Main Lib. >igric. Dept. WORKS OF H. M. WILSON PUBLISHED BY JOHN WILEY & SONS, INC. Topographic, Trigonometric and Geodetic Sur= veyinjc. Including Geographic, Exploratory, and Military Mapping, with Hints on Camping, Emergency Sur- gery and Photography. Third Edition, Revised. Illustrated by 18 engraved colored plates and 205 half-tone plates and cuts, including two double- page plates. 8vo, xxx + gi2 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 ARTHUR POWELL DAVIS, D.Sc Mem. Ant. Soc. C.E.; Director and Chief Engineer U. S. Reclamation A utJior of " Irrigation IVorks Constructed by the United States," etc. AND HERBERT M. WILSON, C.E. Mem. Am. Soc. C.E.; Former Chief Engineer and Irrigation Engineer, U. S. Geological Survey; Author of " Topographic Surveying," etc. SEVENTH EDITION, REVISED AND ENLARGED TOTAL ISSUE TWELVE THOUSAND NEW YORK JOHN WILEY & SONS, INC. LONDON: CHAPMAN & HALL, LIMITED 1919 COPYRIGHT, 1896, 1903, 1905, 1909 By HERBERT M. WILSON COPYRIGHT, 1919 By ARTHUR P. DAVIS and HERBERT M. WILSON PRESS OF BRAUNWORTH & CO. BOOK MANUFACTURERS BROOKLYN, N. Y. PREFACE TO SEVENTH EDITION THE first edition of " Irrigation Engineering," was a pioneer in its field, and quickly took its place as the recognized stand- ard therein, as indicated by its passage through six successive editions. At the date of the first edition and in fact, some time later, the large irrigation works of engineering interest were mostly in India and Egypt. Mr. Wilson's familiarity with those works, based largely on personal contact with them and their builders and operators, gave the early editions of his work a special value as contributions to western knowledge of this subject. The subsequent activity in irrigation in other parts of the world, especially in the United States, together with similar developments in related lines of municipal water supply and hydro-electric construction, have presented new problems and evolved new solutions of old ones to such an extent that what might almost be called a new science has been developed, requir- ing different treatment. Moreover, social, political and eco- nomic conditions in America are radically different from those in the Orient, and this imposes very different conditions and limitations upon the practice of irrigation engineering. Sir William Willcocks, on his visit to America, said he was accustomed to look upon the irrigation industry as one abso- lutely dependent upon cheap labor like that of Asia and Africa, and that his chief interest in examining American irrigation was to learn how it was that irrigation could be practiced at all in America. American irrigation practice therefore is very different from that of India, and has been largely developed quite recently. 394095 VI PREFACE TO THE SEVENTH EDITION When .the undersigned was requested to revise this work for a seventh edition, he undertook the task under the handi- cap of having his time very fully occupied by official duties, without fully realizing the magnitude of the task. The material of the sixth edition relating to sewage disposal and irrigation and to subterranean water supply has been liberally used. A few other portions have been used in part, and about 40 per cent of the illustrations have been utilized. In the main the work has been rewritten and rearranged, and much new material has been added. The principal difference introduced is the treatment of soils, plant food, operation and maintenance, and other lines of work where the duties of the irrigation engineer come in contact with the irrigator, such as the preparation of land, the duty of water and its application to the land. No attempt has been made to treat these nor indeed any other branches of the subject exhaustively, which cannot be done within the limits of such a work as this. It is hoped the results justify their publication, and will continue the usefulness of the work so well pioneered by Mr. Wilson. In writing and compiling this work much assistance has of course been drawn from existing literature, and references are made to the same at the ends of chapters, and in the text. A. P. D. TABLE OF CONTENTS PAGE LIST OF ILLUSTRATIONS . X vii CHAPTER I INTRODUCTION i 1. History 2 2. Extent of Irrigation 4 3. Malarial Effects of Irrigation 5 CHAPTER II SOILS 7 1 . Residual 7 2. Alluvial 7 3. Eolian 7 4. Glacial 7 5. Injurious Salts 8 a. Percentage in Soils 9 b. Resistance of Various Crops 1 1 6. Remedies for Alkali 12 a. Leaching 12 b. Plowing 13 c. Growth of Suitable Plants 13 d. Mulching 14 e. Gypsum. 14 CHAPTER III SOIL MOISTURE - 16 1. Free Water 16 2. Capillary Water 16 3. Hygroscopic Water 16 4. Capillary Movement 17 5. Optimum Water Supply 18 6. Wilting Coefficient 20 7. Water Required for One Irrigation 20 vii Vlll CONTENTS CHAPTER IV PAGE PLANT FOOD 22 1. Functions of Water in Plant Growth 22 2. Mineral Foods 23 3. Fertilizing Effect of Sediments 25 CHAPTER V WATER SUPPLY 27 1. Causes of Rainfall 27 2. Types of Rainfall 32 a. Pacific Type 32 . b. Rocky Mountain Type 35 3. Stream Flow 37 4. Laws of Runoff 40 a. Drainage Area 40 b. Rainfall 40 c. Character of Rainfall 41 d. Evaporation 41 e. Topography 41 /. Soil 41 g. Geologic Structure 41 h. Vegetation 41 5. Discharge of Western Streams 42 6. Subsurface Water Sources 45 a. Rate of Percolation 46 b. Permeability of Soils 47 7. Artesian Wells 48 a. Examples 50 b. Capacity 51 c. Storage of Artesian Water 51 d. Size of Well 52 e. Methods of Drilling 53 /. Varieties of Drilling Machines 53 g. Process of Drilling 54 h. Capacity of Common Wells 57 8. Tunneling for Water 59 9. Other Subsurface Water Sources 61 10. Character of Water 61 CHAPTER VI EVAPORATION .' 