LIBRARY OF THE UNIVERSITY OF CALIFORNIA. % Class WORKS OF H. M. WILSON PUBLISHED BY JOHN WILEY & SONS. Topographic Surveying. Including- geographic, exploratory, and military mapping, with hints on camping, emergency surgery, and photography. Third Edition, Revised. Illus- trated by 18 engraved colored plates and 205 half-tone plates and cuts, including two double-page plates. 8vo, xxx -f yio pages. Cloth, $3.50. Irrigation Engineering. PART I. HYDROGRAPHY. PART II. CANALS AND CANAL WORKS. PART III. STORAGE RESERVOIRS. Sixth Edition, Revised and Enlarged. 8vo, xxix + 625 pages; 38 full-page plates and 195 figures, in- cluding many half-tones. $4.00. IRRIGATION ENGINEERING BY HERBERT M. WILSON, C.E. Member American Society of Civil Engineers ; C kief Engineer and former Geografher and Irrigation Engineer , United States Geological Survey ; Author of" Topographic Surveying" etc. SIXTH EDITION, REVISED AND ENLARGED TOTAL ISSUE SEVEN THOUSAND NEW YORK: JOHN WILEY & SONS LONDON: CHAPMAN & HALL, LIMITED 1909 Copyright, 1896, 1903, 1905, 1909 BY HERBERT M. WILSON COMPOSITION AN 7 D ELECTROTYPING BY PUBLISHERS PRINTING CO., NEW YORK, U.S.A. PREFACE TO FIRST EDITION THE need of a comprehensive treatise on irrigation has been so frequently brought to my attention during the last few years, that I have undertaken to write this book with the hope that it may help those who are engaged in the study or practice of irrigation engineer- ing. It is chiefly the result of original investigation, the descrip- tions of works being made from personal observation in America, Europe, and India. Some of the matter contained in Part I is compiled, and in its preparation I am especially indebted for information and sugges- tions to the valuable work on "Water Supply Engineering," by Mr. J. T. Fanning. There is added, however, much that is new, a portion of which was obtained from the reports of Mr. F. H. Newell, Chief Hydrographer of the U. S. Geological Survey. The purpose has been to include in Part I only so much of hydraulics as is an indispensable preliminary to the remainder of the book, or is original matter. Wherever the subject has been treated by others the reader is referred to their works. The entire book relates directly to the conditions surrounding Western irrigation practice. The examples given and the sugges- tions made apply immediately to Western methods, though many useful hints are borrowed from foreign experience. The classifica- tion adopted is original, I believe, and follows closely that employed in reports made by me to the Government, which seem to have met with general approval. In this classification the terms "diver- sion weirs" and "dams" have been used with special signification. iii 190880 iv PREFACE TO FIRST EDITION Under the term "diversion weirs" are included all obstructions built across running streams and designed to act as overflow weirs, though their functions may be those either of storage dams or diversion weirs or both. Under the term "dams" are included all retaining walls, of whatsoever material, which are intended only to impound water and are not so constructed as to withstand the shock of falling water. These classes necessarily overlap to some extent. The subject of the application of water to crops is but briefly touched upon. It would in itself require a volume, and is one of more interest to the farmer than to the engineer. Part III, which treats of storage works, contains much new material never before brought together, and this is especially true of the chapters on Earth Dams and Pumping. The theory of high masonry dams is but briefly considered, as this subject has already been exhaustively treated by previous writers, to whose works reference is made. What little has been said concerning it is partly com- piled, the chief source being Wegmann's admirable treatise on masonry dams. Great care has been taken throughout the volume to avoid the use of mathematics, since many of the for- mulas given on the flow of water in open or closed channels, on the discharge from catchment basins, and on strains in masonry dams are exceedingly faulty and misleading. We have much to learn before we can apply mathematics to these subjects with accuracy. I consider it better to follow practical usage and experience than theory where the latter is founded on doubtful premises and is liable to produce inaccurate results if adhered to closely. The endeavor has been to prepare a work which will be of value to the practical engineer as well as to the student. It was PREFACE TO FIRST EDITION V found impossible to include within the covers of one volume the necessary tables on hydraulics and flow of water. It is believed, however, that this book contains much that will be useful to the practical engineer, and that the teacher of irrigation engineering will find the facts assembled in such manner as to be materially helpful. The effort has been to illustrate all the important works de- scribed, as well as types of works, in order that practising engineers may obtain suggestions from the experience of others. I am indebted to the courtesy of the Director of the U. S. Geological Survey for numerous electrotypes of illustrations, which had been previously published in reports made by me. Several illustrations were also obtained through the courtesy of the Secretary of the American Society of Civil Engineers, being electrotypes of those used in papers read by me before that society. WASHINGTON, D. C., January, 1893. PREFACE TO FOURTH EDITION CONGRESS has recently enacted a reclamation law whereby for the first time in the history of our country provision has been made for the systematic construction, on a large scale, of public works other than those for river and harbor improvement. Pro- vision was made by which about $2,500,000 will annually accrue in the Treasury to the credit of the Secretary of the Interior for the construction of works for the irrigation of the lands of the arid region under the supervision of the Director of the United States Geological Survey. Already a number of important projects have advanced to a point where construction may be begun. The magnitude of the work proposed is evident when it is realized that ten years hence $30,000,000 may have been expended upon this work without further act of legislation. Within a year nearly 200 engineers, young and old, have found employment upon this work. The importance to the profession, therefore, of a knowledge of the underlying principles of irrigation engineering has suggested the necessity for an exhaustive revision of this book. Since the issue of the second edition there have been few import- ant developments in hydraulic engineering, consequently the present revision does not affect any portion of the book radically, though it has been sufficiently thorough to affect every portion more or less. There have been constructed recently a number of great storage-dams both of masonry and of loose rock, and important changes in existing structures have been made. These are noted in Part III, in which the greatest amount of textual change has Mil PREFACE TO FOURTH EDITION been made. Especially interesting in this connection is the great overfall weir at Assuan, Egypt; the rock-fill dams of California, and the development in arched and combined masonry and metal dams in the West. The chapter on sub-surface water sources has been materially improved as a result of the work of Prof. Slichter, of Wisconsin. The chapter on rainfall and run-off of streams has been brought up to date and extended, thus adding to its usefulness. I ahi especially indebted for information to the admirable series of water-supply papers of the U. S. Geological Survey, numbering now eighty, nearly all of which have been published since the last revision. Many useful data have also been obtained from Mr. J. D. Schuyler's report on reservoirs for irrigation, published in the Eighteenth Annual Report of the same bureau; also from Messrs. Turneaure and Russell's " Public Water Sup- plies," and the various technical papers which have appeared from time to time in Engineering News. H. M. W. WASHINGTON, D. C., November, 1903. PREFACE TO SIXTH EDITION THE Reclamation Service of the United States now has 21 projects which have reached such a state of completion that water is being furnished settlers for irrigation of their lands. At this date 675,514 acres are under irrigation from Reclamation projects and $42,932,787 have been expended upon the construction of works completed or in progress. The revenues collected to date from projects in operation and available under the law for re- expenditure on future construction amoupt to $1,070,596. The present edition has been almost entirely rewritten, bringing up to date the tremendous progress made in construction by the Reclamation Service. Since the last edition important changes have been produced in the design and in the materials used in structures on irrigation works as a result of the very general adop- tion of reinforced concrete for such works. Every chapter and every article of this edition has undergone changes, including the elimination of much old matter and forty illustrations and the introduction of a large amount of new textual matter and eighty new illustrations, representative of more modern designs for irrigation works. I am indebted for information contained in this revision chiefly to the annual reports and published specifications of the Reclamation Service. H. M. W. WASHINGTON, D. C., April i, 1909. ix CONTENTS CHAPTER I INTRODUCTION ART. PAGE 1. Meaning of Irrigation i 2. Extent of Irrigation 2 3. Control of Irrigation Works 2 4. Value as an Investment 3 5. Incidental Values 4 6. Cost and Returns of Irrigation 4 PART I HYDROGRAPHY CHAPTER II PRECIPITATION, RUNOFF, AND STREAM FLOW 7. Relation of Rainfall to Irrigation 7 8. General Rainfall Statistics 7 9. Rainfall Distribution in Detail 8 10. Great Rainfalls 9 11. Suddenness of Great Storms 1 1 12. Precipitation on River Basins 1 1 13. Rainfall Statistics by States 1 1 14. Gauging Rainfall 1 1 15. Runoff 14 16. Variability of Runoff 14 17. Relation of Rainfall to Runoff 15 18. Formulas for Maximum Runoff 16 19. Flood Discharges of Streams 17 20. Amounts of Stream Discharge and Runoff 17 21. Discharge in Seasons of Minimum Rainfall 20 xii CONTENTS ART. PAGE 22. Regimen of Western Rivers 20 23. Mean Discharge of Streams 21 24. Available Annual Flow of Streams 21 25. Works of Reference: Precipitation, Runoff, and Stream Flow 21 CHAPTER III EVAPORATION, ABSORPTION, AND SEEPAGE 26. Evaporation Phenomena 23 27. Measurement of Evaporation 23 28. Amount of Evaporation . . . 25 29. Evaporation from Snow and Ice 25 30. Evaporation from Earth ' 27 31. Effect of Evaporation on Water Storage 28 32. Percolation and its Amount 28 33. Absorption 29 34. Amount of Absorption in Reservoirs and Canals 30 35 . Prevention of Perlocation 30 36. Seepage Water 31 37. Amount of Seepage Water 31 38. Works of Reference: Evaporation, Absorption, and Seepage 33 CHAPTER IV ALKALI, DRAINAGE, AND SEDIMENTATION 39. Harmful Effects of Irrigation 34 40. Alkali 34 41. Causes of Alkali 34 42. Waterlogging 35 43. Prevention of Alkali and Waterlogging 35 44. Chemical Treatment 36 45. Mulching and Leaching 38 46. Growth of Suitable Plants 38 47. Drainage 39 48. Excessive Use of Water 39 49- Silt 40 50. Character of Silt 40 51. Amount of Silt. 41 52. Prevention of Sedimentation in Reservoirs and Canals 42 53. Fertilizing Effects of Sediment 44 54. Weeds 44 55. Malarial Effects of Irrigation 44 56. Works of Reference: Alkali, Drainage, and Sedimentation 46 CONTENTS xiii CHAPTER V QUANTITY OF WATER REQUIRED ART. PAGE 57. Duty of Water 47 58. Units of Measure for Water Duty and Flow . 47 59. Measurement of Water Duty 50 60. Duty per Second-foot 51 61. Duty for Various Crops 52 62. Depth of Water Required tc Soak Soil 52 63. Quantity per Service and Irrigating Period 53 64. Duty per Acre-foot 53 65. Linear and Areal Duty 54 66. Percentage of Waste Land 5^ 67. Tatils, or Rotation in Water Distribution 55 68. Works of Reference: Duty of Water 57 CHAPTER VI FLOW AND MEASUREMENT OF WATER IN OPEN CHANNELS. 69. Physical and Chemical Properties of Water 58 70. Weight of Water 58 7 1 . Pressure of Water 58 72. Amount of Pressure of Water 59 73. Center of Pressure 59 74. Atmospheric Pressure 60 75. Motion of Water 60 76. Factors Affecting Flow 61 77. Formulas of Flow in Open Channels 61 78. Kuttcr's Formula 62 79. Tables for Use with Kutler's Formula 64 80. Discharge of Streams and Velocities of Flow 65 81. Surface and Mean Velocities 70 82. Measuring or Gauging Stream Velocities 70 83. Current Meters 72 84. Gauging Stations 74 85. Use of the Current Meter 7^ 86. Rating the Meter 76 87. Rating the Station 76 88. Measuring Weirs 77 89. Rectangular Measuring Weir 77 90. Francis' Formulas 78 91. Conditions of Using Rectangular Weir 79 02. Trapezoidal Weirs 79 xiv CONTENTS ART. PAGE 93. Weir Gauge Heights 80 94. Tables of Weir Discharge 80 95. Broad-crested Weirs 80 96. Measurement of Canal Water 85 97. Requisites of a Measuring Apparatus or Module 85 98. Methods of Measurement 86 99. The Statute Inch or Module 88 100. Rating Flumes 88 101. Divisors 89 102. Stream Measurement Under Ice 89 103. Works of Reference: Flow, etc., of Water in Open Channels 89 CHAPTER VII SUBSURFACE WATER SOURCES AND SEWAGE FOR IRRIGATION 104. Sources of Earth Waters 91 105. Motion of Ground Water 91 106. Underflow 93 107. Sources of Springs and Artesian Wells > 93 108. Artesian Wells 94 109. Examples of Artesian Wells 94 no. Capacity and Cost of Artesian Wells 95 in. Storage of Artesian Water 96 112. Size of Well 96 113. Manner of Having Wells Drilled 97 1 14. Varieties of Drilling-machines 98 1 15. Process of Drilling 100 1 16. Capacity of Common Wells 102 117. Wells, Power-pumped 103 1 18. Tunnelling for Water 105 119. Underground Cribwork 106 1 20. Other Subsurface- water Sources 107 121. Sewage Disposal 107 122. Sewage Irrigation 109 123. Fertilizing Effects of Sewage no 124. Effects of Sewage Irrigation on Health in 125. Duty of Sewage 112 126. Methods of Laying out Sewage Farms and Applying Sewage 114 127. Works of Reference: Subsurface -water Sources and Sewage for Irrigation 117 CONTENTS XV PART II CANALS AND CANAL WORKS CHAPTER VIII CLASSES OF IRRIGATION WORKS ART. PAGE 128. Gravity and Lift Irrigation 1 18 129. Navigation and Irrigation Canals 119 130. Sources of Supply 119 131. Inundation Canals 120 132. Perennial Canals 123 133. Dimensions and Cost of some Perennial Canals 123 134. Parts of a Canal System 125 CHAPTER IX ALIGNMENT, SLOPE, AND CROSS-SECTION 135. Relation between Lands and Water-supply 126 136. Diversion Works 1 26 137. Alignment 127 138. Method of Survey 1 28 139. Linear or Trial-line Survey 1 28 140. Contour Topographic Survey 130 141. Right of Way on Public Land; also State Desert-land Grants 131 142. Obstacles to Alignment 132 143. Sidehill Canal Works 133 144. Curvature 134 145. Borings, Trial Pits, and Permanent Marks 134 146. Example of Canal Alignment Ganges Canal 135 147. Example of Canal Alignment Turlock Canal 138 148. Example of Canal Alignment Santa Ana Canal 143 149. Velocity, Slope, and Cross-section 148 150. Limiting Velocity 149 151. Grade for Given Velocity 149 152. Examples of Canal Velocity and Grades 150 153. Cross-sections 151 154. Form of Cross-section 152 155. Side Slopes and Top Width of Banks 154 156. Cross-section with Subgrade 155 157. Lined Canal 155 158. Shrinkage of Earthwork 159 159. Cross-section in Rock . 160 XVI . CONTENTS CHAPTER X HEADWORKS AND DIVERSION WEIRS ART. PAGE 160. Location of Headworks : 162 161. Character of Headworks 163 162. Diversion Weirs 164 163. Classes of Weirs 16^ 164. Brush and Bowlder Weirs 165 165. Rectangular Pile Weirs 166 166. Open and Closed Weirs 166 167. Open Frame or Flashboard Weirs 168 168. Open Masonry Weirs, Indian Type 1 70 169. Laguna Weir, Colorado River 175 170. Movable Iron Weirs, French Type 176 171. Rolling Lift Weir 177 172. Construction of Crib Weirs 179 1 73. Wooden Crib and Rock Weirs ^ 1 79 174. Scouring Effect of Falling Water 183 175. Weir Aprons 183 176. Rollerway and Ogee-shaped Weirs 185 177. Water-cushions 186 178. Masonry Weirs , 188 179. Masonry Weirs founded on Piles 190 180. Masonry Weir founded on Piles and Cribs 191 181. Masonry Weir founded on Cribs 192 182. Masonry Weirs founded on Wells 192 183. Concrete Weir, Ashlar Facing 194 184. Rubble Masonry Weir 195 185. Iron N Ogee Rollerway Weir 196 186. Masonry and Iron Drop-gate Weir 196 187. Reinforced Concrete Weir ~ 200 188. Reinforced Rubble Masonry Weir 202 189. Other Masonry Weirs 206 190. Diversion Dams 208 191. River Training Works . ." . . 209 CHAPTER XI SLUICEWAYS, REGULATORS, AND ESCAPES 192. Sluiceways 211 193. Examples of Sluiceways 212 194. Yuma Project and Sluiceways, Laguna Weir 214 195. Sluice Gates, Laguna Weir 217 196. Sluice Gates, Granite Reef Weir 219 CONTENTS xvii ARTv PAGE .197. Falling Sluice-gates . 221 198. Bear-trap Movable Sluice-gates 221 199. Mahanuddy Sluice Shutters 223 200. Soane Falling Sluice-gates 224 201. Automatic Wasteway Gate 226 202. Relation of Weirs to Regulators 227 203. Granite Reef Regulator 229 204. Classification of Regulators 230 205. General Form of Regulator 230 206. Arrangement of Canal Head 231 207. Wooden Flashboard Regulators 232 208. Wooden Gate Lifted by Windlass 234 209. Gate Lifted by Travelling Winch 235 210. Gate Raised by Gearing or Screw 235- 211. Inclined, Horizontally Pivoted Falling Gates 236 212. Hydraulic Lifting Gate 239 213. Wasteways 239 214. Location and Characteristics of Waterways 240 215. Design of Escape Heads 242 216. Wasteways, Reclamation Service 244 217. Taintor Circular Wasteway Gates 246 218. Sand-gates 250 CHAPTER XII FALLS AND DRAINAGE WORKS 219. Excessive Slope 255 220. Falls and Rapids 255 221. Retarding Velocity by Flashboards on Fall Crest 256 222. Retarding Velocity by Contracting Channel 257 223. Gratings to Retard Velocity of Approach 257 224. Notched Fall Crest 260 225. Vertical Fall of Wood 263 226. Masonry Falls 264 227. Wooden Rapids or Chutes 264 228. Masonry Rapids 266 229. Drainage Works 266 230. Drainage Cuts 268 231. Inlet Dams 268 232. Level Crossings 270 233. Flumes -. 272 234. Sidehill Flumes 274 235. Construction of Flumes 274 236. Stave and Binder Flumes 275 237. Flume Trestles 276 xviii CONTENTS ART. PAGE 238. Iron Aqueducts 276 239. Masonry Aqueducts 279 240. Reinforced Concrete Flumes and Aqueducts 283 241. Superpassages 284 242. Culverts and Inverted Siphons 289 243. Wooden Culvert 291 244. Inverted Siphons of Masonry 291 245. Reinforced Concrete Culverts 294 246. Reinforced Concrete Siphons 294 CHAPTER XIII DISTRIBUTARIES 247. Object and Types 296 248. Location of Distributaries 296 249. Design of Distributaries 297 250. Efficiency of a Canal 299 251. Dimensions of Laterals 302 252. Capacities of Laterals 302 253. Distributary Channels in Earth 303 254. Wooden Lateral Heads and Turnouts 304 255. Masonry Lateral Heads 310 256. Works of Reference: Diversion and Canal Works 311 CHAPTER XIV APPLICATION OF WATER, AND PIPE IRRIGATION 257. Relation of Water to Plant-growth 313 258. Relation of Soil Texture to Plant-growth 315 259. Theory of Cultivation by Irrigation 319 260. Methods of Applying Water 321 261. Preparation of Ground for Irrigation 322 262. Sidehill Flooding of Meadows . . . v 324 263. Flooding by Checks 325 264. Flooding by Checkerboard System of Squares 326 265. Flooding by Terraces 327 266. Furrow Irrigation of Vegetables and Grain 327 267. Combined Flooding and Furrow Irrigation of Orchards 328 268. Irrigating Orchards by Small Furrows 330 269. Ditch and Furrow Checks 333 270. Subsurface Irrigation 334 271. Subirrigation Pipes 336 272. Main and Distributing Pipes 336 CONTENTS xix ART. PAG * 273. Flow of Water in Pipes 33 8 274. Formulas of Flow in Pipes . . 339 275. Tables of Flow in Pipes with and without Pressure . 340 276. Sheet-iron and Steel Pipes ... - 343~ 277. Wooden-stave Pipes 34 278. Construction of Wooden Pipe Lines ... -347 279. Reinforced Concrete Pipe 349 280. Measurement of Flow in Pipes 35 281. Works of Reference: Application of Water and Pipe Irrigation 352 PART III STORAGE RESERVOIRS CHAPTER XV LOCATION AND CAPACITY OF RESERVOIRS 282. Classes of Storage Works .353 283. Character of Reservoir Site . 353 284. Relation of Reservoir Site to Land and Water Supply 354 285. Topography and Survey of Reservoir Sites . 355 286. Exploring for Rock Foundation -357 287. Geology of Reservoir Sites 359 288. Cost and Dimensions of some Great Storage Reservoirs . . 360 289. Classes of Dams . 360 CHAPTER XVI EARTH AND LOOSE-ROCK DAMS 290. Earth Dams or Embankments 365 291. Causes of Failure of Earth Dams 365 292. Dimensions of Earth Dams 365 293. Foundations 365 294. Foundations of Masonry Core and Puddle Walls 366 295. Springs in Foundations 366 296. Masonry Cores, Puddle Walls, and Homogeneous Embankments 367 297. Masonry Core-walls in Earth Embankments 369 298. Puddle Walls and Faces 370 299. Puddle Trench 371 300. Homogeneous Earth Embankment 372 xx CONTENTS ART. PAGE 301. Embankment Material 376 302. Embankment of Sand 377 303. Hydraulic-fill Dam 377 304. Combined Earth and Hydraulic-fill Dam 378 305. Interior Slope and Paving 380 306. Earth Embankment with Masonry Retaining-wall 382 307. Earth and Loose-rock Dams Pecos Dam 383 308. Minidoka Project and Dam, Idaho 385 309. Loose-rock Dams 387 310. Walnut Grove Dam 389 311. Rock -filled Steel-core Dam 391 312. Crib Dams 392 313. Loose-rock Dams with Masonry Retaining-walls 394 314. Failure and Faulty Design of Earth and Loose-rock Dams 396 CHAPTER XVII MASONRY DAMS 315. Theory of Masonry Dams 399 316. Stability of Gravity Dams 400 317. Stability against Sliding 402 318. Coefficient of Friction in Masonry 403 319. Stability against Crushing 404 320. Limiting Pressures 406 321. Stability against Overturning 406 322. Molesworth's Formula and Profile Type 409 323. Height and Top Width of Dam 410 324. Profile of Dam 410 325. Stability against Upward Water Pressure; also Causes of Failure 411 326. Stability against Temperature Changes 415 327. Curved Masonry Dams 415 328. Design of Curved Dams 418 329. Wide-crested or Overfall Dams 420 330. Design of Overfall Dams 421 331. Foundations 424 332. Preparing Foundations 424 333. Material of which Constructed 426 334. Concrete 428. 335. Rubble Masonry 430 336. Cement 430 337. Details of Construction 431 338. Waterproofing Materials 434 339. Submerged Dams 437 340. Construction in Flowing Streams 438 341. Specifications and Contracts 440 CONTENTS xxi PACK ART. 342. Examples of Masonry Dams 4 343. Furens Dam, France. . 344. Gran Cheurfas Dam, Algiers . 345. Tansa Dam, India . 346. Bhatgur Dam, India . 347. New Croton Dam, New York 447 348. Periar Dam, India. . 349. Beetaloo Dam, South Australia . 350. Remscheid Dam, Germany . 351. San Mateo Dam, California . 352. Sweetwater Dam, California 45 2 353. Vyrnwy Dam, Wales 354. Assuan Dam and Assiout Weir, Egypt -457 355. Betwa Dam, India .... 356. La Grange Dam, California . 357. Folsom Dam, California 358. Austin Dam, Texas 359. Overfall Masonry Dam, Spier Falls, X. Y. . 360. Roosevelt Dam, Arizona 361. Shoshone Dam, Wyoming 362. Bear Valley and Zola Dams . . 363. Upper Otay Dam, California 4/4 364. Buttressed and Arched Masonry Walls. . 365. Steel Dam, Ash Fork, Arizona . . CHAPTER XVIII WASTE WAYS AND OUTLET SLUICES 366. Wasteways 367. Character and Design of Wasteways ... 482 368. Discharge of Waste Weirs . . 4^2 369. Classes of Wasteways .... 4&3 370. Shapes of Waste Weirs. . 371. Examples of Wasteways . 372. Automatic Shutters and Gates 4$8 373. Automatic Drop-shutters . 374. Automatic Weir-gates 375. Stoney's Balanced Sluice-gate ... 493 376. Undersluices 4 95 377. Examples of Undersluices 49 378. Outlet Sluices 49" 379. Gate-towers and Valve-chambers . . 49 8 380. Examples of Gate-towers and Outlet Sluices . 381. Electrically Operated Outlet Gates, Roosevelt Dam 382. Unit Cost of Construction 383. Works of Reference.. .Storage Works xxn CONTENTS CHAPTER XIX PUMPING, TOOLS, AND MAINTENANCE ART. PAGE 384. Pumping or Lift Irrigation 509 385. Motive Power and Pumps 510 386. Choice of Pumping Machines 512 387. Animal Motive Power 514 388. Windmills 515 389. Capacity and Economy of Windmills 516 390. Varieties of Windmills 519 391. Value of Windmills as Irrigating Machines 523 392. Power in Falling Water 524 393. Water-motors 526 394. Undershot Water-wheels 527 395. Overshot Water-wheels 531 396. Turbine Water-wheels 532 397. Pelton Water-wheels 534 398. Uses of Water-power 536 399. Water-pressure Engines 537 400. Hydraulic Rams 539 401. Hot-air, Alcohol, and Gasoline Pumping-engines 541 402. Pumping by Steam-power 543 403. Producer Gas Power 545 404. Energy, Work, and Power 545 405. Centrifugal and Rotary Pumps 546 406. Examples of Centrifugal Pumping Plants 550 407. Steam Pumping-engines 551 408. Examples of Steam Pumping Plants 552 409. Cost of Various Powers and of Pumping 555 410. Pulsometers and Mechanical Elevators 556 411. Irrigation Tools 557 412. Scrapers 557 413. Grading- and Excavating-machines 559 414. Maintenance and Supervision 560 415. Sources of Impairment of Irrigation Works 561 416. Inspection 562 417. Works of Reference. Pumping Machinery 562 CHAPTER XX RECLAMATION SERVICE OF UNITED STATES 418. The Reclamation Law 564 419. Scope of Reclamation Law 567 420. Water Users' Associations 569 421. Specifications, Roosevelt Dam 573 422. Unit Costs, Reclamation Service 584 CONTENTS xxiii TABLES I. Extent and Cost of Irrigation 5 II. Precipitation by River Basins 10 III. Precipitiation by States 12 IV. Stream Discharge and Runoff 18 V. Depth of Evaporation, in inches per Month in 1887-88 26 VI. Depth of Evaporation per Month, in inches 27 VII. Units of Measure 48 VIII. Duty of Water 51 IX. Value of V in feet per Second and of C for Earth Channels by Kutter's Formula 63 X. Grades, Slopes, and Values A i in Kutter's Formula 65 XL Values of A, r, and \/r for Rectanglar Channels 66 XII. " " " " " " Side Slopes of i on i 67 XIII. " " " " " " " " " i on ij 63 XIV. " " C for given Slopes and Hydraulic Mean Radii 69 XV. Discharge over Rectangular Weirs 81 XVI. Discharge over Cippoletti Trapezoidal Weir 83 XVII. Some Great Perennial Canals 1 24 XVIII. Values of K in Flynn's Kutter Formula 342 XIX. Values of \/f for Circular Pipes 342 XX. Factors for use in D'Arcy's Formula of Flow through Clean Pipes 343 XXL Factors for use in D'Arcy's Formula of Flow through Tuberculated Pipes.. . 344 XXII. Values of C\/r in Flynn's Kutter Formula 344 XXIII. Cost and Dimensions of some Storage Reservoirs 361 XXIV. Coefficients of Friction in Masonry 403 XXV. Wegmann's Practical Profile No. 3 413 XXVI. Wind Velocity and Power 516 XXVII. Capacity of Windmills 517 XXVIII. Energy of Wind Acting upon a Surface of 100 Square Feet .... 519 XXIX. Capacities and Efficiencies of Several Windmills 520 XXX. Equivalent Units of Energy 546 XXXI. " " Work 546 - XXXII. " " " Power 547 ILLUSTRATIONS LIST OF PLATES PLATE PAGE I. Plan and Cross-section of Ganges Canal, Hurdwar to Roorkee, India 137 II. Mill Creek Flume and Steel Bridge, Santa Ana Canal 145 III. View on Line of Santa Ana Canal 14; IV. Kern River Diversion Weir. Head of Calloway Canal 169 V. Cross-sections of Indian Weirs 171 VI. View of Old Weir and Scouring Sluices, Head of Arizona Canal. VII. Cross-section of Croton Dam VIII. Iron-faced Rollerway Weir, Cohoes, X. Y 107 IX. Granite Reef Weir, Salt River, During Construction 20^ X. View of Goulburn Weir, Australia 207 XL Falling Sluice-gate, Soane Canal, India 22 > XII. Bear River Canal. Elevation and Cross-section of Weir and Reg- ulator 238 XIII. Cross-section and Elevation of Regulator Gates, Folsom Canal .... 243 XIV. Plan of Rapids, Bari Doab Canal, India 267 XV. Highline Canal, Colorado. View of Bench Flume 273 XVI. View of Solani Aqueduct, Ganges Canal, India 280 XVII. View of Ranipur Superpassage, Ganges Canal, India 287 XVTII. Idaho Irrigation Company's Canal. View of Wooden Siphon on Phyllis Branch 288 XIX. Rawhide Siphon, Interstate Canal. A. Inlet, B. Creek Bed. . . . 293 XX. Standard Masonry Outlet for Distributaries, Punjab, India 307 XXI. Irrigating Orchard by Terraced Basins on Hillside 329 XXII. Earth Dam and Masonry Core-wall during Construction, Carmel, N. Y " 375 XXIII. Lower Otay Rock-filled Dam 393 XXIV. Excavating Foundation for New Croton Dam and Gate-house . . 427 XXV. View of Bhatgur Dam, India 445 XXVI. San Mateo Dam. Plan, Cross-section, and Outlet Sluices 45 1 XXVII. Plan of Sweetwater Dam 453 XXVIII. Cross-section of Sweetwater Dam 454 XXIX. View of Sweetwater Dam 455 XXX. Folsom Canal, View of Weir and Regulator . 461 XXXI. Folsom Canal, Plan and Cross-section of Weir ... . 463 XXXII. Plan of Roosevelt Dam, Salt River Project, Arizona 4^7 xxvi ILLUSTRATIONS PLATE PAGH XXXIII. Maximum Cross-section, Roosevelt Dam, Arizona 469 XXXIV. Upper Otay Masonry Dam 475 XXXV. View of New Croton Dam and Wasteway 485 XXXVI. Reinold's Automatic Waste Gate, India 492 XXXVII. Vertical Lift Outlet Gate, Fay Lake Reservoir, Arizona 501 XXXVIII. Outlet Gates, Roosevelt Dam, Arizona 505 LIST OF ILLUSTRATIONS FIG. 1. Rain Gauge 14 2. Relation of Runoff to Rainfall 15 3. Evaporating-pan 24 4. Price Electric and Acoustic Current Meters 71 5. Haskell Current Meter 72 6. Price Acoustic Current Meter 73 7. Cable Station, Car, Gauge, etc 75 8. Rectangular Measuring Weir 78 9. Foote's Measuring Weir, A. Water Divisor, B 86 10. Australian Water Meter 87 11. Portable Artesian-well Drilling Rig 99 12. Pumping Station and Group of Wells, Garden City, Kan 104 13. Subterranean Water Tunnel and Feed Wells 106 14. Gathering Cribs, Citizen's Water Co., Denver 108 15. Canal Cross-sections for Varying Bed-widths 133 16. Turlock Canal. Plan of Diversion Line 139 17. Turlock Canal. View of Sidehill Work 140 18. Tunnel on Truckee Carson Canal, Nevada 148 19. Various Canal Cross-sections 153 20. Cross-section of Calloway Canal, showing Subgrade 155 21. Typical Section of Lined Canal, Reclamation Service 155 22. Cross-section of Lined Channel, Santa Ana Canal 156 23. Concrete Lining, Truckee -Carson Canal, Nevada 157 24. Reinforced Concrete Canal Lining, Tieton Canal 158 25. Plan and Cross-section of Sheet Steel Irrigation Canal, Upper Egypt. ... 159 26. Rock Cross-section, Turlock Canal 160 27. A. Rock Cross-section, Bear River Canal. B. Umatilla Canal 160 28. Transition from Rock to Earth Cross-section 161 29. Cross-section of Open Weir, Calloway Canal 170 30. Half -elevation and Plan, and Section of Soane Weir, India 173 31. Elevation and Cross-section of Sidhnai Weir, India 174 32. Cross-section of Laguna Weir, Colorado River 176 33. View of Open Weir on River Seine, France 177 34. Rolling Lift Weir, Schweinfurt, Bavaria 178 35. Cross-section of Old Arizona Weir 180 36. Cross-section of Bear River Weir 182 37. Cross-section of Old Holyoke Weir 183 ILLUSTRATIONS xxvii FIG. PAGB 38. Cross-section of Lower Yellowstone Weir, Mont 184 39. Diagram of Ogee Curve ^5 40. Cross-sections of Eight Ogee -shaped Weirs 186 41. Leasburg Diversion Weir, Rio Grande Project, N. M 190 42. Cross-section of Norwich Water Power Company's Weir 191 43. Cross-section of Henares Weir, Spain 194 44. Cross-section of Iron Weir, Cohoes, N. Y 195 45. Down-stream Elevation, Goulburn Weir, Australia 198 46. Section of Goulburn Weir, Australia 199 47. Cross-section of Reinforced Concrete Weir, Theresa, N. Y 200 48. Cross-section of Corbett Dam, Shoshone Project, Wyo 201 49. Plan and Section of Corbett Dam and Headworks 202 50. Plan of Granite Reefs Weir and Headworks 203 51. Cross-section of Granite Reefs Weir, Arizona 204 52. Granite Reefs Weir and Apron on Bowlder Foundation 206 53. Cross-sections of Newark Dam and Weir 208 54. Cross-section of New Holyoke Weir, Mass 209 55. Plan of Headworks, Laguna Weir, Colorado River 213 56. Plan of Headworks, Granite Reef Weir, Salt River, Arizona 215 57. Sluice Gate with Operating Machinery, Laguna Weir 216 58. Half Plan, Sluice Gate, Laguna Weir 217 59. Operating Mechanism, Sluice Gates, Granite Reefs Weir 219 60. Rear of Sluice Gate, Granite Reefs Weir 220 61. Chanoine Movable Shutters, Raised, Lowered, and Closed 222 62. Bear-trap Gate. Parker Modification 223 63. Cross-section of Mahanuddy Automatic Shutters, India 224 64. Automatic Wasteway Gate, Belle Fourche 227 65. Plan of Headworks, Ganges Canal, India 228 66. Plan of Old Headworks, Arizona Canal 229 67. Regulator Gates, Laguna Weir, Colorado River 233 68. Regulator Gates, Ganges Canal 234 69. Regulator Gates, Soane Canal, India 234 70. Wooden Lever and Screw Regulator Gates 235 71. Regulator Gate, Leasburg Canal, Rio Grande 236 72. Wooden Gate, Leasburg Canal Regulator 237 73. Regulator Gate, Minidoka Canal, Idaho 237 74. Inclined, Falling Regulator Gates, Goulburn Canal, Australia 241 75. Escape-flume on Goulburn Canal, Australia 244 76. Spillway, Fort Shaw Canal, Montana 245 77. Standard Sluiceway, Lower Yellowstone Canal 245 78. Pine Ridge Sluiceway, Interstate Canal 246 79. By-pass Feeder Weir, Umatilla Canal 247 50. Wasteway and Taintor Gates, Lower Truckee Canal 249 51. Cross-section of Sand Box, Santa Ana Canal 250 2. Standard Sluice Gates, Lower Yellowstone Canal 251 83. Cast-iron Sluice Gate, Interstate Canal, Neb.-Wyo 252 4. Sand-gate, Leasburg Canal, Rio Grande 253 xxviii ILLUSTRATIONS FIG. PAGE 85. Section of lo-foot Fall with Grating and Water Cushion 258 86. Typical Fall with Grating, Uncompahgre Canal 259 87. Notched Fall, Interstate Canal, Neb.-Wyo 260 88. Notched Fall, Chenab Canal, India 261 89. Cross-section of Fall, Bear River Canal 262 90. Timber Drop, Lower Yellowstone Lateral 263 91. Concrete Fall with Water Cushion 264 92. Kushuk Fall, Agra Canal, India 265 93. Plan and Elevation of Big Drop, Grand River Canal 265 94. Reinforced Concrete Rapid, Okanogan, Wash 269 95. Pipe Inlet, Reno Coulee, Lower Yellowstone Canal 269 96. Plan of Rutmoo Crossing, Ganges Canal, India . . 271 97. Cross-section of San Diego Flume 275 98. Cross-section, Stave and Binder Flume, Santa Ana Canal 276 99. Standard Timber Flume and Trestle, Reclamation Service 277 100. Elevation and Cross-section of Iron Flume, Bear River Canal 278 joi. Aqueduct, Henares Canal, Spain 279 102. Nadrai Aqueduct, Lower Ganges Canal, India 281 103. Standard Reinforced Concrete Flume and Trestle, Reclamation Service 282 104. Circular Reinforced Concrete Flume and Trestle 283 105. Longitudinal Section, Reinforced Concrete Aqueduct, Interstate Canal. . 284 106. Section through Reinforced Concrete Aqueduct, Interstate Canal 285 107. Reinforced Concrete Aqueduct Spring Canyon, Interstate Canal 286 108. Section of Wooden Culvert, Del Norte Canal, Colorado 289 109. Soane Canal. Cross-section of Kao Nulla Siphon-aqueduct 290 no. Section of Sesia Siphon, Cavour Canal, Italy 290 in. Reinforced Concrete Culvert, Lower Yellowstone Canal 291 112. Reinforced Concrete Twin Siphon, Yellowstone Canal ..... . . 292 113. Reinforced Concrete Twin Siphon, Interstate Canal 294 114. Diagram Illustrating Distributary System 297 115. Distributary System, Huntley Canal, Mont 298 116. View of Distributary Head, Calloway Canal 304 117. Wooden Turnout, Sun River Canal, Mont 305 1 18. Reinforced Concrete Turnouts for Laterals 306 119. Reinforced Concrete Turnouts for Laterals with Drop 308 120. Cast Iron Gates for Laterals, Interstate Canal , 309 121. Wooden Gates for Laterals, Interstate Canal 310 122. Diagram Illustrating Flooding of Meadows 324 123. Irrigation by System of Check-levees 325 124. Flooding by System of Squares 326 125. Furrow Irrigation of Grain 328 126. Furrow Irrigation of Orchards 330 127. Extent of Percolation from Small Furrows ...... ... 332 128. Using Canvas Dam 333 129. Steel Dams 334 130. Flow of Water in Pressure Pipe 338 131. Traveling Forms for Moulding Concrete Pipe ......... 349 ILLUSTRATIONS xxix FIG. PAGE 132. Venturi Meter and Recording Device 35 1 133. Diagrams Illustrating Geology of Reservoir Site 360 134. Cold Springs Dam, Umatilla Project, Ore 369 135. Cross-section of Titicus Earth Dam, N. Y 370 136. Core-wall and Earth Embankment, Boston Water- works 370 137. Earth Dam with Puddle Face, Monument Creek, Col 371 138. Ashti Dam, India, Cross-section 373 139. Cross-section of Earth Dam, Santa Fe, showing Masonry Cross-Trenches 373 140. San Leandro Earth and Hydraulic-fill Dam 379 141. Section and Paving, Belle Fourche Dam, S. D 381 142. Cross-sections of Kabra Dam (A) and Ekruk Dam (B), India 382 143. Cross-section of Pecos Dam 384 144. Avalon Dam, Carlsbad Project, X. M 384 145. Dam, Regulator, and Headworks, Minidoka Project, Idaho 385 146. Cross-section, Rock-fill Dam, Minidoka Project, Idaho 386 147. Cross-section, Concrete Waste Weir, Minidoka Project, Idaho 387 148. Elevation and Cross-section of Walnut Grove Dam 390 149. Rock-filled Steel-core Dam, Lower Otay, Cal 391 150. Plan and Cross-section of Bowman Dam 395 151. Elevation, Plan, and Cross-section of Castlewood Dam 396 152. Theoretical Triangular Cross-section of Dam 402 153. Diagram illustrating Wegmann's Formula 407 154. Molesworth's Profile Type 411 155. Comparison of Profile Types 412 156. Practical Profile from Wegmann 417 157. Flow over Wide-crested Dam 423 158. Steel Forms, McCall's Ferry Dam, Penn 429 159. View of San Fernando Submerged Dam 438 160. Cross-section of Furens Dam, France 441 161. Cross-section of Gran Cheurfas Dam, Algiers 442 162. Cross-section of Tansa Dam, India 443 163. Cross-section of Bhatgur Dam, India 446 164. Cross-section of Masonry Dam, New Croton Dam, Cornell's 447 165. Cross-section of Overfall Weir, New Croton Dam, Cornell's 448 166. Cross-sections of Periar Dam, India 449 167. Cross-section of Beetaloo Dam, Australia 450 168. Cross-section of Vyrnwy Dam, Wales 456 169. Cross-sections of Assuan Dam, Egypt 458 170. Cross-section of Betwa Dam, India 459 171. Cross-section of La Grange Dam 460 172. Cross-section of Austin Dam 464 173. Spier Falls Dam, N. Y 465 174. Overfall Section, Spier Falls W r eir, N. Y 466 175. Cross-section of Shoshone Dam, Wyo 471 176. Cross-section of Bear Valley Dam, Cal 472 177. Plan and Elevation of Bear Valley Dam, Cal 472 178. Sections of Arched Masonry Dams 473 xxx ILLUSTRATIONS FIG. PAGE 179. Meer Allum Dam, India : 476 180. East Park Dam and Spillway, Orland Project, Cal 477 181. Steel Dam, Ash Fork, Arizona 479 182. Plan of Santa Fe Reservoir, Wasteway and Waste-weir 487 183. Cross-section of Shutter on Soane Weir, India 488 184. Automatic Drop-shutter, Betwa Weir, India 489 185. Attachment of Tension-rod to Drop-shutter 490 186. Stoney's Balanced Sluice-gate, Periyar Dam, India 494 187. Outlet Pipes in Earth Dam 498 1 88. Valve-plugs, Sweetwater and Hemet Dams 499 189. Valve-chambers, Wachusett Dam, Boston 502 190. Gate House, Conconully Dam, Wash 503 191. Diagram for Determining Horse-power of Water-wheels and Water-falls 525 192. Undershot Water-wheel or Noria ... 529 193. Floating Pumping Station, Williston, N. D 554 194. Buck Scraper 558 195. New Era Excavator 559 IRRIGATION ENGINEERING CHAPTER I INTRODUCTION i. Meaning of Irrigation. The word irrigation implies a condition far more imposing than is intended. In dry weather a watering-pot is used to sprinkle such plants and flowers as are considered most valuable, or perhaps a hose or water-barrel is used to moisten more or less of the garden truck. This is irrigation pure and simple. The only difference between this form and that more generally implied by the word irrigation as used in arid lands is that in the latter the application of water to crops becomes a business, and the farmer and the engineer unite in the employ- ment of methods whereby water may be applied in the easiest, least expensive, and most certain manner. This is by the action of gravity, and irrigation by natural flow is the result. Ditches are constructed which lead the water from the source of supply, be it well, reservoir, or stream; and they are so aligned and graded that the water shall flow through these and from them into minor channels, and from these again be led by ploughed or drilled furrows through the fields. The mistake is too commonly made of regarding the work of irrigation as a hardship, and the necessity for it as a misfortune. In point of fact, the necessity for irrigation and the ability to irrigate make a fortunate combination. They imply a warm, dry climate, as that of the arid regions ; and this means that the crops are not liable to destruction by sudden, violent storms or by the lack of sufficient sunshine or by the failure of water-supply, as sometimes results from dependence upon rainfall alone. All of this fortunate combination is not found in the semi-humid region, where the rainfall is generally sufficient for the maturing 2 INTRODUCTION of crops. As a result there is not the ever-present sunshine and immunity from damaging storms, yet here irrigation may fulfil one of its most important functions that of helping Nature through the drought periods, or, in other words, that of an insurance on the crops. 2. Extent of Irrigation. The extent to which irrigation can be practised is enormous. The total area irrigated in India is about 40,000,000 acres, in Egypt about 6,000,000 acres, and in Italy about 4,700,000 acres. In Spain there are 2,800,000 acres, in France 400,000 acres, and in the United States nearly 10,000,000 acres of irrigated land. This means that in these countries alone crops are grown on 63,900,000 acres of land which but for irrigation would be barren and unproductive. In addition there are some millions more of acres cultivated by the aid of irrigation in China, Japan, Australia, Algeria, South America, and elsewhere. The works which provide water for the irrigation of the 63,900,000 acres above specified represent an investment of about $700,000,000, and the area thus rendered culturable yields annually products valued at about $725,000,000. This represents an interest on the original investment which seems absurd, but in fact it means only that the yield of irrigated crops averages about $11.30 per acre controlled. There are invested in irrigation works in the United States $100,000,000, and in India $390,000,000. 3. Control of Irrigation Works. The development of irri- gation has resulted in many legal complications, while a diversity of social and physical conditions has given rise to a variety of methods for its control. Practically all the works in India are under the direct control of the government, which employs its engineers and legal staff, owns the land and the water, constructs the works, and collects the rentals for the use of water and land. In the Piedmont valley of Italy the land is the property of in- dividuals, and in some cases individuals are owners of the irrigation works. In the case of the Cavour canal, however, the government owns and operates the works, and the water is sold to the cultivators, In the United States the greater portion of the irrigation works are the property of individuals, corporations, or communities, who construct and maintain them and collect the rentals for the VALUE AS AN INVESTMENT 3 use of water. In some cases the same individual owns both land and water; but usually farmers and irrigators have no property interest in the irrigation works. These are owned and operated by independent organizations who collect a revenue from the sale or rental of water. A few properties are State-built or owned by the States. The United States government has recently embarked upon the policy of constructing and operating irrigation works under the direction of the Secretary of the Interior, through the medium of the Reclamation Service. In the first five years of its exist- ence this organization has expended nearly $43,000,000 on great irrigation works which will reclaim several million acres of land. 4. Value as an Investment. As an investment irrigation works are not always successful. There should be a ready market for the products of irrigation, and the interest charges on land and water must not be so great as materially to reduce the profits from crops. The value of irrigation as an investment is especially dependent on the humidity of the climate. In a semi-humid region, where during occasional seasons the nunfall is sufficient to mature the crops, there is but an intermittent demand for water for irrigation, and consequent irregular return derived from its sale. In an arid region, where crops cannot be raised without the aid of irrigation, the demand for water is constant. In the northern provinces of India water is in constant demand for irrigation, and it returns excellent profits. In Bombay and other places where the demand for water is intermittent, because the rainfall is frequently sufficient to mature crops, irrigation works are designated as " protective" (against famine), and the revenue derived from them is insufficient to pay interest and working charges. Perhaps the most important factor bearing on this subject in our arid regions is the degree of habitation. Nearly anywhere that a good market can be found and irrigation is essential to the production of crops, fair interest can be obtained on money invested in irrigation works. Many failures, however, have occurred, due chiefly to the lack of population, and consequent lack of demand for water. Where all the water furnished is utilized economically designed works al- most invariably pay fair returns on the investment. 4 INTRODUCTION 5. Incidental Values. Not only is the direct money return from an irrigation investment to be considered, but there are several incidental means whereby profit may be derived from such investments. On broad principles of general government and policy the construction of irrigation works is of benefit to the whole country. They furnish homes and agricultural pursuits for many who must otherwise be idle or find less substantial support in other ways. Irrigation adds to the general wealth of the country by increasing the amount of its agricultural products. It furnishes excellent investment for capital where the projects are well designed. It results in the conversion of barren and desert lands into delightful homes, and aids in the general development of the other resources of the region in which it is practised, as mining, lumbering, grazing, etc. One of the great advantages of irrigation is that it becomes practically an insurance on the production of crops. Its practice may not be necessary in the semi-humid or humid regions, but even there occasional droughts occur and crops are lost. Where an irrigation system exists in such cases, it will probably be called into requisition once or twice in the course of the year, and may save vast sums which would otherwise be lost by the destruction of crops. 6. Cost and Returns of Irrigation. The returns of irriga- tion vary greatly with the soil, climate, degree of aridity, and the nature and value of the crops which can be grown. Thus in the semi-humid and humid regions irrigation may serve only as an insurance on the crops by providing against possible deficiencies in rainfall. In Utah and neighboring States where only grain, hay, potatoes, and kindred crops can be grown, and water is not economically handled, the returns from irrigation are far less than in southern California and Arizona, where valuable citrus fruits can be cultivated. From a number of experimental crops grown and marketed the following values were derived for each acre-foot of water used in irrigating them. In Montana, $18.42; Utah, $6.34; Wyoming, $7.69; Arizona, $3.37 to $30; California, $10 to $237. The table on p. 5, compiled from the reports of the U. S. Census of 1900, gives an excellent idea of the extent and cost of INCIDENTAL VALUES irrigation, and of the value of the land and water after irrigation has been provided. While the average first cost of water, that is, the cost of constructing canals to bring the water to the land, was $7.80 per acre, the average value of water per acre as estimated by TABLE I. EXTENT AND COST OF IRRIGATION. States. Acreage in Crops. Average size of Irrigated Farms, in Acres. ' Average Value of Irrigated Land per Acre. Average Value of Products from Irrigated Land per Acre per Annum. Average First Cost of Water per Acre. 2 11. & fcpfc >0o. < Arizona 177,271 62 $4? co $16 40 $o ?o $0 82 California ^O/'*^^ 1,026,832 c6 80 io } 07 IO 7O 60 Colorado 1,300,840 01 4O 77 1 1 40 721 2.4 Idaho ^07,067 67 71 2? io 67 9r i 24 Montana J /'V V O ?(;?,86q TI8 io 66 4 O2 28 Nevada 327.22!; 26? 28 47 8 82 2 86 18 New Mexico < *'*'x 3 182,804 3 26 *-4/ 2O 26 i ? 01 6 co 82 Oregon '. 280 041 84 21 6? IO 1 7. 4 76 22 Utah 577.C88 JC 37 4C 17 88 91 7 24 Washington IOQ 52? TO ol ! 48 8? 2 1 C.6 1 2 ?6 ^4 Wyoming 700.482 T63 16 io 727 6 . v.-- (3) No such formulas can be strictly applied with the same co- efficient to areas of varying size, and all must be used with dis- FLOOD DISCHARGES OF STREAMS 17 cretion, as their results are greatly influenced by different con- ditions from those under which they were obtained. In regions where maximum recorded rainfalls of from 3 to 6 inches in 24 hours have occurred the following values of C have been deter- mined for Dickens's formula: Rainfall 3.5 to 4 inches in flat country, C = 2oo; mixed country, C = 2$o; hilly country, C = 3Oo; and for a maximum rainfall of 6 inches, C varies between 300 and 350. For Ryves' formula the coefficient varies between 400 and 500 in flat country, and for hilly areas where the maximum rainfall is high it may reach 650. The shape of the catchment basin is an important factor in the formula of maximum discharge. 19. Flood Discharges of Streams. It is desirable to know the monthly and daily rates of runoff as well as the mean annual runoff of a catchment basin, in order that dams and weirs may be designed with ample wasteways. The greatest floods occur either on barren catchment basins having steep slopes or where heavy snowfalls are followed by warm, melting rains. On the Gila and Salt river basins in Arizona the percentages of runoff .are exceptionally high during occasional severe storms. The highest recorded flood on the Salt River above Phoenix occurred in February, 1891, and amounted to about 300,000 second-feet from a catchment basin of 12,260 square miles. This is equiva- lent to nearly 30 second-feet per square mile of catchment area, while the stream a few days prior to the occurrence of the storm was not discharging over 1000 second-feet, or one-twelfth of a second-foot per square mile. Sudden great storms (Article n) may in the West cause maximum flood discharges as great as 300 second-feet per square mile of catchment area for short periods of time. Observations by Mr. Desmond Fitzgerald at the Boston Water Works indicate that the greatest freshets observed there caused a discharge during 24 hours at the rate of 150 second-feet per square mile. Wasteways for dams should be designed accordingly. 20. Amounts of Stream Discharge and Runoff. Table IV, derived from observations extending over a series of years to 1900, shows the discharge and amounts of runoff from the 18 PRECIPITATION, RUNOFF, AND STREAM-FLOW ^g^^a ^ NO \O OOO^t-. 5 r? ^ COM.. o 1 w - O t^ vO S J2 " *? . *? S lj *V t 1 ^ O O ^ O O O O ^-O cT ^ w vo M cT v^r o HARGE. l] j^o t^-McsroM M |QN CO Q i| OO O OOQioOOO -^-Oc^oi O o ^o ** ^ a O O O O O c^ w LO O O O *o O O w a i M -*< s Ow Q C^Q\XOO*M rfiocsio ^f ^ o V O c^ M c^ LO DISCH^ O *f M M d d w ? 8 00 HI O HI W 10 d o H! d d ) 10 00 d d O\ O *0 CO O O to W ON . \o xo O M 000 IN to 00 ON ^ o o t^ \O IO N 8 v> 8 : to O O o o ** M t^ O O O O 10 00 HI HI U-) . . . . . . . Ov to to 10 d d 8 o o : * CO O HI o 10 : : : : : : O 10 o M O IO *t 10 Q O 2 1 M X g O N * o o W) 8 r vO vO O*> o o 10 O O O o ^ \0 '/. 8 i/-. to J to O t>> >o 6 M to o w oo" oo" -t M 8 & O 10 1 ! O to O O to to to o Q ^ to -I- co O oo O O ^ t"* vo tO 10 M t"* 10 O O 00 M v: n !/, V) t^ O N N CO O W vO to to HI HI O t^ O r^. vo to O Cv t 8 00 "fr f. 8 /-. M < 10 to t^. to 00 to 8 X. ^ 1 G_ to O O O to IO to C MO to oo" >o \r. \r. ^f S : : CO - 10 ; I/I ^r ~ -t ? "* HI to ? t- -t -I "d V C W l|| >g Salesville. . Red Bluff. _t i i Rodenbah. Battle Mt. 1 gj 1 ^3 El Paso. Collision. d E b i 0k d ll| i i 5 bo J2 J! |o as. III : : : : 1 j 2 c : I Yellowstone . . . 1 a i w Humboldt Rio Grande... Owyhee Umatilla i Shoshone Laramie North Platte . . O : & 1 1 j |ti It & o o > HH I- 9' - b V fc ~ 5 H D ....... 1- 1" 2O PRECIPITATION, RUNOFF, AND STREAM- FLOW catchment basins of the more important streams of the arid region. A study of this table will show that the average daily amount of water which may be furnished by a catchment basin for storage varies between o.i and 3.5 acre-feet per square mile of catchment area. These figures correspond rather closely with those obtained at the Boston Water Works and at San Francisco for approxi- mately corresponding amounts of rainfall. The runoff may be well expressed in percentages of the depth of precipitation. Thus in the drainage basin of the Potomac River the average annual precipitation is 45.47 inches, and the average runoff 24.03 inches in depth, which may be expressed as 52.7 per cent of the precipitation. In years of minimum pre- cipitation the per cent of runoff on this basin is 39.2; from May to December it averages 73.7, and from June to November 33 per cent. Similar percentages obtain in the other eastern catchment basjns. In arid regions and in dry seasons the per- centage of runoff is much smaller for similar slopes, topography, and soil cover than in humid regions or in wet seasons. 21. Discharge in Seasons of Minimum Rainfall. Where the number of storage basins is limited it becomes desirable to save all the water possible and frequently to impound enough to carry over a period of two or three years of minimum rainfall. In general it has been found that cycles of mean low rainfall occur every two or three years when the amount of precipitation is less than 0.8 of the mean. The least of these three-year low cycles has been found to average as low as 0.7 of the mean annual rain fall. 22. Regimen of Western Rivers. Eastern rivers usually drain comparatively level catchment basins, well covered with timber and grass. Hence the soil is deep and the rate of runoff con- sequently low and the streams comparatively constant in their discharge, being subject to few and not excessive flood rises. This because the larger portion of the water reaches these streams by seepage. In the arid West the regimen of the streams is the reverse of this. The catchment basins are precipitous and barren. Little water soaks into the soil to supply the streams from springs. MEAN DISCHARGE OF STREAMS 21 After a heavy storm most of the water runs off in a very short period of time, resulting in great floods. Thus streams which at flood height may reach from 10,000 to 15,000 second-feet discharge for a few hours or days may sink within a week or so to paltry rills of a few second-feet discharge or may entirely dis- appear. With such streams it becomes necessary to design works in such manner that most of the discharge may be saved by stor- age within a short period of time. 23. Mean Discharge of Streams. When definite data of the annual discharge of a stream are not available they may be obtained approximately by multiplying the depth of runoff in inches by the area in square miles of its catchment basin. As shown in Article 17, the proportion of rainfall which runs off varies between 30 and 80 per cent, according as the slopes are flat or steep, wooded or barren. The mean discharge ranges between 0.5 and 2.0 second-feet per square mile of catchment area. 24. Available Annual Flow of Streams. Where irrigation is practised all of the water flowing in the streams is not available for storage, since much of it is already appropriated by irrigators, and this quantity must be deducted from that available for storage. A large portion of the discharge occurs in winter when the streams are covered with ice which renders it practically impossible to divert the water for storage, though it is available for such reservoirs as may be on the main streams. As nearly all of the flow occurring in the irrigating season is appropriated, only the surplus and flood water is available for storage. 25. Works of Reference. Precipitation, Runoff, and Stream- flow. CRAIG, JAMES. Discharge from Catchment Areas. Trans. Inst. C. E., vol. 80. London, 1884. FANNING, J. T. A Treatise on Hydraulic and Water-supply Engineering. D. Van Nostrand Co., New York, 1890. FITZGERALD, DESMOND. Maximum Rates of Rainfall. Trans. Am. Soc. C. E., vol. 21. New York, 1889. - Rainfall, Flow of Streams, and Storage. Trans. Am. Soc. C. E., vol 27. New York, 1892. GREELY, Gen. A. W., and GLASSFORD, Lieut. W. A. Irrigation and Water Stor- age in Arid Regions. 5ist Congress, House of Representatives Executive Doc. No. 287. Government Printing Office, Washington. D. C. ; 1801. 22 PRECIPITATION, RUNOFF, AND STREAM-FLOW GREELY, Gen. A. W. Report of Rainfall. 5oth Congress, Senate Executive Doc. No. 91. Government Printing Office, Washington, D. C., 1888. NEWELL, F. H. Parts II of nth to i4th Annual Reports, U. S. Geological Sur- vey. Government Printing Office, Washington, D. C., 1890 to 1893. Hydrography. Bulletin 131, U. S. Geological Survey. Government Printing Office, Washington, D. C., 1895. Agriculture by Irrigation. Report of Eleventh Census, 1890. Govern- ment Printing Office, Washington, D. C., 1894. UNITED STATES, Census of Agriculture. Eleventh Census, 1890, and Twelfth Census, 1900. Government Printing Office, Washington, D. C. Geological Survey, Numerous Annual Reports and Water-supply Papers since 1890. Government Printing Office, Washington, D. C. Reclamation Service, Annual Reports since 1902. Government Printing Office, Washington, D. C. CHAPTER III EVAPORATION, ABSORPTION, AND SEEPAGE 26. Evaporation Phenomena. The rapidity with which water, snow, and ice are converted into vapor is dependent upon the relative temperatures of the water and atmosphere and upon the amount of motion in the latter. Evaporation is greatest when the atmosphere is dryest, when the water is warm and a brisk wind is blowing. It is least when the atmosphere is moist, the air quiet, and the temperature of the water low. In summer the cool surfaces of deep waters condense moisture from the warm air passing across them and thus gain in moisture when they are supposed to be evaporating. When the reverse conditions exist in the atmosphere and the winds are blowing briskly across the water the resultant wave- motion increases the agitation of the body and permits its vapors to escape freely into the large volumes of unsaturated air which are rapidly pre- sented in succession to attract its vapors. Evaporation is con- stantly taking place at a rate due to the temperature of the surface, and condensation is likewise going on from the vapors existing in the atmosphere, the difference between the two being the rate of evaporation. From the above it will be seen that evaporation should be greatest in amount in the desert regions of the Southwest and least in the high mountains. Tables V and VI show this to be the case, and that in the same latitude evaporation differs greatly in amount according to the altitude. 27. Measurement of Evaporation. Two or three methods have been devised for measuring evaporation, none of which are wholly satisfactory. Elaborate and expensive apparatus has been employed in evaporation measurements made by Mr. Des- mond Fitzgerald, chief engineer of the Boston Water Works; by Mr. Charles Greaves of England, and others. A simple 23 24 EVAPORATION, ABSORPTION, AND SEEPAGE apparatus and one quite as successful as the more elaborate contrivances is that employed by the U. S. Geological Survey. It consists of a pan, Fig. 3, so placed that the contained water has as nearly as possible the same temperature and exposure as that of the body of water the evaporation from which is to be FIG. 3. Evaporating-pan. measured. This evaporating-pan is of galvanized iron 3 feet square and 18 inches deep, and is immersed in water and kept from sinking by means of floats of wood or hollow metal. It should be placed in the water in such position as to be exposed as nearly as possible to its average wind movements. The pan must be rilled to within 3 or 4 inches of the top that the waves produced by the wind shall not cause the water to slop over, and it should float with its rim several inches above the surrounding AMOUNT OF EVAPORATION 25 surface, so that waves from this shall not enter the pan. The device for measuring the evaporation consists of a small brass scale hung in the centre of the pan. The graduations are on a series of inclined crossbars so proportioned that the vertical heights are greatly exaggerated, thus permitting a small rise or fall, say of a tenth of an inch, to cause the water surface to ad- vance or retreat on the scale .3 of an inch. By this device, multi- plying the vertical scale by three, it is possible to read to .01 of an inch. In 1888 a series of observations were made with the Piche evaporometer by Mr. T. Russell of the U. S. Signal Sen-ice to ascertain the amount of evaporation in the West. While it is probable that results obtained with this instrument are not par- ticularly accurate, comparisons of these results with those ob- tained by other methods in similar localities show such slight discrepancies that they may be considered of value until super- seded by results obtained by better methods. Observations were made with this instrument in wind velocities varying from 10 to 30 miles per hour, from which it was discovered that with a velocity of 5 miles an hour the evaporation was 2.2 times that from one in quiet air; 10 miles per hour, 3.8 times; 15 miles, 4.9 times; 20 miles, 5.7 times; 25 miles, 6.1; and 30 miles, 6.3 times. 28. Amount of Evaporation. In Table V is given the amount of evaporation by months in the year 1888 in various sections of the West as derived from experiments with the Piche apparatus. As in the case of precipitation, evaporation decreases with the altitude because of the diminished temperature in high moun- tains. Experiments were made to determine the amount of evaporation in different portions of the West by the hydrog- raphers of the U. S. Geological Survey. These were made with the evaporating-pan, and the results are probably (see Table VI), more reliable than those obtained with the Piche instrument. These experiments were unfortunately conducted for a relatively short space of time. 29. Evaporation from Snow and Ice. From some experi- ments conducted at the Boston Water Works the amount of 26 EVAPORATION, ABSORPTION, AND SEEPAGE evaporation frcm snow and ice was found to be greater than is generally believed. From snow it amounted to about .02 of an inch per day, or nearly 2 J inches in an ordinary season. From TABLE V. DEPTH OF EVAPORATION, IN INCHES PER MONTH IN 1887-88. Stations and Districts. oo 00 .00 00 00 .00 ad .00 oo oo .00 oo' 00 oo .00 4) 1 s : .S :* .8 .6 .1 .1 .4 3 .8 . o .8 . i 3 .4 3 .6 .8 5-4 3-9 4.0 3-0 2.6 5-2 1.4 4-4 3-0 .8 9 .8 .8 .6 .6 7 . i . 2 3 . 2 .2 .0 .8 .8 3 9 1 1.2 1.5 1.4 1:1 11 3.3 3-7 1:1 2.4 1.9 rt .2 3 .1 . i .8 .0 .8 : -5 '.8 3-2 a 3-1 5-4 2.7 8.2 5-4 6.7 7-6 2.1 rt 4.1 6.8 3-2 4-3 4-9 5-2 3-9 5-6 5-8 1.8 C i > 3 H- ) 6.8 9-6 6.8 7-2 6.0 8.0 6.0 6.7 8-3 3-0 3 1:1 4.6 7-7 4.8 1:1 7.2 8.5 4-0 CO 1 o 2.5 2-9 2 .0 3-o 1-7 6.1 2-3 4-2 4-2 2.8 3-4 4-2 1 .1 5 .1 .1 .7 5 . i 9 .1 .0 .8 .1 . 2 .0 7 9 .8 9 .7 .6 .6 .2 .6 .8 3 .8 3 .0 .7 .8 4 -4 9 . i 4 .6 3-6 2.4 2.2 3-0 3-7 NORTHERN SLOPE: Fort Assiniboine Fort Custer Fort Maginnis 4.2 4.9 4.6 5-5 5-7 10.4 6.9 4-3 10.5 1.9 4.8 6.1 3-8 6.4 4-4 8.6 3.7 6.8 6.1 3-0 3-5 1:1 4-3 2~.S 4.6 4-9 2-3 39-5 52.0 35-8 53-4 35-4 76.5 41-3 59-4 69 .0 26.8 47-2 54-6 55-4 46.1 54-4 96.4 76.0 82.0 79-8 65-5 101 .2 56.0 95-7 100.6 48.9 83.9 74-4 68.3 56.1 6 3 .9 42.8 57-7 21. I 26.8 18.1 39-2 84.8 54-3 65-8 37.2 37-5 Helena Poplar River Cheyenne North Platte MIDDLE SLOPE: Colorado Springs Pike's Peak Dodge City Fort Elliott SOUTHERN SLOPE: Fort Sill 4-1 5-1 5-4 7-4 8.2 6^2 5-5 5-4 5-2 4-7 5-7 3-9 3-9 3-4 3-0 4.8 2.8 1:1 .8 .8 .7 7 5 5 .7 9 . i . 2 . I .6 .6 . i .8 .0 7 5-2 6.0 4.2 3-6 6.4 3-6 6.6 6.3 1.8 6.2 3-6 3-7 2-7 3-8 2.7 3.6 1.8 1.8 1.8 2.7 5-4 3-7 3-o 2.8 2-5 4-2 8-5 7-3 8.4 6.8 6.8 9.2 5-4 9-6 8.7 4.6 9.1 7.2 6.2 4.3 6.1 4-4 6.2 2.1 2-5 1-4 3-9 6.1 4-3 5-6 3-4 2.7 5-0 II. 9.5 10.7 8.8 9.4 10.2 6.2 9 .6 9-3 5-2 9-3 6.9 7.0 4-3 6.5 5-4 7-7 2.8 4.1 1.8 4.7 7-0 4.2 6.0 3-0 3-3 5-8 12 .0 10-9 13.6 12.9 13*8 8.1 12.6 11.9 4.0 10. I 8.9 ii .1 6.5 6.6 4-4 5-7 2.3 ii 3-5 6-9 5-6 7-o 3-8 2.8 9-5 ii. 4 9-4 9-4 9.2 7.1 12.4 6.6 II .0 12.8 8.8 ii-S 9.2 10.2 7-7 10. 7-7 9.9 1.8 3-2 1-4 5-4 II .0 5-9 9.1 3-2 3-2 7-5 9.0 ii. 6 7-7 9-8 6.7 10.5 6.5 10.2 13-9 8.1 12.0 10.7 8.3 6.8 9-2 6.4 7.9 2.9 I -4 4-7 10.7 5-6 10.2 3-5 3-3 6.2 5-9 3-9 5-6 6.6 5-3 9.0 4-7 8.2 10.6 5-o 9-9 9-6 6-9 5-6 7.4 3-8 1.8 2.4 I -4 5-0 10. I 6.5 7-6 3-1 2-9 4-5 5-2 4-0 5-2 6.7 5-2 7-9 8.8 4.6 6.6 6.5 5-2 4.2 5-2 2-5 3-4 1.8 i!6 3-2 10.5 7-3 6.7 4.1 4-3 3-4 5-7 3-6 4.6 5-7 4.1 7-2 3-6 5-5 5-9 2.4 3-7 5-0 3-4 5-2 3-2 .7 .8 5 3 .8 7 5-9 3-9 3-8 3-0 3-2 Fort Davis Fort Stanton SOUTHERN PLATEAU: El Paso Santa Fe .... Fort Apache Fort Grant Prescott Keeler MIDDLE PLATEAU: Fort Bidwell Winnemucca Salt Lake City Montrose Fort Bridger NORTHERN PLATEAU: Boise City Spokane Falls Walla Walla N. PACIFIC COAST: Fort Canby Tatoosh Island Roseburg MID. PACIFIC COAST: Red Bluffs Sacramento S. PACIFIC COAST: Fresno Los Angeles San Diego ice it amounted to .06 inch per day, or about 7 inches in an ordi- nary season. The evaporation from snow is greater than this in the arid regions of the West, especially on barren mountain-tops UNIVERSITY EVAPORATION FROM EARTH 27 such as those in Arizona, Nevada, and Utah, where they are exposed to the wind and the bright sunshine. 30. Evaporation from Earth. The amount of evaporation from earth in the West is a doubtful quantity. Important ex- periments bearing on this were made in England between 1844 and 1875. From these it appears that the amount of evaporation from ordinary soil is about the same as that from wate, some- times exceeding it a little and sometimes being a trifle less, though TABLE VI. DEPTH OF EVAPORATION PER MONTH, IN INCHES. 1 Place. Annual. c rt 1 March. rs | j* i 1 $ > o 2 i 1889 1890 1889 1880 1889 1889 1890 1891 1892 1889 1889 1889 1890 1889 1889 1880 1890 1891 1890 1891 1890 1904 1890 1890 1890 1890 1890 1890 Bozeman Mont .... 3 4 4.5 5 3 i 9 2 6 Great Falls " 2 7 6 8 7 -I 6.1 f Fort Douglas, near 1 Salt Lake City, [ 1 Utah . j ; Nephi and Provo 10 . 5 5-7 g 3 -7 4.1 5 * l 7 6 6.5 4.6 . i I . 2 .JO .0 I .O i.S 2.1 3-2 2-3 4-8 4.1 5-2 5-3 i:! 7.6 6.5 5-0 7-9 6-5 7-3 4-6 8.6 7 > x 5-2 5-a 2.9 6.2 5 . I 3 . 2 6 i .4 1.6 2-5 i . i 2.2 Cherry Creek, Colo. . . . Canyort City, ' Lamar, Colo 3-8 4.8 5-2 7-3 6.0 7 - 2 Embudo, New Mexico.. . j Fort Bliss, near El 1 Paso, Texas J . Ternpe, Ariz 2.9 1 6 4-9 10.9 10.8 10. 5-5 10.7 xi. 7 13-0 Y.6 9.6 9.6 12.5 U-7 6.6 II. 4 7.6 xx. 9 14.1 9.2 9.2 II .0 5-8 6.8 6.S 6.4 5-2 4.6 3-7 4.2 4.4 4-6 2-9 3-0 2.9 3. a 9 r.6 2.O 2.7 2.4 2.O 2.9 3-2 7-o !:i 7-3 7-4 7-5 s'-8 4.2 8 7 " 83.5 3.9 3-6 i-l Florence, Yuma, 80.0 i 8 7.2 8.5 7. a 7 O 7-1 4-3 3.6 2.5 .5 Bloods, Cal Lake Eleanor, Cal Tuolumme Mead, Cal. . . Lake Tenaiya, "... 5 7 Little Yosemite, " ... 6 2 generally averaging about 3 inches less than the corresponding evaporation from water surfaces. The evaporation from sandy surfaces was found to be only about one-fourth to one-fifth that from water. Thus in the observations of 1873, where the mean evaporation from water was 20.4 inches, that from earth was 17.9 inches and from sand 3.7 inches. Soil cover of any kind greatly affects the amount of evaporation. Assuming the evap- oration from water is i.oo, Prof. B. E. Fernow gives it for bare 28 EVAPORATION, ABSORPTION, AND SEEPAGE soil 0.60; sod 1.92; cereals 1.73; and forest 1.51. Evaporation from ground covered with forest leaves is 10 to 15 per cent and sand 33 per cent, when from bare soil it is 100 per cent. 31. Effect of Evaporation on Water Storage. The value of water storage for irrigation in the West is realized chiefly between May and August inclusive. The only loss due to evapora- tion wkich practically affects the amount of storage water is that occurring during these months. Little or no rain falls in the arid region during this period, so that comparatively little of the loss of evaporation is replaced by rain. As an example, take Central California, where the average rainfall during these months amounts to a trifle less than i inch. The evaporation during the same period amounts to about 21 inches. The total resultant deficiency chargeable to evaporation is about 20 inches. Storage reservoirs in the West are frequently at high altitudes in the mountains, where evaporation is less than in the hot lowlands. At Arrowhead reservoir, Cal., altitude 5160 feet, the measured evaporation averages 36 inches per annum, of which about 40 per cent occurs between May and August, the irrigation season. 32. Percolation and its Amount. The losses due to per- colation in canals and storage reservoirs are very considerable, and added to those due to evaporation they increase the total loss by from 25 to 100 per cent according to the character of the soil. It is difficult to ascertain the losses due to percolation alone. For this reason it is desirable to consider losses from percolation and evaporation together and include them under the joint head of "absorption." From the experiments previously alluded to which were con- ducted by Mr. Greaves in England, it was found that while the evaporation from earth during the period of 23 years was 73.4 per cent of the rainfall, the percolation was but 26.6 per cent. From sand this percentage was nearly reversed, the loss by per- colation being about 30 inches, while the loss by evaporation was but 7 inches. There was no loss from percolation at all for several consecutive months. As an average year take that of 1872, when the rainfall amounted to 23.8 inches and the evaporation ABSORPTION 29 from water 20.4 inches, the losses by percolation amounting to 4 inches in earth and 20.1 inches in sand. From observations and experiments made in Bavaria it appeared that whereas in the warm summer months the depth of percolation on open bare ground was u per cent of the rainfall, in forests it amounted to as high as 36 per cent of the rainfall. In our West these quantities will be materially different. The amount of rainfall is relatively small on the ordinary mountain catchment basin. The slopes are steep and generally rocky. As a result of this the percentage of percolation will be low, the amount of runoff being relatively higher. Where there are dense forests, the soil beneath which is covered with a depth of litter, or where the slopes are low, the percentage of percolation will be relatively high. The effect of vegetation or other soil cover on percolation is to reduce the latter, being thus the reverse of its effect on evaporation, and hence nearly balancing its net effect on absorption. Wollny found the percolation from loam 20 inches deep to be 33 per cent of the precipitation, and for the same covered with grass 1.3 per cent. For sand it was 65 per cent, and for the same grass covered 14.0 per cent. 33. Absorption. Mr. J. S. Beresford, of India, argues that the losses by percolation are due to capillary attraction and the action of gravity. The latter takes place only through coarse sand or gravel, while the former is a more complicated process acting where the particles are fine and in close contact one with the other. Capillary attraction stops where the absorbing medium is limited, for as soon as water which has been carried by its action through a bank reaches the outer surface, percolation ceases and evapora- tion comes into play. It is for this reason that banks of sand even when well rammed will retain water. The more extensive the absorbing medium the greater the losses from this cause; hence the loss by absorption is greater when a canal is in cutting than when in embankment. If the extent of the absorbing medium be limited by a bed of clay placed under either the reser- voir or canal in which percolation occurs, then the losses due to this cause are rapidly diminished in quantity. The layer next the wetted perimeter limits the quantity absorbed, and the greater 30 EVAPORATION, ABSORPTION, AND SEEPAGE its area the more will it pass through to the still greater area of the next layer ; hence percolation varies as the wetted perimeter. 34. Amount of Absorption in Reservoirs and Canals. The volume of this is very difficult to ascertain and varies greatly with soil and climate. If the bottom of the reservoir is com- posed of sandy soil, the losses from percolation and evaporation combined will be about double those from the latter alone. Whereas, if the bottom of the reservoir be of clayey material, or if the reservoir be old and the percolation limited by the sediment deposited on its bottom, this loss may be but little more than that of evaporation alone. On a moderate-sized canal in India the total losses due to absorption have been found to amount to about one second-foot per linear mile. In new canals these losses are greatest. If the soil is sandy, the losses on new canals may amount for long lines to from 40 to 60 per cent of the volume entering the head. In shorter canals the percentage of loss will be proportionately decreased, though it will rarely fall below 30 per cent in new canals of moderate length. As the canal increases in age the silt carried in suspension will be deposited on its banks and bottom, thus filling up the interstices and diminishing the loss. In old canals with lengths varying between 30 and 40 miles the loss may be as low as 12 per cent in favorable soil, though in general for canals of average length the loss will be about 20 to 25 per cent of the volume entering the head (Art. 65). On the Ganges canal in India, the length of which is several hundred miles, the losses in some years have been as high as 70 per cent. Experiments made on Indian canals where the climate and soil are similar to our own show that the loss by evaporation alone on medium-sized canals is about 5 per cent of the probable discharge, showing that the greater portion of the loss by absorp- tion is from percolation. 35. Prevention of Percolation. An excellent method for the reduction of the loss by percolation is that recommended by Mr. Beresford who advises that pulverized dry clay be thrown into the canals near the headgates. This will be carried long distances and deposited on the sides and bottom of the SEEPAGE WATER 31 canal, forming a silt berme. The losses by absorption are greatly increased by giving the canal a bad cross-section. Thus depressions along the line of a new canal are often utilized to cheapen construction by building up a bank on the lower side only, thus allowing the water to spread and consequently in- creasing the absorption. The least possible wetted perimeter and the least surface exposed to the atmosphere will cause the least loss from this cause. 36. Seepage Water. In many instances where canals and reservoirs are bordered by steep hillsides the amount of water lost may prove to be much less than would be expected. This is due to the fact that large amounts of seepage water may enter the canal or reservoir from the surrounding country and thus replenish to a large extent the losses from absorption. Before irrigation becomes general in any locality it is fre- quently impossible to derive any water from wells, as the sub- surface-water level may be at a great depth below the surface. After irrigation has been practised for some time, however, the soil becomes filled with water and the subsurface level rises so that shallow wells often yield persistent supplies. In portions of California, especially in the neighborhood of Fresno, where the subsurface-water level was originally from 60 to 80 feet below the surface, wells 10 and 15 feet in depth now receive constant supplies, the result of seepage from the canals. Water used in irrigating is in large part returned to the drainage channels and can be again diverted for irrigation. 37. Amount of Seepage Water. The State Engineer of Colorado conducted measurements of seepage water returned to the South Platte and Cache la Poudre rivers during the years 1890 to 1893 inclusive. These showed a constant increase in the amount of seepage water returned to these streams and available for diversion below the points of measurement. On the South Platte River, in a distance of 397 miles, the entire gain from seepage water was, in 1893, 573 second-feet, or a gain of 430.5 per cent over that in the river at the upper measuring station. In other words, several times the amount which was diverted from the river was returned to it through 32 EVAPORATION, ABSORPTION, AND SEEPAGE seepage from the surrounding country. On the same portion of the river the percentage of increase in 1891 was 300, or three times the flow at the first measuring station. In 1891 the average increase from seepage on the South Platte was 3.24 second-feet per mile. In 1893 it was 4.0 second -feet per mile, but was as great in one mile as 13.7 second-feet, varying between these limits. On the Cache la Poudre, experiments made in 1889 show that while the original discharge at the canyon was 127.6 second-feet, the volume at a point considerably lower down the stream had in- creased to 214.7 second-feet, after supplying fifteen canals and without receiving additional natural drainage. Experiments on the same river during succeeding years showed similar results. The average amount of seepage water returned to the Cache la Poudre during the several years of observation was 2.4 second- feet per mile. Seepage losses measured in canals in California were i to 5 second-feet per mile. In an unusually porous canal near Fresno such losses amounted to 15 second-feet per mile. Prof. L. G. Carpenter sums up his investigations on this subject thus : " There is real increase in the volumes of streams as they pass through irrigated sections. This increase is approximately pro- portional to the irrigated area. The passage of seepage water through it is very slow. The amount of seepage water slowly but constantly increases. This seepage water adds to the amount of culturable land. On the Cache la Poudre River about 30 per cent of the water applied in irrigation is returned to the river." Investigations of a similar nature conducted by the Utah Agricultural Experiment Station and by others all point in the same direction. The amounts of returned water by seepage indicated in the above experiments must not be taken as a criterion of what may be expected in other regions. The circumstances surrounding these cases are believed to be especially favorable for the return of seepage water. It is believed that from this, as almost a maximum, the amount of seepage water returned may diminish to practically nothing, dependent upon the soil, quality of underlying strata, their slope and inclination, and the area of drainage basin above and tributary to them. Observations made at storage reservoirs for New York and WORKS OF REFERENCE 33 Boston and some other Eastern cities show clearly that the amount of seepage water returned from the surrounding country to reservoirs which have been drawn down for service varies between 10 and 30 per cent of their capacities. This is supposed to be largely due to the fact that the water plane of the surround- ing country is filled up from the reservoir as well as from seepage from the adjacent country. Measurements of volume in the Sweetwater reservoir in Southern California show that after water ceases to be drawn from the reservoir it begins to fill up while no water is entering from streams, thus indicating that similar additions from seepage may be anticipated for Western reservoirs. As a result, the actual available capacity of a storage reservoir will probably be found to be greater than its measured capacity in spite of the losses which it sustains from evaporation and percolation. It will perhaps be more correct in designing reservoirs to assume that these gains and losses balance. 38. Works of Reference. Evaporation, Absorption, Seepage. BERESFORD, J. S. Memorandum on the Irrigation Duty of Water. Prof. Papers on Indian Engineering, No. 212. Roorkee, India. BUCKLEY, R. B. Irrigation Works in India and Egypt. E. & F. N. Spon, Lon- don, 1893. CRAMER, C. B. Seventh Biennial Report of State Engineer. Denver, Colo., 1894. EVANS, John. Percolation of Rainfall on Absorbent Soils. Trans. Inst. C. E., vol. 45. London, 1875. FITZGERALD, DESMOND. Evaporation. Trans. Am. Soc. C. E., vol. 15. New York, 1886. Rainfall, Flow of Streams, and Storage. Trans. Am. Soc. C. E., vol. 27. New York, 1892. FORTIER, SAMUEL. Water for Irrigation. Bulletin 26, Agricultural Experiment Station, Logan, Utah. December, 1893. - Preliminary Report on Seepage Water, etc. Bulletin 38, Agricultural Experiment Station, Logan, Utah. February, 1895. Evaporation, Bulletin 177, Office of Experiment Stations. U. S. Depart- ment of Agriculture. Washington, D. C., 1907. GREAVES, CHARLES. Evaporation and Percolation. Trans. Inst. C. E., vol. 45. London, 1875. MAXWELL, J. P. Sixth Biennial Report of State Engineer. Denver, Colo., 1892. NEWELL, F. H. Hydrography. Parts II of nth to i3th Annual Reports, U. S. Geological Survey. Washington, D. C., 1891. SLIGHTER, C. S. Motion of Underground Waters. Water-Supply Paper No. 67, U. S. Geological Survey. Washington, D. C., 1902. WILSON, H. M. Irrigation in India. Part II, i2th Annual Report, U. S. Geo- logical Survey. Washington, D. C., 1891. I CHAPTER IV ALKALI, DRAINAGE, AND SEDIMENTATION 39. Harmful Effects of Irrigation. When irrigation is prac- tised without proper attention to drainage it is liable to result in the following evils: (i) production of alkali or flocculent salts on the surface of the ground; (2) souring or waterlogging of the soil due to supersaturation ; (3) fevers and other injurious effects, the result of the same cause. 40. Alkali. The white efflorescent salt known as " alkali" is to be found in many portions of the West, both as the result of irrigation and occurring naturally over extensive areas. This salt has been analyzed and found to consist chiefly of chloride (common salt), carbonate (sal soda), and sulphate (Glauber's salt) of sodium. The relative proportions of these vary greatly, but the latter is nearly always present and predominates, rang- ing from 5 to 75 per cent. There is generally also present a small amount of accessory salts, as manganese sulphate and the salts of potassium. Of the latter, the nitrates and phos- phates are of value, as they are the ingredients usually supplied in fertilizers. Their presence therefore indicates the occurrence of sufficient plant-food in the soil to render fertilization unneces- sary. Perhaps the most harmful of the alkaline salts is sodium carbonate, commonly called "black alkali." This is more generally found in the warmer climates and in moist close soil, rich in humus, such as is found in the San Joaquin valley of California, and it is mainly found in low ground, where the alkali occurs in spots. It is greatest in amount near the centre of the spots, while potash, on the contrary, increases in amount near the margin. The effect of alkali is to kill all vegetable matter and to render the soil barren and unproductive. 41. Causes of Alkali. Where the natural drainage of the 34 WATERLOGGING 55 country is defective and the strata underlying the surface are impervious or the soil not deep, irrigation or rainfall causes the subsurface-water plane to rise to such a height that finally the soil becomes saturated. Evaporation then takes place from the surface, and as this process continues there are left on the soil the salts contained in the water. Thus the more water that evaporates from the surface the more alkali will be deposited, and increased rainfall or irrigation will increase the amount of alkali. It is thus seen that the direct cause of the production of alkali is the rise of the subsurface-water plane due to defective drainage and its evaporation from the surface. Seepage from badly constructed canals is a great producer of alkali. Thus where the velocity of the canal is slow, time is given for water to soak into the soil and permeate it. Prof. E. W. Hilgard's ex- periments show that the main mass of alkaline salts exists in the soil within a short distance of the surface, and that the amount of these salts is limited. He therefore asserts that the bulk of alkali salts is accumulated within easy reach of underdrains, and if once removed not enough to do harm will again come from below. 42. Waterlogging. Where the rise of water from the sub- surface or its addition to the surface from natural causes or ir- rigation is more rapid than the losses by evaporation or drainage, the water stands in pools and the soil becomes soft and marshy, producing the effect known as "swamping" or "waterlogging." Like alkali, waterlogging is directly traceable to defective drain- age and the careless use of water. Where the conditions are sufficiently well balanced for drainage to prevent the rise of the subsurface- water to within 10 or 15 feet of the surface, continued irrigation produces good results by soaking up the lower strata and giving an abundance of water near the surface for wells and for moistening the deeper-rooting plants. 43. Prevention of Alkali and Waterlogging. Since evapora- tion causes the rise of alkali, evaporation should be reduced to the lowest point. This may be done by mulching the soil. It is also possible in some cases to cultivate deep-rooting plants or such as shade the soil and reduce the amount of evaporation, 36 ALKALI, DRAINAGE, AND SEDIMENTATION or such as are least harmfully affected by its presence, thus miti- gating the evil and permitting some use to be made of the land. Irrigating only such lands as have good natural drainage, and exercising care not to interfere with this, is one of the best and surest preventives of the production of alkali and waterlogging. The introduction of artificial drainage produces the same effect, while in a lesser degree the same result may be obtained by the use of deep ditches or furrows which themselves act as drainage channels. When the quantity of alkali is small, the evil effects resulting from its presence may be mitigated by the application of chemical antidotes; and, lastly, relief may be obtained in some cases by watering the surface and drawing off the water without allowing it to soak into the ground. This system of reclaiming the land by surface washing and drawing off the salt-impregnated water is known as ' ' leaching. ' ' One of the most effective methods for the prevention of alkali is the judicious and sparing use of water in irrigation where the drainage is defective. As a result of his investigations in northern Africa, Mr. Thomas H. Means states that the amount of soluble matter allow- able in an irrigation water has been greatly underestimated, and that many sources of water which have been condemned can be used with safety and success with proper precautions. The Arabs in the Sahara successfully grow vegetables with water containing as high as 800 parts of soluble salts to 100,000 parts of water, sometimes 50 per cent of the salts being sodium chloride. The Arab gardens consist of small plots 20 feet square, between which are drainage ditches dug to a depth of about 3 feet. This ditch- ing at short intervals insures rapid drainage. Irrigation is by the check method and application made at least once a week, sometimes oftener. A large quantity of water is used at each irrigation, thus securing the continuous movement of the water downward, permitting little opportunity for the soil water to become more concentrated when the irrigation water is applied, and there is little accumulation of salt from the evaporation at the surface. What concentration or evaporation accumulation does occur is quickly corrected by the succeeding irrigation. 44. Chemical Treatment. A cheap antidote for many alkaline CHEMICAL TREATMENT 37 salts is common lime, while neutral calcareous marl will answer in some cases. When the alkali consists of carbonates and borates, the best antidote is gypsum or plaster of Paris. Notable experiments have been made by Prof. E. W. Hilgard, which prove the value of gypsum in neutralizing the " black alkali," or car- bonate of soda. In the case of this alkali one of the worst- mulching, deep tillage, suitable plant-growth, or any other corrective except gypsum is practically unavailing. Little benefit is to be expected from gypsum in the case of "white" or neutral alkali, which does little harm, however, under proper tillage; but a soil heavily tainted with black alkali can be rendered profusely productive by the use, once for all, of a ton of gypsum per acre. This is more effective when applied at the rate of about 500 pounds per acre per annum in connection with some seeding at the same time, for the slightest growth aids in shading the ground and preventing an injurious release of salts by evaporation. Gypsum, however, cannot be used on alkali without water; its action must be continued for several months and through two or three seasons ; it takes, moreover, several weeks before immunity is secured, and therefore the dressing of gypsum should be applied in ample time before the seeding; and thereafter the soil must be well cultivated and ploughed in, and promptly followed by irrigation. Where there is not a good natural drainage, underdrains must be provided in reclaiming alkaline soil by chemical treat- ment. Gypsum acts practically by converting the harmful car- bonate of sodium into the less harmful sulphate of sodium in the presence of water and with the aid of thorough mixing by ploughing, and these salts are washed through the soil and are carried off into natural drainage channels, or, if the locality treated be a sink, concentrated in its bottom. A cheap form of underdrain consists of boards placed together like the letter A, at a depth of about 3 feet beneath the surface. These drains should discharge either into the sink-hole or drainage channel. Such drains can be constructed for about $30 per acre. Mere surface treatment without drainage, in soils strongly impregnated with black alkali, would change the latter to white alkali, but would still leave too much of this in the soil for the growth of 38 ALKALI, DRAINAGE, AND SEDIMENTATION useful vegetation. Wherever black alkali exists the use of stable manure is harmful by setting free corrosive ammonia vapors. 45. Mulching and Leaching. An excellent preventive against evaporation from the soil surface and the consequent production of alkali is by "mulching." The best mulch is a well and deep tilled surface soil, which is kept so constantly stirred that a crust is never allowed to form. As a result evaporation is reduced to a minimum, and the alkali remains distributed throughout the whole of the tilled layer instead of as a hard crust at the surface where the bulk of the damage is done. Ploughing in large quantities of straw produces also an effective mulch, since the straw keeps the surface loose and enables the grain to germinate. The depth or thickness of this protective tilled layer is of the utmost importance, for thereby the strong surface alkali is diluted with the largest possible mass of subsoil. After a proper tilling to a depth of, say, 10 to 12 inches, it requires a long time for the salts to come to the surface again in sufficient amount to injure the crop. Leaching is not infrequently employed, more especially in Europe, to mitigate the harmful effects of alkali. This is practised by building temporary embankments around the land and then flooding it, after which the salt-impregnated waters are rapidly drawn or pumped off. 46. Growth of Suitable Plants. One of the most effective plants which can be grown on slightly alkaline soil is alfalfa, which when once established brings to bear the action of deep roots and dense shade, and thus by repression of surface evapora- tion tends to restore the soil to its natural condition. Where mulching is practised it is desirable to grow hoed crops, such as beans, beets, potatoes, corn, onions, and canaigre, choosing preferably the deeper-rooted of these. Experiments recently conducted by Mr. M. E. Jaffa indi- cate that Australian salt-bush is likely to prove one of the most desirable forage plants for growth on alkali soils. It is readily eaten by stock, is rich in digestible nutrients, and has been suc- cessfully grown on alkaline land which will produce no other crop. This plant is wonderful for its productiveness and its DRAINAGE 39 drought-resisting power. It is prostrate in its growth, covering the ground with a green cushion 8 to 10 inches thick, and thus effectually shading it. It is perennial, and when cut soon re- produces itself from the same root. Its. yield per acre is very large, being about the same as that of alfalfa. 47. Drainage. Generally the drainage of irrigated land will take care of itself if the natural drainage channels are not interfered with or obstructed. Where the surface has a mod- erate though sufficient slope to allow the water to flow off, or the soil is underlain by deep beds of gravel or porous rocks which will carry off the percolation water, irrigation may be practised for all time, and even an excessive amount of water may be used without seriously affecting the crops. In some cases the drainage may be improved by digging drainage channels or ditches or laying drainage pipes under the surface. In many portions of the West, and especially in the San Joaquin valley in California, old sloughs and abandoned natural drainage lines have been utilized as irrigation channels. The effect is bad, as the natural drainage lines thus become over- loaded, resulting in waterlogging the soil. In this way large areas in Fresno County and its neighborhood have been rendered uncultivable, whereas with a proper system of irrigating channels, providing the natural drainage channels had been left open, no evil effects would necessarily have resulted. In most regions where the slopes are very slight, as in river bottoms and where irrigation has been practised for many years, like Lombardy, Italy, and in the lower San Joaquin valley, California, drainage becomes quite as important as irrigation, and it is extremely necessary to provide some means of conducting seepage water to the streams. In some places where the streams flow in channels above the surrounding land it is even necessary to build dikes to confine the seepage water and to pump this back to the streams. 48. Excessive Use of Water. This is one of the greatest evils at present noticeable in our western irrigation methods. Almost invariably too much water is employed in irrigating crops. The result is waste of water and oversaturation of the 40 ALKALI, DRAINAGE, AND SEDIMENTATION soil. As the value of water rises it will be used with less ex- travagance. Proper care in the location and construction of the canal banks will aid greatly in reducing the evil effects of irrigation. If the location is bad, the natural drainage channels may be interfered with. If the construction is bad, the loss by seepage from the canal into the soil becomes great. With proper drainage too much water cannot be used. 49. Silt. Great volumes of silt are transported by Western rivers in times of flood a result chiefly of the erosion of the alluvial banks of the stream and its tributaries. The heavier sand and gravel is usually deposited in the upper reaches of the stream, and the great bulk of the silt reaching the canals is of the finest quality. As the velocity in the canals is relatively slow, much of the matter carried in suspension is deposited near their heads, or in storage reservoirs or other slack water, thus diminishing the discharge of the canal or the volume of the reser- voir. Silt consists of both organic and mineral matter, and while the former especially is often a source of advantage to the crops, it is generally a great cause of trouble in the irrigation channels. It is desirable to pass forward to the fields as much of the fertiliz- ing matter carried in suspension as possible, and at the same time to prevent the deposition of sediment in the canal. This result is brought about by various devices in the construction of the canal headworks whereby the heavier sands and gravels are deposited just in front of diversion weirs or carried through undersluices in these, or are deposited in the upper reaches of the canals, whence they can be readily flushed by sand gates and escapes, or, if no other means of removal be practicable, by dredging. 50. Character of Silt. Silt varies greatly in its nature, depending chiefly upon the velocity of the stream and upon the soil and topography of its catchment basin. In the upper reaches of a stream where the slopes are great, the fall of the stream bed rapid, and the velocity correspondingly high, the sediment moved by the water consists chiefly of bowlders, shingle, and large gravel. Much of this is not actually carried in sus- AMOUNT OF SILT pension, but is merely rolled along the stream bed. Lower down on the same stream, where the velocity is 4 to 7 feet a second, the sediment consists chiefly of coarse sand or mud, the former of which is usually near the bed and is rather rolled upon it than carried in suspension. Still lower down on such a stream, or in canals the velocities of which are but 2 or 3 feet a second, only the finest silt, rich in organic matter, is carried in suspension. 51. Amount of Silt. The amount of sediment which is carried in suspension during floods is greater than is usually appreciated. From investigations made by the United States Geological Survey on the Rio Grande in 1889, it was found to range from J to J of i per cent of the volume of flow. It was also estimated that in about one hundred and fifty years the amount of this sediment would seriously impair a reservoir 60 feet in depth. On the American River at Folsom, California, in a single year a depth of nearly 10 feet of wet silt was deposited in a reservoir situated at that point. Much of this, however, was heavy matter, bowlders and gravel rolled along the stream bottom by the swift current. Mr. R. B. Buckley states that the proportion of silt to water by weight, in several rivers, is as follows : Mississippi i to 572 Rhone, France (velocity 8 feet per second) i to 45 Po, Italy i to 300 Rhine, Germany i to 100 Indus, India (velocity from 3$ to 5 feet per second)., i to 237 The amount of sediment deposited in reservoirs by turbid streams may be so great as materially to reduce their capacities in a few years. Careful tests must, therefore, be made to de- termine the possible amount of this and its effect. In twelve years the amount of sediment deposited in Sweetwater reservoir, Cal., was 900 acre-feet. In that time 1 80, coo acre-feet of water had entered the reservoir. The amount of measured solids deposited thus averaged about half of one per cent. Care- ful sampling of the Gila River water, Arizona, to determine the possible life of a reservoir of 174,000 acre-feet capacity developed the fact that the mud carried in suspension in a year averaged 10.5 per cent, and the amount of solids 2 per cent. In a year 42 ALKALI, DRAINAGE, AND SEDIMENTATION this reservoir would accumulate 9597 acre-feet of solid sediment, and its life would be but 18^ years, On the Soane canal in India, which is diverted from a river having a maximum velocity of 7.5 feet per second, as much as from 3 to 5 feet of sand and coarser material is deposited in the first quarter mile of the canal, gradually diminishing in depth until but a few inches are deposited at 5 or 6 miles from its head. As already stated, the greater proportion of the silt is heavy matter floating near or rolled along the bottom ; and as shown by experiments conducted on the Rhine with a flood velocity of 8 feet per second, this silt near the bottom was as much as 88 per cent greater in amount than that at the surface. It was observed also that there is more silt in a rising flood than in a falling one, and the maximum amount of silt is carried when the flood has reached about two-thirds of its height. It is be- cause of this reason that under-sluices in storage dams (Arts. 1 86 and 347) are of value, as the water may be permitted to waste through these until the maximum flood height has been reached, after which they may be closed and the remaining flood waters, which are less heavily charged with silt, be stored. 52. Prevention of Sedimentation in Reservoirs and Canals. In view of the important bearing which sediment carried in suspension has upon irrigation water, it is necessary to con- sider the quality and amount of sediment in the source of water supply of any irrigation work. Where a canal is taken from a stream of high velocity, which usually carries but little fertilizing material and much heavier matter, it is necessary to design the head works in such manner that most of this shall be excluded, and to cause the deposition of the remainder in a short distance in the upper reaches of the canal. With streams of lower velocity, the problem to be solved is usually how to align the canals and distributaries and choose their slopes and velocities, so that the heavier particles which are suspended near the bed of the stream shall be deposited close to the headworks of the canal, while the lighter silt containing the fertilizing properties shall remain in sus- pension until deposited on the fields. There are practically but tw r o methods of mitigating the PREVENTION OF SEDIMENTATION .43 injury due to sedimentation in reservoirs. One is by building higher up on the stream cheap settling reservoirs which may be destroyed in the course of a number of years, or the dams may be increased in height as they silt up. The other method is by the construction of under- or scouring-sluices in the bottom of the dam. These have not as yet proved effectual, as their influence is felt at but a short distance back from the opening. Experience has shown that they do not remove silt which has already been deposited, but, providing their area is large compared with the flood volume of the stream, they may effectively prevent the deposition of sediment by permitting the silt-laden waters to flow through the reservoir; the latter being filled only after the flood has subsided and the waters become less turbid. Canals should be so designed that the angle at which they are diverted from the main stream shall be such as to cause the least back eddy in front of the headgates and the least deposit at that point. Where a canal is taken off at right angles to the line of the stream and scouring-sluices are placed in the weir immediately adjacent to the headgates, the main stream may be so trained as to have a straight sweep past the headgates, and thus scour out any deposits occurring at that point. As the velocity of the current is generally diminished in the upper portion of the canal in its passage from the main stream, the deposit of silt is likely to occur at this point. It may be well to encourage this by increasing the cross-section of the canal and reducing its grade so that its capacity shall remain the same but its velocity be diminished. Then the deposit of silt will all occur in the first half-mile or less of the canal, and it may be either dredged out or perhaps scoured out by an escape. Several methods of removing silt from canal waters have been practised in India for a number of years. The older and least satisfactory is by digging borrow-pits in the bed of the canal, the reduction of velocity over these causing some deposition. Another is by the construction of external parallel canals, with cross- banks at 4000 to 5000 feet intervals, with head inlets and tail outlets, the whole canal supply being passed through these. The velocity being reduced causes deposition, thus making of them 44 ALKALI, DRAINAGE, AND SEDIMENTATION settling-basins. The most satisfactory system and that more generally employed consists in building the canal banks back from the channel, with low spur-berms extending inward to the margin of the channel or future inner bank. The effect of these spurs is to shallow the water flowing over them and reduce the velocity between them, causing the deposition of silt. 53. Fertilizing Effects of Sediment. The value of silt- bearing water as a fertilizer is well known. In the valley of the Moselle, France, on land absolutely barren and worthless with- out fertilization, the alluvial matter deposited by irrigation from turbid water renders the soil capable of producing two crops a year. In the valley of the Durance, France, the turbid waters of that stream bring a price for irrigation which is ten or twelve times greater than that paid for the clear cold water of the Sorgues River. It has been estimated that on the line of the Galloway canal in California, land which has been irrigated with the muddy river water gives 18 per cent better results after the fifth year than the same land which has been irrigated with clear artesian water. 54. Weeds. When from any cause it becomes necessary to give a canal a low velocity, the growth of water-weeds and the deposition of silt are encouraged. Water-plants grow most freely where the current has a slow velocity and the depth is such that the sunshine reaches the bottom. They thrive in shallow reservoirs, thus diminishing their capacity. Brush, willows, weeds, and rushes, may encroach on the channels of canals, where the slopes of the banks are low, and so diminish the waterway as to reduce greatly the carrying capacity of the canal. Provided a high velocity cannot be given, the only pos- sible way of remedying this is to draw off the water and destroy the plants. On the Pavia canal, Italy, the growth of aquatic plants is so rank as to require, in addition to two annual clearings, chiefly for silt, the constant use of floating cutting-machines. 55. Malarial Effects of Irrigation. In numerous localities, both abroad and in the West, irrigation has been denounced as a serious menace to the health of the community because of the creation of swamps and their malarial effects. From careful researches, both by a committee to the Indian Government and MALARIAL EFFECTS OF IRRIGATION 45 by Dr. H. O. Orme of the California State Board of Health, it appears that these evil effects have been exaggerated, and may be avoided, either by more sparing use of water, by proper drainage, or by abandoning irrigation in limited localities which it is im- possible properly to drain. In Southern California, between Los Angeles and San Diego, where the natural drainage is of the best, the soil as a rule sandy or gravelly and open to a great depth, the water used in irrigation sinks into the ground or drains off, and the use of almost any amount of water does not breed malarial mosquitoes. On the other hand, in such regions as the low-lying, comparatively level lands of the lower part of the Sacramento and San Joaquin valleys, where the soil is heavy, the slopes slight, and the underdrainage poor, it is undoubtedly true that irrigation has developed various disorders, by raising the subsurface water-plane, thus causing the water to stand in swamps or stagnant pools, breeding malarial mosquitoes. Malarial effects are not attributable directly to the results of irrigation where economically and properly practised, but are frequently due to carelessly constructed canal works having intercepted the natural drainage, thus forming swampy tracts. It appears certain that when care is taken to irrigate only land which has an open soil and such slopes and natural drainage as to prevent waterlogging, no unhealthy effects will result from irrigation; also, that when malarial influences are developed by irrigation their effect is almost strictly local. It is desirable, in order to mitigate the possible evil effects of irrigation, to keep the canal as much as possible within soil so that its surface level may be low, and thus only raise the sub- surface water-plane to the least height practicable; that earth wanted to complete embankments be never taken from exca- vations or borrow-pits except where such localities admit readily of drainage; that the canal and its branches be aligned as far as possible along the watershed of the country so as not to interfere with drainage. If wholesome water and not open-ditch water be provided for domestic uses, prejudical effects of irrigation are largely averted. In such climates as will encourage its growth it appears that the Eucalyptus globulus has proved beneficial 46 ALKALI, DRAINAGE, AND SEDIMENTATION in mitigating the malarial effects of irrigation waters, chiefly because of the great absorbing and transpiring power due to its rapid growth. The destruction of mosquito larvae will en- tirely remove the source of malarial disorders. 56. Works of Reference. Alkali, Drainage, and Sedimenta- tion. BUCKLEY, R. B. Irrigation Works in India and Egypt. E. & F. N. Spon. Lon- don, 1893. DAVIS, ARTHUR P. Report on Irrigation Investigation, etc. Senate Doc. No. 27, Fifty-fourth Cong., 2d Ses. Washington, D. C., 1896. DEAKIN, ALFRED. Royal Commission on Water Supply. First and Fourth Progress Reports: Irrigation in Western America, Egypt, and Italy. Mel- bourne, 1884. HILGARD, E. W. Alkali Lands. Report of University of California. Sacra- mento, 1886. - Distribution of Salts in Alkali Soils. Bulletin 108, Univ. of Cal. Agri. Exper. Station. Berkeley, 1895. Report of the Work of Agricultural Experiment Stations. Univ. of Cal. Sacramento, 1894. JAFFA, M. E. Australian Salt-bush. Bulletin 105, Univ. of Cal. Agric. Exper. Station. Berkeley, 1894. WILSON, HERBERT M. Irrigation in India. Part II of i2th Am. Report of U. S. Geological Survey. Washington, D. C., 1891. CHAPTER V QUANTITY OF WATER REQUIRED 57. Duty of Water. The duty of water may be defined as the ratio between a given quantity of water and the area of crop which it will mature. In order to determine what amount of water is sufficient to irrigate a given area of land it is first necessary to determine at least approximately its duty for the specific case under consideration. On the duty of water depends the financial success of every irrigation enterprise, for as water becomes scarce its value increases. In order to estimate the cost of irrigation in projecting works, it is essential to know how much water the land will require. In order to ascertain the dimensions of canals and reservoirs for the irrigation of given areas the duty of water must be known. 58. Units of Measure for Water Duty and Flow. Before considering the numerical expression of water duty, the standard units of measurement should be defined. For bodies of standing water, as in reservoirs, the standard unit is the " cubic foot." In the consideration of large volumes of water, however, the cubic foot is too small a unit to handle conveniently, and the "acre-foot" which is the amount of water that will cover one acre of land one foot in depth, that is, 43,560 cubic feet is preferable, especially as it bears a direct relation to the unit used in defining areas cultivated. Hence the capacity of a reser- voir in acre-feet expresses a direct ratio to the number of acres which it will irrigate, or its duty per acre-foot. In considering running streams, as rivers or canals, the expression of volume must be coupled with a factor representing the rate of movement. The time unit usually employed by irrigation engineers is the second, and the unit of measurement of flowing water is the cubic foot per second, or the " second -foot," or "cusec" as it is called for brevity. Thus the number of second-feet flowing in a canal 47 48 QUANTITY OF WATER REQUIRED is the number of cubic feet which pass a given point in a second of time. A unit still employed in the West is the "miner's inch." This varies greatly in different localities, and is denned by State statute. In California one second-foot of water is equal to about 40 miner's inches, while in Colorado it is equivalent to about 38.4 miner's inches. The period of time during which water is applied to the land for irrigation from the time of the first watering until after the last watering of the season is known as the "irrigating period." This is generally divided into several "service periods," by which is meant the time during which water is permitted to flow on the land for any given watering. Each method of expressing duty is readily convertible into the other, providing the irrigating period be known. The fol- lowing simple formulas are given by Mr. R. B. Buckley for use in making such conversions : Z> = duty of water in second-feet; B = irrigating period per second-foot ; V = cubic feet of water required to mature one acre of crop ; 5 = total depth in inches of volume used if evenly distributed over area irrigated; Q = discharge in second-feet required to irrigate a given area (A), with a given duty (Z>), and irrigating period (B}. ~n F= X 86,400 ...... (4) 5=^X23.8 ........ (5) D 23.8.8 The following are a few convenient equivalents: TABLE VII. UNITS OF MEASURE. i second-foot equals 40 California miner's inches (law of March 23, 1901). i second-foot equals 38.4 Colorado miner's inches. i second-foot equals 40 Arizona miner's inches. i second-foot equals 7.48 United States gallons per second; equals 448.8 gal lons per minute; equals 646,272 gallons for one day. UNITS OF MEASURE FOR WATER DUTY AND FLOW 49 TABLE VII Continued. i second-foot equals 6.23 British imperial gallons per second, i second-foot for one year covers i square mile 1.131 feet or 13.572 inches deep. i second-foot for one year equals 31,536,000 cubic feet, i second-foot equals about i acre-inch per hour, i second-foot for one day covers i square mile 0.03719 inch deep, i second-foot for one 28-day month covers i square mile 1.041 inches deep, i second-foot for one 29-day month covers i square mile 1.079 inches deep, i second-foot for one 3O-day month covers i square mile 1.116 inches deep, i second-foot for one 3i-day month covers i square mile 1.153 inches deep, i second-foot for one day equals 1.983 acre-feet, i second-foot for one 28-day month equals 55.54 acre-feet, i second-foot for one 29-day month equals 57.52 acre-feet, i second-foot for one 30-day month equals 59.50 acre-feet, i second-foot for one 31 -day month equals 61.49 acre-feet. 100 California miner's inches equal 18.7 United States gallons per second. 100 California miner's inches equal 96.0 Colorado miner's inches. 100 California miner's inches for one day equal 4.96 acre-feet. 100 Colorado miner's inches equal 2.60 second-feet. 100 Colorado miner's inches equal 19.5 United States gallons per second. 100 Colorado miner's inches equal 104 California miner's inches. 100 Colorado miner's inches for one day equal 5.17 acre-feet. 100 United States gallons per minute equal 0.223 second-foot. 100 United States gallons per minute for one day equal 0.442 acre-foot. ,000,000 United States gallons per day equal 1.55 second-feet. ,000,000 United States gallons equal 3.07 acre-feet. ,000,000 cubic feet equal 22.95 acre-feet. acre-foot equals 325,850 gallons. inch deep on i square mile equals 2,323,200 cubic feet. inch deep on i square mile equals 0.0737 second-foot per year. foot equals 0.3048 meter. mile equals 1.60935 kilometers. mile equals 5,280 feet. acre equals 0.4047 hectare. acre equals 43,560 square feet. acre equals 209 feet square, nearly. square mile equals 2.59 square kilometers. cubic foot equals 0.0283 cubic meter. cubic foot equals 7.48 gallons. cubic foot of water weighs 62.5 pounds. cubic meter per minute equals 0.5886 second-foot. horsepower equals 550 foot-pounds per second. horsepower equals 76.0 kilogram-meters per second. horsepower equals 746 watts. horsepower equals i second-foot falling 8.80 feet, if horsepower equal about i kilowatt. Sec.-ft. X fall in feet To calculate water power quickly : - = net horsepower on water wheel, realizing 80 per cent of theoretical power. 4 50 QUANTITY OF WATER REQUIRED 59. Measurement of Water Duty. The duty of water may be variously expressed : a, by the number of acres of land which a second-foot of water will irrigate; b, by the number of acre- feet of water required to irrigate an acre of land; c, in terms of the total volume of water used during the season; or d, in terms of the expenditure of water per linear mile of canal. The duty of water varies primarily with the crop; thus rice requires more than wheat. It varies still more largely with the soil, since sandy requires far more than clayey soil. It varies with the temperature, the precipitation, and with the condition of the ditches, since flat, shallow channels give smaller duties than steeper and deeper ones. Above all, it varies with the skill of the irrigator. In considering the duty of water care should be taken to show whether it is reckoned on the quantity of water entering the head of the canal or the quantity applied to the land, since the losses by seepage, evaporation, etc., in the passage of water through the canal are considerable. Thus, if in a long line of canal the duty is estimated at 150 acres per second-foot, and the losses by seepage and evaporation are 33^ per cent, the duty would be reduced to 100 acres at the point of application. Careful measurements made on various canals in India show the loss of water between their heads and the heads of the dis- tributaries to vary from 20 to 40 per cent. Where duty on dis- charge at canal head was 53 acres, that on its discharge utilized was 72 acres; while the duty of the distributaries on their dis- charge at outlet was 104 acres per second-foot. In a number of experiments conducted in the West to de- termine losses in canals it was found that while the duty at the fields varied from 1.5 to 2.8 acre-feet of water to each acre irri- gated the amount of water used based on measurements at the canal head amounted to from 3.8 to 6.6 acre-feet per acre. In most of these experiments it was found that about 50 per cent of the water entering the canal head was lost by absorption and evaporation before it reached the fields. On the other hand, these losses on the Gage canal, California, which is cement lined, amounted to only 6 per cent. DUTY PER SECOND-FOOT 60. Duty per Second-foot. The duty of water in various portions of the West is a matter of extreme doubt. As recently as in 1883 it was estimated in Colorado to be from 50 to 55 acres per second-foot. In Montana and portions of Colorado the farmers still state the duty as being one miner's inch to the acre, or 38.4 acres per second-foot. Recent experiments show that the duty is rapidly rising, for as land is irrigated through a series of years it becomes more saturated, and as the subsurface water- plane rises the amount of water necessary to the production of crops is diminished. The cultivation of the soil causes it to require less water. The adoption of more careful methods in designing and constructing distributaries and care and experience in handling water increase its duty. The State Engineer of Colorado now accepts 100 acres per second-foot as the duty for that State, varying on the supply at the head from 70 to 190 acres. In Utah, 70 to 300 acres per second-foot is the duty. In Montana it is about 80 acres per second-foot. In the following table the duty of water is given for a few foreign countries and for various portions of the West. These duties cannot be taken as fixed. They are apt to be increased with experience, and in the same State or even in the same neigh- borhood they will differ according as the crops, soil, altitude, and the skill in handling the water vary. TABLE VIII. DUTY OF WATER. (Based on Supply entering Canal Head.) Locality. Duty per Second -foot in Acres. Duty Acre-feet per Acre. Northern India no i co Italy 6c 70 Colorado 80 i 20 4Q Utah. . 60120 6 7 Montana 80100 **-o 4-7 Wyoming 7O 3O J 52 Idaho 60-80 51 New Mexico 60-80 c 6 Southern Arizona lOOICO i 8 San Toaquin Valley, Cal 100150 34 Southern California, surface irrigation ICO 3OO 2 2 " sub-irrigation 300 coo 52 QUANTITY OF WATER REQUIRED The above figures are for duty on supply entering canal head. The duty on the supply utilized will average 20 to 40 per cent greater. The reason for the high duty given for such an arid region as Southern California is because the water there, being valuable, is handled with great care. On the cement lined canals of the United States Reclamation Service in Nevada, Arizona and elsewhere the duty is even greater. 61. Duty for Various Crops. Where great care was taken on an experimental farm in Wyoming in handling water, its duty per second-foot was found to be as high as 94 acres on oats and 230 acres on potatoes. In Montana a duty on oats of 150 acres per second-foot is frequently attained. On beets in California the duty is often 250 to 300 acres, in Utah 200 acres, and in New Mexico 100 acres. In Arizona a duty of 50 acres of peaches per second-foot of water is common practice. At the Montana experiment station Prof. Samuel Fortier found the following duties for various crops : Clover. Peas. Wheat. Barley. Oats. Depth of water applied 1 .02 I. IO 1. 08 .08 1 . 34 Number of applications 2 2 2 I 2 Average head of water, sec. -ft I . c-2 I . "?O i.7< 4.04 i . =50 The average of all the experiments showed 1.2 acre-feet of water used on each acre. 62. Depth of Water required to Soak Soil. Recent experi- ments conducted under the direction of Prof. L. G. Carpenter throw valuable light on the depth of water required for irrigation. It may be generally stated that the experience of all countries indicates that it is impossible to make an irrigation with a depth of less than 3 inches of water on sod ground and 4 to 6 inches on cultivated crops, though under certain adverse conditions of soil and crop as much as 10 inches of water may be required. Experiments conducted in India have shown that a good heavy rain amounting to about 5 J inches soaks into the earth to a depth of from 1 6 to 18 inches. If this amount of water were applied QUANTITY PER SERVICE AND IRRIGATING PERIOD 53 three times in the season, it would be equivalent to a total depth of i6J inches to the crop. 63. Quantity per Service and Irrigating Period. In Colorado alfalfa and clover are irrigated twice in a season, once in May and once in June, to a depth of 6 inches for each period ; wheat and oats are irrigated twice, once in June and once in July, to a depth of 9 and 6 inches respectively. Meadow or native hay requires considerably more water; there are usually two service periods, each of which lasts several days, the water being allowed to run in a small quantity during that time. The first is usually in May, and is about two inches in depth for a week; the second in July or August, of about the same amount; in all from 24 to 30 inches in depth of water are applied. Since the application of water is generally followed by a temporary checking of the growth of the plant, the method preferred in the arid region seems to be to give thorough rather than many irrigations; in other words, to have two ample rather than four to six small services. In general it may be stated that two or three service periods varying in depth from 3 to 6 inches are employed in Colorado, and that the irriga- tion period extends from May to September 123 days. In Utah the practice seems to be to employ a much larger number of service periods, from three to five on grain crops of 2 to 3 inches in depth each, the water running 12 to 15 hours per service period, and the irrigation period extending from June to August inclusive. On vegetables as many as six to ten service periods are employed, each lasting from 3 to 6 hours during June to August inclusive. The irrigating period in the majority of Western States averages from April 15 to August 15, or about 120 days; while the service period varies from 3 to 15 hours in length according to soil and crop, and there are from two to eight such service periods in an irrigating period. In India there are from three to five service periods, making up an irrigating period of from 100 to 130 days' duration. 64. Duty per Acre-foot. Assuming an average depth of 4 inches of water as sufficient to soak the soil thoroughly, this is equivalent to J of an acre-foot per acre. An average crop requires from two to four waterings per season. Assuming 54 QUANTITY OF WATER REQUIRED three as the mean, then at the above rate one acre-foot will be required per season to irrigate an acre. Practice, however, clearly indicates that this theoretic amount is too low. Experi- ments conducted in Wyoming indicate that 12 inches in depth for potatoes to 24 inches in depth for oats are sufficient to mature crops. In Idaho the depth of water generally used is about 24 inches, while in Montana from 15 to 18 inches is believed to be sufficient. These indicate volumes ranging from ij acre-feet in Montana to 2 acre-feet in Wyoming and Idaho, as duties estimated on the amount of water entering the canal heads. Measurements on several canals in Colorado show that from 1 8 to 24 inches in depth of water are required, or from ij to 2 acre-feet per acre. Experiments conducted by Mr. Samuel Fortier in Utah indicate that a depth of 24 inches is required for tomatoes, while potatoes yield abundantly with a depth of 17 inches, onions with a depth of 36 inches, strawberries with 27 inches, and orchards with 12 inches. A recent careful measurement of water duty on mixed crops near Yuma, Arizona, the hottest place in the United States, shows a duty of 5 acre-feet per acre. 65. Linear and Areal Duty. Experiments made in India show that from 6 to 8 second-feet of water should be allowed per linear mile of canal, depending on the area commanded on either side of the canal. On the Soane canal in India a more con- venient unit was employed, it having been discovered that about three-fourths of a second-foot was sufficient for a square mile of gross area. As the net area irrigated, however, is rarely more than two-thirds of the gross area commanded, perhaps about one- half a second-foot is sufficient to irrigate a square mile with the most economic use. On the Reclamation Service projects a more liberal allowance is provided. On the Uncompahgre canal, Colorado, one second-foot at the headgates is allowed for each 80 acres; and on the Interstate canal, Neb.