65 1. Measurement of Evaporation 66 2. Amount of Evaporation 68 3. Evaporation from Snow and Ice 68 CONTENTS ix PAGE 4. Evaporation from Earth 69 5. Effect on Water Storage 70 CHAPTER VII PUMPING FOR IRRIGATION 73 1. Ground- water Supply 74 2 . Windmills 75 3. Water-wheels 78 a. Undershot 79 b. Overshot 81 c. Turbines 82 d . Pelton Water-wheels 84 4. Internal Combustion Engines 84 5. Hot Air, Gasoline and Alcohol Pumping Engines 85 6. Steam Power 86 7. Pumps 86 8. Direct Pumping 90 9. Hydraulic Ram 91 10. Air-lift Pumping 92 11. Hydro-electric Pumping 92 12. Humphrey Direct-explosion Pump 95 13. Rice Irrigation 97 CHAPTER VIII IRRIGABLE LANDS 99 1 . Topography 99 2. Soil Survey 101 3. Preparation of Land 104 a. Clearing 104 b. Leveling 107 c. Ditching no CHAPTER IX APPLICATION OF WATER TO THE LAND in 1. Methods of Irrigation in a. Free Flooding in b. Border Method 112 c. Furrow Irrigation 117 d. Corrugation System 119 e. Leveling 1 20 2. Sewage Disposal 123 3. Sewage Irrigation 127 4. Fertilizing Effects of Sewage 128 CONTENTS 5. Effects of Sewage Irrigation on Health 129 6. Duty of Sewage 130 7. Methods of Applying Sewage 130 8. Sub-irrigation 133 CHAPTER X DUTY OF WATER 137 1. Length of Season 138 2. Natural Rainfall 138 3. Soil Conditions 139 4. Crops Raised 139 5. Preparation of Ground and Ditches 140 6. Skill of the Irrigator 140 7. Care with which Water is Used 140 8. Cultivation 140 9. Utah Experiments 141 10. Agricultural Department Experiments 143 11. U. S. Reclamation Service 144 12. Inquiry of American Society of Agricultural Engineers 148 CHAPTER XI MEASUREMENT OF IRRIGATION WATER 153 1 . Gaging Streams 153 2. Use of Current Meter 157 3. Hydraulic Formulae 163 4. Measurement of Water to the User 164 5. Measuring Devices 165 a. Weirs 166 b. Orifices . . . 168 c. Hanna Meter 1 73 d. Azusa Hydrant 1 73 e. Foote Measuring Box 1 73 f. Dethridge Meter 1 75 "g. Hill Meter .176 h. Grant-Mitchell Meter 177 i. Venturi Meter 177 j. Venturi Flume 1 78 CHAPTER XII DRAINAGE 184 1. Signs of Seepage 185 2. Classification of Drains 191 3. Design of a Drainage System 193 CONTENTS xi 4. Location of Drains 193 5. Depth .195 6. Capacity 195 7. Form of Tile 196 8. Manholes 197 9. Wooden Drains 198 10. Cement Pipe Drains 198 11. Drainage Works of U. S. Reclamation Service 200 CHAPTER XIII CANALS AND LATERALS 202 1 . Capacity of Canals 202 2. Design 205 3. Alinement 212 4. Velocity 215 5. Lateral Systems 217 6. Design of Laterals 220 7. Capacity of Laterals 221 8. Location of Laterals 222 9. Abnormal Leakage from Canals 224 10. Construction of Canals 227 11. Canal Losses and their Prevention 233 12. Seepage Losses _ 234 13. Seepage Formula 235 14. Canal Lining 236 15. Amount of Return Seepage 245 CHAPTER XIV CANAL STRUCTURES 247 1 . Classification 247 2. Location of Headworks 247 3. Canal Headgates 248 4. Turnouts 263 5. Canal Spillways 271 6. Checks, Drops and Chutes 284 7. Protection against Erosion 290 Drainage Crossings 293 Flumes 299 10. Behavior of Various Metals in Presence of Alkali 308 11. Culverts 314 12. Pipes . 323 13. Tunnels 330 14. Highway Crossings .335 15. Sand Traps 337 xii CONTENTS CHAPTER XV PAGE STORAGE RESERVOIRS 342 1. Classes of Storage Works 342 2. Selection of a Reservoir Site 343 3. Geology of Reservoir Sites 344 4. Leakage from Reservoirs 346 5. Survey of Reservoir Sites 353 6. Spillway Provisions 354 7. Outlet Works 358 CHAPTER XVI SEDIMENTATION OF RESERVOIRS 370 1. Measurement of Sediment 371 2. Sediment Rolled on Bottom of Stream 373 3. Removal of Silt from Reservoirs 376 CHAPTER XVII DAMS 381 1. Conditions of Safety 381 2. Diversion Dams or Weirs 382 a. Timber Dams 382 b. Rectangular Pile Weirs 384 c. Open and Closed Weirs 386 d. Flashboard Weirs 388 e. Indian Type Weirs 390 /. Automatic Gates 392 g. Automatic Drop Shutters 392 h. French Type of Weir 394 /. Roller Dams 394 i. Crib Dams 401 k. Submerged Dams 402 3. Storage Dams 404 a. Earthen Embankments ' 405 b. Foundations . 405 c. Springs in Foundations 408 d. Safe Slopes 409 e. Slope Protection 413 /. Percolation 417 g. Methods of Construction 424 h. Hydraulic Fill 426 4. Rockfill Dams 436 CONTENTS xiii CHAPTER XVIII PAGE MASONRY DAMS 442 1. Classification 443 2. Methods of Failure 44 3. Pressures in Masonry 444 4. Failure by Sliding 447 5. Failure by Overturning 449 6. Miscellaneous Forces 450 7. Design of Gravity Dams 453 8. Design of Arch Dams 469 9. Masonry Overfall Dams 475 10. Hollow Concrete Dams 478 1 1 . Steel Dams 487 a. Steel Dam, Ash Fork, Arizona 487 12. Foundations for Masonry Dams 490 13. Exploring Foundation 493 CHAPTER XIX WATER RIGHTS 496 1. Nature of Property in Water 496 2. Riparian Doctrine 496 3. Doctrine of Appropriation 496 4. Appurtenance to Land 500 CHAPTER XX OPERATION AND MAINTENANCE 502 1. Personnel 502 a. Manager 502 b. Canal Superintendent 502 c. Canal Riders 503 d. Hydrographers 503 e. Cooperation with Water Users 504 2. Economy of Water 504 3. Wanton Waste 511 4. Rotation Delivery 512 5. Basis of Charges 514 6. Cultivation 515 7. Winter Operation 516 8. Maintenance 518 9. Erosion of Canal Banks 519 10. Silt Deposits 520 11. Alkali 521 XIV CONTEXTS PAGE 12. Aquatic Plants 521 13. Wind Erosion 524 14. Noxious Plants 525 15. Burrowing Animals 525 16. Land Slides 526 CHAPTER XXI INVESTIGATION OF A PROJECT 528 1. Reconnaissance 528 2. Surveys 528 3. Estimates of Cost 531 a. Bias 531 b. Influence 532 c. Inaccurate Data 532 d. Omissions 532 CHAPTER XXII SPECIFICATIONS FOR CONSTRUCTION 534 1. Specifications for Arrowrock Dam 535 2. Contract Specifications of the Reclamation Sendee 547 a. General Requirements 547 b. Special Requirements 554 3. Standard Paragraphs for Purchase of Material 555 4. Earthwork on Canals 556 5. Concrete 559 6. Structural Steel 561 7. Steel Reinforcement Bars 562 8. Gray Iron Castings 563 9. Malleable Castings 564 10. Steel Castings 564 1 1 . Cement 565 12. Continuous Wood Stave Pipe . 566 13. Machine Banded Wood Stave Pipe 569 14. Laying Machine Banded Wood Stave Pipe 571 15. Steel Pipe -572 16. Jointed Reinforced Concrete Pipe 574 1 7. Metal Flumes 576 18. Steel Highway Bridges 579 19. Tunnels '. 584 20. Telephone System 586 21. Vitrified Pipe, for Culverts 590 CONTENTS xv CHAPTER XXIII PAGE TABLES 592 1. Extreme Flood Discharges , . . . 593 2. Table of Reservoirs 598 3. List of Earth and Rockfill Dams .' 599 4. List of High Masonry Dams 600 5. Velocity Tables 602 6. Tables of Area and Hydraulic Radius 611 7. Velocity Heads 614 8. Weights of Various Substances 615 9. Convenient Equivalents 616 LIST OF ILLUSTRATIONS FIG. PAGE 1. Mean Annual Precipitation in the United States 29 2. Percentage of Annual Precipitation Occurring between April ist and September 3oth 30 3. Mean Precipitation Occurring between April ist and September 3oth. . . 31 4. Diagram Showing Effect of Topography on Rainfall in California 33 5. Discharge of San Joaquin River at Herndon, California, 1900 33 6. Discharge of Neosho River near lola, Kansas, 1900 34 7. Discharge of Boise River at Boise, Idaho, 1899 34 8. Discharge of Salt River at McDowell, Arizona, 1899 35 9. Discharge of Green River at Green River, Wyoming, 1899 35 10. Types of Monthly Distribution of Precipitation in the United States. (After A. J. Henry.) 36 11. Ideal Section Illustrating Condition of Artesian Wells 49 12. Ideal Section Illustrating Thinning out of Water-bearing Stratum 50 13. Portable Artesian Well Drilling Rig 55 14. Subterranean Water Tunnel and Feed Wells, California 60 15. Gathering Cribs, Citizen's Water Company, Denver, Colorado 61 16. Evaporating Pan 67 17. Windmill and Reservoir near Garden City. Kansas 88 18. Battery of Hydraulic Rams, Yakima Valley, Washington 88 19. Undershot Waterwheel 89 20. Current Wheel or Noria, Lifting Water from Salmon River for Irrigation . 89 21. Diagram Illustrating Principle of Hydraulic Ram 91 22. Scoop Wheel Lifting Water 3^ Feet 60 per Cent Efficient 94 23. Direct-explosion Pumping Plant to Raise Irrigating Water 37 Feet 95 24. Shoshone Desert before Irrigation 100 25. Shoshone Desert after Irrigation 101 26. Slip Scraper 106 27. Adjustable V for Making Head Ditches 107 28. Leveling New Lands, Idaho .- 108 29. Fresno Scraper 109 30. Float for Leveling Irrigable Lands no 31. Using Canvas Dam 113 32. Steel Dams "3 33. Diverting Water from Head Ditch, Canvas Dam, Shoshone Valley, Wyo- ming i M xvii XVlll LIST OF ILLUSTRATIONS 34. Drawing Water from Head Ditch through Small Pipes, Riverside, Cali- fornia j i 5 35. Field Prepared for Irrigation by Checks 1 16 36. Border Irrigation in Nevada 116 37. Diagram Illustrating Flooding in Rectangular Blocks or Checks. Cowgill. 1 1 7 38. Orchard Irrigation by Furrow Method, Yakima Valley, Washington. 118 39. Furrow Irrigation of Cabbages, Yuma, Arizona 119 40. Furrow Irrigation on Terraced Hillside, California 1 20 41. Irrigating Orchard by Terraced Basins on Hillside 121 42. Orange Trees Irrigated by Check System, Salt River, Arizona 122 43. Furrow Irrigation of Orange Grove, Riverside, California 122 44. Extent of Percolation from Small Furrows: A, in Loose Loam; B, in Hardpan; C, in Impervious Grit 1 23 45. Irrigating with Large Head by Border Method from Cement Head Ditch, Salt River Valley, Arizona 1 24 46. Irrigating Corn with Sewage, Plainfield, N. J 125 47. Furrow Irrigation of Apple Orchard, Idaho 125 48. Haskell Current Meter 155 49. Price Electric and Acoustic Meters 156 50. Water Stage Recorders 160 51. Cable Gaging Station with Automatic Continuous Recording Gage 161 52. Cable and Car Gaging Station 161 53. Wire and Boat Gaging Station 162 54. Rectangular Measuring Weir 173 55. Foote's Measuring Weir, A ; Water Devisor. B 174 56. Australian Water Meter 177 57. Venturi Meter and Recording Device on Lateral Head 177 58. Curve Showing Fluctuation of Ground Water and Application of Irriga- tion Water in the Rio Grande Valley. After Burkholder 187 59. Curve Showing the Seasonal fluctuation and Yearly Rise of Ground Water in Boise Valley, Idaho. After Burkholder 188 60. Curve showing Rise of Ground Water before Construction of Drains and Effect of Drains. Boise Valley, Idaho. After Burkholder 189 61. Excavating Trench for Tile Drain, Montana 192 62. Dragline Excavator on Drainage Work, Idaho 192 63. Cross-sections of Interstate Canal, North Platte Valley, Nebraska 204 64. Canal Cross-sections for Varying Bed Widths 206 65. Various Canal Cross-sections 206 66. Rock Cross Section, Turlock Canal 207 67. Rock Cross-section, Umatilla Canal 208 68. Cross-section of Galloway Canal in Sand, Showing Sub-grade 211 69. Typical Section of Lined Canal 211 70. Tunnel and Canal Sections, Tieton Main Canal 213 71. Diagram Illustrating Distributary System 218 72. Cavity Developed in Canal Bed, Flathead Reservation, Montana 225 73. Cave Developed in Bottom of Canal, Flathead Indian Reservation 226 74. Building Lateral in Montana with Ditching Machine 228 LIST OF ILLUSTRATIONS xix FIG. PAGE 75. Building Irrigation Lateral in Montana with Elevating Grader 228 76. Building Canal with Elevating Grader 229 77. Building Canal with Fresno Scrapers 233 78. Cross-section of Santa Ana Canal, Lined with Boulders Set in Cement. . . 