-Wyo., ij second-feet to 100 acres. In estimating the duty of water stored in a reservoir or diverted from a stream, allowance must be made for the losses due to evaporation and absorption in conducting the water to the fields. As this averages 25 to 50 per cent, it follows that where a duty of PERCENTAGE OF WASTE LAND 55 i acre-foot per acre is possible ij to i J acre-feet must be provided at the headgates, and where 2 acre-feet per acre is the duty 2\ acre-feet must be provided. In estimating the total duty of the supply consideration must be given to the area of waste land (Art. 66), which will increase the duty by about 20 per cent. On the Reclamation Service projects liberal allowances of water are provided. For the Salt River project, in a very arid region, a duty of 4 acre-feet is allowed; for the Yuma canals, in the most arid region, 5.5 acre-feet; for the Minidoka canals, Idaho, 4 acre-feet; and for the Interstate canals, Nebraska, 2 acre-feet. 66. Percentage of Waste Land. In every irrigated area but a small percentage of the total area commanded is irrigated in any one season. Some of the land is occupied by roads, farm- houses, or villages. Some is occupied by pasture-lands, which receive sufficient moisture by seepage from adjoining irrigated fields; and some by barnyards, while occasionally fields are allowed to lie idle for a season. It has been observed in India that but two-thirds to four-fifths of the total area commanded are irrigated. On the Soane canal in India, about 500 acres out of every 640 are irrigated. From estimates made in well irri- gated portions of the West it appears that if water is provided for 500 out of every 640 acres, it will be sufficient to supply all the demands of the cultivators. Keeping this in mind, it will be seen that the actual duty of water entering the canal head, when estimated on large areas, is at least 20 per cent greater than the theoretic duty per acre. 67. Tatils, or Rotation in Water Distribution. The water in distributaries can be most economically handled if a system of rotation be employed in admitting it to the heads of the private channels. It is more convenient and economical to use water in as large heads and volumes as possible; in fact, the volumes of water flowing in many small distributaries are so small that, if irrigation were b,eing practised all along its line at the same time, sufficient would not reach the lower end of the distributary to moisten its bed, much less flow over the fields. It is therefore essential in such cases to divide the distributary into a number 56 QUANTITY OF WATER REQUIRED of sections, in each of which the water is permitted to flow with full head for a given period, and the irrigators are compelled to use the water at the time when it is available in their section, be it night or day. This system of irrigating by rotation, or by "tatils" as it is called in India, is of great advantage not only in checking the loss of water in the channels and giving sufficient head to each irrigator to flow his land, but also in teaching economical irrigation to the cultivators and insuring a fair division of water among them. Thus an irrigator who is entitled to but J second- foot of water during an irrigating period of 100 days would find that volume too small to be economically and practically handled; but if he were permitted to use 4 second-feet during 12 days, divided into three tatils or service periods of four days each, he would be able to make a satisfactory and economical use of such a head. These tatils are imposed by regulating the amount admitted to the private channels and the period of time in which it shall enter them. The outlets of these channels may be closed in the first section of the canal for, say, 4 days ; in the second for 3 days ; and this order may be reversed, the period of rotation being such as to vary and equalize the period of closure among the several sections. It is better to impose these systems of rotation on long portions of the distributaries at the same time, since the effect of forcing water down to the tail of the distributaries is then more noticeable. Thus, if the canal be twenty miles in length and all the outlets in the first five miles be closed, those in the second five miles opened, those in the third five miles closed, and those in the fourth five miles opened all at the same time, the effect will be to produce a stronger head and carry the desired amount to all the channels in the last portion of the canal; then for a few days this order may be reversed, and the maximum duty obtained in the remaining portions of the distributaries with- out difficulty. To make such a system effective, rules must be enforced compelling irrigators to accept water when their irrigating heads are open and refusing it to them when their turn has gone by. WORKS OF REFERENCE 57 68. Works of Reference. Duty of Water. BERESFORD, J. S. Duty of Water and Memoranda on Irrigation. Professional Papers, Second Series, No. 212. Roorkee, India. BUCKLEY R. B. Irrigation Works in India and Egypt. E. & F. N. Spon. Lon- don, 1894. CARPENTER, L. G. Third Annual Report on Meterorology and Engineering Con- struction, State Agricultural College of Colorado, 1890. Fort Collins, Colorado. Duty of Water. Bulletin 22, State Agricultural College. Fort Collins, Col., 1893. DEAKIN, ALFRED. Royal Commission on Water Supply. First and Fourth Progress Reports, Irrigation in Western America, Egypt, and Italy. Mel- bourne, 1885. FLYNN, P. J. Irrigation Canals and other Irrigation Works. Denver, Colo., 1892. FOOTE, A. D. Report on Irrigation of Desert Lands in Idaho. New York, 1887. FORTIER, SAMUEL. Water for Irrigation. Bulletin 26, Utah Agricultural Col- lege. Logan, Utah, 1893. HALL, WILLIAM HAM. Report of the State Engineer to Legislature of California. Sacramento, 1880. KING, F. H. Irrigation and Drainage. The Macmillan Co. New York, 1899. MEAD, ELWOOD; FORTIER, SAMUEL; and others. Use and Duty of Water in Irrigation. Bulletin 86, Office of Experiment Station, Dept. of Agriculture, Washington, D. C. NEWELL, F. H. Agriculture by Irrigation. Report of the nth Census, 1890. Washington, D. C., 1894. WILSON, HERBERT M. Irrigation in India. Part II, i2th Annual Report of the U. S. Geological Survey. Washington, D. C., 1891. American Irrigation Engineering. Part II, i3th Annual Report of the U. S. Geological Survey. Washington, D. C., 1892. United States Reclamation Service, Annual Reports. Government Print- ing Office, Washington, D. C. CHAPTER VI FLOW AND MEASUREMENT OF WATER IN OPEN CHANNELS 69. Physical and Chemical Properties of Water. Water is composed of an infinite number of minute particles, each of which has weight and can receive and transmit this in the form of pressure in all directions. The particles composing water move upon and among each other with an inappreciable amount of friction. Water is composed of at least two atomic substances, oxygen and hydrogen, combined in the ratio of one of oxygen to two of hydrogen, the whole forming a molecule of water. These molecules are so fine that it has been estimated that there are from 500 to 5000 in a linear inch. 70. Weight of Water. Water reaches its maximum density at about 39.2 Fahrenheit, and the weight of a cubic foot of dis- tilled water at this temperature is 62.425 pounds; and of a U. S. gallon 8.3799 pounds. Below and above this temperature the weight of a given volume of water decreases. The weight of a cubic foot of ice is 57.2 pounds. At 32 Fahrenheit a cubic foot of distilled water weighs 62.417 pounds, and its weight increases from this to the maximum density above given, from which it decreases to 62.367 pounds at 60 Fahrenheit, and continues to decrease almost uniformly to a weight of 59.837 pounds at a temperature of 212, which is the boiling point of water. Ordi- nary pond, brook, or spring water is heavier than distilled water because of the trifling amounts of salts carried in solution in most fresh waters; while salt water or water laden with sediment is still heavier, according to the amount of soluble or suspended matter in a given volume. 71. Pressure of Water. Each molecule of water is inde- pendently subject to the force of gravity, and therefore has weight. When water is pressed by its own weight or that of any other force, this pressure is transmitted equally in all directions. The 58 AMOUNT OF PRESSURE OF WATER 59 pressure at any point of a volume of water is in proportion to the vertical depth of that point below the surface, and is in- dependent of the breadth of the volume of water. If water be contained in a vessel of any form in which an orifice is made the particles of water at that point are relieved of the resistance of the confining surface, and at once slide on each other and flow out of the orifice with a velocity proportional to its depth below the surface, or to what is known as the "head." The pressure due to a column of water in a vertical tube is directly proportional to its height, and if the column be bent or inclined at any angle the pressure will not be dependent on the length of the crooked confining channel, but on the height of the surface vertically above the lowest part of the column. 72. Amount of Pressure of Water. A cubic foot of water is ordinarily taken as weighing 62.5 pounds, and the pressure per square inch for each vertical foot of depth below the surface of water is about 0.434 pound. By means of the ordinary methods adopted in considering the parallelogram of forces, the pressure of a body of water against an inclined surface at any given point may be determined by representing the depth (or the weight due to the depth at that point) by a line, the length of which bears a certain proportion to the weight, and by resolving this inclined line into its resultant horizontal and vertical components, these latter will then represent the relative horizontal and vertical pressures exerted by the water against that point. To find the total pressure of water on any surface its area in square feet should be multiplied by the vertical depth of its centre of gravity below the water surface in feet, and the total by the weight of one cubic foot of water. Making h = ihe head or depth below the surface, /> = the pressure in pounds at that point, and g the depth of the centre of gravity of the mass of water below the surface, or one-half of h, and the weight of a cubic foot of water being 62.5 pounds, we have p = 62.$h. 73. Centre of Pressure. The force which tends to over- turn or push a surface about a given point is not in the centre of gravity of the body of water, but at two-thirds of the depth 60 FLOW AND MEASUREMENT IN OPEN CHANNELS from the surface to that point, and is known as the centre of hydrostatic pressure, while the j^nire of gravity is at one-half the vertical depth of the point. The total pressure upon a curved surface is proportional to the total length of that surface, but the horizontal effect of this pressure is directly proportional to the vertical projection of the surface. 74. Atmospheric Pressure. The weight of the atmosphere upon the surface of any substance at the level of the sea is about 14.75 pounds per square inch. This quantity is known as an atmosphere, and will sustain a column of water 34.028 feet in height. In other words, the pressure of the atmosphere would raise a column of water to this height. It is on this account that it is possible to raise water by pumping or to cause water to flow through a siphon. The act of pumping or of raising water by a siphon produces a vacuum above the water, and the pressure of the atmosphere forces the water up to fill this vacuum to a height, approximately, of 34 feet at sea level. Ow- ing, however, to friction and other causes, water can never be raised to quite this height ; while at altitudes above the sea level where the atmosphere is lighter, its sustaining power is diminished and the height to which it will force water is diminished propor- tionately. 75. Motion of Water. The motion of water is due to a destruction of the equilibrium among the particles forming its mass, and it is said to "flow" because the action of gravity gen- erates motion and destroys equilibrium. The motion of a falling body is constantly accelerated by the force of gravity in regular mathematical proportion. At the level of the sea a body falling freely in vacuo drops a height of 16.1 feet during the first second of time, its velocity at the end of the first second being 32.2 feet, and it is accelerated by this amount for each succeeding second. It is this quantity which is known as the acceleration of gravity, and which is usually designated by the letter g in hydraulic for- mulas. The velocity v of a body at the end of a given space of time / is equal to the product of time into its acceleration by gravity. Thus, v = gt. It has been shown that the height h, through which the body falls or through which its pressure is FACTORS' AFFECTING FLOW 6l accelerated, is equal to one-half of the gravity, and the heights fallen in any given time are as the squares of the time; hence __, and substituting, transposing, and eliminating, we have 76. Factors affecting Flow. If an open channel be given the smallest possible inclination in one direction, the water con- tained therein will be at once set in motion by the act of gravity, and its particles will fall one over the other in the direction of the inclination until motion or flow in that direction takes place. The effect of the action of gravity to produce motion is dependent on the slope, and this is usually represented by the ratio of the vertical to the horizontal distance; so we have as factors repre- senting the velocity of flow the length of the channel, /, for a vertical fall of any given height, //. The amount of friction offered by the sides of the channel to the flow of water and tending to impede its velocity is one of the important factors, and is de- pendent chiefly on the nature of the bed and sides of the channel, that is, to the lining or surface of the channel against which the water flows, and on the length of wetted perimeter or the sectional area against which the water presses. Other quantities on which the coefficients of flow in channels depend are the hydraulic mean depth, r, which is equal to the area of the cross-section of the water in square feet, A, divided by the wetted perimeter in linear feet, p. A simple formula representing the mean velo- city of flow is ...... (7) m in which i is the sine of the inclination h divided by / in feet; h being the fall of the water surface in the distance /; m is a variable coefficient, which includes most of the minor modifying factors. The value of m varies between .05 for a hydraulic mean radius of .25, to .0298 for a hydraulic mean radius of i, and diminishes constantly thence to a value of .0074 for a hydraulic mean radius of 10 and .002 for a hydraulic mean radius of 25. 77. Formulas of Flow in Open Channels. The formulas for 62 FLOW AND MEASUREMENT IN OPEN CHANNELS finding the mean velocity of flow in open channels have all con- stant coefficients, and are therefore incorrect outside of a small range of dimensions. As a result of experiments on the Missis- sippi by Humphreys and Abbot, and of experiments made in India, Kutter has devised a formula which takes into account the resistance due to the varying quantities n and k, which depend on the nature of the surface of the channel. Bazin made some ex- periments on small canals, from which he devised a formula which has been received with popular favor. This formula is arranged with various constant factors, according to the four grades of roughness of the surface of the channel. Modifications of this formula have been devised by D'Arcy which are still more convenient to use. D'Arcy's formula is I 10002 /\ v = r\ - > W V .08534 + 0.35 in which i equals the fall of water in any distance, / divided by that distance = = the sine of the slope. 78. Kutter J s Formula. The formula which is now most approved for determining the velocities of flow in open channels is Kutter's formula, 1.811 , , , .00281 - + 4I.6+ .00281 MX n - i ) Vr (9) Substituting for the first term of the right-hand factor the letter C, we have Chazy's formula v=CVri=CV~rX\/T. . . . (10) For small channels of less than 20 feet bed width Bazin 's formula gives fair results where the sides and bottom are well built. The coefficients in this formula depend on the nature of the surface of the material and the hydraulic mean depth. The following table, from Flynn's "Flow of Water in Open Channels," gives the value of C for a wide range of earth channels, and will cover nearly everything occurring in ordinary practice. KUTTER'S FORMULA 63 TABLE IX. VALUE OF V IN FEET PER SECOND AND OF C FOR EARTH CHAN- NELS, BY KUTTER'S FORMULA. n = .0225 \/~r in feet. r in. 0.7 I .0 1.8 2 -5 4.0 V C V C V C v C V C 1000 1.17 5i-5 2.01 62.5 4.88 80.3 7.08 89.2 I2 -73 99-9 i2;o 1.04 5i-3 i-79 62.3 4.17 80.3 6.38 89-3 "-43 IOO.2 1667 .85 51.0 i-54 62.1 3-58 80.3 5-54 89- 5 9-95 100.6 2500 .72 50-4 1.25 61.7 2 -95 80.3 4-54 89.8 8.19 101.4 3333 .62 49-8 1.07 61.2 2-54 80.2 3-94 90.1 7.14 102.3 5000 -50 48.9 -87 60.5 2.05 80.3 3-24 90.7 5-92 103-7 7500 .42 47-5 -73 59-4 i-77 80.3 2.78 9i-5 5-'3 106.0 IOOOO -34 46.4 .60 58-5 1.49 80.3 2-33 92.3 4-55 107.9 2OOOO .22 43 - .40 55-7 1.20 80.2 1.70 94-8 3-29 115.0 n = .035 \/~r in feet. 0.7 I.O 1.8 2-5 4-0 V C V C V C V C V C 1000 0.67 29.9 1.19 37-6 2.85 51-6 4.69 59-3 8.76 69.2 1250 .60 29.8 1. 06 37-6 2-51 51.6 4.20 59-4 9.86 69.4 1667 -57 29.6 .92 37-4 2.40 51.6 3-62 59-5 6.84 69.8 2500 .42 29.2 -74 37- 1 1.85 51-6 3-oo 59-7 5-63 70.4 3333 -36 28.9 .64 3 6 -9 1. 60 51-6 2.60 59-9 4.92 71.0 5000 .29 28.3 5 1 3 6 -4 1.30 51-6 2.IO 60.4 4.08 72.2 7500 .24 27.7 .42 35-8 I. II 51-6 I. 80 60.9 3-55 73-9 IOOOO .19 27.1 -35 35-3 -93 51-6 1.50 60.5 3.02 75-4 20000 - r 3 25-4 .24 33-8 -65 51-5 I.IO 63-1 2.28 80.6 This table is arranged with two different values for the factor n which are dependent on different qualities of surface in the channel. The accuracy of Kutter's formula depends chiefly on the selection of the coefficient of roughness n, and experience is required in order to give the right value to this coefficient. In order to provide for the future deterioration of the channel surface by the growth of weeds or its abrasion, it is well to select a high value for n. The following are some of the values of n for dif- 64 FLOW AND MEASUREMENT IN OPEN CHANNELS ferent materials as derived from Jackson, Hering, Kutter, and others : n = .009 for well-planed timber; n = .oi for plaster in cement, glazed iron pipes, and glazed stone- ware pipes ; n = .oi2 for wooden pipe, rough plank flumes, concrete, and re- inforced concrete; ^ = .013 to .017 for ashlar masonry, tuberculated iron pipes, and brickwork according to the smoothness of the surface and its condition; about .014 for good ashlar or brick and .018 for rubble masonry; n = .oi6 for riveted steel conduits; n=.o2 for rubble in cement and coarse rubble of nearly all kinds; also for coarse gravel carefully laid and rammed, or for rough rubble where the interstices have become filled with silt; ^ = .0225 in good earth canals; w = .o25 to .03 in canals from those having tolerably uniform cross-section and slopes to those which are in rather bad order, and have some stones and weeds obstructing the channels ; ^ = .035 to -5 f rom canals and rivers with earth beds in bad order and obstructed by stones, etc., to torrents covered with all varieties of detritus, and overflowed tree-covered banks. As an indication of the extent to which the value of n affects the velocity of the discharge of channels, let us take an example in which n = 0.02 2 5. A bed width of 10 feet, depth of 2 feet, and side slopes of i to i, with a grade of 8 feet per mile, gives a velocity of 3.32 feet per second and a discharge of 79.07 second-feet. For the same channel with a value of ^ = .035 the velocity is 2.05 feet per second and the discharge 49.2 second-feet; thus showing that with the better channel the discharge is 60 per cent greater than with the inferior channel. 79. Tables for Use with Kutter's Formula. Tables X to XIV inclusive are in large part derived by condensation from Flynn's tables, and greatly facilitate the various computations DISCHARGE OF STREAMS AND VELOCITIES of flow in open channels, in connection with Chazy's adaptation of Kutter's formulas v = C\/ri and Q = Av. Table X gives the sine of the inclination i ' = in feet, and also \/ i for given grades and slopes from one-fourth of a foot per mile to thirty feet per mile. Tables XI, XII, and XIII give, respectively, the area A in square feet, the hydraulic mean depth r in feet, and the \/r for rectangular channels, and also for trape- TABLE X. GRADES, SLOPES, AND VALUES OF i AND \/T FOR USE IN KUTTER'S FORMULA v Grade in Feet per Mile. Slope i in i VT Grade in Feet per Mile. Slope i in 1 v~r - 2 5 2II2O .000047 .0069 10 528 .001894 -0435 50 10.560 .000094 .0097 II 444 .002083 .0456 75 7040 .000142 .0119 12 440 .002273 .0477 i 5280 .000189 - OI 37 13 406 .002462 .0496 !- 2 5 4224 .000236 .0154 14 377 .002651 -0515 i-5 3520 .000284 .0168 15 35 2 .002841 -0533 i-75 3 OI 7 -000331 .0182 16 330 .003030 -0550 2 2640 .000378 .0194 '7 3 11 .003219 .0567 2-25 2-347 .000426 .0206 18 293 .003409 .0584 2-5 2112 .000473 .0217 19 278 .003598 -0599 2-75 IQ20 .000521 .0228 20 264 .003788 .0615 3 1760 .000568 -0238 21 251 .003977 .0630 3-25 1625 .000615 .0248 22 240 .004166 .0645 3-5 1508 .000663 .0257 2 3 229 .004356 .0660 3-75 1408 .000710 .0266 24 220 -004545 .0674 4 1320 .000757 .0275 25 211 -004735 .0688 5 1056 .000947 .0307 26 203 .004924 .0702 6 880 .001136 -337 27 195 -005113 -0715 7 754-3 .001325 .0364 28 188 -005303 .0728 8 660 .001515 .0389 29 182 .005492 .0741 9 586.6 .001704 .0413 3 176 .005682 -0754 zoidal channels having side slopes of i on i and i on ij, corre- sponding to depths of from i to 10 feet and bed widths of from 3 to 100 feet. Table XIV gives the coefficients of roughness C for different values of n and for values of r from o.i to 10, and of i, from .0001 to .01. 80. Discharge of Streams and Velocities of Flow. The quantity of discharge of a canal or river, Q, in second-feet is obtained by multiplying its velocity, v, in feet per second into 5 66 FLOW AND MEASUREMENT IN OPEN CHANNELS the cross-sectional area, A, of the channel in square feet. Alge- braically expressed, Q=Av, (11) or, substituting for v its value from equation (10), Q=CXAx\/rXVT, (12) Since the discharge of an open channel depends primarily on a knowledge of its mean velocity, it will be well to consider the relation of this to the velocities in other portions of the channel. In any open channel the film of water in contact with the open air has a velocity which is a trifle slower than that in the centre TABLE XI. VALUES OF A IN SQUARE FEET, r IN FEET, AND \/r FOR CHANNELS HAVING VERTICAL SIDES. For Use in Kutter's Formula v = C \'' ri and Q = Av. Depth in Feet. Bed -width, 3 Feet. Bed -width, 5 Feet. Bed-width, 10 Feet. A r \/7 A r \/7 A r V7 I i-5 2 2 -5 3 3-5 4 4-5 5 3 4 4-5 5 I' 5 6-5 7 l- s 9 10 3 4-50 6 7-5 9 .600 -75 -857 -937 9 -774 .866 .926 .967 i 5 7-5 10 I2 -5 i5 17-5 20 .714 -937 i. in 1.250 1.364 1.458 1-538 -845 .968 1.054 1.118 1.168 1.208 1.241 20 25 3 35 40 45 50 1.429 1.666 1-875 2.058 2.222 2.367 2-5 1-195 .290 -396 -434 .490 -538 .581 Bed-width, 20 Feet. Bed-width, 40 Feet. Bed-width, 60 Feet. A r V7 A r VT A r V7 60 80 90 IOC no 120 2.307 2.857 3- I0 5 3-333 3-553 3-750 ^ 8 .690 .762 .825 -885 -937 160 1 80 200 220 24O 3-333 3.672 4 4-314 4.614 1.826 1.916 2 2.077 2.148 240 270 3 00 330 360 390 420 45 480 540 600 3-529 3-913 4.286 4.646 5 5-343 5-676 6 6.316 6.923 7-5oo 1.878 1.978 2.073 2-155 2.236 2-311 2-382 2.450 2 -S I 3 2.963 2-738 280 5.180 2.276 320 3 60 5-7 r 4 6.207 2-394 2.491 DISCHARGE QF STREAMS AND VELOCITIES 6 7 TABLE XII. VALUES OF A IN SQUARE FEET, f IN FEET, AND CHANNELS HAVING SIDE SLOPES OF I ON I. For Use in Kutter's Formula v = C \/ri and Q = Av. FOR Depth in Feet. Bed -width, 3 Feet. Bed -width, 5 Feet. Bed-width, 10 Feet. A r v/7 A r V7 A r VT I i-5 2 2-5 3 3-5 4 4-5 5 2 3 3-5 4 4-5 5 5-5 6 8 4 5 6 6-5 7 I' 5 8-5 9 10 ii 12 4 6-75 10 13-75 18 .686 -932 I-I55 1-365 1-567 .828 .965 r -75 1.168 1.252 6 9-75 14 ' 18-75 24 29-75 36 .766 -054 -314 -553 .780 -997 2.207 -875 .027 .147 .246 -334 -413 .486 24 31-25 37-00 47-25 56 65- 2 5 75 1-533 1.831 2. IIO 2-375 2.628 2.871 3-!07 -238 -353 -452 -541 .621 .694 763 Bed-width, 15 Feet. Bed-width, 20 Feet. Bed-width, 40 Feet. A r VT A r v^7 A r x/7 34 54 6 4-75 76 87-75 IOO 1.646 2.300 2.601 2.888 3- l6 5 3-43 1 .283 .516 .612 .700 -779 -852 69 96 110.25 "5 140.25 156 2.422 3.066 3-369 3.661 3-944 4.220 i-556 i-75i 1-835 1-913 1.986 2.054 176 200.25 225 250.25 276 329 384 3-43 1 3-798 4-155 4-504 4-844 5-5oi 6.132 1.852 1.949 2.038 2.122 2.201 2-343 2-476 126 3-941 1.985 Bed-width, 60 Feet. Bed-width, 80 Feet. Bed-width, 100 Feet. A r \n A r vT A r VT 2 5 6 325 396 43 2 -25 469 506.25 544 582.25 621 700 3-590 4-384 5-145 5-515 5-877 6.234 6.584 6.928 7.267 7.929 1.895 2.095 2.268 2.348 2.424 2-497 2.566 2.632 2.696 2.816 425 5i6 562.25 609 656.25 74 752-25 80 1 900 IOOI 4-5 J 4 5-321 5-715 6.102 6.484 6.860 7.230 7-595 8.312 9.009 2.125 2.307 2.391 2.470 2-546 2.619 2.689 2-756 2.883 3-oor 525 636 692.25 749 806.25 864 922-25 981 I IOO 1221 1344 4.600 5-437 5.848 6-252 6.652 7.046 7-435 7-8i9 8-575 9-3J3 10.03 2-145 2-331 2.418 2.500 2-579 2-654 2.726 2.796 2.928 3-051 3- l6 7 68 FLOW AND MEASUREMENTS IN OPEN CHANNELS of the mass owing to the retarding effect of friction against the atmosphere. This velocity is known as the surface velocity. The velocities of the films adjacent to the sides and bottom of the channel are retarded to a still greater extent by the roughness of the same, and in direct proportion to this roughness. It has been TABLE XIII. VALUES OF A IN SQUARE FEET, r IN FEET, AND \ff FOR CHANNELS HAVING SIDE SLOPES OF I ON ij. For Use in Kutter's Formula v = C\/ri and Q = Av . Depth in Feet. Bed -width, 3 Feet. Bed-width, 5 Feet. Bed-width, 10 Feet. A r V7 A r V7 A r VT I 1-5 2 2-5 3 3-5 4 4-5 5 t j 3 4 4-5 5 5 6' 5 6-5 7 7-5 8 9 10 4-5 7.87 12 16.87 22.50 .681 -935 i-i75 1-405 1.628 -83 -97 i. 08 1.19 1.28 6-5 10.87 16 21.87 28.5 35-87 44 -755 1.045 1.310 1.560 1.802 2.036 2.266 .87 i. 02 -15 -25 -34 -43 -5 1 26 34-375 43-5 53-375 64 73-375 87-5 1.510 1.807 2.090 2-358 2.620 2.873 3-I2I - 2 3 -34 -44 -54 .62 .70 -77 Bed-width, 20 Feet. Bed-width, 40 Feet. Bed-width, 60 Feet. A r x/7 A r \/7 A r V7 73-5 104 120.37 137-5 155-37 J 74 2.386 3.021 3-33 2 3-6i5 3.901 4.179 -54 -73 .82 .90 -97 2.04 184 210.37 237-50 265-37 294 323-4 353-5 3-399 3-742 4.094 4-435 4.770 5-097 5-4i8 1.84 i-93 2.03 2. II 2.18 2.26 2-33 264 300.37 337-5 375-37 414 453-37 493-50 534-37 576 661.50 750 3-547 3-94i 4-325 4.702 5-07 1 5-434 5-789 6.139 6.483 7-*55 7.808 1.88 1.99 2.08 2.17 2.25 2-33 2.40 2-47 2-54 2.67 2-79 416 481.5 6.043 6.646 2.46' 2.58 found that in a channel of trapezoidal cross-section, with an average depth to width, the film of water having a mean velocity of the entire channel is located in the centre of the channel and at a point about one-third of the depth below the surface. DISCHARGE OF STREAMS AND VELOCITIES 6 9 TABLE XIV. VALUES OF C FOR GIVEN SLOPES, I, AND HYDRAULIC MEAN RADII, f, IN FEET. r Coefficients of Roughness for n = .009 .OIO .012 .015 .020 .025 .030 035 Feet. C C C C C C C C .1 no 95 74 54 36 27 21 17 .2 130 114 90 67 46 34 27 22 -4 133 107 82 57 44 35 29 Slope f=.oi = .6 162 U3 116 90 64 49 39 33 i in 100 = .8 i 170 175 156 123 128 95 99 68 72 43 45 II 2 191 171 142 112 83 66 55 46 52.8 feet per mile. 3 199 179 149 119 89 71 59 4 204 184 154 "3 93 76 55 6 210 190 160 129 99 81 68 59 10 217 196 166 136 105 86 74 65 .i no 94 73 54 36 27 21 17 .2 129 "3 89 66 45 34 27 22 Slope i= .001 = 4 .6 161 142 "5 80 88 56 ti 34 39 28 32 i in 1000 = .8 i 169 175 155 122 127 94 99 7i S 2 56 42 45 II 2 191 171 142 112 83 66 54 4 6 5.28 feet per mile. 3 199 179 149 119 89 71 59 51 4 204 184 154 124 93 75 54 6 211 190 l6o 130 99 81 68 59 10 218 197 I6 7 136 105 87 74 65 .i 104 89 6 9 5 34 25 19 16 .2 126 no 87 65 44 32 25 21 -4 148 129 104 79 55 42 33 2 7 Slope *=.ooo4= .6 157 140 "3 8 7 62 47 38 31 .8 1 66 148 121 93 67 42 35 i in 2500= i 172 154 125 98 70 55 45 37 2 190 170 141 112 83 65 54 45 2. 1 1 feet per mile. 3 199 179 149 119 89 71 59 4 204 184 124 94 76 63 55 6 211 191 161 130 99 81 69 60 10 219 199 168 138 107 88 75 66 .2 76 57 39 29 2 3 19 4 ... 95 72 5 38 25 .6 105 81 57 44 35 3 Slope z=.oooi = .8 ... ... 114 88 63 48 39 33 i ... ... 120 93 67 52 42 35 i in 10,000= 2 ... 138 109 81 64 53 45 3 ... ... 149 119 89 71 59 51 .528 feet per mile. 4 ... ... I2 5 94 76 64 55 6 ... ^6 4 IO2 84 71 61 10 J 74 J 43 III 92 78 69 15 ... ... 181 150 118 98 85 75 70 FLOW AND MEASUREMENT IN OPEN CHANNELS 81. Surface and Mean Velocities. The surface velocity is that which is most easily obtained by simple methods. Numer- ous experiments have been made by Du Buat, Francis, Brunning, Humphrey and Abbott, and others, to obtain the ratio of the mean to the surface velocity. From these it has been found that this ratio varies chiefly between ^ = .7807 and v = .g2oV, in which v= the mean velocity of the entire cross-section of the channel and V= its central or maximum surface velocity. This ratio varies with the section of the channel and the roughness of its sides, as well as with the depth. It is found that the ratio of v to V should be at a maximum when the breadth equals twice the depth, also, for several sections, for that which is largest. When breadth is equal to three times the depth, v=.giV', when breadth is equal to five times the depth, ?; = .88F; when breadth is equal to eight times the depth, ^ = .837; in flood work, ^ = .90 to .957. 82. Measuring or Gauging Stream Velocities. One of the simplest methods of gauging the velocity of a stream, but one which does not give the most accurate results, is by means of simple wooden floats or bottles, or some similar contrivance, thrown into the centre of the stream and timed for a given dis- tance. For convenience 100 feet may be measured off on the bank and the time of the float ascertained in passing over this dis- tance. For increased accuracy several passings of the float over this distance should be measured, or, better still, the time of pass- ing of floats over several different lengths of 100 feet should be determined. The mean of these observations will give the central or maximum surface velocity, which multiplied by the proper ratio above will give the mean velocity v. The mean surface velocity may be obtained by throwing in a number of floats on different portions of the surface of the stream and timing their passage over a fixed distance. The resulting velocity per second multiplied by .8 will give approximately the mean velocity of the entire stream cross-section. The velocity of a stream may be ascertained with still greater accuracy by determining the mean velocity, not of the surface as above, but of the entire body of the stream, by timing upright rods so weighted that their bottoms shall float within a few inches MEASURING OR GAUGING STREAM VELOCITIES 71 FIG. 4. Price Electric and Acoustic Current Meters. 72 FLOW AND MEASUREMENT IN OPEN CHANNELS of the bed of the channel. These rods may be either of wood or of tin, of uniform size, and may be jointed so as to be of con- venient use in different depths of water. In using the Pitot tube the stream should be cross-sectioned as in other velocity deter- minations, and the mean velocities may then be ascertained by the tube for various sections in the channel. A curious but well-known fact concerning rivers in great flood is that the water surface near the center of the channel is curved convexly upward and is considerably higher than near the stream banks. This fact should be taken into account in estimating the discharge of a stream in flood if the gauge height is measured near the shore. 83. Current Meters. Current meters are mechanical con- trivances so arranged that by lowering them into a stream the FIG. 5. Haskell Current Meter. velocity of its current can be ascertained with accuracy by a direct reading of the number of revolutions of a wheel, and a comparison of this with a table of corresponding velocities. Various forms of current meters have been designed and used, the three general classes being the direct-recording meter, in which the number of revolutions is indicated on a series of small gear-wheels driven directly by a cog-and-vane wheel; the electric meter, in which the counting is done by a simple make-and- break circuit, the registering contrivance being placed at any desired distance from the meter; and the acoustic meter, in which counting is done by hearing through an ear-tube the clicks made by the revolutions of a wheel and counting the same. Of electric meters, the Haskell Meter (Fig. 5) is strongly CURRENT METERS 73 made, simple and reliable, and therefore especially adapted to work in large rivers. This meter is not so good for very high velocities as that next described, as the rapidity of revolution is so great as to make counting difficult, though it is sometimes provided with two heads of different pitch and rating for low and high velocities. The electric meter which has been found to work most satis- factorily under nearly all conditions of depth and velocity by the hydrographers of the U. S. Geological Survey and U. S. Engineer Corps is the small Price electric-current meter (Fig. 4). It is very accurate for streams of nearly any velocity, and is practically standard with both organizations. Each revolution of the wheel is indicated by a sounder, consisting of a telephone receiver excited by a small battery cell. Two small insulated wires, attached to the stem and to the contact spring in the head, are connected with the sounder through the suspending cable. The Price acoustic current meter is a modification of the Price electric meter. It is especially desirable for its portabil- ity and ease of handling as it weighs but little over a pound. In very shallow streams it gives the most accurate re- sults of ( any meter, and is held at the proper depth by a metal rod in the hands of the observer. It is designed especially to stand hard knocks which may be re- ceived in turbid irrigation waters, and can be used in high velocities, as only each tenth revolution is counted. Its head, like that of the electric meter, consists (Fig. 6), of a strong wheel composed of six conical-shaped cups, which revolve in a horizontal plane; its bearings run in two cups holding air and oil in such manner as entirely to exclude water or gritty matter. Above the upper bearing is a small air-chamber, into which the shaft of the wheel extends. The water cannot rise into this air- chamber, and in it is a small worm-gear on the shaft, turning a FIG. 6. Price Acoustic Current Meter. 74 FLOW AND MEASUREMENT IN OPEN CHANNELS wheel with twenty teeth. This wheel carries a pin which at every tenth revolution of the shaft trips a small hammer against the diaphragm forming the top of the air-chamber, and the sound produced by the striking hammer is transmitted by the hollow plunger-rod through a connecting rubber tube to the ear of the observer by an ear-piece. The plunger-rod is in 2- foot lengths, and is graduated to feet and tenths of feet, thus rendering it serviceable as a sounding or gauging rod. 84. Gauging Stations. The first operation in making a careful gauging of velocity by means of a current meter is the choosing of a good station. This consists in finding some point on the course of the stream where its bed and banks are nearly permanent, the current of moderate velocity, and the cross- sections are uniform for over 200 feet above and below the gaug- ing station. At this point a wire should be stretched across the stream and tagged with marks placed every 5, 10, or 20 feet apart, according to the width of the stream. An inclined gauge- rod is firmly set into the stream at some point where it can be easily reached for reading. It should not be less than 4 by 4 inches and marked for feet and tenths of vertical depth. The gauge heights are recorded through a long period of time in order that variations in the velocity and discharge may be had for different flood heights. Fluctuations in the heights of streams may be measured with even more accuracy than can be obtained by the readings of a gauge-rod as above described by using a nilometer, which is a self-recording gauge. The chief objection to the use of this instrument is that its maintenance requires the attention of a person of considerable mechanical skill in order that it may be kept in proper order. There are three general forms of nilo- meter employed by the hydrographers of the United States Geo- logical Survey. These have horizontal recording cylinders, vertical recording cylinders, and vertical record disks. All of these devices are driven by clockwork and are designed to run a week before renewal of recording paper. The record of stream height by the nilometer is on a scale less than the actual range of the water, and the recording pencil is connected by USE OF THE CURRENT METER 75 a suitable reducing device with a float which rises or falls with the stream. This float is usually placed in a small well near the stream-bank, its bottom communicating with the stream-bed by a pipe of such size as will not become readily clogged. The fluctuations of the water in this pipe correspond with those in the stream and turn the recording wheel through the agency of a cord wound around the wheel and having its lower end attached to the float. 85. Use of the Current Meter. The current meter may be conveniently used either from a boat attached to a wire cable FIG. 7. Cable Station and Section of River. strung a little above the tagged wire, or from a bridge which does not impede the channel so as to make currents or eddies in the water. In using the acoustic meter the gauger holds it in his hands by the rod, and inserting it in the water at any desired depth allows it to register for a certain number of seconds. In obtaining the mean velocity of the stream he plunges it slowly up and down from the bottom of the stream to its surface a few times for a given length of time at each section marked on the tagged wire, and in this way gets the mean velocity of each section. The area of this section is of course already ascertained, by a cross-section made by measurement or sounding of the stream, and the mean velocity multiplied into the area of each section gives the discharge at that point. Care must be taken to hold 76 FLOW AND MEASUREMENT IN OPEN CHANNELS the rod vertically, as any inclination of the meter materially affects its record. In using the electric meter it is inserted in the same manner for moderately shallow streams, but in deep flood streams it is suspended by a wire and a very heavy weight is attached to its bottom to cause it to sink vertically. 86. Rating the Meter. Before the results can be obtained each meter must be rated ; that is, the relation between the num- ber of revolutions of the wheel and the velocity of water must be ascertained. This is usually done by drawing the meter through quiet water over a course the length of which is known, and noting the time. From the observations thus made the rating is determined either by formula or by graphic solution. The distance through which the meter is drawn divided by the time gives the rate of motion or velocity of the meter through the water. The number of revolutions of the wheel divided by the time gives the rate of motion of the wheel. The ratio of these two is the coefficient by which the registrations are trans- formed into velocity of the current. This is not a constant. Taking the number of registrations per second as abscissae repre- sented by x, and the velocity in feet per second as ordinates represented by y, we get the equation y = ax + fr, in which a and b are constants for the given instrument. In determining the rating of the meter graphically, the values of x and y gotten directly from the instrument are plotted as co-ordinates, using the revolutions per second as abscissae and the speed per second as ordinates. In this way a series of points are obtained through which a connecting line called a rating- curve is drawn. From this the coefficient of velocity can be read off corresponding to one, two, or any number of revolutions per second. At each rate of speed of the meter there is a different coefficient of velocity. Three or four of these for average varia- tions in velocities may be used in getting the true velocity from the meter record. 87. Rating the Station. After daily readings of the gauge height of the water have been taken at the station for some time, and the velocity measured by means of the meter at different MEASURING WEIRS 77 heights of stream, the results should be plotted on cross-section paper, with the gauge heights as ordinates and the discharges (obtained by multiplying the velocities into the cross-section) as abscissas. These points generally lie in such a direction that a line drawn through them gives nearly half a parabolic curve and represents the discharge for different heights. Having once plotted this line it becomes possible to determine the dis- charge of the stream at any time by knowing the height of the water from the gauge-rod. 88. Measuring Weirs. The method of measuring discharge which is most popular among the irrigators because of its simpli- city and accuracy is by means of weirs. This method is best suited to streams and canals of moderate size. Among the ad- vantages of the weir as a measuring device are its simple con- struction, accuracy, cheapness, and ease of operation. Its results are easily interpreted by use of tables; it gives quantities of flow in second-feet directly; it is not necessary to maintain a constant head above it; and it causes a trifling loss of head. Where the contraction is complete its coefficient remains constant, and the Francis formula gives the discharge with errors not exceeding one-half of one per cent for depths of water vary- ing between 3 and 24 inches, providing the length of the weir is not less than three or four times the depth of the water flowing over it. There are two classes of weirs, i, sharp-crested or measuring weirs and 2, broad-crested weirs or overflow dams. The three forms of measuring weirs which are most popular are i, the rectangular weir with vertical sides, 2, the trapezoidal and 3, V weirs, of which the latter two have inclined sides with slopes of about one-fourth horizontal to one vertical. 89. Rectangular Measuring Weir. The measuring weir (Fig. 8) should be placed at right angles to the stream, with its up-stream face in a vertical plane. The crest and sides should be chamfered so as to slope downward on the lower side with an angle of not less than 30, while the crest should be practically horizontal and the ends vertical. The dimensions of the notch should be sufficient to carry the entire stream and yet leave the 7 8 FLOW AND MEASUREMENT IN OPEN CHANNELS depth of water on the crest not less than five inches. The sec- tional area of the jet should not exceed one-fifth that of the approaching stream. In order that the proper proportion of the area of the notch to that of the jet shall be maintained, central FIG. 8. Rectangular Measuring Weir. contractions may be introduced, dividing the weir crest into several orifices. 90. Francis* Formulas. The form of equation indicated by theory for the discharge of a weir is Q = Av; ........ (ii) or, substituting for the mean velocity v of a given film its value \/2g/, and for A the area, its equivalent / X h, we get Q = lXhX$V^>h, ...... (13) which formula may be transposed so as to become where / is the effective length of the weir in feet, and h the depth in feet of water flowing over it. Because of the downward curve of the water after passing over the weir, this height h must be measured at some distance above the weir, in order to be free from its influence. The reduction of volume by the crest con- traction can be compensated for by the coefficient m, and insert- ing this factor in formula (14) we have Q = $mV^>lh*. / . ,4,, : -.; - - (15) The factors \m and V~2g are constants, and representing them by c we can substitute it in the formula as a coefficient. This is the coefficient which was determined to be equal to 3.33 by Mr. J. B. Francis' experiments, and substituting this value in equation (15) we get CONDITIONS OF USING RETANGULAR WEIRS 79 Owing to this falling away of the surface at the crest and to the contraction at the ends, if /' be the effective length of the weir, one end contraction makes /' = (/ o.i/z), and any number of end contractions make /' = (/ o.inh). Hence .... (17) which is Francis' formula. 91. Conditions of using Rectangular Weir. If the weir be placed so as to meet the following conditions, formulas (16) and (17) will give the best results. These conditions are: that the water shall not exceed 24 or be less than 4 inches in depth; that the depth on the crest shall not exceed one-third the length of the weir; that there shall be complete contraction and free discharge; and that the water shall approach without perceptible velocity or cross-currents. To obtain these conditions the dis- tance from the side walls to the weir opening should be at least equal to twice the depth on the weir; and the distance of the crest above the bottom of the channel should be at least twice the depth of water flowing over it. Air should have free access under the falling water, and the approaching channel should be at least seven times larger than the weir opening. The ap- proaching channel should be straight and of uniform cross- section. The weir should be erected in a plane at right angles to the stream and perpendicular to its bed, and the edges of the opening should be sharp up-stream and cut away down-stream. 92. Trapezoidal Weirs. As a result of experiments made in Italy in 1886 by Cippoletti, he adopted a trapezoidal weir the sides of which have an inclination of one-fourth horizontal to one vertical. This is based on the theory that the effective length / of a rectangular weir being less than its true length ow- ing to contraction, if the area of the weir be increased in propor- tion to its depth (since contraction increases in this ratio) and so as to balance the loss due to contraction, the flow through the weir will remain the same as though the weir were rectangular without contraction. The conditions called for in placing a rectangular weir must be nearly fulfilled with a trapezoidal weir, but the distance of the sill of the weir from the bottom of the 80 FLOW AND MEASUREMENT IN OPEN CHANNELS canal must be at least three times the depth of the weir, and its length must be at least three times the depth of the water flowing over it. In using this form of weir the equation becomes <2= 3-3W& (18) This weir seems to possess some excellent qualities, the chief difficulty in connection with it being the same as arises in using the rectangular weir, namely, that where silt-laden water is employed this may fill up above the front board of the weir. This weir (Fig. 73) may be used as a divisor, and for fairness of measurement is especially adapted to use on irrigation canals. In using a triangular weir a convenient formula has been found to be the following : Q= 2.$4th*, (19) in which t is the tangent of half the angle in the notch of the triangle. If the triangle be right-angled, this formula becomes <2=2. 54 /*% . (20) which is one of the simplest formulas that can be used, and gives excellent results on small streams. 93. Weir Gauge Heights. In order to determine the depth of water flowing over the weir a post should be set in the stream a short distance above it, and on this a gauge rod suitably marked should be attached. For very exact measurements a hook gauge has been employed, which consists of a hook attached to a sliding rule fastened or hung so that its point shall be below the surface of the water. By turning a tangent screw the hook can be raised until it is exactly level with the surface, thus giving an accurate measurement of the depth of water. 94. Tables of Weir Discharge. Tables XV and XVI are taken from Prof. L. G. Carpenter's instructive bulletin on water measurement. These tables give directly the discharge of rect- angular and trapezoidal weirs of given lengths and for given depths. 95. Broad-Crested Weirs. The results of various experi- ments to determine coefficients of discharge over broad-crested weirs have been assembled by Mr. R. E. Horton. These show BROAD-CRESTED WEIRS 8l TABLE XV. DISCHARGE OVER RECTANGULAR WEIRS OF VARIOUS LENGTHS AND WITH VARIOUS DEPTHS OF WATER, WITH AND WITHOUT CONTRACTION. Formula, Q = 3.33$ (/ o.2/z)/*2. DISCHARGE IN CUBIC FEET PER SECOND. Depth of Water on Correction to Crest. With Two Complete Contractions. be ADDED to each of the preceding to give dis- In In charge with inches. feet. /=! ft. /=i-5 f 1=2 ft. / = 3 ft. / = sft. /=ioft. NO contrac- tion. 0.3 .025 0133 .0200 .O276 .0400 .0677 133 .0000 0.6 .050 .0369 0556 0743 .1116 .1863 3726 .0004 0.9 075 .0674 .1015 .1350 . 2040 .3410 .6830 .0010 I .2 . i .1033 1550 .2078 3132 5240 I.05I9 .0021 i -5 125 .1438 2175 .2912 4385 .7332 I-4695 .0037 1.8 IS .1879 2847 .38l6 5743 .9627 1 . 93 1 2 .0058 2 . I 175 2355 3575 4795 7235 I. 2115 2-43I5 -0085 2-4 . 2 .2861 4352 5843 .8824 1.4787 2.9690 .0119 2.7 .225 3399 .5177 .6956 1.0513 1.7627 3-5412 .0160 3-o 25 3959 .6042 .8126 1.2293 2 .O227 4- 1462 .0208 3-8 275 4543 .6946 9350 I.4I57 2-3771 4 - 7803 .0264 3-6 3 5149 .7287 .0725 i .6103 2-7057 5-4441 .0328 3-9 325 5775 .8863 1952 i .8129 3.0483 6. 1368 .0401 4-2 35 .6420 .9871 3423 2 .O226 3.4032 6.8547 -0483 4-5 375 7079 1.0905 4732 2.2385 3-769I 7-5956 0574 4.8 4 .1974 .6160 2.4623 4.1489 8.3655 .0674 5-i 425 .3070 .7689 2 . 6926 4-5400 9-1585 0785 5 -4 45 .4189 .9221 2 .9874 4 . 9410 9 . 9725 OQOC 5-7 475 5333 .0790 3.1703 5-3529 10.8994 . wyw^ .1036 6.0 .5 .6500 2392 3.4177 5-7743 II .6672 .1178 6.3 525 .7689 .4029 3-6709 6.2069 12.5469 1331 6.6 55 .8899 .5698 3-9295 6.6489 13 .4474 .1496 6.9 575 .0129 7395 4.1928 7-0995 14-3658 .1671 7-2 .6 .1381 2 .9128 4.4621 7-5607 15-3072 .1859 7-5 .625 . 2646 3.0881 4.7351 8.0291 16.2641 2059 7-8 65 3929 3.2663 5-0130 8.5064 17.2399 .2271 8.1 675 5234 3.3478 5-2965 8-9939 18.2374 .2496 8.4 .7 3 63 13 5 5536 9.4882 19 . 2497 2733 8.7 725 3 .8170 5 7747 9 . 9901 20.2786 2084. 9 75 4 . 0052 6 . i 702 10 . 5002 21 .3252 . - u<^4 .3248 9 -3 775 4 . I 06 I 6 . 4704 i i . 0190 22 . 39O5 7 r 2C 9.6 .8 4 .3884 6 . 7734 I I CA14 23 .4684 J J *5 .3816 9 .9 .825 A c8^^ 7 . 08 i o x x j4,54 I 2 . 0764 24 5649 .4121 IO . 2 85 ** jjj A. ?8o6 TO AT i C 2C 6?nr> 10 . 5 ^875 4 . youu 4O7O2 7 .3929 77O7 C * * U * 3 5 13 . l64 ^5 * u/y u 26 . 8056 444O All A 10.8 n yyy* /**/ J 8 02 <7 T -2 T T TT 4 / /^ 5 I 2"l 1 1 . i y 9 2 5 8 ^4.7^ 1 3 7 1/7 T A 277O 27 * 9477 2O T C\A A !s886 11.4 i , - 34 / j 8 672? A 4 * / / V T 1 RA c T ^y . L 044 e86j. it. 7 V5 975 O . Uy ^5 9.0012 14 "45 * 15.4192 3I-4642 5 OW 4- .6258 82 FLOW AND MEASUREMENT IN OPEN CHANNELS TABLE XV. Continued. Depth of Water on Crest. DISCHARGE IN CUBIC FEET PER SECOND. With Two Complete Contractions. Correction to be ADDED to each of the preceding to give discharge with NO con- traction. In Inches. In feet. / = 3 feet. /=5feet. l=io feet. 12.0 12.3 12.6 12.9 13-2 13-5 13-8 14.1 14.4 14-7 iS-o 15-3 15-6 iS-9 16.2 16.5 16.8 17.1 17-4 17-7 18. 18.3 18.6 18.9 19.2 19-5 19 8 20. I 20.4 20.7 21 21-3 21.6 21.9 22 . 2 22.S 22.8 23-1 23 -4 23-7 24 27 3 36 o 025 05 075 i 125 150 i75 2 225 25 275 3 325 35 375 4 425 45 475 5 525 55 575 .6 .625 65 675 7 725 75 775 .8 .825 .85 .875 9 925 95 975 25 50 3 9-3333 9.6679 10.0058 10.3471 10.6890 11.0370 11.3866 11.7396 12.0935 12.4507 12 .8l03 13-1733 13-5375 I3-9047 14.2744 14.6450 i 6 .0000 16.5859 17.1784 17.7777 18.3825 18.9916 19.5080 20. 2308 20.8569 21 .4893 22 . 1269 22.7713 23.4189 24.0727 24 73l8 25-3936 26.0625 26.6355 27 .4122 28.0950 28.7814 29.4719 30. 1675 30.8681 3L5727 32 . 2809 32 -9935 33-7093 34.4269 35 1546 35-8827 36.6151 37 -3520 38.0709 38.8341 39-58i2 40.3321 41 .0860 41-8436 42-6045 43-3665 32.6667 33-8809 35-1099 36.3532 37.6iio 38.9781 40.1615 4i -4573 42.7654 44-0856 45.4184 46.7663 48.1224 49.4927 50.8753 52.2651 53 .6710 55 .0870 56.5122 57.9515 59-3999 60.8584 62.3290 63 .8116 65.3042 66.8059 68.3185 69-8393 71 .3710 72.9146 74.4662 76.0286 77 .6020 79.1614 80.7716 82.3717 83 .9816 85 -5995 87 .2271 88.8635 90.5061 107 .44 125 . 16 162.79 .6667 .7091 7531 .7988 .8460 .8949 9455 9977 0516 1072 1646 2237 2846 -3473 -4117 4779 -5400 .6160 .6878 7615 -8371 .9146 .9940 -0754 -1588 -2441 -3315 -4207 .5128 -6054 .7008 -7984 2.8980 3 .0196 3-1034 3 2093 3-3I74 3-4275 3-5399 3-6545 3-771 S.o6 6-59 10.39 BROAD-CRESTED WEIRS TABLE XVI. DISCHARGE OVER CIPPOLETTl'S TRAPEZOIDAL WEIR OF VARIOUS LENGTHS AND WITH VARIOUS DEPTHS. Formula, Q = 3.365 //tl. Depth of Water on Crest. DISCHARGE IN CUBIC FEET PER SECOND OVER WEIR. In Ins. In feet. /=ift. = i. 5 ft. /-aft /=3ft. / = 4 ft. /=5ft. /=7ft. /=ioft. 3 .6 . -9 I .2 !:I 2 . I 2-4 2.7 3-0 3-3 3-6 3-9 4.2 4-5 4-8 5-1 5-4 5-7 6.0 63 6.6 6.9 7-2 7-5 I* 8.4 8.7 9-0 9-3 9.6 9-9 IO.2 10.5 10.8 ii . i ii .4 ii. 7 12.0 12.3 12.6 12.9 .025 05 075 . i 125 15 175 .2 .225 25 275 3 325 35 375 4 425 45 475 -5 525 55 5-75 .6 .625 65 675 .7 725 75 775 .8 .825 85 875 9 925 95 975 i .0 i .025 1-05 1-075 0135 0367 .0690 .1064 .1488 .1956 .2464 .3010 3592 .4208 4855 5531 .6238 .6972 7730 .0202 .0566 1035 1596 .2232 2934 .3697 .4515 .5388 .6312 .7282 .8297 .9358 0459 1595 2777 3993 5246 6534 .7854 .9210 0599 .2018 3472 4955 .6462 .8007 .0269 0754 .1380 .2128 .2976 3912 .4929 .6020 .7184 .8417 9709 .1063 2477 3945 .5460 7035 .8658 .0328 2045 .3805 5614 7465 9357 3-1293 3 -3274 3-5283 3-7343 3-9437 4-1565 4-3733 4-5942 4.8i77 5-0453 .0404 1131 .2071 3192 .4464 .5868 7393 .9029 i .0777 i .2625 1.4564 1.6594 1-8715 2.0917 2.3190 2-5553 2-7987 3-0492 3-3067 3-57o8 3-8420 4.1198 4-4036 4-6939 4.911 5-2924 5-6014 5-9I56 6.2347 6.5599 6.8912 7.2265 7-5679 7.9154 8.2669 8.6234 8.9850 9.3516 9-7233 10. IOOO 10.4808 10.8666 11-2575 0539 . 1508 .2761 4256 5952 -7824 .9858 2039 4369 -6833 .9419 .2126 4954 -7890 3 .0902 3-407I 3.73i6 4-0656 4-4089 4.7610 5-1227 5-4930 5-8715 6.2585 6.6548 7-0565 7.4686 7-8874 8.2930 8 . 7466 9-1883 9.6354 10.0906 10.5538 ii .0225 ii .4978 i i . 9800 12.4688 I 2 . 9644 T3-566? 13 .9744 14.4888 15 .OIOO 0673 .1885 3451 5319 7440 .978o I .2322 1.5049 1.7961 2 . I 04 I 2.4273 2.7657 3.II92 3.4862 3 8649 4-2588 4-6645 5 .0820 5-5II2 5-9512 6.4034 6.8663 7-3393 7.8231 8.3185 8.8206 9-3357 9-8593 10.3912 10.9332 11.4854 12.0442 12 .6132 13.1923 13.7781 14.3723 14.9749 15.5860 16. 2054 16.8333 17.4679 18.1110 18.7624 ::::::: -1347 3771 .6902 I .0639 1.4881 1 .9560 2.4644 3 . 0098 3-5922 4 - 2083 4-8547 5-53M 6.2384 6.9724 7.7299 8.5177 9.3290 10. 1640 ii .0225 ii .9025 I 2 . 8068 13.7326 14-6787 15.6463 16 .6370 17 .6413 18.6715 19.7186 20.7824 21.8665 22 .9708 24.0885 25.2264 26.3846 27.5562 28.7446 29.9499 31 .1720 32.4019 33-6667 34 9350 36.2220 37.5249 13 .8030 14.5477 15.3065 16.0796 16.8619 17.6585 18.4692 19.2893 2O. 121 2 20.9649 21 .82O4 22.6876 23.5667 24.4551 25-3554 26. 2674 84 FLOW AND MEASUREMENT IN OPEN CHANNELS TABLE XVI. Continued. Depth of Water on Crest. DISCHARGE IN CUBIC FEET PER SECOND OVER WEIR. In ins. In feet. / = 3 feet. / = 4 feet. / = 5 feet. 1 = 7 feet. /=io feet. 13-2 13 5 13-8 14.1 14.4 14.7 15-0 iS-3 15-6 iS-9 16.2 16.4 16.8 17.1 17.4 17.7 18.0 18.3 18.6 18.9 19.2 19-5 19.8 20. i 20.4 20.7 21 .O 21.3 21.6 21.9 22.2 22.S 22.8 23.1 23-4 23-7 24.0 25-5 27.0 28.8 30.0 . i 125 150 175 . 2 225 -25 275 3 325 35 375 4 425 45 475 5 525 55 575 .6 625 65 .675 7 725 75 775 .8 .825 85 875 9 925 95 975 .0 125 25 4 2-775 11.6524 12.0513 12.4553 12.8644 13.2764 13-6936 14.1148 14.5410 15-5365 16.0684 16.6071 17-1525 17.7019 18.2581 18.8197 19.3880 19.9603 20.5394 21 . 1238 21.7123 22.3075 22.9082 23.5128 24.1242 24.7396 25.3604 25.9866 26.6l82 19 .4206 20.0855 20.7588 2 I . 4406 22.1274 22.8226 23.5246 24.2349 24.9503 25.6742 26.4047 26 . 1404 27.8844 28.6352 29.3910 30.1552 30.9245 3I-7005 32.4833 33-2727 34.0685 34.8702 35.6782 36.4913 37-3111 38.1376 38.9691 39.8074 40.6515 4I-5009 42-3577 43-2179 27.1888 28.1198 29 .0624 30.0168 30.9784 31-9517 32-9344 33-9289 34-9305 35-9439 36.9666 37.9966 39-0382 40.0893 41-1474 42.2173 43 2943 44-3808 45.4766 46.5818 47-6959 48.8183 49-9495 51.0878 52.2355 53-5926 54.5568 55.7304 56.9121 58.1013 59-3008 60.5031 61 .7211 62.9442 64. 1720 65 .4116 66.6560 72.999 79-541 87.619 03-156 38.8412 40.1711 41 .5177 42.8812 44-2548 45-6453 47-0492 48.9699 49.9007 51-3484 52.8095 54-2808 55-7688 57.2704 58.7820 60.3105 6 i .8490 63 .4011 64.9666 66.5455 68.1370 69.7405 71-3565 72 .9826 74.6222 76.2752 77.9383 79.6149 83-3030 83.0018 84.7154 86.4358 88.1730 89.9203 91 .6743 93 -4452 95 .2228 104. 285 H3 -63 125.17 I33-C8 MEASUREMENT OF CANAL WATER 85 that over several types of such weirs, and for any width of cross- section exceeding 2 feet, the following formula applies: This formula applies to heads exceeding six inches and up to twice the breadth of weir crest. Mr. E. C. Murphy has determined multipliers to be used in finding the discharge over various forms of broad-crested weirs in connection with Bazin's formula. These and the tables of discharges computed or experimentally determined have been brought together by Mr. Horton in Bulletin 200 of the U. S. Geological Survey. (See also p. 406. ) 96. Measurement of Canal Water. That water flowing in open canals may be sold by quantity it is necessary that the volume admitted to the canal may be readily ascertained at any time, and that the method of admission may be so regu- lated that it cannot be tampered with. As no method has yet been devised for easily and cheaply accomplishing this, water is almost universally disposed of by some means other than by quantity. It is customary in India to charge a land rental which is dependent on the amount of water used. In our country, water is regulated in accordance with the character of the crop as on this rentals are charged per acre irrigated rather than by the amount of water required. In other words, water is not sold like other commodities having intrinsic value, by the yard, pound, or gallon. Numerous efforts have been made to devise some cheap and convenient method of measuring water at a cost commen- surate with its value, but none can as yet be said to have achieved success. 97. Requisites of a Measuring Apparatus or Module. Prof. L. G. Carpenter enumerates the following as the conditions most desirable for a module or apparatus for measuring irrigation water : Its discharge should be capable of conversion into the com- mon measure, which is cubic feet per second. The ratio of discharge indicated from two outlets should be the actual ratio. The same module should give the same discharge wherever placed ; 86 FLOW AND MEASUREMENT IN OPEN CHANNELS it should be capable of being used on canals of all sizes, and of being set to discharge any fraction of its capacity for the process of distributing pro rata. Attempts to tamper with or alter its discharge should leave traces easy to recognize; and it should be FiG. 9. Foote's Measuring W eir, A. Water Divisor, B. simple enough to be operated by men of ordinary intelligence, so that calculations should not be required to regulate the discharge of different modules or to determine the amount thereof. It should occupy but small space, and the discharge should not be affected by variations of the water-level in the supplying canal. It should be inexpensive, and cause the least possible loss of head. Nearly all modules attempt to maintain a constant pressure of water above the opening, the orifice remaining unchanged. 98. Methods of Measurement. In Italy and in some other portions of Southern Europe a " module" or measuring apparatus has been employed with some success for the measurement of METHODS OF MEASUREMENT 87 canal water. This module consists essentially of inserting in the canal bank a regulating gate on which the height of head can be maintained. The size of the orifice being known, the amount of water passing through it can be at any time ascertained. Mod- ifications of this module are employed to a limited extent in India and to a greater extent in the United States. The unit of measure commonly employed in America and Italy is the "miner's" or statute inch, though the second-foot is replacing it. In India the amount of water flowing in canals and distributaries is meas- ured either by a gauge rod placed in some smooth portion of the channel, as in a masonry-lined aqueduct, while floats are timed for a given length in the aqueduct; or by means of a V-shaped measuring weir. In the West the ordinary module employed for measuring the miner's inch is a box flume closed by a lifting gate, in which case the head above the orifice is changeable and the amount passing through is indeterminate. Sometimes a modification of this module devised by Mr. A. D. Foote is used, whereby the head over the orifice can be maintained with some degree of certainty. (Fig. 9.) None of these modules is satisfactory, however, for the measurement of large volumes of water. The measuring weir is in all probability the most satisfactory method yet devised of obtaining an ac- curate measure of the volume of water passing through a canal. The great desideratum in irrigation is a simple device for reading from a dial or similar recorder the discharge of water in open ditches. A FlG I0 Au ^ tralian water Meter, modification of the Venturi meter furnishes such an apparatus, but at considerable cost for installation. A meter recently introduced on Australian canals fulfils the same purpose less satisfactorily and with a probable error of ij to 2 per cent. This consists (Fig. 10) of a wheel 88 FLOW AND MEASUREMENT IN OPEN CHANNELS with radial vanes set horizontally in a box in the bottom of the canal and just below a stop or check. The water passes under the latter and rises through the wheel which is caused to revolve and record on a dial the discharge. The operation of this meter involves a loss of head of from i to 3 inches according to the size of the canal. 99. The Statute Inch or Module. As already stated, the statute inch is a variable quantity, depending on its designation in different States. As an example, the statute inch of Colorado (Art. 58) is defined as follows: An inch-square orifice which shall be under a 5 -inch pressure, measured from the top of the orifice to the surface of the water, in a box set in the banks of the ditch. This orifice shall in all cases be 6 inches perpendicular inside measurement, and all slides closing the same shall move horizon- tally, while from the water in the ditch the box shall have a descent greater than one-eighth of an inch to the foot. 100. Rating Flumes. Under the laws of the State of Colorado rating flumes are constructed by the owners of private channels for the measurement of the flow of water, while the State Engineer is directed to compute the amount of water passing through them at various stages. A rating flume offers a convenient means of ascertaining the amount of water flowing in laterals and distribu- taries at various depths. It consists of a simple open flume which is placed in a straight portion of the channel a few hun- dred yards below its headgate. It is of even width with the channel, on the same grade, and its sides are sufficiently high to carry the amount of water likely to enter. For channels exceed- ing 6 feet in width an apron and wings of one-inch plank are built for 7 feet above and below the flume. The latter is generally 16 feet in length, consisting of a framing of 6 by 6 scantling, placed 4 feet apart and lined with one-inch or two-inch plank. After these flumes have been constructed and placed the engineer rates them by means of a current meter, and furnishes the Water Commissioner and owner of the private channel with a table showing the quantities of water which will flow through them at various depths. It is then only necessary to raise the headgate until the desired depth flows through the DIVISORS 89 flume, when the gate may be locked. The great difficulty with this, as with any similar device, is the changeability of head in the main channel above the headgate, the fluctuation therein causing a change in the volume passing through the flume, ne- cessitating a corresponding change in the position of the gate. 1 01. Divisors. Another method of distributing water to consumers is that by means of a dividing box, the object of which is to give each consumer a definite portion of the water flowing in the lateral. The difficulty of dividing the water into two or more equal parts arises from the fact that the water has not a uniform velocity across the entire channel. If, therefore, equal openings be made across a channel, those near the centre have the greater discharge. As a consequence the use of a divisor gives only approximate results. A simple form of divisor is that shown in Fig. 9, B. In this there is a moveable partition A, which can be slid out into the main channel so as to give the amount of water required in the branch. In order to maintain an equal velocity, the water is brought to a state of approximate rest by a weir board a few inches in height, the crest of which is sharp on the up-stream side. 102. Stream Measurement Under Ice. Discharge measure- ments may be made in ice-covered streams either with weir or meter. With the former this may be done as readily as in open streams provided the stream is kept clear of ice for a short dis- tance above the weir crest. In making current meter measurements holes are cut in the ice and velocity determinations are made at depths of .2 and .8 feet below the bottom of the ice. It has been found that the mean velocity can be found at either of these depths within a small percentage of error. 103. Works of Reference. Flow and Measurement of Water in Open Channels. BARROWS, H. K., and HORTON, R. E. Determination of Stream Flow During the Frozen Season. U. S. Geological Survey, Water Supply Paper No. 187. Washington, D. C., 1907. BAZIN, M. Recent Experiments on the Flow of Water over Weirs. Translated by A. Marichal and J. C. Trautwine, Jr. Proc. Engineers' Club, Phila- delphia. 9O FLOW AND MEASUREMENT IN OPEN CHANNELS CARPENTER, L. G. Measurement and Division of Water. Bulletin No. 27 State Agricultural College. Fort Collins, Col., 1894. CHURCH, IRVING, P. Mechanics of Engineering: Fluids. John Wiley & Sons, New York. FANNING, J. T. Hydraulic and Water-supply Engineering. D. Van Nostrand & Co., New York, 1890. FLINN, A. D., and DYER, C. W. D. The Cippoletti Trapezoidal Weir. Trans. Am. Soc. C. E., Vol. XXXII. New York, July, 1894. FLYNN, P. J. Irrigation Canals and Other Irrigation Works, and Flow of Water in Irrigation Canals. Denver, Col., 1892. GREEN, J. S. Fourth Biennial Report State Engineer of Colorado. Denver, Col., 1889. HORTON, ROBERT E. Weir Experiments, Coefficients and Formulas. U. S Geological Survey, Water Supply Paper No, 200 Washington, D C., 1907. HOYT, J. C., and GROVER, N. C. River Discharge. John Wiley & Sons. New York, 1907. JOHNSON, J. B. Theory and Practice of Surveying. John Wiley & Sons, New York, 1888. MULLINS, Lieut.-Gen. J. Irrigation Manual. E. & F. N. Spon, New York, 1890. MURPHY, E. C. Accuracy of Stream Measurements. U. S. Geological Survey, Water Supply Paper No. 94. Washington, D. C., 1904. MURPHY, E. C., HOYT, J. C., and HOLLISTER, G. B. Hydrographic Manual, U. S. Geological Survey, Washington, D. C., 1904. NEWELL, F. H. Part II, nth and i3th Annual Reports U. S. Geological Sur- vey, Washington, D. C., 1890 and 1892. TRAUTWINE, JOHN C. Engineers' Pocket Book. John Wiley & Sons, New York, 1890. WEISBACH, P. J. Hydraulics and Hydraulic Motors. Translated and Edited by A. Jay Du Bois. John Wiley & Sons, New York, 1891. CHAPTER VII SUBSURFACE-WATER SOURCES AND SEWAGE FOR IRRIGATION 104. Sources of Earth Waters. The water which enters the earth by percolation either from rain or from canals, reservoirs, or lakes finds its way through the soil to some lower level where favorable geologic structure enables it to again reach the surface. This seepage water may move slowly through the particles of subsoil, its motion being rather that due to absorption or capillary attraction than to direct percolation ; or it may enter some seam between two formations from which it may find an exit perhaps at some great distance through a spring or artesian well. The flow of water by percolation is limited not only by the degree of porosity of the strata, but by their inclination. Yet compara- tively impervious rocks frequently furnish abundant supplies which are the result of capillary attraction. 105. Motion of Ground Water. Rain-water in its down- ward motion through the soil ultimately reaches a level which is comparatively saturated. The surface of this zone is called the water table, and varies greatly in depth below the ground surface in different localities. The amount of this ground water is so great that it has been estimated as sufficient to cover the surface of the earth to a depth exceeding 3000 feet and equal in total volume to one-third that of the ocean water of the globe. This ground water is in continuous though exceedingly slow motion, and this is true not only in porous sands but in even the hardest rocks. It is known also that this ground or seepage water flows more freely at high than at low temperatures. At a mean depth of 6 feet below the surface perhaps one-third more water will flow in sand in the warmest than in the coldest part of the year. Among the most important conclusions on this 91 92 SUBSURFACE-WATER SOURCES AND SEWAGE subject are those of Mr. Allen Hazen, which for closely packed sand saturated with water are expressed in the formula h //Fahr.+ 10 where v is the velocity of the water in meters daily in a solid column of the same area as that of the sand, or ap- proximately in million gallons per acre daily; c is a constant factor which present experiments indicate to be approximately 1000; d is the effective size of sand grain in millimeters ; h is the loss of head ; / is the thickness of sand through which the water passes ; t is the temperature (Fahr.). The formula can only be used for sands with coefficients below 5 and effective sizes from o.i to 3.0 mm., and with the coarser materials only for moderately low rates. Mr. Hazen publishes a table in his book showing the rela- tive quantities of water at different temperatures which passed through experimental filters. Taking as unity the quantity passing at 50 F., 0.70 passed at 32 and 1.35 at 71; or for every three degrees increase in temperature the quantity of water passing increased by 5%. In the above the effective size is the size of grain such that 10% by weight of the particles are smaller than this. The uniformity coefficient is the ratio of the size of grain which has 60% of the sample finer than itself to the size of which has 10% finer than itself. An idea of the slowness of flow of ground water may be had from the studies of Mr. N. H. Darton, who places the rate of motion in the sands of the Dakota formation at a mile or two a year. A French engineer gives the same rate, or an eighth of an inch a minute. In Arizona a rate of one-fourth of an inch a minute, and in Kansas three-eighths inch a minute, have been estimated (Art. 120). At Agua Fria, Arizona, the measured rate of flow of ground water in creek gravels having 28% voids was 4 feet a day. As a result of careful investigation, Mr. C. S. Slichter gives the rate of flow for a grade of 10 feet per mile as follows : j UNDERFLOW 93 Material. Velocity, Miles. Per Annum, Feet. Fine sand o.oi 52.8 Medium sand 0.04 216.0 Coarse sand o. 16 845 .o Fine gravel 1.02 5386.0 1 06. Underflow. This word has been improperly used to designate a supposed vast sheet of water flowing eastward under the slopes of the great plains from the Rocky Mountains. It is otherwise and properly used by Slichter to describe the water moving in a thalweg or valley bottom beneath the gravelly bed of a watercourse. Though such underflow may not be possible in the fine silt and sand forming the beds of some streams, it may be of appreciable amount as stored water in coarser sands and gravels. The amount and rate of underflow vary greatly with the source of seepage water, the nature of the material and the slope. In the Hondo and San Gabriel rivers, California, the rate of movement of underflow has been determined to be from 3^ to 5 and 7 feet per day. Velocities of flow through the bed of the Fresno canal, California, of 1.6 feet to 4.8 feet a day, have been measured. At the Weldon valley canal, Colorado, velocities of underflow of 1600 feet a year have been observed. On the Mojave River, California, underflow velocities of 6, 20, 35, 48, and 64 feet per day were measured at various points. In con- clusion it may be stated that the velocity of underflow is very small and the total amount is generally insignificant as a source of water supply for irrigation. The velocity is especially small in the beds of silt-laden streams, though the quantity of under- flow water may be correspondingly great. 107. Sources of Springs and Artesian Wells. Wells and springs usually derive their water supplies from shallow forma- tions as gravels, sands, and marls. Their temperature may be variable owing to the changes in the temperature of the surface of the soil, while their flow is affected by precipitation of recent occurrence and by evaporation from the surface of the ground. Gravitation tends to draw the water toward the centre of the earth, and it percolates in that direction until intercepted by some impervious stratum along which it finds its way. If the water fills a pervious stratum so surrounded by impervious 94 SUBSURFACE-WATER SOURCES AND SEWAGE strata that it is prevented from escaping, and the hydrostatic pressure due to the inclination of the beds is sufficient to bring the water to the surface, the conditions are favorable for the production of an artesian well. All that is necessary is to pierce the upper confining stratum by boring, when the water will escape. Generally artesian supplies exist in the newer sand- stones and other equally porous rocks. Waters are frequently gathered into such strata from distant catchment basins. Where such a water-bearing stratum approaches the surface in a broad plain it forms an extensive artesian basin. 108. Artesian Wells. Deep wells do not always overflow. The condition of overflow depends on whether the pressure is sufficiently great to force the water above the surface, in which case they are known as artesian wells. Frequently the water will reach within but a few feet of the surface, when an ordi- nary well or shaft can be excavated and the 'water pumped to the desired height. In many other cases the pressure is such that the water spouts forth from the well under considerable pressure to great heights. In an artesian area of considerable extent the various wells seriously influence each other. In the San Gabriel and San Bernardino valleys in Southern California it has been found that after a certain number of wells have been sunk each additional well affects its neighbors by diminishing their discharge. There thus comes a point in the sinking of wells when the number which can be utilized in any given area or basin is limited. 109. Examples of Artesian Wells. Some great wells have been sunk in different parts of the world. The celebrated Grinnell well in Paris commenced with a 20-inch bore and is gradually reduced to an 8-inch bore at the bottom; its depth is 1806 feet, and its yield has been as great as 1.5 second-feet. A well has recently been bored in the neighborhood of Wheeling, West Virginia, to the great depth of 4500 feet, but is dry. At Speren- berg, near Berlin, is a well 4170 feet deep, and at Schladabach, near Leipsic, is a well 5740 feet in depth. In St. Louis is a well which reaches a depth of 3850 feet, about 3000 feet below the sea- level. In San Bernardino and San Gabriel valley in Southern CAPACITY AND COST OF ARTESIAN WELLS 95 California and in the upper San Joaquin valley in the neighborhood of Bakersfield are some very extensive artesian areas, but the greatest artesian basins of the West are found in the neighborhood of Waco, Texas; Denver, Colorado; and the James River valley and the neighborhood of Huron in the Dakotas. In 1890 there were 8097 artesian wells on farms in the arid region. Of these 32.110 were in California, 2,524 in Utah, 596 in Colorado, and between 460 and 527 respectively in North Dakota and South Dakota, and 534 in Texas, besides a few in each of the remaining States and Territories. Of these wells 48^ per cent were used in irrigating 51,896 acres at the average rate of 13.2 acres per well. Their average depth is 210 feet, average cost $245, and average discharge 0.12 second-feet. no. Capacity and Cost of Artesian Wells. The capacities of flowing wells are relatively small as compared with the volumes of water required in irrigation. Of the eight thousand wells reported from the arid region comparatively few are of sufficient capacity for use in irrigation. The great majority are shallow in depth and small in bore and discharge. They range from 100 to 200 feet in depth, from 2 to 4 inches in internal diameter, and discharge rarely as much as o.i of a second-foot; though this volume, if stored in a suitably located reservoir, should irrigate a moderate-sized farm. On the other hand there are, especially in South Dakota and Southern California, some very large flow- ing wells. In the former State there are reported to be at least twenty-five wells with discharges ranging from i to 6 second-feet, and in Southern California about thirty Wells of similar capacities. The largest well in South Dakota delivers continuously about 6.68 second-feet. The cost of sinking artesian wells is an exceedingly variable quantity, and is dependent upon the depth and bore of the well and the material through which it is sunk. In some localities, under favorable conditions, 6-inch wells of moderate depth are sunk and lined at prices ranging between $2.75 and $3.50 per foot. In North Dakota, where wells are sunk through sandstone, wells of 2 to 4 inches diameter are sunk for about 80 cents for the first hundred feet up to $1.50 for the second hundred feet. One well 96 SUBSURFACE-WATER SOURCES AND SEWAGE 1084 feet in depth cost $4000 and yields 4 second-feet. In South Dakota are many 2 -inch wells of depths from 250 to 300 feet, which have been sunk at the very low price of $75, the price in- creasing thence to $300 for a 3-inch well 300 feet deep. In other places, where more gravel and stone are encountered, 2 -inch wells have cost $300, and 3- and 4-inch wells from $400 to $1000. One well 850 feet in depth, 4 inches in diameter, cost $1800, and discharges 3 second-feet, irrigating about 100 acres. In Colorado in sandstone and hard clay the cost of well-drilling averages $2 per foot. in. Storage of Artesian Water. Having decided, from a study of the geology and a knowledge of the success attained by other wells, the general locality in which the well is to be drilled, its specific location should if possible be on the highest point of the land to be irrigated, and in such a position that it may be outside of and tributary to the reservoir in which the water is to be stored. Since artesian wells flow continuously during twenty- four hours of the day and three hundred and sixty- five days in the year, it is desirable to store as much of the water which flows during the non-irrigating period as possible, in order that the greatest duty may be gotten from the well. The volume flowing continuously from almost any well is usually too small to enable it to flow over the land in sufficient volume for the purposes of irrigation, so that a necessary adjunct to nearly every well is a storage reservoir of greater or less dimensions. In the case, how- ever, of a well which discharges about i second-foot, or nearly enough to irrigate 100 acres from unstored flow, such a well may be made capable of irrigating ten times this area if the water flow- ing at other times than the irrigating periods can be stored. Small reservoirs, sufficiently large to retain only enough water to pro- duce the requisite head for flowing over, may be built as are watering-tanks on railways, or they may be cheaply excavated in the highest ground on the farm and properly lined. Larger ones may be constructed by making use of the natural configura- tion of the country and building a dam across a hollow or ravine. (Chap. XV.) 112. Size of Well. The volume of the well does not depend MANNER OF HAVING WELLS DRILLED 97 upon its size. A 6-inch well will not necessarily discharge twice as much water as a 3-inch well perhaps not as much. The amount of flow depends directly upon the volume of the water- bearing strata and the pressure due to its initial head or source. Providing this is sufficiently great, then the discharge of the well is dependent on its diameter. Other things being equal, a large well will cost more to drill, but will be more easily and cheaply cleaned and kept in operation than a smaller one, which is apt to clog. Further, during and after drilling an accident may ruin a small well, while a larger one may be recased with diminished bore and still remain serviceable. For purposes of irrigation it may in general be said that a well less than 4 inches in diameter should not be drilled, and it is probable that one with a bottom bore greater than 8 inches will not be economical. Nearly all wells which terminate in soft rock, sand, or gravel discharge more or less of these materials. To prevent this from clogging the well it is not uncommon to place perforated pipe in the bottom of the well through the water-bearing stratum. There are many styles of such pipe, but in general it may be stated that pipe with circular perforations of uniform diameter is not the most serviceable, as it is apt to become clogged. Some of the patented perforated pipes with slots having less aperture on the outer than on the inner surface are preferable. In some cases ex- perience may show that it is not desirable to insert perforated pipe, but to let whatever comes to the well be discharged and col- lected in the storage reservoir. 113. Manner of Having Wells Drilled. There are many responsible firms who make a business of drilling and boring artesian wells, and for those who are unfamiliar with the business of well-sinking it is better to contract with some such firm to perform the work required. On the other hand, the sinking of a well is not a difficult operation for those who have any idea of the process, though by contracting they are certain of having the well sunk as they desire, within a fixed price, and are relieved of the risk of accidents. In the oil and gas regions the drilling of wells to tap oil- and gas-bearing strata, which is a process entirely similar to that 98 SUBSURFACE-WATER SOURCES AND SEWAGE of drillings wells for water, is a matter of every-day occurrence, and nearly all who desire to sink wells perform the work on a sort of half-contract system. The principal apparatus com- prises an engine, boiler, carpenter's rig, and set of drilling-tools, and the common practice is for the owner to provide all except the tools and fuel and let the drilling of the well at so much a foot to a contractor who furnishes these and does the work of putting down the well. In Ohio and Pennsylvania wells drilled in this manner by half-contract cost from 50 to 80 cents per foot for moderate-sized wells up to $1.50 to $2 for large and deep wells. 114. Varieties of Drilling-machines. Wells may be drilled by various methods, among the chief of which are by cables, poles, and hydraulic process. Provided the well is to be drilled by contract, it is of little importance what method is employed, since the contractor is responsible for the proper completion of the work, and the style of rig is a matter for his own choice. In the Dakotas and some other of the plains regions it has been found that wells drilled with pole machines have proved most satisfactory and performed the cheapest work, aside from the amount of time taken in coupling and uncoupling the rods. In the oil-and gas-bearing regions cable machines are most popular. There are many patterns of hydraulic, jetting, and rotary rigs which are adopted by different well-boring firms. The latter are dependent upon a rotary motion given to a piston-rod working by hy'draulic power and turning a tubing with cutting edge. In hydraulic jetting machines, which can be used cheaply only in gravel or sand, there is employed a short drill-bit having a hollow shank through which a jet of water is forced from pipe rods, thus creating an upward current which carries out the drillings. Some of these hydraulic and jetting machines have met with remarkable success. The chief advantage of pole rigs over cable rigs is in the certainty of the revolutions given to the drill, as the rods form a rigid connection between the drill and the machine above, and the motion is uniform in the direction of tightening the screws of the joints. This tends to preserve the connection, VARIETIES OF DRILLING-MACHINES 99 and keep the drill under perfect control. Cable rigs are chiefly preferred because of the ease with which they can be operated and the speed with which the tools can be lowered and removed and the bailing apparatus substituted in their place. The chief disadvantages as compared with the pole rigs is in the greater friction produced by the corrugated surface of the cable, the uncertainty as to whether the striking bar reaches the bottom of the drill, the likelihood of cutting or bending the cable, and FIG. ii. Portable Artesian-well Drilling Rig. the danger of breaking under the strain when tools become fast. As the cable is rotated both to the right and left there is also liability of uncoupling the joints at the tools, and there is a pos- sibility that the cable may not produce the proper rotation in the drill, and thus not bore the hole truly circular. There are now on the market a number of excellent portable well-drilling rigs, both of the old reliable walking-beam type (Fig. n), and also jetting and hydraulic rotary rigs. These can frequently 100 SUBSURFACE- WATER SOURCES AND SEWAGE be purchased outright at prices which will render them cheaper than any other method of having wells drilled. 115. Process of Drilling. The general process of drilling consists in having a long, heavy drilling-bar, the lower end of which is dressed to a cutting edge, which is dropped into a hole in the rock and by its weight cuts or breaks the stone where it strikes. At each blow this rod is turned a little, thus making the hole round. The drill is hung from the end of a cable or series of jointed poles which are raised and dropped by machinery. After the drill has worked for a short time it is removed, and the drillings, or small pieces of rock which have collected in the bottom of the hole and deaden the blow of the drill, are removed. This is done by pouring water in the hole if it be dry, and the fluid mud thus formed is lifted to the surface by a long, narrow bailer with a valve at its lower end. These operations of drilling from three to five feet, then cleaning out the mud and drilling again, are alternated until the desired depth is reached. If casing or lining is to be introduced and the hole is not drilled truly cylindrical, it is reamed out by a steel tool of desired diameter, weighing about 125 pounds and attached in place of the drill. The apparatus which goes to make a drilling-machine com- prises an engine and boiler of about 20 horse-power, a set of drilling-tools, and cable or poles. These latter are generally spoken of as the rig. It is also necessary to provide tubing or casing to line the well through such permeable strata as might cause the loss of water or through such strata as may provide water which is undesirable for the purposes required. It is some- times necessary to line wells with tubing throughout their entire length, and in such cases it is usual to begin with a large bore, say 8 inches, and after sinking this to a given depth, say 200 or 300 feet, to reduce the diameter of the tubing by an inch or two. The "set of tools" which compose the drill for the latter is not a solid bar, but several pieces weigh about 2500 pounds, and consist of a steel "bit" or "drill," of the size of the bore desired, screwed into the lower end of the "auger stem," which latter is a steel rod 30 feet long and 3 inches in diameter. To the upper end of this are screwed "jars," and above them the PROCESS OF DRILLING IOI ''sinker-bar," which is 15 feet long and 3 inches in diameter, and of steel. The jars by slacking together in falling cause the sinker-bar to act on and through them to the drill as a hammer. The term "rig" generally includes, in addition to the set of tools, the woodwork and necessary iron fittings forming a derrick to carry a sheave at a sufficient height, perhaps 50 to 80 feet, to swing the drilling-tools clear of the ground; also, both wheels and shaft on which the drill cable is wound; the sand-reel for winding up the smaller rope used in cleaning out the drillings; a walking-beam to give vertical motion, and a band- wheel for transmitting power from the engine to the moving parts. After the engine has been started and the walking-beam is made to rock up and down at the rate of 20 to 30 strokes a minute, lifting the tools with it, the length of stroke being adjustable from 15 inches to 3 feet, the rope is then twisted by means of a stick, first in one direction for a while and then in the opposite direction alternately. This twisting of the rope turns the drill, and the driller who handles the rope knows by the "feel" how the tools are working, the texture of the rock, and the occurrence of an accident. Occasionally the temper and set-screws are turned out a little, thus lowering the tools. After the drilling has gone on to a depth of 4 or 5 feet the tools are hoisted clear of the floor, the bull-rope swung off to one side, and the bailer or sand -pump is swung over the hold from the sand-reel, and is allowed to drop by its own weight, and upon reaching the bottom is filled with mud and sand through the valve at its lower end and is then drawn up and emptied; this process being re- peated if necessary to clear the hole before drilling is again re- sumed. The rate of drilling depends wholly upon the character of strata encountered, but averages from 15 to 50 feet per working day. A method of deep-well construction employed in California and known as the stovepipe method is admirably adapted to conditions where the material to be drilled consists of coarse debris. Casing from 10 to 14 inches in diameter is put down, reaching in one instance to 1300 feet in depth. A starter is used consisting of a length of 15 to 25 feet of No. 10 riveted sheet steel 102 SUBSURFACE-WATER SOURCES AND SEWAGE with a sharpened steel shoe. The remainder of the casing above is of No. 12 sheet steel in lengths of only two'feet, each following section being smaller than the last so as snugly to telescope for one foot of length, thus forming a double shell of stovepipe casing. This is sunk by the ordinary oil-well type of machinery, the casing being forced down, however, by hydraulic jacks. After the well is sunk a cutting- knife is lowered into it and vertical slits are cut in the casing opposite water-bearing strata. The advantages of these methods are : absence of short fragile screw-joints; flush outer surface which does not catch in clay or projecting rocks; its elastic character permits it to adjust itself to obstacles and stresses; its cheapness for large sizes of casing, the short sections permit the hydraulic jacks to force it down; the ability to perforate the casing at any depth with a large size of perforation inside. The cost of such wells averages about $i per foot for casing; $40 for the starter; and for the drilling 50 cents per foot for the first 100 feet, thereafter 25 cents additional for each succeeding 50 feet. 1 1 6. Capacity of Common Wells. The supplying capacity of common wells is frequently increased considerably by irri- gation. As water is applied to the soil through a period of years the subsurface-water plane rises, and it may be reached at lesser depths than previously. In this way irrigation water may be used over several times; by pumping it from wells it may find its way by seepage back to the streams, from which it may be again diverted. The capacity of surface or common wells de- pends on the degree of fineness of the water-bearing stratum, fine-grained material yielding water more slowly and of less amount than coarser material. The yield also depends on the head or depth below the surface of the water-table at which the flow takes place; also upon the size and shape of the exca- vation and the character of the well walls or casing. The yield is directly proportional to the freedom with which the water- bearing material permits the movement of water, and also to the head or depth by which the water-table is lowered. Of a series of wells across the Rio Grande valley near Las Cruces, N. M., WELLS, POWER-PUMPED 103 those near the river, in fine compact deposits of the valley bottom, have a small yield compared with the greater capacity of wells some distance from the river, under the mesa foot in the coarser mountain debris. If the well is shallow, increasing the diameter increases the flow; but if deep and relatively small in diameter, as a pipe, increasing the diameter does not appreciably increase the flow. For the above reasons driven-pipe wells yield rela- tively more water than open dug wells. The extent to which common wells may be used as a source of supply for irrigation is not appreciated in the United States, where as yet irrigation is practised only in a large way and ir- rigators are but just coming to a realization of the advantages of intensive cultivation, whereby but a few acres are worked by a single farmer, but in the most thorough manner possible. In a few portions of the Far West, notably in Central and Southern California, where Italians and Chinamen are engaged chiefly in market-gardening, wells are employed to some extent for the supply of water. In such cases the water is raised by one of several processes (Chap. XIX), chiefly by windmills, and by mechanical lifts worked by horse-power, and similar to the Per- sian wheel of Asia. It is to India that we must look in order to gain an idea of the extent to which wells may furnish irrigation water. In the Central Provinces of India 120,000 acres are irrigated from wells. In Madras 2,000,000 acres are irrigated from 400,000 wells. In the Northwest Provinces 360,000 acres are irrigated frort wells. Some of these wells are sunk to depths as great as 80 to 100 feet, in some cases through hard rock, and are capable in ordinary seasons of irrigating from I to 4 acres each. These wells may really be said to supplement irrigation from canals and reservoirs, for after the waters of the latter have been used and have seeped into the soil they are caught* by the well and are again used for irrigation. Thus wells as an adjunct to canals may be said to add materially to the duty of the latter. 117. Wells, Power-Pumped. Throughout the West are now many drilled wells which supply large quantities of water for 104 SUBSURFACE-WATER SOURCES AND SEWAGE TUNNELLING FOR WATER ^05 irrigation either by windmill pumping or by power pumping with gasoline, steam or electric motors (Chap. XIX). The Reclamation Service has just completed a most elaborate project near Garden City, Kan., for pumping ground water in the Arkansas River valley from a series of 23 driven wells. Power is furnished by two steam turbines direct-connected with 225 kilowatt alternators located near the middle of a line of pumping plants 23,000 feet in length. The pumping stations are 1,000 feet apart and each pump draws water from 10 wells drilled in the gravel to a depth of 8 to 12 feet (Fig. 12). At present there are in operation ten p-inch centrifugal pumps of 5 second-feet capacity each operated by 25 horse-power motors and thirteen io-inch centrifugal pumps of similar capacity and power, all discharging into a concrete-lined conduit which empties into 12 miles of ditch. 118. Tunnelling for Water. Tunnels are sometimes driven in sloping or sidehill country to tap the subterranean water- supplies. These are practically horizontal wells, differing from ordinary wells chiefly in that the water has not to be (dumped to bring it to the level of the surface, but finds its way by gravity flow to the lands on which it is to be utilized. Near the Khojak Pass in India is a great tunnel of this kind. This is run near the dry bed of a stream into the gravels for a distance of over a mile. The slope of its bed is 3 in 1000, its cross-section is 1.7X3 feet, and its discharge about 9 second-feet. The Ontario Colony in Southern California derive their water-supply from a tunnel 3300 feet in length, run under the bed of San Antonio creek through gravel and rock. Its cross-section is 5 feet 6 inches high, 3 feet 6 inches wide at bottom, and 2 feet wide at top. It is partly timbered and partly lined with concrete, having weep- holes in the upper part of the tunnel. Its discharge is about 6 second-feet. The supply from several subtunnels has been such as to average nearly 10 second -feet per linear mile of tunnel. The Spring Valley Water Company which supplies San Francisco, California, has recently made some of the most ex- tensive developments of water from subsurface sources yet recorded. One bed of gravel in a stream valley having an area of 1200 acres absorbs practically all the drainage of 300 square io6 SUB SURF ACE- WATER SOURCES AND SEWAGE miles. Into these gravels were sunk 91 wells which yield 36 acre-feet of water per day. Another similar bed has been de- veloped by drifting over 14,000 feet of tunnel 5' 6"X$' 6", with nearly as great a length of smaller branch tunnel. Into this drain several hundred driven wells (Fig. 13) which yield over 45 acre-feet of water per day. 119. Underground Cribwork. Submerged cribs were planned for the American Water Company on Cherry Creek in Colorado, and have been used by the Citizens' Water Company on the FIG. 13. Subterranean Water Tunnel and Feed-wells, California. South Fork of the Platte River in Colorado. The former enter- prise contemplated a submerged open crib sunk in the gravel bed of Cherry Creek, and resting on blue clay which is 73 feet below the surface of the stream, rising to a height of 70 feet, with its crest 3 feet below the bed of the stream. This was not to be a dam, but to stop the movement of that portion of the sub- surface water which might enter the cribwork. It would consist of timbers 14 inches in dimension at the bottom, decreased to 8 inches at the top, placed 4 feet apart across stream, and planked OTHER SUBSURFACE-WATER SOURCES 107 on both faces with interstices of 3 inches on the upper face. The water caught in this crib work was to be pumped to the surf ace. The Citizens' Water Company develops the underground waters of the Platte River by means of a series of gathering-gal- leries, consisting of perforated pipe and open cribwork laid at a depth of from 14 to 22 feet below the surface of the gravel bed of the stream. The cribs (Fig. 14) are 30 inches square, and about a mile of these have been built running up the bed of the stream, besides about a mile of perforated pipe 30 inches in diameter. The average daily yield obtained by these galleries is nearly 10 acre-feet of water, which is led off through the pipes by natural flow. 1 20. Other Subsurface-water Sources. Earth waters may be gathered for irrigation by other means than springs, common or artesian wells, or tunnels. In portions of the plains region, especially in Kansas, subsurface supplies have been obtained by running long and deep canals parallel to the dry beds of streams or in the low bottom lands and valleys. These canals, acting like drainage ditches, receive a considerable supply of water and lead it off to the lands. In the dry beds of streams in California submerged dams have been built which reach to some impervious stratum and cut off the subterranean flow, thus bringing the water to the surface. In some experiments made on two subcanals in Kansas the amount of water obtained was 15 second-feet for each mile in length of excavation, which was 6 feet in depth below the subsurface-water plane. (Art. 104.) It was found that the depth and length were the controlling fac- tors, the breadth of the canal having little effect on the amount of water entering. It was also found that the increase of flow due to the deeper cuts was nearly equal to the square of the depth. It may be generally stated that the amounts of water to be derived by such means are very limited and do not approach those claimed by the advocates of so-called " underflow." 121. Sewage Disposal. One of the most important and difficult problems with which municipal engineers have to deal is that of sewage disposal. In the humid regions, where the large cities are usually found close to rivers of some magnitude or near 108 SUBSURFACE-WATER SOURCES AND SEWAGE the ocean, the sewage has usually been easily disposed of by dis- charging it into the natural waterways and allowing it to be carried off to the ocean. In the arid region this method of dis- posal is not so easy of accomplishment, because of the lack of waterways into which to discharge it. Difficulty has also been encountered in some of the older inhabited portions of the world, and as a result other and newer methods of disposing of sewage are attracting attention. A method which is rapidly gaining in favor is by flowing the sewage over the soil and permitting it FIG. 14. Gathering-cribs, Citizens' Water Co., Denver. to filter downward through this and find its way to the natural watercourses. It has been found that nature performs the chemi- cal and mechanical action of removing the heavy matter and purifying the more liquid portions of the sewage even more satis- factorily than it can be done artificially. This has naturally led to the utilization of such sewage water in irrigating crops, and this method of disposal of sewage is of especial interest to the people of the arid West. It is found that by this means the disposal of sewage may SEWAGE IRRIGATION IOQ not only be rendered a simple matter, but that, instead of being an item of great expense to the municipality, it may even in a few instances be rendered a source of income. The use of sewage for irrigation has been practised for many years quite extensively in various portions of Europe, notably at Paris, which thus dis- poses of one-third of its sewage; at Berlin, which uses all its sewage for irrigation; at Edinburgh, Birmingham, Florence, Milan, Madrid, and many other cities and hundreds of smaller towns which maintain sewage farms. In our own country this method has met with some little favor. In the East it is em- ployed successfully at Meriden, Conn., and Pullman, 111., and in the West the following ten cities dispose of their sewage by irrigation: Colorado Springs, Trinidad, Fresno, Pasadena, Redding, Los Angeles, Santa Rosa, Helena, Cheyenne, and Stockton, with populations varying between one thousand and fifty thousand inhabitants. It will thus be seen that this is no new problem either in engineering science or municipal govern- ment. It is well tried, and has been practised for a couple of centuries in some European countries, and in every case where the soil is suitable has been found an economical and satisfactory method of disposing of sewage. 122. Sewage Irrigation. Sewage may be disposed of by discharging it on land in practically three ways, namely, by intermittent downward filtration, by broad irrigation, and by a combination of these two methods. Intermittent downward filtration is simply a mode of purifying sewage, by applying it to land without making any attempt to utilize it in irrigation, or, in other words, in the watering and cultivation of crops. It requires a much smaller area of land than where it is used in irrigation. It depends for its utility on the fact that sewage passed through porous soil becomes aerated and rapidly purified through the oxidizing action of the air which the soil holds in its pores, and for its successful operation requires that the sewage shall not be passed through the same piece of land continuously, but at long enough intervals in order to permit the soil to become aerated. By thus intermittently resting the soil the sewage from 500 to 1000 people per acre can be purified. This system in 110 SUBSURFACE- WATER SOURCES AND SEWAGE itself is of little interest to irrigators, and therefore will not be fur- ther described. The utilization of sewage by broad irrigation requires the employment of a much larger tract than for intermittent down- ward filtration, one acre of land being sufficient to utilize the sewage of from 150 to 500 people. This system has been largely and successfully used, especially where the soil is porous and underlain by a deep porous subsoil. When the farm is properly laid out and carefully managed the effluent water is pure enough to be practically harmless when returned to the natural drainage channels. One of the most serious objections to the disposal of sewage by irrigation is the fact that the farmer must take the sewage at all times, even though he have more than he wants and it hurts his land. It has been found, however, that a com- bination of the above methods, in which intermittent filtration is used as a supplement to broad irrigation, practically overcomes this disadvantage, and is the most satisfactory method of dis- posing of and utilizing sewage on land. This is done by laying out a small portion of the land as a filter-bed by providing it with ample underdrainage, and on this the sewage is discharged at such times as it is not needed in irrigation. 123. The Fertilizing Effects of Sewage. It is well known that the excrement of human beings is far richer in nitrogenous substances than that of any other animal, and that it has a far greater fertilizing value. Human excrement loses its fertilizing value rapidly by decomposition, and it is therefore necessary to apply it to the soil within a few days, and to this end the only practical way of moving it is by water carriage. It can thus be moved as much as fifty miles without deteriorating, while the volume of carrying-water need never exceed 10 cubic feet daily per individual, or about the proportion of water to excreta which usually finds its way into city sewage. On the sewage farms of Paris the most varied products, from vegetables of all kinds to flowers and fruits, are profitably grown. The cultivation of vegetables is predominant, cabbages and cauliflower being especially prolific. The sewage water is em- ployed as a manure or for watering grain, mangel-worzel, and EFFECTS OF SEWAGE IRRIGATION ON HEALTH III meadows. Lucerne is cut as often as four or five times a season, and mangel-wurzel produces as much as 40 tons per acre. The municipal engineers of Paris state that the rent value of lands irrigated by sewage has increased in value since their reclama- tion from 100 to 400 per cent. At Colorado Springs enormous crops are reported to be raised from sewage irrigation, while the lessee of the right to use the city sewage is not troubled with the vexatious problem of priority of rights. The sewage of the city of Fresno, Cal., is used in irrigating a large tract of land on which all varieties of vegetables are profitably grown. The best evi- dence obtainable indicates that the fertilizing effects of sewage are not as great as claimed, and that the crops raised by its use in humid regions are scarcely more abundant than those gotten by use of chemical fertilizers. In the arid regions it produces better crops than water alone, but scarcely better than those gotten by the use of water with artificial fertilization. Thorough cultivation of the soil greatly increases its value as a fertilizer. 124. Effects of Sewage Irrigation on Health. Fears have been entertained that sewage farms would prove dangerous to the health of the neighboring districts, and that the crops grown on them would be unwholesome. These fears, however, have undoubtedly proven groundless, as shown by experience in many portions of the world. It is found that the combined action of soil and vegetation furnishes the true solution of the problem of sewage disposal on land. It satisfies the sanitary conditions, and at the same time gains for agriculture a source of manure and water which would otherwise run to waste. The principle on which this system rests is, that when pure water charged with materials in suspension and solution is flooded over permeable soil the upper bed of this acts as a filter, and all matter in sus- pension is separated by mechanical action. After this superficial mechanical filtration the water reaches the roots of the plants, which absorb with benefit the fertilizing substance remaining in solution. Lastly, as the waters which have escaped the ab- sorbent action of the plants or the retentive action of the soil con- tinue their descent through a subsoil either naturally or artificially permeable, they undergo in this an oxidizing action which changes 112 SUBSURFACE-WATER SOURCES AND SEWAGE them from organic substances into nitrates or nitrites purely mineral substances, which present no danger of fermentation, and are harmless when sufficiently diluted. Chemical analyses of the waters flowing from the Paris sewage farms show no sensible trace of decomposable nitrogen and but little more than a trace of nitrogen in the state of a mineral am- monia. On the other hand, where no vegetation exists on the surface a very perceptible and dangerous quantity of nitrogen has been obtained. It was also discovered that the descent through the porous soil insures a satisfactory aeration, as sewage water flowed on the surface and containing scarcely any oxygen issues from a bed of stony earth but six feet in depth with a gain of from 400 to 600 per cent of oxygen, so that there was a com- plete revivification of the sewage water, which was not merely clarified, but actually purified. Water has been drawn from wells sunk in the middle of lands irrigated by sewage, and this water has been found to be perfectly clear and identical in ap- pearance and taste with waters of the subterranean-water plane which supplies wells elsewhere in the neighborhood of Paris. The experience at the Pullman, 111., farm is similar, as there the superintendent of the farm lives in a handsome house in the centre of the irrigated area, and is in no way affected or annoyed by the sewage. Thorough tilling of the soil after each flowing of sewage is essential, and it is by the creation of a proper tilth that the aera- tion of the sewage and incorporation of the solid matter with the soil is accomplished. It is this process of absorption of the water, incorporation of the deposits with the soil, and its utilization by plants that guarantees the salubrity of the surrounding country. Villages which have sprung up in the neighborhood of sewage farms in Europe show no signs of disorders or diseases of any kind. A more surprising fact is, that there is practically no stench from the flowing of sewage over the land. When put on the land with no more dilution than the flushing water, there is at that time a perceptible and disagreeable odor, but as soon as the soil has been cultivated this entirely disappears. 125. Duty of Sewage. Chemical analysis of sewage water DUTY OF SEWAGE 113 indicates that the theoretical amount which may be used in irrigat- ing crops with benefit to agriculture, and which the soil and crops will deprive of nitrogen, alkalies, and phosphoric acid, which elements most affect the purity of water, is 4.5 acre-feet per acre. However, where several crops are produced in a single season on the same soil, and more especially where these crops consist of alfalfa and similar plants which require heavy watering by flooding methods, as much as 12 to 15 acre-feet per acre may be applied without harmful effect. On the sewage farms of Gennevilliers, in the suburbs of Paris, the average annual appli- cation of sewage during ten years varied between 15 and 22 acre- feet per acre. This soil, it seems, is especially well adapted to the purpose, as it consists of a bed of alluvium from 20 to 30 feet in depth, and composed of sand and gravel interspersed with a little vegetable mould. It is believed that this natural filter-bed will remain in good condition even after the formation of mud many feet in depth. It has been found, however, that the average depth of deposit for 10 years does not exceed 0.5 of an inch. It appears, also, that these deposits are not foul or dirty, as they contain as much as 50 per cent of silicious matter which renders them friable and permeable, and the cultivation of the soil each year incorporates this deposit with the soil, resulting in the main- tenance and increase of the arable earth. At the Colorado Springs sewage farm the sewage of 12,000 people has been beneficially disposed of in irrigating 15 acres of meadow and alfalfa and 10 acres of vegetables. This is approxi- mately at the rate of i acre to 500 inhabitants. At Pasadena, California, the sewage of 6000 people is beneficially used in irri- gating about 40 acres, or at the rate of about i acre to 150 inhab- itants. At Los Angeles, California, the entire sewage, which averages 105 second-feet flowing constantly, has been used in irrigating 1 700 acres ; this is the sewage of 50,000 people, so that it was employed at the rate of about 30 individuals per acre, also about at the rate of 40 acre-feet per acre per annum. At Santa Rosa, California, 20 acres of land are employed in disposing of the sewage of 5200 people, and at Helena, Montana, 40 acres in dispos- ing of the sewage of 14,000 people. At the Meriden, Connecticut, 8 114 SUBSURFACE-WATER SOURCES AND SEWAGE broad irrigation and intermittent filtration farm, one of the most modern laid out in this country, the sewage of 15,000 people, amounting to about 3 second-feet running continuously, is being successfully treated and disposed of on less than 14 acres a rate of 150 acre-feet per acre. It must be remembered, however, that the above figures do not represent the ultimate duty of sewage as such. They show rather the limits in amount of sewage which may be disposed of, that is, the extreme amounts which may be utilized on a given area with- out harmful effects, rather than the minimum amount which may be utilized with beneficial effects to the crops. In other words, they show the limits to which sewage may be disposed as a sani- tary problem, rather than the limit of crop which may be irrigated with a given amount of sewage as an irrigation problem. It is not unlikely that where sewage is used rather for its value as an irrigating material than otherwise the sewage of as few as from 50 to 100 people may suffice to irrigate an acre, and that not over 4 to 6 acre-feet in depth per annum, allowing for waste in winter, will produce satisfactory and beneficial effects in irrigation. 126. Methods of Laying out Sewage Farms and Applying Sewage. In preparing land for sewage irrigation it must be remembered that the sewage cannot be disposed of continu- ously on the same piece of land with benefit to crops, but that it must be rotated from one plot to another so as to give each a rest and permit of the soil being cultivated and the crops handled. With this end in view it has been found that the most satisfactory way of laying out a sewage farm is to divide it into many very small tracts or plots of about one acre in extent each, so arranged and subdivided by distributing channels that the sewage may be applied to them separately and independently. Experience has shown that first of all the soil must be of suitable texture, and care should be taken in choosing a location in which may be found a deep and light surface soil, underlain if possible by a deep and porous subsoil, preferably of sand and gravel. If the slopes of these are such as to furnish good natural drainage, no difficulty is likely to arise in utilizing such land for an indefinite period of time under proper treatment. METHODS OF LAYING OUT SEWAGE FARMS 115 The sewage farm at Meriden, Connecticut, consists of three feet of fine material at the surface, below which is a deep layer of sand and gravel which acts admirably as a filter-bed. This land, however, was at first very much overworked, only a small area being utilized in disposing of the sewage. It has since been successfully revivified and put in condition for suitable operation for many years, by thoroughly cleaning the surface and scraping and ploughing to a depth of 14 inches. Moreover, a number of ditches 3 feet wide were sunk down into the subsoil, the finer material being removed and replaced by gravel. In this way the surface was connected with the gravel or natural filter-bed by the simplest form of artificial drainage. In cleaning the filter-bed it was found that the sludge which had dried hard by exposure to the atmosphere could be raked off into piles and carted away. It was also found that over the greater part of the area the depth of this was scarcely one-eighth of an inch after three years of usage, though this increased to nearly 6 inches at the outlet of the sewage drain. In making additional sewage plots at the same farm a depth of about two feet of the close-grained surface soil has been removed and the remainder ploughed to a depth of about 14 inches, reaching a few inches into the gravel beneath. The cost of preparation of this farm has been nearly as great as one thousand dollars per acre, but this is owing largely to the very small area employed and the inferior quality of surface soil. At the Paris sewage farms the water is brought from the city in closed sewers and then in an open drain, and finally is distributed through the 55 acres of irrigated fields in about 3.5 miles of open surface channels. After a suitable soil has been chosen and the land has been underdrained or otherwise suitably prepared, it should be divided by open drains, preferably lined, into plots of from 200 to 400 feet on a side. The sewage should be brought to the limits of the farm in closed sewer conduits, which must be properly ventilated. It is desirable at the outlet of the conduit at the entrance of the farm to construct a small storage reservoir, suitably lined, since it may be necessary to retain the sewage of at least twenty -four hours, and certainly of a night, at times when it is not possible Il6 SUBSURFACE-WATER SOURCES AND SEWAGE to use it. A screen should be placed at the head of the farm dis- tributaries in order to keep out such matter as it is not desirable to use in irrigation, and this may be removed at certain intervals, either to waste land, where it may be ploughed under, or may be disposed of by cremation or other process. The most satisfactory mode of constructing such a reservoir so that no odor shall emanate from it is to cover it with a rough board roof and build a ventilat- ing chimney, which can be constructed cheaply of lumber and should not be less than 50 feet in height. Such a chimney is sufficient to prevent any nuisance, either from the reservoir or from sewage flowed therefrom on to the fields. By such means sewage which is used on freshly irrigated land scarcely emits the slightest odor, while none is perceptible immediately after ploughing. The most satisfactory way of applying sewage for irrigation is through furrows between rows of vegetables, the simple furrow method of irrigation (Chap. XIV) being employed. In some cases, however, notably at Trinidad, Colorado, the em- bankment or check method has been employed, more especially in the cultivation of grain and forage crops. After applying sewage to crops it is left only so long as to permit it to become dry enough to work, when the land is thoroughly tilled and all solid matter turned over before the next application of sewage, while such a variety of crops must be employed as to make the irrigation season as long as possible. During the non-irrigating period, the winter months, the sewage may be flowed in rotation over various plots of land and be permitted to filtrate through this and find its way back to the natural drainage channels. It is desir- able, however, to use precaution and not overcharge the land, and this may be prevented, by tilling it a few times during the more open days of winter. As soon as the crops are to be sown in spring it is desirable, should too great an accumulation of solid matter appear on the surface, to rake this off before planting the season's crops. Experience has proven that sewage reaches the lands at a sufficiently high temperature, even in the coldest weather, to permit it to remain unfrozen and to find its way by nitration into the soil. WORKS OF REFERENCE 117 127. Works of Reference. Subsurface- water Sources and Sewage for Irrigation. ALLEN, CHARLES A., and Others. Sewage Disposal. Trans. Am. Soc. C. E., Vol. XVIII. New York, 1888. BUTLER, W. P. Irrigation Manual. W. P. Butler, Aberdeen, S. D., 1892. CHAMBERLAIN, T. C. The Requisite and Qualifying Conditions of Artesian Wells. Fifth Annual Report, U. S. Geological Survey. Washington, D. C., 1884. DARTON, N. H. Preliminary List of Deep Borings. U. S. Geological Survey, Water Supply Paper No. 61. Washington, D. C., 1902. ENGINEERING NEWS. "Sewage Purification in America." New York, Feb- ruary 23, 1893; July 1 8, 1894. HALL, WM. HAM. Irrigation in Southern California. Part II, Annual Report of State Engineer. Sacramento, 1888. HAMLIN, HOMER. Underflow Tests. Water Supply Paper No. 112, U. S. Geo- logical Survey. Washington, D. C., 1905. HAY, PROF. ROBT., and Others. Geological Reports on Artesian Underflow In- vestigations. Department of Agriculture, Washington, D. C., 1892. HILL, PROF. ROBT. T., and Others. Same as preceding. JACKSON, Louis D'A. Hydraulic Works. W. Thacker & Co., London, 1885. MANNING, ROBERT. Sanitary Works Abroad. E. & F. N. Spon, London, 1876. NETTLETON, E. S. Artesian and Underflow Investigations. Department of Agriculture, Washington, D. C., 1892. NEWELL, F. H. Artesian Wells for Irrigation. U. S. Census Bulletin No. 193. Washington, D. C., 1890. NEWELL, F. H. Agriculture by Irrigation. Report at Eleventh Census, 1890. Washington, D. C., 1894. Drilling and Care of Oil-wells. Report Geological Survey of Ohio, Volume 6. Columbus, 1888. ORME, S. H. Sewage Irrigation. Engineering News. New York, July 5, 1894. POWELL, J. W. Artesian Wells. Part II, Eleventh Annual Report, U. S. Geo- logical Survey. Washington, D. C., 1890. RAFTER, GEO. W., and BAKER, M. N. Sewage Disposal in the United States. D. Van Nostrand Co., New York, 1894. REID, H. I. Utilization of Sewage for Irrigation Purposes. Annual of American Society of Irrigation Engineers. Denver, Colorado, 1893. SLIGHTER, C. S. The Rate of Movement of Underground Waters. U. S. Geo- logical Survey, Water Supply Paper No. 140. Washington, D. C., 1905. SPON, ERNEST. Present Practice of Sinking and Boring Wells. E. & F. N. Spon, London, 1885. WALL, NORVEL W. Disposal of Sewage of Trinidad, Colorado, by Irrigation. Annual of American Society of Irrigation Engineers. Denver, Colorado, 1893. Part Two CANALS AND CANAL WORKS CHAPTER VIII CLASSES OF IRRIGATION WORKS 128. Gravity and Lift Irrigation. Irrigation works may be divided into the above two great classes. Gravity works include all those by which the water is conducted to the land with the aid of gravity or natural flow. They include 1. Perennial canals;- 2. Periodical and intermittent canals; - 3. Inundation canals;- 4. Storage works; 5. Artesian-water supplies; - 6. Subsurface- or ground-water supplies. - Lift irrigation includes those forms of irrigation in which the water does not reach the land by natural flow, but is transported to it by pumping or other means of lifting. It may be divided into two main classes: 1. Irrigation by watering-pots, hose, or sprinkling-carts; 2. Irrigation by pumping. The first needs no explanation; the last may be divided into four principal classes : 1. Pumping by animal power; 2. Pumping by water-power; 3. Pumping by windmills; 4. Pumping by mechanical power. The sources of supply for all forms of gravity irrigation are defined by the titles of the classes. They are from perennial streams, intermittent streams, artesian wells, submerged dams, 118 NAVIGATION AND IRRIGATION CANALS IIQ tunnels or cuts, or by the storage of perennial, intermittent, or flood waters. The sources of supply for lift irrigation may be from wells, canals, storage works, lakes, or streams. 129. Navigation and Irrigation Canals. Canals may be used for irrigation alone or for irrigation and navigation com- bined. The conditions required to develop an irrigation canal are: first, that it shall be carried at as high a level as possible so as to have sufficient fall to irrigate the land to a considerable dis- tance on both sides; second, it should be fed by some source of supply that will render it a running stream, so that the water used in irrigation may be constantly replaced; third, it should have such a slope and velocity as to reduce to a minimum the deposition of sediment and the growth of weeds; fourth, its velo- city should be the greatest possible in order that the cross-section may be reduced to a minimum for a given discharge. Naviga- tion, on the other hand, requires of a canal : first, that the water in it shall be as nearly still as possible, so that navigation may be equally easy in both directions; and, second, it requires no further supply of water than is necessary to replace the loss by evaporation and absorption, and at the points of transfer from higher to lower levels. It is thus seen that the requirements of the two classes are conflicting, and it is not deemed good practice to make irrigation canals available for purposes of navigation. 130. Sources of Supply. The climate, geology, and topog- raphy are the chief factors in deciding the class of work which belongs to a given region. Where the precipitation is small, occurring during a short period of the year, and resulting in the intermittent or periodical flow of the streams, canals of this class or storage works must be employed. Intermittent and periodical canals are usually very small in dimensions, commanding rela- tively small areas of land, and are generally employed by in- dividual farmers for the utilization of the waters of some stream which may be safely counted upon for a temporary supply during a few occasional spring storms or the melting of the mountain snows. They can only be used with safety where the precipitation is nearly sufficient for the cultivation of crops and the little water 120 CLASSES OF IRRIGATION WORKS which they supply is of value in helping this out. Storage works receive their supply from intermittent streams carrying sufficient volumes of water at flood times, or perhaps from perennial streams artesian wells, or in fact from any source from which a permanent supply of water may be obtained. Inundation canals are used almost exclusively in India and Egypt, and derive their supply from streams the beds of which are at an altitude relatively high compared with the surrounding country. They are thus supplied by flood waters which flow above the general level of the sur- rounding country, and rarely require any permanent headwork to control the entrance of the water into the canal. Artesian wells derive their supply from artesian water sources, which have their origin usually at some great distance and at an altitude considerably higher than the outlet of the well. Sub- surface cuts, tunnels, and wells derive their supplies from the seepage water with which the soil in nearly every country is per- meated (Chap. VI). 