237 79. Check Gates and Canal Lined on One Side. Interstate Canal 239 80. Semicircular Concrete Lined Section of Main Canal, Umatilla Valley, Oregon 239 ST. Concrete Lining Truckee-Carson Canal, Nevada 240 82. Reinforced Concrete Lining, Tieton Canal, Washington 241 83. Transition from Rock to Earth Cross-section Lined Canal 242 84. Lining Canal with Concrete, Idaho 244 85. Cross-section of Corbett Weir, Shoshone Project, Wyoming 248 86. Plan of Corbett Dam and Headworks, Shoshone Project, Wyoming. 249 87. Wooden Gate, Leasburg Canal Regulator, Rio Grande, New Mexico. 250 88. Iron Regulator Gate, Minidoka Canal, Idaho 250 89. Cast-iron Sluice-gate, Interstate Canal, Nebraska- Wyoming 251 90. Diversion Works, Lost River, Oregon 252 Regulator Gates, Laguna Weir, Colorado River 253 Inclined, Falling Regulator Gates, Goulburn Canal, Australia 254 Sunnyside Dam, Canal and Headworks, Yakima Valley. Headgates in Line with Dam 255 94. Regulating Gates and Sluice Gates at Right Angles to Each Other, Yuma Main Canal, California 256 95. Whalen Diversion Dam and Headgates, Normal to Dam, North Platte River, Wyoming 257 96. Sprague River Dam, Klamath Indian Reservation, Oregon 258 97. Plan and Elevation of Headworks, Interstate Canal, North Platte River, Wyoming 259 98. Jackson Lake Dam, Downstream Face, Wyoming 260 99. Headgates and Sluice Gates, Montrose and Delta Canal, Umcompahgre Valley, Colorado. Obtuse angle 260 100. Division Gates and Drops on Tsar Canal near Byram Ali, Murgab Valley, Turkestan 261 101. Headworks of Sultan Yab Canal at Sultan Bend Reservoir on Murgab River, Turkestan 261 102. Cross-section and Elevation of Regulator Gates, Folsom Canal 262 103. Wooden Head to Lateral, Sun River Canal, Montana 263 104. Concrete Check and Farm Turnout with Inclined Valve 264 105. Cast-iron Valve on Small Lateral Turnout 265 106. Standard Turnout, Vitrified or Concrete Pipe, U. S. R. S\ 266 107. Standard Turnout Box Concrete, U. S. R. S 267 108. Reinforced Concrete Turnout with 10 Foot Drop, Garland Canal, Wyo- ming 268 109. Cast-iron Gates for Laterals, Interstate Canal, Wyoming-Nebraska. 269 no. Reinforced Concrete Turnout for Lateral 270 in. Lateral Headgates, North Platte Valley, Nebraska 271 112. Standard Spillway, Length of Weir less than 100 Feet. U. S. R. S 272 XX LIST OF ILLUSTRATIONS FIG. PAGE 113. Standard Spillway, Length of Weir over TOO Feet. U. S. R. S 273 114. Keno Canal Spillway, Klamath Falls, Oregon 274 115. Plan and Section of Siphon Spillway, on Canal in Colorado Valley, Cal. 276 116. Spillway, Fort Shaw Canal, Montana 277 117. Standard Sluiceway, Lower Yellowstone Canal, Montana 278 1 1 8. Waste way, Lower Truckee Canal, Nevada 279 119. Tieton Main Canal, Lined Section 281 120. Concrete Drop with Water Cushion, Truckee-Carson Canal, Nevada 283 121. Notch Drop, Chenab Canal, India 284 122. Cross-section of Fall. Bear River Canal 285 123. Notch Drop, Interstate Canal, Wyoming-Nebraska 286 124. Timber Drop, Lower Yellowstone Laterals, Montana 287 125. By-pass Feeder from Upper to Lower Canal, Umatilla Project, Oregon 288 126. Cylinder Drop on Franklin Canal, Rio Grande Valley, Texas 289 127. Series of Concrete Drops on South Canal, Uncompahgre Valley, Colorado. 290 128. Concrete Chute and Stilling Basin, Boise Valley, Idaho 291 129. Reinforced Concrete Chute, Okanogan Project, Washington 294 130. Pipe Inlet, Reno Coulee, Lower Yellowstone Canal, Montana 294 131. Elevation and Cross-section of Iron Flume on Corinne Branch, Bear River Canal, Utah 295 132. Standard, Reinforced, Concrete Flume, Reclamation Service 296 133. Circular Reinforced Concrete Flume and Trestle, Tieton Canal, Wash- ington 297 134. Head works of Cavour Canal, Po River, Italy 298 135. Brick Aqueduct Carrying Cavour Canal, Po Valley, Italy 298 136. Bench Flume, High Line Canal, Colorado, Spillway in Foreground. 300 137. View of Solani Aqueduct, Ganges Canal, India 301 138. Cross-section of San Diego Flume, California 302 139. Cross-section of Stave and Binder Flume, Santa Ana Canal, California. 302 140. Section through Reinforced Concrete Aqueduct, Interstate Canal, Wyo- ming-Nebraska 303 141. Mill Creek Flume, Steel Frame and Bridge, Santa Ana Canal, Cal. 304 142. Steel Flume, Tieton Distribution System, Yakima Valley, Washington. 306 143. Steel Flume Crossing Eight-mile Creek, Boise Valley, Idaho 307 144. Half Longitudinal Section, Reinforced Concrete Aqueduct, Interstate Canal, Wyoming-Nebraska 308 145. Reinforced Concrete Aqueduct, Spring Canyon, Interstate Canal, Wyom- ming-Nebraska .- 3 10 146. Concrete Flume, Spanish Fork Valley, Utah, Showing Warped Transition from Canal to Flume 310 147. View of Ranipur Superpassage, Ganges Canal, India 311 148. Continuous Wood Stave Pressure Pipe, Idaho Irrigation Company's Canal 312 149. Elevation and Cross-section of Nadrai Aqueduct, Lower Ganges Canal. 313 150. Reinforced Concrete Culvert, Lower Yellowstone Canal, Montana. 315 151. Burn's Creek Superpassage, Lower Yellowstone Canal, Montana. 316 152. Inlet to Rawhide Siphon, Interstate Canal, Wyoming-Nebraska 317 LIST OF ILLUSTRATIONS XXI FIG. PAGE 153. Siphon Crossing under Rawhide Creek, Interstate Canal, Wyoming- Nebraska 317 154. Reinforced Concrete Twin Siphon, Interstate Canal, Wyoming-Nebraska. 319 155. Reinforced Concrete Twin Siphon > Fox Creek Crossing, Lower Yellow- stone Canal, Montana 320 156. Main Canal, Concrete Lined, Okanogan Project, Washington 321 157. Happy Canyon Steel Flume, Uncompahgre Valley, Colorado 322 158. Steel Bridge and Wood Stave Pressure Pipe, Yakima Valley near Prosser, Washington 327 159. Steel Forms and Reinforcement for Concrete Pressure Pipe, Boise Valley, Idaho 328 1 60. Removing Inside Steel Forms from Concrete Pressure Pipe 329 161. Manhole and Concrete Collars on Concrete Pressure Pipe, Boise Valley, Idaho 329 162. High Line Canal, Spanish Fork Valley, Utah, Covered to Protect Against Land and Snow Slides 336 163. Headgates, Sluicegates and Sand Basins, High Line Canal, Spanish Fork, Utah 336 164. Cross-section of Sandbox, Santa Ana Canal 338 165. Sandbox, Leasburg Canal, Rio Grande Valley, New Mexico 339 1 66. Standard Sluiceway and Sandgate, Lower Yellowstone Canal, Montana- North Dakota - 340 167. Curves of Seepage from Deerflat Reservoir Showing Improvement with Use 348 168. Gatehouse Conconully Dam, Washington 360 169. Vertical Lift Outlet Gate, Fay Lake Reservoir, Arizona 361 170. Valve Plugs: A, Sweetwater, and B, Hemet Dams 362 171. Outlet W T orks Lahontan Dam, Carson River, Nevada 363 172. Section of Balanced Valve, Arrowrock Dam, Boise River, Idaho 365 173. Outlet Conduit Keechelus Dam, Washington, Showing Concrete Cut-off Collars, Core Wall and Track for Backfilling on Left 366 174. Butterfly Valve, Minatare Dam. Nebraska 366 175. Elevation and Section of Butterfly Valve 367 176. Needle Valve in Outlet Conduit, Needle Dam, North Platte Valley, Nebraska 368 177. Trap for Measuring Sand Rolling on Bottom of Stream 375 178. Folsom Canal, View of Weir and Regulator 383 179. Folsom Canal, Plan and Cross-section of Weir 385 180. Plan and Section of Laguna Dam, Colorado River 385 181. Cross-section of Lower Yellowstone Weir, Montana : 387 182. Kern River Diversion Weir, Head of Galloway Canal 389 183. Cross-section of Open Weir, Galloway Canal 390 184. Cross-section of Indian Weirs 391 185. Cross-section of Shutter on Soane Weir, India 392 1 86. Automatic Drop Shutter, Betwa Weir, India 393 187. Falling Sluice Gate, Soane Canal, India 395 188. View of Open Weir on River Seine, France 396 xxii LIST OF ILLUSTRATIONS FIG. PAGE 189. View of Goulburn Weir, Australia 397 190. View of Rolling Dam. Grand River, Colorado 398 191. Section through Body of 7o-foot Roller Dam, Grand River, Colorado. 399 192. Section through Driven Hand 7o-foot Roller 400 193. Cross-section of Bear River Crib Weir 401 194. Cross-section of Upper Coffer Dam. Arrowrock Dam, Boise River, Idaho . 402 195. View of San Fernando Submerged Dam 403 196. Sections of Owl Creek Storage Dam, Belle Fourche Valley, South Dakota. 406 197. Plan of Lahontan Dam, Carson River, Nevada 408 198. Elevation and Cross-section of Strawberry Dam, Utah 410 199. Section of Kachess Dam, Yakima Valley, Washington 414 200. Profile, Plan and Section of Upper Deerflat Embankment. Boise Valley, Idaho : 416 201. Owl Creek Dam near Belle Fourche, South Dakota, showing Concrete Paving 418 202. Upper Deerflat Embankment Showing Beaching of Gravel Slope 418 203. Wheeled Scraper 425 204. Cold Springs Dam under Construction, Umatilla Valley, Oregon 427 205. Grooved Concrete Roller 427 206. Dam at Necaxa, Mexico 428 207. Trestles on Conconully Dam, Washington, Showing Method of Hydraulic Construction 431 208. Cross-section of Bumping Lake Dam, Naches River. Washington 433 209. Section of Sherburne Lakes Dam showing Gravel Core and Drains to Provide for Seepage Water 434 210. Sections of Conconully Dam, Salmon Creek, Washington 435 211. Rockfilled Dam, Snake River, Minidoka Project, Idaho 436 212. Plan and Cross-section of Bowman Dam 437 213. Elevation, Plan and Cross-section of Castlewood Dam, Colorado 438 214. Lower Otay Rockfilled Dam, California 439 215. Elevation and Cross-section of Walnut Grove Dam 440 216. Rockfilled Steel Core Dam, Lower Otay, California 440 217. Section of Elephant Butte Dam, Rio Grande, New Mexico 454 218. Elephant Butte Dam, Cableways and Mixing Plant, Rio Grande, New Mexico 455 219. Elevation of Arrowrock Dam, Boise River, Idaho 458 220. Maximum Section of Arrowrock Dam , 459 221. Plan of Arrowrock Dam, Boise River, Idaho 460 222. Elephant Butte Dam showing Construction in Alternate Columns 462 223. Cross-section of Periar Dam, India 463 224. Cross-section of New Croton Masonry Dam, New York 464 225. Plan, Cross-section and Outlet Sluices, San Mateo Dam, California. 