131. Inundation Canals. Inundation canals might also be called flood-height canals, as they are dependent for their water- supply on the height of flood rise in the river from which they are diverted. This variety of canals is employed most satisfactorily in connection with rivers which have built up their beds by the deposition of sediment, and therefore practically flow on the summits of ridges. The most notable of these are the Indus in India and the Nile in Egypt. There are a number of such streams in this country, as the Sacramento and the lower portions of the Yuba and Feather rivers in California, the beds of which are in some places at considerable heights above the surrounding country. The lower Mississippi belongs to the same class of streams. Inundation canals rarely require any permanent headworks for the control and admission of water to their channels, their heads consisting of a simple cut through the river bank or ridge which separates the river from the low-lying, surrounding country. As they depend upon flood rises for their supply, the beds of these canals are generally at some height above the beds of the rivers from which they are diverted, and usually at the level of mean or low water, so that when these streams are not in flood they do INUNDATION CANALS 121 not receive any supply and are therefore not perennial canals. Heads on such canals are usually situated in the true bank of the main river from which they draw their supply, but at such a position that they are not in a cutting bank or one against which in its meanderings the river impinges, lets it destroy the bank at this point, and thus the headwork, as occurred on the Colorado river below Yuma when it filled Salton sea in 1905. It is not un- common, however, to locate the headworks in sloughs or bayous which are found adjacent to rivers of this character. Such sloughs are generally larger than the canals which they thus feed, and the velocity of the water being less in them, as a consequence the silt which might otherwise be deposited in the canals is left in the sloughs. There are many such inundation canals taken from the river Indus. The difference in elevation between ordinary water stage and inundation level of this river is from 8 to 12 feet. The velocity of the river is in some places greater than the nature of the banks will stand, and therefore the heads of the inundation canals have to be opened afresh every year. These canals vary in bed-width from 6 to 50 feet, and are from 10 to 60 miles in length. They carry depths of water during flood periods of from 5 to 10 feet, and their slopes range from i in 4000 to i in 10,000. The inundation canals taken from the Nile in Egypt have usually a much lighter slope, ranging from i in 20,000 to i in 33,000, and some of the more modern of these have permanent control works at their heads with regulating bridges and escapes at places where they are not subject to destruction by floods. The flood rise of the Nile is about 15 feet, and the period of flood, which commences gradually and subsides slowly, is from August to October, and after its subsidence crops are sown in November and reaped in spring. The water of the Nile is not always de- livered to the ground as in ordinary irrigation during the growing of crops, but as it must be gotten when the flood is at its height, and this is the case with most inundation canals, it is permitted during the period from August to October to rest in basins formed by levees or embankments separating one basin from another. By standing in these basins it deposits its silt and enriches the 122 CLASSES OF IRRIGATION WORKS soil and at the same time soaks the ground so thoroughly that after the subsidence the soil retains sufficient moisture to mature crops. In the older methods of irrigation from the Nile the water was supplied directly from the river into the upper basin, and flowed from this through to the lower basins and then back to the river. Latterly, however, some great canals have been built which skirt the bluffs of the river, and instead of pouring the water into the upper basin and letting it run from one basin to another until it reaches the lower and is finally discharged from this back into the river, it is admitted to many basins separately from the canal, thus furnishing fresher water more evenly charged with sediment than the basins would have received by the old method. The greatest of the Egyptian inundation canals is the new Ibrahimiyah canal, which is diverted from the Nile near Assiout (Art. 354), and, skirting the western edge of the valley, irrigates about twenty great basins and a number of smaller ones, contain- ing in all an area of about 600,000 acres, and in addition 500,000 acres of high-level and Fayoum crops not divided into "basins, making a total of 1,100,000 acres irrigated by it. This, though really an inundation canal, acts practically as a perennial canal for a time, as its bed is about 6 to 8 feet below ordinary low Nile, when it has a minimum discharge of about 1500 second-feet. This great canal is about 160 miles in length, has a bottom width in its upper reaches varying between 160 and 230 feet, and a maximum depth of 33 feet with a surface slope of i in 22,000. Its maximum discharge has been as great as 32,000 second-feet, and it is quite open to the river without any headworks for the control of the water entering it. The first regulating work on its line is at Derout, where the water can be drawn from the canal by great regulating works into five branches or passed into the river through a large escape. At the terminus of this canal, at the lower end of the basin system near Queshesha, is the largest masonry escape in the world for discharging the water which comes from the canal and basins. Its maximum capacity is 80,000 second-feet, and it consists of 60 vents of 10 feet each, the maximum height on it being calculated at nearly 15 feet. It PERENNIAL CANALS 123 is closed by a series of great double gates operated by travelling cranes from the piers above. 132. Perennial Canals. Perennial canals derive their supplies from perennial streams or from storage .reservoirs. They may be divided into two classes, according to the location of their head- works. These are : 1. High-line canals, and 2. Low-service or deltaic canals. High-line canals are usually of moderate size, and are designed to irrigate lands of limited area which lie close under the foot of the higher hills. They are generally given the least possible slope, in order that their grades may remain high and command the greatest amount of land. In such canals it is necessary to locate the head works high up on the stream, frequently in rocky canyons where the first portions of the line may encounter heavy and expensive rock-work. Low-service canals are constructed where the majority of the lands are situated in low-lying and extensive valleys and where the location of the head of the canal depends not so much on its being at a relatively high altitude and com- manding a great area as upon the suitability of the site for pur- poses of diversion. High-line canals are more frequently con- structed where the water-supply is abundant and it is desirable to obtain the largest amount of land to which to apply it. Low- service canals are constructed where the irrigable lands exceed in area the amount of water available. Deltaic canals have been constructed chiefly in Egypt and India at the deltas of some of the great rivers, as the Nile, Ganges, Orissa, and others. They are essentially low-service canals and are built in regions where the slope is very small. As a con- sequence their cross-sections must be relatively large, that they may carry a given discharge with the least velocity. They are tisually navigable, and in most cases their water-supply is abundant. 133. Dimensions and Cost of Some Perennial Canals. In Table XVII, are given the dimensions, including the capacity and area commanded, and the cost in various terms, of some of the great perennial canals of the world. 124 CLASSES OF IRRIGATION WORKS Cost per cond -foot or Water used. in . O O * O O O M . .ON- PO t^ M O Q M . vo t^.Olt^t-vO O 45 f! *^ OOOOOOO^^J~OOOO O O O CO CO O ^ O | 1 w ^ O ^O \O 1 o .g : OOOOOOOO-tOOOOOOMr-O OOOOOOOOOoOOOOOOvoMt^vo i fl -' OOO^OO>J-3PO^-MMOOO s,-- I L <** & u OfOt^-OfOCOf^.O^OOOOOMPOO^r)Oi-iM g<3 (NMPOMMMM MOO'tOOt^O ^ ^ 2 "" ^ g J=> " . ^ OJ oj ^ ^ U ' _c ' : 3 o a 8 c : J . . . - = ' ' | 8 i j | lllllliliiiilllilfijl PARTS OF A CANAL SYSTEM 125 134. Parts of a Canal System. The machinery of a great perennial canal consists essentially of the following parts, which are treated here in the order given: 1. Source of supply ; 2. Irrigable lands; 3. Main canal; 4. Head and regulating works; 5. Control and drainage works; 6. Distributaries and laterals. The principal units of this system are the main canals and dis- tributaries. Between different canal systems the greatest points of difference are found in the headworks, and in the first few miles of diversion line, where numerous difficulties are frequently encountered, calling for variations in the form and construction of drainage works and canal banks. The headworks consist usually of the diversion weir with its scouring sluices, of the head regulating gates at the canal en- trance, and of the head escape or sand gates. The control works consist of regulating gates at the head of the branch canals, and of escapes on the line of the main and branch canals. The drain- age works consist of inlet or drainage dams, flumes or aqueducts, superpassages, inverted siphons, and drainage cuts. In addition to these works there are usually constructed falls and rapids for neutralizing the slope of the country, and tunnels, cuttings, and embankments. Modules or some form of measuring box or weir are necessary for the measurement of the discharge. CHAPTER IX ALIGNMENT, SLOPE, AND CROSS-SECTION 135. Relation between Lands and Water-supply. In de- signing an irrigation work the first consideration is the land to be irrigated. The projector must consider the area of this, its nearness to market, the quality of the soil, the climate, and the character and value of the crops which it will produce. In addi- tion the value and ownership of the land must necessarily be con- sidered. All of these quantities having been satisfactorily deter- mined and the necessity of supplying water for irrigation having been ascertained, the next question is the source of supply and its relative location to the lands. This supply may be found in some adjacent perennial stream, or it may be necessary to trans- port it across an intervening ridge from a neighboring watershed, or it may be necessary to conserve in storage reservoirs the flood flow of intermittent streams. The relation of the water-supply to the land, the extent of the latter, and the volume and permanency of the former are the most important items to be ascertained in the preliminary investigation of any irrigation project. 136. Diversion Works. The diversion works of a canal include i, the works for directing the water of the stream into the canal entrance, which may be by weir or by training works ; 2, the mode of controlling the amount of water admitted to the canals, which may be by regulating gates at its head or by simply making an open cut unregulated as in inundation canals; 3, scouring sluices, to prevent the deposition of silt at the canal head; 4, escapes or sand gates in the upper reaches of the canal line for the disposal of surplus water and the removal of sediment; and 5, the diversion line of the canal itself, or that portion required to bring the water to the irrigable land. The first problem in the preliminary design of a canal is the 126 ALIGNMENT 127 choice of the point of diversion or site for the headworks. These are usually located high up on the supplying stream in order to command the largest area possible and to receive water from the stream before the latter has become charged with silt from cutting its banks in the more low-lying country. Occasionally, however, where the area of land to be commanded is limited, it may be desirable to locate the headworks at some lower point on the stream. By locating the headworks high up on the supply stream it is usually possible to reach the watershed or interfluve by the shortest possible diversion line. The chief disadvantage of such a location is that the first few miles of diversion line are sure to be intersected by sidehill drainage, the passage of which may entail great difficulty and, if the slopes of the adjacent country are heavy, much expensive hillside cutting. By " diversion line" is meant that portion of the canal line which is required in order to bring it to the neighborhood of the irrigable land. The endeavor should always be so to locate the diversion canal as to reduce its length to a minimum, so that the canal shall command irrigable land and thus derive revenue at the earliest possible point. 137. Alignment. Having determined the source of water- supply, and its relation to the irrigable lands, the next question is the alignment of the canal. This should be such that it shall reach the highest part of the irrigable lands with the least length of line and at a minimum expense for construction. The line of the canal should follow the highest line of the irrigable land, preferably skirting the surrounding foothills and passing down the summits of the watersheds dividing the various streams in order that it may command land on each side by its branches. Careful preliminary and location surveys are necessary to procure the best alignment. That all possible locations may be examined, it is desirable, first, to construct a general topographic map on some large scale, perhaps 800 to 1500 feet to the inch, and with contour lines showing differences of elevation of from 5 to 10 feet. On such a map it i3 possible at once to lay down with a near degree of approximation the final position of the canal line. It is dso frequently possible from inspection of such 128 ALIGNMENT, SLOPE, AND CROSS-SECTION a map to save many miles of canal by the discovery of some low divide or some place in which a short but deep cut or a tunnel will save a long detour. Having laid down this line on the map, the final location may be made on the ground, with the aid perhaps of a few short trial lines to determine its exact position. 138. Method of Survey. The surveys necessary for properly designing and building a canal may be distinguished as hydro- graphic, preliminary, location, and construction surveys. The first has already been described in Chapters II to V inclusive, and includes all problems connected with the quantity, character, and chemical properties of the water-supply. The construction survey will not be described here other than to state that it is similar to such surveys on railway or other engineering work, and includes careful cross-sectioning of the canal line ; borings and trial pits to determine the nature of the subsurface formations ; the making of detailed estimates of the volume and kind of material to be moved; and the staking out of the line on the ground in accoid- ance with these estimates, in order that the contractors or laborers may know just where and how to work. Circumstances will determine whether both a preliminary and a location survey shall be made, or whether once going over the ground will suffice. These surveys may be divided into two general classes: (i) linear or trial-line surveys, and (2) contour topographic surveys. Where a contour topographic map is made, this will usually answer all the purposes of both classes of survey. It must be made to cover such an area of ground as will include all possible diversion lines as well as main lines, branches, and distributaries. Such a survey and map once made, it is the pre- liminary survey, and on it the location may be laid down with accuracy and practical finality, and it will in all liklihood be necessary to deviate from such a location but little as construction progresses. 139. Linear or Trial-line Survey. Starting from the upper end of the irrigable area, run a level line back up-stream on the grade chosen until it reaches the stream-bed. Should it strike this at a point unfavorable for the construction of headworks, a second trial line may be started at some suitable point above or below LINEAR OR TRIAL-LINE SURVEY I2Q the first and run in the opposite direction with the same grade, or, if it has been started up-stream, with the insertion of a fall or two; and this operation may be repeated until such a line is obtained as will begin at the most desirable site for headworks and reach the irrigable tract at the highest practical elevation with the shortest line and at the same time encounter fewest obstacles. The first trial line or two run as above serve practically as preliminary lines. They should therefore be run with long sights, there being no necessity for great accuracy in levelling. Only a level line is necessary, the chief object being to ascertain the relative elevations of the proposed sources of water-supply and the irrigable lands. The final location line having thus been approximately deter- mined, it should be fixed by the running of more careful trial lines, accompanied by a transit survey for location, and by cross- sectioning with the aid of a couple of rodmen, both by stadia and level, for a little distance to either side of the line. For this class of work a plane-table will be found more suitable than a transit, since on it can be sketched contour lines as the work progresses. From the end of the diversion lines thus developed a rough preliminary level and transit or plane-table line should be run back into the country, approximately on a grade contour line skirting the higher slopes. This line will furnish the data on which to estimate approximately the area of land controlled by this high-level line. These facts ascertained and the relations of the amount of water, its duty and the area of land which it will irrigate, and the total area under command having been deter- mined, trial location lines may be run in similar manner for the selection of the final main line and its branches. The combina- tion of level followed up for location by transit or plane-table with stadia accompaniment for cross-sections will then furnish all the details for final location. In all of the operations thus described substantial bench-marks should be established as frequently as possible, as well as tie-points for the horizontal control. When the final location trial lines are being run, more permanent bench- marks should be left at frequent intervals, and in the course of all 130 ALIGNMENT, SLOPE, AND CROSS-SECTION the surveys connections should be made as frequently as possible with the land-survey system of the country, if the work be in the western United States, in order that the relations of the irrigation project and various lines and ditches to this system of land surveys and the surrounding country maybe at once established (Art. 141). 140. Contour Topographic Survey. In practically all cases where the time and means at the disposal of the engineer will per- mit, the best results will be obtained by making in the beginning a detailed contour map of the area under consideration. In nearly all instances it will be best to precede such a survey by a hasty trial level line or two, in order to ascertain the feasibility of bringing the water to the lands, and the area that will be commanded. These questions settled, and the approximate location of diversion lines along steep hillsides or canyon walls having been ascertained, the contour survey should be made to include only so much of the diversion line as is in question, and of the irrigable area as will lie below the high-line levels. Where the location of the diversion line is fixed by the rough- ness of the topography, a good method of contour survey is to run out a couple of limiting grade contours with level and plane- table, the lower being at the lowest possible limit of diversion line, and the upper at the highest. In the case of the Santa Ana canal (Art. 148) the vertical distance between these two was found rarely to exceed 70 to 100 feet. These lines should be run in conjunction with stadia cross-sectioning, which should be plotted directly on the plane-table sheet on a scale of 100 to 500 feet to the inch, with a contour interval of 2 to 5 feet. With such a map the engineer may be able to lay down a final paper location. Where the diversion line terminates in more open, gently sloping country, the survey of the irrigable area is made thus: Beginning at the end of the survey for diversion line, and following around on the approximate high-line grade, a careful transit and level line should be run to the limits of the highest portions of the irrigable area. From this chained transit and level lines should be run with equal accuracy down the summits of the divides or interfluves separating the main drainage lines, and as these reach the lower limits of the area under examina- RIGHT OF WAY ON PUBLIC LAND 131 tion they should be connected by cross-lines. The whole may then be plotted on a suitable scale, say 500 to 1000 feet to one inch and in 5- or ic-foot contours. The sheet on which these lines are plotted may then be taken into the field either as a whole or divided into sections, placed on plane-table boards, and the topography filled in thereon. This should not be done by running out the various contours, but by irregularly cross-sectioning or dividing up the area by lines which shall so cut up the territory as to enable the contour crossings of the lines run on the plane-table to be connected from one line to the other with an accuracy well within the contour interval, and thus permit of the whole being filled up as a final map. This secondary work resting on the main chained and taped lines is preferably done in a more cheap and expeditious manner by using the plane-table instead of the transit, the stadia instead of the chain or tape, and in some cases the hand-level or vertical or gradienter angles in place of the spirit-level, though the former methods for elevations must be adopted and used with the greatest precaution. On such a map it then becomes an easy matter to lay down the approximate location of the main canal lines and their various branches, the sites of falls, regulating works, and escapes. There- after it may be necessary, prior to construction, to make other more detailed contour maps of limited areas, with a view to determining in special cases the more exact location of the heads of branches, the crossing of drainage lines, the position of escapes, and other critical points on the canal line. 141. Right of Way on Public Land; also State Desert-land Grants. In order to obtain right of way for canals, ditches, or reservoirs on private lands in the West, arrangements must be made, as elsewhere in the United States, by purchase or other- wise, with the owner. To obtain right of way on public lands, surveys, maps, and construction must be made to accord with certain regulations of the General Land Office, whereupon a grant of the land affected by the right of way will be made. This grant, however, is only for purposes of canal or reservoir construction, is dependent on the fulfillment of the conditions required, and is not transferred in fee. 132 ALIGNMENT, SLOPE, AND CROSS-SECTION Among other of the requirements which must be fulfilled that right of way may be granted are the following : The survey in all its parts must be connected with section and township corners of the public-land survey ; especially the termini of the canal, ditch, or lateral must be connected with the nearest corner. All data for the computation of traverses connecting with such corners must be entered in the field-notes. The method of running the grade lines must be described, as well as the size, graduation, and make of instrument used. Stations and courses must be num- bered, and field-notes must show whether the side or middle line of the canal has been run. Maps for filing with the general and local land offices must be drawn on tracing-linen, in duplicate, on the scale of 2000 feet to the inch for canals and 1000 feet to the inch for reservoirs, or on a larger scale in special cases. These maps should show all subdivisions of the public surveys, the source and amount of water-supply of the reservoir or canal, the details of alignment of canals, and flood lines of reservoirs. Permanent monuments must be set at the intersection of the water-line of the reservoir with the public-land lines, also on either side of the in- tersection of the canal lines, in such manner as to comply with the requirements of witness corners as laid down in the " Manual of Surveying Instructions," issued by the General Land Office in 1894. The map must also bear a statement of the width of each canal or branch at high-water line, the capacities of reservoirs in acre-feet, and height of proposed dam. They must also show, in ink of a distinctive color, other canals or reservoirs than those for which application of right of way is made. In addition all field- notes must be in duplicate, properly dated, and be filed like the maps; and both field-notes and maps should bear the certificates of the engineer and president of the company or owner of the canaL 142. Obstacles to Alignment. Such obstacles as streams, gullies, ravines, unfavorable or low-lying soil, or rocky barriers are frequently encountered in canal alignment. The best method of passing these must be carefully studied. It may be cheapest to carry the canal around these obstructions, or it may be better at once to cross them by aqueducts, flumes, or inverted siphons, or to cut or tunnel through the ridges. Careful study should be SIDEHILL CANAL WORK 133 made of each case, and estimates made of the cost not only of first construction, but of ultimate maintenance. In crossing swamps or sandy bottom lands it may be cheaper, because of the losses which the water will sustain from absorption, to carry the canal in an artificial channel through such places. If water be abun- dant, it may be less expensive on hillside work simply to build the canal with an embankment on its lower side, permitting the water to flood back on the upper side according to the slope of the coun- try. In such cases the losses by evaporation and absorption will be great in the beginning, but ultimately these flat places may become silted up and a permanent channel made through them. The relative cost of building a sidehill canal wholly in excavation or partly in embankment should be considered. If the hillside is steep and rocky, the advisability of tunnelling, of building a masonry retaining-wall on the lower side of the canal, or of carry- ing it in an aqueduct or flume will have to be considered. 143. Sidehill Canal Work. It is extremely difficult to carry a large canal along steep sidehill slopes. To get a sufficient cross-section to carry the volume required without unduly increasing the velocity demands the exercise of careful judgment. FIG. 15. Canal Cross-sections for Varying Bed-widths. It is possible to get the same cross-sectional area by employing different proportions of depth to bed-width. The less the cross- sectional area of a channel, the less its cost and the expense for maintenance. It is therefore necessary first to choose the highest possible velocity which the resistance of the material and the necessity of commanding land will permit, and then to give the canal such a cross-sectional area as will produce the required discharge. The great difference in excavation of two canals of equal capacity but different proportions of bed-width to depth is 134 ALIGNMENT, SLOPE, AND CROSS -SECTION graphically shown in Fig. 15. In one case vastly more material will have to be moved than in the other, while the surface exposed to evaporation and absorption will be greatly increased. Where the material is suitable and not too liable to cause loss by percola- tion, it is well to equalize the cut and fill. In this way still less material will have to be moved, for, as shown in the illustration, the depth of excavation is diminished by raising the lower bank. 144. Curvature. A direct or straight course is the most economical alignment, as it gives the greatest freedom of flow and causes the least erosion of the banks. It also greatly dimin- ishes the cost of construction and the losses by absorption and evaporation consequent on the increased length of a less direct location. It is an error in alignment to adhere too closely to grade lines following the general contour of the country. By the insertion of an occasional fall it is frequently possible to obtain a more desirable location and to diminish the cost of construc- tion by the avoidance of some natural obstacle. One of the most serious errors in alignment is the careless location of curves, to which detail too little attention is ordinarily paid. The insertion of sharp bends inevitably results m the destruction of the canal banks, or requires that they shall be paved or otherwise protected to prevent their erosion. On the other hand instances have been noted where engineers have inserted great curves carefully constructed on some fixed radius of absurd length, as though the canal were a railway line. Curv- ature diminishes the delivering capacity of the canal, and too sharp a curve endangers the structure itself. In large canals of moderate velocity it will be safe in most cases to take the radius of curvature at from three to five times the bed width of the canal. As the cross-section becomes smaller or the velocity is increased, the radius of curvature should be correspondingly increased. To keep up the discharge of a canal either its cross- section or grade should be increased in proportion to the sharp- ness of the curve. 145. Borings, Trial-pits, and Permanent Marks. In finally locating an expensive work, borings and trial-pits should be made, the former with a light steel rod and the latter by simple EXAMPLE OF CANAL ALIGNMENT 135 excavation, in order to discover the character of the material to be encountered. In making the final survey of a canal it is well to place at convenient intervals permanent bench-marks of stone or other suitable material. The establishment of these along the side of the canal in some safe place will give convenient datum points to which levels can be referred whenever it may be neces- sary to make repairs or run branch lines. Mile or quarter-mile pests or permanent stakes should also be set in the canal banks so that future surveys and changes in the line may be referred to these. 146. Example of Canal Alignment. Ganges Canal. An excellent example of a typical alignment on one of the great Indian canals is that of the Ganges canal, which heads in the Ganges River at Hurdwar, where the stream issues suddenly from between the foothills of the Himalayas on to the broad level plains. In the first twenty miles of its course the canal encounters considerable sub-Himalayan drainage, and the works for the passage of this and for the reduction of slope in the canal by means of falls are important (PI. I). The slope of the river-bed and country averages from 8 to 10 feet per mile. At the site of the headworks the river is divided into several channels, one of which, about 300 feet in width, follows the Hurdwar shore and rejoins the main stream half a mile below that town. As the discharge of the canal is 6700 second-feet and that of the river never falls below 8000 second-feet, only a portion of the water is required at any time. This is diverted to the Hurdwar channel by means of training works and tem- porary bowlder dams, and the current has deepened the chan- nel until it now has a uniform slope of yj feet per mile to the canal head. The regulator is about half a mile below the first training works, and consists of a weir and scouring sluices across the channel. In the first few miles the canal crosses several minor streams .which are admitted by means of inlets. At the sixth mile it is crossed by the Ranipur torrent, which is passed over it in a masonry superpassage 195 feet in breadth (PI. XVII). In the tenth mile the Puthri torrent, having a catchment basin of about eighty square miles, or twice that of the Ranipur, is carried 136 ALIGNMENT, SLOPE, AND CROSS-SECTION across the canal by a similar superpassage 296 feet in breadth. The sudden flood discharges in these torrents are of great vio- lence, the Puthri discharging as much as 15,000 second-feet and having a velocity of about 1 5 feet per second. In the thirteenth mile the canal encounters the Rutmoo tor- rent (Article 232), which has a slope of 8 feet per mile and a catchment basin half as large again as that of the Puthri. This torrent is admitted into the canal at its own level, and in the side of the canal opposite to the inlet is an open masonry outlet dam or set of escape sluices. Just below this level crossing is a regu- lating bridge by which the discharge of the canal can be readily controlled; thus in time of flood, by opening the sluices in the outlet dam and adjusting those in the regulator so as to admit into the canal the volume of water required, the remainder is discharged through the scouring sluices, whence it continues in its course down the current. In the nineteenth mile, near Roorkee, the canal crosses the Solani River and valley on an enormous masonry aqueduct (Arti- cle 239). The Solani River in times of highest flood has a dis- charge of 35,000 second-feet "and the fall of its bed is about 5 feet per mile. The total length of the aqueduct is 920 feet. The banks of the canal on the up-stream side are revetted by means of masonry steps for a distance of 10,713 feet, and on the down- stream side for a distance of 2722 feet. For i f miles the bed of the canal is raised on a high embankment previously to its reaching the aqueduct, and for a distance of half a mile below it is on a similar embankment. The greatest height of the canal- bed above the country is 24 feet (PL XVI). The aqueduct proper consists of fifteen arches of 50 feet span each. In addi- tion to these great works there are in the first twenty miles of the canal five masonry works for damming minor streams and a number of masonry falls. Beyond Roorkee the main canal follows the high divide between the Ganges and the west Kali Nadi, and continues in general to follow the divide between the Ganges and the Jumna rivers to Gopalpur, a short distance below Aligarh, where the main canal bifurcates, forming the Cawnpur and Etawah branches. EXAMPLE OF CANAL ALIGNMENT 137 PLATE i. Plan and Cross-section of Ganges Canal, Hurdwar to Roorkee, India. 138 ALIGNMENT, SLOPE, AND CROSS-SECTION The former tails into the Ganges River at Cawnpur and is 170 miles in length. The Etawah branch is also 170 miles long and tails into the Jumna River near Humerpur. The Vanupshahr branch leaves the main line at the fiftieth mile, and flows past the towns of Vanupshahr and Shahjahanpur. It formerly ter- minated at mile 82 J, emptying into the Ganges River; but it is now continued to a point near Kesganj, where it tails into the Lower Ganges canal. The first main distributaries are taken from both sides of the canal a short distance below Roorkee. The nature of the country offers abundant facilities for escapes from the canals, of which five are constructed on the main line, four at the Cawnpur branch, and three on the Etawah branch, besides numerous small escapes to the distributaries. 147. Example of Canal Alignment Turlock Canal. A typical American canal alignment is that of the Turlock canal, which is diverted from the Tuolumne River in California at a point where it emerges from the Sierras between high rocky canyon walls. For the first five miles the canal is built along steeply sloping hillsides, and it crosses numerous drainage channels in its endeavors to surmount the bluffs bordering the river and gain the irrigable lands. The topography is so irregular that the first attempts which were made at diversion were unsuccessful. The present location was discovered only after a careful contour topo- graphic map had been made of the entire region, and from this the canal line was laid down (Fig. 16). The headworks of. the Turlock canal consist of a masonry dam which is constructed as a common diversion weir for the Turlock canal and the canal of the Modesto irrigation district, which latter heads on the opposite or north bank of the river. This weir (Article 356) is located between high canyon walls, two miles above the town of La Grange, at a point where the abutments and foundation of the weir consist of firm homogene- ous dioritic basalt, in which scarcely any excavation is required. The canal is diverted from the south bank of the river at a point about 50 feet above the end of the main weir. Owing to the great floods which occur in this narrow canyon the water may rise as much as 15 feet in an hour, and the maximum height which EXAMPLE OF CANAL ALIGNMENT 139 it is estimated to reach above the sill of the canal is 16 feet. The pressure of this height of water on the regulator head would be so great as materially to increase the cost of its construction. Accordingly the canal heads in a tunnel 560 feet in length, blasted through the rock of the canyon walls, and having no regulating apparatus at its entrance. Where it discharges into the open Main FIG. 1 6. Turlock Canal. Plan of Diversion Line. cut, which is the commencement of the canal, regulating gates and scouring or escape sluices are placed. The entrance tunnel is 12 feet wide at the bottom, 5 feet in height to the spring of the arch, above which it is semicircular with a 6-foot radius. Its slope is 24 feet per mile, and it is excavated in a firm dioritic rock which requires no lining. The regulator in the canal head below the exit of the tunnel consists of six gates, each 3 feet wide in the 140 ALIGNMENT, SLOPE, AND CROSS-SECTION clear and 12 feet irf height. These gates are constructed of tim- ber and iron, and slide on angle-iron bearings let into the rock and firmly set in concrete. The escape is set at right angles to the canal-line heading immediately above the regulator, between it and the end of the tunnel, and tailing back into the Tuolumne River a short distance below the subsidiary weir. Like the regu- lator, the escape consists of six gates, each 3 feet wide in the clear, 12 feet high, and constructed of similar material and in like man- ner. It is estimated that whereas a maximum flood of 16 feet FIG. 17. Turlock Canal. View of Sidehill Work. over the sill of the tunnel will give a discharge in front of the reg- ulator and escape of about 4000 second-feet with a velocity of 20 feet per second, the wasting capacity of the escape will be at least 6000 second-feet, thus fully insuring the canal against acci- dent from this source. Below the regulating gates the main canal proper begins, having a capacity of 1500 second-feet. For the first 6200 feet it is excavated in slate rock on a steep hillside (Fig. 17). It has a bed width of 20 feet, depth of water 10 feet, the upper rock slope being J to i, while the lower bank or downhill slope, where gullies are crossed, is built up with an inner slope of J to i and is faced with 18 inches of dry-laid retaining-wall inside and outside, EXAMPLE OF CANAL ALIGNMENT 141 the interior of the bank consisting of a well-puddled earth core 12 feet in top width (Fig. 21). Where this portion of the canal is on ordinary sloping ground, not crossing gulches, its dimen- sions are the same, but the inner face only has the 18 inches of riprapping, the downhill slope of the bank consisting of dirt and other soil. The top width of the bank in such places is 5 feet and the puddle wall 5 feet in thickness. This portion of the canal line has a grade of 7.92 feet per mile, which gives a velocity of 7^ feet per second. After the second year this slate-rock so disin- tegrated by air-slacking that much of it fell away, and the sides of the cutting caved in, requiring extensive rebuilding on firmer lines and flatter slopes. At the end of this slate-rock work the canal empties into Snake ravine, up which the water of the canal runs for 940 feet. This was effected by constructing an earth dam across the mouth of the ravine just below the entrance of the canal, which raises the sur- face of the water so as to form a small settling reservoir and pro- duces a flow up the course of the ravine for the distance above mentioned. The earth dam is 20 feet wide on top, 318 feet long on the crest, with slopes of 2 to i and a maximum height of 52 feet. This dam was partly constructed of material borrowed from its abutments and the canal excavation and partly by a silting process from material washed out of a hydraulic cut at the upper end of the ravine. This hydraulic cut, which is utilized as the canal bed, is 800 feet in length and 45 feet in maximum height, with slopes of i to i and a grade of 5 feet per mile. Owing to the abundance of water procurable this cut was more cheaply excavated by the hydraulic process than it could have been by other means. At the far end of the cut the canal enters an old hydraulic washing which is utilized for its channel for a length of 2380 feet, after which it enters a rock cut 860 feet long, with a maximum depth of 45 feet and a similar cross-section to the cut first described. At the end of this rock cut the canal water is discharged into Dry creek, down which it flows for a distance of 6500 feet on a grade of 12 feet to the mile, and from which it is diverted by means of an earth dam 460 feet long. This dam has a maxi- 142 ALIGNMENT, SLOPE, AND CROSS-SECTION mum height of 23 feet with side slopes of 3 to i, and is riprapped to a depth of 3 feet on its upper face. At its south end the dam abuts on sandstone rock in which a wasteway is cut 50 feet widlw with its sill 4 feet below the crest of the dam, and which will dis- charge back into the creek 180 feet below the toe of the dam. Between the wasteway and the end of the dam is a waste-gate which it is intended shall be used in the time of freshets, for Dry creek has a maximum discharge of 4000 second-feet and, as the freshets are quick and violent, a large wasting capacity is neces- sary. These waste-gates are ten in number, each 3 feet wide in the clear and 10 feet in depth. They fall automatically outward or down-stream, being hinged at the bottom to a concrete floor laid on the bed-rock, and when raised they are attached by chains to the piers. For about a mile below Dry creek the canal is excavated in heavy, sandy loam, in which it has a bed width of 30 feet, with slopes 2 to i, a depth of 10 feet, and a grade of ij feet per mile. At the end of this excavation the canal crosses Dry creek in a flume 62 feet in height and 450 feet long, after crossing which the canal enters a series of three tunnels, the cross-sections of which are nearly similar to that of the first tunnel, while they are excavated in a tufa and sandstone which will require no timber- ing. The first tunnel is 211 feet in length, the second 400 feet, and the third 400 feet in length, while they are separated by short, open cuts excavated in hardpan and clay, which are respectively 250 and 300 feet in length. The last tunnel discharges into Delaney gulch, which is crossed by constructing a high bank or earth dam below the canal, the total length of which is 180 feet, its maximum height being 40 feet and its top width 20 feet. The volume of discharge of this gulch is so trifling that it was unneces- sary to provide a wasteway or escape at this point. Immediately after crossing the gulch the canal enters a cut 8 feet in maximum depth, with the same cross-section and grade as the first cut and having a length of 3300 feet. The canal is then widened to a bed width of 35 feet and depth of 10 feet, and is given a grade of i foot per mile. At the end of a mile and a half Peasley creek is crossed on a trestle and flume 60 feet in height and 360 feet long, EXAMPLE OF CANAL ALIGNMENT 143 the waterway on which is 20 feet wide and 7 feet in depth. This flume is provided with an escape constructed in its bottom and dis- charging into two small sloping flumes which lead the water down into the bed of Peasley creek (Article 215). At the end of the flume the main canal is reached and traversed for a distance of 1 1 miles, in which are two rock cuts, each 3000 feet long and respectively 20 and 30 feet wide on the bottom, depth of water yj feet, and grade 5 feet per mile. The remainder of this length of the canal varies in cross-section according to the soil, but most of it has a bottom width of 70 feet and depth of water of 7^ feet, slopes 2 to i, and a grade of i foot per mile. The main canal as outlined above consists for the 18 miles of its length of a purely diversion channel, the object of which is to bring the water to the irrigable lands included within the area of the Turlock district. At the terminus of this diversion line the canal begins at once to do duty by watering the lands, and below this point the main line is divided into four main branches, each of which has a bottom width of 30 feet, depth of water 5 feet, and grade of 2 feet per mile, their aggregate length being 80 miles. In addition to these main branches minor distributaries, having a total length of 180 miles, lead the water to each section of land. The discharge of the branches is so designed as to give a uniform velocity of 2^ feet per second, in order that any matter carried in suspension will be held up until deposited on the agricultural lands instead of in the canals. 148. Examples of Canal Alignment, Santa Ana Canal. A typical American alignment is that of the Santa Ana canal, diverted from the Santa Ana River above the head of the San Bernardino valley, California. This canal is interesting because of the care exercised in making the preliminary and location surveys for the difficult diversion line and for some interesting details of construction, chiefly in the flumes, siphons, and sand- boxes. The Santa Ana canal is designed to irrigate 45,000 acres in the northern part of San Jacinto valley, which is separated from the canal head by four main divides between the Santa Ana River, Mill creek, Yucaipe, Timoteo, and San Jacinto creeks. Through 144 ALIGNMENT, SLOPE, AND CROSS-SECTION a low neck in the higher ridge immediately north of San Jancinto valley the irrigating company had previously built Moreno tun- nel, 2320 feet in length, and of the capacity desired. This tunnel had been well lined with brick and plastered with cement and therefore became a controlling factor in the location of the align- ment from the headworks chosen. The source of water-supply is the natural flow of the Santa Ana River reinforced by the Bear valley storage reservoir in the San Bernardino mountains. The country between the tunnel and the point at which the Santa Ana River leaves the mountains in a canyon at an elevation of 1850 feet is exceedingly broken. The air-line between these two points is 12 miles, while a grade contour connecting them would be 42 miles in length. The site of the headworks is in a solid rock point of the canyon side where the river-bed has an elevation of 2320 feet. The diversion line was designed to carry 240 second-feet of water for the first portion of the line, and thereafter 300 second-feet to a reservoir site on the line of the work, after which it will diminish to 200 second-feet to the Moreno tunnel, so that the latter figure represents the maximum volume which will be carried for direct irrigation. The intake of the canal is a tunnel 220 feet in length through a vertical point of rock. The tunnel debouches at a point where a side canyon enters, and to avoid this the canal is built into the hill as a walled cutting, over which the side torrent is carried. From this point the canal rapidly " climbs " the cliffs and mountain sides, for the canyon bed drops away at the rate of 125 to 1 60 feet a mile, and on its line the tunnels, flumes, and pipes are given hydraulic gradients averaging less than 10 feet per mile. In the course of this line nine spurs are pierced by tunnels having an aggregate length of 4329 feet; three canyons are crossed by pressure pipes or siphons having a total horizontal length of 2127 feet; there are sixteen stretches of flume having an aggregate length of 14,100 feet; one piece of walled canal 152 feet in length; and eight masonry walled structures, as sand gates, junction bays, and escapes, having a length of 213 feet. In addition there are thirty-nine structures in the nature of trussed girders or combina- 10 146 ALIGNMENT, SLOPE, AND CROSS-SECTION tion Fink truss spans resting on timbers, piers, and masonry footings with an aggregate length of 3345 feet, besides which there are eight stretches of canal having a total length of 8214 feet, lined with rubble in mortar. The largest stream encountered on the completed part of the diversion line is Mill creek, which is crossed in a flume carried on a steel bridge 1072 feet in length (Plate II). The tunnels are sometimes in solid rock, when only the water channel is masonry-lined to produce a smooth surface, and at other times in loose material, when the entire surface is lined. These tunnels are 5 feet 9 inches in maximum height, and 5 feet 3 inches wide, with a curved invert below and an arched roof above. The walled canal has a cross-section practically the same as the water channel of the tunnel. The lined canal has a peculiar cross-section, the essential point of which is similar to that of the tunnel and the flumes, namely, an unusual depth in proportion to width (Fig. 21). The flumes are of wood and of the kind which may be called the stave and binder combination, consisting of wood bound together and held in a rounded bottom, straight- sided form, by steel ribs and binding rods, acting in conjunction with wooden yokes or ties across the top (Plate III). The pipe lines and inverted siphons are likewise of wood, and are con- structed of staves 2 inches in thickness, 52 inches internal di- ameter, with carrying capacities each of 120 second-feet, two parallel pipe lines being used on the main line, and they are of the common wooden stave and circular binder-rod pattern (Art. 233). The first sand-box or escape bay (Fig. 82) is located 700 feet from the initial point, while others are planned for different points low r er down on the works, should such prove necessary. This first sand-box is 60 feet long by 13 feet wide, and its lower end slopes transversely so that it is 7.3 inches deep on the upper side and 10.6 deep on the lower or discharging side, and it is so con- structed as to cause a slacking of the velocity and settlement of sediment at this point. There are six wasteways or escapes in that portion of the diversion line which is now built four at the upper ends of tunnels 3, 4, 5, and 6 respectively, and at distances of 3200, 6350, 8840, and 1 2, 930 feet from the intake. X yi 148 ALIGNMENT, SLOPE, AND CROSS-SECTION 149. Velocity, Slope, and Cross-section. One of the first considerations in designing a canal system is the quantity of water which the main line and its branches are severally to carry. This is chiefly dependent on the areas which they will command and the water duty. These determined, the alignment and construction are affected most by the slopes and cross-sections necessary to discharge the quantities required at given velocities. The three factors, velocity, slope, and cross-section, are nearly related and are interdependent one upon the other. Having FIG. 18. Tunnel Portal and Lining Truckee-Carson Canal, Nevada. determined the discharge required, the carrying capacity for this quantity can be obtained by increasing the slope and con- sequent velocity and diminishing the cross-sectional area; or by increasing the cross-sectional area and diminishing the velo- city. The determination of the proper relation of cross-section to slope requires the exercise of considerable judgment. If the material in which the excavation is to be made will permit, it is well to give a high velocity, as the deposition of silt and the growth LIMITING VELOCITY 149 of weeds are thus reduced to a minimum. A steep slope may result, however, in bringing the canal to the irrigable lands at such an elevation that it will not command the desired area. Again, it may be inadvisable to give too great a cross-section if the construction is in sidehill or in rock, or other material which is expensive to remove. Other things being equal, the correct relation of slope to cross-section is that in which the velocity will neither be too great nor too slow, and yet the amount of material to be removed will be reduced to a minimum. Where the fall will permit, the slope of the bed of the main canal should be less than that of the branches, which should be less than that of the distributaries and laterals, the object being to secure a nearly uniform velocity throughout the system, so that sedimentary matter carried in suspension may not be deposited until the irri- gable lands are reached. 150. Limiting Velocity. In order that the proper slope may be chosen, one which will produce a velocity that shall not cause silt to be deposited on the one hand, or erode the banks on the other, the amount of such velocities for different soils should be known. In a light, sandy soil it has been found that a surface velocity of from 2.3 to 2.4 feet per second, or mean velocities of 1.85 to 1.93 feet per second, give the most satisfactory results. It has been discovered that velocities of from 2 to 3 feet per sec- ond are ordinarily sufficiently swift to prevent the growth of weeds or the deposition of silt, and, other things being equal, this velocity is the one which it is most desirable to attain. In ordinary soil and firm sandy loam velocities of from 3 to 3^ feet per second are safe, while in firm gravel, rock, or hardpan the velocity may be increased to from 5 to 7 feet per second. It has been found that brickwork or heavy dry-laid paving or rubble will not stand velocities higher than 15 feet per second, and for greater velocities than this the most substantial form of masonry construction should be employed. 151. Grades for Given Velocities. The grade required to give these velocities is chiefly dependent on the cross-sectional area of the channel Much higher grades are required in small than in large canals to produce the same velocity. The velocity 150 ALIGNMENT, SLOPE, AND CROSS-SECTION which is required being known, the grade can be ascertained from Kutter's or some similar formula. In large canals of 60 feed bed width or upwards, and in sandy or light soil, grades as low as 6 inches in a mile produce as high velocities as the material will stand. In more firm soil this grade may be increased to from 12 to 1 8 inches to the mile, whereas smaller channels will stand slopes of from 2 to 5 feet per mile, according to the material and dimensions of the channel. 152. Examples of Canal Velocities and Grades. On the Ganges canal, the bottom width of which is 170 feet and the depth 7 feet, a slope of 14 inches per mile given in sandy soil pro- duces such a velocity that the current just ceases to cut the bank or to deposit silt, showing that this is the correct slope for that canal and material. In another portion of the same canal slopes of from 15 to 17 inches have been found too great, and much damage has been done to the banks. A velocity of 3 feet per second given to the Soane canal is found too great for the mate- rial, as much damage was caused by erosion. Careful observa- tions of the slope on the Ganges canal show that a current appar- ently perfectly adjusted to light, sandy soil was produced by a surface velocity of about 2.4 feet per second, or a mean velocity of about 1.9 feet per second. In one of the distributaries in sandy soil having some clay in it a mean velocity of 1.93 feet per second caused slight deposits of silt, but did not permit the growth of weeds. On the western Jumna canal silt was deposited in small quantities with a velocity of from 2 to 2.75 feet per second, while in sandy soil the latter velocity was the highest permissible for non-cutting of the banks. In the light, sandy -loam soils of the San Luis valley in Colo- rado, a slope of 6 inches to the mile given on the Citizens' canal has proven very satisfactory. So low a slope as this is possible, because the water is comparatively free of silt and there is little chance of its deposition, while the temperature is so low that there is little likelihood of the growth of weeds affecting the canal bed. Perhaps the highest grade on any canal is that on a short portion of the Del Norte canal in Colorado, where the fall is 35 feet per mile through a rock-cut. On several miles of this canal CROSS-SECTIONS 151 the grade is 8 feet per mile, but after it reaches the earth soil in the valley it is reduced to i in 2112. On the Interstate canal, Wyo.-Neb., built by the Reclama- tion Service, with a bed width of 34 feet and depth of 10 feet, a slope of .00017 or about n inches per mile produces a velocity of 2.86 feet per second, with discharge of 1407 second-feet. This velocity is best suited to the light soil in which the canal is ex- cavated. Further along for diminished discharge and bed- width of 25 feet, the same depth and slope being maintained, the velocity is as high as 2.78 feet without doing damage. 153. Cross-sections. The most economical channel is one with vertical sides and a depth equal to half the bottom width; but this form is only applicable to the firmest rock, therefore trapezoidal cross-sections are always employed in other materials. The best trapezoidal form is one in which the width of the water surface is double the bottom width and equal to the sum of the side slopes, and the trapezoidal section which gives the maximum discharge for any area of waterway is semi-hexagonal, or one in which the hydraulic mean depth equals half the depth of water. Such cross-sections as these, however, would call for an unusually compact material. In the interest of economy the side-slopes above water-level should be as steep as the nature of the soil will permit. As before shown, the cross-sectional area depends on the velocity and slope and their relation to the quantity of water to be discharged. The exact form of this cross-section is dependent on the topography and the material through which the canal passes. The greater the depth the greater will be the velocity and consequent discharge for the same form of cross-section. Very large canals, such as some of those in India, have been given a proportion of depth to width similar to that of the great rivers. This proportion has been found to be most nearly attained when the bed width is made from 13 to 16 times the depth. In sidehill excavation the greater the proportion of depth to width the less will be the cost of construction (Art. 143), and in all rock and heavy material it is desirable if possible to make the bottom width not greater than from 2 to 3 times the depth. Such a pro- portion as this, however, is rarely practicable. In a large canal, 152 ALIGNMENT, SLOPE, AND CROSS-SECTION one for instance having a capacity of 2000 second-feet, with a velocity of 2 feet per second, the cross-sectional area would be 1000 square feet. If the proportion of 2 to i were maintained, this would call for a bed width of about 45 feet to a depth of 22 J feet. Such a depth as this, unless in very hard material, is readily seen to be absurd, as the cost of construction would be greatly increased over that of a canal having a lesser depth. In this case a fair proportion would be 125 feet bed width to about 8 feet depth. A rule which has been proposed, and which will prove fairly good on moderate sized canals, is to make the bottom width in feet equal to the depth in feet plus one, squared. This, however, will not apply to large canals and is not altogether true for any size of canal. 154. Form of Cross-section. The cross-section of a canal may be so designed that the water may be wholly in excavation, wholly in embankment, or partly in excavation and partly in embankment (Fig. 19). The conditions which govern the choice of one of these three forms are dependent primarily on the align- ment and grade of the canal, and secondarily on the character of the soil. For sanitary reasons it is sometimes desirable to keep a canal wholly in cutting, for if the material of which the banks are constructed is porous the water may filter through and stand about in stagnant pools on the surface of the ground. If the material is impervious to the passage of water and will form good firm banks, it may be well to keep the canal in embankment where possible, though this may necessitate the expense of bor- rowing material. In order to lessen the cost of construction, it is desirable, where the surface will permit, to keep a canal half in cut and half in fill, thus reducing to a minimum the amount of material to be moved. Ordinarily the surface of the ground is irregular and undulating, and in order that the grade may be maintained the canal will of necessity be sometimes wholly in cut and at others wholly in fill, and at others at all intermediate stages between these. Where the canal is wholly in embankment there is always considerable loss from leakage, and consequent danger of breaches. Where the canal is wholly in cut, care must be taken to discover the character of the soil in which the excava- FORM OF CROSS-SECTION 153 tion is to be made, as rock may be encountered at a few inches below the surface, thus increasing the cost of excavation, or a sandy substratum may be discovered which would cause exces- sive seepage. Most main canals follow the slope of the country on grade contours running around sidehill or mountain slopes. In such cases it is necessary to build an embankment on one side only, when the cutting will be entirely on the upper side. If there is a gentle slope on the upper side, and an embankment on that side, SIDELONG GROUND W.L ABOVE C.L. 4V W.L. Majr require Puddle Wall as indicated SOD REVETMENTS WITHOUT BERMS- W.L BELOW C.L, Ground WITH BERMS- W.L. BELOW C.L FIG. 19. Various Canal Cross-sections. it is desirable to run drainage channels at intervals from this embankment to keep the water from making its way through it to the canal. These drainage channels may be taken through the embankment into the canal, or may be led away to some natural watercourse. In designing the cross-section of a canal it may be desirable to give a berm, and this may be above or below the water-level (Fig. 19). Ordinarily the berm is left at a level with the ground surface, though it may be constructed in excavation or embank- ment an unusual practice, however. The chief object of the berm is to provide against the destruction of the slopes in the lower part of the banks by giving a terrace or bench on which the 154 ALIGNMENT, SLOPE, AND CROSS-SECTION upper bank may slide, provided it fails to maintain the slope originally given ; it also serves in some cases as a tow-path or foot- path. The width of berm varies between 2 and 6 feet, and it is common to change the slopes at the point of junction between cut and embankment, making the slope of the latter a little flatter than that of the former. 155. Side Slopes and Top Width of Banks. In large canals it is always desirable to have a roadbed on at least one bank, and the width of this will determine the top width of the bank. The inner surfaces of the canal are usually made smooth and even, while the top is likewise made smooth, with a slight inclination to the outward to throw drainage away from the canal. The inner slopes of the banks vary in soil between i on i and i on 4, according to the character of the material. In firm clayey gravel or hardpan slopes of i on i are sufficiently substantial for nearly any depth of cutting or embankment. On the Turlock canal in California is a cut 80 feet in depth with side slopes of i on i, while on the Bear River canal in Utah are similar slopes in disintegrated shale and coarse gravel. In ordinary firm soil mixed with gravel or in coarse loamy gravel slopes of i on i J are sufficient. In firm soil and slightly clayey loam slopes of i on 2 may be required; on lighter soils these slopes may be increased until the lightest sand is reached, when slopes of i on 3 or 4 may be necessary. The top width of the canal bank is generally from 4 to 10 feet, according to the material and depth, and whether or not the water is in embankment. If there is to be no roadway on the top of the embankment, and the surface of the water does not rise more than a foot or so above the foot of the embankment, a top width of 4 feet is sufficient. Where the depth of water on the embankment is greater, this width should be 6 or 8 feet, and if the soil is light it should be at least 10 f eet. It is sometimes neces- sary to build a puddle wall in the embankment, or to make a puddle facing on its inner slope where is it particularly pervious to water. The same effect is obtained by sodding or causing grass to grow on the bank. It may be well to puddle the entire bank during construction by laying and rolling it in layers. The CROSS-SECTION WITH SUBGRADE 155 carrying capacity of a canal should be so calculated that the sur- face of the water when in cut shall not reach within one foot of the top of the ground surface. In fill the depth of water carried should be such that the surface shall not rise higher than within ij feet of the top of the bank, while if the fill is great it is often unsafe to let the water rise within 2 feet of the top of the bank. 156. Cross-section with Subgrade. In the light soils of the San Luis valley in Colorado and in Kern valley in California FIG. 20. Cross-section of Galloway Canal in Sand, showing Subgrade. it has been found advantageous to dig a subgrade i to 2 feet below the original canal bed. The cross-section gradually approaches that of the ellipse and tends to keep the current in the centre of the channel,' and to keep up its flow with the least exposure to friction and seepage when the volume of water in the canal is low. The subgrade (Fig. 20) is given by practically designing the canal as if it were to have a trapezoidal cross-section with berm, and FIG. 21. Typical Section of Lined Canal. Reclamation Service. then evening off the slope by removing the berm and continuing the slope from the bottom of the canal toward the centre. In such construction as this it has sometimes been found desirable to give the bank practically no top width, simply rounding it off from the innner to the outer surface, where the waste is carelessly scattered, allowing the soil to assume its natural slope. 157. Lined Canal. There are many advantages to be gotten from lining a canal channel excavated in earth, especially where 156 ALIGNMENT, SLOPE, AND CROSS-SECTION the soil is porous and water valuable. In many portions of India and in Europe, particularly where the canal passes through sandy soil, or where a high velocity is desirable or unavoidable, the canals are lined for portions of their lengths, usually with sand placed, dry-laid stone paving. In some portions of South- ern California canals are similarly lined, though there, owing to the high value of water, it is customary to line them with rubble paving set in cement or mortar in order to prevent loss by absorption. The Reclamation Service has lined portions of many of its canals with concrete, particularly those in the Southwest where water is scarce and valuable. Such linings have FIG, 22. Cross -section of Lined Channel, Santa Ana Canal. been used chiefly in sandy sections and through crevised rock sections, the concrete being generally 6 inches in thickness. When a canal is thus lined its cost is in the end not greatly in- creased, for the saving in cross-sectional area due to the ability to increase the velocity, as well as the great saving of water in sandy and gravelly soils, largely offsets the cost of lining; moreover, it is possible to give a lined channel a cross-section more nearly approaching that called for by theory (Art. 153), namely, a greater relative depth to width, because of the stability added to the banks by the lining. Experiments conducted by B. A. Echeverry in Southern California to determine relative percolation from lined and un- lined ditches showed the following relative efficiency ratios. Using unlined earth channels = i.o; heavy oil lining, 3^ gals, per sq. yd.,e = 2.o; clay puddle, e = 1.8; cement concrete 3" thick, e = 7. 2. LINED CANAL 157 The cost of the oil lining was n cents per sq. yd; of the concrete lining 67 cents. A typical paved lining is that given the Santa Ana canal in California, in alluvial soil, sand, and gravel. This canal is FIG. 23. Concrete Lining, Truckee-Carson Canal, Nevada. almost wholly in excavation (Plate III) ; the water is permitted a velocity of 5 feet per second, and the depth is as great as 7^ feet for a bed width of 6J feet and top width of 12 J feet (Fig. 22). In order that the lining may have a stable footing and the bottom 158 ALIGNMENT, SLOPE, AND CROSS-SECTION be less liable to bulge, this is curved downward with a versed sine of ij feet, forming thus a subgrade of that depth. The banks are 2 feet higher than the water surface, and are built on side slopes of 2 on i. The earth excavation had a bottom width of 7 feet and the same slopes as above, and was trimmed at bottom to the lining, which consists of cobbles and bowlders laid in mortar and grouted and faced with cement plaster. On the Tieton canal, Washington, of the Reclamation Service, the lined sections in earth and loose rock are semicircular (Fig. 23). The lining is of reinforced concrete, 4 inches in 1 1 4-4|: ( L \L|j$3Iortar Joine ', 1 ^Jute * ; v DETAIL OF JOINT i Square, r 6'2 FIG. 24. Reinforced Concrete Canal Lining. Tieton Canal, Wash. thickness, and extends i' 10" above the centre of the circular section. The upper edge is cross-braced every 2 feet by a 4-inch square scantling. The diameter of the lined section is 8' 2", depth of water 5' 3", area 36 square feet, velocity 9 feet per second, and discharge 326 second-feet. By comparison the unlined section of the same canal has an area of 120 square feet and velocity of 2.5 feet per second. Below the Assuan dam in upper Egypt is a canal built in shifting sand by erecting on the surface a semicylindrical flume of sheet steel and then banking the sand against it to the level of its top. This steel canal is 19' 8" in diameter with i' 8" straight SHRINKAGE OF EARTHWORK 159 sides at top, making a total depth of 21' 4". The inner shell of \" steel plates is riveted to outer semicircular ribs of heavy T-rail placed 2 y centres. The top is braced with 3" flat and 3" x 2 y angle iron (Fig. 25). The canal rests on a wall of concrete beneath its centre and has expansion joints every 330 feet. 158. Shrinkage of Earthwork. It is well known that when Wro't Steel Rails 2 3 Ion* Angle In 5 lengths on Atmospheric aide jointmarned''6" CROSS SECTION ON LINE A-B FIG. 25. Plan and Section, Sheet Steel Flume, Upper Egypt. soil which has been removed from an excavation is formed into embankment it settles or shrinks in volume. That is to say, the embankment soil occupies a less space than it did in the ground; while, on the contrary, rock or loose stone occupies a greater space, depending on the dimensions of the fragments. The percentage of this shrinkage differs for different soils. The i6o ALIGNMENT, SLOPE, AND CROSS-SECTION following list gives an idea of the amount of this shrinkage for different soils: Sand, about 10 per cent; in other words, after excavation sand will ultimately occupy 10 per cent less space than it did in its natural bed. Sand and gravel shrink 8 per cent. Earth, loam, and sandy loam shrink 10 to 12 per cent. Gravelly clay shrinks 8 to 10 per cent. Puddled clay and puddled soil shrink 20 to 25 per cent. FIG. 26. Rock Cross-section, Turlock Canal. Rock expands or increases in volume from 25 per cent in the case of small or medium fragments and road -met ailing to 60 or 70 per cent in large fragments carelessly thrown. 159. Cross-section in Rock. In firm rock it is desirable ry'Rubble SECTION IN ROCK a =87.7 p=15.4 r= 2.44 w=.oi2 s=.oom Q=300 B FlG. 27. Rock Cross-section; A, Bear River Cana.; B, Umatilla Canal. CROSS-SECTION IN ROCK 161 SECTION "A-A" R|,G Think to make the proportion of depth to width about as i to 2, with side slopes of about 4 on i. In less firm rock lighter slopes and a less proportional depth are desirable. In friable shale, as on the Tur- lock canal in California, a different cross-section is desirable (Fig. 26). In this instance a retaining- wall of hand-placed stones, with an outer slope of 4 on i and a top width of 2 J feet, is built on the lower side. Inside this is a puddled earth bank, riprapped on the water surface with 10 inches in thickness of loose stone. The upper or excavated slope is about 2 on i, the depth 10 feet, and the bed width 20 feet. The slopes have proven too steep, as the friable shale has disin- tegrated and caused the made banks and the sides of excavated banks to crumble and fall. On the Bear River canal in Utah, and the Umatilla canal, Oregon, the cross- sections shown in Fig. 27, were given in order to avoid too much ex- cavation in extremely rocky sidehill, a retaining-wall being built as the lower or embankment wall of the canal. The transition from rock to earth must be made with great care lest erosion take place in the latter. For the same volume of discharge the earth section usually has greater breadth, less depth and diminished slope to reduce the velocity. As a rule the canal bottom and sides are riprapped where the change in section occurs, as illustrated (Fig. 28) on the Umatilla canal, Oregon, of the Reclamation Service. Conoreto 6'thlok FIG. 28. Transition from Rock to Earth Cross-section, Lined Canal, Reclamation Ser- vice. IT CHAPTER X HEADWORKS AND DIVERSION WEIRS 1 60. Location of Headworks. The head works of a canal are generally placed where the stream emerges from the hills. At such a point the slope of the country and of the stream is steep, making it possible to conduct a canal thence to the irrigable lands with the shortest diversion line. Moreover, the width of the chan- nel of the stream is generally contracted, and it flows through firm soil or rock, thus permitting a reduction in the length of the weir and in the cost of its construction and maintenance. As one of the principal objects of the diversion weir is to raise the level of the water and force it into the canal head, one of the con- trolling factors in determining the site of the headworks is the height of the weir. This again is dependent on the effect of vari- ous weir heights on the location and cost of the remainder of the headworks and of the diversion canal. Also on the flood dis- charges, amounts of sediment carried by the stream, the founda- tion, the depth of water in the canal, and similar factors. When the volume of flood water occurring in the stream is great it is sometimes necessary to locate the headworks at a point where the width between banks is greatest, in order that the depth of water flowing over the weir may be reduced to a minimum and danger of its destruction reduced accordingly. While such a location may be the most permanent, it is also most costly for con- struction. The site of the headworks should be such that the most permanent weir can be constructed at the least cost, and yet they should be so located that the diverting canal can be conducted thence to the irrigable lands at a minimum cost. The location of the headworks high up on the stream is usually antagonistic to the last object, since it generally results in the canal having to encounter heavy rock-work and difficult construction until it gets away from the river banks. In selecting the site for the head- 162 CHARACTER OF HEADWORKS 163 works it is desirable to choose a portion of the stream in which its channel is straight and its cross-section uniform for some distance. If the site is in a wide portion of the stream, the weir should be located at a point where the stream shows no signs of shifting its channel. 161. Character of Headworks. The headworks of a canal consist of 1. A diversion weir, in which is usually built 2. A set of scouring sluices; 3. A regulator at the head of the canal for its control; 4. A wasteway for the relief of the canal below that point. Sometimes to these are added river training or regulating works for the protection of the banks of the stream above and below the obstruction formed by the headworks. Too careful attention cannot be given to an examination of the stream at the point of diversion. Soundings and borings should be made to ascertain the depth of water and character of the foundation. The velocity of the stream and its flood heights should be studied, as should the material of which the banks are composed. Where possible, a straight reach in the river should be chosen for the location of the headworks in order that the stream shall have a direct sweep past them, thus reducing to a minimum the deposition of silt in front of the regulating gates. If possible, a point should also be chosen where the velocity in the river will not exceed that in the canal, so that the deposition of silt shall be further reduced. There has been too great a tendency in American construc- tion to build works of a temporary and transient character. The headworks of a canal are the most vital portions of its mechanism ; they are to a canal system what a throttle-valve is to a locomotive. Through them the permanency of the supply in the canal is main- tained, and any injury to them means paralysis to the entire sys- tem. They should therefore be most substantially and carefully designed throughout. The employment of wood has been alto- gether too common in the United States. It is very well to make use of wood as a temporary makeshift until money and time can be found for substituting more substantial material. It may be generally laid down as a principle, however, that only iron and 164 HEADWORKS AND DIVERSION WEIRS masonry should enter into the construction of the head works. It is impossible to form wood, with the addition of little or no iron or masonry, into permanent and substantial headworks. Until recently the best and most abundant examples of substantial headworks were to be found in Europe and India. Now the works of the Reclamation Service furnish magnificent examples of modern reinforced concrete construction. In some cases it has been found unnecessary to construct diversion weirs as a part of the headworks of a canal. This has been the case especially where the discharge of the stream was great relative to the discharge of the canal, and only when a por- tion of the water in the stream was required. At the head of the Ganges and Jumna canals in India there are no permanent diver- sion works, the water being turned into the canal head by means of temporary structures of bowlders, or by means of training the water of the river so that it shall flow directly against the canal head. 162. Diversion Weirs. In this book the word weir as dis- tinguished from dam is generally employed to mean a structure intended for the impounding or the diversion of water and over which flood waters may safely flow. Thus weirs are usually built at the heads of canals for the diversion of the waters of the stream into their heads, while the surplus water is permitted to flow over the weir and to pass on down the stream. In some cases, however, dams over which it would be unsafe to permit flood waters to pass are used for the purpose of diversion, and a wasteway is. con- structed at one end of the dam for the passage of surplus waters. A weir across a stream is analogous to a bar and should be located and treated as such. If it is placed at the widest part of the stream, the cost of construction may be increased. In the great rivers of India and on the Colorado River at Yuma where diversion is made in the level and sandy plains below the hills and where permanent foundations cannot be obtained, weirs have generally been placed in the broadest reaches of the streams. (PL V.) In our own country diversion for canals has generally taken place in the foothills, and accordingly the narrower portions of the streams have been chosen for this purpose. CLASSES OF WEIRS 165 The integrity of weirs is in constant danger of destruction: i, by actual breaching by the force of the current; 2, by under- mining by the falling water; 3, by outflanking, especially where the banks are unstable or not protected by substantial wing-walh; 4, by undermining on the upper side by parallel currents owing to the weir not being at right angles to the course of the stream. This may be remedied by the building of suitable training works (Art. 191). 163. Classes of Weirs. Weirs may be divided into two classes according to the mode of building their foundations. Thus they may rest directly on some permanent material; or they may rest on some unstable material, as quicksand, gravel, or clay, in which case an artificial foundation of piles, caissons, or wells or blocks must be constructed. Where, in Western practice, a firm foundation has not been found piling has usually been employed. In India and Egypt wells or blocks are employed for foundations in unstable material. Foundations of the first class, viz., in rock or bowlders, are found in the foothills and at canyon exits, and where the slope of the stream-bed exceeds 8 feet per mile. Those of the second class are found in valleys and on the plains where the stream-bed has slopes less than 8 feet per mile. The most convenient classification of diversion weirs is accord- ing to the construction of their superstructures. These may be 1. Temporary brush or bowlder barriers; 2. Rectangular walls of sheet and anchor piles filled with rock or sand; 3. Open weirs; 4. Wooden crib and rock weirs; 5. Masonry weirs; 164. Brush and Bowlder Weirs. The simplest and crudest form of weir is the brush and gravel barrier, which was originally used by the Mexicans and is still employed in the West on minor streams. These weirs are formed by driving stakes across the channel and attaching to them fascines or bundles of willows from three to six inches in diameter at the butts, which are laid with the brush end up-stream, and are weighted with bowlders and 1 66 HE AD WORKS AND DIVERSION WEIRS gravel. More willow or cottonwood branches are laid on the top of these and again weighted with bowlders, this operation being continued until the structure is built to a height of three or four feet. Such structures are of the crudest character, can be built without any engineering knowledge or supervision, and are carried away by the first flood. 165. Rectangular Pile Weirs. These have been employed in wide sandy rivers like the Platte, in Colorado. They consist of a double row of piling driven into the river-bed, the two rows being about 6 feet apart, and the piles about 3 feet apart between centres. Between these is driven sheet piling to prevent the seep- age or travel of water through the barrier, and the upper portion of the structure is planked so as to form a rectangular wall the interior of which is filled in with gravel, sand, etc. Such walls are usually low, rarely exceeding 8 feet in height, and after the upper side is backed with the silt deposited from the stream they form substantial barriers which may last a few years. Such struc- tures cannot be employed where the flood height is great, as they would soon be undermined unless substantial aprons were con- structed. 1 66. Open and Closed Weirs. Diversion weirs may again be classified as open or closed. A closed weir is one in which the barrier which it forms is solid across nearly the entire width of the channel, the flood waters passing over its crest. Such weirs have usually a short open portion in front of the regulator known as the "scouring-sluice," the object of which is to main- tain a swift current past the regulator entrance, and thus prevent the deposit of silt at that point. An open weir is one in which scouring-sluices or openings are provided throughout a large por- tion of its length and for the full height of the weir. The advantage of the closed weir is that it is self-acting, and if well designed and constructed requires little expense for repairs or maintenance. It is a substantial structure, well able to with- stand the shocks of floating timber and drift; but it interferes with the normal regimen of the river, causing deposit of silt and perhaps changing the channel of the stream. Open or scouring- sluice weirs interfere little with the normal action of the stream, OPEN AND CLOSED WEIRS 167 and the scour produced by opening the gates prevents the deposit of silt, while their first cost is generally less than that of closed weirs The closed weir consists of an apron properly founded and carried across the entire width of the river flush with the level of its bed, and protected from erosive action by curtain-walls up and down stream. On a portion of this is constructed the super- structure, which may consist of a solid wall or in part of upright piers, the interstices between which are closed by some temporary arrangement. This portion of the weir is called the scouring- sluice. The apron of the weir should have a thickness equal to one-half and a breadth equal to three times the height of the weir above the stream-bed. During floods the water backed against the weir acts as a water cushion to protect the apron, and as the flood rises the height of the fall over the weir crest diminishes, so that with a flood of 16 feet over an ordinary weir its effect as an obstruction wholly disappears. A rapidly rising flood is more dangerous than a slowly rising flood, not only because of its greater velocity, but because it causes a greater head or fall over the weir as the water has not had time to back up below and form a water- cushion. For the same reasons a falling or diminishing flood is less dangerous than a rising flood. An open weir consists of a series of piers of wood, iron, or masonry, set at regular intervals across the stream bed and rest- ing on a masonry or wooden floor. This floor is carried across the channel flush with the river bed, and is protected from erosive action by curtain-walls up- and down-stream. The piers are grooved for the reception of flashboards or gates, so that by rais- ing or lowering these the afflux height of the river can be con- trolled. The distance between the piers varies between 3 and 10 feet, according to the style of gate used. If the river is subject to sudden floods these gates may be so constructed as to drop automatically when the water rises to a sufficient height to top them. It is sometimes necessary to construct open weirs in such manner that they shall offer the least obstruction to the waterway of the stream. This is necessary in weirs like the Barage du Nil, below Cairo, Egypt, or in some of the weirs on the Seine, in France, 1 68 HEADWORKS AND DIVERSION WEIRS in order that in time of flood the height of water may not be appre- ciably increased above the fixed diversion height. Should the height be increased in such cases the water would back up, flood- ing and destroying valuable property in the cities above. Under such circumstances open weirs are sometimes so constructed that they can be entirely removed, piers and all, leaving absolutely no obstruction to the channel of the stream, and in fact increasing its discharging capacity, owing to the smoothness which they give to its bed and banks. 167. Open Frame or Flashboard Weirs. A form of cheap open weir which has been commonly constructed in the West is the open wooden frame and flashboard weir. This type of struc- ture is used only on such rivers as have unstable beds and banks, where any obstruction to the ordinary regimen of the stream would cause a change in its channel. It consists wholly or in part of a foundation of piling driven into the river bed, upon which is built an open framework closed by horizontal planks let into slots in the piers. These weirs are constructed of wood, and are temporary in character, their chief recommendation being the cheapness with which they can be built in rivers the beds of which are composed of a considerable depth of silt or light soil. Two varieties of this weir are in common use. One which has been employed at the heads of the Del Norte, Monte Vista, and other canals in the San Luis valley of Colorado, is partly open and partly closed. An earth bank or dam is built for a portion of the way across the stream and of such height that it will not be topped by floods. The remainder of the weir consists of a framework of rough-hewn logs founded on piles with openings between into which horizontal planks or flashboards can be in- serted one at a time. A more common type of frame or flashboard weir is that em- ployed on the Kern River in California. (Plate IV.) An ex- ample of this is the weir at the head of the Calloway canal (Fig. 29), which consists of 100 bays, each separated by a simple open triangular framework of wood founded on piles, the width of each opening or bay being 4 feet. Two and one-half feet below the bed of the stream is a floor, with walls about 2 feet in height, 1 70 HEADWORKS AND DIVERSION WEIRS forming compartments filled with sand on which the waters fall. This apron is carried up- and down-stream for a distance of about 10 feet in each direction. The weir proper is formed of frames or trusses of 6 by 6 inch timber, placed transversely 4 feet apart. These frames consist of 2 pieces, the up-stream piece being 15 feet 2 inches long and set at an angle of 38 degrees, while the other supports it at right angles and is 9 feet 4 inches long. The lower FIG. 29. Cross-section of Open Weir, Galloway Canal. ends of these rafters thrust against two pieces of 6 by 2 inch timber running the whole length of the weir and nailed to the flooring. These frames are supported directly on anchor piles, one at each end joiced into the framing. These trusses are kept in vertical position by means of a footboard running transversely the entire width of the stream. On the up-stream face of the trusses planks or flashboards which slide between grooves formed by nailing face-boards on the trusses are laid on to the required height. This weir is 10 feet in height above the wooden floor, which is flush with the river bed . 1 68. Open Masonry Weirs, Indian Type. A substantial OPEN MASONRY WEIRS, INDIAN TYPE 171 NARORA WEIR- LOWER GANGES CANAL length 1260 metres ofSiver OKHLA WEIR-AGRA CANAL. Length DEHREE WEJR-SOANE CANAL Length 3825 metres OEZWARA WEIR - KISTNA CANAL. Length J150 metres. " -tr "*- 600IVERY WEIR. >%T'A:V< PLATE V. Cross-sections of Indian Weirs. 172 HEADWORKS AND DIVERSION WEIRS form of open masonry weir is that generally constructed on Indian rivers, where the banks and bed are of sand, gravel, or other unstable material. These weirs generally rest on shallow founda- tions of masonry, in such manner that they practically float on the sandy beds of the streams. The foundation of such a weir is generally of one or more rows of wells sunk to a depth of from 6 to 10 feet in the bed of the river, the wells and the spaces between the rows of wells being filled in with concrete, thus forming a masonry wall across the channel. A well or block is a cylindrical or rectangular hollow brick structure, which is built upon a hard cutting edge like a caisson, and from the interior of which the sand is excavated as it sinks. After it has reached a suitable depth it is filled with concrete, the whole depending for its stability on the friction against its sides. This form of construction is illus- trated in Plate V. The weir at the head of the Soane canals, which is typical of this class of structure, consists of three parallel lines of masonry running across the entire width of the stream, and_ vary ing from 2j to 5 feet in thickness. The main wall, which is the upper of the three and the axis of the weir, is 5 feet wide and 8 feet high, and all three lines of walls are founded on wells sunk from 6 to 8 feet in the sandy bed of the river. Between these walls is a simple dry stone packing raised to a level with their crests, thus forming an even upper surface. The up-stream slope is i on 3, and the down-stream slope i on 12, the total length of this lower slope being 104 feet, while the total height of the weir, including its foundation, is 19.3 feet. The Soane weir has a total length across stream of 12,480 feet, of which 1494 feet consists of open weir disposed in three sets of scouring-sluices (Fig. 30), one in the center and two adja- cent to either bank and in front of the regulating gates at the head of the canals. These scouring-sluices consist of three parts the foundation, the floorway or apron, and the superstructure. The floor is deep and well constructed of substantial masonry, and is continued for a short distance above the weir and for a considerable distance below it. It is 90 feet wide parallel to the river channel, and is founded on wells, the ashlar pavement of OPEN MASONRY WEIRS, INDIAN TYPE the floor being 15 inches thick in the bottom of the scouring-sluices between the piers, and 9 inches thick over the remainder of the apron. Up-stream from the sluice floor for a distance of 25 feet is a line of wells sunk to a depth of 16 feet as a curtain- wall to the apron. Twenty-five feet down-stream from the flooring of the sluices is a similar line of wells formed into a wall, and the spaces Elevation. CROSS SECTION OF WEIR 30' - *rt[ TO' FIG. 30. Half-elevation, Plan, and Section, Soane Weir, India. between these two curtain- walls and the main ashlar flooring of the sluiceway is packed with dry-laid bowlders and rubble cov- ered with a pavement of masonry 9 inches in thickness. Down- stream from the lower curtain-wall a paving of large bowlders stretches for 50 feet further, the whole of this sluice floor parallel to the river channel being 200 feet in length. This is a typical 174 HEADWORKS AND DIVERSION WEIRS floor to an Indian open weir or sluiceway, on top of which, in line with the center of the crest of the weir, are built up masonry piers at intervals of from 6 to 12 feet apart, grooved for the recep- tion of planks or flashboards, or closed with lifting or automatic drop-gates. A peculiar form of open weir is that constructed at the head of the Sidhnai canal in India. At the point where the weir is built the bed of the river gives a good clay foundation for a short dis- tance from either bank, while in the center of the channel the bed FlG. 31. Elevation and Cross-section of Sidhnai Weir, India. is of sand for a considerable depth. Sheet piling 10 feet long was driven into the sandy bed of the river to prevent excessive per- colation. On these piles (Fig. 31) rests a series of piers which support masonry arches, the piers being 16 feet between centers and filled between with clay. Above this masonry arch is built a continuous wall across the entire width of the stream from 4 to 6 feet wide on top and from 3^ to 8J feet in height. Over this wall, parallel to the channel of the river, is built a masonry floor- ing, the upper slope of which is i on 3, while its lower slope varies between i on 5 and i on 10, according as it is near the center or ends of the weir. The total width of this floor parallel LACUNA WEIR, COLORADO RIVER 175 to the channel of the stream is 12 feet above the axis of the weir and 40 feet below it, the lower toe terminating in a series of wells. On top of this flooring are erected a series of piers 23 feet apart between centers, and projecting 2\ feet up-stream from the cen- tral wall and 9 feet down-stream, their total length parallel to the channel being 15 \ feet and their width on top 6 feet. The crests of these pillars are 6 \ feet in height above the crest of the floor, while the total height of the weir above the summit of the pile foundation is about 21 feet. It will thus be seen that this weir offers a clear waterway across the entire channel, obstructed only by the piers, which are 6J feet above the stream-bed. The open- ings between these piers are closed by means of needles, which consist of a heavy beam laid along the crest wall from pier to pier, against which rest wooden sticks or needles inclined at a slight angle. These needles are each 7 J feet long by 5 inches wide and 3J inches in thickness, and are laid along the upper face close together so as to form a close paling or barrier when in place. 169. Laguna Weir, Colorado River. This weir was con- structed across the Colorado River at a point where the bed of that river is composed of sand too deep to permit of founding the same upon solid rock. The weir was designed on lines similar to those on which like structures have been built in India and Egypt. (Art. 168.) Its maximum length is over 4900 feet, extreme height above stream-bed 19 feet. It consists of three walls across the river-bed (Fig. 32 ), each 5 feet wide, one on the crest line 19 feet high, the next 57^ feet down-stream, 14 feet high, the third 93^ feet further down-stream, 7 feet high. On the up-stream face are large rubble blocks carefully placed on a slope 2 to i from the crest to the stream bed. Down-stream between the walls is a loose rock-fill of large blocks surfaced with a paving 24 to 36 inches deep of hand-laid blocks. The slope of the upper surface is 12 to i. Below the lower concrete wall is an apron of large rubble blocks, the whole resting on the sand-bed of the river. Under the crest- line wall is a row of sheet piling driven 10 feet below the stream-bed. This is built up of three 2 1 2-inch Oregon pine planks, thoroughly spiked and clinched by one spike per i 7 6 HEADWORKS AND DIVERSION WEIRS square foot, each of wrought iron 7 inches long and 3 inches in diameter. These piles are sheared obliquely to make them mesh closely when driven. The rock-fill is composed of stone of a regular shape and size, the run of quarry, at least two-thirds of which are not less than 1000 pounds in weight, and one-half of these not less than 4000 pounds in weight, the whole dumped into place by dropping from an elevation of not less than 5 feet. Small stones and chips were thrown into the open spaces be- tween the larger slopes, and the whole levelled off before placing pavements. All paving-blocks are roughly rec- tangular, none less than 2 feet in length, of which 10 per cent are 3 feet long, the breadth not less than i foot and the thickness not less than J foot. This paving is set by hand, closely packed and well tamped, no stone projecting over 3 inches above the piling and surface, and no portion laid under water. In the walls of the weir, as well as in the walls and piers of the regulators and sluiceways, only the best concrete was used, consisting of Portland cement, i barrel to 3 barrels of \- inch mesh river-sand and 7 barrels full of gravel or broken stone, the latter not exceeding in dimensions one-half the thickness of the wall in which it was used. 170. Movable Iron Weirs, French I 8 i; ROLLING LIFT WEIR 177 Type. The weirs on the River Seine in France differ materially from the open Indian weirs. They consist of a series of iron frames of trapezoidal cross-section, somewhat similar in shape to the frames of the open wooden flashboard weirs of California. On these frames rest a temporary footway, and on their upper side is placed a rolling curtain shutter or gate which can be dropped so as to obstruct the passage of water across the entire channclway of the stream, or can be raised to such a height as to permit the water to flow under them. In times of flood the FIG. 33. View of Open Weir on River Seine, France. curtain can be completely raised and removed on a temporary track to the river banks, the floor and track can then be taken up, leaving nothing but the slight iron frames, which scarcely impede the discharge of the river and permit abundant passage- way of the floods over, around, and through them (Fig. 33). 171. Rolling Lift- Weir. An interesting type of movable dam was recently constructed at Schweinfurt, Bavaria. As described and illustrated in Engineering News (Fig. 34) it consists of a heavy, hollow, riveted, sheet-steel cylinder, 6.5 feet in diameter and 121.3 f eet m length, resting on top of a masonry weir. At each end of the upper periphery is fixed a toothed wheel which 178 HEADWORKS AND DIVERSION WEIRS meshes in an inclined rack built in each abutment. The steel is i.i inches thick, built in sections 9.8 feet long, with a single longitudinal joint. The transverse joint ends are butt-joints, and each section is reinforced in the middle by a brace. This cylinder is water-tight excepting two chambers in the upper end of each extremity. When the down-stream level does not rise more than 3 feet above the bottom of the dam, the weight of the cylinder is sufficient to counteract the pressure, but when FIG. 34. Rolling Lift-weir, Schweinfurt, Bavaria. the back-water level rises above this it enters the two chambers, thus adding to the stability of the cylinder. The racks are inclined at an angle of 45 degrees along the upper part, and with increasing pitch toward the bottom with a maximum of 4 to i, the radius of incline being 4.5 feet, thus add- ing to the better bearing against water pressure tending to raise it. The weight of the cylinder is 193,600 pounds. The operating apparatus includes two steel cables of 1.8 inches in WOODEN CRIB AND ROCK WEIRS 179 diameter, rolled on drums and operated by an electric motor. The speed of lifting the cylinder to a height of 13.1 feet or above highest flood water is 1 5 minutes. By auxiliary gearing through cranks the apparatus may be worked by hand. 172. Construction of Crib Weirs. A crib weir should never be left hollow, as was the upper part of the old Holyoke weir (Fig. 37), but should be completely filled in with gravel or rock. Many engineers advise against rock filling, as this permits the passage of air to the wood, and thus promotes its decay. The action of air in causing decay is still more marked if the weir is left hollow. Gravel well puddled around the woodwork becomes air-tight, and protects every timber which it encases. This ma- terial is therefore the most desirable filling. A timber weir is quite permanent when it is constantly submerged, as then only the apron will need repair. The shape of such a weir should always be such as to prevent the water which falls over it from excavating beneath its toe, especially if the foundation is of gravel or soft rock. In such cases a roller apron should be built, backed still lower down by a horizontal apron which will take up the scouring force of the water. Even on a firm rock foundation a clear overfall should not be given unless a deep water-cushion can be furnished or the bed of the river can be laid dry for examina- tion and repair of the weir. Timber dams are usually founded on rock or gravel, though any material will do. When founded on soft material loose rock may be dumped in, or piles must be driven and sheet piling be used to prevent underflow. 173. Wooden Crib and Rock Weirs. This type of weir is generally built where the bed and banks of the river arc of heavy gravel and bowlders or of solid rock. Crib weirs consist essentially of a framework of heavy logs, drift-bolted or wired together, and filled with broken stone and rocks to weight and keep them in place. Such works may be founded by sinking a number of cribs one on top of the other to a considerable depth in the gravel bed of the stream, or they may be anchored by bolting them to solid rock. They may consist of separate cribs built side by side across the stream and fastened firmly together as in the old weir at the head of the Arizona canal (Fig. 35), or i8o HEADWORKS AND DIVERSION WIERS they may be made as one continuous weir, as the structures at the heads of the Kraft Irrigation District canal in California, and the Bear River canal in Utah (Fig. 36). After its completion the weir is planked over on its exposed faces and forms one con- tinuous wall across the channel of the stream. The old weir at the head of the Arizona canal (Plate VI) consisted of crib boxes of hewn logs about 9 by 9 feet, the logs being fastened with drift-bolts, and the whole wired together and filled with rocks. This weir was constructed by laying mud- sills in a trench excavated in the bed of the stream, and on these was built up the cribwork. In the central and deepest portion of the river channel the weir was sunk to a depth of 33 feet in the gravel bed of the stream, while its crest was everywhere 10 feet f FIG. 35. Cross-section of Old Arizona Weir. above mean low-water. The base of this weir in the deepest part of the channel was from 36 to 48 feet in width parallel to the course of the stream, and the mudsills, which were 8 by 12 by 48 feet, were wired together with i-inch cable to act as a hinge be- tween the sections. The weir was built in four sections trans- versely to its axis (Fig. 35). The whole of the upper surface was planked over and formed a series of steps upon which the water fell, its force being thus broken. This weir failed in a great flood in 1905 and has been replaced by the Granite Reef weir (Art. 188). The crib weir at the head of the Bear River canal in Utah is 370 feet in length on its crest, which is 17 J feet in maximum height above the river bed, while the greatest width at its base parallel to the course of the stream is 38 feet (Fig. 36). The up-stream face has a slope of i on 2 while that of the down-stream face is 182 HEADWORKS AND DIVERSION WEIRS i on J, the water falling on a wooden apron anchored by bolts to the bed-rock of the river. This weir consists of heavy 10 by 12 timbers, drift-bolted to the rock and firmly spiked together. The interstices between these timbers are filled with broken stone, and it is backed by silt deposited from the river. The old crib weir across the Connecticut River at Holyoke, Mass., was about 1017 ft. in length, its ends abutting against heavy masonry wings at their extremities. Between these the crib weir was composed of 12 by 12 timbers, built in such a way as to present on the upper face a surface of planking inclined at an angle of 21 degrees to the horizon. These timbers were sepa- A 4 . FIG. 36. Cross-section of Bear River Weir. rated by transverse timbers at distances of 6 feet apart, and the whole was drift-bolted to the solid rock of the channel. The crib- work was filled with loose stone to a height of about 10 feet, and the upper surface of the weir was planked over. On the upper toe of the weir rested a bed of concrete to prevent seepage, and over this was a filling of gravel to a height of about 10 feet (Fig. 37). The down-stream face of this structure consisted of an apron or roller-way of similar crib timbers, a little more substan- tially built. The dam built by the Reclamation Service across the Yellow- stone River, Montana, for diversion of the Lower Yellowstone canal is 740 feet long, 9 feet in height, of ogee cross-section, and is built of wood founded on piles driven into the clay of the river SCOURING EFFECT OF FALLING WATER 183 bed (Fig. 38). The upper toe and the end of the plank floor which extends 18 feet below the lower toe are protected by 6" by 12" sheet piling driven 15 to 20 feet into the clay bed. The body of the dam and below the down-stream end of the floor are filled with heavy rocks. All planking and framing is heavily drift-bolted together and to the piles by i" square bolts 22 inches long. The planking of the surface is of 8 by 12 to 10 by 12 inch material. 174. Scouring Effect of Falling Water. In the construc- tion of weirs various subterfuges have been employed to deliver the falling water so quietly that it shall not erode the stream-bed below. The erosive force of falling water is such that it is capa- 4 8 IS W JO 14 FIG. 37. Cross-section of Old Holyoke Weir, Mass. ble of wearing away even the hardest rock. The principal forms which have resulted from the endeavor to reduce this action are: i, aprons; 2, sloping rollerways; 3, ogee curves to the lower tide of the weir; 4, water-cushions. Each of these forms has its advocates, and each is especially adapted to certain conditions, dependent chiefly upon the height of overfall and the character of the material of which the stream-bed is composed. Under similar conditions aprons are employed in all countries. Ogee shapes appear to have originated in India, and are very popular there. They have recently been adopted extensively in this country. 175. Weir Aprons. Where the foundation of the weir is of unstable material, as earth, sand, or gravel, an apron is built HEADWORKS AND DIVERSION WEIRS below its down-stream toe. Aprons are made of wood, of dry- laid masonry, of cement ma- sonry, of concrete, of reinforced concrete or of steel. They form a substantial artificial flooring to the stream-bed on which the force of the falling water is taken up, thus protecting it from ero- sion and preventing undercut- ting of the weir. Where an apron is employed, the weir de- pends on its efficient construc- tion and careful maintenance for its security. Such works are built of masonry in the most substantial manner in India, where a rough general rule is to give the masonry apron a thick- ness equal to one-half and a length parallel to the stream channel equal to from three to four times the vertical height of the obstructive part of the weir. Beyond this a loose stone apron is generally added, with a length equal to one and one-half times, and a depth equal to two-thirds of the height of the weir. An- other rule adopted in India is to give the apron a length equal to from six to eight times the square root of the maximum depth of water above the weir crest, and a thickness equal to one-fifth to one-fourth of the overfall height of the weir plus the depth of water on the crest. ROLLERWAY AND OGEE-SHAPED WEIRS 185 According to the American standards both of these rules seem to give unnecessarily substantial results. With us wooden aprons are generally employed which rarely exceed from 2 to 6 feet in thickness for the greatest height of overfall. Aprons, however, cannot be used with security with weirs in which the drop is considerable. No limit, other than that of expense, can be set to the height for which aprons are serviceable, for a point is ultimately reached where an ogee-shaped or rollerway weir or a water-cushion will be less expensive and more serviceable. 176. Rollerway and Ogee-shaped Weirs. Ogee-shaped weirs probably originated as a development of roller aprons. The first ogee weirs of any magnitude were those built on the falls in the eastern Jumna canal in India. The original sloping apron or rollerway is still largely employed, the chief objection to it being FIG. 39. Diagram of Ogee Curve. the amount of material required in its construction and its conse- quent cost. Such structures are the weirs of the Soane and Agra canals, illustrated in Plate V. In these the lower slope of the weir is made extremely flat, so that the friction of the water rolling over it shall retard its velocity and diminish its erosive action. In our own country a similar long sloping rollerway is that on the old Holyoke weir (Fig. 37). The ogee shape is an improvement on the rollerway. It reduces to a minimum the amount of material required, while producing nearly the same effect. The object of the ogee shape is to cause the water to slide instead of to fall over the weir, and the exact moment when water ceases to slide and commences to fall is shown by its losing its bluish color and commencing to become whitish. The ogee curve is best understood from the i86 HEADWORKS AND DIVERSION WEIRS accompanying diagram (Fig. 39). Bisect AE, and from the point of bisection at a draw a perpendicular cutting, the perpendicular let fall from A at C. Join C E and prolong this line until it cuts the perpendicular projected on B at D. From the points C and D as centres, draw curves of the ogee. 2 AB > Excellent examples of rollerway weirs with ogee-shaped curves are illustrated in Fig. 40 and in Plates VII and VIII, and ex- amples of storage dams with wide crests and curved overfalls in Chapter XVII. On the Ganges canal it was found that the ogee form of weir was not entirely satisfactory. The shock of the falling water proved so great as to materially injure the structure, and all of these ogee falls have since been remodelled in such a manner as 1, Austin, Tex., Z, Herschel, 3, Waters, 4, Francis & Kendall, S^Leffel, 6, Newton, 30 ' 7, Mechanicsvflle, N.T., 16 4 8, Croton, 38 ' 60 ft. high. 80 SO " 30 " FIG. 40. Cross-sections of Eight Ogee -shaped Weirs. to form water-cushions. Thus on falls 15 feet high the ogee has been cut so as to give first a vertical fall of 5 feet to a short level bench 10 feet in length, then a vertical drop of 10 feet ending in a shallow water-cushion the floor of which is of masonry 4 feet in thickness. 177. Water-cushions. The principle involved in the water- cushion is that which nature has laid down for herself on all WATER-CUSHIONS 187 natural falls, namely, that of having a deep enough cistern below the fall to take up the shock of the falling water and reduce its velocity to the normal. Cataracts and falls erode a cistern the depth of which bears a certain relation to the height of the fall. The method of constructing a water-cushion is not to excavate such a cistern below the weir, but to create a corresponding depth by building a low subsidiary weir below the upper weir. This subsidiary weir backs the water up against the lower toe of the main weir to the required depth, at the same time practically reducing the height of the fall by the height of the subsidiary weir. It is difficult to find any set rule for determining the depth of water-cushion for a given height of fall. From observations of several natural waterfalls it has been discovered that the height of fall is to the depth of the water-cushion as from 5 or 7 to i. In an experimental fall constructed on the Ban Doab canal in India it was found that, with a height of fall to a depth of water-cushion as 3 to 4, the water had no injurious effect on the bottom of the well. On canals where the height of fall is not great it has been discovered that the depth of the water-cushion may be approxi- mately determined from the formula D= c\/ ' h*\/ ' d, in which D represents the depth of the water-cushion below the crest of the retaining wall ; c is a coefficient, the value of which is dependent on the material which is used for the floor of the cushion and varies between .75 for compact stone and 1.25 for moderately hard brick; h is the height of the fall, and d is the maximum depth of water which passes over the crest of the weir. The breadth of the floor or the bottom of the cistern of the water- cushion parallel to the stream channel is dependent on the sec- tion of the weir and will not exceed Sd and should not be less than 6d. A rule laid down for determining the dimensions of water- cushions and their cisterns on the smaller canals in India is that the depth of the cistern at the foot of the weir shall equal one- third of the height of the fall plus the depth of water. Thus on a fall 4 feet deep on a canal carrying 5 feet of water the cistern depth will equal J (4 + 5) =3 feet. The minimum cistern length is equal to three times the depth from the drop-wall to the reverse slope x>f the cistern, which latter will be i in 5. The vr;.;-' % 1 88 HEAD WORKS AND DIVERSION WEIRS width of the cistern must be twice the mean depth of the water in the channel. The Reclamation Service has adopted the water-cushion, combined in some cases with the notched crest and gratings, for drops on a number of canals, including the Interstate canal, Neb.- Wyo., and Uncompahgre canal, Col. (Art. 223 and 224). In this country a few weirs have been designed and constructed with a partial ogee curve to the lower face, the water dropping into a water-cushion. The most notable of these are the great weirs at the head of theTurlock and Modesta canals in California (Article 356) and the Spier's Falls dam (Art. 359). A water- cushion 15 feet in depth is obtained below this weir by the con- struction of a subsidiary weir 20 feet in height, placed at a distance of 200 feet below the main weir. The height of overfall from the main weir is 98 feet, thus giving a ratio of depth of water-cushion to height of overfall of about i in 6. In the case of this weir, however, its down-stream face is not made vertical, but is made somewhat after the design which would be obtained by using one of the gravity formulas and adding to this sufficient material to produce the ogee curve. The Indian method, which has proved very satisfactory in practice, is well illustrated in the Vir weir (Article 184) and the Betwa dam (Article 355). In each of these the water is permit- ted a clear vertical overfall to the water-cushion, the weight neces- sary to give the weir stability being obtained by increasing its cross-section on the up-stream side. In both of these cases sub- sidiary weirs are constructed at some distance below the main weir in the rock bed of the river, which backs up the water to the required height on the toe of the main weir. A subsidiary weir of a form somewhat similar to that below the Vir weir is illus- trated in Fig. 171. This weir is employed below the main escape weir of the Periar dam in India to form a water-cushion on which the floods fall. 178. Masonry Weirs. For permanent weirs on stable foun- dations only masonry and steel should be used. It is frequently necessary, however, to build weirs of less durable material, the object being to economize on the first cost, or because the founda- OP TMI UNIVERSITY Of y MASONRY WEIRS l8o FORjJJ^X tion will not safely support a masonry structure. Masonry weirs may be built: i, of reinforced concrete; 2, of plain concrete; 3, of uncoursed rubble in cement; 4, of ashlar; 5, of brick; and 6, of various combinations of these, including loose packed, un- cemented rubble retained in place by masonry walls. Masonry weirs may be classified according to the superstruc- ture as follows: first, simple weirs with a clear overfall to the stream-bed; second, simple weirs with clear overfalls to an artificial apron; third, weirs with rollerway on lower face; fourth, weirs with heavy cross-section and ogee shape; fifth, weirs with clear fall to water-cushion. The principal classification of masonry weirs is dependent on the foundation. Where practicable such structures should only be founded on firm rock, but occasionally the depth of this below the surface is so great as to render it necessary to found the weir on gravel or sand. Classified according to their substructure, masonry weirs may be of the following types: i, founded on piles; 2, founded on piles and rock cribs; 3, founded on masonry wells or caissons; and 4, founded on rock. Masonry weirs are usually given a batter on the up-stream face of i to 2 inches per foot. The lower face may, according to the height of the structure, i, be given a slight batter; 2, have a parabolic or ogee curve to diminish erosive action; or 3, be given a batter of i on 3 to 5 and be built in steps to break up the force of the falling water. The curved face reduces the shock on the dam, but permits of erosive action on the foundation below the toe. The stepped face is well suited to floods of small volume, but is less effective with floods of greater amount. The top width of a masonry weir should not be less than 5 feet, and for high weirs more to enable them to resist blows from logs, ice, etc. Capstones should be dowelled and should have a downward inclination up-stream to ease the blows received from ice and floating matter. (Figs. 41, 43, and 53.) If of concrete this should be well reinforced in the upper third for the same reason. Where low masonry weirs are on porous foundations, as earth, loose rock, etc., earth backing is sometimes laid on the up-stream i go HEADWORKS AND DIVERSION WEIRS face to the crest height (Fig. 42). This should have slopes of i on 2 to 3, as with an earth embankment. If of less porous ma- terial than the foundation and compactly laid, such a back- ing may add materially to the safety of the weir by reducing the percolation under it. 179. Masonry Weirs founded on Piles. In the con- struction of masonry weirs in gravel or earth, it is usual to found the weir on piles driven deep into the river - bed. These may be of wood, of steel or of concrete. In a few instances cribs and caissons have been sunk for founda- tions. In India the usual foundation in unstable ma- terial is the "well" (Article 182). The Leasburg diversion weir on the Rio Grande, N. M., project of the Reclama- tion Service is of reinforced concrete. It is 600 feet long and 30 feet wide, founded on piles and sheet piling driven to a depth of 25 feet in the sand of the river-bed. At one end it abuts against solid rock, and at the other against a concrete pier, whence 1600 feet of earth embankment extend across the river bottom. (Fig.4i.) The MASONRY WEIR FOUNDED ON PILES AND CRIBS IQI weir proper is actually but 9 feet high and 2 feet wide on the crest, sloping on the down-stream side with a reversed curve to a broad reinforced concrete apron 2 feet thick, founded on piles, and 23 feet broad. The weir of the Norwich Water Power Company across the Shetucket River in Connecticut is a good example of a weir founded on piles. The bed of the river at the site of the weir is composed of gravel containing small bowlders and is 30 feet or more in depth. This weir (Fig. 42) is 15 feet wide at the base and 7 J feet wide on top, its maximum height being about 20 feet. It is constructed of rubble masonry with a cut-stone coping-wall. FIG. 42. Cross-section of Norwich Water Power Company's Weir. The upper slope is covered with one foot of concrete faced with planking secured to it with long iron bolts. The up-stream face has a batter of 1 2 on 5 and is backed by an earth filling having a slope of about i on i J, which reaches to the crest of the weir. A heavy timber apron projects down-stream for 22 feet, the last 8 feet of which has an upward pitch. 1 80. Masonry Weir founded on Piles and Cribs. On the Chicopee River in Connecticut is a weir built partly on rock and partly on deep gravel. Its cross-section is the same throughout and is similar to that of the weir just described. Where the river- bed is composed of gravel the weir rests directly on a depth of 3 feet of cribwork filled with broken stone. Below this and con- nected with its timber foundation is an apron 10 feet in length 192 HEADWORKS AND DIVERSION WEIRS which rests on anchor piles, its lower extremity being protected by a row of sheet piling. 181. Masonry Weir founded on Cribs. One of the most interesting and largest masonry weirs founded on unstable soil was the old Croton dam, in New York. This was constructed for water-storage but acted also as an overfall weir. The con- struction of this weir was peculiarly composite, a large portion resting on firm rock, the remainder being founded on a stratum of alluvial soil containing bowlders. The piers (Plate VI) were of timber crib-work, the walls of which were connected by ties and the whole filled with stone. This structure was 50 feet in maximum height and 76 feet in maximum width at the base. Its up-stream slope was vertical for 23^ feet, broken below into two vertical benches. It was backed behind by an earth embankment having a very low and flat slope. The down-stream face had an ogee curve. The crest was convex, with a radius of 10 feet, below which was a reverse or concave curve with a radius of 55 feet. Below the lower end of this weir was a raised apron 55 feet in total length and connected with the main weir. The rise of this apron was i in nj, and the amount of this rise was 2 J feet, giving a water-cushion of this depth in the lower part of the apron. At a distance of 300 feet from the extremity of this apron was a secondary weir of crib timber filled with broken stone. The object of this secondary weir was to divide the head of water, thus causing it to fall in two steps, the first 38 feet in height to the lowest part of the apron, and the second 15 feet in height over the secondary weir to the stream-bed. This secondary weir answered the additional purposes of creating a shallow water-cushion at the foot of the main weir. 182. Masonry Weirs founded on Wells. This class of weir is as yet peculiar to India, where it is built on sand or gravel stream- beds. In PL V are illustrated several examples of these structures ; those across the Soane River, India, and at Yuma, California, are described in Articles 168 and 169. They consist essentially of one or more walls of masonry running across the entire width of the stream and founded on wells, while the space between these is filled in with loose-packed stone. The slopes of these weirs MASONRY WEIRS FOUNDED ON WELLS 193 C 194 HEADWORKS AND DIVERSION WEIRS are generally long and low, varying between vertical and i on 3 to 5 on the upper face, but on the lower face ranging from i to 10 to 20. In the case of the weir across the Ganges River at the head of the Lower Ganges canal, the main obstruction to the stream channel is a masonry wall founded on wells. On the lower or down-stream face, however, instead of the usual long slope there is a vertical drop of gj feet. The top width of the wall is 7 feet, and the water falling over this drops to an apron nearly 150 feet long, which is composed of masonry resting on four rows of shallow wells for a distance of about 40 feet, below which a loose stone apron kept in place by rows of wells extends for the remaining 1 10 f eet. 183. Concrete Weir, Ashlar Facing. The Hen ares weir in Spain shown in cross-section (Fig. 43) is 23 feet in maximum FIG. 43. Cross-section of Henares Weir, Spain. height, its upper slope having a batter for the lower two-thirds of about 6 on i, and for the upper third of 12 on i. Its top width is 3.14 feet, its thickness at the base is 45.8 feet, and its face has an easy flat ogee-shaped curve. This weir is 390 feet in length on the crest, being curved in plan and running obliquely across the river at a tangent to the axis of the canal. Its body is composed of concrete, while the crest and lower slope are faced with cut stone blocks alternating in headers and stretchers. Leakage was obviated by cutting a channel in the rock along the central axis of the weir for its entire length, and in this is fitted a line of stone, half bedded in the rock and half in the concrete of the weir, the joints being run with pure cement. In the sides of each of the four upper courses of stones near the crest of the weir. RUBBLE MASONRY WEIR 195 were cut V-shaped grooves, and expanding horizontal grooves were cut in the upper and lower faces of each stone, forming a continuous channel which was filled with pure cement so as to form a tight joint between each stone. As the bed of the river was uneven, the lower portion of the weir was carried down as an apron by means of a series of blocks of stone formed in steps, the last of which is firmly embedded 3 feet in the rock. 184. Rubble Masonry Weir. The Yir weir at the head of the Nira canal, India, is built of uncoursed rubble masonry and is protected by a water-cushion. It is 2340 feet in length, 43^- feet FIG. 44. Cross-section of Iron Weir, Cohoes, X. Y. in height, and 9 feet wide on top, and is constructed of un- coursed rubble masonry. The down-stream slope is 8 on i for 20 feet from the crest and 6 on i for the remainder of the weir, while the up-stream face has a uniform batter of 20 on i and at no place is the mean thickness of the weir less than half its height. This weir is founded on solid rock, and in order to form a water- cushion a subsidiary weir is provided 2800 feet below the main weir. This subsidiary weir is located in a narrow portion of the river channel, its total length being 615 feet, its height 24 J feet, while its crest is 20 feet lower than that of the main weir, thus 196 HEADWORKS AND DIVERSION WEIRS forming a permanent water-cushion 20 feet deep. The maxi- mum flood which is estimated to pass over this weir is 158,000 second-feet, producing a depth of 32 feet in the water-cushion and a height of overfall of but 8 feet. 185. Iron Ogee Rollerway Weir. The State dam across the Mohawk River at Cohoes, N. Y., was remodelled to give the down-stream face an ogee shape. Iron and steel were used to give the required surface instead of cut masonry. As a result a substantial face and apron have been obtained at less expense than would have been possible with ashlar masonry. Otherwise the weir is practically a masonry structure, as this iron facing has been placed over and bolted to the old masonry weir, and the latter has been filled up with concrete to the surface of the iron facing. The total length of this weir is 1611 feet (Plate VIII). The facing is backed by strong plate-girder ribs shaped to the final contour of the weir (Fig. 44), and secured by bolts and braces to the masonry work of the old structure. Sheet iron is secured in grooves in these ribs so as to fill it up as a flush and smooth face, and concrete has been rammed in, forming a solid backing. In constructing this weir the lower half of the apron was first built and the space between the iron plates and the masonry filled with the concrete, then the upper half was built in the same manner and the concrete carried up behind the iron plates at the top. At the foot of the curved rollerway is a short apron of heavy plate iron about 5 feet in length, fastened to the lower girder of the rollerway on one side and to wooden beams let into the rock of the river bed at the outer end. The framing of this iron weir face is 12^ feet in length hori- zontally from the crest of the weir to the lower end of the roller- way, while the top of the coping is 8 feet 4 inches in length and slopes back with a fall of i J feet. The total height of the weir, from the crest to the foot of the rollerway, is 10 feet 6 inches. The coping girder is 8^ inches deep at the back or up-stream end, and 1 8 inches in depth at the crest-curve, which latter has a radius of 2 feet from the upper end of the crest-curve or coping. 1 86. Masonry and Iron Drop-gate Weir. At the head of the MASONRY AND IRON DROP-GATE WEIR 197 feW li '''' v si ]&&'/> ' V 0/ f A v* ^ , 1 / ' i ? iP^x/--' -f./!