466 226. Plan of Roosevelt Dam, Arizona 467 227. Maximum Cross-section of Roosevelt Dam, Arizona 468 228. Pathfinder Dam, North Platte River, Wyoming, Lower Face Showing Concrete Ladder and 6500 Second-feet of Water Discharging from Tunnel 470 LIST OF ILLUSTRATIONS xxiii FIG. PAGE 229. Upper Otay Masonry Dam, California 471 230. Meerallum Dam, India. Plan and Sections of One Arch 472 231. Cross-section of Bear Valley Dam, California 473 232. Plan and Elevation of Bear Valley Dam, California 473 233. Shoshone Dam, Wyoming. Analysis of Pressures 474 234. Cross-section of New Holyoke Weir, Mass 475 235. Cross-section of Granite Reef Weir, Salt River, Arizona 476 236. Cross-section of Norwich Water Company's Weir 477 237. Leasburg Diversion Weir, Rio Grande Valley, New Mexico 478 238. Cross-section of Old Croton Dam, New York 479 239. McCall's Ferry Dam, Susquehanna River, Pa., Showing Steel Forms Used in Construction 480 240. Cross-section of La Grange Overflow Masonry Dam, California 480 241. Granite Reef Dam, Salt River, in Flood, Showing Hydraulic Jump.. . 481 242. East Park Reservoir Spillway, Orland Project, California 482 243. Diversion Dam, East Park Feed Canal, Orland Project, California. 482 244. Elevation, Plan and Section of Three Miles Falls Dam, Umatilla River, Oregon. . 483 245. East Park Multiple Arch Spillway, Orland Project, California 485 246. Cross-section of Iron Weir, Cohoes, New York 486 247. Cross-section of Reinforced Concrete Weir, Theresa. New York 486 248. Steel Dam, Ash Fork, Arizona 488 249. Iron Face Rollerway Weir, Cohoes, New York 489 250. Standard Horseshoe and Circular Sections of Conduits 612 IRRIGATION ENGINEERING CHAPTER I INTRODUCTION IRRIGATION is the artificial application of water to soil to assist in the production of crops. Its most familiar form is the sprinkling of lawns in both arid and humid regions, and the contrast between the watered and unwatered lawns, even in a humid climate, illustrates its benefits. Wherever practiced, it is supplementary to the natural rainfall. Scientific irrigation involves a knowledge of the available water supply, its conservation and application to the land, the characteristics and needs of the different types of soil, and the requirements of the various crops to be produced. In general, irrigation is most extensively practiced in arid regions where agriculture without it is precarious or impracti- cable, but it is also applied to lands of the semi-arid regions to increase the yield, and to special crops in humid regions, such as rice, sugar cane, lawns, garden flowers and vegetables. In fact there are comparatively few regions so free from occa- sional drouth that irrigation would not be profitable if it could be cheaply provided. The surface of the earth is composed of land and water, the latter being roughly three-fourths of the area and not habitable by man. Of the remaining one-fourth or land area, more than half is either too cold or too rocky for cultivation, and of the remainder the major portion is too arid for the pro- duction of crops, and only in part useful for grazing or other purposes. Even of the humid area, a very large part is in tropi- 2 INTRODUCTION cal Africa and South America, ill-adapted to civilization and development by means known at present. Thus the area naturally available for cultivation is a very small proportion of the whole, but can in places be increased by artificially applying water to the soil where nature fails to do this. An irrigated region has certain advantages over a humid region in the production of crops. There is much advantage in being able to apply the w r ater at just the time and in just the quantity needed, and to withhold it at will. The soils of arid regions are apt to be better supplied with the mineral plant foods which have not been leached out by excessive rains, and the great promoter of life and growth, sunlight, is more intense and constant in an arid than in a humid region. If sufficient care and skill be applied to secure the full benefit of these important advantages, the acreage yields under irriga- tion may be made far larger than under natural precipitation. History. Agriculture by irrigation antedates recorded his- tory, and is probably one of the oldest occupations of civilized man; but the time and place of its origin are unknown. Vari- ous countries in Asia, Africa, Europe and America exhibit evidences of ancient irrigation works of prehistoric origin and unknown antiquity. The earliest records of Assyria, Babylon, Egypt, Persia, India, China, and practically every country of antiquity, bear testimony to ancient and well- developed practices of irrigation. At the time of the Spanish conquests in America, extensive and well-built irrigation systems existed, antedating the earliest traditions of the peoples using them. Traces of such works were found not only in South and Central America, but also in Southern Arizona, New Mexico, Colorado, and California. As a modern activity of the Anglo-Saxon race, irrigation in the United States seems to have had its origin in the Salt Lake Valley of Utah about the middle of the Nineteenth Cen- tury at the present location of the city of Salt Lake. The early settlers of California, Arizona and New Mexico extended the previous practices of the Spaniards and Indians in those States. HISTORY 3 During the early history of American irrigation farmers and groups of farmers naturally confined their efforts mainly to diverting small streams upon adjacent valleys, where the slope of the country and the topography was such as to make the work easy and cheap. With the values of western land then existing no expensive enterprise was practicable. Such development proceeding