/' ' j ,} ^ i< N V v I / "y / x ^^fewiibv-l r isS^y fiDAvji^. 1 ' HEADWORKS AND DIVERSION WEIRS Goulburn irrigation system in Australia is a clear overfall weir for combined storage and diversion, and at each of its abutments there heads a main line of canal. Its available storage capacity is about 1000 acre-feet, though it is expected that this can be filled several times in a season. On the crest of the masonry struc- ture are built up iron pil- lars between which slide lifting-gates which can be raised and lowered by hy- draulic power, and add thus to the diversion height of the weir and furnish storage capacity equiva- lent to this height. The highest flood known in the river was estimated to discharge 50,000 second, feet, and the wasteway capacity furnished between the crest of the masonry work and the soffit of the overhead bridge is capable of passing a larger volume. The Goulburn weir is founded on alternate beds of sandstone, slate, and pipe-clay, standing almost vertically on edge. This weir is of sufficient height to raise the summer level of the river about 45 feet, FIG. 45. Down-stream Elevation, Goulburn , i f f Weir, Australia. Or tO a total of 5 f eet above the river bed. It is 695 feet in length, exclusive of the canal regulators at either end, which have a further length of masonry work of 230 feet. The body of the work is of combined concrete masonry, composed of broken stone, sharp grit, and Portland cement, backed with MASONRY AND IRON DROP-GATE WEIR 199 stepped granite. In the portion of the weir across the natural waterway of the river were six temporary tunnels (Fig. 45), each with a sectional area of 44 feet, designed to carry the stream flow ~I33~r3 FIG. 46. Section of Goulburn Weir, Australia. of about 3750 second-feet during construction. These were filled in with masonry after the completion of the remainder of the work. The waterway in the upper portion of the weir above 200 HEADWORKS AND DIVERSION WEIRS the masonry crest is composed of 21 floodgates (Plate IX) each having a clear opening of 20 feet horizontally and 10 feet verti- cally. These are lowered into chambers or recesses in the body of the structure (Fig. 46), and can be so adjusted as to maintain the water-level in front of the canal offtakes at the normal full- supply level. The chambers are lined with skeletons of cast-iron ribs between strong cement mortar; and the wall in front of each chamber that takes the pressure of the water is strengthened by a series of rings of wrought iron built into the concrete. The gates are framed with wrought- iron T beams filled with cast-iron plates, and weigh 7 tons each. They are worked by screw-gear- ing actuated by 3oJ-inch Leffel turbines, which can be worked either together or separately. The available head for working FIG. 47. Cross-section of Reinforced Concrete Weir, Theresa, N. Y. them varies from 3 to 13 feet, according to the volume of water in the river, and they give from 3 to 27 horse-power. Hand- gearing is provided for each gate in case of emergency. 187. Reinforced Concrete Weir. Recently diversion weirs of moderate height have been constructed of reinforced concrete. A good example of such structures is one at Theresa, New York, which has a total length of 120 feet and a height of n feet. It consists of a series of triangular walls or buttresses of solid concrete, each 12 inches thick and spaced 6 feet apart, dowelled to the rock on which they rest with ij-inch iron pins 36 inches long. They support an inclined deck consisting of 6 inches of concrete reinforced with Thatcher steel bars, f to f inch in di- ameter, spaced 6.3 to 7 inches, center to center, and expanded metal (Fig. 47). The crest is strengthened with a 6 X 8-inch REINFORCED CONCRETE WEIR 201 concrete beam reinforced with two J-inch steel rods. The base of the spillway or toe is also reinforced with a triangular block of concrete 40 inches wide. The buttresses were built on forms and the whole work completed in 18 working days. An excellent type of such weir is that built by the Reclamation Service for the diversion of the Shoshone River into the Corbett tunnel. This weir crosses the river at right angles with a crest length of 400 feet and height of 24 feet (Fig. 48). In section it is a truncated triangle with an up-stream surface of reinforced concrete 2\ feet thick, resting on a 3^-foot concrete cutoff wall, '0- 3*Z5tS*^^\**^^^ f : A ^** f rta U& b^e^^^^V'M'c^oX^U^^^fe^fe 1 f ^\^^^^^^l : ^^^^^^ E1.4607.0 C i-^U_ ^^p- U to extend SECTION A-A 3 into bLul. FIG. 48. Cross-section of Corbett Weir, Shoshone Project, Wyoming. and having a slope of i to i. The lower side is open and drops off to a 2-foot reinforced concrete floor which extends 25 feet down-stream to a cutoff concrete wall 3j-feet thick. Under the point where the falling water strikes the floor is a third foundation wall 3J feet wide at base and, like the others, about 6 feet in depth. The upper slope is supported at intervals of 12 feet by reinforced concrete partition walls 2 feet in thickness. The rein- forcing bars are of f- to J-inch square steel spaced 6 inch centers. At one end of the dam is a sluiceway of 21 feet clear opening divided by two piers, and separated from the weir by a long 202 HEADWORKS AND DIVERSION WEIRS concrete training wall 3^ feet thick. Adjacent to the sluiceway is the head of Corbett tunnel, entrance to which is controlled by two 6 feet 6 inches regulating gates (Fig. 49). 1 88. Reinforced Rubble Masonry Weir. The failure of the Arizona dam (Art. 173) in the floods of 1905 resulted in the acquirement of the Arizona and related canal systems by the United States Reclamation Service, which proceeded at once to 10 10 20 FIG. 49. Plan of Corbett Dam and Headworks, Shoshone Project, Wyoming. erect a permanent masonry diversion weir. At this structure head the main north and south side canals, which carry all the water for the Salt River project, including the natural flow of the river and the water stored in Roosevelt reservoir (Art. 360). The Granite Reefs diversion weir (Fig. 50) is located 2 miles REINFORCED RUBBLE MASONRY WEIR 203 below the old Arizona dam. (PL VI.) It raises the water of the combined Salt and Verde rivers 15 feet, or 5 feet higher than did the old dam. It is nearly 1300 feet long and, in- cluding sluice and regulating gates, contains 40,000 cubic FIG. 50. Plan of Granite Reefs Weir and Headworks, Arizona Canal. yards of concrete. In plan it is straight and crosses the river at right angles to its course. The regulating gates and main distributing canal on the north side have a capacity of 2000 second-feet, and those on the south side a capacity of 1000 second-feet. The main body of the weir is of heavy bowlders embedded in concrete. Its design is unique, the structure being divided horizontally into two portions, viz., a massive ogee-shaped weir 7 feet 6 inches wide at top, 31 feet 6 inches wide at bottom, and 204 HEADWORKS AND DIVERSION WEIRS Note: All reinforcing and of steel I 18'concrete s'o'k apart. 3^7 from 26 to 30 feet in height, embedded for a depth of n to 15 feet in the gravel of the river bottom. This section is reinforced near the crest, down-stream face and bottom with f- to f -inch steel rods laid horizontally 12 inches center to center, and longitudi- nally of the structure. This massive weir rests, as a foundation, on walls of reinforced con- crete 3 feet 6 inches wide laid crosswise of the weir axis and 21 between cen- ters. These walls are rein- forced with i -inch steel rods set vertically and spaced 2 to 3 feet between centers. These cross walls are sunk 9 to 19 feet to bed-rock and form wells with two longitu- dinal walls 1 8 inches thick, under the up- and down- stream faces of the weir. The cross walls extend be- low the down-stream face as a buttress with i on 2 slope. (Fig- 51.) Where the bed-rock was of such a depth as to make it impracticable to extend the foundations to it, three curtain walls were built ex- tending across the stream in this section. The one under the upper toe of the dam is 6 ft. in width and is carried down to a depth of about 18 ft. below the elevation of the apron below the dam. The curtain wall under the lower toe of the dam is carried to a depth cf 14 ft. below the surface of the apron. Through this wall were left openings 6 ins. square, placed 5 ft, apart and about 6 ft. above the bottom of the wall. These openings permit the water that rmy collect under the dam to drain out under the apron. The apron of concrete is 18 in. thick FIG. 51. Cross-section of Granite Reefs Weir, Salt River, Arizona. 206 HEADWORKS AND DIVERSION WEIRS on a foundation of placed bowlders, having a thickness of 4^ ft. It is laid in squares of about 10 ft. on a side, between which a space of about 3 ins. is left. This space permits the escape of water from under the apron, which is prevented from finding an outlet down the stream by the curtain wall 12 ft. deep that is built under the down-stream edge of the apron. (Fig. 52.) 189. Other Masonry Weirs. A masonry diversion weir, which also serves for purposes of storage, is that across the Pequannock River near Newark, New Jersey. This weir (Fig. 53) is built of rubble masonry, coursed and dressed on its faces FIG. 52. Granite Reef Weir and Apron, on Bowlder Foundation. and having an ashlar capstone. That portion of the structure which acts as a dam is 38 feet in maximum height, 5 feet 10 inches wide on top, and 21 feet wide at the base. The remainder of the structure, which is built as an overfall weir, is set nearly at right angles to the main dam and is curved with a radius of 640 feet. This overfall weir is 22 feet in height, its crest being 7 feet below that of the main dam. It is 15 feet in width at the base and 5 feet wide on top, its lower slope on the up-stream face being vertical for 7 feet, above which it has an inclination of 3 on i. The down-stream face has an inclination of 8 on i for 8 feet below the crest, below which it changes to about 5 on i for 8 feet more, and then to 3 on i . The result is to give a clear overfall to the bed-rock below, which is protected by a trifling depth of water in the river channel, which acts as a shallow water-cushion. The coping-stone of the weir is made continuous by means of dowels between the several stones, and is secured to the structure by anchors let into the masonry which hold down the dowels every 12 feet. 208 HEADWORKS AND DIVERSION WEIRS The new masonry weir recently constructed to replace the old rock and crib weir at Holyoke, Mass. (Fig. 37), is 1020 feet in maximum length. At both ends are built wing walls of masonry extending to a height of 12 feet above the weir crest. The upper part of the down-stream face is designed on a parabolic curve, which is that of water falling freely when flowing 4 feet deep over the crest. At the point of reversing the parabolic curve is changed to a cycloidal curve (Fig. 54), which is that of quickest descent. At FIG. 53. Cross-sections of Newark Dam and Weir. the toe is an up-curve to reduce erosive action. The slope of the up-stream face is i on 5, which is stepped off every 5 feet. The materials of construction are rubble masonry with dressed stone cap and facing and concrete toe and footing. Each stone of the first eight courses is tied with galvanized dogs or dowels. 190. Diversion Dams. There are several structures of con- siderable magnitude which, from the functions they perform, should be classed as diversion weirs rather than storage dams. Prominent among these are the Betwa dam in India and the Fol- som, Austin, and La Grange dams in the United States (Arts. 355 to 35&)' The two latter were built solely for purposes of diversion, while the former serves to store as well as to divert RIVER-TRAINING WORKS 20Q water. These works, however, are ot such magnitude that the principles involved in their design and construction are essen- tially those employed in designing masonry dams for water stor- age, and for this reason they are described among masonry dams. 191. River- training Works. In connection with all irri- gation works heading in lowlands where the slopes of the stream- El. 100.2' 80' hH --(El. 7T FIG. 54. Cross-section of New Holvoke Weir, Mass. beds are slight and their banks of sand, silt, or other easily eroded material, river-training or improvement works must be con- structed in order to maintain the stream in the channel which will cause it to do the least injury to the diversion works. During periods of high flood such rivers erode their banks and may change their channels to such extent as to leave the head or diversion works dry and high or to undermine and destroy them, unless the river is so trained as to secure for it a permanent channel for some distance above and below the diversion works. Such training-works have been extensively constructed at the heads of many of the great Indian canals which head in lowlands or deltas. The works for the protection of the Narora weir of 210 HEADWORKS AND DIVERSION WEIRS the Lower Ganges canal, India, extends 4 miles above and 15 miles below the canal head. They consist of a long earth em- bankment or levee from which shorter embankments or groins project at right angles to the course of the stream. The groins are 10 feet wide on top with slopes of i on 2 and are i to 2 miles in length. The end 150 feet, or the nose, has a 5o-foot spur pointing up-stream at 50 feet from the end of the groin. The entire nose is paved with heavy dry -laid rubble to a depth of 2 to 3 feet. Similar groins are sometimes necessary in weirs built across broad, shallow river channels. These project at right angles to the weir and parallel to the river's course to train the latter straight across the weir. Otherwise the water might be deflected away from the headgates, or towards them so as to injure them. A good example of such works is on the Yuma project on the Colorado River (Art. 194). Here the river floods are restrained by earth dikes or levees similar to those so successfully em- ployed on the Mississippi River. These levees have slopes of i on 3 on the water side and i on 2^ on the land side. They are 8 feet wide on top and extend 5 feet above the highest flood mark. The most magnificent examples of river-training works are to be found on the Mississippi and its branches, where it has been found necessary to guide and maintain their channels with a view to the improvement of navigation. These works consist, accord- ing to circumstances, of walls or embankments parallel to the channels of the streams so as to give them a uniform waterway, or of jetties run out at right angles to the banks so as to direct their flow, and of combinations of embankments, jetties and groines. CHAPTER XI SLUICEWAYS, REGULATORS, AND ESCAPES 192. Sluiceways. Sluiceways, scouring- or undcrsluices, are placed in the bottom of nearly every well-constructed weir or dam, at the end immediately adjacent to the regulator head. Their object is to remove, by the erosive action of the water, any sedi- ment which may be deposited in front of the regulator. If the flow in the stream is sufficiently great, these sluices are kept con- stantly open and thus perform their functions by keeping the water in motion past the regulating head and thus preventing the silt from settling. If sufficient water cannot be spared to leave the sluices constantly open, they are opened during flood and high waters, and by creating a swift current are effectual in re- moving silt which has been deposited at other times. The scouring effect of sluices constructed in the body of the weir is produced by two classes of contrivances; namely, by open sluiceways and by undersluices. The open scouring sluice is practically identical with the open weir, as the latter consists of sluiceways carried across the entire width of the channel. Where the weir forms a solid barrier to the channel and is only open for a short portion of its length adjacent to the canal head, the latter is spoken of as a sluiceway. The waterway of a scouring sluice is open for the entire height of the weir from its crest to the bed of the stream. Undersluices are more generally constructed where the weir is of considerable height and the amount of silt carried in suspen- sion is relatively small. In these the opening does not extend as high as the crest of the weir, nor does the sill of the sluiceway necessarily reach to the level of the stream-bed. It is chiefly essential that its sill shall be as low as the sill of the regulator head. Undersluices are more commonly employed in the higher struc- 211 212 SLUICEWAYS, REGULATORS, AND ESCAPES tures, such as weirs and dams which close storage reservoirs (Articles 376 and 377). Sluiceways are practically open portions of the weir and con- sist of a foundation, floorway, and superstructure. The floor must be deep and well-constructed and carried for a short dis- tance up-stream from the weir axis and for a considerable distance below it. On it are built piers grooved for the re- ception of planks or gates, so that the sluiceway may be closed or opened at will. 193. Examples of Sluiceways. At the head of the Monte Vista canal, Colorado, are sluiceways of wood. The weir is built across the gravel bed of the Rio Grande, and is founded on piles sunk to a depth of 10 feet. The weir terminates at the end adjacent to the regulator head in five scouring sluices. These are founded on piles, and the stream-bed beneath is floored with planking to form an apron to protect it against erosion. The openings are separated by upright posts of wood reaching to the crest of the weir, and can be closed by flashboards dropped be- tween grooves. An excellent example of masonry scouring sluice is in the weir at the head of the Agra canal in India. In the end of the weir adjacent to the canal head are a set of 16 openings having a clear sluiceway of 138 feet. These openings are each 6 feet in width between the upright piers separating them and are 10 feet in height, surmounted by a masonry superstructure or bridge the height of which is 19 feet above the stream-bed. The object of this bridge is to give a platform from which to operate the sluice gates, which are of wood, well braced and fastened with iron, and slide vertically between masonry piers each 2\ feet in thickness. They are raised by means of a winch which is oper- ated from above, travels on a hand car on rails so that it can be placed at will above any gate. The floor, which is flush with the stream-bed and on a level with the sill of the regulator head, is 12 feet in width parallel to the stream channel and extends 8 feet up-stream and 41 feet down-stream from the line of the piers. When these gates are open all the heavy silt-laden waters are carried through the sluices, and when closed and then suddenly 2I 3 Figures without dimension lines are elevation*. Elevations refer to St Icrel 214 SLUICEWAYS, REGULATORS, AND ESCAPES opened the scour produced by the rush of water is effective in removing the silt from in front of the canal head. 194. Yuma Project and Sluiceways, Laguna Weir. The Reclamation Service has constructed a project near Yuma, Arizona, for the irrigation of land on both sides of the Colorado River which contemplates the permanent reclamation of nearly 97,000 acres by a combination of irrigation levee and drainage works. The deposition of silt of the Colorado River is one of the most difficult features and greatly influenced the type of head- works and the design of scouring sluices to remove silt at the canal head. The occasional overflow of the Colorado River made necessary the leveeing of the entire tract. Most of the silt is car- ried near the bottom of the river, the surface-water being rela- tively free from sediment. Water is, therefore, taken into the canals by a skimming process over a long row of flashboards, the canal thus being filled by drawing but i foot in depth of water from the surface of the river. (Art. 195.) The first 3,000 feet of the canal on each side of the river are constructed of such size that the movement of the water through it is slower than i foot per second, thus creating in that portion of the canals a settling basin. The grade of the river at the weir site is about i foot to the mile, so that a weir 10 feet high creates a settling-basin of rel- atively quiet water for approximately 10 miles in length above it. At each side of the weir and excavated to the depth of low water in the river is a sluiceway 200 feet wide. (Fig. 55.) The sluiceways are closed by large gates operated by hydraulic machinery. The area of these sluiceways is so great that the water movement toward the canal will be sufficiently slow to permit most of the sediment to be deposited before reaching the canal intake. When a sufficient accumulation has occurred the sluice-gates will be opened and the capacity of each sluiceway being approximately 20,000 second-feet, the rush of this volume of water is expected to carry out the sediment above the canal in- take. The ordinary low-water flow of the Colorado River is from 3500 to 4000 second-feet; the capacity of each sluiceway is, therefore, about five times this volume. At the lower end of the YUMA PROJECT AND SLUICEWAYS 215 settling-basins gates are arranged to discharge into the river so that the water can be drawn down to the level of the stream, and a grade of n feet in 3000 feet is thus obtained to give swift cur- rent for the scouring. At the lower end of the settling-basins the canal begins. The weir and headworks are of rock, concrete, or steel, with the exception of the sheet-piling, which is driven entirely below the water-level and is thus not subject to decay. The canals are designed so that water will flow at a higher velocity through them riprapped with loose rtone . V Top of Embankment Elev. 1325 PLAN FIG. 56. Plan of Headworks, Granite Reef Weir, Salt River, Arizona. than in the settling-basins, the effect being to prevent the deposi- tion of sediment in them. At either extremity of the Granite Reefs weir of the Salt River project, Arizona, of the United States Reclamation Service, and in front of the intake basins to the canal regulators, are sluice- ways designed to carry off much of the heavier silt-laden water of flood rises and thus prevent the deposition of silt at the canal entrances. They are also designed to scour out such sediment as may accumulate at these points. The north sluiceway con- 216 SLUICE GATES, LACUNA WEIR 2I 7 sists of four openings each 1 5 feet wide in the clear. A concrete wall extends 200 feet up-stream from the pier next the main weir with a view of directing the flow of water into the basin at the head-works. (Fig. 56.) Each opening is closed with metal gates 9 feet high between piers 5 feet 7 inches thick and 37 feet in length parallel to the stream. The entire structure is of concrete masonry (Fig. 60), abutting on either side against similar mas- onry in the weir and regulator. The piers rise to a height of 33 feet 9 inches or 15 feet 8 inches above the weir crest. A con- crete floor several feet in thickness extends for some distance above and below the sluiceway. 195. Sluice Gates, Laguna Weir. These gates are set in FIG. 58. Half Plan, Sluice Gate, Laguna Weir, Colorado River, California. concrete masonry piers 8 feet wide and 48 feet long, by 40 feet 9 inches in height above the gate scats. Each opening has a clear waterway width of 33 feet 4 inches. A distance of 8 ft. above the service gate seats is a set of gate seats for emergency purposes. But one emergency gate is provided for the three openings, this gate being transferred from one opening to another as necessity demands. There is a girder bridge with- out a floor over the tops of the piers and abutments above the position of the emergency gate seats. This bridge is provided with a track for a car on which the operating machinery for the emergency gate is located and which is used in transferring this gate from one set of gate seats to another (Fig. 57). A similar bridge, with a floor, is placed above the service gate seats for the operating machinery for the service gates. The bodies of the gates (Fig. 58) are constructed throughout of suitable plates and 2l8 SLUICEWAYS, REGULATORS, AND ESCAPES angles, with riveted connections, and are 17 ft. n ins. high and 34 ft. gi ins. wide. The thickness of the plates and the sizes of the angles throughout are proportioned to the stresses upon them. The water pressure is taken directly by a skin plate on the up- stream face of the gate and transferred laterally to the piers at the side of the gate by means of four horizontal riveted girders. Each girder has a maximum depth at the center of 42 ins., a minimum depth at the ends of 27 ins., 'and is composed of flange angles and a web plate, reinforced with angle stiffeners at intervals of about 2\ ft. The three lower girders are equally spaced at a distance of about 5 ft., while the distance between the two upper ones is about 7^ ft. The four girders are interbraced by means of five cross girders, likewise composed of angles and plates. To prevent lateral motion of the gates there are placed on the sides of each gate, at the four corners, cast-iron rollers having an ap- proximate length and diameter of 6 ins., which have rolling con- tact with the gate frames. On the backs of the gates, at the ends of the girders, are attached cast-steel strips, having finished sur- faces 6^ ins. wide for transferring the water pressure through the roller trains to the roller tracks on the gate frames. The lower edges of the skin plate and end web plates are finished to a true surface to form a water-tight seat on the gate sill. Attached to the front of each gate, by means of angles, adjacent to the piers and abutments are 3x3-111. needles of Oregon fir. These strips of wood are so placed as to form snug contact with an exterior flange of the gate frame castings, and thereby prevent seepage around the ends of the gates. The gate sills are composed of wrought-iron plates fastened with lag screws to I2xi2-in. white-oak timbers anchored to the rock floor of the sluiceways. Each roller train contains 26 cast- iron rollers, 6 ins. in diameter and 5 11-16 ins. in length, fitted between two |x6-in. wrought-iron plates, 19 ft. 10 ins. long. The rollers have bronze bushings and revolve about ij-in. steel pins that pass through both the bronze bushings and the wrought iron plates. The ends of the roller racks contain pulleys around which J-in. crane chains pass. One end of each of these chains passes over a sheave located on the operating bridge, thence to SLUICE GATE, GRANITE REEF WEIR 2IQ an attachment on a counterweight box. The other end of the chains is secured to small cast-iron drums, also located on the operating bridges. By means of this arrangement, it is possible to raise the roller trains to the full height of the position of the gates by hand operation of the cast-iron drums. Each counterweight box weighs 6500 Ibs., and, including the weights, a total of 48,500 Ibs. are counterpoised against the weight of the gate. The gates are electrically operated. 196. Sluice Gate, Granite Reef Weir. The method of opera- tion of these sluice gates is unique, the design being such as to 220 SLUICEWAYS, REGULATORS, AND ESCAPES give clear overhead passage to the great floods which may assail this structure. There are four clear openings in the north sluice- way (Art. 194), each 15 feet wide by 20 feet high and closed with lifting steel gates 9 feet high (Fig. 59). The separating piers are each 5 ft. 7 in. in thickness, of concrete, and founded on a mass of concrete 10 feet in thickness resting on solid rock. In this foundation mass is a tunnel in which run eight plow steel ropes of ij in. thickness which pass up shafts in the piers to chain wheels 31 in. in diameter. These chains are operated by an FIG. 60. Rear of Sluice Gate before being Concreted. Granite Reef Weir, Arizona Canal. hydraulic cylinder actuated by electric motor and pump placed on the abutment. The arrangement is such that all four gates can be raised or lowered at once from this station. The sluice-gate has at the up-stream face a cast-iron curved shell f-in. thick, made in halves and riveted together in the field. The gate is filled with concrete, giving it a total weight of about 30,000 Ibs. (Fig. 60.) Each sluice-gate is suspended by two chains of i J-in. metal, which are carried first over 31 -in. diameter pocketed chain wheels, then down through the pier or abutment FALLING SLUICE-GATES 221 into a tunnel, then under 21 -in. diameter chain wheels. The chains connect with the two ends of a i J-in. diameter steel rope that is laid around a lug on the periphery of a steel drum of 7 ft. radius. There is one lug for each sluice-gate. 197. Falling Sluice-gates. Various devices have been em- ployed whereby the gates closing sluiceways may be opened rapidly and under the greatest pressure of water which may be brought against them by sudden flood rises. In nearly all scour- ing sluices the gates are operated from a superstructure above the level of the highest flood. This form of construction is ex- pensive and interferes with the free flow of water by stopping and perhaps choking the sluices with floating brushwood and logs. To remedy this and obtain the largest percentage of free space between the piers for the passage of flood waters, some modern Indian works have been given much larger openings between piers, and the gates are so operated that no superstructure is necessary above the level of the weir crest. As a result the floods may pass with little obstruction over as well as through the weirs. Such structures as these are of necessity strongly constructed and are made capable of quick operation. Two excellent examples of this class of structure are furnished by the shutters in the Maha- nuddy weir at the head of the Orissa canals and those of the Dchree weir at the head of the Soane canals in India. 198. Bear-trap Movable Sluice-gates. One of the most satisfactory rapidly operated movable sluice-gates or shutters is the American type of bear-trap gate as developed on the Great Kanawha River, W. Va., by the Engineer Corps of the Army. This gate is almost automatic in operation. When raised it forms an obstruction or weir across the entire width of the channel, and when lowered it is either lifted above the water surface or dropped against the bed of the stream so as to offer no obstruction to its free flow. The Chanoine modification of the original bear- trap weir shutter is illustrated in Fig. 6 1, which is self-explanatory. The essential features of the old bear-trap gate are two leaves built across the sluiceway and fastened by horizontal hinges at the bottom. When the sluiceway is open the leaves lie in a hori- zontal position, the up-stream leaf overlapping the other for a 222 SLUICEWAYS, REGULATORS, AND ESCAPES portion of its length. When the sluiceway is closed the two leaves form a triangle, of which the bottom of the sluiceway is one side and the leaves the other two, the apices being at the two hinges and where the leaves abut against each other. The space within the triangle is a chamber which may be filled by inlet pipes closed by means of valves under the control of the operator of the gate. To raise the gate the outlet from the chamber below is closed and the inlet opened, when the water fills the chamber and presses the lower surface of the leaves. As the water has also access to the upper surface of the upper leaf, the pressure from below upon it is neutralized; on the lower leaf there is no counter pressure, FIG. 61. Chanoine Movable Shutter, Raised, Lowered, and Closed. and therefore the pressure from below tends to raise it, and also the upper leaf which rests upon it. This is done in a properly proportioned structure, and the gate is carried to a height limited by the dimensions of the leaves. To lower the gates the water from above is cut off, the outlet valves are opened, and the chamber emptied. The pressure of the water is thus thrown on the upper leaf, and forces it back into a horizontal position against the bed of the sluiceway. This form of gate has been found difficult of operation, owing chiefly to the difficulties of properly proportioning the angles and lengths of the leaves. Improvements have resulted in the ad- dition of a leaf, or, more correctly, in practically dividing the upper leaf into two parts or joints (Fig. 62), so that as the sluice-gate is lowered the upper leaf which is jointed near its center folds in- MAHANUDDY SLUICE SHUTTERS 223 ward, that is, into the chamber, while the upper and lower leaves are hinged together at the top. This is practically the Parker gate, in which have been eliminated nearly all the difficulties of the old bear-trap, as there is no overlapping at the apex, while the height obtainable for the same length of sluice is over twice as great; there is no sliding friction, and the gate cannot be brought to a sudden stop when it approaches its full height, but comes to a rest gently. The conditions which give the most satisfactory length of leaf for the Parker gate are, according to Lieut. H. M. Chittenden, U. S. A., lower leaf plus lower section of upper leaf minus upper section of upper leaf equals the base, and that when HIS 3E HIN HINGE: LET OUTLET ^ FIG. 62. Bear-trap Gat:, Parker Modification. raised to full height they shall not rise above a curve corresponding to the particular condition of back-water. The proportions as shown in Fig. 62, however, practically fill all conditions essential to successful operation. 199. Mahanuddy Sluice Shutters. These shutters are de- signed somewhat after the plan adopted on some of the older weirs across the river Seine in France. Each bay of the sluiceway is closed by a double row of timber shutters fastened by wrought - iron bolts and hinges to a heavy beam of timber embedded in the masonry floor of the sluice (Fig. 63). These shutters are arranged in pairs, the lower shutters being 9 feet in height above the floor, and the upper shutters 7^ feet in height. Each bay is separated from the next by a stone pier 5 feet thick, to which the gearing for 224 SLUICEWAYS, REGULATORS, AND ESCAPES working them is attached. During the floods the upper row of shutters, which fall forward up-stream, are held to the floor of the weir in an almost horizontal position by means of iron clutches. The rear or lower row of shutters which fall down-stream are kept in a horizontal position by the rush of water over them. In order that the down-stream row of shutters may be retained in position and act as dams when raised, they are provided with strong wrought-iron struts attached to their lower sides. In order to lift the lower set of shutters when the water is resting on top of them the up-stream set of shutters are first raised, this operation being aided by the upward pressure of water from beneath, and they are retained in a vertical position by means of chains guyed to the FIG. 63. Cross-section of Mahanuddy Automatic Shutters, India. piers above them. Relieved of the water pressure by this upper set of shutters it then becomes possible to raise the lower set by means of a hand windlass, after which the upper set are lowered again into their original position and the weir is ready to withstand the next flood, as the lower set can then be instantly dropped by merely removing the bolts which support them. 200. Soane Falling Sluice-gates. The shutters of the Maha- nuddy weir have never been successfully operated against a greater head than 6J feet, and the jar produced by opening the upper gates and by the fall of the lower gates has always been violent. To diminish this jarring action and to obtain a more easy and successful operation in the shutters of the Soane weir, a new design was devised, and it furnishes what is probably the best example of self-acting sluice-gate which has yet been con- structed. SOANE FALLING SLUICE-GATES 225 PLATE XI. Falling Sluice-gate. Soane Canal, India. 226 SLUICEWAYS, REGULATORS, AND ESCAPES The crest of the Soane weir is gj feet above the river-bed, and the grates by which the sluice-ways are closed are each 20 feet in length and gj feet high. They are separated by masonry piers 6^ feet thick by 32 feet in length. The floor of these sluices is very substantial and is 90 feet in length, parallel to the river chan- nel. As the velocity of the current through them may be as high as 17 \ feet per second, it was found necessary in order to with- stand its erosive action to found the flooring on wells or blocks upon which an ashlar pavement 15 inches in thickness has been built up. The gates are constructed of wood, well braced and set in pairs in each opening (PI. XI). A low masonry wall 12 inches high has been built up on the down-stream side of the floor- ing in each alternate bay, thus giving a water-cushion of that depth on which the lower gate falls, relieving the piers of a por- tion of the shock. The upper gate falls up-stream, being hinged to the floor at its bottom and held upright by a series of six struts. These are hollow iron cylinders with small vent-holes, and in them pistons work in such manner that when the gate is raised by the pressure of water beneath it the impact against the struts is relieved by the pistons plunging into the cylinders, from which the water is slowly forced through the vent-holes. The lower gates fall down-stream and are supported by four iron rods hinged to their upper faces below the center of pressure, and when in posi- tion are held upright by chains attached to the piers above. If both gates are open and it is desired to close the lower one so as to cause it to dam up the water, it is first relieved by pushing aside the catch which attaches the uppej gate to the floor when this is raised a little by means of a hand lever, after which the force of the water brings it up slowly for a short distance and then with a jar against its hydraulic struts or rams. The pres- sure is now relieved from the lower gates, which can be raised by hand levers and chained in an upright position to the piers. The upper gate is again lowered, now falling chiefly by its own weight through the water, and is fastened down by clutches. The lower gate, which now acts as the dam, is prepared to be released at a moment's notice. 201. Automatic Wasteway Gate. On the Belle Fourche RELATIONS OF WEIRS TO REGULATORS 227 canal, South Dakota, the Reclamation Service has designed some small automatic iron waste gates. The wasteway section is 5 feet wide and the ribbed iron gate closing it is 5 feet square. It is supported by an iron strut which half rolls on a cogged rack. This gate is balanced for a head of 4.95 feet, when it opens by swinging upward through an arc of 45 degrees. For a head of 4.5 feet it closes automatically. (Fig. 64.) 202. Relation of Weirs to Regulators. A diversion weir retards the flow of the stream and raises the level of the water to a sufficient height to enable it to enter the canal head. The reg- ulator is the controlling valve which admits this water to the canal Balancing Head 4.95 Gate Open Balancing Head J&teJGto^i In 'n* WaJj FIG. 64. Automatic Wasteway Gate, Belle Fourche Canal, South Dakota. if required, or prevents its entrance and causes it to pass on down the stream over or through the weir. The weir is the boiler which generates the power; the regulator is the throttle-valve which controls its entrance to the machinery. The regulator should be so located with relation to the weir that the water held up by the latter will pass at once and with the least loss of head through the former and into the canal. This is effected most successfully by placing the canal head immediately adjacent to the weir and building it in unison with and as part of the structure. The weir should not be so aligned as to cross the river diagonally at an angle inclined either to or from the regulator head. In the former case 228 SLUICEWAYS, REGULATORS, AND ESCAPES it tends to force the water against the regulator, creating an unnecessary scour at that point and producing an undue pressure or strain upon the head. It should not incline away from the regulator, as the reverse effect would be produced and it would cease to perform its function of directing the water into the canal. The best alignment for the weir with relation to the regulator is to have it cross the stream at right angles to the line of the latter. H 1 j 1 <' -{ : 1 i ' x i 1 i i V V 1 ! 1 >\^ I 1 ! : fed 1 1 1 i i i i i fex ! i ; i i i > i 2 i 1 '/ ' ^ / "'. - i 1 i i v I.-/! i i i j * 'i Sfii ; | ! \^ i i i i 1 ;' ; / i i 1 i i // i i i I I ' // i } j i ' i i [ j ; 111 \ I I ' \\ i I '. : i ' 1! ; i i I i j ; 1 J 1 1 Scale ofleet,. FIG. 65. Plan of Headworks, Ganges Canal, India. This gives a clear even scour past the regulating gates and keeps them clear of silt, at the same time furnishing the required amount of water. The regulator should not be located at a distance from the end of the weir; otherwise a dead water is created between the weir and the regulator in which deposits of silt occur, blocking the entrance to the canal and diminishing the volume available for its supply. An example of such faulty location is that illustrated GRANITE REEF REGULATOR 229 in Fig. 65, showing the head of the Ganges canal, where the front of the regulator is not at right angles to the weir and is at a short distance from it, resulting in the formation of a sand-bar at its entrance. A better arrangement would be a regulator built as indicated by the dotted outlines, with its face at right angles to the line of the weir. An illustration of faulty relation of weir to regulator is shown in Fig. 66 in the old Arizona canal hcadworks. The weir was built at an angle to the channel of the stream, and the regulator head was built at an angle both to the stream channel and to the FIG. 66. Old Arizona Canal. Plan of Headworks. weir, the result being to force a great pressure of water against the regulating gates, which seriously damaged them, while the deposition of sediment between the gates and weir was greatly encouraged. 203. Granite Reef Regulator. The regulator at the head of the new Arizona canal of the Reclamation Service, at Granite Reef, is an excellent example of good location and design. The weir (Art. 194) is set at right angles to the river channel and between it and the regulator head are a set of sluiceways (Art. 196) set in an extension of the weir, and separated from the latter by a training wall, at right angles to the weir axis, which directs the stream into the intake basin at the canal head and in front of the 230 SLUICEWAYS, REGULATORS, AND ESCAPES regulator. The sluiceways and regulator are in a straight line with the weir, a continuation of its axis (Fig. 50). Separating the line of the sluiceway and the intake basin is a concrete weir 220 feet in length, parallel to the training wall, 77 J feet from it, and with its crest at the same elevation, 1308 feet, or 2 feet lower than the crest of the main weir. The water falls over this 8 feet to the floor of the intake basin, the elevation of which is 1300 feet. The river bed above the weir and without the training wall has an elevation of 1295 f eet - Tne outer margin or bank of the intake basin, forming the abutment of the regulator gates, is a paved embankment curved on a radius of 116 feet, which is the width of the regulator, and having a crest elevation of 1325 feet, or 15 feet above that of the weir crest and sufficiently high to assure safety from topping by the greatest flood. 204. Classification of Regulators. The type of regulator employed depends upon the character of the foundation and the permanency deemed desirable. Regulators may be classified according to the design of the gate or the method by which it is operated. With nearly any type of foundation varying degrees of permanency may be given the superstructure and various methods may be employed for operating the gates. Accordingly regulators are classified here as follows: First, wooden gates in timber framing; second, wooden gates in masonry and iron framing; third, iron gates in masonry and iron framing. They are further classified, according to the method of operating the gates, as follows: First, flashboard gates; second, gates raised by hand lever; third, gates raised by chain and windlass; fourth, gates raised by screw gearing. Simple flashboard or needle gates should be used only where the pressure upon them is low. When under great pressure the opening should be closed by a simple sliding-gate raised by hand lever or windlass, or double gates, one above the other, may be employed, each separately raised by a screw and hand gear from above. 205. General Form of Regulator. The regulator should be so constructed that the amount of water admitted to the canal can be easily controlled at any stage of the stream. This can ARRANGEMENT OF CANAL HEAD 231 be done only by having gates of such dimensions that they can be quickly opened or closed as desired. Accordingly, when the canal is large and its width great the regulator should be divided into several openings, each closed by a separate and independ- ent gate. The width of these openings should be rarely less than 2 feet nor more than 8 feet. The channel of the regulator way should consist of a flooring of timber or masonry to protect the bottom against the erosive action of the water, and of side walls or wings of similar material to protect the banks. The various openings will be separated by piers of wood, iron, or masonry, and the amount of obstruction which they offer to the channel should be a minimum, in order that the width of the regulator head shall be as small as possible for the desired amount of open- ing. For convenience in operation it is customary to surmount the regulator by arches of masonry or a flooring of wood, iron, or reinforced concrete, so as to give an overhead bridge from which the gates may be handled. Lastly, the height of the regulating gates and the height of the bridge surmounting them must exceed the height of the weir crest by the amount of the greatest afflux height which the floods may attain, in order that these shall not top the regulator and destroy the canal. The regulator must be firmly and substantially constructed to withstand the pressure of great floods, and a drift fender or boom should be built immedi- ately in front of or at a little distance in advance of the gates. Wooden regulator heads are usually constructed much as are open flumes, arid consist of a fluming or boxing of timber lined with planks on the bottom and sides and with cross bracing above. In this are set the piers and gates. 206. Arrangement of Canal Head. As already shown, the regulator gates should be as close as possible to the end of the weir in order to prevent the deposit of silt at this point. Owing to the character of the banks and to avoid excessive cost in con- struction, it is sometimes necessary to set the regulatorjback in the canal a short distance. In such cases an escape should be in- troduced in front of and adjacent to it to relieve it of pressure and aid in its effective operation. At the head of the Cavour canal, Italy, the regulator is set 232 SLUICEWAYS, REGULATORS, AND ESCAPES back in the head cut, and immediately in front of it is placed an escape discharging into the river. At the head of the Turlock canal in California the flood heights are so great that the water may rise above the weir crest to a height of 16 feet. In order to relieve the gates of this pressure the canal heads directly in a tun- nel which is 560 feet in length and 12 feet wide at the bottom and is cut through the solid rock. It discharges into an open rock cut across which is placed the regulator, while immediately above and at right angles to it are a series of escape gates discharging back into the river. The wasting capacity of this escape is made greater than the possible discharge of the tunnel under the great- est head of water, so that the regulator gates are relieved of most of the pressure. There is a similar arrangement at the headworks of the Uncompahgre canals in Colorado. The main canal is sup- plied with water from the Gunnison River through a tunnel 30,- 583 feet in length, 10 by 10 feet in section and having a capacity of 1300 second-feet and a slope of 2 feet in 1000. At the lower portal the canal head is controlled by a regulator and escape. 207. Wooden Flashboard Regulators. Simple flashboard regulators are constructed as are flashboard weirs. A satisfac- tory regulator of this kind is that at the head of the Calloway canal in California, which is almost identical in Construction with the weir (Fig. 29) and therefore scarcely requires description. It consists of a wooden fluming having a rectangular cross-section built into the canal head and resting on piles and protected by sheet piling. Above and below this regulator head are built a wooden flooring and wings to prevent erosion. Flashboards are laid in the regulator head and can be removed or replaced one at a time, according to the amount of water to be admitted. The canal regulator on the Arizona side of the Laguna weir (Art. 194) is nearly parallel to the course of the Colorado River at this point (Fig. 55) and at right angles to the line of sluiceways. It is 219 feet in length and consists of 34 openings, each 7 feet 6 inches wide by 10 feet 7 inches high, in the clear, separated by reinforced concrete piers one foot in thickness and topped by a bridge of the same material. The width of the concrete flooring I I I I S33F "I" "T" ~T. H h- -+- H- 1 c I 234 SLUICEWAYS, REGULATORS, AND ESCAPES under the regulator is 17 feet and its thickness 6 inches. The gates consist of 18 planks or flashboards of Oregon pine 4 inches x 6 inches x 8 feet to each opening. These are removed or replaced one at a time by hooked poles and carried on a car travelling the length of the over- head bridge (Fig. 67). The effect is to let the clearer water into the canal by skimming it from the top of the river. 208. Wooden Gate lifted by Windlass. One of the most notable examples of this type of gate is that at the head of the Ganges canal in India, the regu- lator of which is of masonry, the gates being separated by masonry piers. The head on the gates is such that it is necessary to have three tiers of gates one above the other, the most advanced or up-stream gate having its sill on FIG. 68. Regulator Gates, Ganges Canal. Lover an Cafe full cjecn. Both yatt optn FIG. 69. Regulator Gates, Soane Canal, India. a level with the canal-bed and the two higher gates having their sills each 6 feet higher, while they retrograde toward the face of the bridge by the width of a gate. On the bridge above are two GATE LIFTED BY TRAVELLING WINCH 235 simple horizontal wooden windlasses, and the gates are raised by turning these. 209. Gate Lifted by Travelling Winch. This is the most common form of gate employed in India, where the width of canal head is great and the number of openings correspondingly large, as also at the Laguna weir, Colorado River. (Art. 195.) As shown in Fig. 69, for the Soane canal regulator, the gate is con- structed of wood, cross-braced, and to its top are attached chains which run over the windlass of the travelling winch. Above these FIG. 70. Wooden Lever and Screw Regulator Gates. gates is a bridge, and on the parapet immediately over the gates is a simple railroad track on which a handcar is run. On this is placed a simple hand winch, and by turning this each gate can be successively raised or lowered and the winch pushed along to the next gate. 210. Gate Raised by Gearing or Screw. This is the most usual type of gate in this country and abroad. They are em- ployed where there is some pressure to be overcome and as they are slow in operation, gates raised by levers are generally inserted in a few of the openings (Fig. 70), to be used when the pressure 236 SLUICEWAYS, REGULATORS, AND ESCAPES is light, geared gates being employed in the remainder. Above the gate projects a heavy steel screw, and this passes through a female screw of bronze or malleable iron on which the wear is taken up. As the pressure which this gate has to withstand is high, the simple screw is not sufficient, and the female screw forms the inner surface or axis of a geared or cogged wheel which is turned by a smaller cog operated by a hand wheel; thus the gate, while moving very slowly, can be raised with the application of but a trifling amount of power, owing to the multiplicity of gearing .Standard gate stand /furnished by U.S.R.S. SECTIONAL ELEVATION FIG. 71. Regulator Gate, Leasburg Canal, Rio Grande, N. Mex. employed. This type of gate, as adopted for the Reclamation Service, is illustrated in the wooden gate at the head of the Leas- burg canal, New Mexico Texas (Figs. 71 and 72). The corres- ponding iron gate is illustrated in the headworks of the Minidoka canal, Idaho (Fig. 73). In this the screw is threaded at the lower end and works in nuts fastened to the gate, thus lifting it. 211. Inclined, Horizontally Pivoted Falling Gates. The regulator heads to some of the branch canals on the Goulburn Irrigation System, Australia, consist of a series of fourteen gates each 7 feet high by 10 feet wide, placed across the channel and INCLINED, HORIZONTALLY PIVOTED FALLING GATES 237 arranged to maintain the surface of the water at the offtakes at any desired height. The gates are of wrought iron, fitted with rollers at the head, worked in vertical recesses in cast-iron piers and on roller bearings carried on horizontal shafts, supported on pedestals secured to the stonework in the masonry bed of the regulator head and to the piers (Fig. 74). These roller bearings are a little below the lower third of the gates. The motion of the gates is peculiar, being vertical at the head, forward in raising and CROSS SECTION DETAILS OF GATE FIG. ^^. FIG. 72. FIG. 72. Wooden Gate/Leasburg Canal Regulator, Rio Grande, N. Mex. FIG. 73. Iron Regulator Gate, Minidoka Canal, Idaho. backward in lowering on the roller bearings so that the pressure on them may be nearly balanced in all positions and so that a mini- mum power may be required to work them. Each gate is manip- ulated by separate gearing, consisting of a screw shaft with eye- and-pin connection to the gate-head, worked by a bevel-wheel gearing into a pinion operated by windlass from the bridge above. One of the most desirable results of this form of regulator head is 238 SLUICEWAYS, REGULATORS, AND ESCAPES Scale I I I I I I/ PLATE XII. Elevation and Cross-section of Weir and Regulator, Bear River Canal, Idaho. HYDRAULIC LIFTING GATES 239 in the fact that the water is drawn off the surface of the canal, and thus is freer of silt than if it were taken from the bottom. 212. Hydraulic Lifting Gates. At the head of the Folsom canal in California the regulating gates are operated by hy- draulic power from an accumulator fed by water-power from a fall in the canal. This regulator is constructed in the most substantial manner of granite masonry, and has a total width of 66 feet between abutments. The gates CP1. XIII) are three in number, each 16 feet in width and 14 feet in height to the crest of a semicircular arch, and are separated by masonry piers 6 feet in thickness. They are of wood, well braced, and slide vertically in grooves let into the masonry piers separating them. One hydraulic jack is attached to each gate, and its cylin- der is fastened to the masonry above. In this works a steel plunger having a 1 4-foot stroke and directly connected at its lower end with the gate. 213. Wasteways. In order to establish complete control over the water in a canal channel provisions should be made for dis- posing of any excess which may arise from sudden rains or floods or from water not required for irrigation. This is effected by means of escapes, or, as they are more commonly called in this country, wasteways or spillways. These are short cuts from the canal to some natural drainageway into which the excess of water can be discharged. Wasteways perform the additional service of flushing the canal and thus preventing or scouring out silt deposits. If the heads of distributaries be opened the>i relieve the main canal, and the former are in turn relieved by opening the waste- ways; hence the distributary heads act as the safety-valves and the wasteways as the waste-pipes of a canal system. Wasteways should be provided at intervals along the entire canal line, the lengths of the intervals depending on the topography of the sur- rounding country, the danger from floods or inlet drainage, and the dimensions of the canal. On large canal systems in India it is customary to place them at intervals from 20 to 40 miles. In our own country they are placed more frequently, usually 10 to 20 miles apart. Where the regulator head is placed back from 240 SLUICEWAYS, REGULATORS, AND ESCAPES the river a short distance, as in the case of the Cavour, Uncom- pahgre, and Turlock canals, a wasteway should be provided immediately above the regulator head for the discharge of surplus water and to keep the channel free from silt. The first or main wasteway on a canal line should be at a distance not greater than half a mile from the regulator, in order that in case of accident to the canal the water may immediately be drawn off. This main wasteway has the additional advantage of acting as a flushing gate for the prevention and removal of silt deposits. Where used for the latter purpose it is customary to decrease the slope of the canal between its head and the escape, in order that matter carried in suspension may be deposited at that point. 214. Location and Characteristics of Wasteways. Waste- ways should be located above weak points, as embankments, flumes, etc., that the canal may be quickly emptied in case of accident. Their position should be so chosen that the waste channels through which they discharge shall be of the shortest possible length. These must have sufficient discharge to carry off the whole body of water which may reach them from both directions, so that if necessary the canal below the escape may be laid bare for repairs while it is still in operation above. The greatest source of danger to canals is during local rains, when the irrigator ceases to use the water, thus leaving the canal supply full, while its discharge is augmented by the flood waters. Hence it is essential that, where a drainage inlet enters the canal, a wasteway be placed opposite for the discharge of surplus water. During floods the wasteway acts in relieving the canal as though the head regulator had been brought that much nearer the point of application. That the wasteway may act most effectively the slope of its bed should be increased by at least 12 inches immedi- ately below its head, in addition to which the slope of the re- mainder of the bed should be a little greater than that of the canal, and it should tail into the drainage channel with a drop of a few feet. Wasteways are sometimes built in the sides of flumes, thereby avoiding the expense of constructing a waste channel, as the water is discharged immediately into the drainage channel beneath the flume. While this practice is economical and may LOCATION AND CHARACTERISTICS OF WASTEWAYS 241 P* bC 242 SLUICEWAYS, REGULATORS, AND ESCAPES serve well where cheap construction is necessary, it is far from the best method unless great care is taken. The water falling from the flume may damage its foundations while the wasteway does not add to the security of the structure in which it is placed, and does not shut off the water above it. 215. Design of Escape Heads. Spillways and the regulators placed in the canal adjacent to and below them are built on similar designs to the main regulating gates at the head of the canal. A maximum limit is given to the dimensions of each gate, and as many are inserted as are necessary to pass the entire dis- charge of the canal without obstructing its velocity. These gates may be of wood or iron, and may be framed between timber, iron, or masonry piers and abutments. They are operated as are the head regulating gates; but as the pressure on them is never great some simple form of lifting apparatus, as flashboards or sliding gates raised by hand lever, windlass, or simple screw, is sufficiently effective. On the Galloway canal in California wood en flashboard escape- gates are used which are similar to the Galloway falls and regu- lating gates (Fig. 29). On the Highline canal in Colorado the first main wasteway is in the bench flume 600 feet below the head regulator, and consists of a set of four wooden gates, each 3 by 4 feet, set into the side of the flume and raised by simple rack and pinion (PL XIX). In the flume below and adjacent to this are a set of flashboard checks for regulating the discharge of the canal, or of closing it and forcing all the water through the waste- way. On the Bear River canal, Utah, there are two head waste- ways, one 1 200 feet and the other 1800 feet below the head regula- ting gates, and discharging back over the canyon sides into the river. Each of these has 12 feet of clear opening closed by three wooden gates sliding between iron posts and raised by screw gearing. Below and adjacent to the lower wasteway is a set of regulating gates in the canal. On the line of the Turlock canal abundant wasteway has been provided, as the canal flows in natural drainage channels for a portion of its course. One of these, Dry Creek, has a large catch- ment basin, and the diverting dam which turns the water back DESIGN OF ESCAPE HEADS 243 244 SLUICEWAYS, REGULATORS, AND ESCAPES into the canal is provided with a spillway 51 feet in length, be- sides a wasteway, 30 feet in length. An interesting wasteway on this canal is in the bottom of the flume crossing Peasley Creek. This flume is 20 feet wide and 7 feet deep, and is carried on a trestle 60 feet in height above the stream bed. In the flume bottom is built an escape which is of capacity sufficient to dis- charge the full volume of water in the flume. It is built by laying an iron beam across the flume bed, and this revolves on an axis turned by means of a hand wheel, thus converting a portion of the floor into a revolving gate by opening the bottom of the flume for its entire width. Beneath this gate is a receiving box which TRANSVERSE SECTION LONGITUDINAL SECTION FIG. 75. Escape-flume on Goulburn Canal, Australia. discharges up and down stream into two inclined wooden flumes which lead the water into the creek. Escapes are provided on the Goulburn canal in Australia by building them in the floors of the flumes which cross occasional drainage lines. The first is in the seventh mile and consists of three openings in the floor of the flume, fitted with valves opening downward and worked from a gangway above by screw and lever gearing (Fig. 75). These escapes serve the purpose of regulating the supply by disposing of surplus water, and also act as sand gates. 216. Wasteways, Reclamation Service. Reinforced concrete is used extensively by the Reclamation Service to protect canal banks or earth slopes at wasteway openings, as on all other structures on these government works. A type of the smaller WASTEWAYS, RECLAMATION SERVICE 2 45 wasteway in canal banks is that in the Fort Shaw canal, Montana (Fig. 76). On the canal side is a vertical wall of concrete 3 feet high and 8 inches thick, reaching below the level of the canal bed. PLAN SCALE OF FCF.1 1 1 * 4 & 10 H*L 8ML9 X^* "V. ** n S _j^8 SECTION FlG. 76. Spillway, Fort Shaw Canal, Montana. This supports the lower edge of the 4" reinforced concrete floor of the spillway opening which reaches to maximum water level and slopes thence beyond the outer bank. On the Lower Yellowstone canal, North Dakota (Fig. 77), this form of spillway is slightly Present Surface of Ground Structure to be reinforced throughout with )$"sq. steel bars spaced 12 Vs both way. equidirt. from concrete faces FIG. 77. Standard Sluiceway, Lower Yellowstone Canal, Montana-North Dakota. modified and the concrete flooring is 6 inches in thickness. The reinforcement in both cases is of \ inch square steel spaced 12 inches centers both ways. The latter wasteway discharges into 246 SLUICEWAYS, REGULATORS, AND ESCAPES a third channel paralleling the canal for a short distance and turning .thence down slope to a drainage channel. A by-pass between the storage feed canal and one of the main canals on the Umatilla project, Oregon, is not dissimilar in design to a wasteway excepting that its entrance is closed by regulator gates for control of the volume of water passed to the distributary canal. The total fall between canals is 15 feet, the slope of the 6-inch reinforced concrete floor being 3 to i near the top and 4 Fig. 78. Pine Ridge Sluiceway, Interstate Canal, Nebraska-Wyoming. to i below, and its length 85 feet (Fig. 79). The lower end of the wasteway is closed by a concrete weir 8 ft. high, the crest of which is about i ft. above the water surface in the lower canal. The sloping floor is supported at intervals of about 15 feet by concrete cross walls 3 feet high and 12 inches thick. 217. Taintor Circular Wasteway Gates. On the Lower Truckee canal are two main wasteways, the first or upper of which is 4.6 miles from the head. The lined canal section ad- joining the wasteway basin has 20.8 feet base and i to i slopes. f TAINTOR CIRCULAR WASTEWAY GATES 247 248 SLUICEWAYS, REGULATORS, AND ESCAPES The basin is formed by dropping the canal bed 6 feet vertically for a distance of 45 feet and by widening it on the lower side, making a chamber 45 by about 36 feet on the bottom and 19 feet deep when the canal is full. In the wall forming the lower side of the basin are five wasteway openings, each 5 by 5 feet in the clear with a head of 14 feet over the top. The openings are separated by piers 4 feet wide and lofeet long, the spaces between the piers, above the top of the openings, being closed up by 2 feet of reinforced concrete set back 2 feet from the upper edge of the piers. The passage of water through each of the five openings is regulated by a gate of the Taintor pattern, which consists of a circular arc revolving around a horizontal shaft, to which it is attached by radial arms, the whole forming in outline a sector of a circle. The arc is convex toward the water pressure, which is transmitted as thrust by the radial arms directly to the shaft. The center of the shaft is at the same level as the top of the gate opening. The radius to the outside or bearing surface of gate is 7 feet 5! inches. The arc has a net length of 5 feet 5 inches, and subtends an angle of 41 53'. The required net horizontal length of the gate surface is 5 feet. The steel shaft is 4 inches in diameter and 7 feet, if inches in length. From the shaft radiate three cross frames, constructed of 3 by 3 by J inch angle irons. At the outer ends these support the circular part of the gate which is built up of angles, plates, and 5-inch I-beams. The sheathing by which the water is excluded is of one-fourth inch steel plate. When entirely closed the lower end of the gate has a contact of about 4 inches with a guide strip set in the floor, and the upper end has a light contact with a strip next to the top of the opening. The side edges of the gate also have contact with corresponding strips on the sides of the concrete piers. The lower portion of the piers for over 5 inches on each side is recessed, to make room for the full width of the gates, which is about 5! feet. The contact or bearing surfaces of the gate and the guides are made of bronze 5/6-inch thick. The gate is raised by a i^-inch steel- wire cable, attached to its upper edge. The cable extends upward to and around a TAINTOR CIRCULAR WASTEWAY GATES 249 2 5 SLUICEWAYS, REGULATORS, AND ESCAPES grooved drum on top of the wall between piers. The drums for all the gates are keyed with a 2j-inch steel shaft. Power is applied to the shaft through a pinion and geared wheel at either end of this shaft, which is 43^ feet long. The pinion is turned by a crank by hand. The crank radius is 18 inches, the pinion is about 6 inches and the geared wheel 32 inches in diameter, while the drum is 8 inches, making the multiplication of power 24. The power available for lifting a gate, even if each of the two FIG. 8 1. Cross-section of Sand-box, Santa Ana Canal. gears be worked, is too small to readily lift the gate without some other aid. The entire length of shaft has to be turned, and con- siderable power is required for this alone, besides overcoming other frictions. The gates are counterweighted as follows: A TV-inch cable leads from the same point of attachment up to two 1 8-inch sheaves, on a level with top of the piers and 3 feet apart. From the rear sheave depends a bucket of 15 cu. ft. capacity, which may be filled with water to nearly counterweigh the gate. 218. Sand-gates. Sand-gates are practically waste-gates, though they are so designed and arranged in some canals as to SAND-GATES be of service only in scouring or removing silt deposits. The main or head wasteway on a canal system acts as a sand-gate, and is generally built as much for the purpose of flushing and scouring sediment as for the control of water in the canal. The gate in the Highline flume acts effectively as a sand-gate, because a board check from i to 2 feet in height is placed across the flume below the escape head. This causes the deposit of silt immediately above it, whence it can be removed by the scour through the escape. Careful provision has been made for the removal of silt on the Folsom canal. Immediately in front of and above the regu- lating head is a set of four sand- gates placed 6 feet below the grade of the canal and discharg- ing directly back into the river. These are practically undersluice gates, and are each 5 by 6 feet in the clear and set in substan- tial masonry. Sediment which is dropped into the subgrade in the canal opposite these gates is scoured out through them. In addition to these sand-gates, seven others are placed in the first 1700 feet of the canal. These are all similar in construc- tion, 5 feet wide by 10 feet high, 252 SLUICEWAYS, REGULATORS, AND ESCAPES framed in substantial masonry, and consist of iron gates sliding vertically and raised by means of a hand wheel and endless screw working on ratchets set on the back of the gate. Across the bed of the canal opposite and below each of these sand-gates is a subchannel and catch-basin i foot in depth, the object of which is to collect silt which is afterwards scoured out through the gates. An excellent though expensive form of sand-gate is that on I -1^" Single Thread TOP VIEW VA Steel g "w ft s 6 'x 6 "Wooden Sill e -ll-r-U. n -u- * d FRONT VIEW SEC. C-d SEC. a-b FIG. 83. Cast-iron Sluice-gate, Interstate Canal, Nebraska-Wyoming. the Santa Ana canal. The main feature of this is the sand-box or enlargement of the canal in which the sediment is caused to be deposited. These sand-boxes are placed on the line of a flume, and into them the water is discharged, and because of their increased cross-section the velocity of the water is checked and the sediment deposited. The first sand-box is 60 feet long SAND-GATES 253 by 13 feet wide, and its floor slopes transversely (Fig. 81) and is broken into longitudinal profiles by three partitions, the level tops of which are 6 feet 6 inches below the surface level and are 15 feet apart from center to center. They are so arranged as to divide the bottom of the chamber into four compartments. To each of these sumps the bottom of the chamber slopes, and in each is located a hollow cast-iron cone sand-valve, which opens down into a culvert leading to an escapeway. Sluiceways of standard pattern are provided on the lower Yellowstone canal which are so designed as to perform also the offices of sand-gates. In the line of the canal, at convenient K -8'o ? -U Canal Water Surface FIG. 84. Sand Box, Leasburg Canal, Rio Grande, New Mexico. crossings of depressions, are basins of reinforced concrete de- pressed 5 feet below the level of the canal bed, the width of the basin parallel to the line of canal being 26 ft. at top and 12 ft. at bottom. In these sediment will settle and they may be dis- charged, flushing the sediment or wasting the canal water as desired, through two openings 5' wide and 12 ft. high, controlled by iron gates operated from an overhead bridge by standard Reclamation Service screw and cogged gearing (Figs. 82 and 83). On the Leasburg canal of the Reclamation Service in New Mexico is quite an elaborate sand-gate of reinforced concrete, necessitated by the heavy deposits of silt left by the waters of the Rio Grande. There is a sand-box or depression in the line of the canal, of 3 feet depth. This discharges through a culvert 254 SLUICEWAYS, REGULATORS, AND ESCAPES 19 feet wide by 2 J feet high under the canal bank. The entrance to this culvert is in a concrete retaining wall supporting the canal bank, and is controlled by four ribbed iron gates 3 feet 6 inches wide by 2 feet 8 inches high. When raised the canal water flushes out the sand collected in the canal bed or sand-box. The canal bed approaching the sand-box is 2 feet 6 inches lower than beyond the box. Hence the total depth of the sand-box on the down stream side is 5 feet. CHAPTER XII FALLS AND DRAINAGE WORKS 219. Excessive Slope. As the fall of the country through which a canal runs is usually greater than the slope of the canal, the tendency of the water in the latter is to erode its bed. When this erosive action is extended to long reaches of the channel it produces retrogression of levels. If the canal is straight little harm is done, other than to cause the level of the water to sink below the ground surface and impede its diversion. Where it is necessary to divert the water, or where there are curves which the increased erosive action of the water would injure, it becomes necessary to compensate for the difference between the slope of the country and the canal-bed, so as to reduce the velocity. This is done by concentrating the difference of slope in a few points where vertical falls or rapids are introduced. The location of these is usually fixed by the place where the canal comes too high above the surface of the ground, while their distance apart is so arranged that they shall not have an excessive height or fall. If a canal can be so located and aligned that it will skirt the slopes of the country on a grade contour, it becomes possible to give it the most desirable slope throughout its length without the introduc- tion of falls; but where it runs down the slope of the country, compensation must be made for the difference between the ex- cessive ground slope over that of the canal. 220. Falls and Rapids. There are two general methods of compensating for slope; one is by the introduction of vertical drops or falls, and the other by the use of inclined rapids or chutes. Falls and rapids are of various kinds and may be generally classi- fied according as they are of wood or masonry. In design the fall may be of three general types: i, it may have a clear vertical drop to a wooden or masonry apron; 2, the lower face of the fall may be given an ogee-shaped curve (Article 176), with the object 255 256 FALLS AND DRAINAGE WORKS of diminishing the velocity and consequent erosive action of the water; 3, the water may plunge into a water-cushion (Article 177). To prevent the scour above the fall induced by the increased velocity of approach: i, a flashboard weir may be erected at the crest; 2, the channel may be contracted, or 3, gratings may be introduced. To prevent the erosive action in the lower level at the foot of the fall a water-cushion may be employed, or the chan- nel may be increased in width, terminating in wings which shall deflect the eddies back against the fall. 221. Retarding Velocity by Flashboards on Fall Crest The effect of a fall is to increase the velocity and to diminish the depth of water for some distance above it. This increase of velocity produces a dangerous scour on the bed and banks of the canal, which in a properly constructed fall is guarded against by means of flashboards or by narrowing the width of the channel. The height to which it is necessary to raise the crest of the fall is found by the following formula devised by Colonel J. H. Dyas of the Indian Engineers : 2^)'-- MS .8i M ?l, .... (4) in which h == height in feet of the water surface above the crest of the fall; a = the sectional area of the open channel in square feet; r = the hydraulic mean depth of the same in feet ; / = the length of the crest of the fall in feet ; / = the length of slope to a fall of one in the same. This formula has been somewhat modified by Mr. P. J. Flynn in order to make it agree with Kutter's formula. Mr. Flynn finds the discharge over the fall complete to be in which Q = the discharge in second-feet; c = the coefficient of discharge of open channel ; m = coefficient of discharge over a weir, and varies be- tween 2.5 and 3. 5; s = the sign of slope; and finally he gives the following: RETARDING VELOCITY BY CONTRACTING CHANNEL 257 If from this value of h we deduct the depth of water in the chan- nel, we have the height to which the weir must be raised above the bed of the canal in order that the water shall not increase in velocity in approaching the crest of the fall. 222. Retarding Velocity by Contracting Channel. If, instead of raising the crest of the fall, it is desired to narrow the channel above the fall in order to diminish the velocity of approach and the consequent erosive action, the amount of narrowing may be calculated by the common weir formula (No. 2) above given, and substituting for Q its value ac (rs) J, and transposing we finally get _ zagc :< ~ in which / is the length of the weir crest or the width of the chan- nel immediately above the fall, in feet. 223. Gratings to Retard Velocity of Approach. Gratings, for the purpose of retarding the velocity of approach to the crest of falls, are used with excellent results on some canals in India, and more recently by the Reclamation Service. They consist of a number of inclined bars placed just above the crest of the fall. The method of spacing these is such that the velocity of no one part of the stream shall be either increased or retarded by the proximity of the fall. The bars may be of wood or iron and rest on one or more overhead cross-beams and are laid at a slope of about i on 3, and are made of such length that the full supply level in the canal is half a foot below their ends. In canals with 6J feet depth of water the following dimensions have been used for the bars: lower end \ foot broad by \ of a foot deep; upper end J foot broad by j of a foot. They are supported on 12 -f 12 inch beams, and are placed such distance apart that 18 go into one lo-foot bay. According to the experience had in India vertical falls ter- minating in a water-cushion and having gratings above them are the best form that has yet been devised, the erosive action being diminished to a minimum. 17 2 5 8 FALLS AND DRAINAGE WORKS .JL- GRATINGS TO RETARD VELOCITY OF APPROACH 2 59 Such a fall is illustrated in the standard ic-foot drop built by the Reclamation Service on the Uncompahgre canal, Col. (Fig. 85). The canal banks and bed are lined with concrete for a distance of 20 feet above and 22 feet below the fall to prevent FIG. 86. Typical ro-foot Drop with Grating, South Canal, Uncompahgre Canal, Colorado. erosion, tapering in thickness from 6 to 12 inches. The effective height of drops is 10 feet but the total height of fall is 15 feet 6 inches to a water-cushion 20 feet in length and divided trans- 260 FALLS AND DRAINAGE WORKS versely half way by a concrete wall 10 feet in height to support the grating. This wall is pierced by two semicircular openings 7 feet 5 inches in height and 9 feet 10 inches in width to give free movement of the water (Fig. 86). The grating is of 40-pound rails spaced 8 inches between centers, slightly inclined up-stream, the lowest edge being 6 feet 10 inches above the floor of the ! . : , Top of bank 'JTop of bank Bottom width of canal * Riprap canal for |^Top of bank varying distances ELEVATION FIG. 87. Notch Fall, Interstate Canal, Nebraska-Wyoming. fall. This latter is i foot 6 inches in thickness and is reinforced with 1 6-pound rails spaced 24 inches centers both ways, their ends being turned up 2 feet into the concrete walls. 224. Notched Fall Crest. Great advantages have been found in India in adopting a notched form of canal fall, which practice has shown overcomes almost wholly the difficulties of excessive NOTCHED FALL CREST 26l CROSS SECTION FIG. 88. Notch Fall, Chenab Canal, India. 262 FALLS AND DRAINAGE WORKS velocity and erosive action below the fall. Notched falls have re- cently been adopted by the Reclamation Service as standard on the Interstate Canal, North Platte project (Fig. 87). The breast-wall or crest of the fall is cut away into a number of notches, the base of which are at a level with the canal-bed, the crest of the breast- wall being above full-supply level (Fig. 88). At the foot of each FIG. 89. Cross-section of Fall, Bear River Canal. notch is a lip projecting beyond the outer face of the breast- wall, which has an influence in retarding the stream and determining the form of the lower face of the falling water. The notches are all so designed as to discharge at any given level the same amount of water as the canal above carries at that level, so that VERTICAL FALL OF WOOD 263 there is approximately no increase in velocity in the canal as the water approaches the fall, while a uniform depth and flow are maintained. The water flows from the notches in a fanlike shape, and meets the water surface below in a steady stream, which contrasts favorably with the violent ebullitions which accom- pany clear overflows. The action on the banks of canals below the falls is very slight, and permits of the wings being of but mod- erate length. Mr. R. B. Buckley states there is no question of the superiority of this over all other forms of falls where it can be adopted. The form of the basin below the fall is practically that FIG. 90. Timber Drop, Lower Yellowstone Laterals, Montana. of a shallow water-cushion, it being widened in addition to check the ebullition of the water and reduce it to a steady forward velocity. 225. Vertical Fall of Wood. On the Galloway canal, Cali- fornia, simple flashboard checks are used for the falls. These checks are inclined at a slight angle to the vertical, and the water drops to a wooden apron resting on mudsills and protected by sheet piling at its ends, while the bank is protected by wings. On the Bear River canal, Utah, are a number of falls, ranging from 4 to 12 feet in height (Fig. 89). In these the flooring above and below the apron slopes down into the bed of the canal to 264 FALLS AND DRAINAGE WORKS prevent percolation. Wooden falls on the Lower Yellowstone canal laterals, like nearly all others built by the Reclamation Service, are when founded on piles, protected above and below by shallow sheet piling, and have water-cushions. The floors of these falls above the drop and below the water-cushion are covered to a depth of about afoot with gravel (Fig. 90). 226. Masonry Falls. In all the falls in India masonry work alone is used. These falls have sometimes simple vertical drops, at others they terminate in water-cushions (Fig. 90). In the larger falls of the Reclamation Service reinforced concrete is used, wood being adopted only for small drops on laterals. Nearly all have FIG. 91. Concrete Fall with Water Cushion, Truckee-Carson Canal, Nevada. water-cushions. It is customary in the case of wide canals to divide the falls into bays of 10 feet each, or thereabouts, by means of vertical partitions in order to prevent scour and back eddy and keep the water moving in a direct course. By this means each may be separately closed and repaired if necessary. An interesting series of two falls terminating in water-cushions on the Agra canal is shown in cross-section in Fig. 92. 227. Wooden Rapids or Chutes. A notable wooden rapid is the "Big Drop" on the Grand River canal in Colorado. The canal above the rapid is 30 feet wide and 4 feet deep, and is nar- rowed down at the head of an inclined flume which forms the 266 FALLS AND DRAINAGE WORKS rapid to a cross-section of 5 by 4 feet. The flume descends with a total fall of 35 feet in a length of 125 feet (Fig. 93), the water being discharged against a solid bulkhead of timbers which throws it back into a wooden penstock. From this it escapes over a riffled floor 1 6 feet in length, beyond which is an additional flooring 16 feet in length, whence it emerges in the open canal. Similar wooden chutes, but smaller, with falls of but 6 to 9 feet, have been built on laterals of the Buford-Trenton canals, North Dakota, by the Reclamation Service. In these the drop terminates in a wooden box forming a water-cushion. 228. Masonry Rapids. On the Bari Doab canal in India rapids paved with loose bowlders have been used with great suc- cess. The floors of these rapids (PL XIV) are confined between low masonry walls so as to prevent the movement of the loose bowlders, and the banks are protected by masonry wings. Bowl- ders form a better material for the flooring of a rapid than does brickwork, which could not safely be used with velocities exceed- ing 10 feet per second. The bowlder floors are grouted in mortar and will safely withstand a velocity of 15 feet per second. The tail walls of these rapids are peculiarly curved in order to turn back the current and protect the canal banks from the direct action of the water. On the Okanogan project of the Reclamation Service, Wash- ington, is a reinforced concrete rapid or chute of quite abrupt slope. The height of fall is 15 feet in a horizontal distance of 20 feet, to a water-cushion 9 feet long by 5 feet 9 inches deep (Fig. 94)- 229. Drainage Works. Where the diversion line of a canal is carried around the sides of hills or sloping ground, great difficul- ties are sometimes encountered in passing side drainage. The higher the canal heads up on a stream the more liable is it to encounter cross drainage. On low slopes much may be done by diverting the watercourses by cuts emptying into natural drain- age lines. When this cannot be done it may be passed in one of the following ways : 1. By drainage diversion; 2. Inlet dam; DRAINAGE WORKS 267 268 FALLS AND DRAINAGE WORKS 3. Level crossing; 4. Flume or aqueduct; 5. Superpassage ; 6. Culvert or inverted siphon. 230. Drainage Cuts. An instructive example of diversion by means of a drainage cut is the case of the Chuhi torrent on the Bari Doab canal in India. This torrent had two outlets, one run- ning into the Beas and the other into the Ravi River just above the canal crossing. The latter was embarked close to the bifur- cation by a bowlder dam, and by this means the water was forced down the Beas and the expense of crossing the canal saved. On the Betwa canal in India is another interesting diversion cut. The first six miles of this line are protected by a drainage channel 15 feet wide at the bottom and 6 feet deep, which runs parallel to the canal and catches the minor drainage from small streams, which it discharges into the Betwa River above the point of diver- sion of the canal. 231. Inlet Dams. Where the drainage encountered is inter- mittent and its volume is small relatively to that of the canal, much expensive construction may be saved by admitting the water directly into the canal and permitting it to be discharged through the first wasteway on its line. If the canal crosses a depression on a hillside, a heavy bank will of necessity be built on its lower side to keep its level at the desired height. The result will be to back the water up the drainage depression, thus causing waste, as the area of surface exposed to evaporation and seepage is in- creased. In such a case an inlet dam should be built on the upper side to confine the canal within reasonable limits. Inlet dams may be of wood, masonry, or loose stone. If the depth of the canal is small and the consequent height of over- flow from the crest of the dam to the canal-bed small, a wooden flume may be laid in the bed of the canal and a barrier or dam of piles and sheet-piling be built across the upper side. In a short time the sediment carried by the stream will fill in behind the dam to a level with its crest and the water will simply fall over it onto the canal floor. The inlet dam may be made as a loose rock retaining-wall, when the bed and banks of I 1 t P. c I I 270 FALLS AND DRAINAGE WORKS the canal below and opposite should be riprapped with stone to protect them from erosion. In case the drainage torrent is of some magnitude more sub- stantial works than this may be required, and it may be necessary to build a masonry inlet dam and perhaps to build a portion of the canal channel of masonry, revetting the opposite bank with loose stone. At the crossing of Reno Coulee by the Lower Yellow- stone canal, the Reclamation Service has constructed an inlet consisting of a heavy earth embankment set back 25 feet from the canal on the up-stream slope. In this the inlet heads in a masonry retaining wall and consists of a terra-cotta pipe 2 feet in diameter 69 feet long with a fall of 12 feet. It is supported at in- tervals of 20 feet by concrete walls or collars 6 ft. square and 18 inches in thickness. (Fig. 95.) At the point where the inlet pipe discharges into the canal the latter is paved with 12 inches of con- crete, and the opposite slope of the canal-bed for a short distance above and below are paved with riprap laid in cement and grouted. 232. Level Crossings. When the discharge of the drainage channel is large and it is encountered at the same level as the canal, it may be passed over, under, or through the latter. In the latter case the water is admitted by an inlet dam on one side and discharged through a wasteway in the opposite bank. The discharge capacity of the latter must be ample to pass the great- est flood volume likely to enter, and a set of regulating gates must be placed in the canal immediately below the escape in order that only the proper amount of water may be permitted to pass down the canal. The inlet dam must be constructed as described in Article 231, while the wasteway and gates should be built of the usual pattern. On the line of the Turlock canal in California are several level crossings of peculiar design, built where the canal skirts steep sidehill slopes, causing the embankment on the lower side to become practically a high earthen dam. The top of the bank is made a little higher, firmer, and wider than elsewhere along the canal line, and in the case of two of these drainage crossings no inlet dam has been constructed. As a result the water is retained LEVEL CROSSINGS 271 on the upper side of the canal as in a large reservoir. With a new canal this has no great disadvantage, as such construction saves considerable expense in the beginning, while in the course of a few years, and by the time the canal water becomes valuable, this reservoir will have silted up and the canal can then be confined between proper limits. These earthen drainage dams are of con- siderable height, one 23 feet and the other 40 feet high, and in them are constructed wasteways, for the discharge of surplus waters. The most interesting level crossing is that of the Rutmoo FIG. 96. Plan of Rutmoo Crossing, Ganges Canal, India. torrent on the Ganges canal in India. This consists of a simple inlet at the torrent entrance; of a masonry outlet dam; of an escape regulator in the opposite canal bank; and of a regulating bridge across the canal channel just below the inlet (Fig. 96). The escape dam consists of 47 sluiceways, each 10 feet wide, with their sills flush with the canal-bed and flanked on either side with overfalls of the same width with their sills 6 feet higher, while on the extreme flanks are platforms 10 feet above the canal-bed. 272 FALLS AND DRAINAGE WORKS The closing and opening of these sluiceways is accomplished by means of small flashboards fitting into grooves. 233. Flumes. Where drainage encountered is at a lower level than the bed of the canal, it may most conveniently be passed under the latter, which crosses over it in a flume. Care must be taken to study the discharge of the stream crossed in order that the waterway under the flume may be made ample to pass the largest flood which may occur. * The foundations of the flume must be substantial, 'and the area of waterway must not be greatly impeded; otherwise the velocity in the drainage channel will be so great as to cause scour of its bed and perhaps the destruction of the work. : Care must be exercised in connecting the ends of the flume with the canal banks on either side that leakage may not occur at these points. If the flume is built across a depression, expense in construc- tion is usually saved by limiting the length of the structure as much as possible. This is done by making its approaches on either side of earth embankment, on which the canal is carried. This must be carefully constructed and of ample width that it may not settle greatly or be washed away, and it must be faced with abutments and wing walls at its junction with the flume to protect the latter against erosion. That the dimensions of the flume may be as small as possible, its cross-section is generally diminished and it is given a slightly greater slope than the canal at either end to enable it to carry the required volume. A satisfactory method of connecting wooden flumes with canal banks consists in building a low vertical drop of 2 to 4 feet in the flume at its junction with the earth at either end, and then filling up to the level of the canal and flume-gate with earth. At either end of the drop, against the earth embankment and at the end of the flume proper, is placed sheet-piling, while the earth is care- fully tamped back of and about the drop. Another plan em- ployed with satisfaction, but more expensive of construction, is to build out at the end of the flume a couple of parallel rows of sheet- piling at right angles to the line of the flume and canal, and still another row meeting this at the junction with the flume is run out at 45, thus enclosing an angle in the canal bank between two 274 FALLS AND DRAINAGE WORKS rows of sheet-piling filled in with earth. Another way of making the connection, in conjunction with one of the methods above described, is that of putting in an inclined drop or apron running into the canal-bed, with sheet-piling at either end. Be the means employed what they may, the greatest care must always be ex- ercised in making the connection of flume ends with earth. 234. Sidehill Flumes. The simplest form of wooden flume is what is generally known as a bench flume, built on a steep side- hill to save the cost of canal excavation. Such flumes are com- mon in the West, notable examples being the bench flume on the Highline canal in Colorado (PL XV), the great San Diego flume in California. The former is a little over half a mile in length. It is 25 feet wide and 7 deep, its grade being 5^ feet per mile and its discharge 1184 second-feet. The San Diego flume was built chiefly to give the canal a more permanent waterway than earth and one less liable to the losses of evaporation and absorption. In this case fluming is employed for the entire length of the canal, which is 36 miles. The Santa Ana flume was built for similar reasons, and also because the rocky canyon wall on which it is aligned is in places too steep to permit of excavation or other form of channel within reasonable limits of expense. Such structures should never be built on embankments ; they should rest everywhere on excavated material or trestles to avoid the danger of subsidence and consequent destruction. This excavated bench should be several feet wider than the flume, in order to give a place on which loose rock from the sidehills may lodge without injury to the structure, and the flume itself should rest on a permanent foundation of mudsills or posts. 235. Construction of Flumes. The boxing of flumes is gen- erally of three types : 1. The floor may be built directly on stringers and the plank- ing be laid at right angles with the current of the stream. 2. The floor beams may be laid on stringers braced at inter- vals calculated to bear the water pressure; the standards and floor beams being boxed in and bolted to the outside braces, the whole forming the foundation for putting on the inside sheeting or boxing. STAVE AND BINDER FLUMES 275 3. The floor beams and stringers may be formed in cross beams yoked to receive the boxing. The lumber forming the boxing of the flume should be from ij to 2\ inches in thickness, according to the dimensions of the flume. It should be of good grade and well seasoned. The best practice is to match the various planks together either by ship-lap joints or driven tongue-joints, which, if shrinkage occurs, should be calked with oakum. An excellent example of bench flume is that of the San Diego Flume Company (Fig. 97), which is 6 feet wide in the clear and FIG. 97. Cross-section of San Diego Flume, California. 4 feet deep; the bottom and sides are planked with 2-inch red- wood, and the boxing rests on transverse sills of 2 -inch planking laid 4 feet apart, and upon these are 4 by 6 longitudinal stringers, above which is constructed the framework of the flume, consisting of 4 by 4 scantling placed at intervals of 4 feet and braced by diagonal uprights 2 by 4 inches and 3 feet in length. Another and even better type of flume is that shown in Fig. 98, being the standard type of wooden flume and trestle adopted by the Re- clamation Service. 236. Stave and Binder Flumes. This type of structure is curved in cross-section, and, as indicated by the title, is like the lower half of a wooden water-pipe (Article 277). It consists of wooden staves bound and held together in a rounded bottom by iron and steel ribs and binding-rods, acting in conjunction with wooden yokes or ties across the top (Fig. 98). In its simplest 276 FALLS AND DRAINAGE WORKS form this flume is semicircular, with the top edges braced apart by the stiff yoke or cross-head, so that there is no tendency of the shell to buckle inward. As developed on the Santa Ana canal, the sides are formed of broader boards which are carried up vertically in a line tangent to the ends of the bottom half -circle and to the desired height. Upon applying the binding com- pression on this form there is a tendency to buckle inward, which is obviated by stiff ribs made to serve as binders and introduced at intervals in the shell. This flume has not been successful, for, FIG. 98. Cross-section of Stave and Binder Flume, Santa Ana Canal. if not well filled with water, cracks open and sand gets in these, making it impossible to cinch them up water-tight again. 237. Flume Trestles. Where the flume crosses a depression it rests on trestles. (Fig. 99.) These are constructed as are the ordi- nary trestles on railway lines. Where the trestle rests on dry ground it may be founded on mudsills, on short posts let into the soil, or on concrete blocks, but where it crosses drainage channels it must be substantially founded on cribs, piling, or concrete. The superstructure of a flume crossing a drainage line is similar to that of bench flumes. 238. Iron Aqueducts. The chief difficulty encountered in constructing long aqueducts of iron has been the expansion and contraction of the metal, though in practice it has been found that IRON AQUEDUCTS 277 the metal of the structure has approximately the same tempera- ture as that of the water, and as this is somewhat uniform but little change takes place in the dimensions of the aqueduct. On the Bear River canal in Utah are two aqueducts, one of which consists of a wooden flume resting on iron trestles founded on masonry columns. The other is a simple iron aqueduct resting on iron trestles. The floor of this is 37 feet above the bed of the *'C.to C.- -4'c.to C.- DETAIL OF WEDGE AND YOKE ELEVATION FIG. 99. Standard Timber Flume and Trestle, U. S. Reclamation Service. stream, and its length is 130 feet (Fig. 100), disposed in three bents, the center span of which is 60 feet long, the other two being respectively 25 and 45 feet long. This aqueduct is essentially a plate-girder bridge resting on iron columns and founded on iron cylinders rilled with concrete and resting on piles. The plate girders forming the sides of the aqueduct are 5 J feet in depth, the available depth of water being 4 feet. The sides of the girder are braced by vertical angle-iron riveted to it every 5 feet apart, while 2 7 8 FALLS AND DRAINAGE WORKS the top is cross-braced by similar angle-iron. These angle-irons vary between 3 and 4 inches in width, while the web of the sides of the aqueduct consists of f -inch iron. On the Henares canal in Spain is an iron aqueduct over the Majanar torrent. This aqueduct is 70 feet long with a clear span l l l l l l ULJ FIG. 100. Elevation and Cross-section of Iron Flume on Corinne Branch, Bear River Canal, Utah. of 62 feet. Its waterway is 10.17 feet wide > its capacity being 177 second-feet. The sides are composed of box girders 6.2 feet deep (Fig. 101), and each girder is calculated to bear 200 tons or the entire structure to carry 400 tons. To prevent leakage the ends of the aqueduct rest on stone templates, and 4 inches from MASONRY AQUEDUCTS 279 each end is a pillow composed of long strips of felt carpet 9 inches wide and soaked in tallow, which is let into the stone below the aqueduct. This presses on it with its full weight, thus making a water-tight joint. In addition to this lead flushing is riveted to the aqueduct and let into a recess of the stone abutments. This recess is 1 2 inches deep and 4 inches wide, and around it is poured, Half Utvation of Aqueduct FIG. 101. Aqueduct, Henares Canal, Spain. hot, a mixture of tar, pitch, and sand, which allows slight play during its expansion and contraction and yet is water-tight. 239. Masonry Aqueducts. In general design masonry aque- ducts are planned and constructed much as are those of wood or iron. One of the greatest structures of this kind is the Solani aqueduct on the Ganges canal in India (PI. XVI). This consists of an earth embankment approach or terre plein 2 J miles in length across the Solani valley, its greatest height being 24 feet. This embankment is 350 feet wide at the base and 290 feet wide on top, and on this the canal banks are formed, the width of the banks MASONRY AQUEDUCTS 28l being 30 feet on top and the bed width of the canal 150 feet. The aqueduct is 920 feet in length with a clear water space between piers of 750 feet, disposed in fifteen spans of 50 feet each. The FIG. 102. Elevation and Cross-section of Nadrai Aqueduct, Lower Ganges Canal, India. breadth of each arch parallel to the channel of the river is 192 feet and its thickness 5 feet. The greatest height of the aqueduct above the river valley is 38 feet, and the walls of the waterway 282 FALLS AND DRAINAGE WORKS are 8 feet thick and 12 feet deep. This structure is founded on masonry piers resting on wells sunk 20 feet in the river-bed. Perhaps the most magnificent aqueduct ever built is that car- rying the Lower Ganges canal across the Kali Nadi torrent in Span varies from U to 30 Span 7 1 24 10' s'o IS 1 Tieton Cana1 ' Washington. and the thickness of walls and manner of reinforcing are such that no cross-bracing is necessary to hold the sides in position. On the Tieton project, Washington, a flume of semicircular cross-section is also used. This (Fig. 104) has thinner walls and these are therefore cross-braced with 4-inch square concrete beams 10 feet long and reinforced with two J-inch steel rods. The shell of the flume 154 inches thick reinforced circumferentially 284 FALLS AND DRAINAGE WORKS with f-inch steel rods spaced 4 inches centers and each ly long, and longitudinally by eighteen J-inch steel rods spaced 12 inches centers. The trestles are of reinforced concrete cross- braced with steel tie-rods. The concrete posts are 12 inches square reinforced with four J-inch steel rods and the caps and struts are 6 by 12 inches reinforced with two J-inch rods. On the Interstate canal, Nebraska, is a reinforced concrete aqueduct 206 feet long and 34 feet wide by 12 J feet deep inside, which is carried over Spring Canyon on a massive masonry multi- arched reinforced concrete bridge (Figs. 105 to 107). The walls 10 ;,p HALF SECTION SCALE OF FEET 10 20 FIG. 105, Half Longitudinal Section, Reinforced Concrete Aqueduct, Interstate Canal, Nebraska-Wyoming. of the aqueduct are ioj inches thick at top and 12 \ inches at bottom, and heavily reinforced with j- to i-inch rods as shown. The floor is 24 inches thick and is reinforced with i-inch steel rods spaced 6 inches centers and turned up two feet into the walls. The tops of the latter are cross-braced every 1 1 feet 9 inches with built-up steel lattice beams 16 inches deep and let well into and firmly bolted into the concrete walls. The foundations and columns of the supporting bridge are of massive concrete, the main arches being reinforced with two rows of i- to i i-inch steel rods spaced 2 ft. centers. The superimposed arches are reinforced with No. 10 gauge 4-inch mesh wire fabric. 241. Superpassages. Where the canal is at a lower level SUPERPASSAGES than the drainage channel, a superpassage is employed to carry the latter over the canal. This is practically an aqueduct, though there are some elements entering into its design which are different from those affecting aqueducts. The volumes of streams which are to be carried in superpassages are variable, at times they may be dry, while at others their flood discharges may be enormous. No provision has to be made for passing flood waters under the structure, since the discharge of the canal beneath it is fixed. Tin- longitudinal reinforcing rods of the flume are to t* carried 5-uinto SCALE OF FEET 7 8 fl 10 FIG. 106. Section Through Reinforced Concrete Aqueduct, Interstate Canal, Nebraska -Wyoming. On the other hand, the water-way of the superpassage must be made amply large to carry the greatest flood which may occur in the stream, and much care must be taken in joining the super- passage to the stream-bed above and below to prevent injury by the violent action of the flood waters. No instance can be cited where superpassages have been con- structed in the United States. In nearly every case where these would have been required the stream has been taken under the canal in an inverted siphon. In India, however, superpassages have frequently been used on the canals in preference to inverted siphons chiefly because of the requirements of navigation. It would probably be a dangerous experiment to attempt to 286 FALLS AND DRAINAGE WORKS construct a superpassage of wood, because it would be so con- stantly subjected to alternate drying and wetting, according as there was or was not water flowing in the stream, that it would soon decay. A small iron superpassage has been constructed across the Agra canal in India which is 99 feet long, 30 wide, 10 feet deep, of boiler-iron strongly cross-braced. It is supported on masonry piers and has a steep slope giving a high velocity. The connection between its ends and the abutments is made by means of heavy sheet lead to accommodate the changes due to expansion FIG. 107. Reinforced Concrete Aqueduct, Spring Canyon, Interstate Canal, Nebraska-Wyoming. of the iron. This precaution is more necessary in a superpassage than in an aqueduct, as it is more subject to changes of tempera- ture when empty. On the Ganges canal in India are two of the largest super- passages ever constructed. One carries the Puthri torrent and the other the Ranipur torrent over the canal. The discharge of the former amounts in times of flood to as much as 15,000 second- feet The Ranipur superpassage (PL XVII) is built of masonry PLATE XVIII. Idaho Irrigation Company's Canal. View of Wooden Siphon on Phyllis Branch. CULVERTS AND INVERTED SIPHONS 289 founded on wells, and its flooring, which is given a steep slope in order that the velocity shall pre- vent its filling up with sediment, is 3 feet in thickness above the crown of the arches and is bordered by parapets 7 feet wide and 4 feet high. The flooring and parapets continue inland from the body of the work a distance of 100 feet on each side, the latter expanding outward so as to form wings to keep the water within bounds. The superpassage is 300 feet long and provides a water-way 195 feet wide and 6 feet deep. 242. Culverts and Inverted Siphons. Where the canal is not used for purposes of navigation and encounters drainage at a relatively low level, the most convenient and usual form of crossing is by means of inverted siphons or culverts. Sometimes the canal is carried in a siphon under the stream, some- times the stream is carried in a culvert under the canal. The di- mensions of the culvert or siphon are to be computed by means of one of the many formulas for the flow of water through pipes (Arts. 273 to 275), though the formula for flow through open channels may also be used in some cases (Art. 78). Inverted siphons, or pressure-pipes are frequently em- ployed in crossing deep depressions 19 290 FALLS AND DRAINAGE WORKS CROSS SECTION FIG. 109. Soane Canal, India. Cross-section of Kao Nulla Siphon-aqueduct. FIG. no. Sections of Sesia Siphon, Cavour Canal, Italy / WOODEN CULVERT in place of flumes on high trestles. . This method is most satisfactory in crossing depressions carrying little drainage water. In some cases w r ooden pipe (PL XVIII), in others wrought- or cast-iron or reinforced concrete pipes are used. 243. Wooden Culvert. An ex- cellent example of a small work of this kind is the wooden culvert on the Del Norte canal in Colorado (Fig. 108). This consisted of two parallel wooden boxes, each 4 feet 6 inches wide by 3 feet high, sup- ported on piling and framed and braced with 6 by 8 scantling. The bottom and sides were floored with 2-inch plank, while the top which had to bear the weight of the super- incumbent earth and water, was covered with 6-inch planking laid crosswise. This culvert was recently washed away and has not been re- stored. 244. Inverted Siphons of Ma- sonry. An interesting structure of this kind is that carrying the Kao torrent under the Soane canal in India (Fig. 109). This work is built of the most substantial ma- sonry, the area of the superstructure being contracted and given a slightly increased grade to carry the waters of the canal, while the waters of the torrent flow over a masonry floor which is depressed a few feet. The most magnificent masonry 2 9 I / :,L- 292 FALLS AND DRAINAGE WORKS siphon ever built is that carrying the waters of the Cavour canal under the Sesia River in Italy. Its total length is 878 feet and it consists of five oval orifices (Fig. no), each 7.8 feet in height by 16.2 feet in width, the amount of depression of the water surface in the canal being 7^ feet. The siphon consists of a substantial concrete floor or foundation nj feet in thickness under the river-bed, its roof forming the floor of INVERTED SIPHONS OF MASONRY 293 the river channel and being about 3 feet in thickness. Another large siphon is that on the Sirhind canal in India crossing the Hurron torrent. The total length of this is 212 feet, and it con- PLATE XIX A. Inlet to Rawhide Siphon, Interstate Canal, Nebraska-Wyoming. PLATE XIX B. Siphon Crossing Under Rawhide Creek, Interstate Canal, Nebraska-Wyoming. sists of two openings each 4 feet high by 15 feet wide. The water drops from the canal almost vertically into a well, the floor of which is on a level with the floor of the siphon, while 294 FALLS AND DRAINAGE WORKS at its exit it is raised again to the level of the outlet canal up an incline built in steps. 245. Reinforced Concrete Culverts. On nearly every canal of the Reclamation Service are one or more culverts of reinforced concrete, this material and mode of crossing being generally adopted. Fig. in shows a longitudinal and cross-section of such a culvert built for passing the water of War Dance coulee under the Lower Yellowstone canal. The culvert consists of two rect- angular pipes each 3 by 5 feet with 1 2-inch reinforced concrete PART LONGITUDINAL SECTION Ji R.S C.to~C. 66 Longitudinal Rods y'i tf FIG. 113. Reinforced Concrete Twin Siphon, Dry Spotted Tail Creek, Interstate Canal, Nebraska-Wyoming. walls. At entrance and exit are reinforced concrete bays with paved approaches. At intervals along the culvert are heavy concrete collars to prevent travel of seepage water from the canal. 246. Reinforced Concrete Siphons. Like the culverts, the siphons built by the Reclamation Service are of reinforced con- crete. The Lower Yellowstone canal is carried under Fox Creek in a twin siphon of sewer or egg-shaped cross-section (Fig. 112). At entrance and exit are bays lined with concrete and with paved approaches. Three sets of concrete collars 18 inches thick and 5 feet deep are at either end to prevent seepage and below these is 4j-inch sheet piling. Each pipe is of 9 inches of concrete rein- forced circumferentially with bars \ to J inches square and 15 REINFORCED CONCRETE SIPHONS 295 to 17 inches centers, while longitudinal bars are spaced at in- tervals of about 1 8 inches. In the siphon is a blow-off of 10 inch pipe with reducer and valve. On the Interstate canal of the North Platte project arc sev- eral siphons, that under Rawhide creek being shown in Pis. XIX A and B, and cross and longitudinal sections of that under Dry Spotted Tail creek in Fig. 113. The latter is a twin siphon of rectangular section with curved invert. The walls are of con- crete 10 to 12 inches thick and are reinforced with two circum- ferential and one longitudinal rows of J inch bars. CHAPTER XIII DISTRIBUTARIES 247. Object and Types. Distributaries are to a main canal system what service pipes are to the mains in city water service. The minor or farm ditches, from which water is directly applied to the crops, should never be diverted from the main canal nor from its upper branches. It is desirable to have as few openings in the bank of the main canal as possible, so as to reduce to a minimum the liability of accident. The water is drawn at proper interval from the main line into moderate-sized branches which are so arranged as to command the greatest area of land and to supply the laterals and farm ditches in the most direct manner. Wherever water has not a high intrinsic value it is conducted to the lands in open distributaries and laterals. Where, however, its value is relatively high it is desirable to reduce the losses from absorption and evaporation to a minimum. In such cases the laterals consist of wooden flumes or of paved or masonry-lined earth channels, while in extreme cases, such as are encountered in Southern California, water is conducted underground to the point of application in pipes, and is applied to the crops from these instead of being flowed over the surface. By such methods of handling the highest possible duty is obtained .and the most effective use made of the water at command. 248. Location of Distributaries. Distribution from a canal is most economically effected when it runs along the summit of a ridge so that it can supply water to its branches, to laterals and to private channels on either side. In the case of main canals this location can be made only in occasional instances ; but the laterals taken from these mains should be made to conform to the dividing lines between watercourses. The capacity of the laterals which then traverse the separate drainage divides is proportioned to 296 DESIGN OF DISTRIBUTARIES 297 the duties they have to perform, the natural bounding streams limiting the area they have to irrigate. In designing a distributary system too little care and attention are ordinarily paid to its proper location and survey; yet it is in the distribution and handling of water that the greatest losses occur, and accordingly it is there that the greatest care should be taken in its transportation. Careful surveys should be made of the area to be traversed by the distributaries, as described in Arti- cle 138 for the location of main canals, and the greatest care FIG. 114. Diagram Illustrating Distributary System. should be taken to balance cuts and fills and to so locate the laterals that the least loss of water shall occur from percolation. In Fig. 114 is shown an ideal distributary system. The con- tour lines and drainage courses show the general slope and lay of the country, and the main canal and its branches should be run down the divides between these drainage lines as indicated. Such an arrangement enables the least mileage of channels to command the greatest area of country by furnishing water to both sides of its line. At the same time perfect drainage is ob- tained by the water flowing in both directions into the natural watercourses. 249. Design of Distributaries. For the more complete and efficient distribution of water the engineer treats laterals as of 298 DISTRIBUTARIES as much importance as the mains and branches. Attention is devoted to the character of the soil traversed, to the alignment, to the safe and permanent crossing of natural drainage lines, and especially to so maintaining the surface of the canal with relation to the ground as to command the largest irrigable area. In all well-designed distributary systems the capacity of the channels is exactly proportioned to the duty to be performed, the cross- High Lin* Pumping Station Arrow] Creek Crossing 5 FIG. 115. Distributary System, Huntley Canal, Montana. sectional area being diminished as the quantity of water is de- creased by its diversion to private watercourses. The lateral should be taken off from the main canal as near the surface of the latter as possible, the bed of the lateral not being on a level with the bed of the canal, bui; placed with refer- ence to the full supply of the main canal, in order to get the clearest water, and in order that the bed of the lateral may be kept at a high level and admit of surface irrigation throughout its length. In level country care should be taken in designing distributaries EFFICIENCY OF A CANAL 2QQ that the natural drainage lines into which they tail shall be sufficiently large to accommodate any flood volume it may be necessary to pour into them; otherwise the stream courses may become clogged and flood the surrounding country. On many of the Reclamation Service projects on very level lands (Fig. 1 15), the laterals for convenience follow the rectangular boundaries of the public land subdivision. In order to avoid the construction of costly embankments and to insure the surface of the water being above that of the country the slope of the lateral should be made as nearly parallel as possible to that of the land it traverses. To effect this alignment, falls must be frequently introduced, and to dispose of storm-waters, wasteways into natural drainage lines should be provided at least every 10 miles in the course of the lateral. 250. Efficiency of a Canal. According to Mr. J. S. Beres- ford, an Indian engineer, we may look upon a great canal system as a machine composed of four parts and calculate its efficiency in the same way as that of a steam-engine. These parts are: 1. The main canal. 2. The distributaries. 3. The private irrigating channels. 4. The cultivators who supply the water to the soil. Each cubic foot of water entering the canal head is expended in five ways : 1. In waste by absorption and evaporation in passing from the canal head to the distributary head. 2. In waste from the same causes between the distributary head and the head of the private channel. 3. In waste from the same causes in passing from the private channel to the field to be watered. 4. In waste by the cultivators in handling the water, both by causing losses from evaporation or from percolation where an unnecessary amount is applied. 5. In useful irrigation of the land. The object is plainly to increase the last item by the reduction of all the rest. Calling D l the theoretic duty of a foot of water entering the canal head, we have the actual duty of the canal. 300 DISTRIBUTARIES ....... (i) where C me represents the mean efficiency of the main canal. Now if the efficiency of water entering a distributary head for use in watering a field from an outlet is called A, the duty of water used in this field will be D = EXD> ........ (2) and E = E d xE w xE c , ...... (3) where E d is the efficiency of the distributary, E w is the efficiency of the private watercourse between its heap! and the field, and E c is the efficiency of the cultivator who waters the field. The efficiency of any distributary is the fraction whose denom- inator is the quantity entering the distributary head, and the numerator this same quantity minus the loss down to the point in question. If W represents the waste down to any outlet, Q the discharge at the head of the distributary, and E the efficiency at the point under consideration, then - 2 T L 7 ..... > The waste W down to any point may approximately be ex- pressed as the product of the loss of the first mile into some func- tion of the length, or W = APXL X - ....... (5) or substituting in the above equation, we get APXL* E =i- -- , ..... (6) where AP is the ascertained loss by absorption and percolation in the first mile and L x is some function of the length, which will be found by experiment to be about f or f of L in most cases, or near the head of the distributary Z, 1 . Taking / as the length of the private watercourse, q as its discharge, and I* as the same function of its length as in the case of L x , we have the efficiency of the private channel *-ii^22i. (7) EFFICIENCY OF A CANAL 301 The efficiency of the cultivator E varies between .5 and .9 where unity represents his efficiency at the theoretical limit. Now for an outlet at the head of the distributary and with the irrigating field close to this outlet, L = o and / = o. Therefore the second terms of the equations (6) and (7) vanish and E and E each = i , and for L or / very great, E or E* = o. An application of these rules as laid down by Mr. Beres- ford is given in the following cases: Say the discharge Q= 50 cubic feet ; that the outlet is at the tenth mile, whence L = 10; the losses from percolation, etc., being 1.25 in the first mile and x = ,f. The discharge of the watercourse q=i cubic foot, 1 = 6 furlongs, and ap = .03 of a cubic foot per furlong. Then I.2S X 10* .829; 50 X .820. i Say *-. 75 and = .829 X .82 X .75= .51; or leaving out the cultivator, this is equal to .68. That is, of each cubic foot entering the distributary head only .68 of a cubic foot is available at the tenth mile and 6 furlongs. Whatever the actual amount of loss in either distributary or private channel, it varies directly with L and /; it also varies directly with AP and ap, and great waste is due to the cultivator if he is careless. It will thus be seen from the above that every effort should be made to reduce the value of AP and to induce the cultivator to use the greatest possible care in handling the water. From the above it is evident that the widest field for improve- ment is in the private watercourses. These, generally, are much longer than is necessary and are usually so constructed as to avoid low lands, whereas flumes or proper alignment would remedy this. They often run long distances through sandy soil, which absorbs the water and frequently parallel each other, thus ad- ding to the absorption losses by unnecessarily increasing the wetted perimeter. Where sandy soil is encountered or depres- 302 DISTRIBUTARIES sions are to be crossed the channels should be puddled or cement- lined, or flumes introduced. 251. Dimensions of Laterals. Experiments made in India show that the greater the amount of water discharged by a dis- tributary the smaller will be the proportion of cost of maintenance. Thus a channel 12 feet wide discharges more than double the volume discharged by two channels each 6 feet wide, while the cost of patrolling and repairing the banks would be half that of both the smaller ones. Experience has proved that irrigation can be most profitably carried on from channels 18 feet wide at the bottom and carrying about 4 feet in depth of water. Thus on the eastern Jumna canals during the years 1858 to 1860, inclusive, the expenditure of water on all the distributaries of 12 feet bed width and upwards was 0.123 f tne revenue, while on all those below 12 feet it was 0.223 or nearly double that of the first. From the same examinations the relative value per cubic foot per annum on channels of respectively 12, 6, and 3 feet in bed width was as 10:7:4. The increased action of absorption in small channels with diminished volumes and velocities accounts for the difference. The depth of water should accordingly seldom be less than 4 feet and the surface of the water should be kept at from i to 3 feet above that of the surrounding country; not only to afford gravity irrigation, but because the loss by absorption is thereby diminished. The principle which is so commonly employed in the West on private channels of diverting the water by raising it to the surface of the country by means of earth check-dams, or by in- troducing plank stops, is to be condemned. It converts freely flowing streams into stagnant pools, encourages the growth of weeds and the deposit of silt, and produces a generally unhealthy condition. It is moreover extremely wasteful of water, much of which is dissipated because of loss of head and because of absorp- tion and evaporation. Where these stop planks or checks are used in private channels with a view to diverting the water to the irrigable fields, little damage is done, since the planks remain in but a short time. 252. Capacities of Laterals. In planning a distributary DISTRIBUTARY CHANNELS IN EARTH 303 system care should be taken so to design each of the laterals that its carrying capacity shall be equal to the duty which it has to perform. This duty is dependent on various factors, which are fully discussed in Chapter V. The total area to be commanded by each branch and its laterals should be known, the duty of water for the particular soil and crops estimated, and then careful allowance made for the area of waste land (Art. 66), being that which will remain uncultivated or will be occupied by roads, buildings, etc. Consideration having been given to all these factors, the capacities required of the different channels can then be readily determined and their dimensions fixed. The simple form of computation which this investigation takes is A' = gross area commanded by the distributary; a = area of waste land ; 6 = proportion of culturable land which is to be irrigated during an average year. Then A=(A'-a)xb, ...... (i) in which A is the net area to be irrigated, and is equivalent to the same symbol in the formula in Article 58, so that the dis- charge of the distributary, Q 1 becomes Where rotation periods are to be imposed on a canal (Art. 67), careful attention must be paid to these and to their effect on the necessary discharging capacities of the laterals, and the latter must therefore be designed in accordance with the effect which these rotation periods or tatils will have on their required maximum discharges. 253. Distributary Channels in Earth. The cross-section of the larger laterals should be relatively the same as for main canals (Arts. 151 to 152). In designing the canal banks their top width should be sufficient to admit of easy inspection. On moderate-sized laterals 3 feet may be taken as the minimum width. Should the cut be so deep that a berm is necessary, it is always well to let the latter slope away from the canal and be 34 DISTRIBUTARIES drained off through the bank. The top of the bank likewise should not be level, but should drain away from the canal. For smaller laterals or private channels a trapezoidal cross-section both for the bank and the canal will usually be sufficient, and as far as possible the larger portion of this cross-section should be in embankment, thus keeping the water above the level of the FIG. 116. View of Lateral Head, Galloway Canal, Cal. surrounding country. In small channels it is not necessary to con- struct berms, to give subgrades or other complex cross-sections. 