for nearly half a century, widely distributed over the arid region, irrigated in the aggregate a large area of land. The farmers employed the cheapest class of construction and seldom counted their own time in computing costs, which are hence reported very low. As land values increased and the easier projects had been developed more and more difficult ones were taken up, sometimes successfully and sometimes not. As the more difficult problems were attacked, corporate capital and the district system were employed and such projects as they could handle were gradually developed. The inherent difficulties, however, did not admit of much profit to the investor. In fact, in a majority of the cases, the investors lost a large part of their capital,, to say nothing of interest and profits, and though the general benefits in the development of the country were great and lasting, the losses made it more and more difficult to enlist capital in further irrigation enterprise. Various National laws were passed from time to time to encourage the irrigation of arid lands, the Desert-Land Act and the Carey Act, with their various modifications, being the most conspicuous examples, but all depending upon the invest- ment of private or corporate capital for actual construction. A great deal was accomplished under these acts in spite of the great and growing difficulties. The increasing difficulty of carrying out many large projects led to the passage in 1902 of the Reclamation Act, with the avowed object of enlisting National funds for the development of projects not feasible by private, corporate, district, or State enterprise. The acts provided for the segregation in a special fund of the receipts from the sale of public lands in the sixteen Western 4 INTRODUCTION States, and the investment of this fund in irrigation works, to be returned by the beneficiaries in small installments. Under the operations of this act more than a million acres have be.en irrigated, the reclamation of which would not have been feasible for private enterprise for a long time if ever. Extent of Irrigation. The total area irrigated in various countries is estimated as follows: France 6,000,000 India 40,700,000 Italy 3,460,000 Russian Empire 8,000,000 Java 3,000,000 Egypt 5,350,000 Japan 7,000,000 Philippines 130,000 Australia 450,000 Canada 400,000 Hawaii 200,000 Argentina i ,000,000 Peru 640,000 Siam i ,750,000 United States 15,000,000 Total 93,080,000 In addition there are millions of acres irrigated in China Algeria and other countries, probably increasing the total to nearly 100,000,000 acres. Returns of Irrigation. The returns of irrigation 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. MALARIAL EFFECTS OF IRRIGATION 5 Irrigation adds to the general wealth of the country by in- creasing the amount of its agricultural products. 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 practiced, as mining, lumbering, graz- ing, 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 drouths occur and crops are lost. Where an irrigation system exists in such cases, it may 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. Malarial Effects of Irrigation. In some localities, irrigation has been denounced as a 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 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 by more sparing use of water and by proper drainage. Where the natural drainage is of the best, the soil 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 irrigation water does not breed malarial mosquitoes. On the other hand, in low-lying, comparatively level lands 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 practiced, but are frequently due to carelessly constructed canal works having intercepted the natural drainage, thus forming swampy tracts. When care is taken to irrigate economically land which has such slopes and natural drainage as to prevent waterlogging, no injurious effects will result from irrigation; furthermore 6 INTRODUCTION when malarial influences are developed by irrigation their effect is local, and can be corrected by drainage. If wholesome water and not open-ditch water be provided for domestic uses, prejudicial effects of irrigation are largely averted. In such climates as will encourage its growth it appears that the Eucalyptus globulus has proved beneficial 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. REFERENCES FOR CHAPTER I FORTIER, SAMUEL. Use of Water in Irrigation. McGraw-Hill Book Co., New York. WIDTSOE, JOHN A. Principles of Irrigation Practice. Macmillan Company, New York. WILSON, H. M. Irrigation in India, 1 2th Ann. Report U. S. Geological Survey, Washington. JAMES, GEORGE WHARTON. Reclaiming the Arid West. Dodd, Mead & Co., New York. HENNY, D. C. Federal vs. Private Irrigation. Engineering News, Jan. 15, 1915. NEWELL, F. H. The Human Side of Irrigation. Engineering Record, August 29, 1914. CHAPTER II SOILS ARABLE soils may be divided into four general classes with respect to their origin: (i) Residual; (2) Alluvial; (3) Eolian; and (4) Glacial. 1. Residual soils are the product of the disintegration of rock in place under the action of air, moisture, frost and vegeta- tion, all of which act upon most natural rocks. As moisture and vegetation are most abundant in humid regions, residual soils are there most general in consequence. 