254. Wooden Lateral Heads and Turnouts. Heads to laterals on Western canals are arranged much as are the heads of main canals and wasteways. They consist essentially of two parts, a regulator or check below the head on the main canal, to divert the water into the lateral, and a regulating gate in the latter to admit the proper amount of water. These heads usually consist of a WOODEN LATERAL HEADS AND TURNOUTS 305 wooden fluming, which is practically an apron to the bed of the lateral, and planking to protect the banks. In this fluming are inserted the gates, which consist either of flashboards, as in Kern Variable Ffwtpliink " DETAIL OF MEASURING WEIR m En 5ft "ilraxuring Weir PLAN i; l i d : . : i r; . J T r -] 1 ' 2 'x 12 ' '12- II 2.12 /. . Note: All opening* / over ' Stringers _. u I : r ~~t wide to have two gate* ELEVATION FIG. 117. Wooden Head to Lateral, Sun River Canal, Montana. County, California, or of simple wooden lifting gates, as in most other portions of the West. In Fig. 116 is shown a distributary head on the line of the Calloway canal in California. Immediately below the regulator is shown a minor headgate or turnout leading to a private channel, 20 \v-*\ \ X S2 J, ^7 ^: z.^/s_ "J^/ r::: .- .__J E --.-9,9- 4 WOODEN LATERAL HEADS AND TURNOUTS 307 3 o8 DISTRIBUTARIES while a sort of well is formed in the lateral flume just below this farm headgate to retard the velocity of the current. The standard type of wooden turnout adopted on the smaller 12'2- >K 4'0- ^O^ 1 -' 9'9"--- -*J 4403.0 Bars from both side and wing walla continuous orners.Alternate bars from both Bets in face of fillet FIG. 119. Reinforced Concrete Turnout with lo-Foot Drop, Garland Canal, Wyoming. laterals of the Reclamation Service is illustrated in Fig. 117. This consists of a timber flume and wing- walls, with cross flume taken from its center in which the lateral turnout heads. Simple WOODEN LATERAL HEADS AND TURNOUTS 309 lifting gates, one or more in number, serve to check the flow in the principal lateral and turn the water into the branch which is ( \ Cant Iron / 1 / / './ ....... .., f f r 1 i i .X 5 _ ' v % ( ji * I: 1 j 1 F c u / t - 9 4- -nr- r- ^ IX SECT,ON-6 SECTION L " d FIG. 120. Cast -Iron Gates for Laterals, Interstate Canal, Nebraska-Wyoming. controlled by a similar gate. In the latter is a trapezoidal weir for measuring the amount of water admitted at various heads. 310 DISTRIBUTARIES For each Gate: 1 eye bolt, 10 "x ^'with 3"int. dia. ring as shown ^^ The bed of the branch lateral is taken off at a height of one or two feet above that of the principal lateral. 255. Masonry Lateral Heads. In Europe and India masonry is employed almost exclusively in the construction of distributary heads. These are generally so built that the water passing from them can be measured and the volume turned into the private channels be thus ascertained at any time. In PL XX is shown the type of distributary head used on the canals of the Punjab. On the Mutha canals in Bombay a V-shaped weir is placed in the head of each private channel or lateral for the purpose of water measurement, while a water- cushion is built in the lower portion of the distributary head in order to diminish the shock of the falling water. The rules for the dimensions of \vater- cushions are given for main canals (Art. 177). On the laterals of the Recla- mation Service turnouts of rein- forced concrete or of terra-cotta pipe are extensively used. The standard turnouts on the Yellowstone canal (Fig. 118) consist of rectangular reinforced concrete pipes, in pairs for the larger laterals, or of terra-cotta for pipes less than 24 inches cross-section passed through the canal banks. At entrance and exit are wing- walls of reinforced concrete 9 inches thick with cut-off wall of same dimensions carried down 4 feet below the bed of the pipe. Re- taining walls of same material support the canal banks. The walls of the pipes are of 9 to 7 inches thickness and are encircled by an 1 8-inch cut-off collar under the center of the canal bank. Falls are frequently concentrated at the lateral turnouts and 9i i 5 St.B. .PlO 7 holes ^ dia. prorld fc" Washer X 1 \* for MliUn S ( \ N - / .',, (Same for all gates) \ i \ / "* /1 ^3"^ / x a^ts" ~ St.B. 4 .H * i ^H ** 3 FIG. 121. Wooden Gates for Laterals, Interstate Canal, Nebraska-Wyo- ming. MASONRY LATERAL HEADS 311 the standard type of turnout with fall adopted on the Garland canal, Wyo., of the Reclamation Sen-ice is illustrated in Fig. 119. The main canal and lateral are paved and the banks protected with wing-walls of reinforced concrete. Above the fall crest are stop gates, of wood or iron (Figs. 120 and 121). The lateral heads just above these, and is taken off from the upper level at the end of a forebay about 25 feet deep. At the head of the lateral are control gates set in grooves in the concrete. All the gates slide vertically and are lifted by a screw which extends up through the female screw of a hand wheel. 256. Works of Reference. Diversion and Canal Works. AMERICAN SOCIETY OF IRRIGATION ENGINEERS, ANNUAL OF THE. Denver, Colo- rado, 1893. BARROIS, J. Irrigation in Egypt. Paris, 1887. Translated by Major A. S. Miller, U. S. A. War Department, Washington, D. C. BUCKLEY, ROBERT B. Keeping Irrigation Canals Clear of Silt. Proceedings Inst. C. E., vol. 58, Part IV. London, 1879. Movable Dams in Indian Weirs. Proceedings Inst. C. E., vol. 60, Part II. London, 1880. Irrigation Works in India and Egypt. E. & F. N. Spon, London, 1893. CAUTLEY, COL. SIR PROBY T. Ganges Canal Works. 3 vols. London, 1860. CHITTENDEN, LIEUT. H. M. American Types of Movable Dams and their De- velopment. Engineering News, vol. 33, No. 6. New York, 1895. DERRY, J. D. Victorian Royal Commission on Water Supply. Fourth Progress Report. Melbourne, 1885. ETCHEVERRY, B. A., and MEAD, ELWOOD. Lining of Ditches, etc. Bui. 188. Agricultural Experiment Station, Sacramento, Cal., 1907. FLYNN, P. J. Irrigation Canals and Other Irrigation Works. San Francisco, 1892. FORTIER, SAMUEL. Conveyance of Water. Water Supply. Paper No. 43. U. S. Geological Survey. Washington, D. C., 1902. HALL, WM. HAM. Report of the State Engineer to the Legislature of California, Part IV. Sacramento, 1881. - Irrigation in Southern California. Report of the State Engineer to the Legislature of California. Sacramento, 1888. - The Santa Anna Canal of the Bear Valley Irrigation Company. Trans. Am. Soc. C. E., vol. 33, No. 2. New York, 1895. HERSCHEL, CLEMENS. The Holyoke Dam. Trans. Am. Soc. C. E., vol. 15. New York, 1886. LEVINGE, H. C. Soane Canal. Professional Papers VII. Roorkee, India, 1870. MEDLEY, LIEUT.-COL. J. G. Manual of Irrigation Works. Thomason Civil Engineering College, Roorkee, India, 1873. MONCRIEFF, COLIN C. SCOTT. Irrigation in Southern Europe. E. & F. N. Spon. London, 1868. MULLIN, LIEUT. -GEN. J. Irrigation Manual. E. & F. N. Spon, New York and London, 1890. 312 DISTRIBUTARIES MURRAY, STUART. The Goulburn Weir and its Dependent System of Works. Victoria, Australia, 1893. NAVIGATION DE LA SEINE. Exposition Universelle Internationale. Paris, 1889. NEWBROUGH, W. Engineering Notes on Irrigation Canals. School of Mines Quarterly, vol. 15, No. 3. New York, 1894. RECLAMATION SERVICE, U. S. Annual Reports. Washington, D. C. RIGHT or WAY FOR CANALS, ETC. Regulations for General Land Office, Wash- ington, D. C., 1894. RONNA, A. Les Irrigations. Firmin-Didot et Cie. 2 vols. Paris, 1889. SCOTT, JOHN H. Irrigation and Water Supply. Crosby, Lockwood & Com- pany, London, 1883. STEWART, HENRY. Irrigation for the Farm, Garden, and Orchard. Orange^ Judd & Company, New York, 1889. SURVEYING INSTRUCTIONS, MANUAL or. General Land Office, Washington, D. C., 1894. VERNON-HARCOURT, T. F. Fixed and Movable Weirs. Proceedings Inst. C. E., vol. 60, Part II. London, 1880. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. WHITING, J. G. The Nira Canal. Proceedings Inst. C. E., vol. 77, p. 423. WILCOX, W. Egyptian Irrigation. E. & F. N. Spon, London, 1889. WILSON, H. M. Irrigation in India. Twelfth Annual Report U. S. Geological Survey, Part II. Washington, D. C., 1891. American Irrigation Engineering. Thirteenth Annual Report U. S. Geo- logical Survey, Part II. Washington, D. C., 1892. CHAPTER XIV APPLICATION OF WATER, AND PIPE IRRIGATION 257. Relation of Water to Plant-growth. The prevailing idea of irrigation has been the moistening of the soil by spreading water on its surface so as to produce by artificial means an effect similar to that caused by rain. This definition goes but a part of the way. It fails to take account of the effect of water on the physical properties of soil, and the physical and chemical pro- cesses which accompany plant-growth. More broadly, then, irrigation may be defined as the application of water to soil at such times, in such amounts, and so accompanied by cultivation of the soil as to produce the condition best suited to plant-growth. After light and heat, water is the most important of the various factors which influence plant-growth. Next to it in importance may be placed the physical condition of the soil, and lastly, plant-food. It is on these five factors, light, heat, water, soil-texture, and plant-food, that the machinery for plant- growth is dependent, and in about the order stated. When these are furnished in the right amounts and at the right times, the best results may be expected in plant-growth, and of these the latter three may be controlled to a material extent by the irrigator. In our arid regions heat and light are usually furnished in abund- ance during the irrigating season, and fortunately the clouds rarely furnish water at such times as it is not desired. There- fore, having at his disposal a satisfactory irrigation system, the quality and amount of the crops which may be produced depend chiefly on the knowledge of the farmer as to the proper mode of utilizing the water and soil. Plants do not naturally grow well in arid regions, because the amount of moisture evaporated from the surface of the leaves and stems by the domesticated grain and vegetable plants com- monly cultivated is much greater than the amount which their 313 314 APPLICATION OF WATER, AND PIPE IRRIGATION roots can absorb, and as a result the plant dries up. Nearly all of our cultivated plants have originated in humid climates, and as all plants evaporate, or, as it is technically known, "transpire," large amounts of water in the process of their growth, one of the first considerations in adapting our plants to Western needs is the desirability of modifying and developing them so as to encour- age the growth of those varieties best suited to the conditions. The physiological effect of irrigation is to furnish for absorption by the roots of plants sufficient moisture to balance the amount transpired by the leaves. In the humid region both air and soil are moist ; in the arid region both are warm and dry. The effect of this dryness of the air is to increase the transpiration, and by keeping up a greater tension in the plant to force or hasten its growth. It is for this reason that plants cultivated in the arid region by the aid of irrigation produce larger and more rapid growth than those of the humid regions much as is the case with hothouse plants. In order best to satisfy the conditions of plant- growth, the supply of moisture should never fail from the time the seed is placed in the soil until the crop is fully matured ; and there are certain times when the cessation of the supply will do more harm than at others for instance, in the case of corn, when grain is forming in the ear. Irrigation does away with the element of chance by supplementing moisture, by making the crop larger and more certain, and by reducing the number of acres which the farmer may cultivate. For easier understanding of the subject of plant-growth, it may be stated that moisture absorbed by the suckers or hairs of the rootlets rises to the green parts, especially the leaves, where it assimilates carbon from the air and becomes concentrated by its evaporation or transpiration. What remains descends and is distributed through the plant, where the carbon increases the growth of its various organs by adding to the cellular struc- ture of the plant. Transpiration takes place chiefly during the heat of the day, and is greater when the air is dryer and the soil more moist. The amount of this transpiration is enormous at times. An ordinary crop of meadow grass, cutting two tons to an acre, will RELATION OF SOIL TEXTURE TO PLANT-GROWTH 315 transpire 6J tons of water on a dry day and about 527 tons of water during a growing season; an average crop of wheat will evaporate 260 tons of water per acre in a growing season. There- fore hay evaporates an amount of water equal to 5^ inches in depth of the water, and wheat an amount equal to about 2f inches in depth of water in an irrigating season. The soil must therefore be maintained in a condition to supply this incessant consumption of moisture, and as soon as the moisture becomes deficient, the current or flow of sap becomes slackened and the plant remains stationary or dies. One hundred pounds of meadow grass contains on an average 70 pounds of water, and 100 pounds of red clover over 80 pounds of water, to every 100 pounds of fresh material. Such moist plants as lettuce, cucum- ber, cabbage, etc., contain as much as 95 to 98 pounds of water to even' 100 pounds of fresh material. These facts indicate the importance of water in plant-growth and the amount which must be supplied them, especially when it is recalled that much of the moisture reaching the soil evaporates from its surface or percolates through it. Experiments by Prof. F. H. King show that in Wisconsin from 250 to 450 pounds of water are required to produce a pound of dry matter. The depth of water required to produce a pound of dry matter in various crops ranged from 1 6 to 23 inches. All plants obtain their water solely through their roots, there- fore a well-developed root system is of the highest importance to their welfare. Consequently any process which will aid this development, such as the mode of application of water or attract- ing the roots in various directions by fertilization or tillage, should be carefully considered. Saturated soil is detrimental to their growth, while half -saturated soil is most favorable to their growth, and therefore to that of the plant. 258. Relation of Soil Texture to Plant-growth. Among the more important methods employed for conserving the mois- ture which reaches the soil from natural or artificial sources, and of making it available to the plant through its roots, are, i, cultivation and fertilization of the soil so as to enable it to absorb the moisture which reaches it; 2, decreasing evaporation from 31 6 APPLICATION OF WATER, AND PIPE IRRIGATION the soil surface, through producing a proper tilth or mulching ; and 3, decreasing the evaporation from the plants, Evaporation is essential to pi ant -growth, yet excessive evaporation is wasteful of moisture. Under certain conditions where it is desirable to reduce evaporation, which is less rapid in moist air than in dry air and in a calm than in strong winds, we may increase the amount of moisture in the air and thus diminish the evapo- ration from the plant by sheltering them by growths of trees suitably disposed, especially in regions in which hot, dry winds are prevalent. It is wasteful to allow water to flow off soils on which large sums have been expended in the introduction of irrigating systems. Every drop of water which flows from the soil is an indication that the latter is not in a proper physical condition. Either the surface slope should be changed by grading and terracing, or the soil be made more open and porous by proper preparation and cultivation. Also, wherever this cultivation has been prop- erly performed water is more rapidly carried into the soil, and this not only diminishes the loss by flow-off, but also by evapora- tion from the surface. Where moderate deep ploughing will not accomplish the object desired, subsoiling must be resorted to. There is much wisdom in the practice in vogue among many of the older and more wasteful irrigators who flood their land in the fall after their crops have been harvested. The common assumption is that this adds so much moisture to the soil that it is retained until the following spring, when the plants require it. The real explanation of the benefits of fall irrigation is that the soil which is helped by this process is not in the proper physi- cal condition. Nothing rectifies an unfit physical condition better than water. Therefore subsoiling or deep ploughing, whereby the soil is stirred up for a depth of 12 to 1 8 inches, breaks up its texture, and if water is properly applied thereafter beneficial effects will surely be felt by the succeeding crop. Such subsoil- ing should rarely be performed in the spring, and just before planting, as it works an injury to the first crop, though a benefit to the succeeding crops. It should therefore be done at a con- siderable time before the crop is put into the ground. After the RELATION OF SOIL TEXTURE TO PLANT-GROWTH 317 ground has once been deeply subsoiled it should be frequently stirred up so as to maintain a mulch of loose, dry soil on the sur- face, and thus check evaporation and aid in the absorption of moisture. This after-cultivation should rarely be to a depth exceeding 3 to 5 inches. There are many curious facts connected with the effect of water, cultivation, and fertilization on plant-growth. It is well known, however, that climatic conditions, changing seasons, which chiefly include light, heat, and moisture, have more effect upon the production of crops than is obtained through any degree or kind of fertilization. It is not rare to have a crop over a wide area fall off one-third or even one-half by reason of unfavorable climatic conditions, even though fertilizers may be applied most liberally. Again, soil may be analyzed and be found wanting in certain chemical requisites for plant-growth. These chemicals may be supplied by fertilizers and yet produce little beneficial effect on plants, while some other fertilizer or some other methods of cultivation may increase the crop a hundredfold, in some way which is unexplained by chemical analysis. This is undoubtedly due to the physical effects of water brought more intimately in contact with the soil in changing its texture, or to physical effects of fertilizers on soil rather than on its chemical constituents. This is probably by changing the relation of soil to moisture and heat so as to better adapt it to the needs of the particular plant. Thus, a worn-out soil is not necessarily deficient in plant-food, and soils which are barren in that they will produce little plant -growth have been shown by chemical analysis to contain an abundant supply of food material. The texture of soil is largely determined by the amount of clay and the manner in which the clay particles are arranged in the soil. Early vegetable and fruit soils have from 4% to 10% clay, but are too light for wheat. The best tobacco lands have from 15 % to 20% clay, while the subsoil in good wheat and grass land has from 20% to 50% clay. Fertilizers and water and the temperature at which the latter is applied have great effect on the texture of clayey soils by changing the arrangement of the soil grains. Thus the subsoil of a good grass land from decom- 318 APPLICATION OF WATER, AND PIPE IRRIGATION posed limestone has 40 % to 50 % clay, yet impervious pipe-clays on which nothing can grow owing to their physical texture have been analyzed and found to have the same percentage of clay. This is because the grains are evenly arranged and the spaces between them through which water moves have so uniform a size that water can scarcely circulate. On the other hand, in the limestone soil having the same proportion of clay the grains are differently arranged or are granulated and held close against the grains of sand, thus leaving large spaces in the soil through which water and air can move readily. Experiments have been made which show that a few drops of ammonia will make a very coarse, sandy soil almose impervious to water, as will also car- bonate of soda or black alkali (Art. 44). Lime and organic matter may do the same, yet the effect of lime is commonly to render heavy soils looser and more friable. One of the most potent influences on the physical texture of soil and its relations to plant-growth is the amount of air-space in the soil and the relation of this to the amount of moisture contained therein. When water in soil amounts to over 80 % of its water-holding capacity it is detrimental to plant-growth. This is because its roots are immersed in water and the soil is poor in oxygen or air. On the other hand, when only a part of the space in the soil is filled with water and the air-supply is sufficient ordi- nary plants do best; that is, when the water in the soil amounts to from 40% to 60% of its water-holding capacity, or in other words, when the spaces in the soil contain half air and half water. The water-holding capacity of a soil depends on the amount of space between the soil grains, and averages 40% to 60% of the total soil volume, therefore the amount of water in soil should average about 25 % of the total soil volume, and there should be about the same percentage of air-space, dependent upon the character of the soil and the crop to be grown. Thus the amount of water in soil most favorable to wheat growth is 12 to 20 pounds in every 100 pounds of weight. At the other extreme, the water- holding capacity of heavy clay soils is about 44 pounds per 100 pounds of saturated soil. The plant may wilt in a soil contain- ing 10 % to 12 % of moisture, because this amount may be so small THEORY OF CULTIVATION BY IRRIGATION 319 as to make water movement to the roots too slow. In a soil of different texture, the same plant may not suffer when the amount of moisture in the soil is as low as even 6%. 259. Theory of Cultivation by Irrigation. From what has preceded it is evident that the correct mode of applying water to soil in irrigating various crops is yet but a matter of merest experiment. It is* dependent on many varying fac- tors, among which are the physical and chemical properties of the soil; the temperature of both air and water; and the condition of the crop growth, that is, the time when it requires irrigation. As has been shown, the irrigator must strive to accomplish three results in the most perfect manner: i, he should not apply cither too much or too little water, but just sufficient to fill about half the soil spaces; 2, this water should be applied in such manner as to be most evenly distributed throughout the soil in order to encourage root-growth in all directions; 3, the soil should be so cultivated as to create the loosest texture, and thus enable it to hold the largest proportion both of air and water without settling and becoming heavy or soggy. The physical texture of the soil is beneficially affected by deep subsoiling or plough- ing, followed by rain or irrigation, at a considerable period of time before the planting of crops preferably in late fall, when water is abundant. After seeding the soil should not again be deeply ploughed, and should be frequently stirred for a few inches in depth to produce a surface mulch, especially prior to irrigation, that the water may be absorbed and not evaporate too freely. The first cultivation after seeding cannot take place until after the plant has attained sufficient growth to render it possible to avoid injuring it. Certain crops, as meadow-grass and hay, cannot be so cultivated without injury to them. Others which are planted in rows, as potatoes and corn, and orchards and vineyards, offer excellent opportunities for such after cultivation. A well-cared-for orchard or vineyard should never show a sign of weed or other plant-growth at any period in the year. Water cannot be applied after seeding to hay, grain, and similar crops, until they have attained such a height above the ground that 320 APPLICATION OF WATER, AND PIPE IRRIGATION the cracking of the drying soil at the surface will not seriously injure the crown growth and delicate stalks. This brings us to the theory of time of application and amount of water, which again can only be determined by experiment and yet is dependent upon certain general principles. Experi- ments made at the Agricultural Experiment Station of Utah with early and late watering of hay and grain crops indicate for the latter that early and late watering produces decidedly larger crops of grain and but little less of straw. In the climate of Utah early irrigation means watering in the middle of May instead of toward the middle of June, as is customary, and late irrigation means watering but a week before harvest time. The effect of usual irrigation instead of beginning early in the season and ending late in the season seems to be that the early irrigation affects soil temperature as well as its physical properties. Grain plants absorb a large amount of moisture during the time when they are taking on stem and leaf. There is but little moisture relatively in the grain, and this is formed rapidly and during a short period of time. The application of water shortly before harvesting forces the grain, makes it ripen rapidly, and produces a greater ratio of grain to straw, and a larger yield of the former as well as of the whole plant. On the other hand, the influence of early and late watering on potatoes has the opposite effect. In the experiments referred to this crop suffered materially from the effects of early watering, due, it is believed, to watering before the plant demanded it, thus reducing the temperature of the soil and of the air around it in such a manner as practically to delay the season. In comparisons of night and day irrigation it tran- spired that the temperature of soil irrigated at night was higher than that irrigated in the day. It is well known that irrigation lowers the temperature of the soil and therefore retards plant- growth for the time being, so that there appears to be an advan- tage in this point for night irrigation; yet for grain crops the yield of the grain is greater for day than for night irrigation, due, probably, to checking of growth of foliage. On the other hand, the yield of straw is greater as a result of night irrigation. The method of applying water is also indicated to some METHODS OF APPLYING WATER 32! extent by the foregoing considerations. Where water is applied to plants -by flooding, especially where evaporation is great and the amount applied relatively small, it results in a shallow growth by attracting the roots near the surface. If water is applied from small orifices of subsurface pipes it encourages the root- growth in that direction only, and prevents their spreading in other directions. Irrigation by deep furrows at some distance apart one from the other tends to draw root-growth toward the furrows, though in certain plants, as potatoes, corn, celery, and others which are naturally grown in ridged rows, this form of irrigation is best suited to root development. For many other varieties of plants, and especially for fruit-trees and vines, the method of application which is probably best suited to root devel- opment is by means of many small but deep furrows carrying small volumes of water which shall completely enter and uni- formly saturate the soil in all directions. As to time and amount of water, each soil, crop, and climate is a law unto itself, and experience, tempered by a knowledge of the physical and chemical effects of moisture and the texture of soil on plant-growth, must indicate to the irrigator the course best suitable for his particular conditions. In Chapter V this sub- ject has been treated in a general manner, and additional facts are pointed out in the following articles. Each condition calls for a particular depth of watering and a particular time for applying water which, if properly fulfilled, will produce superior results. 260. Methods of Applying Water. The cultivator applies water to crops by various methods, depending chiefly on the nature of the crop and the slope of the surface of the ground. These are: 1. By absorption from water sprinkled over the surface. 2. By filtration of a sheet of water downward through the surface of the soil. 3. By lateral percolation from an adjacent source of supply. 4. By absorption from a subsurface supply. The first method includes irrigation by nature in the form of rain, or by sprinkling with a watering-pot or hose. This method 21 322 APPLICATION OF WATER, AND PIPE IRRIGATION is of such simple character as to require no further consideration here. The second method of irrigation is called flooding, and is accomplished in three ways, depending on the character of the crop and on the slope of the soil : 1. Flooding of meadows by simply conducting a ditch along the upper slope of the land and allowing the water to flow from this completely over the meadow. 2. Flooding by checks, by dividing gently sloping surfaces into level benches by means of check levees and permitting the water to stand in these as in still ponds. 3. Flooding by the checkerboard system, by dividing nearly level ground into rectangles by surrounding levees and allowing the water to stand in these. The third method of application is generally called the furrow method and is accomplished in four ways: 1. By running small ditches close to fruit-trees and vines, and allowing the percolation from these to moisten their roots. 2. By letting a large number of small streams flow from flumes through ditches between fruit-trees and vines, and allow- ing the water to percolate from these to their roots. 3. By flowing the water in small streams through the furrows between such crops as potatoes and corn, and thus gradually moistening them. 4. By drilling grain in rows or shallow furrows and running the water through these. This is practically a combination of flooding and sidewise soakage. The fourth method of irrigation is conducted by laying pipes underground and having outlets in these under each fruit-tree; or by so placing these outlets that the water escaping therefrom shall moisten the roots of vines and trees near by. 261. Preparation of Ground for Irrigation. The amount and kind of preparation required to put ground in the most suitable condition for irrigation is indicated in the above general discussion. In every case where the best results are desired the greatest care should be taken in properly grading and laying out the irrigable lands. A little time and money devoted in PREPARATION OF GROUND FOR IRRIGATION 323 the beginning to a proper preparation of the land will be more than repaid in the saving of water and the ease and cheapness with which it can be applied. Land once properly prepared can always be cheaply and easily maintained in the best condi- tion. The real secret of successful irrigation is intensive culti- vation, by which is meant careful and tireless attention to a very small area of land by one individual. A single farmer can produce larger and better crops and obtain greater profit from thorough and careful cultivation of 10 to 20 acres than from superficial cultivation of 100 acres. Where land is properly prepared one man can quickly and thoroughly handle water on ten acres, whereas two or three men would not produce as satisfactory results on the same area illy graded and prepared. Where water is to be applied by the flooding method great care should be taken to produce a perfectly uniform slope and surface. This should be done by the use of some of the grading tools which are now on the market, in connection with levels taken to determine within an inch or two as maximum limits the slope of the land. If the surface is particularly uniform, deep ploughing followed by harrowing and then dragging over the surface a heavy log or beam or some other device for leveling the land will suffice. At other times the slope may be too great to permit of irrigation by flooding, because it would produce such a velocity as to cause erosion of the soil. This is to be corrected by grading the soil so as to form checks or in extreme cases by terracing, which is but an exaggerated form of check. If the surface is uneven the water will stand about in pools, so that certain portions of the land will receive too much and become supersaturated while other places will be high and dry. It is only, therefore, by the creation of a uniform surface that water can be satisfactorily applied by the flooding method. Where the soil is to be prepared for irrigation by furrows, and especially where these furrows are to be small and narrow, as in the drill method of irrigation, even greater care must be taken than in the flooding method in producing the proper slope and surface level. If the slope of the land is too steep the furrows and drills will, because of the velocity of the water, be rapidly 324 APPLICATION OF WATER, AND PIPE IRRIGATION eroded. If the slope is too slight the water may take so long in flowing across the fields as to be all evaporated or absorbed before it reaches the further end. Too steep slopes may be rectified by running small ditches or flumes down the slope of the ground and inserting falls in them to overcome excess of slope, and by turning the water from these into lateral furrows and drills which run at such an angle as procures the proper fall. 262. Sidehill Flooding of Meadows. This method is the FIG. 122. Diagram Illustrating Flooding of Meadows. most wasteful of water, but it is that most commonly practised in the cultivation of grass and cereals. Wild meadow-lands and hayfields are flooded by simply turning the water on them when the slope of the ground is sufficient and allowing it to sink into the soil. To accomplish this the water is made to enter the field at its highest point in a ditch conducted around an upper contour of the field. Breaks are made at intervals in the side of the ditch, and the water, being allowed to flow through these, finds its way in a thin sheet over the field (Fig. 122). This method FLOODING BY CHECKS 325 is very expensive of water and can be employed on but few soils since clayey soils bake or parch, forming a thin crust which kills the growth of plants. Instead of making breaks in the side of the ditches, checks are sometimes formed by little dams of earth or wood. 263. Flooding by Checks. This method consists in run- ning check levees around the slope of the land on contour lines. These are low ridges of earth about i foot in height, turned up with a plough or scraper and placed at such distances apart that the crest of each shall be on a level with the base of the check above it (Fig. 123). If properly built these checks will SCCnon on a-* FIG. 123. Irrigation by System of Check Levees. last for many years, and the field may be ploughed and reploughed without injury to them or their in any way affecting the handling of the crops. In comparatively level country like that in Kern county, California, the distributary ditches are placed as much LS a quarter of a mile apart, their banks forming two of the bound- ing ridges or levees, the third or lower boundary being a contour levee connecting the ditch banks. The less the height of this levee the better, because the quantity of water spread over the land will be of more uniform depth and will interfere less with 326 APPLICATION OF WATER, AND PIPE IRRIGATION PLAN ploughing and harvesting; the greater the width of the levee base the better. From 6 to 12 inches is the best height, and from 15 to 20 feet the best width of base. In such country as that described the checks range from 10 to 50 acres each in area and require from 12 to 20 miles of levee per square mile of check, while a mile of levee contains about 3000 cubic yards of earth. The water is run through the ditches (Fig. 123) and ad- mitted by gates into each separate check. When the latter is full the water is drawn off to the next lower level, or if the soil is porous it is al- lowed to stand until it has been absorbed. 264. Flooding by Check- erboard System of Squares. This method is practised ex- tensively on the level plains of Southern Arizona and in In- dia. The fields are divided into squares of from 20 to 60 feet on each side (Fig. 124), and these are separated by ridges or levees of from 10 to 12 inches in height in which openings are made leading FIG. 124. Flooding by System of Squares. from one square to the other. In some cases the fields are divided into much larger squares, often of an acre in extent, depending on the slope of the ground. Again, especially in India, very small squares are employed, and the height of the dividing ridges is made as low as 6 inches, so that these do not interfere materially with the harvesting and ploughing of the fields. The chief objection to this method is the obstruc- tion created by the check levees. When these can be placed far enough apart they interfere but little with the operations of . FLOODING BY TERRACES 327 the cultivator: otherwise he must use spade and hoe instead of plough. Water is admitted to one square at a time and is either per- mitted to soak into the soil or is drawn off to be used in the next square below, much as in the check method. The chief crops irrigated by this method are hay, grain, and vegetables. Where flooding is practised by checks or squares, anywhere from 4 to 12 inches in depth of water is let on at a single watering. The number of these waterings may range between two and five in a season, according to the crop, soil, and climate. Rice and sugar-cane are irrigated in India and South America by squares. These crops require a very large amount of water, and as a con- sequence the height of the levees is rarely less than a foot and is often greater. These are filled with water and it is allowed to stand on them for long periods of time, the soil being seldom permitted to dry. 265. Flooding by Terraces. This method is employed chiefly in India and China, and has recently been adopted on a small scale in a few neighborhoods in California. It consists of laying out steeply sloping sidehill ground in terraces, the lower sides of which are surrounded by high levees. These are practi- cally exaggerated forms of checks, and as employed in California are maintained and operated on the same general principle, though thoy receive a large proportion of their water-supply from the drainage of the hillsides above. As employed in India or China, these terraces also receive their water-supply chiefly from the drainage above, and hold it as in a small tank or reser- voir of a few feet in depth. As the water soaks into the soil of the terrace, rice or similar crops are sown, and the amount of moisture retained in the earth by such a volume of water entering )t is sufficient, with the addition of what may be received from occasional rains, to irrigate the crops. 266. Furrow Irrigation of Vegetables and Grain. This method is practised by laying the field off in shallow ditches run around its upper slope. From these ordinary V-shaped plough furrows radiate down the slope of the field, and between these vegetables, potatoes, or grain are planted. Where the 328 APPLICATION OF WATER, AND PIPE IRRIGATION country slopes more irregularly or steeply the furrows are run at various angles down the slope in such manner that their grade shall not be too steep. The water is then turned into a few of these furrows at a time by blocking the ditch above with a clod of dirt or a board (Art. 266), and the water penetrates by side- wise soakage to the crops. Grain is irrigated by the furrow method by ploughing a ditch along the upper slope of the field as above described, and by drilling the grain down the slope of the field radially from this ditch and permitting the water to enter a few of the drill-rows at a time. Grain-fields are some- FIG. 125. Furrow Irrigation of Grain. times prepared for this method of combined flooding and fur- row irrigation by rolling the field after the grain is planted, with a heavy roller on the surface of which are annular projections of a few inches in height and from \ to i foot apart. These make grooves in the surface of the soil in a direction parallel to the slope, and the water is admitted to these and permitted to flow through them as in the case of ploughed furrows or drill- rows. 267. Combined Flooding and Furrow Irrigation of Orchards. Where trees are directly flooded the tendency of the water is to bring the roots to the surface and thus enfeeble them. To prevent this furrows are run from the upper ditches, generally in a double row, one on either side of and at a short distance 330 APPLICATION OF WATER, AND PIPE IRRIGATION from the trees or vines (Fig. 125). By this means the water per- colates into the soil and reaches the roots of the tree by sidewise soakage at some depth beneath the surface, thus moistening and encouraging their growth. Another method of flooding orchards is to protect the trees by earth ridges thrown up so as to prevent the water from reaching within 3 to 4 feet of them. In this method the entire field is flooded with the exception only of the areas immediately adjacent to the trees. This practice is wasteful of water, as much more is employed than is required. Olive- and orange-trees are watered from three to four times in FIG. 126. Furrow Irrigation of Orchard, Riverside, Cal. a season ; vines once or twice, and often not at all after the first few seasons. 268. Irrigating Orchards by Small Furrows. This method is practised chiefly in Southern California. The principle under- lying this method is that the ground shall be put in the condition which it would be in after several days of long soaking rain, rather than in the condition which it would be in after a small cloud- IRRIGATING ORCHARD BY SMALL FURROWS 331 burst, which is the condition resulting from other methods of sur- face irrigation. This is done not by running large streams of water through the furrows for a short period of time, but by run- ning small streams through them for a long time. It is accom- plished (Fig. 126) by running a number of ploughed furrows between the rows of trees, the nearest furrow being as close as practicable to the trees, and the distance between furrows from 2 to 3 feet. The volume of each of the streams running through these does not exceed one four-hundredth of a second-foot, and the water is run through them for two and three days at a time. Where the soil is not too loose or sandy this method seems to give the best results for fruits and vines and may be used with some success on grain and corn. The moistening of the roots by sidewise percolation from shallow furrows between tree rows is not nearly so complete as generally supposed. This is admirably indicated by a series of experiments conducted by R. H. Loughridge in California in 1908. As shown in figure 127 the movement of water in porous loam soils is downward; it percolates laterally only 2 or 3 feet from the furrow and fails entirely to reach through the tree rows or under the trees unless the furrows are very close to them (Fig. i2yA). An impervious layer like hardpan causes sidewise movement to the extent of 4 to 5 feet, greater wetting of the surf ace, and increased loss by evaporation (Fig. 1276). In grit the movement is more rapid downward (Fig. 1270). In loose soil an extreme depth of 26 feet was reached; in compact, impervious soil the depth was but 12 inches after three days. Shallow furrows do not give as good results as deep ones, as they allow the water to rise on either side by capillarity and evaporate, while deep furrows allow the retention of nearly all the water applied. In order that the method shall be successful, the laterals from which the furrows are filled and which come from the main distributary must have a uniform depth and slope to a degree which cannot be secured in open earth. This is accomplished by running wooden laterals or flumes along the surface of the ground down its slope. These simple flumes are but a few inches 332 APPLICATION OF WATER, AND PIPE IRRIGATION in cross-sectional area, generally the width of a plank at base and on the sides. They are given a sufficient grade to produce a good velocity, and where the natural slope is too great falls Ft, 1 2 3 4 5 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 10 11 12 13 14 15 16 17 18 19 20 FIG. 127. Extent of Percolation from Small Furrows; A, in Loose Loam; B, in Hardpan; C, in Impervious Grit. are introduced. The water escapes from these flumes into the furrows through auger-holes bored in their sides opposite each furrow and on a level with the bottom of the flume (Fig. 126). DITCH AND FURROW CHECKS 333 The flow through these holes is regulated by wooden buttons or plugs which are inserted in them. For small orchards these flumes generally have a capacity of about a second-foot. Fruit trees thrive well on from three to five waterings and vines on from two to three waterings when supplied by this method. 269. Ditch and Furrow Checks. Water flowing in minor ditches must be checked and turned into the field channels and furrows by some temporary and inexpensive means. Likewise water flowing through the smaller furrows must be turned from FIG. 128. Using Canvas Dam. these into other furrows and drill-rows by some similar temporary expedient. The plan of erecting wooden structures at such points is not only expensive but inconvenient, as permanent structures interfere with the working of the fields. The form of check which works about as satisfactorily as any on the larger field ditches is the canvas dam (Fig. 128), which consists of a simple piece of scantling from 5 to 7 feet long, according to the width of the ditch, on which is nailed and held by a lath a piece of 10- or i2-ounce canvas from 50 to 60 inches wide, preferably large enough to afford ample protection to the sides of the ditch, 334 APPLICATION OF WATER, AND PIPE IRRIGATION and about 3 feet in length. At the bottom of this piece of canvas laths and a rope should be fastened for properly manipulating it. The scantling is laid across the ditch banks, and the canvas conforms to the inner surface of the ditch, and is held in place by a stake of wood driven through the rope loop at the bottom. This canvas dam obviates the necessity of injuring the sides of the ditch by temporary earth or wood dams. The older and more common mode of checking water in ditches or furrows is by throwing dirt into these from either bank until the flow of water is blocked. This method is still probably the most satisfactory for use in small furrows and drills which a spadeful of earth or a small stone will block. Another form of dam than that of canvas, and which is not FIG. 129. Steel Dams. unsatisfactory under certain conditions, is that of a thick piece of sheet metal, which may have a couple of handles at the top, and be fastened to a small wooden scantling. This piece of sheet iron, which should be curved or pointed at the bottom, can be forced vertically into the ground in a manner similar to that of driving a shovel into the bed of the ditch, and this will procure a satisfactory temporary check (Fig. 129). 270. Subsurface Irrigation. Irrigation from beneath the surface, or subirrigation, is theoretically one of the most eco- nomical and satisfactory methods of applying water to plants. The idea is to replace seepage from above by absorption from below, which, to be perfect, should not wet the surface. As SUBSURFACE IRRIGATION 335 a result the water thus applied to the soil should theoretically have the same temperature, and thus not set the plant-growth back, and as long as the water does not reach the surface it is presumable that just the right amount has been applied and not sufficient to saturate the soil. This is effected by laying pipes underground, and these derive their supply from distrib- utaries, which are usually of vitrified pipe. The cost of pre- paring land for this mode of irrigation is relatively great, but is more than repaid by the saving in water charges, since the duty of water reaches as high as 500 to 1000 acres per second - foot. This method has been most extensively employed among the valuable fruit-lands of Southern California, which are usually divided into orchard lots of from 10 to 20 acres each. The company distributing pipe terminates at the highest point in each of these lots, and from this the subirrigation pipes of the farmer are conducted through the orchards. In practice this method has not proven as satisfactory as had been anticipated. Roots clog the orifices of the subirriga- tion pipes, and uniform watering of the soil such as is required to produce the best form of root-growth is practically impossible. This is true even when roots do not clog the orifices, and, more- over, growth of these roots has also the effect of bursting and destroying the pipes. Yet in some localities where this method has been introduced and great care and attention have been paid to the maintenance of the subirrigation pipes very satis- factory results are still achieved. Subirrigation, while attractive theoretically, is considered a failure even in Southern California, where it has been most thoroughly tried and no expense spared to make it effective. This method does not work well in sandy or gravelly soils, because of the tendency of the water to drain off through these, and this may account for the disfavor into which this method has fallen in Southern California, where this class of soils predominates. This system works best in loamy and silty soils, where the effects of capillarity are greatest, and this fact may account for the favor which this system has met with in portions of Kansas. Experiments on subirrigation at the Utah Agricultural Station developed the fact that for the climate APPLICATION OK WATKK, AND PIPM IkKKiATION and soil subirrigation failed to supply sufficient moisture for growing crops, as the lateral movement of water due to capillarity was too slow to furnish the requisite moisture for transpiration. 271. Subirrigation Pipes. These are made of sheet iron or steel or of some porous or glazed material. Glazed earthen- ware pipes are more popular than any other form. Asphalt- concrete pipes have been successfully employed for subirrigation and have the advantage over simple concrete pipes of being impervious to water. These are united by heating so as to form a continuous pipe. These distributing pipes are in some cases as small as 2 inches in diameter, and from this they range to 6 inches where the principal distributaries are reached. Subirrigation pipes are laid in open trenches at a depth of i to i feet below the surface, parallel to the rows of trees or vines in the orchard, and the trench is then filled in with earth. Irriga- tion is effected from these pipes sometimes by cutting a hole on the upper side and inserting therein a wooden plug opposite each tree or vine. Each plug is surrounded by a larger stand pipe set loosely on top of the distributary pipe, open at the bottom and reaching to the surface of the ground for the purpose of keeping the dirt away from the outlet and rendering it accessible at all times for inspection. The process of irrigation consists in simply turning the water off or on from the main pipe, when it finds its way through the outlets, fills the standpipe, and slowly percolates to the surface of the ground. One of the most satisfactory methods of letting the water escape consists in cutting a section several inches in length out of the continuous pipe where the plug- hole should be inserted, and by replacing it by a U-shaped shoe placed below the cut in the pipe. A tile a little longer than the gap covers it and water escapes between the two surfaces. 272. Main and Distributing Pipes. It is frequently found desirable to use pipes on main canal lines as inverted siphons, or pressure pipes to carry water over depressions which would otherwise have to be crossed by flumes or similar structures. Since methods of building suitable pipes of wood have been introduced in the West this form of structure has come into more popular use because of its relative cheapness, and its dur- MAIN AND DISTRIBUTING PIPES 337 ability. More recently, particularly on the works of the Reclama- tion Service, concrete or reinforced concrete pipes have been employed, according to the pressures to be withstood. The pipes more generally used are of cast iron, sheet steel or iron, wood, cement, vitrified, concrete or reinforced concrete, according to the amount of pressure which they may have to withstand and the relative cost of the various materials in the locality in which they are to be used. The pipes in more general use range from 4 to 60 inches in diameter, or in extreme cases an- even larger, though it has usually been found desirable to use two pipes when the volumes to be carried call for excessive dimensions (Art. 246). Cast-iron pipe should be used only under great heads of pressure, exceeding say 200 feet. Sheet metal or reinforced concrete pipe has generally been employed for pressure between 50 and 200 feet, and for lower pressures down to 20 feet wooden pipes, and below this cement or vitrified pipes. Wooden pipes are now being used under certain con- ditions more cheaply and satisfactorily than reinforced concrete, sheet iron or cast iron for pressures as high as 200 feet. The controlling considerations governing the adoption of any par- ticular material must invariably be the cost of materials at the point at which the work is to be constructed, the expense of put- ting it together, the durability desired, and the duty to be per- formed. In general it may be stated that in most of the arid region cast iron is more expensive than the other forms of pipe, owing to its great weight and the consequent heavy freight charges, that wood is cheapest where it may be sawed near the seat of work, and that otherwise reinforced concrete or terra-cotta tile pipe, depending on pressures, will be cheapest in the long run because most durable. Experience gained in the West indicates that the life of a wooden pipe well constructed and properly tended is quite as long as that of well-constructed and asphaltum- coated sheet-metal pipes. It may be expected under favorable conditions to have a life of at least forty years, though the least carelessness in preventing oxidation may cause it to rust and become worthless in a few years. Reinforced concrete and 338 APPLICATION OF WATER, AND PIPE IRRIGATION vitrified tile pipes undoubtedly have by far the longest life and require the least attention and repairs. 273. Flow of Water in Pipes. The formulas for the flow of water in pipes are practically the same as those given in Chap. VI for the flow of water in open channels, modified by friction due to the pressure under which the pipe may be placed. "Water will seek its own level," and as a result of this well-known law water in a pipe which may be depressed to as great an amount as its resistance to pressure will stand will rise in the further arm of the pipe to the level of its source if it be allowed to stand quietly within the pipe without motion. The moment that motion or flow takes place it becomes necessary to overcome the resistance due to the friction of the water against the walls and bends of the pipe, and this balance of pressure must be obtained by shortening its lower or discharging arm in order that the source FIG. 130. Flow of Water in Pressure Pipes. may be at a greater height than the point of discharge by the head necessary to overcome the resistance due to friction. The velocity and discharge of a pipe are dependent not only on the head or pressure for a given diameter, but also upon the frictional resistance which the interior of the pipe offers to the flow of water. Accordingly the discharge for a given head may be increased for the same diameter of pipe by using a pipe with smoother lining with the straightest possible alignment and fewest obstructions to flow in the way of bends and joints. In conducting water through pipes from storage reservoirs account must always be taken of the reduction of pressure in the pipe due to the lowering or draining of the water from the reservoir, and such pipes should always be calculated on a basis of the pressure FORMULAS OF FLOW IN PIPES 339 due to the height of their inlets, and not to the height of water in the reservoir. Should the pipe rise at any point above the hydraulic grade- line (BE, Fig. 130), or should it have vertical bends of any con- siderable height, air will accumulate at the summit of these bends at A. This air is compressed from one side by the head /*, and on the other side by the head H; then if h = H and the surface of the water at D does not meet the outlet of the pipe E, there will be no discharge. Under less extreme cases the dis- charge will be greatly reduced, and it is therefore necessary, where there are such vertical bends in pipes, to insert ventilators, or air-valves as they are called, to release the air-pressure at such points. Likewise at the lowest point in a pipe crossing, say a ravine, at the point r, mud, dirt, and other obstructions are apt to accumulate, and it is necessary to insert there mud -valves or blow-offs for clearing the pipes of such obstructions. 274. Formulas of Flow in Pipes. If there were no resist- ance to the flow in pipes, due to friction or pressure, the veloc- ities of flow would be similar to those for falling bodies. Ex- perience has shown, however, that velocity of flow in pipes is equal to only two-thirds of the height, the remaining third being lost in overcoming the resistance to flow of water in entering the pipe; hence we have the formula .M ~^~T : in which g is the acceleration due to gravity or 32.2 feet, and h is the head or height of fall. One of the controlling factors in determining the flow of water through pipes under pressure is the hydraulic grade-line, which is a straight line drawn from the entry to the exit of the pipe (BE, Fig. 130). Water flowing through a pipe which has several vertical bends in it may rise nearly to the level of this hydraulic grade-line, though the pipe should never except under the most unfavorable circumstances rise in any portion of its length above this line, otherwise there will be 'a decided loss of pressure at this point and a diminished flow below it, calling 340 APPLICATION OF WATER, AND PIPE IRRIGATION for an increased diameter from that point on to carry the dis- charge required. Where the vertical bends in a pipe are kept well below the hydraulic grade-line or where the pipe is practically in the grade- line, in other words, when its alignment is straight, it will be under little or no pressure, and the formulas of flow of water in open channels are directly applicable to all computations necessary to determine the velocity and discharge in such pipes. These formulas are given in Chapter VI, and may therefore be used in computing the discharges and other factors required in designing pipes which are not under pressure. There are many formulas for the flow of water in pipes under pressure, notable among which are those of Weisbach, D'Arcy, Flynn, and others whom it will be unnecessary to mention here. Nor is it desirable in such a work to discuss the theory of such formulas. These subjects are fully treated in many accessible publications, among which are those of Weisbach, Fanning, Bovey, and Flynn. For the purposes of this work it is sufficient to give but a few of the simpler of such formulas, and the neces- sary tables to aid in their use. The most satisfactory modifica- tion of the more abstruse formulas are those published by Mr. P. F. Flynn in private pamphlets, in the Transactions of the Technical Society of the Pacific Coast and in his admirable treatise on ''Irrigation Canals and other Irrigation Works," and these, with abbreviated tables, are given in the following article. 275. Tables of Flow in Pipes With and Without Pressure. The Chezy modification of Kutter's formula given in Art. 78, ~, ........ (2) is really the most satisfactory which can be used to express flow in pipes without pressure. This formula is sufficient only for particular conditions of pipe surface, unless the value of C be made to include the coefficient of roughness and other modify- ing elements, according to Kutter's method. So considering it here, as was done in the case of flow in open channels, the tables given in Art. 77 then furnish the material from which to com- TABLES OF FLOW IN PIPES 341 pute nearly all of the elements of flow in pipes either clean or tuberculated. The D'Arcy formula for flow in clean pipes is * . 00000162 ^.00007726 + - - -- 1 The value of the coefficient in this formula depends on the hydraulic mean depth r, and is not affected by slope as is the case with Kutter's formula. D'Arcy's formula is based on careful experiments made with clean pipes and is therefore quite accurate for pipes of moderate diameter, but not for pipes of large diameter. Kutter's formula, on the other hand, is derived not only from experiments with small but also with very large channels; and as it takes into consideration the roughness of surface as well as the slope, it agrees more accurately with the actual discharge than does D'Arcy's for large pipes. Flynn has modified D'Arcy's formula (3) to the following simplified form: - ISI'x V* .... (4) He has also taken D'Arcy's formula for flow in old cast-iron pipes badly tuberculated, and from it has derived the simplified form * in which d equals the diameter of the pipe, and i is the sign of the slope or fall of water in any height h, divided by i, which i the horizontal projection of the hydraulic grade-line joining the two extremities of the pipe. It may be further stated that r, which is the hydraulic mean depth, is equal to one-fourth of the diameter in the case of circular pipes. These formulas may again be reduced to the more simplified Chezy form v = C\/~ri and Q = ACV~ri, .... (6) and the values of these factors have been tabulated by Mr. Flynn 342 APPLICATION OF WATER, AND PIPE IRRIGATION in such form as to aid the rapid solution of all problems relating to the flow of water in pipes. In orde*r to simplify Kutter's formula for computation of velocity of flow in pipes under varying conditions of roughness and diameter, Mr. Flynn reduces it to the following form, after computing Tables XVIII and XIX to facilitate its use : K \/ff. : - . (7) The value of the coefficient C for new iron pipes of 36 to 72 inches diameter ranges between 100 and 115 and changes little with changes of velocity. For such pipes tar-coated the value of n may be taken as .012 to .015 (see Art. ooo). For wooden-stave pipe values of C from no to 125 have been ob- TABLE XVIII. VALUES OF K FOR USE IN FLYNN'S MODIFICATION OF KUTTER'S FORMULA. n K n K n K n K n K .009 .010 .Oil 245-63 225.51 209.05 .012 .013 .014 195-33 183.72 J 37-77 - OI 5 .016 .017 165.14 157.60 150.94 .018 .019 .020 145 -03 139-73 134.96 .021 .022 .023 i3- 6 '5 126.73 124.90 TABLE XIX. VALUES OF V~r FOR CIRCULAR PIPES OF DIFFERENT DIAMETERS. Diameter. V7 Diameter. VT Diameter. \/7 ft. in. in feet. ft. in. in feet. ft. in. in feet, 5 -323 2 .707 4 4 .041 6 -354 2 2 -736 4 8 .080 8 .408 ' 2 4 .764 5 .118 10 -456 2 6 .790 5 4 -155 .500 2 8 .817 5 8 .190 2 -540 2 IO .842 6 .225 4 -577 3 .866 6 6 -275 6 .612 3 4 -9 J 3 7 J -3 2 3 8 .646 3 8 -957 7 6 1.369 10 .677 4 i . 8 1.414 SHEET-IRON AND STEEL PIPES 343 TABLE XX. AREAS, ETC., OF CIRCULAR PIPES OF DIFFERENT DIAMETERS AND UNDER PRESSURE. Based on D'Arcy's formula of flow through clean cast-iron pipes, in which v = cV~r X \^T and Q = AC\Tr X \/7 Area in square feet = A; also, C\/~7 and AC\/ r. Diam. A cvV AC\/7 Diam. A CV7 AC\f* ft. in. sq.ft. ft. in. sq. ft. I .005 ii. 61 .063 2 4 4.276 85.39 365 I* .OI2 15-58 .191 2 8 5.585 9L5 1 5" 2 .021 [8.96 -413 3 7.068 97.17 686 3 .049 24-63 1.208 3 4 8.726 IO2 895 4 .087 29-37 2.563 3 8 10.559 107 1136 6 . 196 37-28 7.306 4 12.566 112 1414 8 349 43-75 15.270 4 4 14-748 117 1729 10 -545 49-45 26.952 4 8 17.104 121 2082 .785 54.65 42.918 5 19-635 126 2476 2 1.069 59-34 63.435 5 4 22.340 130 2912 4 1.396 63-67 88.886 5 8 25.220 '34 3388 6 1.767 67-75 119.72 6 28.274 138 3912 8 2.182 71.71 156.46 6 6 33-183 144 4782 10 2.640 75-3 198 7 38-485 149 5757 2 3-142 78.8 247 7 6 44-179 '54 6841 2 2 3.687 82.1 302 8 50.266 160 8043 tained with velocities of 2 to 5 feet per second in pipes 44 to 72 inches in diameter, the corresponding values of n being from .on to .014. 276. Sheet-iron and Steel Pipes. Sheet-metal pipes were first used for conveying water under pressure for hydraulic min- ing in the Far West, and when the people of that region turned their attention to agriculture they immediately came into favor for conveying irrigation water. There aje several varieties and makes of these pipes constructed either of iron or steel, and the prices for either are about the same. Steel is preferable to wrought iron chiefly for great pressures, since for lesser pressures its greater strength than wrought iron requires such a reduction in its thickness, if this strength is to be utilized, as would render it liable to collapse. Its surface, however, is more smooth and less liable to scale when bent. Wrought iron, on the other hand, is more rigid because of requiring greater thickness. It is there- 344 APPLICATION OF WATER, AND PIPE IRRIGATION TABLE XXI. AREAS, ETC., OF CIRCULAR PIPES OF DIFFERENT DIAMETERS AND UNDER PRESSURE. Based on D'Arcy's formula for flow of water through old cast-iron pipes, lined with deposit, in which v = v r X \/ * and Q = AC\/ r ; Areas in square feet = A ; also, Cv r and A Cv r. Diam. A Cx/7 ACVr Diam. A cV7 ACVr ft. in. sq. ft. ft. in. sq. ft. I .005 7.81 .042 2 6 4.909 59-45 292 I* .OI2 10.48 .128 2 8 5-585 6i.55 344 2 .022 I2 -75 .278 2 10 6-305 63-49 400 3 .049 16.56 .813 3 7.068 65-35 462 4 .087 J9-75 r -7 2 5 3 4 8.726 69 602 6 .196 25.07 4-915 3 8 10 -599 72.40 764 8 -349 2 9-43 10.27 4 12.566 75-7 951 10 -545 33-26 18.13 4 4 14.748 78.9 1163 -785 36.75 28.87 4 8 17.104 81.9 1400 2 1.069 39-9i 42-67 5 J 9-635 84.8 1665 4 6 1.396 1.767 42-83 45-57 59-79 8o-53 5 6 6 23-758 28.274 89.1 93-i 2116 2632 8 2.182 48.34 105-25 6 6 33-183 96-9 3216 10 2.640 50.66 !34 7 38-485 100.6 3872 2 3-142 52.96 1 66 7 6 44-179 104.1 4602 2 2 3.687 55- 2 6 204 8 50.266 107.6 54io 2 4 4.276 57-44 246 TABLE XXII. VALUES OF C\/7 FOR VARIOUS DIAMETERS AND COEFFICIENTS OF ROUGHNESS H, FOR CIRCULAR PIPES FLOWING FULL. Based on Flynn's modification of Kutter's formula, v = C\/ r X \/ i and Q = d ft. in. n=.bn CVT n=.oi3 cV7 H=.OI7 CVT- d ft. in. n=.on cV7 n=.OI3 CVT =.oi7 cV7 6 3-9 24.6 16.98 3 4 124 103 75 8 38.7 3 1 21.6 3 8 132 no 80 10 45-8 36-9 25.8 4 140 116 86 52.8 42.6 3 4 4 148 123 9i 2 59-i 47-8 33-9 4 8 J 55 129 95 4 65.2 52-9 37-6 5 163 135 IOO 6 7i 57-8 4i-3 5 6 i73 144 1 08 8 76.8 62.6 44-9 6 183 153 114 10 82.1 67 48.2 6 6 J 93 161 121 2 87.4 71.4 5i-6 7 202 169 127 ' 2 4 97-3 79-9 57-9 7 6 211 177 133 2 8 107 87-9 64 8 220 184 139 3 116 95 70 SHEET-IRON AND STEEL PIPES 345 fore less liable to be dented or otherwise injured, and being more porous it takes the asphalt coating better than does steel. The plates from which these pipes are made are usually annealed, and in the case of wrought iron a tensile strength of about 45,000 pounds per square inch and in steel about 60,000 pounds per square inch is called for. There are many makes of pipe, the more prominent of which are lap-welded, converse lock- jointed pipe; straight, double- riveted, and spiral-riveted pipe. These are made of plate ranging from 18 B.W. gauge down to No. 10 gauge, and even thicker. Safe working stresses, in pounds, for the various gauges of metal more usually employed are as follows: No. Thickness. Pounds Square Inch. 16 !... .16 6,000 14 08 7o 12 ii g,ooo 10 14 12,000 iV- - I0 14,000 Straight-riveted pipes are double-riveted along the seams, and as delivered several lengths are riveted together or lap- welded, making the section as delivered from 20 to 25 feet in length. The distance apart between rivets in the rows varies from .33 to .40 inch, and the distance between any two rows is about f of an inch. Spiral-riveted pipe, as its name implies, is made by curving the plates spirally into a cylindrical form, and it is believed that this method of riveting gives a little added stiffness, owing to the manner in which the riveting and the seams are disposed around the circumference of the pipe. Laminated pipe is made by rolling together and uniting at the edges two sheet-metal plates each of half the thickness necessary for an ordinary pipe. The inner shell is telescoped into the outer while immersed in hot asphalt, thus making a barrier to corrosion. All sheet- metal pipes depend for their length of life on the resistance to rust of the asphalt coating given them. This coating has a thickness of to 7 V of an inch, and is made as nearly im- pervious as possible on both the inner and outer surfaces. The composition of this coating is various proportions of asphaltum 346 APPLICATION OF WATER, AND PIPE IRRIGATION fluxed with crude oil and heated nearly to burning-point. In this hot fluid the pipes are inserted. There is a decided difference in various makes of pipe as to the amount and character of the flux used with the asphaltum, and each maker has his own special variety and mode of application. Well-coated pipes have been frequently examined which have remained clean for 15 to 25 years. On the other hand, uncoated pipes rapidly corrode, thus dimin- ishing their carrying capacity as much as 75 per cent for 6-inch pipes and less for larger diameters. Tar-coated pipes 15 years old and 48 inches diameter have had their carrying capacity re- duced 25 per cent by tuberculation. 277. Wooden-stave Pipes. There are a number of varie- ties of this make of pipe, among the first to find favor being that known as the Colorado wooden pipe, the invention of Mr. C. P. Allen of Denver. There have since been put on the mar- ket various modifications of this pipe, each possessing special advantages. The chief differences in these various forms of pipe consist in the method of binding the edges of the staves together, that is, the form of the groove or lug with which they meet and the mode of uniting or fastening the ends of the metal binding- rods. These pipes are made in sizes from 10 inches up to 72 inches in diameter, while even larger diameters might be used if desired. The walls of these pipes are of wooden staves bound together by steel bands. These staves are shaped on the broad sides to cylindrical circles and the edges to true radial lines, so that when put together they form a perfect cylindrical pipe. To join the ends of the staves a thin metallic tongue is in some cases inserted, this being a trifle longer than the width of the stave and cutting into the two adjoining staves. The confining bands are of round or flat iron or steel f to f inch in diameter, according to the pressures to be withstood and the diameter of the pipe, and are shipped from the factory as rods. These rods are provided at one end with a square head, at the other with a thread and nut. They are bent on the ground on a bending table to the proper form, and are coated with mineral paint or asphaltum varnish and cut about 6 inches longer than the outside circumference of CONSTRUCTION OF WOODEN PIPE LINES 347 the pipe, on which they are slipped loose. As the construction of the pipe progresses these binding-rods are screwed up gradually until brought to a uniform tension on the whole length of the pipe. In some forms of pipe the coupling or saddle in which the rod ends are fixed is of cast iron. In one the threaded portion of the binding-rod is upset and an eye formed at the other end which fits into a special casting, and instead of a metallic tongue at the stave ends, a flat V-shaped groove is used, a similar groove being also employed on the edges of the staves. The best materials from which to make such pipes are Oregon pine and California redwood. The latter has a great advantage over any other, in that it has a great crushing strength which prevents rounded bands from penetrating the wood in case of excessive strain due to the swelling of the wood when saturated. The staves are usually prepared for the larger diameter of the pipes from carefully selected 2 X 6-inch joists, which are dressed down less than one-half an inch in either direction. The dis- tances apart of the binding-rods vary from 5 inches apart be- tween centers under great pressures up to 12 inches under lesser pressures, and in putting these pipes together the staves can be so dressed and the binders so placed as to accommodate pipes to moderate curve both vertically and horizontally. The diameter of the pipes may be reduced during construction by inserting tapering staves at proper places, and the reduction can thus be made without any abrupt change of diameter, but gradually. 278. Construction of Wooden Pipe Lines. Wooden pipe lines should be so aligned and located as to be kept well below the hydraulic grade-line in order that the pipe shall not only be kept full of water, but under pressure at all times, otherwise it will rapidly deteriorate. Care must be taken in aligning a wooden pipe to introduce as few and as large curves as possible, owing to the difficulty of constructing these. After the staves have been dressed they must be kept under cover to avoid warping or checking. Care must be taken in tightening the binding bands, for, no matter how tightly these may be fastened when the pipe is built, they will be comparatively loose within a couple of days, and water will be spurting from every seam. 348 APPLICATION OF WATER, AND PIPE IRRIGATION Experience differs as to the desirability of burying wooden- stave pipes in the earth, and of coating the wood. Pipes which are above the surface are exposed to destruction from fires. Such coatings as coal-tar and asphaltum only increase this danger, and in general this class of coating is not recommended. For the interior of flumes and of pipes asphaltum has certain pre- servative advantages; but the great disadvantage of such coating on either surface is that it prevents free soakage of the wood and the passage of the water from the interior to the exterior of the pipe, for on the constant saturation of the wood is largely de- pendent its preservation. It is believed that wooden-stave pipes above ground, kept saturated, will last longer than the metal binding-rods underground. The tensile strength of the binding-rods is affected (i) by the pressure in the pipes; (2) by the pressure arising from the expansion of the wood; (3) by the tensile strength of the rod itself; and (4) by the compressive strength of the wood. Mr. C. K. Bannister gives the following simple formula for deter- mining the distance between adjacent bands : Let d = distance in inches between two bands; / = maximum tensile strength of each band in pounds ; p = pressure of water in Ibs. per sq. in. measured at bot- tom of pipe; r = internal radius of pipe; C = coefficient to allow for strain caused by swelling of wood; also includes factor of safety in binding- rods. Then Practice indicates that C is generally equal to about 4 or 5 as a factor of safety. In some cases it is believed desirable to anchor inclined wooden pipes in order to prevent their creeping. More recent experi- ences indicate, however, that where such pipes are carefully constructed, and where their ends terminate in substantial pen- stocks of heavy timberwork or masonry, there will be no tendency REINFORCED CONCRETE PIPE 349 to creep, and the mode of construction of the pipe itself creates a stiff shell of such large diameter as practically to prevent any such tendency. 279. Reinforced Concrete Pipe. This material is used quite extensively on the more recent works of the Reclamation Service for pipe culverts, siphons, etc., and in a few instances for long pressure pipes. The most notable example of the latter use is on the line of the power canal of the Roosevelt dam, Arizona. At the crossing of Cottonwood canyon is an inverted pressure pipe 250 feet long under a head of 76 feet, and at Pinto Creek FIG. 131. Travelling Forms for Moulding Concrete Pipe. crossing a length of 2130 ft., and a head of 35 ft. At both places are two lines of pipe each 5 ft. 3 inches inside diameter, with a thickness of 6 inches and 7 inches respectively, at the two cross- ings. Each pipe is of concrete, that at Cottonwood crossing being reinforced circumferentially with f-inch rods 6 inches centers, and longitudinally by six rods of f-inches diameter. At Pinto crossing the reinforcing rods are of the same dimen- sions, spaced and 3 inches centers circumferentially and with ten rods longitudinally. These pipes were moulded in place by use of an ingenious system of outside detachable steel framework with wooden lag- 350 APPLICATION OF WATER, AND PIPE IRRIGATION ging and inner travelling form called an "alligator," the whole the design of F. Teichman. The plates of the alligator formed the lower semicircle of the inner mold, the upper stationary plates being erected over the slowly moving alligator and supported on rails. These were built in half cylinders bolted to those pre- viously erected so as to form a rigid upper half cylinder of 70 feet length. The lower half cylinder of the alligator had a length of about 24 feet, beyond which it sloped for 10 feet to a point. In the construction of concrete pipe for sewers in Indianapolis, Ind., very simple collapsible sheet-steel, half -cylindrical forms were used. The lower half of the forms consisted of short sections about 3 ft. long, with top bracing. The upper half form was over 50 feet in length and was hauled forward by block and tackle (Fig. 131). 280. Measurement of Flow in Pipes. Where water is pumped an excellent measure of the volume discharged from pipes can be obtained by noting the capacity of the pump per stroke and the speed and time of running. Otherwise the only satisfactory method of directly measuring their discharge is by means of some of the various patented water-meters. Measurement by com- putations depending on the diameter of the pipe, head of water and consequent theoretic velocity is not at all satisfactory. There are a number of water-meters on the market, nearly all of which give satisfactory results, though some of them are apt to be clogged by sediment in turbid waters and others are too heavy and cumbersome or too expensive to be satisfactorily used on irrigation work, except where water has an extremely high value and is sold by careful measure. Perhaps the form of water-meter which is most likely to find favor among irrigators is the Venturi meter, the invention of Mr. Clements Herschel. These meters are made in all sizes, from those suitable for measuring pipes a few inches in diam- eter up to meters capable of utilization on pipes 6 or 8 feet in diameter. This meter consists of two pipes forming the tube, and of the register. The former consists of two funnel-shaped pipes of different tapers, while the latter is a delicate electrical recording apparatus with dials, etc., which registers the volumes MEASUREMENT OF FLOW IN PIPES 351 discharged (Fig. 132). This meter is not affected by water- hammer, dirt, sticks, or other substances. The principle on which it works is that of measuring the differences of pressure due to friction in passing through the throat of the pipe, for it is well known that the pressure is less at the throat or contraction than at the up-stream end. A peculiar feature of this instrument is that this difference in pressure does not produce any appreciable loss of head, as is the case with other meters; and the final result of the principle on which it depends for its action is summed up in the rule that "the faster the flow of the water through the Venturi Chart Recorder continuously Record* cubic feet per second FIG. 132. Venturi Meter and Recording Device on Lateral Head. tube the greater is the difference in pressure at the up-stream end and at the throat of the tube; and the slower the flow the less the difference in pressure." Upon this principle the action of the meter is based, and by utilizing these differences of pressure the amount of flow is shown by the register. Except for the delicate registering apparatus this instru- ment is not necessarily expensive. It consists practically of a couple of cast-iron pipes moulded to fixed shapes. Cheaper forms of the Venturi meters are being constructed for use in meas- uring sewage of towns, and still cheaper forms are being de- signed in brick and cement, and even in wood, for measuring the discharges in open as well as closed irrigating channels. 352 APPLICATION OF WATER, AND PIPE IRRIGATION 281. Works of Reference. Application of Water, and Pipe Irrigation. BOVEY, HENRY T. A Treatise on Hydraulics. John Wiley & Sons, New York, 1895. FANNING, J. T. A Treatise on Water-supply Engineering. D. Van Nostrand & Co., New York, 1878. FINKLE, F. C. Pipes in California Irrigation. Irrigation Age, Chicago, Illinois, October, 1893. FLYNN, P. J. Irrigation Canals and other Irrigation Works. San Francisco, California, 1892. FORTIER, SAMUEL, Use of Pipes in Irrigation. Irrigation Age, Chicago, Illinois, July and August, 1893. Pipe Irrigation. Trans. Am. Soc. Irr. Engs., Denver, Colorado, 1893. Conveyance of Water. Water-supply Paper No. 43. U. S. Geological Survey Washington, D. C., 1902. GOULD, E. SHERMAN. Practical Hydraulic Formulas, etc. Engineering News Publishing Company, New York, 1894. HALL, WM. HAM. Santa Ana Canal of the Bear Valley Irrigation Company. Trans. Am. Soc. C. E., vol. 33, No. 2, New York, 1895. KING, F. H. Irrigation and Drainage. The Macmillan Co. New York, 1899. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. WILCOX, LUTE. Irrigation Farming. Orange Judd & Company, New York, 1895. Part III STORAGE RESERVOIRS CHAPTER XV LOCATION AND CAPACITY OF RESERVOIRS 282. Classes of Storage Works. A storage work is any variety of natural or artificial impounding reservoir or tank for the saving of flood waters. Storage works are employed to insure a constant supply of water during each and every season regardless of the amount of rainfall. They may be classified according to the character and location of the storage basin, or the materials and construction of the retaining wall or dam which closes it. Under the former classification are: 1. Natural lake basins; 2. Reservoir sites on natural drainage lines, as a valley or canyon through which a stream flows; 3. Reservoir sites in depressions on bench lands; 4. Reservoir sites which are in part or wholly constructed by artificial methods. For the second classification, see Art. 289. 283. Character of Reservoir Site. i. If situated in a natural lake basin, a short drainage cut or a comparatively cheap dam or both may give a large available storage capacity. Such sites are usually the cheapest, costing for construction as low as 20 cents per acre-foot stored, and in unfavorable cases rarely ex- ceeding $3 per acre-foot. 2. The most abundant reservoir sites are those on natural drainage lines, though these are usually the most expensive of construction owing to the precautions necessary in building the dam to provide for the discharge of flood water. 23 353 354 LOCATION AND CAPACITY OF RESERVOIRS 3. Almost equally abundant are those reservoir sites found in depressions on bench or plains lands. The utilization of such basins as reservoir sites is comparatively inexpensive; they can be converted into reservoirs by the construction of a deep drainage cut or of a comparatively cheap earth embankment, or both. Scarcely any provision is necessary for the passage of floods. The heaviest item of expense in connection with such sites is the supply canal for filling them from some adjacent source. 4. Artificial reservoirs are occasionally constructed where water is valuable, by the erection of an earth embankment above the general surface of the country or by the excavation of a reser- voir basin by artificial means. Such constructions are usually insignificant in dimensions, as the expense of building large reservoirs of this kind would ordinarily be prohibitive. Shallow reservoirs should not be constructed, since the loss from evaporation and percolation is proportionately great, and the growth of weeds is encouraged, where the depth is less than seven feet, by the sunlight penetrating to the bottom. 284. Relation of Reservoir Site to Land and Water-supply. There are several modifying considerations affecting the value of the reservoir site. Among the more important are : 1. The relation of the site to the irrigable lands ; 2. The relation of the site to its catchment basin or source of supply; 3. The topography of the site; 4. The geology of the site. The cost of water storage depends chiefly on the last two, while the value of the site for storing water and the possibility of filling the reservoir depends on the first two. In considering the relation of the reservoir site to the irri- gable lands, the former should he situated at a sufficient alti- tude above the latter to allow of the delivery of water by natural flow. The area of irrigable lands should be sufficient to make use of the entire amount of water stored, that the maximum return may be derived from water rates, and the reservoir should be as neaf as possible to the irrigable lands in order that the loss in transportation shall be a minimum. It not infrequently TOPOGRAPHY AND SURVEY OF RESERVOIR SITES 355 happens, however, that the reservoir is of necessity located at seme distance from the irrigable lands, thus requiring either a long supply canal or that the water be turned back into the natural drainage channel, down which it will flow till diverted in the neighborhood of the irrigable lands. This is very wasteful of water, since the losses by absorption, percolation, and evaporation are great, especially if the bed of a natural channel is used as a portion of the supply line. As related to the source of supply, the reservoir site may be on a perennial stream the discharge of which is more than sufficient to fill it, in which case the supply is assured. It may be on a stream the available perennial discharge of which is sufficient to fill it only in times of flood. It may be on an inter- mittent stream subject to occasional flood discharges of sufficient volume to fill the reservoir so as to enable it to tide over a couple of seasons of moderate supply. Or the reservoir site may be situated above and away from any natural drainage line, in which case it will receive its supply either by a canal diverted from some perennial stream or from artesian wells or springs. 285. Topography and Survey of Reservoir Sites. Knowing the position of the irrigable lands, a careful preliminary survey should be made of the entire neighborhood to discover all possible reservoir sites, and the outlines of the catchment basins of each of these should be mapped, while stream gauging should be con- ducted and examinations and inquiries made to ascertain the minimum discharge of the streams and their flood heights, as well as the amount of evaporation and percolation (Chapters III and IV). Having determined in a general way upon the location of the reservoir site, a detailed survey of it should be made. This can ordinarily be best done by means of a plane table. The highest possible point to which the dam may reach may be taken as a datum, and a top contour run out closing around the entire site. A main traverse should then be run through the lowest line of the site from the dam to the extreme end where it will connect with the top contour. Cross-section lines may be run from this with the plane table, and the topography of the site sketched in 5 -foot contours and plotted to some large scale, preferably 500 to 356 LOCATION AND CAPACITY OF RESERVOIRS 1000 feet to the inch. Where the country is open the site may be triangulated from one side, as a check on the cross-section lines, and where the slopes are even these may be best determined by means of gradienter lines run up and down them from a base contour. Such a map will enable the engineer to determine the capacity of the reservoir for various depths of water. To calculate the storage capacity of the reservoir the area enclosed by each contour must be measured on the map with a pi ammeter, and the mean area between adjacent contours multi- plied by the contour interval will give the volume. The sum of all the volumes between successive contours will be the full capa- city of the reservoir. There is quite an error by this method when the slopes are flat, in which case the prismoidal formula should be used. By this the volumes of two successive intervals in terms of three areas a, b, and c equals (a + 46 + c)-, where a, b, o and c are the two end and intermediate areas and d is the contour interval. The available volume of a reservoir is always less than its full capacity both because some portion is below the outlet sluices and because some part of the bottom will soon become filled with sediment. This is often one-fifth or more of the height of the dam, though a far less proportion of the reservoir content. Having determined the elevation of the outlet sluices, grade- lines must be run to determine the route of the canal which is to carry the water to the irrigable lands, also to ascertain whether it can be led to the higher or more arable portion of such lands (Art's. 137 to 139). The dam site should be surveyed in greater detail, several possible sites being cross-sectioned and mapped in i-foot con- tours and at a scale of 50 to 100 feet to the inch. This work should be done with transit and tape, whereas in the reser- voir survey the stadia may be satisfactorily employed on most of the cross-section lines. Several test pits or borings should be made at the dam site to determine the nature of the foundation. Samples of rock, clay, etc., should be collected and tested to determine its value as material for constructing masonry or EXPLORING FOR ROCK FOUNDATION 357 earth dams. With such a knowledge of the topography of a catchment basin and of the reservo ; and dam sites as the re- sulting map and data will give, the engineer may readily compute the cost of construction of dams for various heights as well as the contents of the reservoir for these heights, and thus determine what height of dam will be most economic of construction, for there is always some height which will render the unit cost of storage a minimum. 286. Exploring for Rock Foundation. Three methods may be employed to determine the depth of rock foundation at a dam site; these are, in inverse order of their merit: i, by sound- ing-rods; 2, by sinking open shafts; and, 3, by diamond core- drill. The first method consists in driving or churning solid steel sounding-rods, each 10 or more feet in length, and f to i inch diameter. The results are unsatisfactory, as friction in the gravel bed of a stream is such as to limit penetration to 25 or 30 feet. They are incomplete, as the rod may be stopped on a large bowlder and the kind and texture of the foundation material encountered cannot be examined. Shaft-sinking is usually quite expensive, owing to the cost of pumping and of carrying off the surface or stream water in a flume or other artificial channel. To sink such shafts to depths greater than 50 feet will cost from $20 to $30 per foot according to the nature of the material, and the depth and volume of surface and pumped water to be handled. For shallow depths this method is quite satisfactory, however, as the nature of the foundation rock can be readily examined. For considerable depths the method which is by all odds the most satisfactory and cheapest is by the diamond core-drill, since the result is certain and the physical and chemical proper- ties of the rocks penetrated can be tested. Several concerns make and sell the complete apparatus. The machinery is in two distinct parts: first, a pile-driving apparatus for putting pipe or casing down through quicksand or earth; the pipe is afterwards washed out, and inside of it the shaft with the diamond bits is operated. The second part is the drilling apparatus proper. The machinery is very light, and 35 8 LOCATION AND CAPACITY OF RESERVOIRS made so that it can be knocked down to weights that will admit of the sections being carried on the backs of men. The hammer is in sections and can be increased or lessened in weight. The bottom section is cored out and filled with wood, so that the blow of the hammer will not abrade the head of the pipe. It is raised by means of a hand- winding drum, and is tripped when it reaches the tops of the guides, and falls upon the pipe. The maximum lift is nj feet, and the maximum weight 190 pounds. A tool- steel head is screwed into the top of the drive-pipe for the hammer to fall upon. The pipe is shod at its lower end with a tool-steel shoe, which is thicker and heavier than the pipe, but equal to it in interior diameter. The size of the pipe used is 3J-inch, 2 J-inch, and 2-inch extra-heavy screw-pipe, with extra-heavy couplings which have bevelled corners. The smaller diameter pipe is in each case made to fit into the larger diameter if required. It, however, requires a special make of 2^-inch pipe to go inside of the 3J-inch pipe. The pipe is driven through the sand and gravel until bed-rock is reached. This is indicated by the refusal of the pipe to go any farther under driving. The pipe is cut in 5 -foot sections, and as it is driven into the ground new sections are put on until the desired length is reached. When the drive-pipe has reached bed-rock, what is known as a chopping-bit, which is a bit with openings for water to flow through its point, and to which is screwed a f-inch pipe, is worked into the drive-pipe. The top of this f-inch pipe is connected with a small double-action hand force-pump by a hose. The chopping-bit is churned around in the sand which is inside of the drive-pipe, and the water which is under pressure is discharged through the point of the chopping-bit, and floats the loosened sand out over the top of the drive-pipe. In this manner a hole can be readily cleaned to depths, as great at 130 feet of sand and small gravel. The diamond drilling machinery is put to work when the drive-pipe is cleaned out, and its use may demonstrate that, instead of being on a bed-rock, the drive-pipe has stopped upon a bowlder. As soon as the diamond bit passes through a bowlder GEOLOGY OF RESERVOIR SITES 359 it drops, which is an indication that bed-rock has not been reached. The diamond drill is then drawn and four or five sticks of giant powder are lowered through the pipe to the bowlder. The drive- pipe is then pulled up four or five feet, and the powder is dis- charged by means of an electric firing-batter)-. This shatters the rock, and the drive-pipe may then be forced through the splintered bowlder. Such a machine is capable of drilling 200 feet into solid rock. It is operated by hand, six men being necessary to handle it and the pipe. In soft rock it will make from 10 to 20 feet per day, and in hard rock from 5 to 10 feet. The cost of diamond core-drilling ranges from $i to $3 per foot, according to hardness of rock and locality, and including cost of plant where several deep holes are sunk. 287. Geology of Reservoir Sites. Having ascertained the desirability of the reservoir site topographically and hydro- graphically, a few test borings or trial pits should be sunk at various points on the reservoir basin, in addition to those at the dam site, to ascertain the character of the soil and the dip of the strata underlying the proposed reservoir. The geological con- formation may be such as to contribute to the efficiency of the re- servoir, or it may prove so unfavorable as to be irremediable by engineering skill. A reservoir site which is situated in a syn- clinal valley as shown in A, Fig. 133, is the most favorable. In this the strata incline from the hills towards the lower lines of the valley, and any water which may fall on to these hills will find its way by percolation through the strata into the reservoir, thus adding to its volume. An anticlinal valley is the least favorable for a reservoir site (Fig. 133, B). In such a valley as this the strata dip away from the reservoir site and would permit of the escape of much of the impounded water, percolation through the strata leading it off to adjoining valleys. A class of geologi- cal formation intermediate between these two is that represented in C, Fig. 133, in which the valley has been eroded in the side of strata which dip in one direction. Here the upper strata lead water from the adjoining hills into the reservoir, while the strata on the lower side tend to carry it off from the reservoir 3 6o LOCATION AND CAPACITY OF RESERVOIRS by percolation. In such a case it is probable that the reservoir would neither gain nor lose. If the surface of the proposed reservoir site is composed of a deep bed of coarse gravel or sand or even limestone, crevices in the latter or between the interstices of the former will tend greatly to diminish the capacity of the reservoir by seepage from it. Again, the geologic formation may be most unfavorable, yet if the surface of the reservoir site be covered with a deep FIG. 133. Diagrams Illustrating Geology of Reservoir Site. deposit of alluvial sediment or of clay or dirty gravel or other equally impervious material, little danger may be apprehended from loss by seepage. 288. Cost and Dimensions of some Great Storage Reser- voirs. In Table XXIII are given the capacities, material, dimensions of dam, and cost per acre-foot stored of some of the great storage reservoirs which are used for purposes of irrigation. 289. Classes of Dams. Dams may be grouped in five general classes, according to the materials of which they are composed, as follows : i. Earth dams or embankments. COST AND DIMENSIONS OF STORAGE RESERVOIRS 361 II SCO (NOOOOOCOu-, OOO1-O O O O O -tr;OOOOf^OOC . LT, rj- tree M ^ - Maximum Height of Dam. Fee fO OOC OQC fO O oC - r^ tr; "IOC OONV.ONOCQO v; o\O 10 r>. >- t \r.*C O ^ 'II OOOO tonv) N. h.i-ioocr)t^o M O- ir, O r < -oc w-r Hi!! g i, X - X I 60 s s .2 d.2 3^1 362 LOCATION AND CAPACITY OF RESERVOIRS 2. Crib or rock-filled timber dams. 3. Loose-rock or rock-filled dams. 4. Steel dams. 5. Masonry dams. These may be combined in many ways, giving rise to numerous varieties merging the different types. The prime essential of a good dam is that it shall be im- pervious and stable, since its function is to prevent the passage of water. The choice of the material of which the dam shall be con- structed, whether it shall be of earth, masonry, or loose rock, is dependent largely upon the character of the foundation, the topography of the site, and the cost of transportation. Earth dams when well constructed are fully as substantial as those of masonry, and in many cases they are far more so. In countries subject to earthquakes, or where the rock foundation is not thoroughly homogeneous, an earth dam is decidedly preferable to one of masonry. They are usually cheaper, and where trans- portation is expensive they are very much cheaper. Providing a substantial and abundant wasteway of a sufficient capacity to carry the greatest possible flood be provided, an earth dam is generally to be preferred in mild, damp climates. In warm, dry climates they are liable to dry and crack. Where the founda- tion is of rock, gravel, or hardpan, or where earth is scarce, rock abundant, and cement costly, a loose-rock dam may prove the most suitable type. For dams over 100 feet in height on solid rock foundations masonry is to be preferred, as earth or loose- rock dams are nearly as expensive when transportation is cheap, and are more liable to be badly built. A substantial masonry dam cannot be founded on loose gravel or soil; an earth dam should rarely be founded on rock, owing to the difficulty of making a tight joint between it and the earth unless a masonry core-wall is used; a loose-rock dam may be founded on rock, earth, or almost any material. CHAPTER XVI EARTH AND LOOSE- ROCK DAMS 290. Earth Dams or Embankments. There are five general types of earth dams: 1. Earth dams having a central core or wall of puddled earth; 2. Earth dams having a central core of masonry or wood ; 3. Earth dams built up in layers of homogeneous material, without central core or puddle facing. 4. Earth dams with selected material on water face and coarser material on lower face. 5. Earth dams of sand, gravel, etc., sluiced into position by hydraulic filling. 291. Causes of Failure of Earth Dams. An earth dam may fail (i) from lack of stability of cross-section; (2) from disintegra- tion by erosion of the material composing it. It may fail from lack of stability either by yielding to the horizontal pressure of the water overturning it, or by sliding on its base. The simplest form of calculation clearly demonstrates what is fully acknowl- edged by all engineers, namely, that the dam will not be destroyed by overturning or revolving about its lower toe; hence the only theory as to its destruction is that it may slide on its base. The conditions of stability will be unsatisfactory when the hori- zontal component of the water pressure against the bank equals the weight of the latter plus the vertical pressure exercised by the water to hold it down, and multiplied by the coefficient of friction. Such a case is rarely or never apt to occur. In point of fact such structures usually fail, not by overturning or sliding on their bases, but by the disintegration of their particles due to the erosive action of water. Failures from this cause are usually due (i) to insufficient wasteway; (2) to the mode of drawing off water through pipes or tunnels; (3) to carelessness in construction. , 363 364 EARTH AND LOOSE-ROCK DAMS 292. Dimensions of Earth Dams. When subjected to the con- tact of percolation water earth loses a certain amount of its sta- bility due to buoyancy, and therefore it is customary to give the inner slope of an embankment a greater inclination than the outer slope. These slopes depend on the character of the material. When the outer slope will stand with an inclination of i on 2 J the inner slope should be i on 3. The interior and exterior slopes of earth dams may be con- sidered as planes forming together an angle of not less than 90 degrees, and the figure should be so formed, in order to in- crease its stability, that lines of pressure passing from the in- terior faces at right angles may fall within its base. As one cubic foot of rammed earth weighs about 100 pounds and a cubic foot of water 62^ pounds, we find the base of a prism re- sisting the lateral thrust of the water does not require to be more than two-thirds of the depth of the column it supports. Hence all quantities above that are due to the natural slopes, the stability of the dam, and the prevention of percolation. In large works it is frequently a matter of close calculation to determine which will be the more economical dams exclu- sively of earth or those whose inner slopes are supported by retaining walls of masonry. The outer slope of the dam may vary between i on ij and i on 3^, according to the character of the material. Light sand requires the flattest slope. A firm mixture of gravel and clay will stand a slope of about i on ij. The inner slope of the dam should be about J on i greater than the outer slope. It is not unusual, as in the case of the Ashti dam (Fig. 137), to make the inner slope near the top a little steeper than the lower portion of the slope, the object being that a steep slope from i on i to i J reflects the waves, while a flatter slope breaks them up. The top width of the dam depends somewhat on circum- stances. A top width of 6 feet is the minimum which should be employed, and for a high dam is too small. A good rule as to the minimum top width of earthen dams 50 feet in height and over is to make their breadth 10 feet. For dams under 50 feet the top width should be 8 to 6 feet. As the dam settles in course of FOUNDATIONS 365 time, its top should be built up by adding material to the required height. The dam should always be several feet higher than the highest flood mark in order to prevent waves from topping it. Thus the height of the dam above the crest of the discharge weir should be in which D equals the depth of water in the reservoir above the weir crest at maximum flood; X equals the height of the top of the stone pitching above the surface of the maximum flood; C is a constant equal to 2 or 3 feet according to circum- stances, and is equal to the vertical height of the top of the dam above the top of the pitching. 293. Foundations. The foundation of an earth dam should be examined with great care. The best material on which to found it is sandy or gravelly clay, fine sand or loam. Such a structure should never be built on shale or slate; or on firm rock unless a masonry core-wall is used, when a firm bonding to prevent creep of water can be obtained between this and solid rock up to the level of the crest of the dam. A low concrete core-wall may be built on bed-rock, and in the lowest part of the latter loose rock be piled on the up-stream side to collect seepage water. This may then be led by a drain- pipe through the core- wall to the lower toe of the earth embankment. Great care should be taken in searching for springs or quicksands in the foundation. Sometimes a quicksand may be discovered at some little depth beneath a hardpan or other suitable foundation. In such a case it is sometimes possible to seal over the quicksand under the embankment, and found the latter on the upper stratum. Such an expedient is not entirely free from risk, and great care should be taken in joining the toe of the embankment to the foundation material, if necessary spreading earth and clay over the surface of the valley for some distance on either side of the dam. The first thing to be done in preparing the site of the dam is to remove all soil to a depth equal to that penetrated by roots. 366 EARTH AND LOOSE-ROCK DAMS If firm and impervious, the soil may be scored by longitudinal trenches, which will give the proper adhesion between the founda- tion and the embankment, and prevent the slipping of the latter. If a puddle wall or masonry core is to be built into the dam, the foundation for this should be sunk to a sufficient depth to secure its permanence. If a homogeneous dam is to be built and the foundation material exposed is not impervious, a trench should be dug, and this filled with some puddle material, as clayey gravel or gravelly loam, moistened and rolled or packed in layers; or with concrete in cement. 294. Foundations of Masonry Core and Puddle Walls. The foundations for a masonry core- wall should always rest only on firm, homogeneous rock, as described for foundations of masonry dams (Art. 331). In any case where only loose ma- terial or disintegrated rock is to be found, some other form of earth dam than one having a masonry core is to be recommended. The core-wall should have a perfect bond with the clean bed- rock, both under the dam and up the sides of the hill to a level with its crest; otherwise it may afford the means for creep of seepage water which will eventually destroy the structure. When a puddle wall of clay or earthy gravel is employed instead of a masonry core, equal precautions with regard to its foundation are necessary, though in the case of a puddle wall it is not necessary or desirable to found it on rock. The best foundation for a puddle wall is fine, loose material, as gravel or sand containing earthy material; a firm bed of clay, or a close- grained hardpan. This should be cleaned off and trenched so as to insure a firm seat and close bond for the puddle wall. 295. Springs in Foundations. It is a common occurrence to encounter springs in the excavations for the foundations of dams either of masonry or of earth. These springs are a great menace to the integrity of the structure, and it is due to their presence that some of the most disastrous failures of dams have occurred. Some engineers recommend that springs be carried away in drains securely puddled. This, however, is a difficult operation and one rarely possible of accomplishment. A single large spring may be easily followed back in a cutting until it can be taken up MASONRY CORES 367 in a pipe, but ordinarily the foundation is underlain by a number of small springs. One excellent way of dealing with a foundation containing a number of small springs is to begin construction from the inner toe and work progressively across the base of the dam to the outer toe, in such manner as to force the springs out from under the foundation, or, if possible, to smother them. Where a cement puddle or core-wall is used, in the foundation of which a number of large springs are encountered, the foundation may be closed over these by leaving a little hole or tube through which the spring may issue. This is coaxed upward as the wall is carried up until a point is reached above which the spring does not rise. Or the diameter of the tube may be diminished until it becomes too narrow for the passage of the water owing to its diminished head and increased friction. 296. Masonry Cores, Puddle Walls, and Homogeneous Em- bankments. There is still a wide difference among engineers as to the best type of earth dams. Occasionally in England and in a few cases in our own country earth dams have been built up homogeneously, the front or water face being covered with a deep layer of some puddle material, as clayey loam. This practice, however, is falling into disuse, and engineers now rarely trust to a puddle face alone for protection against leakage. A wooden or plank core should never be employed. The material is sure to rot and decay, while the smooth surface of the boards offers an excellent route along which leakage water will travel until it finds an outlet. Again, it is impossible to make a wooden wall sufficiently substantial to withstand leakage and the tendency to rupture which may result from the settling of the bank. Recently steel core-walls have been used both in earth and in rock-fill dams in the West (Arts. 307 and 311). The masonry core is in great favor with many engineers, both in Europe, India, and America. A central core of puddled earth is subject to rupture from the settlement of the embank- ment. Both are practically impervious to leakage, and the masonry core especially so to burrowing animals. In build- ing such core walls they must be carried sufficiently deep to reach 368 EARTH AND LOOSE-ROCK DAMS some impervious stratum, and far enough into the side walls of the valley to prevent the passage around their ends of seepage water which would travel along their impervious faces. The con- struction of a dam composed for a portion of its length of earth and for the remainder of loose rock or masonry is dangerous, and the writer is opposed to such combinations which have re- cently been measurably condemned by the abandoment of this type for the new Croton dam. Moreover, masonry, either as a retaining wall, core, or culvert, is rigid, while the other material is flexible, and any settlement in the latter leads to rupture in the former. Furthermore, masonry offers a smooth surface for the travel of seepage water and thus tends to aid any internal erosive action which may set in. The earth dam with masonry core is probably the most popu- lar at present, especially for very high dams and those with which other masonry structures combine, as masonry wasteways or extensions of the dam, for then a safe bond can be made between the core-wall and its adjoining masonry work. Magnificent examples of such works have recently been built for the Boston water-supply and the New York water-supply. Engineers, to a limited extent in India and to a large extent in our Western irrigation region, favor the earth dam built up in homogeneous layers without puddle or core-wall, each carefully rolled or tramped over in such a manner that the whole dam is a dry puddle wall. This character of construction has all the advantages of imperviousness to leakage if the work is well done, while it is free from the disadvantages possessed by dams with central cores, namely, a smooth surface along which water may travel, and liability to rupture in the wall. With such a form of dam one or more trenches are usually excavated in the foun- dation and parallel with its axis. These may be carefully packed with the material of which the dam is built, or with puddle mate- rial to prevent leakage under and around the dam. The embank- ment material as laid down may be so selected as to get the finest and least pervious constituents in the front portion of the dam, leaving the heavier and coarser material to the rear to give stability. Such a form of construction is popular with the Reclamation MASONRY CORE-WALLS IN EARTH EMBANKMENTS 369 Service, and practically converts the dam into one having an impervious face of great thickness (Fig. 134). 297. Masonry Core-walls in Earth Embankments. The pri- mary object of a masonry center wall is to afford a water-tight cut- off to water of percolation. It is the dam proper, for it retains the water in the reservoir, the earth embankment on either side being only of service in keeping the center wall from being thrown down. A great advantage of the masonry core is that it affords an excellent opportunity for making the connections with the outlet tower and the culverts for the discharge sluices. These masonry culverts running through the center of an earth dam constitute one of the weakest points in its construction, and offer FIG. 134. Cold Springs Dam, Umatilla Project. Oregon. the greatest opportunity for the passage of seepage water. They can be so bonded with the masonry core as to form part of it, and preclude the possibility of the water following along the culverts. The masonry core should be carried to a height equal to that of the sill of the escape-way, while in very high dams it is well to raise it to the extreme flood height. It should be as thin as possible in order to reduce its cost, yet, as some move- ment may take place in the embankment owing * to settlement, it should be sufficiently heavy to be self-supporting. A safe and usual rule is to give it a top width of 4 to 5 feet, and to in- crease its thickness toward the bottom at the rate of about i foot in 10. This center wall should be composed of the best concrete. An excellent example of a masonry core or center wall for an earth dam is that in the Titicus dam of the Croton water- 24 EARTH AND LOOSE-ROCK DAMS shed, New York (Fig. 135). This masonry core is 17 feet thick at the base, where it is founded on rock, and retains the same dimensions for a height of 85 feet, above which it tapers to 5 feet in thickness at the top, which is 20 feet below the top of the em- bankment. The latter is 30 feet wide on top with slopes of 2\ to i with a - aximum height of 124 feet. The Boston Water- works Department has a practice of backing the core-wall by FIG. 135. Cross-section of Titicus Earth Dam, New York. a sort of buttress on the up-stream side of fine selected material puddled, and containing clayey matter, the remainder of the embankment being of any coarse and heavy material, especially on the lower side. The outer slopes are made of loose gravel to prevent slips, which are more likely to occur in clayey soil (Fig. 136). The core- wall has occasional buttresses of masonry 144^ 9 ' Flood Level, El. 251.25 ^s6* El. 251.5 && ; m?^ FIG. 136. Core-wall and Earth Embankment, Boston Water- works. to prevent longitudinal creep of water, and the up-stream surface is well plastered with cement. 298. Puddle Walls and Faces. The puddle core-wall is not considered as satisfactory nor as efficient as the masonry wall. The proper material for a puddle is not always obtainable, while water for moistening it is frequently impossible to obtain in the PUDDLE TRENCH 371 arid region. It is difficult to prepare, and requires careful manipulation in placing. Where too much responsibility is rested in the imperviousness and security of the puddle wall it is frequently a menace to the structure, as it is rarely built with sufficient care. A puddle wall should have a thickness of 8 or 10 feet at the level of the water line, and should increase in thick- ness downward to the surface of the ground at the rate of about i foot in 10. Where a puddle wall is employed, the material of which it is constructed is usually clay, or gravel and clay moist- ened and puddled in layers of about 6 inches in thickness, and permitted to dry slowly. On either side of it selected material is usually placed, the remainder of the dam downward consisting of the poorer and most available material. A puddle face, a form rarely employed, consists of a covering FIG. 137. Earth Dam with Puddle Face, Monument Creek, Col. on the whole inner face of a layer of puddle 8 or 10 feet in thick- ness at the base and 2 or 3 feet in thickness near the summit, and on the whole is placed a layer of common soil on which the riprap is laid (Fig. 137). In a few instances the puddle face has been mixed with small stones or furnace cinders as an obstruction to the passage of moles, gophers, or other vermin, which are the greatest menace to any structure depending for its imperviousness on a puddle wall or face. One of the serious objections to a puddle face is its liability to slip if the reservoir is drawn down so quickly as not to give it time to dry, for this is a slow process in so close-grained a material as a puddle of clay. 299. Puddle Trench. This is employed only where the dam is built up in homogeneous layers without a central wall. 372 EARTH AND LOOSE-ROCK DAMS It consists of one or more trenches excavated longitudinally the entire length of the dam down to some impervious stratum, or, if none can be found, for a very considerable depth. The trench is then filled either with puddle material built up the same as is a puddle wall, or with a wall of masonry built up as a core-wall, and the material filling this trench is carried up several feet abovj the surface of the ground. The trench should be carried up the slopes of the surrounding hills till it terminates at a level with the top of the embankment, and its bottom should be level in all directions, all changes of level being made by means of ver- tical steps. An excellent example of a puddle trench is that in the Ashti dam, India (Fig. 138). This trench was carried down to a hard bed of trap-rock, and in some places to consolidated clay. In this a puddle was laid in layers 4 inches thick which were reduced to 3 inches by watering and rolling. This puddle trench is rect- angular in cross-section, lofeet in width throughout, and generally 1 6 feet in height to the summit of the material filling it. The crest of the material filling the puddle trench was raised to a height of i foot above the surface of the ground so as to form a water-tight junction with the earthwork of the dam. Across the bed of the river along the center line of the dam the trench was made but 5 feet in width, and was carried down to bed-rock and extended 100 feet into the banks of the river on either side, and was filled with a wall of concrete. The use of a puddle trench is open to the same general objections as a puddle or core wall, but in a less degree. One of its great advantages where filled with masonry is that it furnishes an excellent bond for the outlet pipes and culvert, and as a barrier against creep of water along these. A good example of this form of construction is to be found in the Santa Fe dam (Fig. 139), in the bottom of which are four parallel masonry puddle trenches. 300. Homogeneous Earth Embankment. This type of dam is considered by the writer and by many other engineers as the most safe, efficient, and economic. It is generally preferable in the arid region because of the saving in transportation of cement, rock, or selected materials for a core-wall. It should be of the HOMOGENEOUS EARTH EMBANKMENTS 373 9 374 EARTH AND LOOSE-ROCK DAMS same density throughout, and composed of material practically impervious to water. It should form with the natural material on which it rests a perfectly homogeneous mass. Practically it is difficult to obtain such a structure, though the engineer should come as near as possible to the ideal. In a homogeneous earth dam the up-stream face is that point at which the water pressure ceases either by the water ceasing to penetrate the body of the dam or by its having free egress from the down-stream side. A core-wall will, on the other hand, stop the small amount of water coming through a new dam, and this will accumulate in the earth against the core, and will finally permeate the whole body of the dam above the wall, thus causing the water pressure which should be exerted against the up-stream face to be exerted against the core. The whole duty of the dam is then performed by the core-wall and the material below it. If enough impervious material cannot be had to build the whole structure up homogeneously in layers, the up-stream third or half should be built of the best material available, the poorest and heaviest being put in the lower side. These two classes of material should be well worked into one another so as to give a perfect bonding. This practically converts the principal third of the dam into a dry puddle face, only the whole structure is built up at the same time in irregular layers of 6 to 15 inches in thickness, and well tramped over or dry-puddled. By not building it in uniform layers a better bond is given to the struc- ture. With such a form of construction any water which may soak through the upper third will find free egress from the dam on its lower side. The result will be to keep water out of the dam if possible, but when it enters to pass it through quickly. The layers should be so disposed that the outer edges or extremities of each shall be higher than the center of the layer by from 2 to 4 feet. As built in the West with teams and scrapers, no run- ways should be provided, the teams being driven over the whole surface, thus adding to the density and compactness of the struc- ture. As each layer is built up it is well to drag or harrow it, and then pass a heavy roller over it. The same result can be produced by rolling it with a heavy roller having annular pro- 376 EARTH AND LOOSE-ROCK DAMS jections or rings on its surface. Excellent results in compact- ing such dams have recently been gotten on the Santa Fe dam (Fig. 139) by keeping a band of goats tramping constantly back and forth over the surface during the period of construction, loo goats doing the work for about 20 wheel scrapers. 301. Embankment Material. The ideal material of which to construct an earth dam is such a mixture of gravel, sand, and clay that all the coarser interstices between the particles of the former shall be filled by the sand, and that all the minute openings between the particles of this material shall be filled by the still finer particles of clay. This would give such a com- position that water would pass through it with the greatest amount of resistance, and the bank would be practically im- pervious. In practice, with proper care to mix the materials so as thoroughly to incorporate them one with the other, the following proportions should be used: Coarse gravel i .00 cubic yard Fine gravel 0.35 " " Sand 0-15 " " Clay 0.20 " " Giving a total of about 1.70 cubic yards, which when well mixed, compacted, and rolled can be reduced to about i\ cubic yards in bulk. These proportions will rarely be obtained, but the effort should be to approach as nearly to them as possible in order to produce the best combination of materials. Weight is a valuable property in an earth embankment, and such a com- bination as above given possesses the greatest amount of weight obtainable with earth. The sand and gravel lack cohesiveness but have stability, while clay, though cohesive, is liable to slip if unsupported. The above combination possesses the qualities of weight, cohesiveness, stability, and imperviousness, while the angle of repose or the slope which can be given is about midway between that possible with fine sand and that to be obtained with shingle or a mixture of sand and clay. If judgment be used in choosing materials, dirty gravel or that possessing a large amount of soil and sandy matter may often be found which will give nearly the proportions above specified. EMBANKMENTS OF SAND 377 Recent experiments by Prof. E. W. Hilgard with alkali soils in California (Art. 44) shows that black alkali carbonate of soda puddles clay soils so as to make them impervious and untillable, and sandy soils so as to produce a tough hardpan through which water cannot pass. Puddle walls in dams watered with a one-tenth per cent solution of carbonate of soda will be rendered water-tight, and so tough and solid as to resist pressure and erosion to a remarkable degree. 302. Embankments of Sand. Sand has occasionally been used as the material of which to construct embankments, but generally in a very small way. A very large dam of such mate- rials is that at Kalegh reservoir, India. This reservoir has an embankment composed entirely of sand, abutting on rock at one end. It was commenced in 1880 and completed in 1882, and is, financially speaking, the best paying irrigation work in Central India, having cost only $60,000, while the revenue realized aver- ages a return of 15.75 per cent per annum. The embankment which is thrown across the river Bandi is composed entirely of sand, the inner slope four to one, and the outer slope three to one, the width at the top being 20 feet. At the point at which the embankment abuts on to the rock a core- wall of masonry, 30 feet long and 2 feet thick, was built into the dam to prevent water creeping along the face of the rock and en- dangering the sand dam. Rubble at the toe of the outer slope, 10 feet wide and 3 feet high, prevents any erosion of the outer slope. These measures have been completely successful. The length of the dam is 730 feet at the top and 305 feet at the bottom, and the height 50 feet. The greatest depth of water impounded is 30 feet, of which 25 feet is available for irrigation. The waste-weir, cut out of the rocky spur of Kalegh hill, is only loo feet long. The area of the lake is 1540 acres, and the total capacity of the tank is 13,300 acre-feet. 303. Hydraulic-fill Dam. The idea of building up a reser- voir embankment of earth by washing or hydraulicking earth from above it and sluicing it into position originated in the earliest days of hydraulic mining in California. Perhaps the first struc- ture of this kind to be built was the San Leandro dam, near 378 EARTH AND LOOSE-ROCK DAMS Oakland, Cal. (Art. 304). A smaller and similar type of dam is that described as having been built on the Turlock canal (p. 141). More recently two excellent examples of such structures have been built which have been fairly satisfactory, especially as to cost; namely, at Tyler, Tex., and at La Mesa, Cal. The former structure is of but moderate dimensions, being but 32 feet high, with maximum water depth of 26 feet, and capacity of 1770 acre-feet, the contents of the embankment being 24,000 cubic yards, the inner slopes of 3 on i, and the outer of 2 on i. The building of this embankment was carefully watched, and it was estimated that 65 per cent of the material sluiced into it was sand and 35 per cent clay, the average cost per acre-foot of storage capacity being 65 cents. The total cost of the work, including outlet-pipes, etc., was but 4! cents per cubic yard. La Mesa dam is one of the same series with Sweetwater and Otay, which provide the city and neighborhood of San Diego, Cal. It is constructed in a narrow gorge the materials of which are hardpan overlying some rock. The structure is 66 feet in height, 25 feet in width on top, 25 ij feet in extreme width at the base, with outer and inner slopes ij to i. The entire structure was finished by material transported by water and washed from the neighboring hillsides, the volume of the material being 38,000 cubic yards, the extreme distance of transportation being 2200 feet. The volume of water used in constructing the dam was about 7 cubic feet per second. As the stream of water was loaded with material it was conveyed by a 24-inch wood- stave pipe to the point at which it was deposited on the bank. In the first thirty days 21,000 cubic yards or 55 per cent of the structure was placed, the ratio of solid embankment to water being 3.3 per cent. In the beginning of the work a trench was excavated in bed-rock, 2 to 5 feet deep and 20 feet wide, through- out the entire length of the center line of the structure, and at right angles to this an outlet culvert was built through the dam consisting of a concrete conduit 48 inches wide by 30 inches high, in which were placed two 24-inch cast-iron pipes. Upon this masonry work the sluiced material was deposited. 304. Combined Earth and Hydraulic-fill Dam. One of the f COMBINED EARTH AND HYDRAULIC-FILL DAM 379 largest and best types of such a structure and perhaps the first built is the San Leandro dam near Oakland, California. The dam is now 500 feet long and 28 feet wide. The original width of the ravine at the base was 66 feet. The length of the axis of the base from toe to toe of slopes is now 1700 feet. The toe of the lower slope is 121 feet below the high-water surface of the reservoir. A puddle- filled trench was carried down 30 feet beneath the original surface, reaching rock, except at the FIG. 140. San Leandro Earth and Hydraulic-fill Dam, Oakland, Cal. k . . , '- -, v., .. east end, where 20 to 30 feet of solid clay was penetrated. The capacity of the reservoir is 113,270 acre-feet (Fig. 140). All that portion of the dam within a slope of i on 2 J at the rear and i on 3 at the face is built of choice material, carefully selected and put in with great care. The portion outside of the i on 2j slope-line at the down-stream side of the dam was sluiced in from the adjacent hills regardless of its character, and is of ordinary soil with more or less rock. This process of sluicing was to be carried on during the winter months, by gravity flow, when there was an abundance of water, until eventually it would fill the canyon below the dam. This would give an average 380 EARTH AND LOOSE-ROCK DAMS slope of i on 6.7 at the rear. In the bottom of the puddle trench are three parallel concrete walls each 3 feet wide by 5 feet high. The wasteway consists of a tunnel 10 by 10 feet in section, 1487 feet long, with a 2\ per cent grade and lined throughout with masonry. The dam has a total volume of 542,000 cubic yards, of which 160,000 cubic yards were sluiced in. 305. Interior Slope and Paving. The interior slope of an earth dam is rarely made uniform, while the exterior slope, though usually uniform, is sometimes broken by a level bench (Fig. 136), the object of which is to prevent serious effect from the sliding of the embankment. This bench is usually made from 4 to 6 feet in width. On the interior slope one or more similar benches are sometimes introduced. In the case of the great dam built by the Reclamation Service near Belle Fourche, S. D. (Fig. 141), the slope is broken by two benches, each 8 feet in width. In addi- tion to this break in the slope, it is not uncommon to give a lighter slope below the bench and a steeper inclination for the last 5 to 7 feet at the top of the inner slope (Fig. 137). This steepness at the top prevents waves at flood height from slopping over the crest of the embankment, the sharp angle breaking the waves up and reflecting them back. The bottom of the inner slope is some- times made steeper if the material will stand it, as it is not exposed to the air by the drawing off of the water as is the upper portion of the embankment. This interior slope is invariably paved with cobblestones or dry rubble tightly driven home and carefully placed (Fig. 137) or with concrete blocks. The object of this pitching is to protect the embankment against the erosive action of the waves, and its thickness depends on the height and violence of these. The maximum height of the waves depends on the fetch or distance from the shore where their formation commences, and may be determined by Stephenson's formula, where X equals the height of wave in feet and F equals the fetch in nautical miles. Rankine states that where an embankment of loose stone is exposed to the action of the waves it should be INTERIOR SLOPE AND PAVING faced with blocks set by hand, the least dimension of any block in the facing being not less than two-thirds the greatest wave height. The best way in which to lay the riprap is to place the stones with broad ends down- wards, rough squared stones being preferable, in order that they shall fit fairly close one to the other. The interstices should be packed with small stone chippings and finished off with earth (Fig. 133). This paving should be laid on a foundation of 10 to 20 inches of small stones and gravel tightly compacted. The Belle Fourche dam is paved with concrete blocks 8 inches thick and about 5 by 7 feet in plan, laid on 24 inches of gravel (Fig. 141). The entire height of the inner slope need not be pro- tected by a stone pitching. That portion of the slope which is below the level of the outlet- sluices requires no pitching at all, as it will not be subjected to wave action. The lower portion of the exposed slope need be pitched with a lesser thickness than the upper por- tion, as the fetch will be less, and consequently the wave height less and its erosive action proportionately diminished. At 382 EARTH AND LOOSE-ROCK DAMS the upper portion of the slope the pitching should be carried quite to the top of the embankment, and for safety might be carried across the top or be topped by a parapet, in order that any spray falling on the top of the embankment should do the least possible amount of damage. The top of the em- bankment may be given a slight inclination toward the reservoir, so that it will drain into it and not outward over the unprotected lower slope. For better protection of this exterior slope it should be planted with grass, or, better still, sods of considerable size should be placed upon it a few feet apart, in order that the roots of these may spread and entirely protect it from the erosive action of rain and spray. 306. Earth Embankment with Masonry Retaining-wall. r^^&S ^ \ '^^^^fev^O j A B FIG. 142. Cross-section of Kabra Dam (A) and Ekruk Dam (B), India. It is sometimes necessary to economize reservoir space, in which case one side of the embankment may be faced with masonry, though this combination is rarely successful or advisable. It has all the disadvantages of both earth and masonry dams with- out any additional advantages. The Kabra embankment in India (Fig. 142, A) is an example of this class of structure. It consists of a masonry wall on the front face of an earth embank- ment and having a steep batter of about 12 on i, while the outer portion of the embankment and the lower slope have the natural slope of the earth, which is merely used to give stability to the masonry facing wall, the latter being the dam proper. The masonry may be put in as in the case of the Ekruk tank in India (Fig. 142,$). This consists of a masonry core of such EARTH AND LOOSE- ROCK DAMS 383 dimensions as practically to form the entire dam, the earth being merely added to the bottom of the slopes to give stability. In this case the masonry dam has an inner slope of 12 on i, an outer slope of 2 on i, and a total height of 72 feet. Against it, on its upper side, is an earth embankment with a slope of i on 3, reaching to about 25 feet in height, and on the outer slope another earth embankment with a slope of i on 2, reaching to about 35 feet in height. Above this the masonry is unsupported. 307. Earth and Loose-rock Dams Pecos Dams. The dam at the head of the Pecos Irrigation Company's canal, at Avalon, New Mexico, furnishes an excellent example of this combined construction. This dam is shaped in plan like the letter L, the re-entering angle of which points up-stream. The long arm which composes the main dam is 1025 feet in length and varies from 5 to 50 feet in height; the short arm consists of a simple earth embankment 530 feet in length, with an aver- age height of 8 feet. Adjacent to the end of the dam farthest from the headgate is a wasteway 250 feet wide, excavated in limestone rock, its bed being 5 feet below the crest of the dam. At the lower end of the rock cut on the left bank of the river is an additional wasteway just below the end of the dam. This waste- way has a total length of 206 feet, its sill being about 2 feet lower than the one first mentioned. The main dam (Fig. 143) is com- posed of a prism of loose rock 12 feet wide on top, 100 feet wide at bottom, with a lower or outer slope of i on ij and an inner slope of i on {. The up-stream face is backed with an earth embankment the width of which is 10 feet at top and 200 feet at the bottom; its up-stream slope being i on 3^ and paved with 12 inches of stone riprapping. The lower portion of this slope near the outlet sluice is replaced by 10 feet in depth of loose rock for a total width through the dam of 75 feet, to prevent under- cutting by currents. In August, 1893, the dam was breached for 300 feet in length and to its full height. This was repaired, the crest raised 5 feet, and additional spillway provided to dis- charge 33,000 second-feet. In October, 1904, a flood carried away a large portion of the main dam. In 1905 the Reclamation Service acquired the 3^4 EARTH AND LOOSE-ROCK DAMS properties of the Pecos Irrigation Company and rebuilt the dam to the original height of 50 feet on lines similar to those of the old work. The spillways were considerably enlarged in capacity and the canal, which heads at the east abutment of the dam, has its water surface 24 feet below the dam crest. For the entire length of the dam, including the old portion which remained FIG. 143. Cross-section of Pecos Dam. standing, a core-wall is placed in the earth portion, founded on bed-rock and reaching to the level of water in the canal (Fig. 144). This core is partly of concrete and partly of heavy steel interlocking channel barsheet piling; the latter only in a portion of the old dam where it is driven from above to bed-rock. From the top of the concrete wall to the crest of the dam is a reinforced concrete diaphragm 12 inches at bottom, 8 inches at top, and 24 feet high. Higher up on the Pecos River is Lake McMillan, closed by largest obtainable rock to be placed along this edge FIG. 144. Avalon Dam, Carlsbad Project, Pecos River, N: M. a dam of similar design, but larger. This is 1686 feet long, 52 feet in maximum height, and 20 feet wide on top, the width at base being 40x5 feet. The up-stream or rock-fill is 14 feet wide on top, with upper slope of i on ij and lower slope of i on J, backed by an earth fill having a top width of 6 feet and an outer or lower slope of i on 3 J. MINIDOKA PROJECT AND DAM, IDAHO 308. Minidoka Project and Dam, Idaho. On the Snake River, Idaho, near Minidoka, a diversion dam and main canal FIG. 145. Dam, Regulator, and Head works, Minidoka Project, Idaho. built by the Reclamation Service controls nearly 150,000 acres. Connected with this project is a pumping plant which will de- 25 3 86 EARTH AND LOOSE-ROCK DAMS velop 17,500 horse-power during low stages of the river, and will thus raise sufficient water to irrigate 76,000 acres which are too high to be supplied through the gravity system. The diversion dam raises the water 47 feet at flood level and backs it up the river a distance of about 35 miles. It is constructed in two sections and of two types: (i) a rock-fill and gravel back-fill diversion dam, and (2) a masonry spillway. The rock-fill dam has down-stream slopes of ij to i, faced on the up-stream side with a filling of gravel having a slope of 3 to i (Fig. 146). This dam rises to a height of 8 feet above extreme high water, and is 25 feet in width on top. Longitudinally through the center of the rock-fill dam ROCK AND EARTH DAM 20 40 60 80 100 SCALE OF FEET FIG. 146. Rock-Fill Dam, Snake River, Minidoka Project, Idaho. is a masonry core-wall, 12 feet in height and 4 feet wide on top. The top of the dam is 56 feet above low water and has a maximum height above bed-rock of 86 feet. The spillway consists of a masonry weir, well bonded with the masonry core- wall of the rock-fill dam, and having a maximum breadth of base of about 13 feet and a maximum height of 14 feet, the top of the spillway being at an elevation lofeet below that of the crest of the dam, and over it water is expected to pass in maximum flood to a depth of 4 feet. At the end of the dam nearest the deepest channel of the river is a diverting-channel (Fig. 145) dosed by five regulating- gates each 8 feet wide by 10 feet high and working between LOOSE-ROCK DAMS 37 masonry piers reinforced with concrete. Each gate is raised by a pair of screws actuated by worm-wheel gearing. The total height of the top of the regulating-bridge above the bottom of the gates is 58 feet. The main south-side canal is 14 miles in length and irrigates by gravity 8000 acres, and conducts water to the pumping-station. Its capacity is 850 second-feet, and the capa- city of the main north-side canal is 1000 second-feet. The grade in this canal is about 0.007, anc l i* s length 12 miles. Its bed width is about 90 feet, and the banks are paved and have slopes of i to i. The top width of bank is 25 feet, of which the outer half is composed of loose rock. The regu- lating-gates at the head of this canal are 14 in number, separated by piers of reinforced concrete. Each gate consists of two leaves 5 feet wide by about 5 feet high, of steel well braced and worked by screw gearing through hand-wheels from an over-head bridge. 309. Loose-rock Dams. When properly constructed and well founded there is no apparent reason why a loose-rock dam should not be nearly as substantial as one of masonry. Such dams should be founded only on solid rock, hard-pan, or on very stiff clay or other unwashable material. This type of dam is the outcome of Western engineering practice, and was first in- troduced for the purpose of storing water for placer mining. It consists of a mass of loose rock placed together with some degree of care, the smaller stones being used to fill the inter- stices between the larger ones so that the settlement shall be the least possible. Such slopes are given the mass as it can safely Height 14 Feet 15 Ft. FIG. 147. Concreted Waste Weir, Snake River, Minidoka Project, Idaho. 388 EARTH AND LOOSE-ROCK DAMS stand, and it is rendered impervious to water by a heavy sheath- ing of tarred planking, an earth embankment on its upper face, or by a vertical diaphragm of steel or reinforced concrete. Water should not be permitted to flow over the crest or back of such a structure, as it is liable to cause settlement which may result in its rupture. An earth dam is cheaper than a rock-filled dam where ma- terials for such construction are available. If transportation is not expensive a masonry dam is frequently cheaper than a rock- filled dam owing to the difference in cross-section and the cor- respondingly small amount of material required in the former, though the cost per cubic yard is relatively high. One of the great advantages of the rock-filled dam is that it may be con- structed with very little difficulty in flowing water; another advantage is that a leak is not the menace it is in an earth or masonry dam, since the whole structure is expected to leak. A masonry dam is at all times in a state of unstable equilib- rium, while a rock-filled dam tends to improve with time, and if properly built may be benefited by occurrences which threaten other dams. Such a dam should not be used where water is valuable unless great care is taken in providing against leak- age. The foundation for a loose-rock dam should rest on impervious and unwashable material. If there be a surface covering of loose soil or gravel it should either be removed by carts, or if the current in the stream is sufficient it may be washed away as the dam is built up. A loose-rock dam should be built up in layers as is an earth dam, and in such manner that the center of each layer shall be lower than the outer extremities. The best cross-section for such a dam is an upper slope of 3 to 2 on i and a lower slope of i on i; anything less than this cannot be considered secure. Mr. R. B. Stanton, as a result of his experience in lining a composite dam with asphaltum concrete, recommends that the site be cleaned down to bed-rock and levelled off with proper toe catches, and that on this a loose-rock gravity dam be built from material carefully dumped in place by cableways. The WALNUT GROVE DAM 389 largest stones up to several hundredweight should be surrounded by smaller pieces so as to make the whole mass compact and reduce settlement to a minimum. The inner face should be care- fully dry-laid by hand, on a suitable slope from a thickness of several feet at the bottom, the joints being well filled with spalls. This upper slope, starting from the bottom, should be stepped back 3 or 4 inches for every 5 or 6 feet of rise, making such a series of steps all the way to the top, and on this surface a true asphalt concrete such as is described in Art. 338, 6 inches to i foot in thickness according to height, should be placed. The advan- tages of this system are that with the aid of the steps and with well-made materials no creeping of the asphalt surface will occur, and a perfect joint will be made between the bed-rock, side walls, and dam. 310. Walnut Grove Dam. This is an example of the earlier type of rock-filled dam. It was destroyed in February, 1890, by a great flood, though its destruction was not a result of faulty design, but of carelessness in one or two details of its construc- tion notably in the failure to provide an ample wasteway and in the careless manner in which the stores were dumped in the center of the structure. This darn (Fig. 148) rested on the firm rock of the stream bed throughout its length, with the exception of a small portion of the upper wall, which is believed to have rested on from 5 to 12 feet in depth of loose earth and gravel. This was the weak point of its construction. The slopes were steeper than the angle of repose of the loose rock, which was only held in position by the enclosing hand-laid dry walls. The dam was 420 feet long on top, 138 feet wide at the bottom, 10 feet in width on top, and no feet in greatest height, and con- tained nearly 50,000 cubic feet of material. It consisted of a front and back wall, each 14 feet thick at the base and 4 feet on top, with a loose-rock filling between; the whole made water- tight by a wooden sheathing. The upper slope of the dam was 2\ on i and the lower slope ij on i. This latter, however, was increased for the lower half of the dam to about i on i by the addition of a pile of loose rock after the completion of the struc- ture. The wooden sheathing consisted of logs from 8 to 10 390 EARTH AND LOOSE-ROCK DAMS inches in diameter and from 6 to 12 feet in length, built into the wall on its upper face and projecting therefrom about i foot. The upper and lower faces consisted of rough blocks of granite dry-laid in such manner as to form two loose-rock retaining-walls, between which the body of the loose stone was dumped. Verti- cal stringers about 8 by 10 inches were bolted to the projecting 400FI FIG. 148. Elevation and Cross-section of Walnut Grove Dam. ends of the logs built into the upper face, and these stringers were placed about 4 feet apart. Upon the face of the dam and over these stringers two thicknesses of 3 X 8-inch planking were spiked, and tarred paper was laid between the two. The outer face of this sheathing was finally calked, and the whole covered with paramne paint. ROCK-FILL STEEL-CORE DAM 391 311. Rock-fill Steel-core Dam. One of the first and by far the largest and best type of this variety of loose-rock dam is the Lower Otay dam in California. The site chosen is ideal for a masonry structure, but because of high freights and in- accessibility it was decided to adopt the loose-rock type after the masonry foundations had been laid with a thickness of 65 feet at the base and for a depth of 40 feet. The plan of making a rock-fill dam water-tight by inserting in its center a steel web plate filling the entire cross-section of the canyon originated with the president of the company, Mr. E. S. Babcock. This web plate is held in position by a heavy T iron anchored in the top of the finished masonry foundation by a one-inch bolt. To 125' H.W -882' CROSS-SECTION OF DAM FIG. 149. Rock-filled Steel-core Dam, Lower Otay, Cal. the vertical leg of this the bottom of the web plates were riveted (Fig 149). Each of these was 5 ft. wide and 17.5 ft. long, the bottom plates being .33 inch thick. At heights between 28 and 50 feet the thickness of the plates is reduced to J inch, while the plates are 8 feet wide and 20 feet with diminishing thickness above 50 feet in height. The riveted plates were calked on the water side and coated with asphalt applied hot with brushes To this a layer of burlap was attached while the asphalt was still hot, and this aided in holding the asphalt from flowing. Over this a harder grade of asphalt was placed and the whole was encased in a rubble-masonry wall laid with Portland- cement concrete. The thickness of this wall is 6 feet at the base, tapering to 2 feet, at a height of 8 feet, above whicb the latter 3Q2 EARTH AND LOOSE-ROCK DAMS dimension was maintained. The steel core was carried into the side walls of the canyon in a foundation trench excavated to solid rock, into which it was anchored with leaded bolts. The thickness of the masonry corewall was increased at the sides to a maximum of 20 feet from its normal width of 2 feet, the taper extending over distances of 20 feet. A peculiarity of this loose-rock dam is that no portion of it was hand-laid, the whole consisting of a rock-filled embankment which was left lying as it was dumped. The top width is 12 feet and the slopes on both sides stand at about i to i. The dam is 565 feet long on top and 150 feet in height above bottom of foundation, the greatest depth of water being 125 feet with a gross storage capacity of 42,000 acre-feet (PL XXIII). A few hundred feet beyond the east end of the dam is a channel 30 feet wide, 300 feet long, arid extending to a depth of 10 feet below the crest of the dam, which affords ample spillway. There were approximately 180,000 cubic yards of stone used in this structure, which was quarried below the dam and transported by a Lidger- wood cableway. In quarrying material two blasts of 4000 pounds and 8000 of Judson powder were exploded simultaneously, thus loosening about 60,000 cubic yards of material at one discharge. An outlet tunnel 1150 feet long and of circular section is provided through a narrow part of the enclosing ridge 1000 feet distant from the dam. At East Canyon creek, Utah, has been built a modification of the above type of dam which forms a reservoir of 5700 acre- feet capacity. This structure is 68 feet high above the creek- bed and 100 feet in length on top. Through the gravel-bed of the canyon there was first sunk a concrete wall 15 feet thick to bed-rock at a depth of 30 feet, and in the center of this wall the steel web plates were anchored. These were yVinch thick for the lower 20 feet, diminishing to -f& for the upper 28 feet. On the upper slope the rock fill has an inclination of to i, and on the lower of 2 to i, the top width of the dam being 15 feet. 312. Crib Dams. The general form of construction and several examples of crib weirs were described in Articles 172 and 173. Structures of similar design have occasionally been built of 394 EARTH AND LOOSE-ROCK DAMS sufficient height to form storage reservoirs. The employment of cribwork in a storage dam is not recommended, as such work is essentially temporary in character. As a result of the alternate wetting and drying which it receives it is very liable to rot, and the life of such a dam is manifestly shorter than that of an earth, loose-rock, or masonry dam. Several types of crib and combined crib and loose-rock dams have been constructed in the Sierras of California for the storage of water for hydraulic mining. One of the most notable of these is the Bowman dam, used for water storage by the North Bloom- field Mining Company, in California. This dam (Fig. 150) has a total height of 100 feet and uniform slopes on both faces of i on i . Its lower third on the up-stream side consists of a cribwork of logs filled with rock, the cross-section of which is i on i, w r hile the re- mainder of the dam consists of loose rock hand-placed and care- fully laid. The upper slope of the dam is sheathed with plank- ing, and the lower slope is faced with rubble masonry laid in cement. Through the bottom of the dam is an outlet culvert constructed of masonry and cement. 313. Loose-rock Dam with Masonry Retaining- walls. The best existing example of this type of construction is that closing the Castlewood reservoir in Colorado. The area of the resulting reservoir is 200 acres and its capacity 12,280 acre-feet. This dam (Fig. 151) is founded on a bed of clay and bowlders from 7 to 30 feet in depth, into which the facing wall is carried for a depth of 6 to 22 feet, and is composed of an outer shell or wall of large blocks of coarse rubble masonry, the thickness of which on the up-stream face is about 6 feet on top and 12 feet at the bottom. On the down-stream face the wall is from 5 to 7 feet in thickness, this face being laid in steps the height of which vary from ij to 2\ feet according to the dimensions of the stone blocks forming them. The main body or center of the dam consists of dry-laid rubble enclosed between these two walls. The maximum height of the dam is 63^ feet, the extreme height above the foundation being 92 feet; it is 586 feet in length on the crest, and 100 feet of this length is lowered 4 feet in order to form a wasteway over which flood waters may discharge. The LOOSE-ROCK DAM WITH MASONRY RETAINING-WALLS 395 upper 4 feet of this dam is vertical on both sides, and its top is 8 feet in width and constructed of rubble masonry in cement. At the west end of the dam is an auxiliary spillway 40 feet wide, the total wasteway capacity being 4000 second-feet. The outer slope CROSS SECTION FIG. 150. Plan and Cross-section of Bowman Dam. of the remainder of the dam is i on i, while the inner slope is 10 on i. A water cushion 200 feet long and 25 feet wide is formed at the toe by a grouted rock pavement 3 to 6 feet deep. It is doubtful if so steep a slope as 10 on i for the upper face is EARTH AND LOOSE-ROCK DAMS safe; probably 5 on i would be better, while i on i for the rear face is ample to give stability. A rectangular outlet tower having a central well 6 by 7.5 feet is built in the body of the dam, reaching to the top. In this are eight 1 2-inch outlet pipes placed at four successive levels. In such a structure as this great care should be taken to firmly found it on solid rock or on a deep bed of hard and impervious clay, while the loose-rock center should be carefully ELEVATION FIG. 151. Elevation, Plan, and Cross-section of Castlewood Dam, Colorado. laid to prevent any inclination to slide or thrust outward against the confining walls. 314. Failure and Faulty Design of Earth and Loose-rock Dams. There have been many failures of earth dams, which have been due chiefly to faulty construction and design, and not to the principle of employing earth as a material for closing storage reservoirs. It is an undoubted fact that where the con- ditions are suitable, that is, where desirable material can be obtained, an ample wasteway provided and proper foundations procured, earth furnishes under most circumstances the best material from which to construct a safe reservoir dam. Such dams (Art. 291) never fall from sliding or overturning, but always because of careless and faulty construction acting through FAILURE AND FAULTY DESIGN 397 erosion due to percolation along the outlet pipes or foundation, or along some structure within the dam, or by erosion from over- topping. There are some notable instances of large earth dams built on leaky ground which have remained intact for many years. This is the case with some great earthen dams built in California for the water-supply of San Francisco which have been in constant use for over twenty-five years. The ground at the site of one of these was full of water-bearing gravel beds and a puddle trench carried down 98 feet below the bed of the valley failed to meet an impervious stratum. Accordingly the height of the dam was reduced to 50 feet above the bed of the valley, and when the reservoir was completed springs appeared and have continued to flow harmlessly for many years. The San Leandro dam at Oakland, California, is 120 feet high above the valley-bed, and rests on leaky ground. This dam is twenty years old, and has leaked more or less around both edges, along the hillsides as well as from the bed below. The same is the case with a small old earth dam built for the water-supply of Los Angeles, California, from below which a spring of water is constantly issuing. It is evident that the upward pressure beneath these structures is not sufficient to overturn or move them. Earth dams are among the oldest structures in the world. There are many thousands of them in India, Europe, America, and elsewhere, and in the former countries some of these have been in existence for many centuries and are still as safe and substantial as when built; in fact, they have improved with age. Loose-rock dams are yet to a certain extent experimental, and while many have been constructed in the West, many have failed. The causes of failure are various, as are the modes of construction. One of the first causes of failure is an unstable foundation. It is not essential to the integrity of such a struc- ture that water shall not pass through it. It is desirable to have it water-proof, chiefly that it may hold water for storage; but if water passes through such a dam, as it may, the structure should be founded on such firm and unerodable material, and should itself have such natural slopes, that the passage of water 398 EARTH AND LOOSE-ROCK DAMS shall cause no erosion within it or about it, and therefore no settlement. Another cause of failure is to be found in such steep slopes that the loose rock will not maintain them or that waste water overtopping the structure will give it a tendency to assume natural slopes which will reduce the height of the dam and thus lead to its destruction. Unless a loose-rock dam be given such low slopes as are not likely to be changed by violent water action as ample a wasteway must be provided as for an earth or masonry dam. Without further knowledge than is now possessed as to the causes of failure in such structures and their proper design, every precaution should be taken in their construction to make them as safe against settlement by carefully building them up in horizontal layers, as secure against erosive action of water through and around them, and as free from the danger of overtopping by supplying ample wasteway, as is desirable in the construction of an earthen or a masonry dam. CHAPTER XVII MASONRY DAMS 315. Theory of Masonry Dams. Masonry dams are employed both for diversion and storage works, and may be so constructed as either to permit flood water to pass over their crests or to have it passed around one end. If the dam is to be used for storage purpose? only, and a sufficient wasteway can be provided, it may be designed according to one of the theoretical formulas or from one of the type profiles given hereafter. Dams constructed by theseformulas contain the minimum amount of material necessary to enable them to perform their functions of holding up the storage water, and are not sufficiently substantial to withstand the shock produced by water falling over their crests. Where a masonry dam is used as a diversion weir or as an overflow weir, it is im- possible to design it on any of the theoretical profiles. The chief considerations requisite in its design are that the pressure of the masonry on the foundation shall not pass the limit which the material can withstand, that its cross-section shall be more ample and substantial than that which would be required by one of the theoretical profiles, and that its lower face shall have that profile which will most facilitate the easy flow of water over its surface without the shock of actual fall. The first and most vital rule in building a masonry dam is that it shall rest on solid and practically homogeneous rock. A masonry dam is an almost absolutely rigid structure, and settle- ment in any portion of its foundation will result in cracks and ultimate rupture in its mass. There are two ways in which a masonry dam may resist the thrust of water: first, by the inertia or weight of its mass, and, second, as an arch. Its safety depends upon compliance with the conditions i. That the horizontal thrust of the water must be held in 399 400 MASONRY DAMS equilibrium by the resistance of the masonry to sliding forward or overturning; and, 2. That the pressure sustained by the masonry or its founda- tion must never exceed a certain safe limit. The thrust of the water may be resisted by being transmit- ted to the abutments, the dam acting as an arch. But three dams have as yet been built which depend in any degree for their stability on arch action, and the laws governing this action in a dam are as yet so uncertain that they cannot be depended upon with any degree of security. Some attempt at solving the rules on which a dam is dependent for its stability as an arch are given in Articles 318 and 319. According to J. B. Krantz, a dam which is curved in plan with a radius of 65 feet or less will transfer the pressure of the water to the sides of the valley whatever the height of the structure. This, however, does not lessen the effect of the weight of the masonry, so that whether the structure be curved in plan or not, its weight must be sup- ported in the same way, and the height must be such that this weight will not exceed the limit of pressure permissible on the base. In France, and in the case of the Fife dam nearPoona, India, and elsewhere, reservoir walls have been reinforced by means of masonry counterforts. If the wall is strong enough by itself the counterforts are a useless expense, and if the wall is not sufficiently strong they will not prevent it from yielding. The masonry intended for the counterforts would always be better used if spread over the mass of the dam. 316. Stability of Gravity Dams. The author will not enter into a mathematical discussion of the theory of the stability of masonry dams. This has been investigated with great thorough- ness within the past twenty-five years, and nothing which could be summarized in a work on irrigation would add to the value of the theories now held. For the benefit of students who desire to enter into the mathematics of this subject a list of authors is appended at the end of this chapter. Sufficient of the principles of the subject may be obtained from the classic works of Delocre, Krantz, Rankine, and Molesworth; or those of Baker, Fanning, Wegmann, McMasters, Church, and Mer- STABILITY OF GRAVITY DAMS 4OI riman, who are the more modern American writers on the subject. The conditions on which the stability of gravity dams are calculated are: 1. The hydrostatic principles involved in the pressure of a volume of liquid on an immersed surface; the fact that this pres- sure is perpendicular to the surface; and that for rectangular surfaces it may be considered as a single force applied below the water surface at a distance equal to of its depth. 2. That a gravity dam may fail: i, by sliding on a horizontal joint; 2, by overturning; or 3, by crushing of the masonry or foundation. The stability of the dam against its liability to destruc- tion, as enumerated in condition 2, Art. 307, must be deter- mined 1. When the reservoir is full; and, 2. When the reservoir is empty. These two conditions give the extreme positions of the lines of pressure in a dam. The first causes the maximum pressure in any horizontal plane to be at the down-stream face of the wall, and the second produces them at the up-stream face. When the reservoir is empty the wall supports only its own weight, but if the wall has a uniform thickness the pressure per square inch will be about 85 pounds if the height of the structure is 85 feet. If the faces be inclined so as to reduce the mean thick- ness, the pressure on the base diminishes and the height can be accordingly increased. From this it is clearly seen that it is absolutely necessary to widen the base of the dam by inclining its faces if the wall is to have any great height ; otherwise it would rupture from the pressure of the material composing its own mass. When the reservoir is full, however, the water contained in it bears upon the up-stream face with a pressure that increases with the square of the depth. In deep reservoirs this pressure is great, and exerts its effect in a resultant which is nearly hori- zontal in direction and carries the maximum load to the down- stream toe of the wall. For stability this resultant must pierce the base in front of this lower edge. From these considerations 26 4O2 MASONRY DAMS FIG. 152. Theoretical Triangular Cross-sec- tion of Dam. arises the necessity of giving the down-stream face a greater batter than the up-stream face. The tendency of the water pressure to produce overturning or sliding and the weight of the material are greater for each suc- cessive layer of the mass of the dam from the top downwards. As a result of this the width of the dam at the top might theoreti- cally be nil, and should be increased down- wards in such a proportion as to render the dam capable of resisting tendencies to crush- ing, sliding, and overturning. From theo- retical examinations of the effects of these forces it has been found, keeping constantly in view the necessity of making the batter of the down-stream face the greater, that the dam should have a triangular profile, some- what similar to that represented in Fig. 152. The tendency to movement in a dam under change of water pressure is about the toe and not at the center of the base. Hence the greatest stress in the structure from horizontal water pressure on the face will be parallel to and near the back face of the dam. There is far greater danger of failure from shearing or sliding on the base than from tensile strain in the upper face or from over- turning of the structure. The force tending to produce shearing or sliding increases with the square of the depth of the water, and in straight dams where tensile stress from changes of tempera- ture may exceed the strength of the masonry (Art. 3170), this source of danger is a serious one and practically limits the safe height of the structure. In high dams where the length near the base does not exceed 200 feet, the width is so great that with the ends firmly anchored in the side walls, the lower portion of the dam acts to a great degree as a horizontal beam of such magnitude that little deformation is possible from water pressure. 317. Stability against Sliding. The tendency of the water pressure to slide any portion of the dam forward on a given horizontal plane is resisted by the friction due to the weight of the mass above it. The dam is necessarily founded on firm rock, COEFFICIENTS OF FRICTION IN MASONRY 403 . the disintegrated and weaker portions of which must be removed, and as a result the base is usually sufficiently rough to offer con- siderable resistance to sliding. If this is not the case, steps must be cut for a few feet in depth in the foundation rock, or this must be irregularly cut in such manner as to leave trenches in which projections of the dam will fit. The dam, if properly constructed, is safe against any liability to slide provided its profile is such that it will resist overturning; therefore, the usual computations entered into to determine whether it will resist sliding are practi- cally unnecessary. If it be constructed of rough rubble masonry without regular beds, and so built as to form a monolithic mass, sliding is impossible. It is well known that the force required to make two pieces of smooth stone slide upon each other when dry or joined by fresh mortar is equal to about .75 of the normal pressure. Hence sliding would only be possible when the horizon- tal was equal to f of the sum of the vertical pressures. In none of the formulas or profile types ordinarily employed is the ratio of the thrust to the pressure beyond .7, while it more ordinarily ranges between .3 and .5. 318. Coefficient of Friction in Masonry. In the following table are given the coefficients of friction in dry masonry of various kinds. TABLE XXIV. COEFFICIENTS OF FRICTION IN MASONRY. Coefficient. Point-dressed granite on like granite 70 Point-dressed granite on brick 63 Point-dressed granite on smooth concrete 62 Fine-cut granite on like granite 60 Fine-cut granite on beton block 60 Dressed granite on granite with fresh mortar 50 Beton blocks on beton blocks 65 Common brick on common brick 65 Common brick on common brick with wet mortar 50 Common brick on dressed limestone 60 Dressed hard limestone on limestone 65 Dressed soft limestone on like limestone 75 According to J. T. Fanning, let S =the symbol of friction of stability; 404 MASONRY DAMS #=the horizontal water pressure resultant; c =the coefficient of friction of the given section; w = the weight of masonry above that section; e =the vertical downward water pressure resultant; z =the maximum upward water pressure resultant; d the ratio of effective upward water pressure to the maximu m. Then, when S and x are equal to each other, the wall is on the point of motion and S must be increased. This has to be done by adding more weight to the wall. This weight should be increased until it is able to resist a thrust of at least 1.5^, when S = (w + ecfz) Xc = i.$x. The wall has a small margin of fractional stability when x = 2.2$ tons. Ordinarily the weight or pressure of the wall far exceeds this figure, and is usually from 5 to 12 tons per square foot. For equilibrium, let X < CW -f W/, in which m is the cohesion of the masonry per square unit and / the length of the joint at the section above x. The value of m is so considerable that ml may be considered as a margin of safety, when we have x = cw. To find what value of c will pre- x vent sliding, we have c = . w A masonry wall must be founded upon solid rock which is either naturally uneven or must be made so, and it must be made of rubble masonry or concrete not laid in courses. As there can therefore be no smooth planes to slide one upon the other, the coefficient of friction in the mass must be many times the superincumbent weight; and we may conclude, therefore, that there is no possible danger of failure from sliding. 319. Stability against Crushing. According to the method given by Debauve, when the reservoir is full and the resultant of the pressure of the water and the weight of the masonry inter- sects the base at one-third of its width from the down-stream toe, the maximum pressure is at this toe, and is double what the pressure per square inch would be if the weight were uniformlv distributed over the whole base. When the reservoir is empty STABILITY AGAINST CRUSHING 405 the conditions are reversed, the maximum pressure being at the up-stream toe and equal to double the average pressure on the base. From this proposition Mr. James B. Francis differs. He believes that the pressures near the base of the wall are prac- tically zero, and that these pressures are transferred to the cen- tral part of the mass, where the resistance to crushing is greatest. In other words, that the masonry is not perfectly rigid, and that it becomes accordingly unnecessary to take account of crushing pressures in a dam less than 200 feet in height. In this opinion other authorities agree with Francis to a limited extent, though all prefer to calculate the limit of pressure in the usual manner, namely, to measure the pressures near the face of the wall, as that gives a safer factor, though it may be unnecessarily high. As parts of the dam are built at different times in the year and under different conditions, the structure cannot be truly homo- geneous. The absence of fractures at the thin portion near the toe of most dams indicates the absence of excessive strains at that point; it is therefore more probable that the real point of dis- tribution of pressure lies somewhere between the extremes enu- merated by Debauve and Francis. Up to the limit of 200 feet in height there is no doubt that the crushing strength of well- laid masonry need not be considered. The following, from Wegmann, is a brief synopsis of a simple formula for finding the distribution of pressure at any point in a dam: Let W = the total pressure on the base; u =the distance of W from the nearest edge; p =the maximum pressure on the foundation; q =the minimum pressure on the foundation; / =the length of the joint or base under consideration. 2W f T>U \ I Then p = ~7~\ 2 V J- When u = -, or in other words the o 2W pressure is within the middle third of the base, p = r~. If the pressure is without the middle third there will be tension in 406 MASONRY DAMS the mass. As it is unsafe to depend on the tension in masonry, it would be best to neglect this in calculating the pressure on the 2\ foundation, and this will become p = . Another simple 3 u formula for determining the pressure on the base, and one which leads to practically similar results, is the following, given by Ira O. Baker: W 6Wu f= "~l J~ 320. Limiting Pressures. The limiting pressures which it may be safe to permit in masonry differ considerably accord- ing to various authorities. From actual tests these pressures differ according to the dimensions of the masonry blocks, and it is probable that much greater pressures can be sustained per unit of area in the interior of large masses than in the smaller experimental blocks or near the surface of the mass. The fol- lowing pressures are ordinarily accepted: Brick, 120 pounds; sandstone, 130 pounds; limestone, 152 pounds; granite, 155 pounds per square inch. It is not advisable to allow either a direct or resultant pressure exceeding 140 pounds per square inch within i foot of the face of rubble masonry or exceeding 200 pounds per square inch in the heart of the work. On some of the great structures already built limits of pressure as low as 85 pounds have been adhered to, while pressures exceeding 200 pounds per square inch have been permitted in the Almanza and the Gros Bois dams in Europe. Among the great dams which have been constructed the pressures vary between 5.8 tons per square foot in the Verdon dam in France and 14.6 tons per square foot in the Gros Bois dam, while the proposed Quaker Bridge dam, in New York, was designed for a maximum pressure of 16.6 tons per square foot. It is probable, however, that a safe average limit is that already given of from 140 to 200 pounds per square inch. 321. Stability against Overturning. To insure ample safety against all the causes of failure in a dam in addition to the other conditions already fixed, the lines of pressure must lie within STABILITY AGAINST OVERTURNING 407 the center third of the profile, whether the reservoir be full or empty. This last condition precludes the possibility of tension, and insures a factor of safety of at least two against overturning. In Fig. 1 53 suppose the lines of reaction R and W to intersect the joint / at the limit of its center third. Taking the moments of the three forces H, R, and W, which are in equilibrium at about the point e, we find - , in which d=ihc depth of / O water at the joint above the plane of /. If the moments are taken about the front edge a, the lever arm of W will be double, while that of H remains unchanged ; the factor of safety against over- H I I/ i W FIG. 153. Diagram Illustrating Wegmann's Formula. turning is therefore two. It is equally evident that if the line of reaction of W or R should intersect / within its center third, the factor of stability would be greater than two. The following formulas are taken from the treatise of Edward Wegmann, Jr., on Masonry Dams, because the author considers them simple and accurate. For their deduction and discussion the student should refer to this work. The mass of the cross- section of the dam should be rectangular and will contain an excess of material as regards resistance to the hydrostatic pres- sure of the water; P f will pass through the center of the rectangle, and P will gradually approach the front face eventually reach- ing some joint x = a, where u = . The depth of this joint below o the top of the dam is d = a\/r, where P =the line of pressure, reservoir full; P' = the line of pressure, reservoir empty; 408 MASONRY DAMS x =the unknown length of the joint; u =the distance of P from the front edge of the joint x; a =the top width of the dam; d =the depth of water at the joint x; r =the specific gravity of the masonry. For the next course below the joint x y where the dam begins to assume a trapezoidal cross-section, we have ?, .... (2) in which w = the total weight of masonry resting on the joint /; / =the known length of the joint above x; h = the depth of a course of masonry assumed as 10 feet; w = the distance of P' from the back edge of the joint /; d s M = = the moment of H on the joint x; 6r ff H = = the horizontal thrust of the water. 2r Equation (2) may be used for a series of joints down to a depth where the back surface of the dam begins to slope or until /Y* a joint is found where n = ; n being the distance of P' from o the back edge of the joint x. For the next course both faces sy* will have to be sloped, and u = n t when we obtain o 6M In applying equation (3) for finding the value of x, the maxi- mum pressure must be obtained both with reservoir full and empty. This may be done by the formula 6M **=, ... ... - (4) in which p= the limiting pressure per square foot at the front face of the dam. This equation may be employed until the limiting pressure is reached at the back face, when the following formula must be used: MOLESWORTH'S FORMULA AND PROFILE TYPE 409 . . (5) in which q is equal to the limiting pressure per square foot at the back face of the dam, and is generally assumed to be greater than p. These equations give the successive lengths of the joints, but do not give their position. This may be found by deter- mining the value of y= the batter of the back face; the formula being 2W ( x - 3 m)-h? 6w + h(2l + x) ' and for equation (5), lh(xl) + x 2 (hq) h(2l + x) The theoretical profile resulting from calculating the dam by the above formula will have polygonal faces. It only be- comes necessary then to make the value of h sufficiently small to determine a profile with a smooth surface which will fulfil all of the conditions. 322. Molesworth's Formula and Profile Type. Mr. Guil- ford L. Molesworth has worked out the following formula, the application of which gives the profile shown in Fig. 154: This formula gives a dam of excellent cross-section nearly ap- proaching that gotten by Wegmann's and others, and one in which the resultants of pressures, reservoir full and empty, lie well within the middle third. The computations by this formula are simple, and for that reason it is given here. 3> = the distance measured along any point in the masonry from the down-stream face to a vertical line drawn from the top front edge of the dam to the base; 2 = the corresponding distance on the same joint to the up- stream face; # = the distance from the top of the dam to the joint above mentioned ; 4 io MASONRY DAMS y = .6oc as a minimum; r = the limit of pressure of the masonry in tons per square foot ; H = the minimum height of dam in feet; TT a = y at from the top; 4 b = top width = -. 323. Height and Top Width of Dam. As far as the forces already considered are concerned, the top width of the dam might be zero and the water might rise to its crest. In practice a certain definite top width must be given in order to enable the dam to withstand the shock of waves and ice, and the top of the dam must be continued above the maximum flood-water line for a sufficient height to prevent its being topped by waves. Ordinarily the top width of the dam should be sufficient to enable it to act as a road- way and afford communication between the two slopes of the valley. It should never be less than 5 or 6 feet, and for the highest dams need never exceed 15 feet, varying between these according to the height of the wall. Having calculated the height of the dam for maximum flood heights of water, this should be continued upward a sufficient amount to insure it against being topped by the waves. The height of waves depends on complex causes, chiefly on the depth of the reservoir and the fetch, a formula for computing which was given in Article 305. The maximum amount to which it will be necessary to increase the computed height of the dam need rarely or never exceed 10 feet, its minimum being as low as one foot in an extremely shallow and small reservoir. On top of the crown of the dam there should always be a parapet as an additional precaution against its being topped by waves, and this parapet may be from 3 to 5 feet in height. 324. Profile of Dam. In Fig. 155 is given a comparison of the profiles obtained by several of the more common formulas, while that which is shown in full lines is the practical profile type No. 3, adopted by Wegmann. In the table on the oppo- site page are given the dimensions and pressures for this profile STABILITY AGAINST UPWARD WATER PRESSURE 411 type. The specific gravity of the masonry employed in making these computations is assumed at 2\. 325. Stability against Upward Water Pressure; also Causes of Failure. The question of the effect of springs under founda- tions of masonry dams is still an open one, and has led to much discussion among the more experienced builders of such struc- '.so x- 9 . z _ /.ooa?\* ; . a = y a t ^-; 6 - .4 a *, y - 0.6 X as a minimum; H Height of dam in feet; X s * Depth in feet of any horizontal plane below >rW.L, Offset in feet from vertical line, A-A to outer face of dam at any depth X ; Z = Offset to inner face ; b = Width in feet of dam at top; Limit of pressure in tons per square foot; 7.492-I 38.02 " JSO Scaled FIG. 154. Molesworth's Profile Type. tures. A cross-section which would enable a dam to resist up- ward water-pressure should be much heavier than one called for by the usually accepted theories which disregard such pressure. It would, in fact, be nearly twice as heavy, and therefore call for about twice as much masonry in the structure as would the theo- retical cross-section. All the evidence appears to be against danger of rupture from such causes. There have been con- structed and are still standing many masonry dams designed on 412 MASONRY DAMS cross-sections too light to withstand theoretical pressures from below, and of all these structures but three of any moment have failed, namely, the Puentes, Habra, and Bouzey dams; and the causes of failure of each of these has been due to faulty con- struction rather than to errors in not designing an ample profile for withstanding upward pressure. In a recent discussion of this Scale of Feet \ 5 10 20 30 40 50 60 70 Delocre's Type Kankine's " Krantz's ft ~ Crugnola's " Quaker Bridge Dam Wegmanri's Type Krantz- Delocre Crugnola QuakerJridge Dam \ v \ FIG. 155. Comparison of Profile Types. subject before the American Society of Civil Engineers Mr. Weg- mann enumerates the causes of failure in these three structures as follows : The Puentes dam, built in Spain a century ago, was 164 feet high. During construction a deep pocket of earth was discov- STABILITY AGAINST UPWARD WATER PRESSURE 413 p aoj Aaessaa uoi} -ouj jo SOPO^POO to O HI CS PO PC PO PO PO M M Q OOO to HI (s pr> rf to 10 toO OOOOOOOOO to w-,O dddo'ooooooooooooooooo !/3 O c o O O 8 HI O 00 00 O toO ^- W 00 to PO -tOO -. N PO t^oo to -t O N O O t--O tooO o N HI -too to PO PO OO r>O '^'tO HI o POHI rj-w\o t^.to?s o^^ j auiq jo luojj iuoaj aouB^stQ S.S8.: 100 r^oo O HI p<-> 10 2 13 jj"a .a rt t 4_> W rf rt\O O N to ^QO OOO OO HI roioON OO O t^OO r^ t^co 10 to o HI o tooo to t^ OO oo r H, \o r^oo O oo 00 oo O 't OO N OO 5fMMM^fOOQ MMMNPINCO^-^- IOO t^.00 OO HI N T510I^O t^* O ^O *"** Q *o | ^ ^O w r^-vO 10 f^ d 00 ro t^ - NO O t^ r^oo OO "-" ^ t^ O O M w fO ^t io>O r^ M -O O u^ toM OOOOO IOO t^OM to too r t^oo o O M N PC too O O 1 - ^ ^O ^t 1 O O ^t" ^ O ^^O ^O O ^t" ^" ^O ^ ^ ^O O^OMOQwcxJOOO'-'i-.oO'-'OOOOO^'-'OO'-'OOOO M T^OO to ^^O w M *o ^O^O ^O *^ w O N O s M M w to to *"* O^ ^ to O" ^t* O^ to w oO t*^* JO ^93^ iqn3 ui aa^B^V. jo -3-H, M -to __. ._ _ PO ^ O'OO w O 1 ^ ^^ 00 OO ^O fOS O ^ t^ M ID O ^ ^^ 00 ^t* *^ s *>* MMMCiWrOfOrfTt ioO ^O f^-C jo do^ M.O\ -aq ja^B^i jo 414 MASONRY DAMS ered under the foundation, and instead of going down to solid rock a pile foundation was employed in this place. This was forced outward by water-pressure and caused a rupture in the cement portion of the dam. The Habra dam, constructed twenty-five years ago, failed through the poor material used in its construction. This consisted of porous sandstone not of uniform character, while the sand used in the cement was of poor quality; the hydraulic lime was made of calcareous stone of imperfect quality containing quicklime, which possibly ex- panded, and thus assisted in making the structure porous. The dam was not water-tight, for water flowed through it like a sieve, until finally a severe rain-storm caused the structure to be overtopped by a flood 13 feet in height above the crest, which resulted in its destruction. The Bouzey dam was completed ten years ago and was founded on porous conglomerate rock; consisting of siliceous stones joined together by poor cement material. The foundation was not carried down to solid rock, and to prevent leakage under the dam a guard-wall 6J feet thick was carried below the main structure for a depth of 20 or 30 feet to solid rock. As the maximum height of water in the reservoir was to be 75 feet, this guard-wall could scarcely be expected to prevent water from percolating under the dam, and thus cause sufficient upward pressure to injure its stability by sliding. The structure was finally ruptured, not by settling or overturning, but by sliding or bulging forward, which produced numerous fissures in the foundation and four vertical fissures in the wall. In this latter case upward pressure under the base caused the disaster, but this doubtless would not have occurred had the whole dam been founded on solid rock, as should have been the case. In the construction of most masonry dams fissures are en- countered in the foundation rock from which water issues or is expected to issue under pressure. These should invariably be carefully examined, cleaned out, and followed down to such a depth as to reach homogeneous rock, or, after being cleaned out for a considerable depth, should be gradually narrowed up with cement so as to coax leakage water to a small orifice, which STABILITY AGAINST TEMPERATURE CHANGES 415 may terminate in a tube and be led out of the structure or be capped and bottled. 326. Stability against Temperature Changes. Mr. George Y. Wisner has called attention to the fact that strains arising from changes in temperature in straight dams are sometimes enormous and must be provided against with large coefficients of safety. The base of a dam, being massive and generally submerged in water, has much less range of temperature than the upper por- tions of the structure, where it may exceed 100 degrees F. The expansion of sandstone for 100 degrees change of temperature is about i inch in 100 feet, of limestone about i inch in 125 feet, of granite about i inch in 1 70 feet, and of masonry and concrete may average i inch in 125 feet. A dam 500 feet long in pass- ing through a change of 100 degrees temperature will expand or contract about 4 inches in its entire length, and will subject the upper portion of the wall to greater strains than those due to water pressure and weight of dam. A drop of 20 degrees of temperature at the crest of the dam may cause a tensile strain of 40 tons per square foot, and unless the dam were supported by arch construction, it would be left with only its resistance to shearing and sliding to withstand the water pressure. Mr. Wisner observes that if the upper portion of the dam be constructed during a period of warm weather, the arch will be under tension during the cooler portions of the year and a large portion of the pressure from the water will be transmitted to the toe of the dam. On the other hand, if the walls be con- structed in cool weather, the arch will be under compression most of the time, and the water pressure will be transmitted directly to the side walls by the arch. In most cases for curved dams of less than 500 feet length on the crest, the cross -sect ion necessary to keep pressure on the foundation within sufficient limits is ample to withstand shearing stress from water pressure, thus making the curved type of dam for the same stability much more economical than that of gravity section. 327. Curved Masonry Dams. A dam of the kind already considered is of the pure gravity type and relies for its stability solely on the weight of the masonry and its friction. A dam 4T6 MASONRY DAMS of the pure arched type relies solely on the arched form for sta- bility, in which case the pressure of the water is transmitted laterally to the abutments. If our knowledge of the laws govern- ing masonry arches were more complete, the arched or curved dam would probably be the best type, since it will contain the least amount of material. As it is, we know something of the laws governing such true masonry arches as those supporting bridges. In these the two extremities of the arch are raised at their springing on some firm abutment and the whole is keyed together at the center; but in a masonry dam of arched form not only is the arch supposed to transmit the pressures laterally to the side of the abutments, but as the dam rests on the bottom of the valley it is sustained again at that point, so that it cannot act as a true arch, nearly perfect arch action only occurring at the top, where the pressure is a minimum, while near the bottom, where the pressure is greatest, probably very little of this is trans- mitted to the abutments. For this reason it is not yet considered safe to build a dam depending purely on the arched form, and such few dams as have been constructed on this principle have been given somewhat of the gravity cross-section, increasing downward in width, so that they presumably resist the pressure both by gravity and arched action. The best existing types of such works are the Zola dam in France, the Shoshone and Path- finder dams, Wyoming, and the Bear Valley and Sweetwater dams in California (Arts. 352,361, and 362). That a masonry dam constructed across a narrow valley can resist the water-pressure by transmitting it to its abutments is proved by the dams above cited. The question then arises, can the profile be reduced from what would be required if the plan was straight? As stated at the beginning of this chapter, Krantz asserts that a dam curved in plan and convexed up- stream with a radius 65 feet or less will transfer the pressure of the water to its abutments. Dams, however, of even greater radius than this do transfer the pressure to the abutments. The radius of the Zola dam is 158 feet and its length on top is 205 feet. The length of the Bear Valley dam, which depends almost wholly on its arched form for its stability, is 230 feet, the radius CURVED MASONRY DAMS 417 at the top being 335 feet and at the bottom 226 feet. The Sweet- water dam is 380 feet in length on top, its radius at the same point being 222 feet. The Shoshone dam is 200 feet in length on top, the radius of curvature of its center line being 150 feet. M. Delo- cre says that a curved dam will act as an arch if its thickness does SCALE OP OS 10 15 ?0 * 3 - . aj.od...... 3?.?3 FIG. 156. Practical Profile from Wegmann. 200 not exceed one-third of the radius of its up-stream or convex side. M. Pelletreau fixes the limiting value of the thickness at one-half of this radius. When a dam acts as an arch it only transmits the water-pressure to the sides of the valley; its own weight must still be borne by the foundation. 27 41 8 MASONRY DAMS 328. Design of Curved Dams. Mr. Wegmann gives the following formula for calculating the thrust in curved dams of circular plan : t = pr, in which t = the uniform thrust in the circular rings of any plane of the masonry; p = the pressure per unit of length of this section of the ring; r =the radius of the rings of the outer surface. Arch action can only take place by the elastic yield of the masonry; but little is known of the elasticity of brick, stone, etc., and nothing of the elasticity of masonry; hence it is impossible to determine the amount of the arch action. It may be shown theoretically that in the case of a narrow valley a profile of less area may be employed for a dam which is curved in plan than for one in which the plan is straight. An excellent theoretical discussion of this subject has been pub- lished by Messrs. Hubert Vischer and Luther Wagoner. The result of the investigations of these gentlemen goes to show that arch action, as usually understood, adds little to the strength of a curved dam. Notwithstanding this, the curved form may to a marked degree afford additional resistance, and this in a manner less dependent on the radius of the curve than the arched theory implies. The general conclusion reached by these gentle- men is, further, that the rate of efficiency of a curved dam over the straight decreases with the increased length of the dam; that very narrow cross-sections are not justifiable; and they ascribe the high duty of the Bear Valley dam to a favorable com- bination of conditions which could not have held good if the span had been considerably longer or the workmanship less excellent. Engineers are now fully agreed upon the advantages of the curved plan. Its chief disadvantage is the increased length of the dam over a straight plan, and the consequent increase in the amount and cost of material to within certain limits of top length and radius. Though the cross-section of a curved dam may unquestionably be somewhat reduced, it would be unsafe to DESIGN OF CURVED DAMS 419 reduce it as much as has been done in the case of the Bear Valley and Zola dams, without adding metal reinforcement, though these have withstood securely the pressures brought against them. It might with safety be reduced under favorable conditions to the dimensions of the Sweetwater, or Shoshone dams, thus saving largely in the amount of material employed. All of the more conservative writers, as Wegmann, Rankine, and Krantz, recom- mend that the design of the profile be made sufficiently strong to enable the wall to resist water pressure simply by its weight, and to curve the plan as an additional safeguard whenever the topography makes it advisable. American engineers, and es- pecially those of the West, however, are prone to be more liberal ; and the tendency is toward a slight reduction in the cross-section where a curved plan is practicable, as shown in the great dams of the Reclamation Service. An additional advantage of the arched form of dam is that pressure of the water on the back of the arch is perpendicular to the up-stream face, and is decomposed into two components, one perpendicular to the span of the arch and the other parallel, to it. The first is resisted by the gravity and arch stability, and the second thrusts the up-stream face into compression, which has a tendency to close all vertical cracks and to consolidate the masonry transversely. An excellent manner in which to increase the efficiency of the arch action in a curved dam is that employed in the Sweet- water dam, in California. This consists in reducing the radius of curvature from the center towards the abutments. The good effect of this is to widen the base or spring of the arch at the abut- ments, thus giving a broader bearing for the arch on the hillsides. In the Sweetwater dam the effect of this is seen in projections or rectangular offsets made on the down-stream face of the dam (PI. XXVII), the center of the dam sloping evenly, while the surface is broken by steps where it abuts against the hillside. The best materials for a dam of curved type is probably a wall having a face of first-class masonry with center filling of con- crete and large rock. Such a dam will consist practically of two concentric arches capable of withstanding heavy pressures, connected by a water-tight concrete core, having a lower modulus 420 MASONRY DAMS of elasticity. In the case of high dams of considerable length, the use of railroad iron in the upper portion of the structure may " prevent temperature cracks. Construction when temperatures are below normal, thus insuring compressive strains most of the time, will have a similar effect. 329. Wide-crested or Overfall Dams. Gravity dams (Art. 316) are designed with cross-sections sufficiently ample to enable them to resist by their weight the hydrostatic forces which tend to overturn or slide them. Curved dams (Art. 327) are designed to resist the same forces, but their weight is aided in that effort by curving them in plan in such manner as to add to their stability by bringing into play arch action. They are sometimes accordingly diminished in cross-section from gravity requirements. Overfall dams have to resist, in addition to the hydrostatic forces tending to shear or overturn them, the dy- namic and erosive action due to having large volumes of water pour over them, often from great heights. Their cross-sections must therefore be increased over those called for by gravity requirements by an amount sufficient to enable them to resist the pounding and erosive action of the falling water. This re- sult is usually aided by diminishing these forces to some extent by giving their lower slopes such rollerway curves (Art. 176) as will cause the water to slide or roll down them rather than fall and be broken up on them; also, by diminishing the effective height of overfall by water-cushions, as is done for weirs (Art. 177). An overfall dam therefore has to withstand greater destruc- tive forces than any other type, and should accordingly be con- structed of even better materials, with greater care, and be if possible more firmly founded than a simple gravity dam of cor- responding height. The cross-sections of existing overfall dams exhibit on the one hand the conservatively massive English type illustrated by the Vyrnwy dam (Fig. 168), and on the other the bold Western type illustrated by the La Grange dam (Fig. 171) which is scarcely heavier than gravity alone would require. In both of these examples well-designed rollerway curves and deep water-cushions greatly reduce the erosive effect of the falling DESIGN OF OVERFALL DAMS 421 water. Between these extremes the Folsom dam (PL XXXI) is amply heavy and has a good lower curve, but too wide and sharp a crest to produce the best results. The Betwa dam (Fig. 170), while having a cross-section at variance with the theoretic demands upon it, is made very heavy, with a massive buttress below to reinforce it. The form of overfall given the new Croton weir (Fig. 165) is more nearly that required by theory, but the advisability of breaking its lower face up into steps is doubtful, for this prevents its rollerway curve from causing the water to slide gently down it, while it induces a strong erosive action on the face of the dam, though it reduces the action at the toe. Probably the best cross-section yet given an overfall dam is that given the Spier Falls dam (Fig. 173), and the McCall's Ferry dam, the curves of the lower faces of which are such as to aid best in producing a sliding motion in the falling water, while the crest width is neither too great nor too little. 330. Design of Overfall Dams. As yet theory has made little advance in solving the proper cross-section for overfall dams. We believe that they should be somewhat more mas- sive than gravity sections, and that their lower slopes should be so modified as either to cause the water to slide, as in the Colorado River dam, or fall clear of the base, as in the Betwa dam. We know that the provision of a water-cushion tends materially to reduce the erosive and dynamic action of the fall- ing water by reducing the height of fall. On the other hand, the form of the crest and that of the lower slope are still points of difference among hydraulic engineers. There are those who favor a very wide crest with a sharp lower edge as giving the proper direction to a body of falling water; there are others who favor the curved crest and lower face; and still others who advocate the stepped outer slope. Again, instances are not lacking in which an unprecedented flood has proven too great for the wasteway of a simple gravity dam, and large volumes of water have passed harmlessly over its crest. This has happened during construction to the Bhatgur, Tansa, and, in our own country, to the San Mateo dams; while since completion the more frail Sweetwater curved dam, and 422 MASONRY DAMS lightest of all the Bear Valley dam, have been harmlessly topped by flood -waters. To assume from this, however, that such sections are sufficiently substantial for overfall dams would be unsafe, and no careful engineer will intentionally tempt fate as yet by adopting them for overfall dams. Again, each case will require special treatment and its own dimensions, according as the dam is to be topped by a few feet of water, as in the Croton overfall weirs, or by a flood which banks up 30 feet above the crest, as with the Folsom dam. One of the simplest problems connected with the design of wide-crested overfall dams is the determination of the velocity and discharge for a given depth of water passing over the crest, yet the theoretic determination of these quantities is one of the most difficult problems of solution, since it is affected by the curves at both the upper and lower edges of the crest as well as by the crest width. The crest velocity may be accepted as being due to the differences in head over the dam crest between still water above the dam and high-water surface over the crest. Thus (Fig. 157), v is dependent on H h, and may be expressed ^), (i) and for discharge per unit of length in second-feet -h), .... (2) <2 = o when h = o or h = H. In formula (2) the discharge Q is a maximum when H = $/2h; therefore, for maximum dis- charge, ...... (3) in which B = width of crest, agrees very closely with the results obtained from experiment. A rounded inner edge to the crest prevents crest contrac- tions and increases the discharge greatly in proportion to the degree of rounding. The same effect is produced by curving the outer edge, the tendency of which is to diminish the width of the dam crest and to make it to conform more nearly to the dis- charge which would be gotten from a knife-edge weir. Width of crest and degree of rounding will affect accordingly the velocity DESIGN OF OVERFALL DAMS 423 and discharge, and will determine how far out over the weir crest the column of water will fall for a given height. Thus a very sharp crest well rounded on the outer face will cause the water to flow or slide down this face and alight upon it well within the toe; a broader crest less curved will throw the water k Jfc: FIG. 157. Flow Over Wide-crested Dam. further out and make it alight nearer the toe, thus jarring the structure; while a very wide crest with sharp outer edge may throw the water out entirely clear of the dam. Francis' formula of flow for a sharp-edged weir crest (Art. 90), that is, one in which B equals zero, gives Q = 3 .goHVW. (4) If the crest is very wide, and there be practically no curve at either edge, the stream assumes a rectilinear direction, so that the formula for maximum flow in a canal applies, or Q = 2. 9 2HVlT, (5) which will not apply for crest widths B less than 3.5^. Accord- ingly, for intermediate widths, the constants in formulas (4) and (5) will have values intermediate between those there given (Art. 368). The pressure against the back of the surcharged masonry dam, or spillway, is represented by P = d(2H + d) 3 i.2$, (6) in which P is the pressure and d the total depth of water above inner foot of dam. The center of pressure g is on the line pass- ing through the center of gravity of the prism of water pressing against the upper face of the dam, and is 424 MASONRY DAMS 2H+d The point of application of the overturning moment M about the outer toe is the product of (6) and (7), and is M = io.42d 2 (sH + d) ..... (8) 331. Foundations. Masonry dams must be founded on solid rock, and great care and judgment are required in deter- mining just when the excavation for the foundation has pro- ceeded sufficiently far. If the looser and partially decomposed surface rock is not entirely removed there is danger of leakage under the dam, and consequent liability of its destruction. If the excavation is carried too far into the underlying rock much money may be wasted. Frequent cases might be cited where it has been found necessary to make unusually deep excavations in order that a sufficiently firm foundation might be reached. In the case of the Turlock dam the average depth of excavation in the large bowlders and underlying porphyry was from 5 to 10 feet to the homogeneous material. In one or two cases, how- ever, seams full of huge bowlders weighing several hundred tons apiece were encountered, which necessitated excavation to a depth of 25 to 35 feet in order that they might be worked out and homogeneous rock reached. A masonry dam is an abso- lutely rigid structure, and the least unequal settlement in any portion of it tends to produce a crack. A clay or hardpan foun- dation is almost sure to yield under the weight of a masonry dam, and be the loose material ever so little in amount, if it offers opportunity for subsidence it will result in the rupture of the dam. The safe load on the lower courses of a masonry dam depends on the character of the material of which it is com- posed, and may reach from 10 to 15 tons per square foot, and nothing but the most substantial rock will bear such a weight as this. 332. Preparing Foundation. After the foundation of a masonry dam has been excavated down to a solid or homo- geneous rock the greatest care should be taken in properly clean- ing it and roughing its surface in order to make a most perfect PREPARING FOUNDATION 425 bond with the masonry superstructure. Perhaps the best way of describing the care to be taken in these particulars is by re- hearsing the account given by Mr. Walter McCulloh, detailing the excavation for the foundation for the Sodom dam of the Croton water supply. The rock of the foundation was rotten, disintegrated, and shaly for a depth of from 4 to 15 feet. In preparing the foun- dation, drilling was done by steam and hand, and light charges of 40 to 60 per cent dynamite used in blasting until the rock appeared firm. Then all seams and fissures were followed up with block-hole and black-powder blasting, and by barring out until a solid and practically tight bottom was secured. The foundation thus prepared was swept clean with wire stable brooms and washed thoroughly with streams from hose-pipes. In the process of washing it may be stated that streams under high pressure are desirable in order to remove every particle of loose material, and the use of hot water or steam is found to facilitate the cleansing of the foundation. When the bottom of the foundation for the Sodom dam was ready, all pockets, holes, and seams were filled with rich Port- land-cement concrete, forming a series of level beds on which to build up the rubble superstructure. The use of concrete beds was discontinued later, as it was found that a tighter bed could be formed with rubble and small stones. A large amount of water made its way through the loose rock above the bottom, and in some cases through seams in the bottom itself, but generally where the rock appeared solid the seams were not followed any deeper. Springs washed the mortar out of the concrete, but in making the rubble beds the water was led around and pre- vented from doing damage, by forcing the streams from place to place, until finally a small well 2 feet in diameter and from i to 2 feet deep would be formed about the place where the water boiled up. When the mortar about each well was thoroughly set, it was bailed out and quickly filled with dry mortar, and on top of this a large stone would be placed, and the spring was effectually bottled. This same process was followed over the entire bottom wherever water had to be contended with, and 426 MASONRY DAMS after the first 6 feet of rubble foundation was laid no difficulty was experienced. To assure no shattering of the foundation rock from blast- ing at the Olive Bridge dam site, Esopus creek, N. Y., both faces of the foundation curtain-wall were first channelled, and the intermediate rock then blown out with black powder. This curtain- wall was sunk 20 feet below the level of the founda- tion proper and is 20 feet wide, to assure good bond and cut off seepage. The foundation was explored with drill holes in which water was forced and all seams in the rock thus located were closed with grout pumped in under pressure. Plate XXIV illustrates admirably the great depth to which foundations are sometimes carried. This shows the founda- tion of the gate chambers of the new Croton Aqueduct at Cornell's, which extend in places to a depth as great as 80 feet below the level of the river-bed. 333. Material of which Constructed. Masonry reservoir dams may be built of cut ashlar stone; of rubble; of concrete with or without dressed-stone facing; or of random rubble stone. The first is best on account of its strength, but while only twice as strong as rubble, it costs three or four times as much. As the form of the upper part of the dam depends on the positions of the lines of pressure and not on the strain in the masonry, the great strength of cut-stone work would only avail in the lower portion of the dam. Great care would have to be employed in the use of cut masonry in order that it should not be laid in hori- zontal beds, which might permit of shearing or sliding, and in order that it should break joints with a proper degree of irregular- ity. Neither the vertical nor the horizontal joints in a dam should be continuous, but should be carefully broken. Rubble or concrete with cut-stone facing is not a desirable material of which to construct a dam, because of the difference in settling of the two kinds of masonry, which might result in the formation of cracks and seams. Where the facing becomes detached in this manner from the remainder of the body of the wall the strength of the structure is reduced to that of the un- coursed or concrete center. The most prominent examples of PLATE XXIV. Excavating Foundation for New Croton Dam and Gate-house. 428 MASONRY DAMS the use of cut-stone facing with rubble or concrete interior are to be found in the Vir, Bhatgur, and Betwa dams of India, which are briefly described in Articles 346 and 355, and the new Croton dam in New York (Art. 347). In each of these the cut stone is laid as headers and stretchers, and the former are well bonded into the mass of the dam. 334. Concrete. Concrete has been successfully employed in five of the greatest dams yet constructed, namely, the San Mateo dam in California, 170 feet in height; the Periar dam in India, (Art. 348), 155 feet high; in the Geelong and Beetaloo dams in Australia, respectively 60 and no feet in height (Article 349), and in the McCalPs Ferry dam, the greatest of overfall masonry dams, 60 feet high. The Periar and Beetaloo dams are two of the best examples of the homogeneous use of concrete. The great dis- advantage in using this material, aside from engineering considera- tions, is the added cost of cement where the latter is expensive. The great advantage of the use of concrete is the saving effected in labor and the speed of construction; for concrete can be mixed and handled entirely by machinery worked by water-power. In the Beetaloo dam for 46 feet above the foundation the concrete was made of i part Portland cement, 2 parts washed sand, and 4 parts broken stone of 2 -inch gauge. In the McCall's Ferry dam the proportions were i cement, 3 sand, and 5 broken stone of sizes up to 5 inches. This concrete was laid so wet as to require no tamping. In building such structures great care is taken to have the surface of the set concrete picked, washed, and brushed before a fresh layer is deposited, and large projecting stones are left to assist the bond. Beetaloo dam was built up as a monolithic mass, the concrete being laid between boards or framing bolted in the body of the dam. The concrete for McCall's Ferry dam was laid in movable steel forms of wooden lagging boxes between frameso Concrete is little more than uncoursed rubble reduced to its simplest form. As regards resistance to crushing or percola- tion the value of the two materials is almost identical, unless it be considered as a point in favor of concrete that it must be solid, while rubble may, if the supervision be defective, contain void CONCRETE 429 spaces not filled with mortar. The selection between the two depends entirely on their relative cost. The San Mateo dam in California was not built up as a mono- lithic mass of concrete as were those just described, but is com- posed of great concrete blocks of uniformly irregular dimensions. These blocks (PL XXIV) weigh about 300 tons each, and were built up in the body of the dam in such manner as to key in with each other both in horizontal and vertical plan, so as to produce a nearly homogeneous mass and create the greatest amount of friction between blocks. The material was mixed at -Double Lacing Bar. This Furring Piece to t 1,12'C ; 15 It*, with Back, turned toward* Maaoory SIDE ELEVATION FIG. 158. Steel Forms. McCall's Ferry Dam, Susquehanna River, Perm. the site of the dam, and run out in a tramway and built in place inside of a wooden boxing which was afterwards removed. The blocks were left surrounded by the boxing for one week, during which time they set sufficiently for the wood to be removed and to permit of other blocks being built against them. The concrete consisted of 2 -inch gauge metal mixed in the proportion of 6 of broken stone to 2 of sand and i of Portland cement. Concrete should be laid immediately after mixing, and should 43 MASONRY DAMS be thoroughly rammed and compacted until the water flushes to the surface. It should be allowed to set for 12 hours or more before any further work is laid upon it. 335. Rubble Masonry. Rough random rubble masonry is perhaps the best material that can be used for building a dam. It possesses strength, can be readily adapted to any form of profile, and is relatively cheap. In building a dam the main object is to form as nearly homogeneous a monolithic mass as possible. Horizontal and vertical courses must therefore be avoided, and the stones interlocked in all directions. The sizes of these stones may differ greatly. The mass of the wall may be composed of stones of such a size as may be carried between two men, as is the case in India, where machinery is rarely em- ployed; or it may consist of cyclopean rubble measuring from one to several cubic yards in volume, each block perhaps weighing several tons, as in the Spier Falls dam. To prevent leakage, all spaces between the stones must be completely and compactly filled with impervious mortar or cement. To prevent sliding, the blocks must be irregularly bedded, and as each course is laid a large proportion of the stones must be permitted to project above the general surface. The spaces between the larger stones may be filled with concrete or small rubble. This practice of imbedding cyclopean rubble in concrete is becoming increasingly popular. Grouting must never be permitted, and the best stones are gener- ally reserved for the facing, in which they are laid as headers in such manner as to give an even contour to the outer surface. 336. Cement. The center of a large work may be of some cheaper variety of cement, as Rosendale or other natural cement. Portland cement should be used in the facing stones and in point- ing. All cement used should be hydraulic and of some well- known brand, whether natural or Portland. The cement should be carefully stored in a tight shed with a close floor set above the ground to protect it against dampness, and should be subjected to strict inspection and tests. All mortar used should be prepared from the best quality of cement of the kind above described, and of clean sharp river sand well washed and free from dirt. They should be mixed dry in the proper proportions, and then a mod- DETAILS OF CONSTRUCTION 431 erate amount of water should be added and the whole thoroughly worked together. Portland cement mortar should generally be mixed in the proportion of about i of cement to 2 of sand in laying the puddle work; while for laying the rubble work and concrete i of cement to 3 of sand may be used. In laying masonry great care should be taken that water shall not interfere, and in no case should it be laid in water. 337. Details of Construction. Rubble stone masonry should always be made of sound clean stone, of suitable size, quality, and shape for the work. All awkward projections should be hammered off so that the stones shall become rectangular in form. Their beds should present such even surfaces that when the stones are lowered on the surface prepared to receive them the mortar will fill all spaces. The stones should be well rammed into the bed of mortar if they axe light, and this should be at least one inch in thickness. Where large stones are employed a moder- ate quantity of spawls may be used in the preparation of suitable surfaces for receiving them. Especial care must be taken to have beds and joints full of mortar, as no grouting or filling of joints should be allowed after the stones are placed. The work must be thoroughly bonded, and if mortar joints are not full and flush they should be taken out to a depth of several inches and properly re- pointed. In such work various sizes of stones should be employed and regular coursing should be avoided in order to obtain both vertical and horizontal bonding. The sizes of the stones may vary with the character of the quarry, but where the thickness of the masonry is great a considerable proportion of large stones should be used. Where exceptionally large stones are employed the joints may be filled with concrete instead of mortar as in modern cyclopean rubble masonry. In such cases only so much water should be employed as can be brought to the surface by ramming. In carrying out the construction of rubble- masonry work it should not be built in horizontal courses; at the same time it must be built in beds, and these should be irregularly stepped, and various parts of the structure worked upon and allowed to set at different times. The surface of these horizontal steps or courses should bristle with projecting stones, so as to secure a 43 2 MASONRY DAMS perfect bond in every direction. This is done by working up the mortar or concrete between the stones to about half their height, and wherever the work is stopped over night or for a period of time these projections insure bond with the next layer to be worked. No stones should be deposited or dressed upon the wall, but on platforms or planking, so that no dirt shall be brought in contact with the material. The same precaution must be taken in handling concrete and mortar. The rubble facing stones should be of large size, not less than 2 feet deep, with frequent headers. Where especial jar is brought on the masonry work, as in overfall weirs, facing stones should be of range rubble, of the soundest and most durable quality, and should be cut so true that joints not exceeding J inch shall be necessary for 3 inches from the surface, the remain- der of the joint not exceeding 2 inches in thickness at any point. In such work it is well to alternate about two stretchers for one header, and to make the former not less than 3 feet in length, while the header should not have less than 12 inches lap under ordinary circumstances. The concrete used in work of this character should be made of rough broken stone metal, and of clean river gravel not ex- ceeding from 2 to 2j inches gauge. This material should be washed free of dirt before being used, and be mixed in boxes or mortar mixers with mortar of a proper quality. The pro- portions used in mixing differ greatly, and are described in tech- nical books treating on this subject. After cement masonry has been allowed to rest until it has had time to dry and harden it must be gone over with sharp picks or chisel-edged tools to remove the scale, roughen the surface, and make it clean and fresh in order that the new mortar may adhere to it. This is especially true of new work laid on old which has set for several months. Masonry should not be built in winter during freezing weather unless exceptional precau- tions are taken to cover and protect it from frost. Recent experi- ments with masonry built in freezing weather on Sodom dam showed that the effect of freezing was not as serious as had been anticipated, though no mortar was set in temperatures less than DETAILS OF CONSTRUCTION 433 + 20 F., and hot brine made of five pounds of salt to one pound of water was used for mixing. This and the fact that the sand and stones were heated is believed to have helped the quality of this cement. In addition, salt was scattered over the new work at night, and at times a layer of sand was spread over to protect it. Masonry laid under these circumstances showed in the spring but slight damage to the surface. A thin scale not exceeding one-eighth of an inch in thickness was left, which was easily scraped off, and under this the mortar was in good condition. Many mechanical devices are employed both for the mixing of cement mortar and the conveying of mortar and stones to the work, and for laying the same. Descriptions of these, how- ever, are to be found in special works on the subject. The chief object of mechanical mixers is thoroughly to incorporate the dry materials so as to bring them into intimate contact. Of the mechanical conveyors the more common are bucket eleva- tors and inclined tramways. Perhaps the most useful for the construction of dams, which because of their location are usually inaccessible, is the overhead cableway, by which materials are conveyed from the sidehills and delivered to any point on the dam. One of the most notable of such cableways was that used in the construction of the Colorado River dam. This cable was suspended on two towers, the higher of which was about 70 feet tall and was situated at a point 65 feet above the crest of the dam. The main cable was 2\ inches in diameter and 1850 feet long, being 1350 feet between points of support, and on this cable the carriage and its operating cables were supported. On the new Croton dam two steel towers, each 25 by 50 feet in plan, were used. In each corner was a bull- wheel derrick pro- vided with a separate driving engine, and each tower was 50 feet in height. On the McCall's Ferry dam steel goose-neck shaped travelling cranes, running on tracks on a temporary dam, were used for handling concrete and forms (Fig. 158). Various methods are employed to preserve the batter lines of a masonry dam during construction. On the Bhatgur dam this was done by means of large wooden forms constructed to 28 434 MASONRY DAMS scale from drawings and set and tested by transit instruments. These forms gave the masons outlines which they had no diffi- culty in following. On the Sodom dam the true batter-points were established for each course of the facing stone at every twenty feet of the length of the dam by the use of instruments. These batter-points were cut in the stone and the foreman re- quired to work to them for each succeeding course, and at change of batter short profiles fifty feet apart were set out by the en- gineers to insure the correct laying of the first course at the new rate of batter. At McCall's Ferry dam the forms consisted of interchangeable steel frames filled with wooden box lagging to conform to the surface of the dam (Fig. 158). At Cross River dam of the Croton watershed and the great Olive Bridge dam on Esopus creek, in the Catskills, N. Y., the batter lines of the face are secured by the use of moulded concrete blocks for the faces of these dams. These blocks are moulded in wooden forms provided with steel face plates to insure smooth- ness. They are in headers and stretchers with interlocking grooves for bonding, and weigh several tons each. The concrete used is i : 2^ to 4! , and the mortar used for setting them is i : 2^, that for pointing being i : i. 338. Waterproofing Materials. It is frequently necessary to line the inner slopes of earth embankments or loose-rock or masonry dams, and the entire inner surfaces of small artificial storage reservoirs such as are used in storing the discharge for a day or two, either of sewage or artesian water. It is common to use such small distributary reservoirs in connection with pumped water, especially where pumped by wind-mills, or for water which is to be furnished through pipes for subirrigation. Linings for large storage dams are applied with the object of preventing leakage which may endanger their integrity, or for the purpose of preventing loss of water as in the case of a loose- rock dam. Some of the modes of making loose-rock dams im- pervious have been described in Arts. 307 to 313. Several earth dams with masonry cores, and gravity masonry dams, have had one or more coatings of rich cement wash or natural bitumen applied somewhat like whitewash or as a thick paint to their inner WATER-PROOFING MATERIALS 435 surfaces to make them less pervious. This has proved effective in preventing sweating on the outer surfaces of the dams or core- walls. The only successful way to make a masonry dam or core-wall waterproof is to make the concrete or mortar rich in cement, at least for a few inches on the face, and to mix and lay it relatively wet and to tamp it thoroughly. One of the most impervious linings for earth embankments is asphaltum. Its toughness and flexibility enable it to conform without rupture to slight cracks and settlements of the underlying material, thus indicating where repairs may be necessary, while such repairs may be easily made in the asphaltum. The bottoms of earth distributary reservoirs, the inner slopes of a number of earth embankments in California and Colorado, and the bottoms and sides of earth canals and tunnels have been lined with this substance, which has remained in satisfactory condition, always easy to repair, for a number of years, and experience shows that where properly applied such linings have proven successful under the most trying conditions. A number of methods have been devised for making the asphaltum adhere to the surface beneath, and thus prevent slipping or crawling in hot weather. One of these is by an- choring heavy burlap at the top of the slope, stretching it tight upon and pressing it into the first coat of asphalt. Upon this a second coat of asphalt is spread. Such application of burlap to the Linda Vista Reservoir in Oakland, California, which is 35 feet deep with slopes of i on i, prevented the creeping of the asphaltum for a number of years. An equally successful mode of fastening the asphaltum is by the use of anchor spikes cut from strap iron about an inch wide and 6 to 8 inches long, which are driven through the asphalt into the banks, and over this a second coating of asphalt is applied. An interesting example of the use of asphaltum for lining dams is the case of the two West Ashland Avenue reservoirs in Denver, Colorado, on which this lining was applied by Mr. J. D. Schuyler. The maximum depth of one of these reservoirs is 32 feet, with side slopes of i on i J. Beginning at the bottom of the slopes, the asphaltum was laid in horizontal strips about 10 feet 436 MASONRY DAMS wide with an average thickness of if inches, and was spread with hot rakes and tamped with hot square tampers and ironed with heavy hot smoothing-irons much as is the asphaltum used in street pavements. While this sheet of asphalt was warm, strap-iron anchor spikes i inch wide, J-inch thick, and 7 to 8 inches long were driven through the asphaltum into the bank in rows i foot apart and i foot between centers in the row, every other row being flush with the concrete, the alternate rows being allowed to project for the support of scantling on which the workmen stood. When the final coat was applied the projecting spikes were driven flush, and all painted over with bitumen. The asphaltum used on these reservoirs consisted of 78% La Petra asphalt with 22 % of Las Conchas flux from the Lower California coast. This was boiled in open kettles for twelve hours at a temperature a little over 300 and frequently stirred; 20% by weight of this was mixed with 80% of sand previously heated to the same temperature. The weight of this mixture after being applied was about 127 pounds per cubic foot. Upon this lining was applied a second or paint coat of pure Trinidad asphaltum fluxed with residuum oil and poured on hot from buckets, and ironed over with cherry-red-hot irons. A more satisfactory cohesion was gotten between the two coats by apply- ing the second quickly after the first was laid and while it was still warm and clean, the thickness of this second coat being from J to \ of an inch. The cost of this lining was about 1 5 cents per square foot. An asphaltum-concrete lining was used by Mr. R. B. Stanton in the construction of a small placer-mining dam in an inaccessible portion of the mountains of Southern California, in which asphal- tum was used as a mortar or binding material with broken stone. The stone was in sizes of two inches and under, all the fine material and dust being used so as to form a nearly perfect concrete. The rock was heated and mixed in a pan, and a hot paste composed of four parts of California refined asphaltum and one part crude petroleum was boiled in another pan, poured over the hat rock, and well mixed with shovels and hoes. This concrete was put on in layers four inches in thickness, in horizontal strips four to six SUBMERGED DAMS 437 feet wide, and where the strips joined the old edge was coated with hot paste. Over the whole a second coating of hot asphaltum paste, mixed in the same proportions and boiled for a much longer time, was applied, which when cool was hard and brittle like glass, yet tough and elastic when warm. This paste was applied and ironed down to a thickness not exceeding one-eighth of an inch. This lining stood for several years without showing a single crack. In one place the bank settled 6 inches under a strip 4 feet wide and the lining followed the settlement without break, and though applied on a slope of i J on i it has shown no tendency to creep, which is one of the great objections to a lining composed of asphaltum and sand. 339. Submerged Dams. In a few instances submerged dams have been constructed for the purpose of stopping the underground or underflow water in the beds of streams. This has been resorted to particularly in a few streams in the moun- tains of Colorado and California, where the surface flow is large, but as the streams reach the platins the water sinks and disap- pears. Its downward course then is stopped by some imper- vious bed of clay or rock, and there is created practically a slow- moving river under a bed of deep gravel. This can be brought to the surface by sinking a dam entirely across the stream bed to the impervious substratum, when the water will be raised, forming an underground reservoir; or a serious of cribs may be built on the impervious stratum under the gravels, and these will catch the water and lead it off, whence it may be removed by an open cut or by pumping (Art. 119). The former method is employed on the San Fernando Land and Water Company's property on Pacoima Creek in Califor- nia. At the site of the dam the sandstone canyon walls are about 800 feet apart and the bed-rock about 45 feet below the surface of the gravel bed of the stream. Through this a trench was excavated, in which a cobble-stone and Portland-cement masonry wall was built up, its bed width being about 3 feet and its top width 2 feet, its greatest depth being 53 feet and rising to a height of from 2 to 3 feet above the stream bed (Fig. 159). On the line of this wall are two large gathering wells, and on its upper 438 MASONRY DAMS face pipes are laid in open sections, so that the seepage water caught by the dam might enter these and be led through them into the wells, from which it is drawn off for purposes of irriga- tion. Above the dam the stream bed consists of several hundred acres of gravel 12 to 20 feet in depth, which forms a natural storage reservoir of 1200 to 1500 acre-feet capacity (Arts. 118 and 119). A somewhat similar submerged dam is in operation at King- man, Ariz., for providing a small supply to the town and railway. A masonry wall 173 feet long on top, 6 feet wide at base, and FlG. 159. View of San Fernando Submerged Dam. 2 feet wide on top is built on bed-rock across and through the gravel bed of Railroad canyon. A 6-inch cast-iron outlet pipe through the dam, 12 feet below its crest, which is below the level of the canyon bed, leads into an 8-inch standpipe perforated with f-inch holes placed ^ inch apart. In this is collected the water which gathers behind the dam to the full height of its crest* 340. Construction in Flowing Streams. In building any variety of dam across a flowing stream the expense of construe- CONSTRUCTION IN FLOWING STREAMS 439 tion is considerably increased by the necessity of handling the flowing water and keeping it away from the work of construction. Several methods are pursued, depending largely upon the dis- charge of the stream. If this is small, one of the simplest methods is to build an under or scouring sluice in the dam and construct this portion of the work first, so that the water may be permitted to flow off through it while the remainder of the work is being built. If the stream is subject to violent floods or its discharge is too large to be conveniently handled in this manner, wasteways at varying heights may be left in the crest of the dam over which the floods may fall. It is frequently necessary to build a tem- porary dam above the main structure with a view to retaining the water until the latter is completed; or a temporary channel may be built for the stream around the dam, and through this the water may be carried off. In the great Tansa and Bhatgur dams in India, where the floods discharged were very large, a portion of the masonry adjacent to either abutment was main- tained at a lower height than the rest in order that the floods might flow over it as over a wasteway. In commencing the construction of a dam where flowing water has to be controlled, if the discharge is not too great the stream may be diverted temporarily while the main portion of the dam is being built as in the new Croton dam; or if under- sluices are to be provided for the discharge of the water, these should be built first, the stream being passed to one side during their construction, after which it may be turned back through them, and the remainder of the structure carried up, as in the Roosevelt dam. If no undersluices are to be constructed, pump- ing may be resorted to if a temporary channel cannot be provided, though this method is not advisable and should rarely be resorted to. In founding a dam in quicksand two or three methods may be employed. Pneumatic caissons may be sunk, and the founda- tion built in these as would be done for a bridge pier; or if the sand is comparatively dry and semi-fluid, it may be frozen by the Poetsch process, and the excavation for the foundation can then be made within the frozen walls; or interlocking steel sheet pil- ing may be driven through the quicksand. 440 MASONRY DAMS 341. Specifications and Contracts. There are many trivial details of construction which must be considered by the engineer in designing earth, crib, and masonry dams. It is customary to have such structures built by contract, and for this purpose careful specifications are drawn, detailing the character of material and construction. For those who are unfamiliar with such forms of specifications, such books on the subject of specifications and contracts as those of Gould and Haupt can be purchased; or specifications which have been used by other engineers can be obtained through them. An excellent example of modern speci- fications are those used by the Reclamation Service and repro- duced in Art. 421. The usual form of specification opens with a general de- scription of the work and its location, a statement of the methods and appliances to be used in construction, a description of the protective work, highways, bridges, and diverting works, as well as pumping plant and other temporary work to be employed during construction. For earth dams the specifications then go into a description of the soil to be used, and where it is to be obtained; the depth of excavation and its character, and the method of retaining it; a description of the refilling of excava- tions and the building of embankments; and the question of sodding and paving or revetting the embankments. If the dam is to be of timber or loose rock, a description of the timberwork and cribwork is given, and the character of the rock excavation and explosives to be employed is entered into. If of masonry, the matter of excavation for foundation, measurement and disposal of the material removed, and method of stepping the foundation are first considered. Then the hy- draulic masonry is described, the cement and its tests, the pro- portions used in mixing mortar and concrete, the character of the brickwork and of the stone masonry, whether of dry rubble, rubble masonry, range-rubble facing, or cut stone. In addition to these there is usually some ironwork connected with the super- structure and gate-houses. 342. Examples of Masonry Dams. In Table XXIII are given the general dimensions of several of the largest masonry dams EXAMPLES OF MASONRY DAMS 441 which have been built. An account of the construction of ma- sonry dams would be incomplete without a few examples of the larger and more typical of the modern ones, and accordingly brief descriptions and illustrations of some of these are given here. These are divided for convenience into two general classes: i, 45.9 49.08 FIG. 1 60. Cross-section of Furens Dam, France. those which act as retaining-walls for the water and over which the latter is not expected to flow; and, 2, those which act both as retaining-walls and overflow weirs. The older and less typical forms of dams, such as those built in Spain in earlier days, and a few of those built in France and elsewhere, do not require de- 442 MASONRY DAMS scription here, as no such works are likely to be designed in the future. For those who are interested in their study, descriptions and cross-sections of these can be found in Wegmann's "Design and Construction of Masonry Dams," "Krantz's " Reservoir Walls," Schuyler's " Reservoirs for Irrigation," or in the twelfth > 4.00 J T 71 4100 FIG. 161. Cross-section of Gran Cheurfas Dam, Algiers. thirteenth, and eighteenth Annual Reports of the U.S. Geological Survey. 343. Furens Dam, France. This is one of the largest and first of the great dams built according to modern formulas (Fig. 1 60). It is 170.6 feet in maximum height above bed-rock, GRAN CHEURFAS DAM, ALGIERS 443 the maximum depth of water being 164 feet; its thickness at top 9.9 feet, and at base 161 feet. The maximum pressure on the masonry is 6.82 tons per square foot, while its total length is 328 feet on top. In plan it is curved with a radius of 828.4 f eet > and it is built entirely of rubble masonry, the facings being of the same material. The top of the dam is finished off as a roadway 3 406' Flood Level '- 4 -LV - A 405' Full supply Weight of Masonry, 150 Ibs. per sq. ft. Note. Pressures reservoir-empty, in Ibs. per sq. inch. FIG. 162. Cross-section of Tansa Dam, India. 9.8 feet wide, and this is protected by two parapets, one on either side, each 1.6 feet in height. 344- Gran Cheurfas Dam, Algiers. This dam (Fig. 161) was built in 1882, and has a total height above its foundation of 98.4 feet. Its width at top is 13.1 feet, at the base 72.2 feet, and its top length is 508.4 feet. It is built practically in two 444 MASONRY DAMS parts, the first consisting of a trapezoidal-shaped foundation mass of rubble, on which is built the dam, the upper and lower surfaces of which are parabolic. The depth of water which this dam will hold is 132.2 feet, and the maximum pressure on the masonry within it is 6.14 tons per square foot. In plan it is straight. 345. Tansa Dam, India. This great dam is built through- out of uncoursed rubble masonry. It is designed to have a total height of 133 feet, though it has as yet been completed only to a height of 118 feet (Fig. 162). At this height its max- imum top width is 15.2 feet, while its maximum width at base is 96.5 feet. Its total length on top is 9350 feet, while in plan it is built in two tangents, the apex pointing up-stream. Near the south end is built a wasteway 1800 feet in length, its crest being 3 feet below that of the dam. This wasteway is built in a portion of the dam where its height fe but a few feet, and it discharges back directly into the river channel below the toe of the structure. Near the base of the dam is a large outlet tunnel, which discharges into the conduit which carries the water to Bombay for the supply of that city. 346. Bhatgur Dam, India. This dam (PL XXV) is 4067 feet in length, and is constructed of the best uncoursed rubble masonary in cement, excepting in the upper central portion, where the pressure is less than 60 Ibs. per square inch. There it is of concrete with blocks of rubble imbedded in it. On the faces the dressed rubble is laid up in courses. It is 127 feet in height, 74 feet in width at the base, and 12 feet wide on top (Fig. 163). When full the pressure on the lower toe is 5.8 tons per square foot, and -when empty the pressure at the upper toe is 6.7 tons per square foot. In plan the dam curves irregularly across the valley, following an outcrop of rock. Portions of either end of the dam, where it is not high, are left 8 feet lower than the remainder so as to act as wasteways. The total length of these waste ways is 810 feet, and they are arched over in such manner as to leave a roadway across their tops. Below the dam and jutting from it are masonry walls which lead the waste water off in such manner that it flows clear of the foot of the dam and 446 MASONRY DAMS passes off through separate channels to the main stream below. For the purpose of scouring silt which may be deposited in the reservoir, fifteen undersluices are constructed near the center 3&&tf3-&i !&&&&& SK*?K t^ JV^P^fc -' FIG. 163. Cross-section of Bhatgur Dam, India. of the dam, at its deepest part. These are placed 17 feet apart and are 4 by 8 feet in dimensions, their sills being 60 feet below high-water mark. Above these are two other undersluices for THE NEW CROTON DAM, NEW YORK 447 discharging the water to be used in irrigation when the reservoir is full. One of these is 20 feet and the other 50 feet above the main row of undersluices. 347. New Croton Dam, New York. This consists of a high masonry darn for 2260 feet, thence to the left bank the structure consists of a masonry overfall weir of heavy cross-section and FIG. 164. Cross-section of Masonry Dam, New Croton Dam, Cornell's. 1020 feet in length on the crest. The capacity of the reservoir is 92,000 acre-feet. The main dam has an extreme height of 297 feet above its foundation and is 166 feet in height above the river-bed. The crest of the dam is 16 feet above the high- water level or crest of the overfall weir. Its extreme width at base is 185 feet and at its top 1 8 feet, surmounted by a 4-foot coping. So much of this structure as was built prior to 1904 is of the best rubble-stone masonry laid in cement mortar and faced above the ground sur- 448 MASONRY DAMS face with coursed stones set in Portland cement. That built since is of cyclopean rubble set in concrete, faced with rubble masonry. In plan the dam is straight to the masonry overfall weir, which curves up-stream nearly at right angles to the main structure. The water falling over this weir spills into an artificial channel excavated in the hillside and emptying into the main channel below the toe of the dam. The extreme height of the weir is 154 feet, and its extreme width at base 195 feet. It has a very slight batter on the up-stream side, while its lower side has a slightly ogee-shaped curve broken by 25 steps varying from 2 to 10 feet in FIG. 165. Cross-section of Overfall Weir, New Croton Dam, Cornell's. height. This weir is constructed, like the dam, of an uncoursed rubble masonry interior and coursed faces (Fig. 165). 348. Periar Dam, India. This dam, which is constructed with a concrete hearting, faced on either side by rubble masonry from 6 to 20 feet in thickness, is 1480 feet long on top, has a maximum height of 173 feet above bed-rock and 155 feet above the river-bed (Fig. 166). Its crest is surmounted by a parapet 5 feet in height, the maximum depth of water which the dam will hold being 160 feet, and its width at base 138 feet 9 inches, its top width being 12 feet. At the right end is a wasteway built in solid BEETALOO DAM, SOUTH AUSTRALIA 449 rock, forming the abutment of the dam and separated from it, its length being 420 feet. At the left end is an earth embankment 250 feet long and reaching to an elevation of 170 feet. The maximum capacity of the reservoir will be 306,000 acre-feet, its available capacity being 157,000 acre-feet. 349. Beetaloo Dam, South Australia. This structure (Fig. Roikf Scale. 1 inch =50 fee* FIG. 1 66. Cross-section of Periar Dam, India. 167) is no feet in maximum height, no feet wide at the base, and 14 feet wide on top. Its length on top is 580 feet, and it is curved in plan, the convex side facing up-stream. It is con- structed throughout of concrete, and in one end of the dam is built a set of three wasteways, their total length being 200 feet, with their crests 5 feet below that of the main structure. These 20 45 MASONRY DAMS wast cw ays are separated by masonry walls, which lead the flood waters back into the river below and clear of the structure. 350. Remscheid Dam, Germany. This structure supplies the city of Remschied, and is an excellent typeof modern European masonry structure. It is built throughout of rubble masonry, the stone being a hard slate and the mortar a hydraulic lime some- what like the pozzolan of Italy and the kunkar of India. This dam has been finished for a number of years and shows no signs of leakage or cracks, the upper face having been heavily plastered J10 above S Urcl FIG. 167. Cross-section of Beetaloo Dam, Australia. with Portland cement over which tw r o coats of asphalt were placed. Outside of this latter a brick wall ij to 2\ bricks thick was carried up tight against the asphalt. The dam is curved in plan, with a radius of 410 feet. It is 82 feet high, 49 feet thick at base, and 13 feet thick at the crest, the reservoir capacity being 1180 acre-feet. The masonry was laid in curved instead of horizontal courses in such manner that each course is nearly perpendicular to the varying direction of resulting pressures. 351. San Mateo Dam, California. This structure is built throughout of concrete, not as a monolithic mass, as is the case with the Beetaloo dam, but, as described in Article 325, it was built up in blocks set in place, the weight of each being about 9 tons. In cross-section this structure is heavier than theory alone SAN MATEO DAM, CALIFORNIA 45 452 MASONRY DAMS would require. As shown in PL XXVI, its maximum height is 170 feet, its crest being 5 feet above high-water mark, at which level is a wasteway built a short distance above the north end of the dam and separated from it by a low ridge. The top width of the dam is 25 feet and its width at the bottom is 176 feet. Its upper slope has a uniform batter of 4 on i, while the lower slope, beginning with a batter of 2^ on i at the top, curves to within a few feet of the bottom, where the batter becomes i on i. In plan this structure is curved up-stream with a radius of 637 feet. Its maximum storage capacity is 62,000 acre-feet. 352. Sweetwater Dam, California. This dam (PL XXIX) is slighter in cross-section than theory would require, and de- pends to a certain extent on its curved plan for its stability. As shown in Plates XXVII and XXVIII, it is 90 feet in maximum height, 380 feet long, 12 feet wide on top and 46 feet wide at the base. The radius of its curvature is 222 feet, and as the length of the radius is small and the curvature great, this adds considerably to its stability. The structure is built throughout of large uncoursed rubble masonry, the greatest care having been used in ever} 7 detail of construction. At its southern end are a set of seven escapeways 40 feet in aggregate width, so arranged that the water issuing through them drops first into a series of water-cushions, and is then led off by a directing wall so as to clear the dam. Near its base is a discharge sluice, oper- ated from a water-tower in the reservoir. In 1895 tne dam was called upon to withstand an extraor- dinary flood during which water to the depth of 22 inches flowed over its crest for 40 hours without serious injury to the structure. Afterwards the parapet was raised 5^ feet, making the greatest height of the structure above bed-rock 95.5 feet. The center of the parapet was lowered 2 feet, thus making an escape over the crest for a length of 200 feet. The wasteway at the end of the dam was extended 20 feet by adding four more bays of 5-feet width each. In addition to other remedial measures, a subsidiary weir 15 feet high and 18 inches thick was built of masonry 50 feet below the lower toe, and on a concentric curve with the main dam, to create a water-cushion. -Finally, an un- SWEETWATER DAM, CALIFORNIA 453 454 MASONRY DAMS 45 6 MASONRY DAMS used tunnel in bed-rock near the wasteway, 8 by 12 feet in section, was adapted for use as an additional wasteway by laying in it two 30-inch and two 36-inch iron pipes on a 4 per cent grade. These changes have increased the storage capacity of the reser- voir by 25 per cent, or to 22,566 acre-feet, and the discharge FIG. 1 68. Cross-section of Vyrnwy Dam, Wales. capacity of the combined wasteway to an amount believed to be sufficient to pass the greatest possible flood. 353. Vyrnwy Dam, Wales. This structure is peculiar in cross-section (Fig. 168), being unusually heavy, and much greater than theory would demand. The reason for this is that the crest of the whole dam acts as a waste weir, which is surmounted ASSUAN DAM 457 by arches on which rests a roadway, and beneath these arches the waste waters are permitted to flow. Its lower face is given an ogee-shaped curve, so 'as to reduce to a minimum the shock of the falling water, and there is a depth of 45 feet of back-water on its toe, which forms a sort of water-cushion. Its maximum height is 136 feet, while the greatest depth of water is 129 feet. Its width at base is 117.7 f ect > an d the upper curved portion rests on a massive pedestal nearly rectangular in cross-section and 43 feet in height. This dam is straight in plan, its total length on top being 1350 feet, and it is built throughout of large cyclopean rubble, the stones weighing from 2 to 8 tons apiece. 354. Assuan Dam and Assiout Weir, Egypt. The former of these is the greatest masonry dam in existence, completed in 1902, and extends across the valley of the Nile River and forms a storage reservoir therein of about 800,000 acre-feet, and is estimated as capable of irrigating a large portion of 2500 square miles from the Ibrahimia canal, about 350 miles lower down the river (Art. 131). This dam is 6400 feet long, founded on granite, and has a maximum height of 120 feet in the deepest part of the foundation (Fig. 169). It is of massive cross-section, as the floods of the Nile pass through, and may pass over it. It is 80.4 feet thick at base, 23 feet wide on top, the crest being 9.84 feet above estimated high water. The batter of the down-stream face is i to i J. In the structure are built 140 undersluices, each 6.56 feet wide and 23 feet high, and 40 sluices at a higher eleva- tion, each with one-half the area of the lower series. These are to pass the floods of the Nile and to scour the silt from the reser- voir, and 90 of them are designed to act somewhat as do the automatic gates at Bhatgur, India (Art. 374). All of the upper and 20 of the lower sluices are lined with cast iron, the remainder being of cut stone. The piers between them are 16.4 feet wide with abutment piers at every tenth sluice 39.37 feet wide. They are expected to pass maximum floods of about 490,000 second - feet, during which the sluices will be open. The structure con- tains nearly 1,000,000 cubic feet of masonry. At the head of the Ibrahimia canal, at Assiout, a great divert- ing weir is built across the Nile valley. This is of rubble masonry, 458 MASONRY DAMS 3930 feet long and 48 feet in maximum height. In it are 120 sluices, each 16.4 feet, separated by piers 6.56 feet wide. 355. Betwa Dam, India. This structure, which has an unusu- ally heavy cross-section (Figs. 170 and 184), performs the functions of a weir, the flood-waters being estimated to pass over the entire crest to an extreme depth of 6J feet. In the extraordinary flood FIG. 169. Cross-section Assuan Dam, Egypt. of 1901 the depth on the weir crest reached 16.4 feet without caus- ing any damage to the structure. The maximum discharge was estimated to have been 970,000 second-feet (Art. 373). In plan it is built in three tangents, following the line of an outcrop of rock. Its total length is 3296 feet, its top width being 15.2 feet, and its maximum height about 64 feet. The down-stream face of this weir is supported by a buttress or block of masonry 15 feet BETWA, DAM, INDIA 459 in width and 20 feet in height, while above it the back-water in the river rises to an additional height of about 10 feet, so that the flood-waters will fall on a water-cushion of this depth and then on the solid buttress. This structure is built throughout of uncoursed rubble masonry, its faces, however, being coursed with dimension stone and the coping being of ashlar. In the river some distance below its highest pbrtion is built a subsidiary or smaller weir, which backs the water up against the toe of Reservoir FIG. 170. Cross-section of Betwa Dam, India. the main weir in such manner as to form the water-cushion on which the floods may fall. The extreme height of this sub- sidiary weir is 18 feet, and the height of overfall from the main weir to the surface of the water-cushion is 21 J feet, though in time of greatest flood this will be reduced to 8 feet. The top of the subsidiary weir is 12 feet, and its walls are nearly vertical on the down-stream side, with a slope of 10 to i on the up-stream side. The question of increasing the storage capacity of the reser- voir dam having been contemplated for many years, it was pushed 460 MASONRY DAMS to completion in 1901 by adding a series of automatic drop-shutters to the weir crest. As this was of irregular cross-section it was levelled off and the crest raised one foot by adding rubble masonry. On this shutters 6 feet high were placed, making the total addi- tional height 7 feet (Art. 373) and the added storage capacity of the reservoir 17,500 acre-feet, equivalent to nine days full supply of the canal, which has a discharge of 1000 second-feet. The present total capacity of the reservoir is therefore 54,300 acre-feet. 356. La Grange Dam, California. This structure (Fig. 171) is heavier in cross-section than theory alone would demand, as it must withstand the flood-waters of the Tuolumne River, which passes over its entire crest to a possible maximum depth FIG. 171. Cross-section of La Grange Dam, California. of 1 6 feet. About 200 feet below the main dam is built a sub- sidiary weir, 20 feet in height and 120 feet in length, its top width being 12 feet. This weir will back the water up against the toe of the main weir to a depth of 15 feet, thms giving a water- cushion on which the floods may fall. The main weir is curved in plan with a radius of 300 feet; it is 320 feet in length on top, 90 feet in width at the base, 24 feet in width on top, and 128 feet in maximum height, and is built throughout of uncoursed rubble masonry. The dam is built for diversion purposes only (Art. 147), hence its entire crest acts as an overfall weir. In it are a couple of undersluices which served to pass water during con- struction, one at 'low water and the other 10 feet higher, their cross-sections being 4 feet wide by 6 feet high. The maximum flood which has passed over this weir since -.. 462 MASONRY DAMS its completion in 1894 was 46,000 second -feet, the depth on the crest being 12 feet, while it is estimated that it may have to pass floods of even 100,000 second -feet. 357. Folsom Dam, California. This structure (PI. XXX), like that just described, acts only as a diversion weir. It is 6gJ feet in maximum height on the up-stream side, and 98 feet in height on the down-stream side. Its cross-section is unusually heavy, as flood-waters to a depth of over 30 feet are expected to flow over its crest (PL XXXI). Its top width is 24 feet, and its extreme width at base 87 feet, the toe terminating in a heavy buttress of masonry. Its total length on the crest is about 520 feet, a large portion of which consists of a retaining- wall leading to the canal entrance. One hundred and eighty feet in length in the center of the main dam is lowered a depth of 6 feet to form a wasteway over which the floods may pass, and this wasteway is closed by a single long shutter, consisting of a Pratt truss backed with wood, which can be raised and lowered by means of hydraulic presses, operated from a power-house near by. The dam is constructed throughout of uncoursed rubble masonry. 358. Austin Dam, Texas. This dam was built in 1891-2 across the Colorado River for the supply of water and water- power to the city of Austin, Texas. In 1900, during a flood which topped its crest to a depth of nearly 10 feet, it failed by the sliding down-stream intact of a section 500 feet in length, due- largely to an insufficient bonding of the foundation in bed- rock, which was of a limestone easily leeched and seamed. Its interior was of rubble masonry, faced on both sides and on top with large cut blocks of coursed granite. It was 1275 feet long on top, 1125 feet of which are constructed as an overfall waste- way, and 66 feet in maximum height, its upper face being vertical. The lower face had an easy ogee-shaped curve (Fig. 172), calcu- lated to pass the waters with such ease that the erosive action at the base would be reduced to a minimum. The structure was practically a great overfall weir, the maximum flood to be passed being estimated at 250,000 second-feet from a catch- ment basin of 50,000 square miles. The cross-section was heavier than theorv would demand AUSTIN DAM, TEXAS 463 /! CROSS SECTION OF WEIR. PLATE XXXI. Folsom Canal Plan and Cross-section of Weir. 464 MASONRY DAMS if the dam were built to act as a retaining-wall only. The lower portion of the down-stream face was curved with a radius of 31 feet tangent at the bottom to low-water surface, so as to de- liver the floods away from the toe and against the back-water in the river. The upper end of the curve was tangent to the main slope, which has a batter of 3 in 8, and ends on top in a curve of 20 feet radius. This top curve was tangent to the hori- zontal crest line, which is 5 feet wide. The total top width was 1 6 feet, and the maximum width at base 68 feet. 359. Overfall Masonry Dam, Spier Falls, N. Y. This is Scale FIG. 172. Cross-section of Austin Dam. probably the longest and one of the highest masonry dams ever built across the channel of a great river. It is located on the Hudson River, in New York, about 9 miles above Glens Falls, and furnishes water for power, with an 8o-foot head, to ten tur- bines, each capable of developing 5000 horse-power. These drive dynamos which feed 50,000 horse-power of electricity to Glens Falls, Troy, Saratoga, Schenectady, and Albany, from 9 to 42 miles distant. The foundation was laid with the aid of great coffer-dams resting on a river-bed composed of masses of bowlders, cemented gravel, and hardpan. The cribwork was almost entirely covered by the material excavated from the dam site, which thus aided as a reinforcement and was essential as an aid in stopping leaks. The main, coffer-dam was of huge dimensions, being 250 feet in OVERFALL MASONRY DAM, SPIER FALLS, N.Y. 465 maximum width at base, 80 feet wide at top, 90 feet high, and 600 feet long on top. A portion of the dam in the river section is of the usual gravity masonry section, as shown in Fig. 173, the remainder is built as a Rad.= 81.74- FIG. 173. River Section, Spier Falls Dam, New York. spillway on the north side of the river and has an admirable over- fall section (Fig. 174). This spillway was built first and in it four archways, 7 by 10 feet, were left as undersluices to carry the 'river. 3 4 66 MASONRY DAMS These sluices were 35 feet above the river-bed, and were finally closed with sliding gates and permanently filled with mason ry. The maximum height of the overfall section is 80 feet above the river-bed with a width on top of about 1 7 feet. The top is curved, however, with a radius of 16 feet, and thence the down-stream curve is reversed to a straight section having a batter of .6 foot per foot, and this eases off to a concave curve of 35 feet radius. The river section or main dam has a top width of 17 feet, a height above river-bed of 90 feet and a maximum height above FIG. 174. Overfall Section, Spier Falls Weir, New York. foundations of 152 feet. Its maximum width at bottom is 113 feet and the cross-section that called for by modern formulae. Both the main and the spillway dams are founded on a hard-granite rock. The material used in the dam is rough rubble masonry of all sizes of granite stones up to some of cyclopean dimensions. These are set in concrete cement and into the large spaces spalls were rammed. The mode of construction of this rubble concrete- is almost identical with that used on the Bhatgur dam, India, except that the facing stones were even less shaped and dressed. The face stones in the river section were laid dry with their beds inclined to the horizon, the joints being grouted. The face stones of the overfall section were brought from a distance and were carefully dressed. 360. Roosevelt Dam, Arizona. This structure creates the PLATE XXXII. Plan of Rcx>scvelt Dam, Arizona. 467 468 MASONRY DAMS storage reservoir of the Salt River Valley project. It was built on the Salt River below its junction with the Tonto River, about 50 miles above Phoenix, Ariz., by the United States Reclamation Ser- vice, and stores about 1,100,000 acre-feet of water in a reservoir 20 miles long by from i to 2 miles wide up the Salt River and about 16 miles up the Tonto. Floods exceeding 4000 second-feet are liable to pass over the dam, and were carried off during construc- tion through the permanent outlet tunnel constructed in solid rock under the abutments before the structure was closed. The dam has a maximum cross-section (PL XXXIII) 270 feet in height above the lowest point in foundation, the height of spillway being 210 feet above mean low water. The roadway, bordered by a parapet along the crest, is 230 feet above mean low water and 1 6 feet in width. The length of the dam at river-bed is 210 feet and 700 feet along the top, and its extreme width about 165 feet (PL XXXII). This is one of the highest masonry dams ever constructed, and contains about 300,000 cubic yards of masonry. The outlet tunnel is about 400 feet long, and in it are placed six gates for sluicing out silt and regulating the flow of water to be drawn off (Art. 381). This is discharged into Salt River down which it runs about 50 miles to a diversion weir, where it is picked up at the Granite Reef weir (Art. 188), and distributed through canals to the irrigable lands m the vicinity of Phoenix and Mesa, Ariz. The whole system of dams, canals, distributaries, etc., is known as the Salt River Project, and the storage-water is expected to irrigate nearly 200,000 acres. Incidentally the power plant, built at the foot of the dam for utilizing the energy of the water to be drawn off to the 80- foot level, and other power plants to be erected along the Salt River at falls, develop about 10,000 horse-power, which is electri- cally transmitted to irrigable lands and utilized in pumping a sufficient amount of water estimated to irrigate 50,000 additional acres. The lands of the Salt River valley contain at least three water-bearing strata; the second, extending to a depth of over 200 feet, is already being extensively pumped and furnishes such an abundant supply that no appreciable effect on the water-level has yet been produced. ROOSEVELT DAM, ARIZONA 469 Water $urface+2 ' El. -30' u-io4>^iof"' 110^4 - 181.04 feet- j 158 feet Scale of Feet 10 20 30 40 50 PLATE XXXIII. Maximum Cross-section, Roosevelt Dam, Arizona. 47 MASONRY DAMS The masonry in the dam is of broken-range cyclopean rubble, made so as to break joints and be thoroughly bonded in all directions. Electricity for lighting by night and for development of power for handling derricks and cement plants, etc., was furnished from a power canal 19 miles long, taken from the Salt River above the dam, and having a capacity of 200 second-feet. The dam is built on a curve having an up-stream radius of about 400 feet, though its cross-section is that required by theory, and closely resembles that of the new Croton dam, N. Y. (Art. 347). The concrete consists of i part Portland cement, 2\ parts sand, including run of crusher passing J-inch screen, and 4 parts of broken stone up to and not exceeding 2-inch-mesh screen; the sand contained not more than 10 per cent clay or other foreign substance. The stones were laid not nearer than 2 inches apart, and weighed up to 10 tons or greater. The upper 100 feet of the dam was reinforced during construction with railroad steel to enable it to resist tensile strains due to temperature changes. Moreover, it was built only when the temperature was below normal, thus insuring compressive strains most of the time. The specifications for the construction of the dam, which with auxiliary and diversion works is estimated to cost $3,200,000, are presented in Article 420 as a fair sample of similar specifications issued for the construction of other work of the Reclamation Service. 361. Shoshone Dam, Wyoming. This structure was built by the Reclamation Service to store water on the Shoshone River, Wyoming. Thence the stored water flows down the river for a number of miles to the Corbett weir (Art. 187) which diverts it through a tunnel to the Garland canal for irrigation in the neigh- borhood of Cody. The dam, which is of cyclopean rubble, is 310 feet high, 200 feet long on top and 85 feet at bottom. It is curved up-stream with a radius of 150 feet and has a cross-section far lighter than required by theory, being largely dependent for its stability on arch action. The up-stream face has a batter of 0.15 in i and the down-stream face 0.25 in i to within 60 feet of the bottom below which the sides are vertical. The top width is 10 feet and SHOSHONE DAM, WYOMING 471 the bottom width 108 feet (Fig. 075). The reservoii capacity is 456,000 acre-feet. The foundation and walls are of granite, of which material the dam is built. There is a spillway 250 feet long discharging through a tunnel in the hillside. 5065' FIG. 175. Cross-section of Shoshone Dam, Wyoming. 362. Bear Valley and Zola Dams. Two of the most notable curved dams are the Bear Valley dam in California and the Zola dam in France, the cross-sections of which arc unusually 47 2 MASONRY DAMS light, as they depend chiefly on their curved plan for their stability. The former (Fig. 176) is but 3.2 feet in width on top, and at a depth of 48 feet below its crest its width is but 8.4 feet. At this point an offset of 2 feet is made on each side, and its width thence increases to 20 feet at its base, which is at a point 64 feet below its crest. The structure is 450 feet in length on top, and in plan it is curved with a 300- foot radius (Fig. 177). It is built throughout of the best uncoursed rubble granite masonry, and depends almost wholly on its curved plan and the excellence of its construction for its stabil- ity, since the lines of pressure with the reservoir full fall from 13 to 15 feet outside of its base. The Zola dam (Fig. 178) is 123 feet in maximum height, 19 feet in width on top, and 41.8 feet in width at the base. Its length on top is 205 feet, and it is curved with a radius of 158 feet. Like the Bear Valley dam, it depends chiefly on its curva- FIG. 176. Cross-section of Bear Valley Dam, California. FlG. 177. Plan and Elevation of Bear Valley Dam, California. ture and the excellence of its construction for its stability. The material of which it is built is uncoursed rubble masonry. 363. Upper Otay Dam, California. This is a masonry UPPER OTAY DAM. CALIFORNIA 473 structure of unusually light cross-section, being nearly as frail in dimensions as the celebrated Bear Valley dam. It is located on the north branch of Otay River, above Lower Otay reservoir (Art. 311), at a narrow gorge where there are excellent porphyry abutments the width between which at stream-bed is but 20 feet. The length of the dam at the top is 350 feet, its maximum height above bed-rock is 75 feet, and in plan it is curved with a ladius _____ _n n UPPER OTAY SWEETWATER DAM ZOLA DAM FIG. 178. Sections of Arched Masonry Dame. of 359 feet (PI. XXXIV). The greatest width or thickness at base is but 14 feet, the width on the crest is 4 feet. This dam was built with great care, of the best Portland- cement concrete masonry, and for its length and height probably ranks with any structure of its kind in minimum section and cost. Two tiers of steel plates were set in the cement longitudinally at the axis of the dam to add strength, and i^-inch railway cables were laid above these vertically at intervals of 2 feet and reach- ing within 5 feet of the crest. It was completed to its present height several years ago, but the catchment basin above it is so limited that it has never yet been filled, nor is it likely that it ever will be filled, from its own drainage basin. Therefore there is little danger of its being topped by a flood. The storage capacity of the reservoir is but 2000 acre-feet. There is a very limited wasteway at one end, and in the top or crest are a number of 474 MASONRY DAMS notches about 4 feet in depth designed to waste before the crest is reached. 364. Buttressed and Arched Masonry Walls. A dam has two functions to perform; one, to present an impervious barrier to seepage, through its body; and, two, to withstand the pressure tending to thrust it away or overturn it. The first is effected by the impervious nature of the materials opposing it, as clay puddle, cement masonry, wooden facing, etc. The second by the weight or stability of the mass of the structure. Efforts have been made from time to time to procure imper- viousness by light steel faces, as at Ash Fork (Art. 365) where stability is secured by steel framing securely anchored. At least three masonry dams have been built with this end in view by erecting comparatively thin masonry walls and bracing them with buttresses or vertical arches. One of these is the dam at Lake Fife, which furnishes the water-supply of Poona, India. This structure is founded on sloping rock and is built of un- coursed rubble masonry. Its total length is 5136 feet, of which 453 f ee ^ ac ^ as a wasteway; its maximum height above the foundation being 80 feet. The design of the dam is crude. At first it was built 14 feet wide on top, with straight slopes on either side of 2 on i down-stream and 20 on i up-stream. It soon showed signs of weakness, and to strengthen it a great earthen embank- ment 1 6 feet wide on top and 30 feet high was built against its lower face. In plan the dam is in several tangents, with change of top width for each, and at the points of juncture the masonry wall is backed up by heavy buttresses of masonry. A masonry dam of very unusual design is that which closes Meer Allum, from which the water-supply of the city of Hyder- abad, India, is drawn. The structure is built in the form of a large arch which consists of tw r enty-one smaller arches or scallops, transmitting the water pressure to solid -masonry buttresses. The lake has an area of about 9000 acres and a capacity of about 6500 acre-feet. The greatest depth of water is nearly 50 feet. The catchment area of the basin is hilly and undulating and fairly well covered with jungle. The main feeder of the lake takes its rise from the river Esee, and is about eight miles in length. 47 6 MASONRY DAMS The dam is, roughly, half a mile in length, and the twenty-one arches composing it range all the way from 70 to 147 feet in length of span. The largest of these arches, which is about the center of the dam, is shown in Fig. 179. The dam is built with walls vertical on both faces, the down-stream face being rapidly stepped out near the top so as to attain the maximum SECTION A-B SECTION C-D FIG. 179. Meer Allum Dam, India. Plan and Sections of One Arch. thickness of 8 feet, 6 inches within a few feet. A waste weir is provided at one end of the dam, but during heavy rains, when the lake is full, the water flows to a depth of i or 2 inches over the crest of the whole dam. At Belubula, New South Wales, is a somewhat similar struc- ture 60 feet in height, 431 feet long, but with six buttresses 28 feet apart from center to center, each being 40 feet long and from ; to 12 feet thick. Within these brick arches were built BUTTRESSED AND ARCHED MASONRY WALLS 477 4 feet thick at bottom and ij feet at top, at an angle of about 60 degrees to the horizontal. A unique buttressed dam of reinforced concrete has been built by the Reclamation Service to close East Park reservoir, Orland project, California. This dam, which acts as a spillway in flood, Expansion f Cut off wall 1 18" Wide, totw carried well Into SECTION C C FIG. 1 80. East Park Dam and Spillway, Orland Project, California. is but ii feet high and consists of a number of circular walls of 13^ feet radius, convex up-stream and sustained by concrete buttresses of 8 ft. thickness, sloping down-stream with gradient bfijto i. These walls (Fig. 180) are of reinforced concrete 18 inches 478 MASONRY DAMS thick, resting on a floor 12 inches thick, and below the walls and between ihe buttresses are subsidiary walls 2 feet high forming water-cushions. Down-stream is a concrete apron 8 inches thick extending for a distance of 30 feet. 365. Steel Dam, Ash Fork, Arizona. This structure, built wholly of metal and intended for the impounding of water, was built by the Santa Fe railway to store water for use of locomotives and for city supply, and has a capacity of no acre-feet. A similar dam, 70 feet high, built across the Missouri River, near Helena, Montana, recently failed during a flood. The Ash Fork dam is 184 feet long on top, and about 300 feet in total length, including a short concrete abutment at each end. Its greatest height is 46 feet. Structurally it consists of a series of triangular steel bents or frames, resting on concrete founda- tions and carrying steel face-plates on the inclined or up-stream face of the bents. The foundations of the steel bents are of Portland-cement concrete and the vertical posts rest on concrete walls (Fig. 181). There are 24 bents, each a right-angled triangle, with the inclined side having a slope of 45, facing up-stream, the rocky bottom of the canyon forming the base. The dimensions of the bents vary with their height. The end bents (Nos. i to 7 and No. 24) are 12 to 21 feet in height, each consisting of a vertical Z-bar column and an inclined I-beam. Bents Nos. 8, 9, 22, and 23 are about 33 feet high. Each has a vertical Z-bar column, an inclined I-beam, and two inclined posts or columns built up of Z-bars, the upper of these resting on the same shoe or bedplate as the vertical post. Bents Nos. ic, n, 12, 19, 20, and 21 are 33 feet to 41 feet 10 inches high. These have but one inclined post, which rests on the same bedplate as the vertical post while above it are truss members. connecting the face member with the posts. Bents Nos. 13 to 18, inclusive, are 36 feet to 41 feet 10 inches high, and have two inclined posts, with truss members above the upper post. In all of them the face is composed of a 2O-in. 65-lb. I-beam, reinforced on the underside by a plate J inch thick and 18 inches wide. The vertical and inclined posts are all composed of four Z-bars and a web-plate. The bents are STEEL DAM, ASH FORK, ARIZONA 479 connected by four sets of transverse diagonal bracing between the vertical and inclined posts. The bracing is composed of single or double angle-irons, 1X3X3 inches, the ends of which are riveted to connect ion -plates. The structure is composed of alternate rigid and loose panels. The crest or apron -plates which fit the braced panels between the bents are riveted to a curved angle, which is riveted to the upper end of the curved plate, while in the unbraced panels this curved angle merely bears on the apron-plate. The face of the dam FIG. 181. Steel Dam, Ash Fork, Arizona. is composed of steel plates -jj inch thick and 8 feet io inches wide and 8 feet long, riveted to the outer flanges of the I-beams of the bents. They are curved transversely to a radius of 7 feet 6 inches, forming a series of gullies or channels down the face, the width of the channels being 7 feet 5 inches measured on the chord, leaving at each side a flat portion which rests on and is riveted to the I-beams. There are seven expansion rivets at intervals of about five bents, and all joints exposed to water- prcssure are well caulked. A weakness of the structure is the failure to have provided 480 MASONRY DAMS a wasteway, the crest of the structure being expected to pass floods to a depth of six feet. Moreover, the masonry foundations were not carried down to impervious rock, and in consequence the dam at first failed to serve its purpose, much of the water impounded being passed under and around it by sepage through the permeable loose rock and volcanic cinder foundation material. Later concrete was used to connect the steel facing with the rock foundations, and this was covered with asphaltum and is reported to have greatly reduced the leakage. CHAPTER XVIII WASTEWAYS AND OUTLET SLUICES 366. Wasteways. Wasteways, escapes, or spillways as they are sometimes called, are an essential adjunct of every dam. They are to a reservoir what a safety-valve is to a steam-engine; the means of disposing of surplus waters due to floods and pre- venting these from topping the dam and possibly causing its destruction. Water should not be permitted to flow over the crest of a masonry dam unless it has been built in an unusually substantial manner calculated to withstand the shock of its overfall. It should never be permitted to flow over the face of a loose-rock or earth dam. The outer slope of an earth dam is its weakest part, and if water is permitted to top it it will speedily cut it away and cause a breach. Too many of the great floods which have occurred in recent years bear testimony to the necessity of constructing substan- tial and ample wasteways. Moreover, an ample wasteway being provided, the greatest care shoud be exercised to maintain it always open and ready for use, independent of all undersluices and other discharge outlets which may be closed by valves or other mechanical means. To the lack of one or both of these precautions was due the destruction of the South Fork dam in Pennsylvania in 1889; of the Walnut Grove dam in Arizona in the spring of 1890, and many other similar catastrophes. Had the wasteway to the South Fork dam been ample, as it origi- nally was, the water would not have flowed over the crest of the dam and have caused its destruction and that of Johnstown. But the wasteway was barred by fish-screens, and these not only obstructed the passage of the water but caught floating timber and logs brought down by the flood, which so diminished the area of the spillway as to cause the waters to top the dam. In the case of the Walnut Grove dam the area of the wasteway was in- 31 481 482 WASTEWAYS AND OUTLET SLUICES sufficient, resulting consequently in the passage of much of the flood-water over the dam crest and in the destruction of the work. 367. Character and Design of Wasteways. In design- ing a wasteway for a reservoir, data relating to the greatest floods likely to occur must be sought for in its catchment basin, and the dimensions of the wasteway must be proportioned for the extraordinary floods. The methods of determining the great floods and the necessity for looking for signs of these in the valleys has already been discussed in Chapter IV. Should other reser- voirs exist above that under consideration, provision must be made for the discharge of their contents lest their embankments give way; this can only be done by considering their volume and calculating the velocity and consequent quantity which will reach the dam at any one time. It would be well, after having ascertained the greatest known flood to be passed, to exceed this as a factor of safety, for almost every masonry dam has at some time been topped by a flood greater than calculated for. Having fixed on the area of the wasteway from a knowledge of the maximum flood to be discharged, the chief consideration to be borne in mind is the relation of its depth to its length. A long wasteway may permit the loss of too great a volume of water if exposed to the action of the wind, whereas a short one renders it necessary to give the dam an increased height in order that it may have the required capacity. The depth of the waste- way will be largely regulated by the probable wave-height, and this will depend on the depth and fetch of the reservoir (Art. 305). The difference in height between the crest of the dam and the wasteway will generally vary between 5 and 20 feet as limits. Care should always be taken, in designing a wasteway, rapidly to increase the slope of its bed immediately below the crest of the waste weir, so that there shall be no piling or banking up of water to retard the discharge. A quick drop beyond the crest considerably enhances the discharging capacity. . 368. Discharge of Waste Weirs. For the calculation of discharge the wasteway can be considered as a measuring weir subject to the weir formulas. If the crest of the wasteway has a sharp square edge or falls away with considerable suddenness CLASSES OF WASTEWAYS 483 on the lower side, Francis' formula (Art. 90) may be applied with approximate results, and we have <2 = 3-33('-.i^ ! (i) The mean velocity of flow over the crest is v = %V~2gh, and multiplying the depth of water on the weir h into its length / we get the volume of discharge. When the overfall from the crest is not sudden <2 = 5-35.-i;r P^N. 3N PLATE XXXVIII. Outlet Gates, Roosevelt Dam, Arizona. 506 WASTEWAYS AND OUTLET SLUICES wheel takes the place of the ordinary crank, rendering the gate easily handled under the maximum head of 25 feet. 381. Electrically Operated Outlet Gates, Roosevelt Dam. The outlet tunnel passes around the left end of the dam through the solid quartzite cliff. It is 490 feet long, 12 ft. wide, and 10 ft. high, its bottom being 240 feet below the dam crest. Above the gates the tunnel widens to a gate chamber 19 J ft. wide, which is divided into three channels by two piers made of hollow cast- steel columns, filled with concrete, in which the service and emergency gates are supported (PL XXXVIII). Over the gate chamber is a gallery of about the same dimensions, divided into rooms by partitions, and containing recesses into which the gates are raised. The service gates for regulating outflow are near the down- stream end of the chamber, and the emergency gates for use in repairs are 10 feet further up-stream. The gates are each n ft. 6 in. high by 6 ft. 4 in.wide, of cast iron sHding in cast-steel guides. The shell of each is 2\ inches thick and is strengthened with ribs of equal thickness spaced 12 inches centers and of 13 in. depth. Each gate weighs 10 tons complete and is surrounded by a bronze facing on all edges, as is also the gate frame. The gate and frame each have roller tracks parallel to the gate body but sloping away from the gate seats in opposite directions with a batter of i in 30. When the gate is closed the battered faces are in contact and the gate seats bear the pressure. The rollers are of Tobin bronze, each 4 in. diameter and 5 T 9 ^- in. long, and in each train are 31 such rollers spaced 3 T 3 g- inches apart. Each gate is under 800,000 Ibs. pressure, and is raised and lowered from a hydraulic cylinder, in an overhead chamber, operating under a maximum pressure of 700 Ibs. per sq. in., by a bronze lifting rod 6 in. diameter and 32 ft. long. Each cylinder is operated by an electrically actuated pump outside the dam, serving through two pipes. 382. Unit Cost of Construction. The cost of construction on contracts for the Reclamation Service is set forth in Art. 422. WORKS OF REFERENCE 507 Earth Embankments: Excavation 25 to 60 cts. cu. yd. Embankment 20 to 50 " " Riprap $1.50 to $2.00 sq. yd. Puddle $0.50 to $i .25 cu. yd. Dry paving $2.00 to $3.50 sq. yd. Sodding 20 to 50 cts. sq. yd. Masonry Dams: Earth excavation $ 0.25 to $ 0.60 cu. yd. Rubble masonry (nat. cem.) $3.501085.00 " " " (Port, cem.) S 4.00 to $ 6.50 ' Brick masonry (nat. cem.) Sio.oo to S 15.00 " " Dimension stone for works $15 .00 to S 20.00 " " Rock excavations $ i.oo to S 2.50 " Concrete masonry (nat. cem.) $ 4.00 to $ 5.50 " " (Port, cem.) $4.501087.00 " " Rockfaced ashlar $10.00 to $30.00 " " Pipes, Cost per Foot (including fitting and laying): 12" 1 8" 24" 36" 48" 60" 72" Cast-iron $1.60 $2.75 $4.00 $7.00 $12.00 $16.00 $22.00 Steel-riveted 0.60 1.50 3.00 5.00 6.75 8.50 10.00 Wooden stave 1.20 2.00 3.25 5.00 5-25 9-5 I2 - 2 5 Artesian Wells per Foot: 2 in. wells, $0.50 to $1.00, for 300 ft. to 1000 ft. 6 to 8 in. wells, below 500 ft., $2.00 to $3.00. 6 to 8 in. wells, up to 1500 ft., $3.00 to $6.00. Loose material less than rock for shallow and more than rock for deep wells. 383. Works of Reference. Storage Works. BAKER, IRA O. A Treatise on Masonry Construction. John Wiley & Sons, New York, 1890. BOVEY, H. T. A Treatise on Hydraulics. John Wiley & Sons, New York, 1895. BUCKLEY, R. B. Irrigation Works in India and Egypt. E. & F. N. Spon, Lon- don, 1893. CHURCH, IRVING P. Mechanics of Engineering. Fluids. John Wiley & Sons, New York, 1889. CLERKE, SADASEWJEE and JACOB. Impounding Reservoirs in India. Trans. Inst. C. E., No. 2730, London, 1894. FANNING, J. T. Hydraulic and Water-supply Engineering. D. Van Nostrand & Co., New York, 1896. FRANCIS, J. B. High Walls or Dams to Resist the Pressure of Water. Trans. Am. Soc. C. E., New York, vol. xix, 1888. FTELEY, A. Report of Chief Engineer of Croton Aqueduct Commission, New York, 1895. GOULD, B. SHERMAN. Contract and Specifications for Building a Masonry and Earthen Dam. Engineering News Pub. Co., New York. HALL, WM. HAM. Irrigation in Southern California. Report as State Engineer of Cal. Sacramento, 1888. HOBART, E. F. Reservoir at Santa Fe\ N. M. Trans. Am. Soc. Irrigation En- gineers, Denver, Col., 1893. 508 WASTEWAYS AND OUTLET SLUICES JACOBS, ARTHUR, and GOULD, B. SHERMAN. The Designing and Construction of Storage Reservoirs. D. Van Nostrand & Co., New York, 1888. KRANTZ, J. B. A Study on Reservoir Walls. Translated by F. Mahan. John Wiley & Sons, New York, 1883. MACKENZIE, A. T. History of the Periyar Project. Superintendent of Govern- ment Press, Madras, India, 1899. McCuLLOH, W. The Construction of a Water-tight Masonry Dam. Trans. Am. Soc. C. E., vol. xxviii, New York, 1893. MCMASTERS, JOHN B. High Masonry Dams. D. Van Nostrand & Co., New York, 1876. MERRIMAN, MANSFIELD. Text-book on Retaining Walls and Masonry Dams. John Wiley & Sons, New York, 1892. Reclamation Service, U. S. Annual Reports. Washington, D. C. RONNA, A. Les Irrigations. 2 vols. Firmih-Didot et Cie, Paris, 1889. SCHUYLER, JAMES D. The Use of Asphaltum for Reservoir Linings. Trans. Am. Soc. C. E., vol. xxvii, New York, 1892. SCHUYLER, JAMES D. Reservoirs for Irrigation, Water Power, etc. John Wiley & Sons, New York and London, 1901. STANTON, ROBERT B. Notes on the Construction of a Water-tight Masonry Dam. Proc. Am. Soc. C. E., vol. xxii, New York, 1896. TURNEAURE, F. E., and RUSSELL, H. L. Public Water Supplies. John Wiley & Sons, New York, 1901. UNITED STATES GEOLOGICAL SURVEY, i2th, i3th, and i8th Annual Reports. Gov- ernment Printing Office, Washington, D. C., 1891, 1892, and 1897. VISCHER, HUBERT, and WAGONER, LUTHER. On Strains in Curved Masonry Dams. Trans. Tech. Soc. Pacific Coast, vol. xi, 1890. WEGMANN, EDWARD, JR. Design and Construction of Dams. John Wiley & Sons, New York, 1*907. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. CHAPTER XIX PUMPING, TOOLS, AND MAINTENANCE 384. Pumping or Lift Irrigation. The methods of irri- gating so far considered are those in which the water is brought to the irrigable land by gravity or natural flow. There are large volumes of water situated at such a low level that gravity will not carry it to the fields, and this water must be raised by means of pumps or other lifting devices. Pumping may be employed to utilize the water from wells or from natural streams flowing at a lower level than the land irrigated, or may be em- ployed to raise water from low-service canals to others at higher levels. When the gravity sources of supply have been entirely util- ized large areas of land may still be brought under cultivation by the employment of pumps. As irrigation is practised, the subsoil becomes saturated, the ground- water level is raised, and much of the water delivered by gravity systems thus finds its way by seepage from the fields into the soil and may be pumped up and re-employed in irrigation, thus greatly adding to the duty of the ultimate sources of water-supply. The value of pumping for this purpose has been recognized in the older European and Asiatic countries for ages, and a large proportion of the irriga- tion in Europe, China, Japan, India, and Egypt is by means of lifting (Article 116). In Oriental lands lifting is performed almost wholly by animal or man power, through various ancient devices operated chiefly by bullocks or men. In Italy quite a deal of pumping is done by machinery, chiefly to raise water from existing low-level canals to high-service canals. In our country the value of pumping as a means of irriga- tion is scarcely yet appreciated. A few windmills and water- 509 510 PUMPING, TOOLS, AND MAINTENANCE wheels are utilized for this purpose, and a small amount of pump- ing is done by steam-power, though the value of the water-supply to be derived from these modes of lifting is sure to increase greatly in the near future, when its cheapness and adaptability come to be fully recognized. The Reclamation Service is providing for the utilization of water power, electric-ally transmitted, for pumping water from wells in the irrigable lands of the Salt River and other projects (Art. 117). A perusal of this chapter will show that pumping as a mode of supplying irrigation waters, far from being more expensive than water derived from gravity supplies, generally furnishes water more cheaply than do gravity supplies, both in the matter of first cost of the pumping or gravity plant or the equivalent cost of water right (Tables I, XVII, and XXIII), and in the matter of the cost of maintenance and operation, equivalent in the gravity supply to the annual water rental or rate paid. Moreover, the source of water-supply is more directly under control of the irrigator, and he is troubled by none of the vexatious questions of priority of right, tatils, etc. 385. Motive Power and Pumps. Pumps are machines for elevating water, and consist of two principal parts: (i) the pumping or water-elevating mechanism, and (2) the motive power by which this is operated. Pumps may be divided into four general classes, according to the principle on which they raise the water. These are : 1. Lift-pumps. 2. Force- or plunger-pumps. 3. Rotary and centrifugal pumps. 4. Mechanical water-elevators. Lift- and force-pumps may be combined, and may be either reciprocating or rotary, in which latter case they come under class three. All may be single- or double-acting. The motive power may be : 1. Animal-power. 2. Wind-power. 3. Water-power. 4. Hot-air or gas engines. MOTIVE POWER AND PUMPS 511 5. Steam-engines. 6. Hydro-electric. The above classes of pumping machinery are nearly all in- terchangeable. Thus lift, force, and centrifugal pumps and mechanical elevators may nearly all be operated by any of the various motive powers, though not by all of them. Distinguished from these there are three additional classes of pumping mechanisms in which the motive power and pump are inseparable. These are: 1. Injectors, vacuum-pumps, and pulsometers, in which steam is the motive power. 2. Hydraulic rams and hydraulic pumping-engines, in which water is the motive power. 3. Siphons and siphon elevators, in which atmospheric pres- sure is the motive power. Lifting-pumps operate by drawing water through a suction- pipe as the pump bucket ascends; the water is forced through a valve in the bucket as the plunger descends, and is then again lifted as the bucket reascends. This variety of pump is de- pendent for its operation on the creating of a partial vacuum below the pump bucket by atmospheric pressure. Force-pumps draw water through a suction-pipe as do lift- pumps, but the water is raised above the bucket by the action of a piston or plunger which forces it through a delivery valve. Force-pumps may be single- or double-acting, and nearly all steam-pumps -are of the latter variety, the discharge of these being practically continuous, for as the water is drawn in at one end it is forced out at the other. Centrifugal pumps depend for their action on a disk to which are attached propeller-blades revolving inside a chamber. These propeller-blades create a partial vacuum which lifts water into the chamber by suction, whence it is forced by the following propeller-blade. Rotary pumps are practically revolving piston- pumps, differing from the latter chiefly in that they are not direct- acting. Mechanical water-elevators include the various patented de- vices in which water is raised by means of disks or buckets ar- 512 PUMPING, TOOLS, AND MAINTENANCE . ranged on a revolving chain; also chain-pumps, Archimedean screws, Persian wheels, norias, the common well-sweep, which is the paecottah of India and the sakia of Egypt; and many other curious devices. All the motive powers except wind may be used to operate any of the various classes of pumps. Ordinarily, however, animal power is used to operate the lighter forms of pumping machinery which are intended to elevate small quantities of water and the common lift- and force-pumps and mechanical elevators of various kinds. Wind is employed almost exclusively for the operation of lift- and force-pumps, as it is too uncertain in its action to work well with centrifugal pumps or mechanical elevators. The various steam powers may be divided into two gen- eral classes, according to the manner in which they are attached to the pumps. These are: 1. Direct-acting steam pumps. 2. Fly-wheel and belting steam pumps. Direct-acting pumps have no rotary motion, their action being reciprocating, and both steam- and water-cylinders being mounted on a solid bed-plate, so that the piston-rod which pro- duces the power has attached to it the plunger which elevates the water. Fly-wheel or indirect- acting pumps may have the motive power at some distance from and independent of the elevat- ing pump, and be connected therewith through shafting or belting or some other mechanical device. They are not so satisfactory or reliable in their operation where used for irrigation, as they are liable to get out of alignment and out of order, and therefore require more skilled attendance than do direct-acting pumps, though, on the other hand, their efficiency is generally higher. 386. Choice of Pumping Machines. The pump and mo- tive power which are to be employed in each particular case depend wholly on the services to be performed and on various local modifying conditions. The variety of pump must be chosen according as greater or less volumes are to be elevated to greater or less heights. The motive power must be selected according to the pump chosen, the work to be done, and the CHOICE OF PUMPING MACHINES 513 fuel available, be this air, water or wood, coal, gasoline or elec- tricity. Where means are limited and the area to be irrigated is but a few acres, the motive power chosen will usually be either animal or water. The first is cheapest of installation but least economical, and the second is next cheapest, where a sufficient water-supply is available for the operation of an ordinary mid- current undershot wheel or hydraulic ram. Where the area is small but the means at the disposal of the irrigator less limited, animal power will usually be left out of consideration, and the choice rest between wind, water, hot air, gasoline, alcohol, electric or steam pumping-engines. If the wind be reasonably steady and the facilities good for the construction of a storage tank, that power, though not less expensive to install than some others, is least expensive and troublesome to maintain and operate, yet not the most reliable. Where water is abundant, it furnishes, through rams, water-wheels, turbines, or water-engines, the next least ex- pensive power to maintain and operate, though not the cheapest to install. The class of water-motor selected will depend wholly upon the volume of motive power available and the height to which the water is to be raised. Hot-air engines and gasoline- engines furnish the most reliable power for pumping water, and are less difficult to operate than steam-engines. Gasoline or alcohol engines are especially economical where coal or wood as fuel are expensive, though hot-air engines have a wide adapta- bility in the variety of fuel which they may utilize. Steam-engines, where coal is cheap, furnish the most satisfactory motive power, but are generally not so economical to operate, especially where small areas are to be irrigated. For the pumping of large vol- umes, water and steam are the only competing motive powers. Where water power is available at some distance from the wells to be pumped, it can often be converted into electricity and thus be transported long distances at relatively low cost. The irrigation engineer who proposes installing a pumping plant should consider all the various circumstances which affect the case under consideration. He should carefully weigh the necessity for having a permanent and steady supply, the inac- cessibility of the plant for repairs or replacement of broken parts, 33 514 PUMPING, TOOLS, AND MAINTENANCE the relative cost and accessibility of different kinds of fuel or of water, and the degree of intelligence and skill possessed by those who are to operate the machine employed. 387. Animal Motive Power. There are numerous modes of utilizing animal power in pumping water. Among the oldest and best known of these are the common domestic hand pump, the well-sweep, and the curb and bucket, which are all too limited in capacity for use in irrigation. More extended in use is the Persian wheel and some of its American adaptations which have recently come into use in this country. There are several varieties of this apparatus skilfully designed and constructed which are more efficient than the old Oriental wheel. These have large metal buckets hung on heavy linked chains which revolve over the wheel and dip into the source of water-supply beneath, and are operated by iron cogged gearing turned by horses or bullocks attached to a shaft from the center of these and walking around in a circle. These have capacities varying between 500 cubic feet per hour for one horse up to 2000 cubic feet per hour for four horses for a depth of 20 feet, the first cost for plant ranging from $200 to $500. There are on the market a number of mechanical devices for utilizing animal power in pumping water, consisting chiefly of various forms of sweeps to be drawn by horses walking in a circle, or treadmills for utilizing horse, bullock, or sheep power, through gearing and shafting. Most of these are simple in construction and operation, are not liable to get out of order, and are with their pump connection capable of lifting sufficient water with a two-horse device to irrigate three to five acres per season without storage, while this amount could be at least doubled if a storage tank of sufficient capacity were provided for retain- ing water raised during periods when it is not wanted for im- mediate use. Of the older mechanical devices for lifting water for irriga- tion there may be enumerated, as among the more prominent, the mot of India, which consists of a rope passing over a pulley down into the well, and to the end of which a bucket or other receptacle is attached. This is raised by two bullocks walking WINDMILLS 515 away with the rope, usually down an incline, thus raising the bucket to the top of the well, where it is emptied into a distrib- uting ditch. The Persian wheel is perhaps the most commonly employed of the various devices, both in India and generally throughout Asia and Egypt. It consists of a vertical wheel to the outer rim of which are either attached buckets which dip into the well or over which is hung a rope which hangs below the lower periphery of the wheel and to which buckets are at- tached, and as these reach the upper circumference of the wheel they spill their contents into a trough which leads the water to the fields. Another old-fashioned water-lifting device is the paecottah of India, which is the sakia of Egypt and the bascule of Europe and the common well-sweep of America. By its use from 500 to 2000 cubic feet of water are raised in a day. With the mot two bullocks working 10 hours a day will raise 3} acre- feet in a season of 90 days. With the Persian wheel two bullocks will lift 2000 cubic feet of water a day. Still other devices of this kind, and worked like the well-sweep by man power, are the latha or scoop of India and China, the double-zigzag balance of Asia Minor and Egypt, the well chain, the noria, the tympan, and the Archimedean screw. 388. Windmills. Windmills are being extensively used in the San Joaquin valley in California, and on the great plains east of the Rocky Mountains and in other portions of the West, for pumping water for irrigation. They have been most ex- tensively employed for pumping water for domestic use, but as the necessity for irrigation has become better appreciated, and as water has become more scarce and valuable, .windmills have come into more extended use in providing water for irri- gation. The chief objection to windmills for this purpose is their unreliability, as they are wholly dependent upon the force of the wind for their operation. This objection is not so seri- ous on the great plains between the Rocky Mountains and the Mississippi River, where there is almost always a sufficiently steady and powerful wind to keep mills constantly turning. In other places they are less certain in their action, and may fail the farmer at the very time when he is most in need of a water-supply. PUMPING, TOOLS, AND MAINTENANCE Because of their uncertainty of operation, windmills should never be used for purposes of irrigation without providing as an adjunct an ample tank or reservoir for the storage of suffi- cient water to irrigate a considerable area. As the wind may blow at any time during the twenty-four hours, and is just as likely to blow at night as in the day, when the water cannot be used in irrigating the fields, a storage capacity sufficient cer- tainly to impound water pumped during the night-time should be provided; though for any security, and in order to irrigate a reasonable area, ample capacity should be provided to store the water of several days' pumping when irrigation may not be neces- sary. This storage capacity may be obtained by using one of the various forms of elevated tanks which are supplied by wind- mill makers; or, better still, if the windmill can be located at a high point on the farm, an artificial reservoir may be excavated at this point and suitably lined, which shall have capacity to contain a much larger amount of water. 389. Capacity and Economy of Windmills. The amount of work which a windmill will perform depends on two prime considerations: (i) the force and steadiness of the wind, and (2) the size of the wind-wheel. It requires on an average a wind velocity of not less than 6 miles an hour to drive a windmill, and on an average winds exceeding this velocity are to be had during eight hours per d,ay. Hence, about two-thirds of the total wind movement is lost for work. The reports of the U. S. Weather Bureau indicate that the average wind movement of the entire country is 5769 miles TABLE XXVI. WIND VELOCITY AND POWER. Miles per Hour. Feet per Second. Pressure per Square Foot, Miles per Hour. Feet per Second . Pressure per Square Foot, in Pounds. in Pounds. 6 7-5 .12 3 44-0 4-4 10 14.7 5 35 5!-3 6.0 15 22.0 i.i 40 58.8 7-9 20 2Q-3 2.0 45 66.0 10. 2 5 36.7 3-i 5 73-3 12-3 CAPACITY AND ECONOMY OF WINDMILLS 517 per month, or about eight miles per hour. These averages are somewhat exceeded in Dakota, where the average hourly velocity is ten miles; also in Nebraska, Kansas, and neighboring States; while they are too great for other portions of the arid West. The preceding table gives roughly the force of the wind for ordinary velocities: The following table is derived from Mr. A. R. Wolff's ex- cellent work on the windmill, and shows the capacity and econ- TABLE XXVII. CAPACITY OF WINDMILLS. t> "O&H Revolu- Gallons of Water Raised per Minute to an Elevation of Horse- 8-3 tions of Wheel. Devel- oped. 25 Feet. 50 Feet. 75 Feet. TOO Feet. 150 Feet. 200 Feet. 10 60 to 6<; 19.2 9-6 6.6 4-7 0. 12 12 55 6 33-9 17.9 ii. 8 8-5 5-7 .... 0.21 14 5 55 45- r 22.6 !5-3 II. 2 7-8 4-9 0.28 16 45 5 64-6 31-6 19-5 16.1 9-8 8.0 0.41 18 40 45 97-7 52.2 32-5 24.4 '7-5 12.2 0.61 20 35 40 124.9 63.7 40.8 31.2 19-3 15.9 0.78 25 30 35 212.4 lOJ.O 71.6 40.7 37-3 26. 7 '-34 omy of an experimental windmill having various diameters of wheels, with an assumed average velocity of wind of 16 miles per hour and with eight hours per day as the average number of days during which the results given may be obtained. Mr. Wolff estimates the cost of operating a windmill for a 25-foot lift, including interest on first cost and charges for main- tenance, as ranging from seven-tenths of one cent per hour for a 10- foot wheel to 24 cents for a 1 6-foot wheel and 43 cents for a 25-foot wheel. Aside from the uncertainty of action in windmills, it is evi- dent from the foregoing that the windmill is one of the most economical of prime movers. Its operation calls for no expense for fuel, practically none for attendance in self -regulating mills, and little or none for repairs. In comparison a steam-engine calls for large expenditures for fuel, repairs, and attendance, while most 518 PUMPING, TOOLS, AND MAINTENANCE classes of water-motors call for heavy expense in providing and maintaining a supply of water, as well as for attendance and repairs. On an average it appears that the economy of a wind- mill is at least 1.5 times that of a steam-pump, while it has an additional economy over the latter because of the attendance and repairs demanded by the steam-boiler. On the other hand, a windmill usually calls for additional expense where it is used for irrigation in making its supply more certain by providing storage capacity. Some interesting comparisons of the efficiency of various windmills have recently been made by Mr. J. A. Griffiths in Australia. The mills experimented with were situated in the ordinary manner directly over a well, reciprocating pumps being attached directly from a crank on the main axle of the sail-wheel, the latter being erected on the usual wooden mill-tower. Mr. Griffiths assumes the following equation of energy required to stop and start a stream as being (i) in which A is the sectional area in square feet of a stream of air weighing W pounds per cubic foot, and moving with a uni- form velocity of v feet per second. In computing the efficiency of windmills the unit adopted is usually 100 square feet cor- responding to a circle of 11.3 feet diameter, or about that of the smallest windmills ordinarily employed, and the unit of velocity is 10 miles per hour. A uniform stream of air of 100 square feet sectional area, weighing .075 pound per cubic foot and moving with a velocity of 10 miles per hour, contains an actual kinetic energy of 1,323,267 foot-pounds per hour, or .6683 of an English horse-power, and from this coefficient the energy of any other stream may be calculated. In the following table are given horse-powers of wind acting upon an area of 100 square feet for velocities ranging from 5 to 30 miles an hour. The highest net efficiency observed in Mr. Griffiths' experi- ments at 7 miles per hour was twenty-five per cent; also, that the velocity of the wind when leaving the mill was '.909 of the VARIETIES OF WINDMILLS 5*9 approaching velocity. He further observed that the loss of ve- locity was proportionately less than the loss of energy, and that with a working efficiency of 10 per cent or less the loss of velocity was scarcely appreciable. TABLE XXVIII. ENERGY OF WIND ACTING UPON A SURFACE OF IOO SQUARE FEET. Ve S. f AtSea-,.vel. At 1000 Feet above Sea-level. At 2000 Feet above Sea-level. Miles per Hour. H.-P. H.-P. H.-P. ^ o.o83S 0.0780 0.0724 10 0.6683 0.6237 0.5792 15 2-2550 2.1050 1-9550 20 5-3470 4.9900 4.6340 2 5 10.4400 9-7460 9.0^00 30 18.0400 16.8400 15.6400 In designing a windmill for pumping, two things have to be considered the torque, or statical turning moment, and the speed of the wheel in relation to that of the pump. The for- mer should be as large as possible so that the mill will start with the faintest wind, and the latter must not be too fast for the pumps in a small mill or too slow in a large one. Hence the size of a mill is an important element in the arrangement of its vanes. The angle between any portion of a vane and the plane of the wheel is termed the weather angle, and to obtain the greatest torque at starting the weather angle should be the complement of the best incidence angles, or between 70 and 55 degrees. In practice it is found that the weather angle is never as great as this, being in the best examples about 43 degrees. The following table gives the results of Mr. Griffiths 1 ex- periments for the five American-made windmills tested. 390. Varieties of Windmills. A wind-wheel is designed for the utilization of wind-power much as is a water-wheel for that of water-power, but differs from it in that the former is wholly immersed in a sea of air while the latter is acted upon by a limited current of water. The common paddle-wheel will not be revolved by the wind, because its force is exerted equally on diagonally opposite paddles; hence the paddles on 520 PUMPING, TOOLS, AND MAINTENANCE X w G / % w ill CO 00 vO ** t- W 10 O m o O T 00 NJ W CNl O O O t^ CNl 10 rl- (N O t~- "J ON O O ^ O Tj-00 10 ro vO M O O O M M to O O N * o o o o t III 2-3 NO co who "H 00 Tf t>- 00 10 (N ro to 10 O O O 00 f> CN - |3s 9 *1 d to M co X od H 00 cs ro co 00 O O O ON to O O c^ H H t^ O O O ON IO 00 O O O to to O M 00 ON M M 10 s^- 3 i * ^t t- O v ^ H LO PO A\o H CO 4 s * N O O ON .0 lA CNl O O M Tt to T3 *-; o "3' LJ CO (t V 526:2 00 IT o *H rf N M H O 10 O O ON c?0 O O to to M CNl to O i- 1 O O H t- ill >O O M \O v O M o co/^ ro cs fO O t^ O O 00 ON O O O^O^Q< AT MAXIMUM EFFICIENCY. Velocity of wind, miles per hour Velocity of mill, revolutions per minute Actual horse-power Horse-power per 100 square feet of gross a Maximum net efficiency, per cent IN 100 AVERAGE HOURS, CALM LOC Average quantity of water lifted, gallons pe Average continuous horse-power developed Average continuous gross horse-power deve Average net efficiency, per cent IN 100 AVERAGE HOURS, WINDY LO Average quantity of water lifted, gallons p< Average continuous horse-power developed Average continuous gross horse-power devt Average net efficiencv, per cent VARIETIES OF WINDMILLS 521 one side only should be exposed to the wind a result which is obtained without the use of a screen by pivoting the paddles upon their axis so that on one side they present a broad face to the wind and in passing to the other side they turn on their pivots so as to present a feather edge to the wind. Windmills consist of arms, cross-bars, and clothing therefor. They are made plane, warped, or concave. The older type of sail-mill is common in Europe, especially Holland, and has usually four arms, occasionally more. The narrow part of the sail is usually covered with a wind-board, as it is called, and the broader with wind slats of wood or with a covering of sail- cloth. American mills differ from European mills in that they are chiefly of the propeller type, and instead of a small number of sails of considerable width are made with a great number of blades or slats of slight widths, and otherwise have an entirely distinct appearance from the European mill, as the wheel pre- sents a closed surface as compared with the large open spaces between the arms of the sail-mill. As a result of this mode of construction the American mill is lighter in weight as well as appearance than the European mill; and though the wide angle of the vane is not as advantageous as in the sail-mill, the sur- face presented for a given diameter is sufficiently great to more than compensate for this difference, and it would appear that the American mill is superior to the European type from the fact that it is rapidly replacing them in Europe. The several types of American mills are distinguished both by the form of the wheel and the mode of regulating or gov- erning its position and direction so as to obtain a uniform power and rate of revolution under varying wind velocities. There are two principal types of these mills, namely, (i) sectional wheels with centrifugal governor and independent rudder, and (2) solid wheels with side-vane governor and independent rudder. Be- sides these there are a number of special types, including various combinations of solid and sectional wheels with various arrange- ments of rudder, or in some cases no rudder is employed, and the wind pressure upon the wheel is relied on to bring it into direction. 522 PUMPING, TOOLS, AND MAINTENANCE The windmill is usually placed directly over the well on a wooden or iron tower or scaffolding, having usually four upright inclined pillars which straddle the well. This tower should be sufficiently high to raise the wheel at least 20 feet above all ob- structions, as buildings, trees, etc. This may require a tower, preferably of steel; 50 to 70 feet high. A small wheel on a high tower is better than a large wheel on a low tower. At the top of the scaffolding is a platform or a turntable with an open center, through which the pump-rod descends vertically to a recipro- cating force-pump in the well. A horizontal crank-shaft sup- ported in bearings on the upper movable part of the turntable is connected with the pump by a swivel- joint in order to permit of the rotation of the mill top necessary in adjusting the sails to the various horizontal directions of the wind. An overhang- ing end of the crank-shaft carries the wind-wheel, which in some forms is on the lee side of the tower, in which case it maintains its direction perpendicular to the wind by pulling the turntable around, and is rudderless. In others the pressure of the wind on a rudder vane with sufficient area and leverage to overbalance the wind keeps it perpendicular to the wind, and on the wind- ward side of the tower. In addition there is also a controlling or regulating gear to stop the mill when the reservoir is full or repairs are necessary, and to prevent damages by gales. This gear is operated by hand or is automatic. Of side-vane governor mills the Corcoran and Eclipse are excellent examples. Of centrifugal governor mills the Halla- day and Althouse are good examples. The latter is folding and rudderless. Of special mills the Buchanan is a good ex- ampb, being dependent for its regulation on the tendency of the wheel to go into the direction it turns as the velocity of the wind increases. The Stover is a solid sail-wheel with vanes so regulated that the mill may be reefed or even stopped or other- wise regulated to go slowly in heavy winds. The Perkins mill has a solid wheel with automatic rudder, which also acts as an automatic regulator, though in slow winds it must be half reefed. The Carlyle special mill has a rudder arranged to reef the sail in storms, and so attached by an adjustable cam as to cause VALUE OF WINDMILLS AS IRRIGATING MACHINES 523 the center of gravity of the rudder to rise as it falls toward the wheel. The Leffel windmill depends for regulation on the fact that the center line of the wheel shaft stands off from and parallel to the plane of the rudder, while the wheel of the mill is of peculiar type, being made of metal blades with a helical curve. The Aermotor Cyclone and Woodmonse are excellent types of modern American mills. The Advance is a good type of automatic regulating rudder mill having both side steering-vane and govern- ing rudder. 391. Value of Windmills as Irrigating Machines. Wind- mills average in cost from $50 to $400, according to size and make. Any one intending to use a mill should purchase it from a reliable maker, and choose a design according to the work which the mill is expected to perform and the average wind veloc- ity in his locality. Thus, on the Rocky Mountain plains a wind- mill will run at least twelve hours in a day, while in some of the mountain valleys between the Rocky Mountains and the Pacific slope eight hours per day is an average run. Experience with average mills already constructed shows that a 5-inch pump will discharge about 250 cubic feet an hour, a 6-inch pump about 380 cubic feet per hour, and an 8-inch pump about 650 cubic feet per hour. On the average basis of duty of water a 5 -inch pump will therefore irrigate about 6 acres if running constantly or about 2 acres if running one-third of the time. Recent experiments by Prof. E. C. Murphy show that the power of windmills does not increase much faster than the square of the wind velocity, and about as i| times the diameter of the wind-wheel. A good 1 2-foot steel mill should furnish i horse- power in a 2o-mile wind and 1.4 horse-power in a 25-mile wind. A 1 6-foot mill will furnish 1.5 horse-power in a 20- mile wind and 2.3 horse-power in a 25-mile wind. The average mill will, according to experience, do sufficient work to irrigate from i to 3 acres. If, however, a storage reser- voir or tank be supplied this may be emptied and filled several times during an irrigating season, which contains several irri- gating periods, and a mill supplied with such a reservoir may therefore irrigate from three to five times the area above indicated. 524 PUMPING, TOOLS, AND MAINTENANCE There are numerous windmills in the West which irrigate from 10 to 15 acres from wells 30 to 150 feet in depth with the aid of storage tanks, and these plants, including mill and tank, average in cost from $150 to $350. Taking $250 as a mean and their capacities at 12% acres, the cost of these plants is about $20 per acre irrigated and the cost for maintenance practically nil. A 2 5 -foot mill will, according to Table XXVII, in a working day of 8 hours, pump one-third of an acre-foot to a height of 25 feet, or one-sixth of an acre-foot to a height of 50 feet. In an irrigating season of 120 days it will raise 40 acre-feet to the lower elevation, and were storage provided for half this volume and the reservoir filled before the beginning of the irrigating season, such a mill would theo- retically, under average wind conditions, be capable of furnish- ing enough water to irrigate from 20 to 30 acres. It is doubt- ful, however, if such a duty will be practically obtained even with the most ample storage facilities. 392. Power in Falling Water. Water acts as a motive power by its weight or by its impulse. In the former case it falls slowly through a given height, and in the latter it passes through a machine with a constantly decreasing velocity. The work P which it performs because of a given fall h is P = Qwh, ...... (2) in which Q is the whole quantity of water falling in one second of time and w the weight of a unit of volume. If v is the velocity with which it enters, then the work which it performs because of impulse, before coming to rest, is but water started from rest will attain a velocity v only after it v 2 has passed through a height h = ; hence in the latter case the formula may be written as is (2). The following simple graphic mode of determining the horse- power which is contained in any given waterfall was published by Prof. Olin H. Landreth in Engineering News. It is based POWER IN FALLING WATER 5 2 5 on the formula HP = Hqwe 500 , in which H is the effective head on the wheel in feet, q the quantity of water in cubic feet per second, w the weight of water per cubic foot, and e the percentage of efficiency of the wheel. For w = 62.4 Ibs.; HP = o.n^^Hqe. The inclined lines radiating from the zero at the lower left corner are of three different kinds: Those running to the upper edge of the diagram represent the quantity of water; those run- ning to the right side of the diagram represent the different per- centages of efficiency, except the one line which crosses the margin Water, Cu. ft. per. Sec. 30 30 40 60 30 40 60 Horse Power FIG. 191. Diagram for Determining Horse-power of Water-wheels and Water-falls. Example: Head = 15.6 ft. Quantity = 40 cu. ft. per sec. Efficiency = 75%- Then Horse-power = 53-2. between 85% and 90%, which is a conversion line to transform the resulting value of the horse-power into such linear values as to permit them to be represented by the graduations along the base of the diagram. This line is drawn at an angle with the vertical lines, whose tangent t = \ (0.1134) 75.^)^, where v and h are 526 PUMPING, TOOLS, AND MAINTENANCE the numerical values of the vertical scale of head and the hori- zontal scale of quantity, the J being introduced in this case to make the HP units along the base of the diagram one-half the value of the quantity units along the top edge of the diagram. To use the diagram: Start with the value of the head on the left margin, pass horizontally to the radiating line representing the given quantity, thence pass vertically down to the proper efficiency line, thence pass horizontally to the inclined conversion line, thence vertically down to the horse-power line along the base of the diagram, where the proper value may be read off. With heads or quantities in excess of the maximum value of the diagram, the scales may be assumed changed to ten times that graduated and the resulting horse-power read off to a scale either ten or one hundred times that graduated, according to whether one or both the argument scales have been amplified, one or two other arrangements of the lines indicating respec- tively the heads. 393. Water-motors. Hydraulic motors are machines de- signed to utilize the energy possessed by falling or moving masses of water, and may be divided into the following two classes: (i) water-wheels and (2) water-engines. These may be again divided into several classes, in some of which both water-wheels and water-engines act either through power due to fall or due to impulse, or a combination of both. Water-wheels may be sub- divided into two classes: (i) vertical water-wheels and (2) horizontal water-wheels. Of the former we have the more com- mon of the old-fashioned wheels: 1. Undershot water-wheels. 2. Breast- wheels. 3. Overshot water-wheels. 4. Hurdy-gurdies. 5. Pelton water-wheels. The latter is a modern adaptation of the old-fashioned hurdy- gurdy, and is properly an impulse wheel. Horizontal wheels are turbines of vorious types, and in these, like vertical wheels, water may act both by pressure or -impulse, or by a combina- tion of the two. UNDERSHOT WATER-WHEELS 527 Water-engines may be divided into three classes' 1. Bucket-engines. 2. Rams. 3. Water- pressure engines. The first is an antiquated form of motor by which work is performed by allowing water to enter buckets, thus causing these to descend vertically. Rams utilize the impulse due to the weight of a large body of water in forcing a smaller body to a desired height. Water-pressure engines utilize the fluid properties of water in a manner somewhat resembling the opera- tion of steam-engines producing a reciprocal motion through the pressure of water confined in an upright pipe. Assuming one has to elevate a given quantity of water to a fixed height, having at one's disposal a hydraulic force which it is desired to apply to the work, we may divide the problem into two parts: (i) The fall may be distinct from the water which is to be lifted, or (2) the question of fall may be inseparable from the water to be elevated. In the first class are included all water- wheels and bucket-engines; in the second are included rams and most forms of water-pressure engines. In either case it may be necessary to raise a large volume to a small height or a small volume to a large height, and each of these offices may be performed through a large volume of power from a small height, or a small volume of power from a great height. It is this intimate connection between volume and head of power and of resulting work which calls for the exercise of ingenuity and discretion on the part of the engineer in choosing the water-motor by which this work is to be done. Thus a ram is nearly always called upon to utilize a large volume of power from a small height to raise a small volume of water to a great height. The Pelton water-wheel generally utilizes a small volume of power from a great height to elevate varying quantities of water to varying heights. 394. Undershot Water-wheels. The word water-wheel is usually applied to the various old-fashioned vertical wheels, undershot, breast, and overshot wheels. Undershot wheels may be classified as midstream wheels, the common undershot 528 PUMPING, TOOLS, AND MAINTENANCE wheels, and Poncelet wheels. In midstream wheels the motive power is due to the velocity or impulse of the current of water in the stream in which the wheel is set, and such wheels are em- ployed almost exclusively for the elevation of water for irriga- tion. They are very simple in construction and operation, and may be advantageously employed where water is abundant, even in streams having the very slowest velocity of flow. Midstream wheels produce the greatest power for the smallest diameter of wheel when the float-boards are made straight, but not radial. They vary from 12 to 16 feet in diameter, but are not infrequently larger, the float-boards varying from 9 to 12 in number, while two of them at least should always be im- mersed at the same time. These float-boards project from 24 to 30 inches from the wheel-rim, and dip into the water about half of their depth. In rivers where the water-level fluctuates, the axle of the wheel is made movable on its supports to render it capable of being raised or lowered at pleasure to suit the height of water-level, and this is effected by resting one or both ex- tremities of the axle on floats. The horse-power of a midstream wheel may be calculated by the following formula from Mr. P. R. B jorling ; HP = (v vj .0028 A v, (4) in which v is the velocity of the stream in feet per second, v^ the mean velocity of the float-boards in feet per second, and A the immersed area of the float-boards in square feet. Numerous wheels of this class have been successfully em- ployed in pumping water for irrigation in various portions of the West. In some cases these wheels have attached to their outer rim a row of buckets (Fig. 173), which dip into the water as the wheel revolves, are thus filled, and then as they reach the upper portion of their revolution spill their contents into a trough which leads to the irrigating ditches. Such wheels are called norias, and are of very ancient origin, having been used for ages in all portions of the world most extensively, perhaps, in Egypt and Italy. At other times midstream wheels are sus- pended directly in the stream current, and by means of gearing UNDERSHOT WATER-WHEELS 5 2 9 or belting are connected with pumps which elevate the water for irrigation. Such contrivances have been employed in the West, one of which, on the Platte River, has a lo-foot wheel, 14 feet broad on the face. It runs a 3J-inch centrifugal pump, and is said to elevate 2\ second-feet of water to a height of 16 feet, or 5 acre-feet per twenty-four hours. FI 2. Undershot Water-wheel or Noria. The average diameter of the midstream water-wheel of the West varies from 10 to 20 feet and the length of the blade of the paddle is from 6 to 10 feet. Some wheels of this variety but of large size have been successfully employed notably on the Green River in Colorado which are from 20 to 30 feet in diam- eter. These are hung on wooden axles 5 inches in diameter, while their paddles dip 2 feet into the stream. They are used as norias, for on their outer circumference are buckets of wood hav- ing an air-hole in the bottom closed by a suitable leather flap-valve which permits the bucket to fill rapidly by forcing out the air. These buckets are 6 feet in length and 4 inches square, and have 34 530 PUMPING, TOOLS, AND MAINTENANCE a capacity of a little less than a cubic foot each. The largest of the wheels on the Green River have 16 paddles and lift 10 cubic feet of water per revolution, and as they make two revolu- tions a minute, though they spill a large portion of their contents, each wheel handles about 4000 cubic feet per day, or approxi- mately TO" of an acre-foot. Common undershot water-wheels, as distinguished from mid- stream wheels, are the best where a fall of convenient height cannot be obtained, and the velocity of the water is yet relatively great. These are confined in a channel which is made about the width of the wheel and is wider at the inlet than at the wheel so as to give freedom of access to the water and to increase its velocity. These wheels operate most satisfactorily where the fall is from -|- to 2 feet in the course of the race. The paddles are similar to those for midstream wheels, though sometimes they are curved and of iron. The number of float-boards or paddles for such a wheel may be determined by the formula dd n = - + 12, (5) o in which n is the number of float-boards and d the diameter of the wheel. These wheels vary in diameter from 10 to 20 feet, and are usually constructed of from 30 to 40 paddles, varying from ij to 2j feet in depth, their length being from 3 to 6 feet. The power developed by such a wheel may be ascertained by the formula HP = .ooo6qh (6) in which is the quantity of water in cubic feet per minute and h the head of water in feet. Poncelet wheels act rather on the turbine principle, their paddles being curved. They are usually immersed to the height of their axes, and the water is screened from them with the ex- ception of a few inches near their under surface, so that it im- pinges by impulse against the under side of the wheel and acts much as does a turbine. The power they are capable of generat- ing may be expressed by the formula HP = .o6Sqh . (7) OVERSHOT WATER-WHEELS 531 Breast-wheels are placed where there is a considerable fall in a manner similar to Poncelet wheels, so that the level of water is about at the height of their axes. They have usually curved paddles or buckets, and the water impinges against them both by weight and impulse at a point just below the axial line. 395. Overshot Water-wheels. Overshot wheels are more economical in their use of water, and are therefore employed where water is scarce. In these the water is delivered above the wheel by means of a flume, race, or penstock, and they are so constructed that the water may be delivered either on the near or the far side of the wheel, according to the arrangement of the outlet gates controlling the supply. On the outer cir- cumference of the overshot wheel is a series of buckets into which the water pours and by its weight causes the wheel to revolve. As the wheel turns each bucket fills as it passes the inlet orifice and empties as it approaches the bottom, so that on one side are always a certain number of buckets filled with water. This class of wheels may be employed in falls of from 6 to 60 feet, and with streams having from a few up to 50 second-feet dis- charge. In order to lose as little of the fall as possible the bot- tom of the wheel should approach close to the lower water sur- face, but should not dip into it, as by drowning the wheel its power is diminished. These wheels are made of such width as to permit of their buckets being large enough to hold a con- siderable weight of water. The buckets of overshot wheels may be made of straight boards or sheets of metal having two or three bends in them, or may be curved. The number of buckets may be calculated by the following formulas given by Bjorling: For wheels from 12 to 20 feet in diameter, n = 2.id: (8) and for wheels 25 to 40 feet in diameter, n = 2.3<*. . . . t . . . . (9) The depth of shrouding for these wheels is about 12 inches, and the bucket opening is about J of a square foot for each cubic foot of bucket contents, or is about 7 inches in width. The 532 PUMPING, TOOLS, AND MAINTENANCE quantity of water in cubic feet per second being Q, the effective horse-power of such a wheel may be gotten by the formula HP = .oSsQh (10) Overshot water-wheels may be employed to operate through gearing or belting any of the usual forms of reciprocating or centrifugal pumps, and will elevate volumes of water to heights proportioned to the power they are capable of developing. 396. Turbine Water-wheels. Turbine wheels may be di- vided into three classes, according as they are acted on (i) through impulse, (2) through pressure, and (3) through reaction. Impulse wheels have plain or concave vanes or float-boards, on which the water strikes more or less perpendicularly. Pressure- wheels have curved float-boards along which the water glides. Reaction wheels consist of an arrangement of pipes from which water issues tangentially. To this latter class really belong Pelton wheels, which are vertical reaction wheels. While pressure and reaction wheels are similar in construc- tion, they differ in that in the former the passages between the vanes are not completely filled with water, while in reaction wheels the water fills and flows through the whole section of the discharge-pipe. In impulse wheels the water spreads over the vanes in all directions, while in pressure and reaction wheels it flows only over one side. Turbines are again distinguished as (i) outward-, (2) inward-, and (3) mixed- or parallel-flow turbines. The former receive the water at the center and deliver it at the periphery of the revolving wheel, the regulating apparatus con- sisting of a ring inserted between the outer periphery of the guide-blades and the internal periphery of the revolving wheel. In inward-flow turbines the motion of the water, as the name implies, is practically the reverse of that for outward flow. Tur- bines possess an advantage over vertical water-wheels in that they may be used with any fall of water from one foot to several hundred feet. The. efficiency of turbines differs with the height of the fall. It is less for small wheels and high falls and greater for large wheels and small falls. Overshot wheels frequently attain a greater efficiency than turbines with falls of 20 to 40 TURBINE WATER-WHEELS 533 feet, while with falls of 10 to 20 feet their power is about the same; but turbines possess a great advantage over other (except Pelton) water-wheels in having the same efficiency under dif- ferent falls and volumes, and in that they can be regulated. Some- times the whole power may be required of the turbines, at other times only a part may be required; sometimes water is scarce, and at other times abundant; but the regulating apparatus is such that the efficiency remains nearly the same. The chief differences between turbines and vertical water-wheels are that the turbines may be drowned, but vertical wheels must be elevated above the water in the tail-race; the turbine takes its supply at the bottom of the fall and the water-wheel at the top or beginning of the fall, and therefore the former obtains nearly the whole pressure due to the head or height of the fall; turbines work without material loss of energy when drowned and move with a greater velocity than vertical water-wheels, and hence may be reduced in size and weight for equal power. The outward-flow turbine is more popular in Europe, and is generally known as the Fourneyron type of turbine. The horse- power of this class of turbine may be roughly determined by the formula - ....... <"> in which q is the quantity of water flowing through the pipes of the turbine per minute. Inward-flow turbines are more popu- lar in the United States. They are the reverse of the Four- neyron type in that the guide- wheel surrounds the revolving wheels and after the water has passed the buckets it is gradu- ally deflected downward by the curved under side of the re- volving wheel. Mixed- and parallel-flow turbines are gener- ally known as the Jonval or Girard type of turbine. They may be fixed at any convenient distance above the tail-race, and must have sufficient water above the guide-blades to allow it to enter freely without eddies. The horse-power of this type of turbine may be roughly determined by the formula <*> 534 PUMPING, TOOLS, AND MAINTENANCE in which Q is the quantity of water available in cubic feet per second. Of the American makes of water-wheels probably the two most extensively employed are the Victor turbine and the Leffel turbine, though a number of other types are manufactured. These wheels have been extensively employed for all the various purposes to which power may be applied, and a number of pump- ing plants for irrigation operated by such turbines have been erected in the West. These turbines come in sizes and powers ranging from a few inches in diameter under a head of but a few feet, and capable of developing as little as one horse-power, up to the enormous sizes which have recently been built for the Niagara Water Power Company, and other similar concerns, which are capable of developing as much as 5000 horse-power, and which may be operated under several hundred feet of head, and have diameters as great as 6 or 8 feet. They range in price likewise from one hundred to several thousand dollars. There has recently been erected at Prosser Falls, Washing- ton, a turbine power and pumping plant capable of irrigating 4000 acres, besides furnishing power for factories and electric- lighting purposes. The water is pumped to an elevation of 100 feet with a power-producing fall of 20 feet, and is deliv- ered to the turbines through a flume 10 feet deep by 12 feet clear width, and carrying 6 feet in depth of water at low stages. The turbines are 48 inches diameter, of special Victor type, and there are two of these, each capable of developing 135 horse-power under 12 feet head. They operate a pair of Duplex pumping- engines of 25-inch cylinder and 24-inch stroke, each having a capacity of 4000 gallons a minute. A third pump is to be installed, and when erected the entire plant will have a daily capacity of about 45 acre-feet. 397. Pelton Water-wheels. Pelton water-wheels are sim- pler in construction than turbine wheels and less liable to be clogged or to get out of order, while the ycna be worked under much greater heights of fall than can turbines. They are ver- tical, tangential reaction wheels, and power is derived from the pressure of the head of water supplied by a pipe which discharges PELTON WATER-WHEELS 535 upon the wheel -buckets on the lower side of the wheel through a small nozzle, as was the old hurdy-gurdy of California mining days operated by the discharge through a hydraulic monitor. Pelton wheels are not recommended for heads less than 30 to 50 feet, as below these heads turbines are usually more efficient, though for the production of small powers, say 10 or 20 horse- power, a Pelton wheel will give as great efficiency as any other wheel with heads of 10 to 30 feet. But above 50 feet head and up to 2000 feet a Pelton wheel is best, as no other wheel produces anything like the same efficiency or works with equal simplicity. These wheels are adapted to a wide range of conditions of water- supply, producing power under the most varying conditions with almost equal efficiency. This is accomplished by simple change of nozzle-tips, by varying the size of stream thrown upon the wheel, the power of which may thus be varied from maximum to 25 % without appreciable loss. The buckets being open, there is no uncertainty or annoyance from derangement of the parts, or stoppage by driftwood or other substances in the water. They are relatively cheap of instalment, and may utilize the water from a small spring or creek as well as from the largest source of supply. These wheels admit, by varying their diameter, of being placed directly on the crank-shaft of power pumps without intermediate gearing or connections. The efficiency of Pelton wheels is perhaps a little higher than that of turbines, the latter attaining efficiencies of 60% to 80%, while Pelton wheels not uncommonly attain efficiencies of 70% to 85%. The buckets which are on the periphery of a Pelton wheel the latter, by the way, is narrow, not having the broad diameter of other vertical wheels are of metal, cup-shaped, and divided into two compartments in such way as to develop the full force of the impinging stream, while in passing out the water sweeps the curved sides with a reactionary influence, giving it the effect of a long impact. The power of this wheel does not depend upon its diameter, but upon the volume and head of water sup- plied. There are practically three types of Pelton wheel- single nozzle, double nozzle, and multiple nozzle though there are in addition a number of patented attachments to the wheel, 536 PUMPING, TOOLS, AND MAINTENANCE giving it various names, as the Hett Pelton wheel, the Caudle Pelton wheel, and others, which have no especial advantage over the more ordinary forms. The single-, double-, and multiple- nozzle wheels, as their names imply, may have one or more nozzles from which water is directed tangentially at various parts of the wheel. As yet few Pelton wheels have been employed in pumping water for irrigation, but it is not improbable that in the near future their value in utilizing small volumes of water from great heights for this purpose will become better appreciated. Several wheels of this character have been erected, both for the produc- tion of very small and very large power. Some are so small as to develop power from the supply of a house faucet, running little pumps for filling water-tanks for domestic use. At the North Star mine in California one of the largest has recently been constructed for pumping, which is operated under an effective head of 750 feet, the wheel being i8J feet in diameter, of 300 H.P. capacity, and mounted on a bicycle-like spoked frame having a lo-inch steel shaft connected directly with air-compressing engines with a speed of 300 feet a minute. The peripheral speed of this wheel is 6000 feet a minute, and its efficiency is believed to be as high as 90%. Another Pelton water-wheel working under 810 feet head, the wheel being but 40 inches in diameter, develops 600 horse-power; and still another wheel 57 inches in diameter under 1410 feet head develops 500 horse- power. 398. Uses of Water-power. Turbine and Pelton water- wheels, and in fact simple vertical water-wheels, may be util- ized in connection with irrigating plants in a reverse manner to that just described; that is, not for pumping water for irri- gation, but the water which flows in gravity canals may be util- ized to develop power for various economic purposes. On the lines of nearly all canals there is wastage of power in falls introduced at the headworks, at the outlets of storage works, and at various points where falls are introduced to neutralize the surface grades. At such points as these turbines or Pelton wheels may be employed to generate power which may be util- WATER-PRESSURE ENGINES 537 ized for manufacturing purposes, for electric lighting or trans- mission of power, or for pumping water from low-service canals to high-service lines which will bring under irrigation areas which would otherwise go without water-supply. The water in the Folsom canal in California is used to de- velop power through four pairs of turbines, each pair having a capacity of 1260 horse-power at 300 revolutions per minute, operated under 55 feet head. They develop 5000 horse-power for electric transmission, the remainder being employed for power at the site. At Roosevelt dam 4400 horse-power are developed at the outlet gates and this may be transmitted electrically sixty miles to Mesa and Phoenix, where it may be utilized in pumping seep- age water from the irrigated lands. Additional pumping plants will be located along the Verde River to utilize the fall between Roosevelt dam and Granite Reefs diversion dam. On the Min- nedoka project, Idaho, 20,000 to 30,000 horse-power will ulti- mately be developed for electric transmission and pumping of seep- age water to be reused in irrigation. In Italy and India irrigation water is thus employed for de- veloping power; at the Fife dam in Bombay, and notably near Cigliano, Italy, where the water flowing in a feeder of the Cavour canal is thus employed to lift water to a high-level canal for further use in irrigation. There are diverted from the stream three canals, between the two lower of which is placed an exten- sive turbine pumping plant which receives its water from the upper of these two canals and tails into the lower canal, whence it is distributed for the irrigation of low-lying fields. The third or uppermost of these canals through a wrought-iron pipe three feet in diameter supplies water under head of 66 feet to the pumps below, and these elevate it through a pipe of the same diameter to a total height of 140 feet, where it is emptied into a fourth canal, which distributes it for irrigating the upper fields. 399. Water-pressure Engines. Water-pressure engines, as their name implies, develop power from the pressure of water confined in upright pipes. They are used to convert stored into active energy, as the water acts by its weight alone, in oc- 538 PUMPING, TOOLS, AND MAINTENANCE casional instances only being assisted by momentum. Their motion is periodical and reciprocating, and they are therefore serviceable when not required to develop rotary motion as in operating direct -acting pumping-engines. In using water-pres- sure engines care must be taken to prevent sudden checking of the descending volume of water, and to this end escape- valves, air-vessels, accumulators, or other means of lessening shock which the engine sustains are provided. The principal parts of such a machine are the reservoir, the supply-pipe which conducts the water from the reservoir to the working cylinder, in which latter work is performed by forc- ing upward a loaded driving piston. The cistern is relieved of water after the work is performed by a discharge-pipe. A regulator is placed in a connecting pipe which joins the work- ing cylinder with the supply-pipe. These engines are made single- and double-acting, and may have one or two cylinders. In the single-acting engine the piston is moved by water pres- sure in one direction only, and in the opposite direction by its own or added weight. In the double-acting engine the piston is moved in both directions by the force of water. There are many designs and many makes of these engines, and it may be said of them that they are better suited for pumping in mines where a great fall is readily obtainable and a comparatively small volume is to be elevated to a considerable height than they are for irrigating purposes. There are a few forms of water-pressure engines which are rotative, and these are similar to steam-engines with fixed cylinders, connecting-rods, and fly-wheels, but have no flap on the slide-valve. There are also a few designs of oscil- lating water-pressure engines, worked on the principle of the old oscillating marine engine; yet none of these can be recom- mended especially for pumping water for irrigation. There is not much difference between rotary water-pressure engines and impulse turbines other than that the former are less eco- nomical than the latter, which are generally larger and more efficient. No exhaustive experiments have been made to ascertain the performance and economy of these engines. Where they HYDRAULIC RAMS 539 arc utilized under the most advantageous circumstances their efficiency is not infrequently as high as 70% or 80%. Water- wheels have an advantage over water-pressure engines in their simplicity and cheapness. Under small pressures water-wheels are preferable. Under great pressures pressure-engines may att?.in higher efficiencies, but they are much more elaborate and expensive machines as compared with most water-wheels, except the Pelton. It may be said that under great pressures, where it is desirable to make the best use of the water-power available, water-pressure engines are most economical, but where water-power is abundant, and it is desired to economize cost, turbines have the advantage. 400. Hydraulic Rams. Where there is a slight fall and it is desired to raise small amounts of water the hydraulic ram is extremely simple, useful, and economical. It works on the principle of a large volume of water having a small fall forcing by impulse blows a smaller volume of water to a higher eleva- tion. Hydraulic rams owe their action to the shocks which are so objectionable in water-pressure engines. There are three classes of such machines: (i) those having no air-vessel in direct communications with the drive-pipe; (2) those having an air-vessel in direct communication with the drive-pipe; and (3) pump- ing-rams. Water is delivered to the ram from a reservoir or a stream with steady flow through a supply- or drive-pipe, at the end of which is a check-valve opening into a chamber connected with the discharge-pipe. In the drive-pipe, near the check- valve, is a weighted pulse or clack-valve which opens inward, the length of stroke of which is capable of regulation. Sup- posing the water at rest in the machine and the deli very- valve closed and the pulse-valve open, the water that passes through the drive-pipe flows with a velocity due to the height of fall out through the pulse-valve, which it almost immediately closes. At the moment the issue of water ceases a ramming stroke is created w r hich opens the deli very- valve and permits the water to enter the air-vessel, and at the same time, in consequence of the shock to the delivery-valve and by virtue of its elasticity, the water flows back through the drive-pipe. At the moment 540 PUMPING, TOOLS, AND MAINTENANCE the backward motion begins the delivery-valve closes and the pulse-valve opens to allow the passage of water from the drive- pipe. The alternation of these effects is continuous. A general rule for the discharge of hydraulic rams is that about one-seventh of the supply volume of water can be elevated to a height five times that of the fall, or one-fourteenth part may be elevated ten times the height of the fall, etc. The fall should range from 2 to 10 feet, but not above this, owing to the wear and tear produced by the ramming stroke. Among the ad- vantages of hydraulic rams are their small first cost and very small cost for maintenance; also, that they are unaffected by tail water, and may continue working even when flooded. They are not economical in water, as it takes a large volume to do a small amount of work. Their efficiency is low, and as the height to which the water is elevated increases the efficiency decreases. The efficiency of a well-designed ram working under the most advantageous circumstances may be as high as 66%. With a great difference between the delivery and supply head only a small percentage of water is pumped. Let H = height to which water is elevated and h = head consumed in friction and hydraulic re- sistance; then for the actual work done P = w(H-h,), ..... (13) in which w = weight of water elevated. The efficiency of a ram may be expressed by the formula in which q = quantity of working water in gallons, Q quan- tity of pumped water in gallons, h = head of working fall, and H = height to which water is pumped. The diameter of the drive-pipe may be gotten by the formula d = .o$S\/~q ..... - - (15) The length of drive-pipe should be increased with the height to which water is to be lifted. A general rule is to make its length equal five to ten times the height of fall. Its inclination should vary from i in 18 for small falls to i in 4 for high falls. The HOT-AIR, GASOLINE, AND ALCOHOL ENGINES 541 diameter of the delivery-pipe is usually from J to J the area of the drive-pipe. A hydraulic ram should be protected from frost and a strainer should be secured at the upper end of the drive-pipe. But few rams are sufficiently powerful to pump water for irrigation. Most of those which can be used for such purposes partake more of the nature of hydraulic-ram engines than of hydraulic rams proper, being so designed that they may be actuated by dirty water as well as clear, and they are more intri- cate in their construction and valve arrangement than the simple ram. One of the best hydraulic rams made for pumping large volumes is the Rife hydraulic engine. The largest of these only are capable of elevating enough water for irrigation purposes. Those having a drive-pipe 8 inches and a delivery-pipe 4 inches in diameter are capable, under a head of 10 feet and utilizing one second-foot of supply per minute, of elevating about J acre-foot per day of 24 hours to a height of 25 feet. Such a machine costs $500, or at the rate of about $10 per acre irrigated for first cost of plant, and practically nothing for operation. 401. Hot-air, Gasoline, and Alcohol Pumping-engines. Hot air pumping-engines depend for their operation on power developed by the expansion of heated air without the interposition of steam or other agency to convert the heat into motion. Alcohol and gasoline-engines are likewise operated without converting the heat produced by combustion into steam, but depend upon the expansive force produced by the explosion of alcohol or gaso- line converted into gas when brought into contact with air. They have under certain conditions decided advantages over water- and steam-motors in that they can be employed where there is not a sufficient water-supply to operate a water-motor, utilizing, as they do, practically no water, and therefore being able to pump all that is available for irrigation. They may be employed where steam-pumps cannot be, both because of their economy in water consumption and because of the kinds of fuel which they may use; gasoline and alcohol being serviceable in arid regions where transportation of fuel is expensive and hot-air engines being capable of utilizing any variety of fuel. Again, they are compact, and simple of erection by comparatively unskilled machinists, 542 PUMPING, TOOLS, AND MAINTENANCE and can be operated at the least expense for supervision. De- natured alcohol is as efficient a fuel, pint for pint, as is gasoline, when utilized in a specially designed alcohol engine of which there are several successful makes on the market. Such alcohol can be made on the farm from waste or refuse vegetables, fruit, or grain. Hot-air engines are constructed almost wholly as pumping- engines, and the motive power and pumping apparatus are combined in one machine inseparably connected. Gasoline- and alcohol-engines come, as do other motive powers, independent of the pump, and therefore capable of utilization for doing other forms of work; but they are also made as direct connected pump- ing-engines, both pump and motive power being combined in one mechanism. The only form of hot-air pumping-engine on the market is the De Lamater hot-air engine. Many thousands of these machines are in use, chiefly for pumping small quantities of water in cities for manufacturing. or domestic uses, only a few being employed in pumping water for irrigating. They are so simple of construction that any one capable of lighting a match can operate them. There is no possibility of explosion, as may occur through carelessness with a gasoline-engine. When once started they require no further attention than the replenishment of fuel. These engines are made with capacities ranging from a few gallons a minute up to one second-foot, equivalent to . 2 of an acre-foot per day of 24 hours, limited by the height of lift, which varies from a few feet to 500 feet. One of the objections to hot- air pumping-engines is their great first cost, which for the largest sizes for example, those capable of pumping .2 second-foot is $600, or, for plant alone, $3000 per second-foot, equivalent to from $50 to $75 per acre irrigated. Gasoline- and alcohol-engines are used extensively in some portions of the West, notably in Kansas, for pumping water for irrigation. They are made of various dimensions up to those capable of developing 50 H.P., and pumping a correspondingly large volume of water, and they are constructed as combined motive and pumping plants or as separate motors to be attached to various forms of pumps. The chief advantages which these PUMPING BY STEAM-POWER 543 machines have over other motive powers for pumping are their compactness and simplicity of installation and operation, but above all their cheapness, not so much for first cost as for ultimate maintenance, though in this latter item they do not surpass hot- air pumping engines. The largest of these engines is capable of elevating for low heads as much as 10 second-feet of water, or 20 acre-feet per day of 24 hours, and lesser quantities to greater heights in proportion. The cost of operation of such a machine as this has been for gasoline as low as 2 to 5 cents per acre-foot and for all expenses 5 to 24 cents, depending on lift. The largest sizes will elevate sufficient water to a height of 50 feet to irrigate about 320 acres if storage be provided. 402. Pumping by Steam-power. There are many forms of motors designed to utilize steam-power in pumping. These may be divided into the following three classes: 1. Those in which water is elevated directly by steam, as injectors and pulsometers. 2. Those which utilize the power developed by steam through an engine indirectly by gearing and belting or other separable connection. 3. Those which utilize steam-power through an engine di- rectly, as direct-acting or fly-wheel pumping-engines. In considering steam as a motive power it is unnecessary to refer to any of the forms of steam-engines and boilers employed in developing this power, as their name is legion, and they are manufactured in all varieties, forms, sizes, and prices. Under the title of Pumps direct-acting engines will have to be considered, because the motive power is a portion of the pumping mechanism. Such is also the case with pulsometers, vacuum-pumps, and in- jectors. The only feature of steam as a motive power which it is de- sirable to consider is the cost and economy of producing power for pumping purposes and the amount of work which a given power will perform. This consideration of power in elevating water is one which bears the same relation to its other forms as does the power produced by water or by air, and therefore the facts here developed have immediate bearing on the powers 544 PUMPING, TOOLS, AND MAINTENANCE produced by water-motors as well as steam-motors. According to Mr. J. T. Fanning, the power P in foot-pounds required to produce a given flow of water by pumping is P = QWh, ...... (16) in which Q = volume in cubic feet of water to be set in motion, W = the weight of a cubic foot of water in pounds, equal to 62.5 Ibs., and h = is the height in feet to which the rate of motion 2g is due. The power required to accelerate the motion of water is in addition to the dynamic power, p, in foot-pounds required to lift it through a height, H, of actual elevation, and the equation of lifting per second, disregarding frictional resistance, is P-QWH, ...... (17) or for any time p = tQWH. ...... (18) The frictional resistance, F, to flow in a straight pipe is pro- portional about to the square of the velocity of flow, and is com- puted by some formula for friction head, h v among which, for lengths exceeding 1000 feet, is 4/JfV in which / is the length of pipe in feet, while the coefficient F may be derived from the tables of resistance to flow in pipes given in Chapter XIV. The equation of power p v required to overcome the fric- tional resistance to flow in pipes, in which h l is the vertical height of lift in feet equivalent to frictional resistance, is (20) As one horse-power = 33,000 foot-pounds per minute, P9 .... (21) 33,000 in which P is the power in foot-pounds required to produce a PRODUCER GAS POWER 545 given flow and 5 is the number of strokes of the pump per minute. The horse-power required to overcome the combined dy- namic lift and frictional resistance to flow for a given time, /, is (22) 33,000 403. Producer Gas Power. Gas generated in a producer and utilized in an internal combustion engine furnishes the most efficient and economic power under certain conditions. Coal converted into power under a steam boiler will develop 5 to 8 per cent of the latent energy of the fuel while in a producer gas plant it will develop 2\ times as much power or 12 to 20 per cent of the latent energy. In many parts of the arid West, where good steaming-coal is scarce and expensive, there are unlimited supplies of cheap lignite, worth one to two dollars per ton near the mine. This is not a good steaming-fuel but in the gas producer it develops as high efficiency, often one pound of lignite per B.H.P., as does the best eastern coal under a steam boiler. Gas producers are of two types, (a) suction and (b) pressure. The former are at present made only in small powers, for 25 to 100 H.P., and are not as yet well adapted to the use of fuels so high in volatile matter as lignite. Pressure producers are made in sizes from 100 to 500 H.P., and may be used in batteries de- veloping several thousand horse-power. They may be success- fully operated on lignite, peat, or wood, as well as on all varieties of coal. The gas generated is exploded in a gas engine which may be of any of the regular makes, directly or indirectly connected with a pump. Or the producer gas plant may be located at a distance from the pump, as at a mine, and the power generated be con- verted into electricity and transported to the pumping station, as is done with the steam power plant of the Reclamation Service at the Williston-Trenton-Buford project (Art. 408). 404. Energy, Work, and Power. In considering energy expended in lifting water and useful work accomplished, the following equivalents are helpful. 35 546 PUMPING, TOOLS, AND MAINTENANCE TABLE XXX. EQUIVALENT UNITS OF ENERGY. i cu. ft. water at 39 . 2 Fahr. = 7 .48055 U.S. gals.= .028316 cu. meter=62.396i Ibs. 0.13368 =i ' =.003785 " " = 8.34112 " 35.31563 " ' =264.179 " " = i " " = 2203.55 " 0.016027 " =0.119888" " =.000454 " " = i lb. Any form of energy, as wind or water pressure, steam or electric power, may be utilized in lifting water through the medium of various pumping devices. The following are some of the more useful equivalent units of work. TABLE XXXI. EQUIVALENT UNITS OF WORK. i i horse-power-hour = 1,980,000 foot-pounds. i kilowatt-hour=2,654,i5o foot-pounds. i pound of steam =7 78,000 foot-pounds. i pound of hard coal = 11,400,000 foot-pounds. i pound of soft coal =9,9 1 0,000 foot-pounds. 100 cu. ft. i ft. high (water) = 62, 396 foot-pounds. In considering the equivalents of various heads of water, it is well to know that i foot of head = 0.4335 pound per square inch = 62.396 pounds per square foot = 0.02945 atmosphere. Also thpt i pound pressure per square inch = 0.01602 foot-head. Among the more useful units of power are the following with their equivalents. 405. Centrifugal and Rotary Pumps. For lifting large volumes of water to moderate heights the centrifugal pump excels in economy, efficiency, and simplicity of construction, and in cost both for plant and its maintenance. Where circum- stances are suited to its employment, it is perhaps the best pump for irrigation. Being valveless, it is well adapted to raising water containing sediment or foreign matter. It is continuous in its action, and is easily erected and operated by machinists of moderate skill. A centrifugal pump is essentially an outward-flow turbine driven in the reverse direction. Water enters the pump with- out any velocity of whirl, and leaves it with a whirling velocity CENTRIFUGAL AND ROTARY PUMPS 547 TABLE XXXII. EQUIVALENT UNITS OF POWER. i horse-power =33,000 foot-pounds per minute = 42,4i6 thermal units per minute = 0.0226 watt= .0069 pound cu. ft. per minute. .00134 horse-power= 44.24 foot-pounds per minute=.o568 thermal unit=i watt = .307 pound cu. ft. per minute. .02357 horse-power =7 78 foot-pounds per minute = i thermal unit=i7-58 watts = 5.388 pounds cu. ft. per minute. .00436 horse-power= 144.92 foot-pounds per minute=.i857 thermal unit=.o326 watt= i pound cu. ft. per minute. One Watt. One Kilowatt. One Horse-power One Watt-Hour. One Horse-power-Hour One Ampere-Hour. . . . Torque A RATE of doing work. i . ampere per second at i 7373 foot-pound per second. 44.238 foot-pounds per minute. 2654.28 foot-pounds per hour. .5027 mile-pound per hour. .00134 horse-power. Tf^g horse-power. volt. A RATE of doing work. 737.3 foot-pounds per second. 44238. foot-pounds per minute. 502.7 mile-pounds per hour. 1.34 horse-power. f A RATE of doing work. 550. foot-pounds per second. 33000. foot-pounds per minute. 375. mile-pounds per hour. 764. watts. .746 kilowatt. A QUANTITY of work. 2654.28 foot-pounds. . 503 mile-pound, i. ampere hourXi volt .00134 horse-power-hour. rtx horse-power-hour. A QUANTITY of work. 1,980,000. foot-pounds. 375. mile-pounds. 746. watt-hours. .746 kilowatt-hour. A QUANTITY of current. One ampere flowing for i hour, irrespective of the voltage. Watt-hour -i- volts. FORCE moving in a circle. A force of i pound at a radius of i foot. 548 PUMPING, TOOLS, AND MAINTENANCE which must be reduced to a minimum in the action of lifting. The direction of the water as it flows toward the discharge-pipe is controlled by a single guide-blade, which is the volute or outer surface of the pump-chamber into which water flows on leaving the fan. A centrifugal pump cannot be put into action until it has been filled with water, which operation is effected through an opening in the casing when the pump is below water or when above water by creating a vacuum in the pump-chamber by means of an air or steam jet which raises the water into the suction-tube. In action the water rotates in the pump as a solid mass, and delivery only commences when the speed is such that the head due to centrifugal force exceeds the lift, though this speed may afterwards be reduced. As the pump commences to operate the water rises in the suction-tube and divides so as to enter the center of the pump-disk on both sides. The revolving pump- disk or fan, as in a turbine, is provided with vanes or blades curved so as to receive the water at the inlet surface without shock an effect obtained by so proportioning the pump as to give a gradually increasing velocity to the water until it reaches the outer ends of the vanes and then a gradually decreasing velocity until it reaches the discharge-pipe, a result obtained in construction by conical ends to both suction- and delivery- pipes and a spiral casing. The water leaves the surfaces of the vanes with more or less velocity and impinges upon the mass of water flowing around inside the outer casing towards the dis- charge-pipe, and this casing must have a section gradually in- creasing to the point of discharge in order that delivery across any section of it may be uniform. This section is also designed so as to compel rotation in one direction only with a velocity corresponding to the velocity of the whirl on leaving the pump- disk. Nearly all centrifugal pumps are provided with a vortex- or whirlpool-chamber in which the water discharged from the re- volving vanes continues to rotate, and here the kinetic energy is converted into pressure energy which would otherwise be wasted in eddies in the confining chamber. This vortex-chamber is provided with guide-blades following the direction of the CENTRIFUGAL AND ROTARY PUMPS 549 stream lines so as to prevent irregular motion. The working parts of a centrifugal pump accordingly consist of a series of curved disks or vanes mounted on a spindle and revolving in a chamber in a manner similar to a fan-blower. A revolution of each vane within this closed case produces a partial vacuum which draws up the water, and it is on a proper proportioning and arrangement of these vanes that the effective working of the pump chiefly depends. These pumps are so constructed that the casing may be removed to allow of the inspection and cleaning of the pump-disks. The curved vanes are made of the best steel or phosphor-bronze and the pump-disks should be perfectly balanced in order to produce even motion in the water. The efficiency of a simple centrifugal pump diminishes with the lift, and for lifts exceeding 25 to 30 feet a plunger-pump pro- duces better results. Centrifugal pumps are driven by belting or shafting or they may be directly connected to the motor-shaft. The more rapidly the pump-disk rotates, the lift remaining constant, the smaller is the centrifugal force a peculiar con- dition, due to the fact that as the discharge increases the velocity of the water in the casing more nearly approaches that of the water leaving the pump-disk, and therefore the efficiency of the pump improves, and with it the theoretical lift diminishes as well as the centrifugal force. Another peculiar property of centrifugal pumps is that a small increase in the number of revo- lutions after it has begun discharging produces a very large in- crease in the delivery. The highest efficiency ordinarily obtained by simple centrifugal pumps is from 65 to 70 per cent, and ex- periments seem to indicate that the efficiency of a centrifugal pump increases as its size increases. Thp'.s, a pump with 2-inch discharge-pipe will give an efficiency of 38 per cent, while a 3-inch pipe will give a 45 per cent efficiency and a 6-inch pump a 65 per cent efficiency. From this it appears that a centrifugal pump is to be recommended rather where large volumes of water are to be lifted. Rotary pumps are theoretically among the most efficient, and their form is a favorite among experimenters in pump designs. They are, however, capable of elevating but small quantities of 550 PUMPING, TOOLS, AND MAINTENANCE water, and are of little value for elevating water for irrigation. They may be termed revolving piston-pumps in distinction from direct-acting pumps, and have the advantage of not changing the direction of flow of the water during its elevation by each stroke of the pump. They can be run at a high speed, and have no complicated leather valves or pistons to be choked or get out of order. These pumps may be divided into two classes, according to the forms and methods of working the revolving pistons and the manner in which the butment is obtained. The efficiency of rotary pumps is low, there being a great excess in driving power required over useful work performed, caused chiefly by the inertia of water or difficulty of putting it in motion after it has been brought to rest and the necessity of imparting at certain moments a high velocity to a large volume of water, which calls for the expenditure of considerable power. 406. Examples of Centrifugal Pumping Plants. Centrifugal pumps are made both to be worked separately by transmitted power or by motors directly connected to the pump frame, and are of varying capacities, from those having 2-inch discharge- pipes up to those having 45-inch discharge-pipes, the largest sizes being capable of elevating as much as 100 second-feet, or the same number of acre-feet, in a day of 1 2 hours. Centrifugal pumps may be either single or compound, the latter being also called turbine pumps. Single stage pumps are generally used for low lifts while multiple stage pumps, made in 4 to 8 stages, will lift water from 100 to 1000 feet. These pumps come in very large sizes, capable even of lifting 5,000,000 to 10,000,000 second-feet in 24 hours. When made direct-connected to steam turbines or producer gas-engines, they are of high efficiency. Such pumps cost for plant from $10 to $30 per acre-foot lifted to moderate heights and from $5 to $10 per acre-foot per annum for operation. A centrifugal pumping plant for irrigation for the Vermilion Canal Company in Louisiana consists of six 1 5-inch pumps, capable of discharging 130 second-feet of water against a head of 20 feet, and are operated by two engines, each of 250 H.P. A centrifugal pump in southern Arizona, operated by a lo-H.P. PUMPING-ENGINES 551 engine and boiler, has a capacity of two-thirds of a second-foot a day. The operation of this plant calls for the consumption of about one cord of wood per 24 hours, and it is capable of irrigating about three acres in a season. A similar pump in the same locality and operated by a gasoline engine of 35 H.P. will handle about nj acre-feet in 24 hours, on a consumption of about 84 gallons of gasoline. Other centrifugal pumps of small capacities and capable of watering 5 to 10 acres per day, and in the course of an irrigation season from 50 to 100 acres, are operated by one man at a cost of about $2.50 per acre irrigated for maintenance and $15 per acre for first cost of plant. A centrifugal pump at Yuma, Ariz., lifts 3 acre-feet of water per hour a height of 10 feet at a cost of $0.54 per acre-foot. 407. Pumping-engines. These may be either direct-acting, or pump and motor may be indirectly connected by belting or shafting. In general it may be stated that fly-wheel pumping- engines which give high duty under the conditions of municipal water service, and other forms of indirect pumping-engines, are not the most efficient and economical for purposes of irrigation. Direct-acting pumping-engines have a reciprocating motion, and may be either single- or double-acting. They may be either steam pumping-engines or the water end of a direct-acting pump may be operated through gearing from water-, electric-, gas-, gasoline-, or alcohol-motors. Direct-acting steam-pumps have the water and steam ends centered in line one with the other so that the water-plunger and motor-piston are attached to the same piston-rod and work together without an intervening crank or other connection. This is the simplest and most compact form of pumping-engine, and is more extensively used for pumping than all other varieties of pumping machinery combined, though it is perhaps one of the most wasteful and expensive forms of steam-engines. In selecting steam pumping-engines, among the points most desirable are strength and simplicity of working parts; large water-valve area; long stroke and ample wearing surfaces; continuity of steam flow; simplicity of adjustment and repair; moderate steam consumption. In choosing from the various 552 PUMPING, TOOLS, AND MAINTENANCE makes of pumping-engines It is well in corresponding with the makers to inform them among other points of the purposes for which they are to be used; height of lift and height to which water is to be forced; quantity of water to be elevated; motive power; and quality of water as clear or muddy. Direct-acting steam pumping-engines may be either high- pressure or compound. In the latter case they are economical in both fuel and water consumption, and their cost for opera- tion is therefore correspondingly less, though their first cost is a little greater. The best form of direct-acting pumping-engines are Duplex pumping-engines, consisting of two direct-acting steam pumping-engines of equal dimensions, side by side on the same bed-plate, with a valve motion so designed that the movement of the steam-piston of one pump shall control the movement of the slide-valve of its opposite pump so as to allow one piston to proceed to the end of the stroke and come to rest while the other piston moves forward on its stroke. Direct-acting pumping-engines are made to operate also with gas, gasoline, alcohol, electricity, or water as the motive power, and in great variety of design and capacity. All single-acting pumps should be provided with air-cham- bers, while these are a decided addition even to double-acting pumps, for though the latter have a fairly steady discharge, the air-chamber insures almost perfect uniformity of delivery. The capacity of an air-chamber for a pair of double-acting pumps is about five or six times the combined capacities of the water- cylinders, while for a single-acting pump it may be ten or twenty times greater. The air-chamber performs practically the office of a stand-pipe attached directly to the pump. It neutralizes the variations of velocity of discharge in the delivery-pipes, the fluctuations of which might cause danger of ramming and wastage of work. The air-chamber obviates this by permitting the excessive delivery of water from a pump-stroke to enter it and thus compress the air, while on the return stroke the ex- pansion of the air forces out water to supply the deficiency. 408. Examples of Steam Pumping Plants. Several exten- sive steam pumping plants have been introduced in the-* West EXAMPLES OF STEAM PUMPING PLANTS 553 for providing water for irrigation. Their first cost is usually less than for gas or hydro-electric plants, though not always so, depending upon the power generated. Their efficiency, in large units, is usually quite high as compared with all other forms of pumping plants, and their maintenance cost is usually a little less, excepting hydro-electric plants. In Arizona is a high-pressure steam pumping-engine capable of irrigating 100 acres per season which cost when erected $ioco, or $10 per acre irrigated, while the cost of runndng it is but $5 per acre. A larger and more modern plant operated near Tucson consists of two compound steam pumping-engines, capable of irrigating 600 acres per season at a cost for operation of $3 per day, the first cost for this plant laid down having been $4200, or $7 per acre, and the height of lift being 70 feet. Still another consists of an automatic cut-off condensingrengine with two 150- horse-power boilers. The pumping-engine which has 1 8-inch stroke and 42-inch cylinders, and is of 165 H.P. capacity, has a fly-wheel weighing 7 tons and making 67 revolutions per minute, the capacity of the pump being 12 second-feet, or about 24 acre- feet in a day of 24 hours. This pump delivers water through a 26-inch redwood stave main, elevating the water 80 feet, and this is stored in a reservoir having 23 acre-feet capacity. A year's test of this engine shows it to be capable of discharging 12 second- feet at a cost of $3 per second-foot for fuel. A pumping plant designed by the writer and employed for the irrigation of 1000 acres consists of a duplicate set of duplex compound pumping-engines each capable of elevating 25 sec- ond-feet with a suction height of 15 feet and forced to an ele- vation of 40 feet. Such a plant in Arizona cost $10 per acre controlled, and for operation not exceeding $0.75 per acre. In the Gila valley, Arizona, one steam-pump, with wood for fuel, raises water 44 feet at a cost of $2.27 per acre-foot and another raises it 50 feet for $2.50 per acre-foot. Others give costs for small engines up to 50 horse-power, ranging between $2 and $4 per acre-foot for similar lifts. The cost per hour for operation is $1.26 and per horse-power per year $137.97. The Reclamation Service has erected at Williston, N. D. 554 PUMPING, TOOLS, AND MAINTENANCE near a lignite mine, a steam-power electric generating plant whence the electricity developed is transmitted long distances for pumping water from the Missouri River for irrigation on the Williston and the Buford-Trenton projects. There are 8 electrically operated pumping stations requiring about 1500 kilowatts from the Williston power-station. HALF LONGITUDINAL ELEVATION SHOWING SIDE TRUSSES HALF LONGITUDINAL SECTION SHOWING DOUBLE CENTER TRUSS FIG. 193. Floating Pumping Station, Buford-Trenton Project, N. D. The pumping installations and canals are designed for de- livering i cubic foot for 80 acres or 2 acre-feet per acre in an eighty days irrigation season. The main Buford-Trenton intake pumping-station consists of four electrically operated centrifugal pumps on a scow which rises and falls with the fluctuations of the river (Fig. 193). The pumps have a combined capacity of 150 second-feet with a lift of 28 feet and discharge into a settling COST OF VARIOUS POWERS AND OF PUMPING 555 basin. A second set of similar pumps, in a concrete building 600 feet from the river, pump the water from the settling basin through one-half mile of reinforced concrete pipe to a canal which commands 6,000 acres. The total lift here is 85 feet and the pumping capacity 75 second-feet. There is a similar main intake station at Williston and other stations lifting to high line canals. The transmission is at 22,000 volts over about 25 miles for each project. 409. Cost of Various Powers and of Pumping. The capital and annual cost of steam, producer gas, and hydro-electric power per brake horse-power is given in the following table: Capital Cost of Plant per B. H. P. Annual Cost of 24 Hour-Power per B.H.P. Rated Horse Power Steam. Producer Gas. Hydro- electric. Steam. Producer Gas. Hydro- electric. 10 $100 Si 75 $150 $90 5 75 I0 5 IOO 55 100 70 TOO $125 80 45 $40 500 60 80 IOO 5 40 30 IOOO 55 70 80 40 35 25 An increase of 50 cents per ton in the price of coal means an additional cost per B.H.P. for 24 hour-power ranging from $3 for large installations to $15 for small ones. The cost of producing electric energy for an installation of about 1000 horse-power, from different sources of power, per kilowatt year, and including interest and depreciation on capital cost, annual running expenses, etc., varies as follows: For steam, $55; producer gas, $60; oil, $86; and hydro- electricity, $37. The results of an extensive series of tests of pumping-plants made in California by the United States Department of Agri- culture furnish some exact data on the cost of pumping water for irrigation by steam, gasoline, and electric power. The cost of lifting one acre-foot of water one foot high ranged for gasoline from 4 to 25 cents; for steam from 2 to 13 cents; and for electricity from 8 to 21 cents; this with gasoline at 6 cents per gallon and with crude oil fuel for generating steam at less than $i per barrel 556 PUMPING, TOOLS, AND MAINTENANCE The cost of electricity was 2 cents per kw. hour. The gasoline plants ranged from 14 to 63 horse-power; steam plants from 30 to 239 horse-power, and the electrically driven from 5 to 39 horse- power. The lifts varied from 22 to 247 feet, and within these limits it cost the irrigators to pump one acre-foot of water from $i to $46 with gasoline, from $0.54 to $9.60 with steam, and from $1.96 to $19.20 with electricity. 410. Pulsometers and Mechanical Elevators. Pulsometers are mechanisms for lifting water by the direct action of steam. They are most advantageously employed for rough work and in difficult situations, chiefly because of their portability, as they can be readily moved from one point to another. The pulsom- eter is capable of utilizing very dirty water, but its capacity is so limited as to render it practically of small value in pumping water for irrigation. It consists of a couple of pear-shaped vessels in one casting, the necks of which terminate in a single chamber. It is designed somewhat on the plan of the human heart, wherein two valve-seats are arranged with one ball-valve which oscillates between them. It also has an air-chamber, suction- and delivery-valves. When charged with water, steam is admitted and presses on the water surface in one chamber, forcing it through the delivery-valve into the delivery-pipe. When the steam reaches the opening leading to the discharge- pipe it comes in contact with the water already in the pipe, and is immediately condensed, forming a vacuum in the chambei just emptied. This vacuum draws the ball-valve over to the seat opposite that which it previously occupied, and prevents for the time further admission of steam, and to fill the vacuum thus formed water rises through the suction-pipe and fills the empty chamber, an operation which is repeated indefinitely. Pulsom- eters contain practically no movable parts; wear is reduced to a minimum, very little attention is required in their use, and there is little chance of clogging the valves by dirty material, but their efficiency is extremely low. A modern mechanical water-elevator, somewhat like the old chain-and-bucket pump, consists of an elongated box which can be set up over the well or other water-supply. At either end of IRRIGATION TOOLS 557 this box is a wheel carrying on its periphery a metal link belt or chain, having attached to it at short intervals wooden projections of such dimensions as completely to fill the cross-section of the box. These projections, or flights as they are called, close the space in the box between each flight, and as the chain revolves they are raised, carrying with them the water resting upon them and preventing it from running back. This machine may be operated by animal, wind, steam, or water power, as desired. The largest size made is capable of lifting about 5 second-feet or 5 acre-feet in a working day of 12 hours, with an expendi- ture of 7 horse-power for a lo-foot lift. The highest satisfactory lift of these machines is about 20 feet, and the cost of a machine of this capacity is about $50 per second-foot, or $i per acre con- trolled, a comparatively trivial outlay for first cost of pumping plant, excepting the motive power. 411. Irrigation Tools. There is little to say of the tools required in the construction and management of irrigation works. Agricultural-tool makers now manufacture hoes, spades, shovel?, and ploughs of special designs for the making and management of ditches and furrows. Special ditching-ploughs of unusual depth and reach are made as right and left ploughs, or some- times to throw dirt in both directions, having a V-shaped shear, thus making a V-ditch at one operation. Ploughs of this kind are also arranged in gangs on sulkies. Corrugated ribbed rollers are employed where the surface of the country is even and level, and for such crops as grain and alfalfa. These consist essentially of a roller of the ordinary form, on the outer surface of which are iron rings or projections of from 2 to 3 inches in height and of about the same width, placed from 4 to 8 inches apart. These projections are some- times V-shaped. In running this roller over the surface of a- well-harrowed field it leaves small furrows, down which the water runs, thus irrigating the crop much as if it were flooded. 412. Scrapers. The most useful implement for the ditch- and canal-maker is the scraper, of which there are many forms and with most of which engineers are familiar. Two forms of scrapers which have peculiar advantages in ditch-making 558 PUMPING, TOOLS, AND MAINTENANCE over the ordinary road-scraper are the Fresno and Buck scrapers. The latter is especially useful in sandy soil with a low lift and short haul, and cheaper work has been done with it than with any other implement. A common form of Buck scraper con- sists of a working or frond board with an effective length of about 9 feet and a height of 22 inches. This board rests hori- zontally on edge on the ground and consists of two planks each 2 inches in thickness, below which is fastened an iron cutting edge which reaches 7 inches below (Fig. 194). At either end of 0123 FIG. 194. Buck Scraper. 4 Feet the scraper is a cam-shaped roller 4 inches in height, on which the scraper is turned over. This board is fastened at the back to a tailboard 3 feet 9 inches in length, on which the driver stands, and is drawn forward by from two to four horses, the scraper being dumped by the driver merely stepping off the tailboard, the forward pull upsetting it. This implement handles, a load of from i to ij cubic yards, while its average daily capacity is about 130 cubic yards. For two horses a scraper of this form is rarely made over 6 feet in length, and the angle of the face- board to the ground is about 28 degrees, and is regulated by the attachment to the tailboard. The Fresno scraper is most satisfactory in handling tough earth too heavy to be handled by a Buck scraper, and which would even give trouble to a road- scraper. This implement is usually drawn by four horses and GRADING- AND EXCAVATING-MACHINES 559 handles about 100 cubic yards a day, each load averaging a third of a cubic yard. 413. Grading- and Excavating-machines. Several of the road-grading machines give great satisfaction in levelling and grading land which is to be irrigated. The more useful expedite the work of preparing land for furrow or flooding, and thus greatly aid the operations of applying water. One of the most popular ditching-machines now employed in the West as a ditcher and excavator consists of a series of gang-ploughs suspended on wheels. An endless belt or elevator is attached to the truck above these ploughs in such manner that it catches the dirt turned up by them and deposits it on the banks of the canal (Fig. 195). FIG. 195. New Era Excavator. This machine requires from eight to twelve horses and three men to operate it, its maximum lift being about 10 feet, while each plough makes a furrow 12 inches wide and 6 inches deep. These machines have attained an average capacity of 100 cubic yards per linear mile and handle about 1000 cubic yards in a day's run. They are of use not only in excavating and building canals, but also in building low earth embankments for storage-reservoirs. An elaborate great canal excavator used in California consists 560 PUMPING, TOOLS, AND MAINTENANCE of a bridge-truss supported on wheels running on rails on either bank of the canal. This deck truss has on it a track on which the engine-house and machinery travel back and forth across the canal, and the excavator consists of a dredging arm carrying an endless chain of buckets. The material brought up by these is deposited on one of two endless belt-carriers running on booms which dump it on either spillbank. The engineer can cause the excavator to move across the canal on the truss bridge, or can raise or lower the excavating arm carrying the buckets, causing these to move forward and perform their work. There are twenty-six of these buckets, each having a capacity of cubic yard, and the apparatus will excavate 3000 cubic yards a day in hardpan. In earth this machine has excavated from 4000 to 5000 cubic yards a day, at an average cost of 7 cents per cubic yard. Dredges of various forms are employed on the larger canals to remove silt which may be deposited in them, and to repair and straighten banks which have been cut down or eroded by the action of the water. Such dredges are usually employed on scows or flatboats, and are operated by small steam-engines, being similar in design and in construction to the ordinary dredge employed in river and harbor work and in like operations. A small dredge which has recently been employed on irrigation canals has a draught of only 15 inches a single bucket, and can excavate from 2 feet above the water-line down to 8 feet below it, delivering either to a shore conveyor or to scows. A larger dredge of similar construction has a 3 -foot draught and exca- vates as much as 70 cubic yards per hour, delivering it at a dis- tance of 100 feet. 414. Maintenance and Supervision. Careful attention should be paid to the proper maintenance and the making of all needful repairs on the lines of canals, on reservoirs, and other irrigation works. The expenditure of an exceedingly small amount of time or money in repairing an injury to canal banks or other works may prevent great destruction of life and property consequent on an injury to the reservoir or canal system. In order that these repairs may be intelligently made, and that damage to the canal SOURCES OF IMPAIRMENT OF IRRIGATION WORKS 561 property may be discovered in time, a suitable system of super- vision must be inaugurated upon the completion of construction. Such a system should include an engineer, a superintendent, and patrolmen. Careful and frequent inspection must be made of earthen reservoir embankments or masonry dams to detect any sign of increased leakage. Cracks in the latter may be filled with Port- land-cement grout under pressure, and leaks by plastering with rich cement mortar. If seepage water through an earth em- bankment is muddy it indicates serious leakage. This may be repaired by drawing off the water and puddling at the upper point of leakage, or even by excavating a pit in the embankment from above and puddling and well bonding with new material. When reservoirs become silten this must be removed by ex- cavating, washing, or sluicing. Waste weirs must be kept clear to their full capacities, as must undersluices, and the gates of the latter must be kept in good working order. 415. Sources of Impairment of Irrigation Works. These are: 1. Erosion of the inner slope of the banks by the canal water. 2. Filling of the canal channel or reservoir from deposition of sediment. 3. Erosion of the outer banks due to storm and flood waters. 4. Damage from cattle, horses, and trespassers destroying the banks, channel, and dams by walking over them. 5. Injury or destruction to the head works, regulators, es- capes, or wasteways by floods. 6. Incendiarism. 7. Decay in timbers forming structures. 8. Destruction of earth-banks due to burrowing by gophers. 9. Injury from growth of weeds or water plants choking the channel, and thus diminishing its discharge. The first and second causes of impairment may be dimin- ished by the use of intelligent engineering skill in the alignment and construction of the canals, and by the vigilance of patrols in discovering indications of erosion and rectifying them. If the amount of sediment deposited is large, it will have to be 36 562 PUMPING, TOOLS, AND MAINTENANCE removed by dredges or scrapers, and such changes will have to be made in the headworks or slope of the canal or by the in- sertion of flushing escapes as to rectify them. Little injury should be caused the outer banks of the canal by storm waters if the canal is properly aligned and ample provisions made for the passage of drainage channels. Injury due to rain falling on the banks may be reduced to a minimum by the encourage- ment of the growth of grass and trees. Damage to the canal from the fifth and seventh causes may be provided against in the construction by building the structure of some permanent material as masonry or iron, and during operation by proper supervision and repairs of the weakened part. Much damage may result from the burrowing of gophers and moles. This can only be prevented by careful supervision, the discovery of the holes, and the destruction of the pests. The discharge of a canal may be considerably reduced by the growth of aquatic plants and willows along the banks. This is to be prevented only by pulling up or mowing the brush or by de- stroying it by fire when the canal is emply. 416. Inspection. In order that the supervision and inspec- tion of works may be properly performed, the canal line should be divided into a number of sections, each of which should be patrolled by a ditch-rider, while the whole should be in charge of a superintendent. Where the line is long, telephone com- munication should be had from each section to the main office of the engineer and superintendent. In addition to this, supplies of lumber, cement, gravel, or other building material should be placed at each bridge, escape, or other work on the canal, and by this means any damage inflicted may be immediately repaired by the patrol, or he may telephone to headquarters for further assistance and proper advice. The length of a division of the patrol should be regulated by the number of irrigation outlets and the character of the works, and they should be of such length that every portion can be visited daily. 417. Works of Reference. Pumping Machinery. BALE, M. Powis. Pumps and Pumping. Crosby, Lockwood & Son, London, 1880. WORKS OF REFERENCE. PUMPING MACHINERY 563 BARR, W. M. Pumping Machinery. J. B. Lippincott & Co., Philadelphia, 1893. BJORLING, PHILIP R. Water on Hydraulic Motors. E. & F. N. Spon, London, 1894. BOVEY, H. T. A Treatise on Hydraulics. John Wiley & Sons, New York, 1895. BRESSE, M., trans, by F. A. MAHAN. Water-wheels or Hydraulic Motors. John Wiley & Sons, New York, 1876. FANNING, J. T. Water-supply Engineering. D. Van Nostrand & Co., New York, 1889. GRIFFITHS, J. A. Windmills for Raising Water. Proc. Inst. C. E., vol. cxix, No. 2672, London, 1895. HUGHES, SAMUEL. A Treatise on Water-works. Crosby, Lockwood &: Son, London, 1882. MAHAN, F. A. Water-wheels. E. & F. N. Spon, New York. MURPHY, E. C. The Windmill; its Efficiency and Economic Use. 2 Parts. Water Supply Papers Nos. 41 and 42. U. S. Geological Survey, Washington, D. C., 1901. RONNA, A. Les Irrigations. Firmin-Didot et Cie., Paris. TROWBRIDGE, W. P. Turbine Water-wheels. D. Van Nostrand & Co., New York. TURNEAURE, F. E., and RUSSELL, H. L. Public Water Supplies. John Wiley & Sons, New York, 1901. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. WILSON, HERBERT M. Pumping Water for Irrigation. Water Supply Paper No. i. U. S. Geological Survey, Washington, D. C., 1896. WOLFF, ALFRED R. The Windmill as a Prime Mover. John Wiley & Sons New York, 1890. CHAPTER XX RECLAMATION SERVICE OF THE UNITED STATES 418. The Reclamation Law. The full text of the reclama- tion law dated June 17, 1902,* is as follows: AN ACT Appropriating the receipts from the sale and disposal of public lands in certain States and Territories to the construction of irrigation works for the reclamation of arid lands. Be it enacted by the Senate and House of Representatives oj the United States 0} America in Congress assembled, That all moneys received from the sale and disposal of public lands in Arizona, California, Colorado, Idaho, Kansas, Mon- tana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Utah, Washington, and Wyoming, beginning with the fiscal year ending June thirtieth, nineteen hundred and one, including the surplus of fees and com- missions in excess of allowances to registers and receivers, and excepting the five per centum of the proceeds of the sales of public lands in the above States set aside by law for educational and other purposes, shall be, and the same are hereby, reserved, set aside, and appropriated as a special fund in the Treasury to be known as the "reclamation fund," to be used in the examination and survey for and the construction and maintenance of irrigation works for the storage, diversion, and development of waters for the reclamation of arid and semi-arid lands in the said States and Territories, and for the payment of all other expenditures provided for in this Act: Provided, That in case the receipts from the sale and disposal of public lands other than those realized from the sale and disposal of lands referred to in this section are insufficient to meet the requirements for the support of agri- cultural colleges in the several States and Territories, under the Act of August thirtieth, eighteen hundred and ninety, entitled "An Act to apply a portion of the proceeds of the public lands to the more complete endowment and support of the colleges for the benefit of agriculture and the mechanic arts, established under the provisions of an Act of Congress approved July second, eighteen hundred and sixty-two," the deficiency, if any, in the sum necessary for the support of the said colleges shall be provided for from any moneys in the Treasury not otherwise appropriated. SEC. 2. That the Secretary of the Interior is hereby authorized and directed to make examinations and surveys for, and to locate and construct as herein pro- vided, irrigation works for the storage, diversion, and development of waters, including artesian wells, and to report to Congress at the beginning of each regular session as to the results of such examinations and surveys, giving estimates of cost of all contemplated works, the quantity and location of the lands which can be irrigated therefrom, and all facts relative to the practicability of each irrigation *Stat. L., vol. xxxii., p. 388. 564 THE RECLAMATION LAW 565 project; also the cost of works in process of construction as well as of those which have been completed. SEC. 3. That the Secretary of the Interior shall, before giving the public notice provided for in section four of this Act, withdraw from public entry the lands required for any irrigation works contemplated under the provisions of this Act, and shall restore to public entry any of the lands so withdrawn when, in his judg- ment, such lands are not required for the purposes of this Act; and the Secretary of the Interior is hereby authorized, at or immediately prior to the time of begin- ning the surveys for any contemplated irrigation works, to withdraw from entry, except under the homestead laws, any public lands believed to be susceptible of irrigation from said works: Provided, That all lands entered and entries made under the homestead laws within areas so withdrawn during such withdrawal shall be subject to all the provisions, limitations, charges, terms and conditions of this Act; that said surveys shall be prosecuted diligently to completion, and upon the completion thereof, and of the necessary maps, plans, and estimates of cost, the Secretary of the Interior shall determine whether or not said project is practi- cable and advisable, and if determined to be impracticable or unadvisable he shall thereupon restore said lands to entry; that public lands which it is proposed to irrigate by means of any contemplated works shall be subject to entry only under the provisions of the homestead laws in tracts of not less than forty nor more than one hundred and sixty acres, and shall be subject to the limitations, charges, terms, and conditions herein provided: Provided, That the commutation provisions of the homestead laws shall not apply to entries made under this Act. SEC. 4. That upon the determination by the Secretary of the Interior that any irrigation project is practicable, he may cause to be let contracts for the construc- tion of the same, in such portions or sections as it may be practicable to construct and complete as parts of the whole project, providing the necessary funds for such portions or sections are available in the reclamation fund, and thereupon he shall give public notice of the lands irrigable under such project, and limit of area per entry, which limit shall represent the acreage which, in the opinion of the Secretary, may be reasonably required for the support of a family upon the lands in question; also of the charges which shall be made per acre upon the said entries, and upon lands in private ownership which may be irrigated by the waters of the said irriga- tion project, and the number of annual installments, not exceeding ten, in which such charges shall be paid and the time when such payments shall commence. The said charges shall be determined with a view of returning to the reclamation fund the estimated cost of construction of the project, and shall be apportioned equitably: Provided, That in all construction work eight hours shall constitute a day's work, and no Mongolian labor shall be employed thereon. SEC. 5. That the entryman upon lands to be irrigated by such works shall, in addition to compliance with the homestead laws, reclaim at least one-half of the total irrigable area of his entry for agricultural purposes, and before receiving patent for the lands covered by his entry shall pay to the Government the charges apportioned against such tract, as provided in section four. No right to the use of water for land in private ownership shall be sold for a tract exceeding one hun- dred and sixty acres to any one landowner, and no such sale shall be made to any landowner unless he be an actual bona fide resident on such land, or occupant thereof, residing in the neighborhood of said land, and no such right shall per- manently attach until all payments therefor are made. The annual installments shall be paid to the receiver of the local land office of the district in which the 566 RECLAMATION SERVICE land is situated, and a failure to make any two payments when "due shall render the entry subject to cancellation, with the forfeiture of all rights under this Act, as well as of any moneys already paid thereon. All moneys received from the above sources shall be paid into the reclamation fund. Registers and receivers shall be allowed the usual commissions on all moneys paid for lands entered under this Act. SEC. 6. That the Secretary of the Interior is hereby authorized and directed to use the reclamation fund for the operation and maintenance of all reservoirs and irrigation works constructed under the provisions of this Act: Provided, That when the payments required by this Act are made for the major portion of the lands irrigated from the waters of any of the works herein provided for, then the management and operation of such irrigation works shall pass to the owners of the lands irrigated thereby, to be maintained at their expense under such form of organization and under such rules and regulations as may be acceptable to the Secretary of the Interior: Provided, That the title to and the management and operation of the reservoirs and the works necessary for their protection and opera- tion shall remain in the Government until otherwise provided by Congress. SEC. 7. That where, in carrying out the provisions of this Act, it becomes neces- sary to acquire any rights or property, the Secretary of the Interior is hereby au- thorized to acquire the same for the United States by purchase or by condemna- tion under judicial process, and to pay from the reclamation fund the sums which may be needed for that purpose, and it shall be the duty of the Attorney-General of the United States upon every application of the Secretary of the Interior, under this Act, to cause proceedings to be commenced for condemnation within thirty days from the receipt of the application at the Department of Justice. SEC. 8. That nothing in this Act shall be construed as affecting or intended to affect or to in any way interfere with the laws of any State or Territory relating to the control, appropriation, use, or distribution of water used in irrigation, or any vested right acquired thereunder, and the Secretary of the Interior, in carry- ing out the provisions of this Act, shall proceed in conformity with such laws, and nothing herein shall in any way affect any right of any State or of the Federal Government or of any landowner, appropriator, or user of water in, to, or from any interstate stream or the waters thereof- Provided, That the right to the use of water acquired under the provisions of this Act shall be appurtenant to the land irrigated, and beneficial use shall be the basis, the measure, and the limit of the right. SEC. 9. That it is hereby declared to be the duty of the Secretary of the Interior in carrying out the provisions of this Act, so far as the same may be practicable and subject to the existence of feasible irrigation projects, to expend the major portion of the funds arising from the sale of public lands within each State and Territory hereinbefore named for the benefit of arid and semi-arid lands within the limits of such State or Territory: Provided, That the Secretary may tempo- rarily use such portion of said funds for the benefit of arid or semi-arid lands in any particular State or Territory hereinbefore named as he may deem advisable, but when so used the excess shall be restored to the fund as soon as practicable, to the end that ultimately, and in any event, within each ten-year period after the passage of this Act, the expenditures for the benefit of the said States and Terri- tories shall be equalized according to the proportions and subject to the conditions as to practicability and feasibility aforesaid. SEC. 10. That the Secretary of the Interior is hereby authorized to perform SCOPE OF RECLAMATION LAW 567 any and all acts, and to make such rules and regulations as may be necessary and proper for the purpose of carrying the provisions of this Act into full force and effect. 419. Scope of Reclamation Law. The first step in any action taken under the law is a request from the engineers of the recla- mation service, made through the head of the organization, the Director, to the Secretary of the Interior, for the withdrawal from entry of certain specified lands with a view to their examination in the field, in order to determine the practicability of construct- ing irrigation works for reclaiming them. When this request is approved by the Secretary of the Interior, the proper steps are taken, by the General Land Office, for the withdrawal of the lands, through the local land office for the district in which they are located. Thereafter no entries will be allowed except, under the provisions of the homestead law, as modified by the limitations and conditions of the act. In accordance therewith they may be limited to an area as small as 40 acres, and will not be subject to the commutation provisions of the homestead law. The entry- man may, therefore, be required to reduce the area of his entry to such limit as in the opinion of the Secretary of the Interior may be reasonably required for the support of a family, and will be called upon to pay the charges per acre which may be determined on in not more than ten annual installments. As soon as possible after such withdrawal, engineers are instructed to make the survey of the lands of proposed canals and reservoirs; also to conduct necessary engineering investi- gations concerning the water-supply and the conditions under which the construction will be carried on. Upon the comple- tion of this work the results are summarized and submitted to the Secretary of the Interior, with such recommendations as may be deemed advisable by the Director, together with maps, plans, and estimates of cost. It then becomes the duty of the Secretary of the Interior to determine whether or not such project is practicable and advis- able. If determined to be impracticable or inadvisable, he re- stores to the public domain the lands withdrawn, and they be- come subject to the public-land laws, as if such withdrawal had 568 RECLAMATION SERVICE never been made. If the project is approved by the Secretary of the Interior, he may cause contracts to be let for the construc- tion of the proposed works, either as a whole or for such portion or section as will constitute a complete system, if it should be deemed best not to undertake the entire project at that time. He will thereupon give public notice of the land which may be reclaimed thereunder, and of the particular limitations contem- plated by the law as to area, cost, number of installments, date of payments, etc. As soon as it shall be possible to furnish water for the irri- gation of any particular portion of the lands involved, the entry- men thereon will be allowed to take the water; and as construc- tion progresses additional lands will be supplied from time to time. When payments have been made in full for the major portion of the lands irrigable under any system, the management and operation of the irrigation works will pass to the owners of the land irrigated therefrom, to be maintained at their expense, under such form of organization and under such rules and regu- lations as may be acceptable to the Secretary of the Interior; it is provided, however, that the title to the reservoirs and the works necessary for their protection and operation shall remain in the Government, and that they shall continue under the con- trol and management of the Government unless otherwise pro- vided by Congress. The examination of the title to the lands involved in each irrigation project must be made before construction can begin in order to determine how much of each tract is public or pri- vate land. In connection with the right of way for canals to be constructed by the reclamation service, by decisions of the Secre- tary of the Interior of October 5, 1893 (Decisions of the Depart- ment of the Interior Relating to Public Lands, Vol. 17, page 521), it has been held that all lands entered subsequent to Octo- ber 2, 1888, are subject to a right of way for ditches or canals constructed by the authority of the United States, in pursuance of an Act of August 30, 1890 (26 Stat. L., p. 391). In each project for reclamation there are involved tracts of WATER USERS' ASSOCIATION 569 lands under private ownership and waters claimed by individuals, and it is necessary to make a careful examination of their charac- ter, the title, etc. In obtaining this information, it is necessary to discover how much water was being used per acre of land irrigated, and to report how much land was irrigated and from what sources. The use of public lands for right of way for canals and laterals constructed by the reclamation service is provided for by the Act of October 2, 1888 (25 Stat. L., 526). There is also a reser- vation of right of way for canals constructed by the United States affecting all lands disposed of subsequent to that date. 420. Water Users' Association. When it appears probable that any particular project will be carried into effect, steps are taken looking toward the organization of an association of people owning land under the project. The object of this association is to secure prompt and effective dealing between the Secretary of the Interior and the water users. The latter should have a common agent, as officers, with whom business may be trans- acted. The first association formed to carry out the purpose of the law is the Salt River Valley Water Users' Association, the articles of incorporation of which were prepared after long discussion and consultation with legal advisors, engineers, and landowners. In forming such associations among other points to be considered is that they shall be organized simply for the purpose of carrying out the provisions of the law and not for speculative purposes. They should be constituted solely for the purpose of acquiring, maintaining, and operating the irrigation works at their own expense. The necessity for the formation of these associations results from each owner of land having his own preference regard- ing details of management, which should be fully discussed in public meetings by all interested water users, that a majority view may be presented to the officers of the reclamation service. This is particularly true concerning details of water distribution, while on the other hand the ownership, management, and opera- tion of the storage works and main diversion canals remain by law in the hands of the reclamation service. 570 RECLAMATION SERVICE The members of the Salt River Valley Water Users' Association at the time of its incorporation in 1903, pledged their lands to the amount of 200,000 acres for the return to the United States of the cost of the reservoir and auxiliary works. A contract was approved by the Secretary of the Interior and later adopted by the Association early in 1904, which reads as follows: These articles of agreement, made and entered into this 25th day of June, 1904, by and between the United States of America, acting in this behalf by Ethan A. Hitchcock, Secretary of the Interior, party of the first part, and the Salt River Valley Water Users' Association, a corporation duly organized and existing under the laws of the Territory of Arizona, party of the second part, their successors and assigns, witnesseth: That whereas the Salt River Valley Water Users' Association is a corporation organized and existing under the laws of the Territory of Arizona for the purpose mentioned in its articles of incorporation, a copy of which is appended to this memorandum (which is marked "Articles of incorporation referred to in the attached memorandum, and attested by the signature of the honorable the Secre- tary of the Interior of the United States of America and of the president of the Salt River Valley Water Users' Association, for the purpose of identification"), and are for every purpose of the interpretation, construction, and consideration of this memorandum, and of the rights of the parties hereunder, to be deemed, held, read and considered as if fully written out or printed herein, and deemed a part hereof. And whereas the lands embraced within the district of lands described in Sec- tion 3 of Article IV of said articles of incorporation are naturally desert and arid and incapable of proper cultivation without irrigation, and unless the waters of the Salt and Verde rivers in Arizona and their tributaries be impounded and the flow thereof otherwise regulated and controlled will, to a greater or less extent, remain unreclaimed, unfit for habitation and uncultivated, in which condition they, or a great part thereof, are now. And whereas the Secretary of the Interior of the United States of America con- templates the construction of certain irrigation works under the provisions of an Act of Congress entitled "An act appropriating the receipts from the sale and disposal of public lands in certain States and Territories to the construction of irrigation works for the reclamation of arid lands," approved June 17, 1902, in and across Salt River at a point about 32 miles up the course of said Salt River above the confluence of the Verde River and said Salt River, said point being near the mouth of Tonto Creek, for the purpose of there impounding the waters of said Salt River and otherwise regulating and controlling the flow of water there- in, and works necessarily or conveniently incident thereto, for the use of said waters for the reclamation of arid lands along the course of said Salt River; and Whereas the incorporators of said Salt River Valley Water Users' Association and its shareholders are, and under the provisions of its articles of incorporation must be, owners and occupants of land and the appropriators of water from said Salt River and said Verde River and their respective tributaries for the irrigation WATER USERS' ASSOCIATION 571 thereof, and in addition thereto such incorporators, shareholders, and constitu- ents, and their assigns or successors, must initiate rights to the use- of water from the said proposed irrigation works, to be constructed by the said Secretary of the Interior, as soon as such rights may be initiated, and thereafter complete the acquisition thereof in the manner and upon the terms and conditions to be prescribed therefor by the Secretary of the Interior, which rights shall be, and thereafter continue to be, forever appurtenant to designated lands owned by such shareholders and constituent members; and Whereas neither the relative priority and extent of the individual appropria- tions of such water heretofore made by said incorporators, shareholders, and con- stituent members, nor the proportion of the entire waters of said water courses that has been in the aggregate appropriated by them, and which are now vested rights, have been ascertained or determined, but said incorporators, shareholders, and constituent members of said association have agreed among themselves, by the terms and provisions of said articles of incorporation, upon the rules and prin- ciples by and upon which the relative priority and the extent of their several ap- propriations and vested rights to the use of such waters shall be determined. r. Now, therefore, if the said Secretary of the Interior shall authorize and shall cause the construction of said irrigation works, then in the determination of the relative rights of the shareholders of said association, and of their respective rights to the use of water acquired from the Government under said Act of Con- gress, the rules and principles set out in said articles of incorporation for such de- termination shall be deemed the established rules and principles for that purpose. 2. That only those who are, or who may become members of said association, under the provisions of its articles of incorporation, shall be accepted as entrymen or applicants for rights to the use of water impounded, developed, or the supply of which is or may be regulated or controlled by said proposed irrigation works. 3. That the aggregate amount of such rights to be issued shall in no event exceed the number of acres of land capable of irrigation by the total amount of water available for the purpose, being (i) the amount now appropriated by the shareholders of said association, and (2) the amount to be impounded and de- veloped in excess of the water now appropriated. The Secretary of the Interior shall determine the number of acres so capable of such irrigation as aforesaid, his determination to be made upon due and expert consideration of all available data, and to be based upon and measured and limited by the beneficial use of water. 4. That the payments for the reservoir rights to be issued to the shareholders of said association, under the provisions of said Act of Congress, shall be divided into not less than ten equal annual payments, the first whereof shall be payable at the time of the completion of said proposed reservoir, or within a reasonable time thereafter, and after due notice thereof by the Secretary of the Interior to the association. The cost of said proposed irrigation works shall be apportioned equally per acre among those acquiring such rights. 5. The said Salt River Valley Water Users' Association agrees that it will promptly collect or require prompt payment in such manner as the Secretary of the Interior may direct, and hereby guarantees the payments for that part of the cost of the irrigation works which shall be apportioned by the Secretary of the Interior to its shareholders, and promptly pay the sums collected by it to the re- ceiver of the local land office for the district in which said lands are situate; that 572 RECLAMATION SERVICE it will promptly employ the means provided and authorized by the said articles of incorporation for the enforcement of such collections, and will not change, alter, or amend its articles of incorporation in any manner whereby such means of col- lection, or the lien given to it by the shareholders to secure the payment thereof, or of any assessments contemplated or authorized thereby, shall be impaired, di- minished, or rendered less effective, without the consent of the Secretary of the Interior. 6. The United States shall in no manner be responsible for the sums collected by said association until they have been paid into the hands of the receiver of the local land office, as provided by the law, and in accordance with such regula- tions as may be prescribed by the Secretary of the Interior. 7. That for the purpose of enforcing said collections, the association will adopt and enforce proper by-laws, subject to the approval of the Secretary of the In- terior, and not change them so as to in anywise impair their efficiency for said pur- pose, and will otherwise do any and all things it is authorized and empowered to do in the premises. 8. That the association will adopt and enforce such rules and regulations as it is authorized by its articles of incorporation to adopt and enforce concerning the use of water by its shareholders and concerning the administration of the affairs of the association, to effectually carry out and promote the purposes of its organ- ization, within the provisions of said articles of incorporation, which rules and regulations shall be subject to the approval of the Secretary of the Interior. That if the association fail to make and adopt such rules and regulations, then the Secre- tary of the Interior may prescribe them; but in such event it is understood that the Secretary of the Interior shall impose no rule or regulation interfering with any vested right of the shareholders of the association as defined or modified by said articles of incorporation. 9. Persons who are not now members of the association, but who may be the owners or occupants of land within the reservoir district described in Section 3 of Article IV, or of added lands provided for in that section and to whom rights to the use of water, from the proposed reservoir or irrigation works, may be issued, may, at the designation of the Secretary of the Interior, become members of the association by subscribing to the stock thereof, and upon the compliance with the other conditions prescribed for such membership. 10. It is understood that in all the relations between the Government and this association and the members of the association the rights of the members of the association are to be defined and determined and enjoyed by and under the pro- visions of the said Act of Congress and of other Acts of Congress on the subject of the acquisition and enjoyment of the rights to use water, and by the laws of Arizona where not inconsistent therewith, where such rights have vested, modified, if modified at all, by the provisions of the articles of incorporation of said associa- tion. ii. Nothing contained in this memorandum, or to be implied from the fact of its execution, shall be construed, held, or deemed to be an approval by the Secre- tary of the Interior, nor an adoption by him, of the articles of incorporation of said association, in all their details as the form of organization of water users con- templated and authorized by Section 6 of the said Act of Congress of June 17, 1902; but such approval and adoption is expressly reserved until the conditions SPECIFICATIONS, RECLAMATION SERVICE 573 authorizing such approval and adoption prescribed in said act shall have arisen. And when the Secretary of the Interior shall make, approve, and promulgate rules and regulations for the administration of the water to be supplied from such pro- posed irrigation works, such rules and regulations, and such modifications thereof as the Secretary may, from time to time, approve and promulgate, shall be deemed and held to be obligatory upon this association as fully and completely, and to every intent and purpose, as if they were now made, approved, promulgated, and written out in full in this memorandum, and are to be read and construed as if so done. In witness whereof the undersigned have hereunto subscribed their names and affixed their seals the day and year first herein written. ETHAN A. HITCHCOCK, Secretary of the Interior, For and on behalf of the United States of America, party of the first part. [Departmental seal.] Witness: W. SCOTT SMITH, SALT RIVER VALLEY WATER USERS' ASSOCIATION, Party of the second part. By B. A. FOWLER, President. FRANK H. PARKER, Secretary. [Corporate seal.] Witness: JOSEPH H. KIBBEY, C. G. WILLIAMS. 421. Specifications, Reclamation Service. The following is a typical specification: Specifications, Roosevelt Dam. GENERAL CONDITIONS. 1. Form of proposal and signature. The proposal must be made on the form provided for that purpose, inclosed in a sealed envelope, and marked and addressed as required in the advertisement, stating, in writing and in figures, the sum of money for which the bidder proposes to supply the materials and perform the work required by the drawings and specifications, the unit prices, and the separate estimates called for in the proposal. It must be signed with the full name and address of the bidder; if a co-partnership, the co-partnership name by a member of the firm, with the name and address in full of each member; and if a corporation, by an officer in the cor- porate name, with the corporate seal attached to such signature. No telegraphic proposal or telegraphic modification of proposal will be considered. 2. Proposals. All blank spaces in the proposal must be filled in, and no change shall be made in the phraseology of the proposal, or addition to the items mentioned therein. Any conditions, limitations, or provisos attached to a proposal will be liable to render it informal and may cause its rejection. Alterations by erasure or 574 RECLAMATION SERVICE interlineation must be explained or noted in the proposal over the signature of the bidder. If a bidder wishes to withdraw his proposal he may do so before the time fixed for the opening, without prejudice to himself, by communicating his purpose in writing to the officer who holds it. No bids received after the time set for opening the proposals will be considered. 3. Certified check. Each bidder must submit with his proposal a certified check for the sum stated in the advertisement, drawn to the order of the Secretary of the Interior; and if, for any reason whatever, the bidder withdraws from the competition after the opening of the bids or refuses to execute the contract and bond as required, if his bid is accepted, the proceeds of said check shall become the prop- erty of the United States. Checks submitted by the unsuccessful bidders will be returned after the approval of the contract and bond executed by the successful bidder. 4. Eight-hour law and foreign labor. In all construction work eight hours shall constitute a day's work, and no Mongolian labor shall be employed thereon. The importation of foreigners and laborers under contract to perform labor in the United States or the Territories or the District of Columbia is prohibited. (Section 3738, Rev. Stat., U. S.; act Aug. i, 1892, 27 Stat. L., 340; section 4, act June 17, 1902, 32 Stat. L., 388; acts Feb. 26, 1885, and Feb. 23, 1887, 23 Stat L., 332 and 414.) 5. Award. The bidder to whom award is made will be required to enter into a written contract with the United States, with good and approved security as herein specified, within ten days after receiving such contract for execution. The contract which the bidder promises to enter into shall be, in its general provisions, in the form adopted by the Reclamation Service, copies of which can be inspected at its offices and will be furnished, if desired, to parties proposing to bid. If the bidder to whom the first award is made should fail to enter into a contract as herein pro- vided, then the award may be annulled and the contract let to the next most desirable bidder in the opinion of the Secretary of the Interior; and such bidder shall be required to fulfill every stipulation embraced herein as if he were the original party to whom the award was made. A copy of the advertisement and of the general conditions and detail specifications will be attached to and form part of the contract. A corporation to which a contract is awarded will be required, before the contract is finally executed, to furnish certificate as to its corporate existence, with evidence to show that the officer signing the contract is duly authorized to do so on behalf of the corporation. 6. Contractor's bond. The contractor will be required to give a bond in the sum of 20 per cent, of the amount of the contract, unless a different amount is specified in the advertisement or proposal, conditioned upon the faithful performance by the contractor of all the covenants, stipulations, and agreements in the contract. If at any time during the continuance of the contract the sureties, or any of them, shall die, or become irresponsible in the opinion of the Secretary of the Interior, he shall have the right to acquire additional and sufficient sureties, which the con- tractor shall furnish to the satisfaction of that officer within ten days after notice, and in default thereof the contract may be annulled by the Secretary of the Interior and the work carried to completion in the manner provided in the contract. 7. Transfers. Transfers of a contract, or of any interest therein, is prohibited by law. 8. Engineer. Where the word "engineer" is used in the general conditions 01 SPECIFICATIONS, RECLAMATION SERVICE 575 detail specifications, or in the contract, it shall be and is mutually understood to refer to the chief engineer of the Reclamation Service, or any of his authorized assistants or inspectors, limited by the particular duties intrusted to them. The engineer wil give the locations and the grades for the work, and no work depending on such locations and grades will be commenced until these have been established. It shall be his duty to point out to the contractor any neglect or disregard of the plans, specifications, and general conditions of the contract. Upon all questions concerning the execution of the work and the classification of the material, in accord- ance with the specifications, the decision of the engineer shall be binding on both parties. All materials furnished and all work done shall be subject to rigid inspec- tion, and if not in accordance with the specifications, in the opinion of the engineer, shall be made to conform thereto. Unsatisfactory material will be rejected and shall be immediately removed from the premises, at the cost of the contractor, if so ordered by the engineer. 9. Contractor. Whenever the word "contractor" is used, it shall be held to mean the party, firm, or corporation with whom the contract is made by the United States for the construction of the work, the agent of this party who may be appointed to represent him in the execution of the work, or the legal representatives of the contractor. The foreman in charge of the work will be held to represent the con- tractor during the absence of the latter or his designated agent. 10. Foreman and copy of plans, etc. The contractor shall at all times keep upon the work a copy of the plans and specifications, so that reference may be made thereto by the engineer, in case of misunderstanding or misconstruction. In- structions given to the contractor's foreman or agent on the work, by the engineer, shall be considered as having been given to the contractor himself. 11. Railroad rates. Special concessions of rates have been obtained from certain railroad companies foe the benefit of the United States, which are applicable in favor of contractors on this work. Full information concerning the same can be obtained from the engineer in charge of the project. Bidders should make allowance for these concessions. 12. Local conditions. Bidders must satisfy themselves as to the nature of the material and as to all local conditions affecting the work, and no information derived from the maps, plans, specifications, profiles, or drawings, or from the engineer or his assistants, will in any way relieve the contractor from any risks or from ful- filling all the terms of his contract. 13. Damages. The contractor will be held responsible for and, when possible, be required to make good, at his own expense, any and all damages, of whatsoever nature, to persons or property caused by carelessness, neglect, or want of due pre- caution on the part of the contractor, his agents, employees, or workmen. He will not allow any of his agents, employees, or workmen to trespass upon the premises or lands of persons in the vicinity of the works, and will discharge, at the request of the engineer, anyone in his employ who may be guilty of committing such damage. 14. Drawings and specification requirements. Any drawings or plans which may be listed in the detail specifications shall, together with such detail specifications, be regarded as forming part hereof and of the contract. The engineer will furnish from time to time such detail drawings, plans, profiles, and special specifications as may be necessary to enable the contractor to complete the work in a satisfactory manner. The general conditions and detail specifications shall apply to all work 576 RECLAMATION SERVICE done or material furnished, and shall control the special specifications, where the latter are silent. In case of conflict in the general conditions, the detail specifica- tions, and the special specifications, the last shall control in the particular work to which they apply. 15. Experience. Bidders must, if required, present satisfactory evidence that they have been regularly engaged in the business of constructing such work as they propose to execute, and that they are fully prepared with the necessary capital, machinery, and material to begin the work promptly and to conduct it to the satis- faction of the Department. 1 6. Character of workmen. The contractor shall discharge from his service, when required by the engineer, any disorderly, dangerous, insubordinate, or incom- petent person employed on or in the vicinity of the works under construction by the United States. None but skilled foremen or workmen shall be employed on work requiring special qualifications, as tunnels, concrete work, etc. 17. Methods and appliances. The methods and appliances adopted by the contractor must be such as will secure a satisfactory quality of work and will enable him to complete the work in the time agreed upon. If at any time such methods and appliances appear inadequate, the engineer may order the contractor to improve their character, or increase their efficiency, and the contractor must conform to such order; but the failure of the engineer to order such improvement of methods or increase of efficiency will not relieve the contractor from his obligations to perform good work or finish it in the time agreed upon. 1 8. Material and workmanship. All materials must be of the specified quality and fully equal to approved samples, when samples are required. All work must be done in a thorough workmanlike manner by mechanics skilled in their various trades, notwithstanding any omission from the drawings or specifications; and anything mentioned in the specifications and not shown in the drawings, or shown in the drawings and not mentioned in the specifications, must be done as though shown or mentioned in both. 19. Samples. The contractor shall submit samples of any or all materials pro- posed to be used in the work if required to do so by the engineer. 20. Delays. The contractor shall not be entitled to any compensation for delays or hindrances to the work from any cause whatever. Extension of time will be allowed for unavoidable delays, such as may result from causes which, in the opinion of the engineer, approved by the Secretary of the Interior, are undoubtedly beyond the control of the contractor, such as acts of Providence, fortuitous events, or the like. If any delay or hindrance is caused by specific instructions on the part of the Secretary of the Interior or the engineer, or by their failure to provide material sufficient to carry on the work, or to give such instructions as may be necessary for the same, or to provide necessary right of way, then such delay will entitle the con- tractor to an extension of time equivalent to the time lost by such delay. The engineer must receive from the contractor a written notice of claim for such delay before any extension of time will be allowed. Any extension of time, however, shall not release the sureties from their obligation, which shall remain in full force and effect until the discharge of contract. In case the contractor should fail to complete the work in the time agreed upon in the contract, or in such extra time as may have been allowed for delays as herein provided, the engineer shall compute and appraise the direct damages for the loss sustained by the United States on account of further SPECIFICATIONS, RECLAMATION SERVICE 577 employment of engineers, inspectors, and other employees, including all disburse- ments on the engineering account, properly chargeable to the work as liquidated damages. The amount so appraised and computed shall be deducted from any money due the contractor under his contract. The decision of the chief engineer as to the appraisal of such damages shall be final and binding on both parties. Any provisions in the detail specifications concerning deduction for delay shall be held as modifying or revoking the provisions herein. 21. Suspension oj contract. Should the contractor fail to begin the work within the time required, or fail to begin the delivery of material as provided in the contract, or fail to prosecute the work or delivery in such manner as to insure a full compliance with the contract within the time limit, or should any question arise as to whether or not the contractor is properly carrying out the provisions of his contract in their true intent and meaning, at any time during the progress of the work, notice thereof in writing shall be served upon him, and upon his neglect or refusal to provide means for a more energetic and satisfactory compliance with the contract within the time specified in such notice, then and in either case the Secretary of the Interior shall have the power to suspend the operation of the contract, and he may take possession of all machinery, tools, appliances, and animals employed on any of the works to be constructed under the contract and of all materials belonging to the contractor delivered on the ground, and may use the same to complete the work, or he may employ other parties to carry the contract to completion, substitute other machinery or materials, purchase the material contracted for in such manner as he may deem proper, or hire such force and buy such machinery, tools, appliances, materials, and animals at the contractor's expense as may be necessary for the proper conduct of the work and, for finishing it in the time agreed upon. Any excess of cost arising therefrom over and above the contract price will be charged against the contractor and his sureties, who shall be liable therefor. The failure to order improvement of methods or increase of force, plant, or efficiencies will not relieve the contractor from his obligation to perform good work or finish in the time agreed upon. 22. Climatic conditions. The engineer may order the contractor to suspend any work that may be damaged by inclemency of the weather or other climatic conditions (as, for example, excessive cold or heat) and due allowance shall be made to the contractor for the time actually lost by him on account of such suspension. 23. Quantities. The quantities given in the proposal are for the purpose of comparing bids, and are approximate only, and no claim shall be made against the United States on account of any excess or deficiency, absolute or relative, in the same. 24. Changes. The Secretary of the Interior reserves the right to make such changes in the specifications of work or material at any time as may be deemed advisable, without notice to the surety or sureties on the bond given to secure com- pliance with the contract, by adding thereto or deducting therefrom, at the unit prices of the contract, or at such allowances for changes of materials as shall be deemed just and reasonable by the engineer, whose decision shall be binding on both parties. The right to make material changes in the quantities listed in the proposal is an essential part of the contract, and bidders must make their estimates accord- ingly. Should any change be made in a particular piece of work after it has been commenced, so that the contractor is put to extra expense, the engineer shall mako 37 578 RECLAMATION SERVICE reasonable allowance therefor, which action shall be binding on both parties. Claim of payment for extra work or for work not provided for in the specifications will not be allowed unless such work shall have been previously ordered in writing by the engineer. Demand for such extra payment must be accompanied by the certificate of the engineer that such work has been satisfactorily performed or the material furnished, and stating the amount to be allowed therefor, which amount, when no price for work of such kind is specified in the proposal, shall be the reason- able actual cost to the contractor, plus 15 per cent. Such demand must be made before the time of the payment following the completion of said extra work, or the furnishing of the material. 25. Structural difficulties. Should structural difficulties prevent the execution of the work as described in the plans and specifications, necessary deviations there- from may be permitted by the engineer, but must be without additional cost to the United States. 26. Inspection of work. The engineers and inspectors appointed by the Secre- tary of the Interior shall at all times have the right to inspect the work and materials. The contractor shall furnish such persons reasonable facilities for obtaining such information as they desire respecting the progress and manner of the work and the character of the material, including all information necessary to determine the cost of the work, such as the number of men employed, their pay, the time during which they worked on the various classes of construction, etc.- He shall, when required, furnish the engineer and his assistants meals and camp accommodations at reason- able prices at any camp under his control. Whenever the contractor shall decide to inaugurate night work, or to otherwise vary the period during which work is carried on each day, he shall give due notice to the engineer so that proper inspection may be provided for. Such work shall be done under regulations to be furnished in writing by the engineer, and no extra compensation shall be allowed therefor. 27. Removal of defective work. The contractor shall remove and rebuild, at his own expense, any part of the work which has been improperly executed, even though such work should have been already allowed for in the monthly estimates. The engineer shall give to the contractor written notice of such defective work, when found. If the contractor refuses or neglects to replace such defective work, it may be replaced by the United States at the contractor's expense. 28. Protection of finished work and cleaning up. The contractor will be held responsible for any material furnished to him, and for the care of any finished work until final completion of the work, and will be required to make good, at his own cost, any damage or injury it may sustain from any cause. He shall take all risks from floods and casualties of every description and make no charge for detention from such causes. He may, however, be allowed a reasonable extension of time on account of such detention, as provided herein. The contractor shall remove all rubbish and unused material upon completion of the work, and place the premises in a condition satisfactory to the engineer. 29. Errors and omissions. The contractor will not be allowed to take advantage of any error or omission in these specifications, as full instructions will always be given should such error or omission be discovered. 30. Roads and fences. All roads crossing the work, and subject to interference therefrom, must be kept open until proper bridges or crossings are provided if SPECIFICATIONS, RECLAMATION SERVICE 579 necessary, and all fences crossing the work must be kept up by the contractor until the work is finished. 31. Bench-marks, stakes, etc. All bench-marks and side-slope stakes must be carefully preserved by the contractor, and in case of their willful or careless destruc- tion or removal by him or any of his employees such stakes shall be replaced by the engineer at the contractor's expense. 32. Right oj way. The right of way for the works to be constructed and for all necessary borrow-pits, spoil-banks, ditches, roads, etc., will be provided by the United States. 33. Sanitation. The chief engineer may establish rules for sanitary and police regulations for all forces employed under this contract; and should the contractor fail to enforce these rules, the engineer may enforce them and assess against the contractor the cost thereof, which will be deducted from any sum due on the contract. 34. Use of liquor. The use and sale of intoxicating liquor will be absolutely prohibited on the work except under the direction and supervision of the engineer or his agent, and then only for medicinal purposes. 35. Claims for work and material. The contractor shall promptly make pay- ments to all persons supplying labor and materials in the prosecution of the work, and a condition to this effect shall be incorporated in the bond to be given by the contractor, in pursuance of the act of Congress approved August 13, 1894 (28Stat., 278). 36. Payments. The payments due shall be made to the contractor upon the presentation of proper accounts, prepared by the engineer and approved by the chief engineer, in accordance with the provisions made therefor and pertaining to the contract. When the work has been completed or all the material has been delivered, to the satisfaction of the chief engineer, and when a release of all claims against the United States on account of the contract shall have been executed by the contractor, final payment of the balance due will be made. DETAIL SPECIFICATIONS. 37. Object oj the work. The object of the work is the construction of a masonry dam in the canyon of the Salt River below the mouth of Tonto Creek, Ariz., for the purpose of impounding about 1,000,000 acre-feet of water. Two spillways, each about 200 feet long, carry the flood waters around the dam. A roadway is carried across the dam, crossing the spillways on concrete-steel bridges. The general dimensions of the dam are as follows: FRET. Height of spillway above datum or mean low water 210 Height of roadway above datum or mean low water 230 Lowest point of foundation below datum 36 Length of dam at datum 210 Length of dam at spillway 780 38. List of drawings. No. i. Plan of east half of dam, abutment, and spillway. No. 2. Plan of west half of dam, abutment, and spilhvay. No. 3. Cross-section of dam. No. 4. Plan, cross-sections, and elevation of bridges and piers. 580 RECLAMATION SERVICE 39. Diversion. Floods exceeding 4,000 second-feet are liable to go over the dam. The river, at low stage, shall be diverted through the tunnel or temporary flume by means of a temporary diversion dam not less than 12 feet high above the bottom of the tunnel, and made as tighUas practicable with sheet-piling securely connected with the dam. The stream shall be conducted well below the vicinity of the dam before discharging into the river. A row of sheet-piling shall also be driven across the canyon below the dam site to prevent the return of water by seepage. As soon as practicable a tight wooden flume, not less than 50 feet wide afnd 5 feet deep, shall be provided, leading from a level 5 feet below the top of the diversion dam and discharging below outlet of tunnel. The construction of dams, cofferdams, flumes, and all other diversion and protection works shall be done at the contractor's cost without extra compensation. The necessary lumber for such works will be furnished, after due notice, by the United States at the dam site at the rate of $25 per M feet, board measure, the charge therefor to be deducted in the monthly statements of amounts due the contractor. No sawed lumber over 22 feet in length can be furnished. 40. Excavation. All material will be measured in place, and the material excavated from the foundation shall be paid for in three classes, viz. : Class i. Loose material consisting of sand, gravel, and bowlders of less than 10 cubic feet, and all other material which may occur excepting solid rock in place. Class 2. Solid rock in place, lying below the datum, which is about low-water surface, and bowlders of 10 cubic feet or larger. Class 3. Solid rock in place above the datum. 41. Foundation. The foundation shall be thoroughly cleaned of all gravel, sand, and earth, and all fissured or disintegrated rock shall be removed so that the dam shall be founded on solid rock throughout, and in such manner as required by the engineer in charge. Explosives shall not be used in excavating the rock in the foundation unless absolutely necessary; and when used, shall be in small quantities only, and in a manner approved by the engineer. A trench shall be cut in the solid rock of the foundation 15 feet from the heel of the dam, and parallel thereto, and shall be 10 feet wide and 6 feet deep below the bottom of the dam on the line of the trench. 42. Removal of temporary works. All cofferdams or other temporary works shall be removed by the contractor, free of cost, at such times as the engineer may direct. 43. Side walls. Above the bed of the river the side walls shal be cut away until they present surfaces normal to the face of the dam suitable, in the judgment of the engineer, for solid and safe junction with the masonry. This shall be paid for by the cubic yard as solid rock at the price agreed upon in the contract; any earth or loose material occurring in the side walls will be small in amount and shall be re- moved by the contractor without extra charge. 44. Overhaul. All material excavated from the foundations and side walls shall be placed where directed by the engineer. Whenever the engineer may require any material transported more than 300 feet from the point of excavation the distance over 300 feet will be paid for as overhaul at the price agreed upon in the contract. 45. Masonry. The main body of the dam shall be constructed of broken range cyclopean rubble, laid so as to break joints and thoroughly bond the work in all SPECIFICATIONS, RECLAMATION SERVICE 581 directions. The stone shall be quarried from the walls on each side of the canyon shown in the drawing as proposed spillways. If a sufficient quantity of hard fine- grained stone can not be obtained in these spillways it shall be quarried from the bluffs at either end of the dam at locations designated by the engineer, at the con- tractor's expense. Each stone shall be thoroughly drenched and cleaned of dirt and laid in Portland cement mortar of the quality hereafter specified. Vertical joints between the stonts inside of the face stone of the dam must be nowhere less than 6 inches, and must be thoroughly filled with Portland cement concrete, or mortar, which should be rammed into place by hand, to the end that all space in the dam not occupied by stone shall be absolutely filled with mortar. Spalls may be rammed into the mortar in the vertical joints and rock may be rammed into the concrete where the joints are large enough. No rock shall come nearer to another than 2 inches. All overhanging edges shall be hammered off, and concave or otherwise improper beds are prohibited. The aim shall be to use the largest pro- portion of stone and the smallest proportion of mortar and concrete in the dam that can be practically secured. To this end facilities shall l>e provided for handling stones weighing 10 tons, and large stones shall be used as far as practicable. 46. Water-pipes. The contractor shall provide water-pipes on the work, by which at any time any portion of the masonry may be thoroughly wet, and these shall be used whenever required by the engineer. All masonry shall be kept wet during the time of construction and until the work is at least six days old. 47. Up-stream /ace. The stone for the up-stream face shall be selected so as to lie with horizontal beds and vertical joints in Portland-cement mortar, composed of i part cement to 2 parts sand. No mortar joint in the face shall exceed 2 inches in thickness. At least one-third of the area in the face must be headers evenly distributed throughout the wall, and every header shall be laid over a stretcher of the underlying course. The stone shall be so arranged as to break joint in no case less than i foot with the stone of the underlying course. The stretchers must be not less than 3 feet long nor less than 2 feet in any other dimension; the headers must not be less than 6 feet in length nor less than 2 feet in any other dimension. The joints in tlr's face of the dam shall be dug out to a depth of at least 3 inches and at such times as directed shall be carefully pointed by hand with mortar composed of equal parts of sand and cement, or with such material as shall be required by the engineer and furnished by the United States, and this shall be done as thoroughly as possible in order to make a water-tight surface. Immediately before pointing, the joints shall be thoroughly washed out with a hose. Projections of 12 inches or less beyond the lines of the drawings, will be permitted where they are of such symmetry as not to be unsightly. The face wall shall be kept at all times at least one course higher than the body of the dam opposite. 48. Down-stream face. The stone for the down-stream face shall be so selected as to lie with horizontal beds and vertical joints, and each stone shall be laid in a bed of cement mortar composed of sand and cement in the proportion directed by the engineer; where not otherwise directed the proportions shall be i part of cement to 2\ parts of sand. At least one-fourth of the area in the face must be headers evenly distributed throughout the wall, and every header shall be laid over a stretcher of the underlying course. The stone shall be laid in steps and shall have a proper bond with the stone of the underlying course. Projections of 2 feet or less beyond the lines of the drawing will be permitted where they are of such symmetry as not 582 RECLAMATION SERVICE to be unsightly. Payments will be made in every case for material within the neat lines of the drawing only. The face wall shall be kept at all times at least one course higher than the body of the dam opposite. 49. Wing walls. Two rubble-masonry wing walls of the same character of masonry as the body of the dam shall be constructed as shown in the drawings. The dimensions of these wing walls are dependent on the character of the rock and can only be accurately determined when the excavation is complete. 50. Outlet pipes. The United States reserves the right to require the insertion, in such manner as the engineer may direct, of large pipes for drawing water through the dam. All pipes to be built in the dam will be furnished by the United States at the dam site and shall be built in by the contractor. The price of laying to be included in the price for masonry and paid for by the cubic yard at the same rate as masonry. 51. Coping, etc. The coping, roadway, guide walls, bridge piers, bridges, gate shaft, and spillways shall be built and finished in a workmanlike manner as shown in the drawings. The contractor shall insert, in the position and manner designated by the engineer, such iron or steel as may be required and furnished by the United States. 52. Concrete. All concrete used in the dam shall be composed of Portland cement, sand, and broken stone, in the proportion by volume directed by the engi- neer. The run of crusher will be taken, the parts passing a |-inch screen being classed as sand. The sand shall be free from organic matter, and contain not more than 10 per cent of clay or other foreign mineral substance. Where not otherwise directed, the proportions of separate aggregates shall be i part of cement, z\ parts sand, and 4 parts of broken stone of such size as to pass through a 2-inch-mesh screen. 53. Sand. The contractor shall provide screens for ascertaining the proportion of materials of various sizes produced by the crusher, in order to enable the engineer to determine the necessary proportion of sand in the concrete; and he shall at inter- vals, when required, make such tests as may be necessary for this purpose without extra charge. Sand required in addition to the run of the crusher, or such sub- stitute as the engineer may adopt, will be furnished by the -United States at the dam site, without cost to the contractor. 54. Mixing. The mixing shall be done by a machine whenever practicable, and the style of machine shall be subject to approval by the engineer. Whenever the machine fails to perform the mixing thoroughly it must be made satisfactory or removed and another machine substituted. When from any cause resort to hand- mixing is necessary, this shall be done thoroughly and to the satisfaction of the engineer. 55. Water. The water used for mixing must be free from organic matter. The amount of water used both in mixing and seasoning the concrete after it it placed in the work must be satisfactory to the engineer. All concrete will be used as wet as will give good results and as the nature of the work will permit. 56. Cement. All cement will be furnished by the United States and will be delivered to the contractor near the cement mill in Tonto Basin. 57. Time of beginning work. Within twenty days after receipt of contract for signature the successful bidder shall execute the same and file a satisfactory bond. Within thirty days after notice of signature of contract by the Secretary of the SPECIFICATIONS, RECLAMATION SERVICE 583 Interior, the contractor shall begin work under the contract, and within ninety days thereafter shall have on the work as large a force as can be economically employed, and a plant adequate to prosecute the work in the most rapid and efficient manner practicable and carry it to completion as specified in the proposal. He shall employ three daily shifts of eight hours each on masonry construction, and shall provide an ample number of electric lights to efficiently illuminate all work in progress at night. The number of lamps and the type thereof shall be subject to the approval of the engineer. 58. Default. Should the contractor fail to begin the work within the time allowed, or fail to begin the delivery of material as provided in the contract, or fail to prosecute the work or delivery in such manner as to insure a full compliance with the contract within the time limit, or default in any other manner in the proper execution of the work, all the machinery, tools, appliances, and animals employed on any of the works to be constructed under the contract and all materials belonging to the contractor delivered on the ground shall be and become absolutely the prop- erty of the United States. 59. Deduction /or failure to complete. Bidders will state in their proposals the time in which they propose to complete the dam to a height of 150 feet above the datum, which datum is about low-water mark. Time is an element in the construc- tion of this work and will be considered in the examination and comparison of bids and the award of the contract therefor. If the work is not completed within the time agreed upon in the contract there will be deducted from all payments made on said work after the expiration of said time the sum of $250 per day for every day occupied in excess of the time agreed upon in the contract, as liquidated damages for the loss to the Government on account of engineering, superintendence, and the value of the operation of the irrigation works dependent thereon, said sum to be deducted from any amount due under the contract. 60. Completion. After the completion of the dam to the i5o-foot level, it shall be discretionary with the engineer whether masonry work on the dam be permitted during the months of June, July, August, and September, but work shall be prose- cuted vigorously and continuously during the remaining eight months of the year, at a rate per month of not less than two-thirds of that achieved during the construc- tion of the lower portion of the dam, considered in cubic yards of masonry laid. The contractor shall place in the masonry such iron and steel in such manner as the en- gineer may direct. The metal will be furnished at the dam site by the United States. The United States reserves the right to vary the section of the dam above the 150- foot level. The section shown on drawings is for comparison of bids only. 61. Power plant. The United States reserves the right to construct a power plant at or near the location shown in the drawings without hindrance from the con- tractor. The power house may be built by the same contractor as the one building the dam, by another contractor, or by the United States, as may best conserve the public interests. After the work on the power plant is begun, that portion of the dam adjacent to the left bank must be kept at least 10 feet higher than the rest of the dam, as a protection to the power house in case of overflow. The United States reserves the right to store and use the water in the reservoir up to a level 25 feet below the lowest point of the top of the masonry. 62. Power. Electric energy for all lights for construction purposes will be furnished free of charge at the darn. Electric energy for all power purposes required 584 RECLAMATION SERVICE by the contractor will be furnished at the dam, to be measured at the power plant and charged for at the rate of cent per horse-power hour up to a limit o/ 400 horse- power, and i cent per horse-power hour for all power in excess of 400 horse-power the charges therefor to be deducted in the monthly statements of amounts due the contrac- tor. The United States does not guarantee the delivery of more than 600 horse-power. 63. Repairs. Repairs required by the contractor will be performed when feasible in the repair shop attached to the cement mill, and will be charged at cost for necessary labor and material plus 15 per cent for use of tools. 64. Payment of employees. The contractor shall make such banking arrange- ments that his employees may not be subjected to loss in securing their wages. 65. Payments to contractor. Payments will be made to the contractor as follows: At the end of each calendar month the engineer shall make an approximate measure- ment of all the work done up to that date, and an estimate of the value of the same at the prices agreed upon in the contract. A deduction of 20 per cent shall be made from this estimated amount, and from the balance shall be deducted the amount of all previous payments. The remainder shall be paid to the contractor upon the presen- tation of proper accounts. The 20 per cent so deducted shall be retained by the Government until the work shall have been completed to the entire satisfaction of the chief engineer and the Secretary of the Interior, and then be payable to the con- tractor, his heirs, assigns, or legal representatives; provided, however, that in the event of default on the part of the contractor all of the moneys retained under this paragraph in the hands of the Government shall be and become absolutely the prop- erty of the United States in reimbursement of any damage which may result through the failure of the contractor to fully and satisfactorily comply with the terms and conditions of his contract. After 50 per cent of the work shall have been completed the foregoing deduction of 20 per cent shall no longer be made, but the contractor shall be paid the full value of the work done during each month. The balance due upon completion of the work shall be paid as provided in paragraph 36. 422. Unit Costs, Reclamation Service. The following are some of the unit costs of construction, both by contract and by force account, on Reclamation Sendee projects. These furnish excellent examples of prevailing prices in the arid regions in 1908. Comparative earthwork costs in the northwest are analyzed by chief engineer Arthur P. Davis as follows: Cold Springs Earth Dam, Umatilla Project, Oregon. COST OF PRINCIPAL EQUIPMENT. Items. Cost. Depreciation. One steam shovel, 7o-ton, z\ yd $14,147 $8,147 Four locomotives, i6-ton I5>i2i 7>5i Forty-five dump cars I 2>fi7 2 9,102 Four miles 3o-in. track, 35~lb. rails. . . . 25,187 20,447 Trestle 10,263 9*263 Sundries 270 Total $78,590 $54,280 UNIT COSTS, RECLAMATION SERVICE 585 The total depreciation on the equipment has been figured at $54,280. The total amount of gravel required is estimated at 590,000 cu. yd., making the cost of depreciation of plant per cubic yard moved, 9.2 cents. COST OF GRAVEL EMBANKMENT AND OF EARTH EMBANKMENT. Gravel Embankment: C'ents. Excavation by steam shovel 3.5 Hauling, railroad maintenance, etc 7.0 Spreading and mixing 8.8 Sprinkling i .o Rolling 5 Engineering, superintendence and general expense 5.7 Repairs 5 Depreciation of plant (> . a Total cost per cubic yard 36. 2 Earth Embankment: Loading and hauling g . 5 Spreading and mixing 3.8 Sprinkling i . i Rolling 8 Depreciation 4.2 Repairs 3 Engineering, superintendence and general expenses 3.7 Total cost per cubic yard 23 . 4 As the dam is approximately one-fourth loam and three-fourths gravel, the combined cost is 33 cents per cubic yard, measured in excavation. The thorough mixing and compacting causes a shrinkage of about 16 per cent., making the cost in embankment about 39 cents. Contract bid on the above Vork was 38 per cent, higher than cost as constructed on force account. 586 RECLAMATION SERVICE COST OF UPPER DEER FLAT EMBANKMENT, PAYETTE PROJECT, IDAHO. Per yard. Excavation 6.3 Hauling 8.3 Spreading 1.8 Sprinkling 1.8 Rolling 1.3 Depreciation 4.1 Engineering, superintendence and general expenses 3.9 Total cost per cubic yard 27.5 Eliminating the items of engineering and general administra- tive expenses, which would have been incurred had the work been contracted, there would have been a cost of about 26 cents per yard, as against the lowest bid price of 36 cents. COST OF EARTHWORK ON BELLE FOURCHE DAM, SOUTH DAKOTA. Steam shovel Grader Item. work. work. 305,000 cu. yd. 199,000 cu. yd. Loading $0.067 $0.054 Hauling .079 .113 Spreading .101 .015 Sprinkling .015 .013 Rolling .012 .015 Depreciation and repairs .091 .034 Administration .033 .022 Total cost per cubic yard $0.398 $0.266 Aggregate total cost $121,338 $52,814 The average daily output per steam shovel was 950 cu. yds., at a cost of $15 per day worked. Comparing the above with Eastern conditions it appears that the difference in price and quality of coal for power production adds 2 to 3 cents per yard. There is an average of two working UNIT COSTS, RECLAMATION SERVICE 587 days more per month in the West than the East, due to less rainfall, allowing for which makes wages in the West cost 39 per cent, more than in the East. Including higher freight, diffi- culty of making repairs, etc., this class of work costs 25 to 50 per cent, more in the West than in the East, depending on locality and accessibility. The following are some unit prices bid on contract work: CONCRETE. Per cu. yd. Belle Fourche, S. D., dam $6.50 to $7.00 Lower Yellowstone, Mont., canal structures 4.25 to 6.25 Minidoka, Idaho, dam 5.00 to 6.00 Salt River, Ariz., spillway 6.00 Truckee-Carson, Nev., turnouts, foundations 10.00 to 12.00 Umatilla, Ore., dam and canal structures 6.00 to 8.00 Yuma, Cal.-Ariz., core-wall 4.00 EARTH EXCAVATION. COST PER CUBIC YARD. Loose Material. Plowable 2-4 Horses Heavy. Plowable 6-8 Horses. Indurated. Blast- ing and Scrapeis. Belle Fourche, S. D. Borrow pits to ic Grading and embankment *_>. i^ $o 1 6 ^o $o 2^ $o 42 North Platte, Wyo. Main canal . . 1 1 14 40 60 Lateral canals . 18- . ii 4 U . ^5 . 60 Truckee-Carson, Nev. Main canal 2O 2 1 ic TO Lateral canals I 7 . I C $O 12 to. 15 25 .4.C. Uncompahgre, Col. Main canal .11 .14 .16 .25- .28 Hondo N M dam 11 l% .46 Lower Yellowstone, Mont. Main canal 12 14 . 28- . 14 Pavette-Boise Idaho dam T > . 10- . IS 5 88 RECLAMATION SERVICE LOOSE ROCK EXCAVATION. COST PER CUBIC YARD. 2 1O 10 CU. ft. 10 to 15 cu. ft. 15 to 30 cu. ft. Lower Yellowstone, Mont., canal $O . 3O $O CJO Truckee-Carson, Nev., canal JO 2s North Platte, Wyo., canal . . . o w -oo $o. 3S $o. 7? * u -o u *-3^ Payette-Boise, Idaho, canal e r ?C Hondo, N. M., dam JJ ' /O Uncompahgre, Col., canal . . . ? r SOLID ROCK EXCAVATION. COST PER CUBIC YARD. Belle Fourche, South Dakota, canal $i . 05 Klamath, California, canal i . 25 Lower Yellowstone, Montana, main canal and structures 65 Minidoka, Idaho, laterals i . 50 Canal . $o . 90- . 95 North Platte, Wyoming, canal 50- . 80 Payette-Boise, Idaho, canal i . 15- i . 25 Salt River, Arizona, Roosevelt dam i . 50 Truckee-Carson, Nevada, canal 80 Uncompahgre, Colorado, canal 95 Yuma, California- Arizona, Laguna dam i . 30 MISCELLANEOUS. Ce- ment. Gates and Guides. Lum- ber. Pave- ment Head- works. Pud- dling. Rip- rap. Rock- fill. Belle Fourche S. D bbl. $21* pound. $o ex 1000 ft. sq. yd. $2 18 cu. yd. cu. yd. cu. yd. Payette-Boise Idaho 06 $O 3O $1 2S Truckee-Carson, Nev Umatilla Wash. 2-55 .07 45 70 1.50 $2 . OO 300 $1 ^O Yuma, Cal.-Ariz Lower Yellowstone, Mont . . . 2. 7 6 2 8O .... I .00 sO 2 OO 35 North Platte, Neb 2 2O 7c Klamath, Cal Minidoka, Idaho 2 0? oc OO UNIT COSTS, RECLAMATION SERVICE 589 Reinforcing steel used in the canal lining of Uncompahgrc project, Colorado, cost 0.034 cent per pound, 0.016 cent per linear foot of bars, and 0.895 cent P er cubic yard of concrete. Contract prices for pressure stave pipes for Salt River project were : Pressure Head Per Linear in Feet. Foot. 10-20 $5. 13 20-30 5.53 30-40 5-94 40-50. ... 6.34 Additional price for each additional lo-foot increment in pressure up to 200 feet, 53 cents. INDEX PAGE Absorption 20 Amount of, in Reservoirs and Canals 30 Works of Reference 33 Acoustic Current Meter 71 Acre foot 47 Duty of Water per 53 Agra Canal, Iron Aqueduct 286 Kushuk Fall on 265 Scouring Sluices 211 Alcohol Pumping-Engines 541 Alignment of Canals 127 Canals, Obstacles to 131 Ganges Canal : 135 Santa Ana Canal " 143 Turlock Canal 138 Alkali : 34 Causes of 34 Growth of Suitable Plants in 38 Leaching and Mulching of 38 Prevention of 35 Soil, Chemical Treatment of 36 Works of Reference 46 Alkaline Water, Use of 36 Allen, C. A . r 1 7, 346 Altitude, Increase of Rainfall with g American Society of Irrigation Engineers 31 ; Well Works 487 Application of Sewage, Methods of 114 Water, Methods of 321 Works of Reference 352 Aprons to Weirs 183 Aqueducts and Flumes 272 Interstate Canal 284 Iron 276 Agra Canal 286 Bear River Canal, Utah 277 Henares Canal, Spain 278 Masonry 279 Nadrai, over Kali Nadi on Lower Ganges Canal, India 282 591 59 2 INDEX PAGE Aqueducts and Reinforced Concrete 283 Solani River, Ganges Canal, India 136, 279 Arched Masonry Walls 474 Archimedean Screw 512, =u^ Areal Duty of Water 54 Arizona Canal 254 Plan of Headworks 229 Regulator Gates 23^ Weir 1 79 Artesian Water, Storage of 96 Wells . 94 Capacity and Cost of 95, 507 Drilling, Manner of 97 Machinery for t . . . . 98 Process of 100 Examples of 94 Sizes of 96 Sources of 93 Works of Reference 117 Ash Fork Dam 474, 478 Ashlar-Faced Concrete Weir . . . ." 194 Ashti Dam 372 Asphalt Lining of Dams 435 Assiout Weir 122, 457 Associations, Water Users' 569 Assuan Dam 457 Atmospheric Pressure 60 Austin Dam 462 Automatic Drop-shutter 489 Gates 488 Shutters 488 Sluice Gates 221, 224 Wasteway Gate 226 Weir Gates 226, 488, 491 Avalon Dam 383, 384 Babcock, E. S 391 Baker, Ira 507 Baker, M. N 123 Bale, M. Powis 562 Banks of Canals, Side Slopes and Top Widths of 154 Bannister, C. K 348 Bari Doab Canal, Drainage Diversion 268 Rapids 266 Barr, W. M 563 Barrois, J 311 Barrows, H. K 89 INDEX 593 PAGE Bascuie 48g Bazin, M Sg Bear River Weir 180 Canal, Cross-section in Rock 160 Escapes 242 Fall 263 Iron Aqueduct 277 Regulator Gates .... 221, 237 Trap Sluice Gates 221 Valley Dam 416471 Beetaloo Dam 44g, 504 Belle Fourche, Automatic Wasteway Gate 226 Dam 381 Belubula Dam, Australia 476 Beresford, J. S 2g, 33, 299 Betwa Canal, Drainage Diversion 268 Dam 458 Automatic Sluice Gate 489 Bhatgur Dam 444, 49 1 , 496 Bjorling, P. R 563 Borings on Canal Locations 134 Boston Water Works Dam 370 Bouzey Dam 414 Bovey, Henry T 352, 507, 563 Bowlder and Brush Weirs 1 65 Bowman Dam 394 Breast Water-wheels 526 Bresse, M 563 Brush and Bowlder Weirs 165 Buck Scraper 558 Buckley, R. B 33, 41, 46, 48, 57, 263, 31 1, 507 Bucket Water Engines 527 Buford-Trenton Pumping Plant 554 Butler, W. P 116 Buttressed Masonry Walls 474 By-pass Feeder, Umatilla Canal 246 Calloway Canal, Cross-section 155 Distributary Heads 305 Escapes 242 Regulator 232 Weir 168 Canal Alignment 127 Ganges Canal as an Example 135 Obstacles to 132 Santa Ana Canal as an Example 143 Turlock Canal as an Example 138 594 INDEX PAGE Canal Banks, Side Slope and Top Width of 154 Cross-sections, Form of 152 Rock 1 60 Subgrade 155 and Diversion Works: Works of Reference 311 Distributaries 296 Grades for Given Velocities 149 Head, Arrangement of 231 Limiting Velocity in 149 Ibrahimia 122, 457 Lined Cross-section of 156 Locations, Borings on 134 Trial Pits on 1 34 Minidoka 385 Steel-lined 159 Subgrade, Cross-section of 155 Survey, Permanent Marks on 135 System, Parts of 1 25 Velocity in 149, 150 Water, Measurement of 85 Methods of Measurement of 86 Work, Sidehill 133 Works, Maintenance and Supervision of 560 Canals Absorption in 30 Cross-section of 148, 151 Curvature on 134 Deltaic .' . . . 1 23 Dimensions and Cost of some Perennial 123 Efficiency of ' 299 Inspection of v 562 Inundation 120 Limiting Velocity on 149 Navigation and Irrigation 119 Perennial . ". 123 Prevention of Sedimentation in 42 and Reservoirs, Amount of Absorption in 30 Slope and Cross-section of 148, 150 Sub- 107 Survey of 1 28 Works of Reference 311 Canvas Dam 333 Carlsbad Project 3 8 4 Carmel Dam, Wasteway 487 Carpenter, Prof. L. G 32, 52, 57, 80, 85, 90 Casing, Stove-pipe, for Drilled Wells 101 Castlewood Dam 394 Cautley, Col. Sir Proby T 311 INDEX 595 Cavour Canal, Inverted Siphon under River Sesia 292 Cement 430 Wash 435 Centrifugal Pumps 511, 546 Pumping Plants 550 Chamberlin, T. C 1 16 Chanoine Movable Shutters 221 Check-Levees, Flooding by 325 Checks, Ditch and Furrow 333 Chemical and Physical Properties of Water 58 Treatment of Alkali Soil 36 Chezy's Formula of Flow 62, 340 Chittenden, Lieut. H. M 223, 311 Church, Irving P 90, 507 Chutes of Wood ... 264 Cippoletti's Formula of Flow over Trapezoidal Weirs 79, 83 Clerke, Sadasewjee and Jacob . 507 Coefficient of Friction in Masonry 403 Cohoes Iron Rollerway Weir 196 Cold Spring Dam 369 Colorado River Weir at Yuma 175,214 Wooden Pipe 346 Conconully Dam 504 Concrete 428 Pipes . 349 Reinfoiced, Weir 200 Weir, Ashlar Facing 194 Construction, Cost of 506 Details of 431 Contour Topographic Survey 130 Contract Prices, Reclamation Service 585 Contracts and Specifications 440 Core Walls, Masonry 367, 369 Foundation of 366 Corbett Weir 201 Cost of Artesian Well Drilling 95 Construction 506, 585 Irrigation 4, 5 and Dimensions of Perennial Canals 123 Pumping 555 Storage Reservoir 360 Unit on Reclamation Works 584 Craig, James .... 21 Cramer, C. B 33 Crib Dams 392 Foundations for Masonry Weirs 192 and Pile Foundations for Masonry Weirs 191 INDEX Crib and Rock Weirs 1 79 Weirs, Construction of 179 Cribs, Gathering, for Water 107 Cribwork, Underground 106 Crops, Duty of Water for ^2 Crossings, Level 270 Siphon 292 Cross River Dam 434 Cross-section of Bear River Canal in Rock 161 Calloway Canal 155 Canals J 48, i S l Canals, Form of 152 Canals in Rock 1 60 Canal with Subgrade 155 Lined Canal 156 Santa Ana Canal in Rock 146 Turlock Canal in Rock 161 Umatilla Canal 161 Various Canals 152 Croton Dam, New, at Cornell's, N. V 426, 433, 447 Weir 192 Crushing, Stability against, in Masonry Dams 404 Cultivation by Irrigation, Theory of 319 Culverts 289, 294 Current Meters : 72 Acoustic 73 Haskell 72 Price : 73 Rating the 76 Use of : .... 75 Curved Dam, Design of 418 Masonry Dam 4*5 Curvature on Canals 134 Cusec 47 Cuts, Drainagee 268 Dam, Ashti 37 2 Ash Fork 474, 47$ Assuan 457 Austin 462 Avalon 383 Bear Valley - .416, 47 1 Beetaloo 449> 54 Belle Fourche 380 Belubula 476 Betwa 458 Bhatgur 444, 49 r > 49 6 INDEX 597 PAGE Boston Water Works 370 Bouzey 414 Bowman 394 Canvas 333 Carmel, Wasteway of 487 Castlewood 394 Cold Spring 369 Combined Earth and Hydraulic-fill 378 Conconully 504 Cross River 434 Croton, New, at Cornell's 426, 433 Design of Curved 418 Earth with Masonry Retaining Wall 382 East Park 477 Ekruk .382 Folsom 4< 2, 496 Furens 442 Geelong 428 Gran Cheurfas 443 Habra 414 Hydraulic-fill 377 Kabra " 382 Kalegh . . . 377 Kingman 438 La Grange 4 La Mesa 378 Lake Fife - 474 Loose Rock with Masonry Retaining Walls 394 Lower Otay 39 1 Meer Allum 474 Minidoka 385 Monument Creek 371 New Croton, Cornell's, N. Y 426, 433, 447 Olive Bridge 426, 434 Periar 448, 486, 493 Profile of 410 Profile Type for Masonry 409, 410 Puentes 412 Remscheid 450 Roosevelt 466, 486, 495, 506 San Fernando 437 San Leandro 377 San Mateo 450, 503 Sante Fe 372, 487 Shoshone 417, 470 Sodom 425, 432 Specifications 573 INDEX PAGE Dam, Spier Falls , '. 430, 464 Steel 478 Sweetwater 416, 452, 486, 499 Tansa 444 Titicus 369 Tyler . 37 8 Upper Otay 472 Vyrnwy 456, 502 Wachusett 500 Walnut Grove 389 Zola 416, 471 Dams, Asphalt Lining and Cement Wash 435 Buttressed and Arched 474 Cement 430 Classes of N 360 Concrete 428 Construction in Flowing Streams 438 Crib 392 Curved Masonry 415 Design of Curved Masonry 417 Overfall 421 Details of Construction of Masonry 431 Dimensions of Earth 364 Diversion 208 Earth 363 Masonry Core Walls in 369 Material of ' . 376 Puddle Trenches in 371 Walls and Faces of 370 Slope and Paving of 380 Earth and Loose-rock 383 Examples of Masonry 440 Failure, Causes of 363, 41 1 and Faulty Design of 396 Foundations of Masonry 424 Earth 365 Height of 410 Inlet ; for Drainage 266 Limiting Pressures in Masonry 406 Loose-rock 387 Masonry, Material of 426 Molesworth's Profile Type of 409 Overfall 420 Puddle Walls and Faces of Earth 370 Rock-filled 386 Steel-core 391 Rubble Masonry 430 INDEX 599 PAGE Dams, Springs in Foundations of 366 Stability against Crushing 404 of Gravity 400 of, against Overturning 406 against Sliding 402 Temperature Changes 415 of, against Upward Water-pressure 411 Steel 334,478 Steel-core, Rock-filled 391 Submerged 437 Theory of Masonry 399 Top Width of 410 Wegmann's Profile Type of 410 Wide-crested 420 D'Arcy's Formula for Flow 62, 341 Darton, N. H 92, 117 Davis, A. P 46 Deakin, Alfred 46, 57 Delocre, M 417 Del Norte Canal Regulator Gates 291 Deltaic Canals 123 Derout Regulator 122 Desert-land Grants 131 Deny, J. D 311 Diamond-Drilling * 357 Dickens, Col. C. H., Formula for Runoff 16 Discharge over Weirs, Table of 80 of Pipes 338 of Streams, and Table of 18, 65 Flood 17 Mean 21 in Seasons of Minimum Rainfall 20 of Waste Weirs 482 Western Rivers 20 Disposal of Sewage 107 Distributaries, Capacities of 302 Design of 297 Diagram Illustrating 297, 298 Dimensions of 302 Efficiency of 299 Huntley Canal 298 Location of 296 Object and Types of 296 Distributary Channels in Earth 303 Heads, Galloway Canal, Cal 305 of Masonry 310 of Wood 304 600 INDEX Distributary Pipes of Iron, Steel, or Wood v 336 Capacities of 286 Distribution of Rainfall in Detail & Water, Rotation in 55 Ditch Checks 333 Diversion and Canal Works, Works of Reference 311 Dams 2o Line 126 Weirs 164 Works 126 Divisors, Water 89 Drainage 30 Crossing at Level 270 Cuts 268 Diversion, Bari Doab Canal, India 268 Betwa Canal, India 268 Inlet Dams for 268 Works 266 Works of Referencee 46 Dredges 560 Drilling Artesian Wells 35 7 Diamond Machines for 98 Manner of 97 Process of 100 Du Bois, A. J ' 90, 312, 3^2, 508, 563 Duty of Sewage 112 Water 47 per Acre-foot 53 for Crops, Various 52 Linear and Areal 54 Measurement of 50 Reference Works on 57 per Second-foot 51 Table of 51 Units of Measure of 47 Works of Reference 57 Dyas, Col. J. H 256 Dyer, C. W. D 90 Earth Dam, Ashti 372 Boston Water Works 370 Cold Spring, Oregon 369 Ekruk 382 New Croton, at Cornell's 368 Santa Fe, N. M 37 2 Titicus, N. Y 3^ Dams, Construction of 374 INDEX 60 1 PAGE Earth Dams, Cost of 507, 585 Dimensions of 364 or Embankments 363 Puddling 374 Failures of . . 363, 396 Foundations of 365 Masonry Core Walls in 309 Trenches in 372 with Masonry Retaining Wall 382 Materials of 3/6 Puddle Walls and Faces 370 Distributary Channels in 303 Evaporation from 27 Embankment, Homogeneous 367, 372 Slope and Paving of 380 and Loose-Rock Dams 383 Failures and Faulty Design of 396 Waters, Sources of 91 Earthwork, Cost of . . 507, 585 Shrinkage of 159 East Park Dam .... 477 Echeverry, B. A . . . . 1 56, 3 1 1 Efficiency of a Canal 2 Egypt, Area Irrigated in 122 Canals 121 Ekruk Dam .382 Electric Current Meters 72 Elevators, Mechanical Water 510, 556 Embankment, Construction of 376 Cost of . 507, 585 Earth Dams or 363 Homogeneous 367, 372 Hydraulic Fill 377 Material 376 with Masonry Retaining Wall 382 of Sand 377 Slope and Paving of 380 Energy, Equivalent Units of 545, 546 Engineering News 117 Engines, Alcohol Pumping 542 Gasoline Pumping 513, 542 Hot-air Pumping 510, 542 Pumping 551 Steam Pumping 511 W'ater Pressure 537 Fscapes . ... 239 Bear River Canal, Utah 242 602 INDEX Escapes, Galloway Canal, Cal 242 Goulburn Canal, Australia 244 Heads, Design of 242 Highline Canal, Col 242 Location and Characteristics of 240 Qushesha 122 Turlock Canal, Cal 242 Eucalyptus as Preventive of Fevers 45 Evans, John , 33 Evaporating-pan 24 Evaporation, Amount of 25 Effect of, on Water Storage 31 from Earth 27 Measurement of 23 Phenomena 23 from Snow and Ice 25 Table of Depth of 26 Works of Reference 33 Evaporometer, Piche 25 Excavating Machines 559 Excavation, Cost of Earth 585 Fall, Agra Canal, India 286 Bear River Canal, Utah 161 Interstate Canal 262 Lower Yellowstone Canal 264 Notched Crest ' 260 Turlock Canal, California 270 Uncompahgre Canal, Notched 259 Fall of Wood, Simple Vertical 263 Wooden, with Water-cushion 263 Falls of Masonry 264 and Rapids 255 Retarding Velocity of Approach to, by contracting Channel above 257 by Flashboards 256 by Gratings 257 Falling Sluice Gates 221, 224 Water, Power in 524 Scouring Effect of 183 Fanning, J. T 16, 21, 89, 352, 403, 507, 544, 563 Farms, Sewage 114 Fernow, B. E 27 Fay Lake Reservoir Outlet Gates 504 Fayoum 122 Fertilizing Effects of Sediment 44 Sewage no Fevers . 1 1 * INDEX 603 PAGE Fevers, Malarial 44 Finkle, F. C 352 Fitzgerald, Desmond 17, 21, 33 Flashboard or Open-frame Weirs 168 Regulators of Wood 232 Flashboards on Fall Crest to Retard 2>6 Flinn, A. D 90 Flood Discharges of Streams 17 Flooding by Check-levees 325 and Furrow Irrigation Combined 328 of Sidehill Meadows 324 by Squares 326 by Terraces 327 Flow, Available Annual, of Streams 21 Chezy's Formula of 62 Kutters Formula of 62 and Measurement of Water in Open Channels, Works of Reference on . . 89 in Open Channels, Formulas of 61 of Water in Pipes 338 Formulas of 339 Measurement of 350 Tables of 340 Units of Measure of 47 Velocities of 65 Flume, Highline Canal, Col 274 over Mill Creek, Santa Ana Canal 143 San Diego, Cal 274 Santa Ana 275 Stave and Binder 275 Trestles 276 Flumes and Aqueducts 272 Flumes, Construction of t 274 Rating 88 Reinforced Concrete 283 Sidehill 274 Stave and Binder 275 Flynn, P. J 57. 9, 256,311,352 " Flow of Water," by 62, 340 Folsom Canal, Hydraulic Lifting Gate 239 Dam 462, 496 Foote, A. D 57,87 Foote's Water Meter 87 Formula, Chezy's 62 Francis' 78 of Flow of Water in Open Channels 62 Pipes 339 Kutter's , 62, 339 604 INDEX PAGE Formula of Maximum Runoff 16 Fortier, Samuel 33, 52, 57, 352 Foundations of Dams, Exploring for Bed-rock 357 Springs in 366 Earth Dams 365 Masonry Core and Puddle Wall 366 Dams 424 Preparing 424 France, Area irrigated in 2 Francis' Formulas of Flow over Weirs 78 Francis, J. B 78, 405, 483, 507 French Movable Weirs of Iron 177 Scraper 558 Fteley, A 57 Furens Dam 44 2 Furrow Checks 333 and Flooding combined 328 Irrigation 327 Furrows, Irrigation by Small 320 Ganges Canal as an Example of Canal Alignment 135 Headworks and Plan of 228 Kali Nadi Aqueduct 282 Ranipur Superpassage 135, 286 Regulator Gates 234 Rutmoo Level Crossing 136, 271 Solani Aqueduct 136, 279 Garland Canal Turnouts - . . 3 1 1 Gasoline Engines 513, 54 2 Gas Producer for Pumping ... 545 Gate, Automatic Wasteway 225 Balanced Sluice 495 Chamber 49 8 Regulator Raised by Screw 235 Windlass 234 Towers 49 8 Examples of 500 Gates, Automatic Weir 223, 488, 491 Electrically Operated 5<> Falling Sluice 221 Hydraulic Lifting 239 Inclined Falling 236 Regulator 234, 239 Sand 250 Taintor Wasteway , 246 Gathering-Cribs for Water 106 Gauge Heights, Weir 8 INDEX 605 PAGE Gauging Car 74 Rainfall 1 1 Stations 74 Stations, Rating the 75 Stream Velocities 70 Gearing, Regulator Gates raised by 235 Geelong Dam 428 Geology of Reservoir Site 359 Gila River Valley, Precipitation in 8 Glassford, Lieutenant W. A 21 Goulburn Canal, Escapes 244 Regulator Gates 236 Iron and Masonry Drop-gate Weir 197 Gould, E. Sherman 352, 507 Grade for given Velocities on Canals 149 Grading Machines 559 Gran Cheurfas Dam 443 Grand River Canal, Big Drop 264 Granite Reef Regulator 229 Sluice Gate 219 Sluiceway 21^ Weir 202 Gratings to Retard Velocity of Approach to Falls . 2^7 Gravity Dams, Stability of 400 and Lift Irrigation 1 18 Greaves, Charles 28, 33 Greeley, Gen. A. W 21 Green, J. S 90 Griffiths, J. A 518, 563 Ground, Preparation for Irrigation 322 Water, Motion of 91 Habra Dam 414 Hall, Wm. Ham 57, u 7, 3", 352. 57 Hamlin, Homer 117 Haskell Current Meter 72 Hay, Robert 117 Hazen, Allen 92 Heads, Masonry Lateral 310 Wooden Lateral 304 Headworks of Arizona Canal, Plan of 215 Arrangement of 231 Character of 163 Ganges Canal, India . . 229 Location of 162 Health, Effects of Sewage on 1 1 1 Irrigation on 44 606 INDEX Henares Canal Iron Aqueduct, Spain 278 Weir, Spain 194 Herschel, Clemens 311, 350 Highline Canal, Bench Flume 274 Escapes 242 Sand Gate 250 Hilgard, E. W 37, 46, 377 Hill, Robert T 117 Hobart, E. F 507 Hollister, J. B 90 Holyoke Weir 208 Horton, R. E 80, 90 Hot-air Pumping Engines 5 10, 541 Hoyt, J. C ... 89 Hughes, Samuel 563 Humphreys and Abbott 70 Hurdy-gurdy 526 Hydraulic-fill Embankment or Earth Dam 377, 378 Hydraulic Lifting Regulator Gate, Folsom Canal, Cal 239 Motors 526 Rams .527, 539 Ibrahimia Canal, Egypt : ... 122, 457 Ice, Evaporation from 25 Stream Measurement under 89 Inch, Miner's 48, 87 Statute or Module : 86 India, Precipitation in 7,11 Area Irrigated in 2 Indian Type Weirs 1 70 Inlet Dams for Drainage 268 Inspection of Irrigation Works 562 Inundation Canals 1 20 Interstate Canal Falls 262 Flume 284 Siphon 295 Sluiceway 245 Inverted Siphons 289 Hurron Torrent, Sirhind Canal 293 Kao Torrent, Soane Canal 291 Sesia River, Cavour Canal 292 of Masonry 291 Investment, Value of Irrigation as an 3 Iron Aqueducts 276 Agra Canal 286 Bear River Canal . . 277 Henares Canal 276 INDEX 607 PAGE Iron Aqueducts, and Steel Pipes 343 Weirs 196 Movable 176 Rollerway 196 Irrigated Area in United States 6 Irrigation, Alkali, Effects of on 34 Cost and Returns of 4 Cultivation by 319 Effect on Health of Sewage in Engineers, American Society of 311 Extent of 2 by Flooding by Checks 325 and Furrows combined 328 by Furrows 327 Gravity i ; 8 Harmful Effects of 44 Incidental Value 4 Lift 1 18, 509 Malarial Effects of 44 of Meadows by Flooding 32 [ Meaning of i and Navigation Canals 1 19 Period 54 Quantity of Water per 56 Preparation of Ground for 322 Pumping or Lift 509 Relation of Rainfall to 7 Sewage 1 09 by Small Furrows 330 Subsurface 334 by Terraces 327 Theory of Cultivation by 319 Tools .. .---557 Value as an Investment 3 Windmills for ^23 Works, Classes of 1 18 Control of 2 Sources of Impairment of 561 Irrigating Machines, Value of Windmills as 523 Period, Quantity per 53 Italy, Area Irrigated in 2 Precipitation in 7 Jackson, Louis D' A 117 Jacobs, Arthur 508 Jaffa, M. E 38, 46 Kabra Dam 382 608 INDEX Kalegh Sand Embankment, India 377 King, Prof. F. H 57, 352 Kingman Submerged Dam 438 Krantz, J. B 400, 416, 508 Kutter's Formula of Flow 62, 340 Tables for Use with 63 La Grange Dam 460 Laguna Weir, Colorado River 1 75, 2 14 La Mesa Dam 378 Lake Fife Dam 474 McMillan .384 Land Grants, Desert 131 Percentage of Waste 55 and Water Supply, Relation between 126 to Reservoir Site 353 Landreth, O. H 5 2 4 Laterals, Capacities of 302 Dimensions of 302 Masonry Heads to 310 Wooden Heads to 304 Latha 5 X 5 Law, Reclamation 564 Leaching of Alkali Soil 3 8 Leasburg Regulator Gates 236 Sand Gates 253 Weir ' 19 Level Crossings of Drainage 268 Rutmoo ... 136 Turlock Canal 270 Lever, Wooden Regulator Gate raised by 234 Levinge, H. C 3 11 Lift and Gravity Irrigation 1 18 Irrigation or Pumping 59 Weir, Rolling 1 77 Limiting Pressures in Masonry Dams 46 Linear Duty of Water 54 Location and Characteristics of Escapes 240 of Distributaries 296 of Headworks IO2 Survey, and Alignment of Canals 127, 128 Loose-rock and Earth Dams 3 8 3 Failures and Faulty Design of 396 Dams 3 8 7 Loughridge, R. H 33 1 Lower Ganges Canal, Nadrai Aqueduct, India 282 Lower Otay Dam 39 1 INDEX 609 PAGE Lower Yellowstone Canal Falls 264 Level Crossing 270 Siphon 294 Turnouts 310 Wasteway 245 Weir 182 McCall's Ferry Dam 428, 433, 434 McCulloh, Walter . . . 508 McMasters, John B 508 McMillan Lake .384 Machines, Drilling 98 Excavating . 559 Pumping, Choice of 512 Mahan, F. A . . . 563 Mahanuddy Sluice Shutters 223 Maintenance of Canal Works 560 Malarial Effects of Irrigation 44 Manning, Robert 117 Masonry Aqueducts 279 Coefficient of Friction in 403 Cores . .367, 369 Foundation of 366 Dams of Concrete 428 Cost of Construction of 507 of Cement 430 Construction in Flowing Streams 430 Curved 415, 418 Details of Construction 431 Examples of 440 Failure and Causes of 411 Foundations of 424 Limiting Pressures in 406 Material of 426 Overfall Type 420 Profile Type for 409, 410 of Rubble 430 Stability of 400 Crushing 404 Overturning 406 against Sliding 402 Temperature Changes .... 415 Upward Water Pressure 411 Theory of 399, 409 Falls 264 Inverted Siphons 289 Lateral Heads 310 6lO INDEX PAGE Masonry Rapids 266 Retaining Wall, Embankment with 382 Turnouts 310 Walls, Buttressed and Arched 474 Weir of Rubble 195 Weirs 188 Founded on Piles 190 Piles and Cribs 191 Wells 192 Open Indian Type 170 Maxwell, J. P 33 Mead, Elwood 57 Meadows, Sidehill Flooding of 324 Means, Thomas H 36 Measure, Unit of, for Water Duty and Flow 47 Measurement of Canal Water 85 Methods of 86 Evaporation 23 and Flow of Water, Works of Reference 89 Stream under Ice 89 Water Duty 50 in Pipes 350 Measures of Water, Table of Units of 48 Measuring Apparatus, Requisites of a 85 Stream Velocities 70 Weirs 77 Rectangular 77 Medley, Lt-Col. J. G 311 Meer Allum Dam 474 Merriman, Mansfield 508 Meters, Current 72 Rating the 76 Use of 75 Foote's Water 87 Venturi Water 350 Miner's Inch 48, 87 Minidoka Project and Dam 385 Regulator Gates 236 Module, or Statute Inch 86 or Water-Measuring Apparatus 85 Molesworth, Guilford L 409 Profile Type for Masonry Dam 409 Moncrieff, C. C. S 311 Monument Creek Dam 371 Mot 5 I 5 Motion of Ground Water 91 of Water . 60 INDEX 6ll Motive Power for Pumps 510 Motors, Water 526 Movable Weirs 1 76 Mulching Alkali Soil 38 Mullin, Lt.-Gen. J 90, 3 1 1 Murphy, E. C . .85,90,523,563 Murray, Stuart 312 Nadrai Aqueduct, Lower Ganges Canal, India 282 Navigation and Irrigation Canals 1 19 Nettleton, E. S 117 Newark Weir 206 Newbrough, W 312 New Croton Dam, Cornell's, N. Y 426, 433, 447 Newell, F. H ..15, 22,33,57,90, 117 Nile Inundations 1 20 Nilometer 74 Noria 515 Norwich Water Power Go's. Weir 191 Notched Fall Crest 260 Ogee-shaped Weirs 185, 196 Okanogan Canal Rapids 266 Olive Bridge Dam 426, 434 Orme, Dr. S. H 45, 1 1 7 Otay Dam, Lower 39 1 Upper. . . 472 Outlet Gate, Roosevelt Dam 506 Vertical Lift 496 Sluices 496 Examples of 500 Overfall Dams 420 Overshot Water Wheel 5 26, 531 Overturning, Stability of Dams against 406 Paecottah 515 Parker Bear-trap Gate 223 Paving of Embankment 380 Pecos Dam 383, 384 Valley, Precipitation in 9 Pelletreau, M 417 Pelton Water-wheel 526, 534 Pequannock Weir at Newark 206 Percentage of Waste Land .... 55 Percolation, Amount of 28 Prevention of 30 6l2 INDEX PAGE Perennial Canals 122 Dimensions and Cost of 123 Periar Dam 448, 486, 493 Permanent Marks on Canal Surveys 133 Persian Wheel 514 Pruenix, Precipitation at 12 Physical and Chemical Properties of Water 58 Piche Evaporometer 25 Pile Foundations for Masonry Weirs 190 Weirs 166 Pipe Irrigation, Works of Reference 352 Pipes, Concrete 349 Construction of Wooden 347 Flow of Water in 338 Formulas of Flow in 339 Iron and Steel 343 Main and Distributing 336 Measurement of Water in 350 Reinforced Concrete 349 Steel 343 Sub-irrigation 336 Tables of Flow in 340 Wooden Stave 346 Works of Reference on 352 Plant Growth, Relation of, to Soil Texture 315 Water . . . 313 Plants Suitable for Growth in Alkaline Soil 38 Poncelet Water-wheel 528 Powell, J. W 117 Power, Cost of, for Pumping 555 Equivalent Units of 547 of Falling Water 524 -Pumped Wells 103 Precipitation by River Basins, Table of 10 States, Table of '. 12 Works of Reference on 21 Pressure, Atmospheric 60 Limiting, in Masonry Dams 406 of Water 59 Price Current Meter 73 Producer Gas Power 545 Profile of Dam 410 Type for Masonry Dam 409, 410 Public Lands, Right of W 7 ay on 131 Puddle Trench 371 Walls 367, 370 and Faces 370 INDEX 613 PAGE Puddle Walls, Foundations of 366 Puentes Dam ... 412 Pulsometers 556 Pumping, Cost of 555 Engines . . . 551 Alcohol 541 Gasoline 541 Hot-air 541 Steam 552 or Lift Irrigation 509 Machinery, Reference Works 562 Machines, Choice of 512 Plants, Examples of Centrifugal 550 Steam 552 Willixton, N. D 554 by Steam-power 543 Pumps, Animal-power 514 Centrifugal 511, 546 Chain 512 Direct-acting 512 Fly-wheel 512 Force 510 Gas 510 Gasoline 510 Hot-air 510 Hydro-electric 511 Lift 510 Motive Force for 510 Rotary 510, 546 Steam 511 Water-power 510 Wind-power 515 Queshesha Escape 122 Rafter, Geo. W 117 Rainfall 7 Discharge of Streams in Seasons of Minimum 20 Distribution in Detail 8 Gauging i r Great 9 Increase of, with Altitude 8 Relation of, to Irrigation 7 Runoff 15 on River Basins 1 1 Statistics, General 7,10 by States . 1 1 614 INDEX PAGE Rainfall, Works of Reference on 21 Rams, Hydraulic 527, 539 Ranipur Superpassage . . . 135, 286 Rapids, Bari Doab Canal, India 266 and Falls 255 Masonry 266 Okanogan 266 Wooden 264 Rating Current Meter 76 Flumes 88 Gauging Station 76 Reclamation Law 564 Scope of 567 Service 312, 508 Lateral Heads 308 Reinforced Concrete Flumes 283 Specifications of 573 Unit Cost on 584 Wasteways 244 Rectangular Measuring Weir 77 Conditions of Using the 79 Pile Weirs 7 166 Reference Works: Alkali, Drainage, and Sedimentation 46 Application of Water and Pipe Irrigation 352 Artesian Wells 117 Diversion and Canal Works 311 Duty of Water 57 Evaporation, Absorption, and Seepage 33 Flow and Measurement of Water in Open Channels 89 Precipitation, Runoff, and Stream-flow 21 Pumping Machinery 562 Sewage Irrigation 117 Storage Works 507 Subsurface Water Sources 117 Regimen of Western Rivers 20 Regulator Gates, Arizona Canal , 232 Bear River Canal, Utah 242 Del Norte Canal, Col 291 Folsom Canal, Hydraulic Lifting 239 Ganges Canal, India 234 Goulburn Canal, Australia 244 Granite Reef 229 Hydraulic Lifting 239 Inclined, Falling 244 Leasburg 236 Lifted by Travelling Winch 235 Minidoka Canal 236 INDEX 615 PAGE Regulator Gates, Raised by Gearing or Screw 235 Rolling, Idaho Canal 236 Sliding, Idaho Canal 236 Soane Canal, India 235 of Wood lifted by Lever 234 Windlass 234 Regulators, Galloway Canal, Cal 232 Classification of 230 Form of .230 Relation of Weirs to 227 Wooden Flashboard 232 Reid, H. I .117 Reinold, E. K - 49 1 Reinforced-Concrete Canal Lining 158 Culverts 294 Flumes and Trestles 283 Pipes 347 Siphon 294 Weir 200 Remscheid Dam 45 Reservoir Site, Character of 353 Geology of 359 Relation of, to Land and Water Supply 354 Topography and Survey of 355 Reservoirs and Canals, Amount of Absorption in 30 Cost and Dimensions of some Storage 360 Prevention of Sedimentation in 42 Retaining Wall of Masonry, Embankment with 382 to Loose-rock Dam . 394 Retarding Velocity of Approach by Contracting Channel above Fall 257 Flashboards on Fall Crest 256 Gratings on Fall Crest 257 Returns of Irrigation 4 Right of Way on Public Lands 131, 312 Rio Grande, Precipitation on 9 River Basins, Precipitation on 1 1 Training Works 209 Rivers, Western, Discharge of 21 Regimen of 20 Rock and Crib Weirs 1 79 Cross-section of Canals 160 Excavation, Cost of 588 Foundations, Exploring for 357 Rock-filled Dams 386 and Crib Weir 1 79 Steel-core Dam 391 Rollerway and Ogee-shaped Weirs 1 85 6l6 INDEX PAGE Rollerway Weir of Iron 196 Rolling Lift- Weir 177 Ronna, A 312, 508, 563 Roosevelt Dam 466, 486, 495 Outlet Gates 506 Specifications of 573 Rotation in Water Distribution 55 Rotary Pumps '. 546 Rubble Masonry 430 Weir 195 Runoff 14 Amount of, and Tables of 17, 1 8 Examples of 21 Formulas for Maximum 16 of Streams, Table of 18 Relations to Rainfall 15 Variability of 14 Works of Reference 21 Russell, T 25 Rutmoo, Level Crossing 1 3&> 2 7 Ryves. Col., Formula for Runoff 16 Sacremento Valley, Precipitation in 9 Sakia 515 Salt Bush, Australia 38 Salt River, Rainfall and Flood Height of 8 Salt River Valley Project 468 San Diego Flume 274 San Fernando Dam 437 San Joaquin Valley, Precipitation in 9 San Leandro Dam 377 San Mateo Dam 429, 450, 502 Sand, Embankments of 377 Gates 250 Highline Canal 251 Leasburg 253 Santa Ana Canal 252 Santa Ana Canal, Alignment 143 lined Channel 157 Flume 276 Sand Gates 252 Tunnels , 158 Santa Fe Earth Dam 372, 487 Schuyler, J. D . : 435, 504, 508 Scott, John H 312 Scouring Effect of Falling Water 183 Sluices . .211 INDEX 6 1 7 PAGE Scouring Sluices Agra Canal, India, 212 Examples of 212 Monte Vista Canal, Col 212 Scraper, Buck . 558 Scrapers -557 Screw Regulator, Gate raised by 235 Second-foot 47 Duty of Water per 51 Sediment, Amount of 41 Fertilizing Effects of 44 Sedimentation, Prevention of, in Reservoirs and Canals 42 Reference Works on 46 Seepage Water 31 Works of Reference 33 Service Period 50 Quantity of Water per 53 Sesia Siphon on Cavour Canal, Italy 292 Sewage Application 114 Disposal 107 Duty of 112 Fertilizing Effects of 1 1 o Health, Effect on 1 1 1 Irrigation 100 Laying out, Farm 114 Works of Reference 117 Shrinkage of Earthwork 1 59 Shoshone Dam 417, 470 Shutters, Automatic Weir 488 Chanione Movable 221 Side Slopes of Canal Banks 154 Sidehill Canal Work 133 Turlock Canal 1 40 Sidehill Flooding of Meadows 324 Flumes 274 Sidhnai Weir 174 Silt 40 Amount of 41 Character of . 40 Siphon Aqueduct on Soane Canal under Kao Torrent 291 Crossing, Interstate Canal 295 under Hurron Torrent on Sirhind Canal, India 293 Inverted, Sesia River, on Cavour Canal, Italy 292 Siphons 289 Inverted 289 Masonry, Inverted 29 1 Reinforced Concrete 294 Wood, Inverted 291 6l8 INDEX PAGE Sirhind Canal, Siphon under Hurron Torrent 293 Slichter, C. S 33, 92, 117 Sliding, Stability against, in Masonry Dams 402 Slope of Canals 148 Canal Sides 154 Embankment 380 Excessive 255 Sluice Gates, Automatic 221, 226 Balanced 493 Bear Trap Movable 221 Falling 221 Granite Reef Weir 219 Laguna Weir , 217 Shutters, Chanoine Movable ' 221 Mahanuddy Automatic 223 Sluiceways 211 Interstate Canal 246 Laguna 214 Sluices, Outlet 49 6 Examples of 500 Scouring ...211 Snow, Evaporation from 25 Soane Automatic Sluice Gates 224, 488 Canal, Regulator Gates 235 Canal, Siphon-Aqueduct under Kao Torrent 291 Weir i7 2 Sodom Dam .' 425, 43 2 Soil, Depth of Water required to Soak 52 Texture, Relation of, to Plant Growth .313 Solani Aqueduct, Ganges Canal, India 136, 279 Sources of Earth Waters 9 1 Springs and Artesian Wells 93 Supply -119 Specifications and Contracts 44 of Roosevelt Dam, Reclamation Service 573 Spier Falls Dam 43> 464 Spillway to East Park Dam ... 477 Spillways 239 Spon, Ernest ! IJ 7 Springs and Artesian Wells 93 in Foundations of Dams 3^6 Sources of 93 Squares, Flooding by 3 2 6 Stanton, R. B 388, 43 6 > 5 8 State Desert Land Grants I3 1 Statistics of Rainfall 7, 10, 1 1, 12, 13 Statute Inch or Module 86 INDEX 619 PAGE Stave and Binder Flume 275 Pipes of Wood 346 Steam Power, Pumping by 543 Pumping Engines 543 Plants 552 Steel Core Rock-fill Dam 391 Dams 334, 478 and Iron Pipes 343 Lined Canal 159 Stewart, Henry 312 Stoney's Balanced Sluice-gate 493 Storage of Artesian Water 96 Reservoir, Cost and Dimensions of 360 of Water, Effect of Evaporation on 28 Works, Classes of 353 Works of Reference on 507 Storms, Suddenness of Great 1 1 Stream Flow, Works of Reference 21 Measurement under Ice 89 Velocities, Measuring or Gauging 70 Streams, Available Annual Flow of 21 Construction of Dams in Flowing 438 Discharge of r 7, 70 Flood Discharge of 17 Mean Discharge of 21 Table of Discharge and Runoff of 18 Subcanals 107 Subgrade to Canal Cross-section 155 Subirrigation Pipes 336 Submerged Dams 437 Subsupply Tunnels 105 Subsurface Irrigation 334 Water Sources 107 Subterranean Water Tunnel and Wells 105 Suddenness of Great Storms 1 1 Superpassage 284 on Ganges Canal over Ranipur Torrent 135, 286 of Iron, Agra Canal, India 286 Supervision of Canal Works 560 Supply, Sources of 119 Supplying-Capacity of Wells 102 Survey of Canals ^128 Contour, Topographic '. 130 Linear or Trial line 128 Method of Canal 1 28 Permanent Marks on 134 and Topography of Reservoir Site 355 620 INDEX PAGE Sweetwater Dam 416, 452, 486, 500 Taintor Wasteway 246 Tansa Dam 444 Tatils, or Rotation in Water Distribution 55 Terraces, Flooding by 327 Theory of Masonry Dams 399 Tieton Canal Lining 158 Flumes 283 Titicus Dam 369 Tools, Irrigation 557 Topographic Survey, Contour 130 Topography and Survey of Reservoir Site 355 Top Width of Canal Banks 154 Towers, Gate 498 Training- Works for Rivers 209 Trapezoidal Weirs 79 Tables of Flow over 83 Trautwine, J. C 90 Trench, Puddle, in Earth Dams 371 Trestles, Flume 276 Trial-line Survey 128 Trial Pits on Canal Locations 134 Trowbridge, W. P 563 Truckee-Carson Canal, Lining 157 Tunnels on 148 Tunneling for Water 105 Tunnels for Sub-supply : 105 Santa Ana Canal 146 Truckee-Carson Canal 148 Turlock Canal 142 Underground .- 105 Turbine Water-wheels 532 Turlock Canal as an Example of Canal Alignment 138 Level Crossings 270 Sidehill Works 140 Tunnels 142 Turneaure, F. E . 508, 563 Turnouts, of Masonry 310 Wood - 34 Tyler Dam, Texas 37 8 Tympanum 515 Umatille By-pass ." 246 Canal Section 161 Project, Cold Spring Dam 369 Uncompahgre Canal Fall 259 Underflow 93 INDEX 621 PAGE Underground Cribwork or Tunnels 106 Undershot Water-wheels 526, 527 Undersluices 495 Examples of 496 United States, Area irrigated in 6 Units of Measures for Water Duty and Flow 47 Power, Equivalents of 547 Upper Otay Dam 472 Valve- chambers 498 Examples of . 500 Variability of Runoff 14 Velocity of Approach, Retarding by Contracting Channel above Fall 257 Flashboards on Fall Crest 256 Gratings on Crest of Fall 257 Limiting, on Canals 149 Velocities on Canals for given Grades 149 Examples of 150 of Flow in Canals 65, 148 Pipes . . .338 Formula for 61 Stream, Measuring or Gauging 70 Surface and Mean 70 Venturi Water Meter 350 Vernon-Harcourt, T. F 312 Vertical Fall of Wood 263 Vir Weir 195 Vischer, Huber 418, 508 Vyrnwy Dam 456, 502 Wachusett Dam 500 Wagoner, Luther 418, 508 Wall, Norvel W 117 Walls, Core, in Earth Dams 369 Masonry 474 Puddle, in Earth Dams 367, 371 Steel 367 Walnut Grove Dam 389 Waste Land, Percentage of 55 Weirs, Discharge of 482 Wasteway Gate, Automatic 226 Taintor 246 Weirs, Shapes of 484 Wasteways 239 Carmel Reservoir 487 Character and Design of 482 Classes of 483 622 INDEX Wasteways, Examples of 486 Location and Characteristics of 240 Reclamation Service 244 Water, Artesian, Storage of 96 Center of Pressure of 59 Chemical and Physical Properties of 58 Depths of, required to Soak Soil 52 Distribution, Rotation in 55 Divisors 89 Duty of 57 Linear and Areal 54 Measurement of 50 Reference Works on 57 Table of 51 Units of Measure for 47 Excessive Use of 39 Factors affecting Flow of 61 Falls, Power in 524 Flow of, in Pipes 338 Flow and Measurement of, in Open Channels, Works of Reference on . . 89 Formulas for Flow of 61 Gathering-Cribs for 107 Ground, Motion of 91 Measurement of Canal 85 Measurement of, in Pipes 350 Meter, Foote's 87 Venturi 350 Methods of Applying . . 321 Motion of 60 Motors 5 26 Physical Properties of 58 Power of Falling 524 Pressure of 59 Quantity per Service and Irrigation Period 53 Relation of, to Plant Growth 313 Scouring Effect of Falling 183 Seepage of 3 1 Sources of Earth 9 1 Other Subsurface 107 Storage, Effect of Evaporation on 28 Supply and Land, Relation between 126 of Reservoir Site to 354 Tunneling for 105 Units of Measure of, Table .......... 48 Velocities of Flow of 65, 148 Weight of 5 8 Water -cushion on Wooden Fall 264 Water -cushions J 86 INDEX 623 Water-logging 35 Prevention of 35 Water-power, Uses of 536 Water-pressure Engines 537 Water Users' Associations 569 Water-wheel, Breast 526 Horizontal 526 Hurdy-gurdy 526 Mid-stream 528 Overshot 526 Pelton ..... 526, 534 Poncelet 528 Turbine 532 Undershot 5?6, 527 Vertical 526 Wave Heights and Fetch 380 Weeds 44 Wegmann, Edward, Jr 407, 412, 418, 508 Profile Type for Masonry Dam 410 Weir Aprons 183 Arizona Canal 180 Assiout 122, 457 Bear River Canal 180 Calloway Canal 168 Cohoes Iron Rollerway 196 Concrete, Ashlar Facing 194 Conditions of using Rectangular 79 Corbett 201 Croton 192 Formulas, Francis* 78 French Movable . 176 Gates and Shutters, Automatic 488, 491 Gauge Heights 80 Goulburn Masonry and Iron Drop-gate 196 Granite Reef 202, 215 Henares, Spain 194 Holyoke, Mass 208 Laguna 175, 214 Leasburg 190 Lower Yellowstone 182 Minidoka, Idaho 385 Movable French 176 Norwich Water Power Co., Conn 191 Pequannock River, Newark, N. J 206 Reinforced Concrete 200 Rolling Lift 177 Rubble Masonry 195 Sidhnai 174 624 INDEX FACE Weir Soane 172 Theresa 200 Vir, India 195 Weirs, Broad-crested 80 of Brush and Bowlders 165 Classes of 165 Construction of Crib 179 Crib and Rock 179 Discharge over 80, 482 Diversion 164 Flashboard or Open-frame 168 Indian Type 170 of Iron 196 Movable 176 Masonry 188 founded on Cribs 192 Piles 190 and Cribs 191 Wells 192 and Iron Drop-gate 196 Open Indian Type 170 Measuring 77 Ogee or Rollerway Shaped 185, 196 Open and Closed 166 Open Iron Frame, French Type 176 Pile 1 66 Rectangular Measuring 77 Relation of, to Regulators 227 Rollerway or Ogee-shaped 185, 196 Table of Discharge over Rectangular 81 Trapezoidal 83 Trapezoidal 79 Waste, Discharge of ' 482 Shapes of 484 Wooden Crib and Rock 179 Weisbach, P. J 90, 312, 352, 508, 563 Wells, Artesian 94 Capacity and Cost of 95, 507 Drilling, Manner 97 Machines 98 Process of 100 Examples of 94 Power-Pumped 103 Sizes of 96 Sources of 93 Stove-pipe Casing for 101 Wells as Foundation for Masonry Weirs 192 Supplying Capacity of Common 102 INDEX 625 Wheel, Persian 515 Whiting, J. G 312 Wide-Crested Dams 420 Wilcox, W 312 Lute .352 Williston Pumping-Plant 554 Wilson, H. M 33, 46, 57, 312, 563 Windlass, Wooden Regulator Gate raised by 234 Windmills 515 Capacity and Economy of 516 Value of, as Irrigating Machines 523 Varieties of 519 Winch, Regulator Gate Lifted by Travelling 235 Wisner, George Y 415 Wolff, A. R . 517,563 Wooden Lateral Heads 304 Fall with Water-cushion 264 Fall, Simple, Vertical 263 Flashboard Regulators 232 Inverted Siphons 289 Pipes, Construction of 346 Rapids or Chutes 264 Regulator Gate lifted by Lever 234 Windlass 234 Stave Pipes 346 Work, Equivalent Units of 547 Works, Canal Diversion 1 26 Works on Canals, Maintenance and Supervision of 560 Works of Reference Alkali, Drainage, and Sedimentation 46 Application of W T ater and Pipe Irrigation 352 Artesian Wells 117 Diversion and Canal Works 311 Duty of Water 57 Evaporation, Absorption, and Seepage 33 Flow and Measurement of Water in Open Channels . . 89 Precipitation, Runoff, and Stream Flow 2 r Pumping 562 Sedimentation 46 Sewage Irrigation 117 Storage Works 507 Subsurface-water Sources 117 Works, Storage 352 Yellowstone Canal Wasteway ,. . 245 Weir 182 Yuma Project, Colorado River 214 Zola Dam 4 1 6, 47 1 RETURN TO the circulation desk of any University of California Library or to the NORTHERN REGIONAL LIBRARY FACILITY Bldg. 400, Richmond Field Station University of California Richmond, CA 94804-4698 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 2-month loans may be renewed by calling (510)642-6753 1-year loans may be recharged by bringing books to NRLF Renewals and recharges may be made 4 days prior to due date DUE AS STAMPED BELOW 20,000 (4/94)