2. Alluvial soils are the deposits of sedimentation in bodies of still water, and of flowing streams upon their banks by over- flow, and by the accumulation of sediments in deltas at and near their mouths. 3. Eolian soils are those which have been deposited by wind action, and are common in the neighborhood of broad shallow streams or lakes, whose fluctuating waters leave broad bare stretches frequently exposed to wind action which removes and redeposits the surface with a sorting result, different from that of water. 4. Glacial soils are the deposits by glaciers of the products of glacial erosion and some other agencies. .All these classes differ widely in the methods and results of the mixing process, but many soils are the products of two or more of the agencies mentioned, and the original condition of the soil is generally modified superficially by the action of wind and rain. rThere are generally certain important differences between the soils of arid and humid regions, due to the difference of humidity. In humid regions the abundance of moisture tends to leach out the more soluble constituents of the soil,'\ and the 8 SOILS same cause promotes the luxuriant growth of vegetation, so that the tendency is to remoye the soluble minerals, and to accumulate vegetable mold. ( As most alkaline minerals are highly soluble, and are hence easily leached out of the soils of humid regions, and as the decay of vegetation produces certain organic ^acids, there is often a resulting acidity of soil in humid regions. \ In arid regions, on the contrary, the lack of moisture leaves the soluble minerals largely in the soiLj These-soils are therefore likely to contain much larger percentages of the various salts of potassium, sodium, and magnesium, as well as the less soluble phosphates, most of which are valuable plant foods. The arid condition being unfavorable to vegetable growth, the arid soils are generally deficient in vegetable mold, or humus, and sometimes this must be supplied before the soil becomes fer tile. -j-Most_aJka;Kne_saJjts. are soluble in water, and therefore these occur more generally in arid than in humid regions, and the soils of arid regions are more likely to be alkaline than acidjjand the alkalies are sometimes present to an extent injuri- ous to vegetation ; an excess of the salts of sodium being especially harmful. 5. Injurious Salts, or Alkali. While the aridity of western soils has its advantages in retaining the soluble salts in the soil, and thus preserving the plant foods, it sometimes happens that one or more soluble elements occurs in such abundance as to be injurious to vegetation. This is most important in the case of some of the so-called alkaline salts, as the carbonate, chloride and sulphate of sodium, and a few other salts less abundant and harmful. Alkalies found in natural soils are usually composed of a variety of salts, which possess widely different properties with relation to plant life. The most harmful alkali, and the one which becomes harm- ful with the least quantity is carbonate of sodium, Na2COs. This has caustic qualities, and in the presence of organic mat- ter takes on a dark brown color, from which it is often called " black alkali." INJURIOUS SALTS, OR ALKALI 9 Where the carbonates predominate, the presence of an average of one-tenth of one per cent of alkali in the root zone of any soil is disastrous to the growth of most useful crops, and for the best results the quantity should be much less. A somewhat greater quantity of chlorides and a still greater per- centage of sulphates can be tolerated. In general a soil having less than five-hundredths of one per cent oi soluble salts is acceptable, and one having more than five-tenths of one per cent of soluble salts is infertile. Between these limits, the fertility depends mainly upon the character of the salts and of the soil. Lyon and Fippin have compiled from analyses made by the U. S. Bureau of Soils, the following percentage composition of Various Natural Soils: TABLE I YAKIMA VALLEY, WASH., BOISE VALLEY, GREAT FORKF BILLINGS, MEADOW LAND IDAHO N. DAKOTA MONTANA Sur Surface Second Third Surface Surface Alkali 12-36 Crust face foot foot foot foot Deposit Crust ins. i in. KC1 5-6 7-8 8.1 1.8 1.8 5-5 K 2 SO 4 I 6 21 4 K 2 C0 3 8. 7 9-7 8.6 Na 2 SO 4 . .. . 16.5 67.? 85-6 35-1 Na 2 C0 3 . . . . 66.9 13-9 6.6 41-6 . I trace 7-3 NaCl 17.6 26.2 .6 trace MgSCV... .8 6.2 41-5 24-3 8.9 4-i MgCl 2 13-3 9.2 8.8 CaCl 2 I O NaHC0 3 ... 36.7 45-3 3i-3 .7 i-5 4-3 7 22.1 CaSO 4 9.1 1.9 6.2 .6 5-9 19.8 57-i 2.7 10. I Ca(HCO 3 )-> 16 ^ I -2 2 Mg(HC0 3 ) 2 12.6 12.3 KHCO 3 i i DeVries has shown that the presence of large amounts of salts dissolved in the water in contact with the roots of plants causes a shrinkage of the lining of the cells which, if persistent, causes the plant to wither and die. In addition to this, the car- 10 SOILS bonates of the alkalies have a corroding effect directly upon the plant tissues. An excess of alkaline salts sometimes encourages various plant diseases, and reduces the efficiency of tillage. The various crops are differently affected by the presence of alkali. Some native grasses, as salt grass and sacaton, are the most resistant, and of the cultivated grasses, timothy and alfalfa are the most tolerant. Of the cereals, barley is the most tolerant, and oats next. Sugar beets are more tolerant of alkali than most other root crops and cereals. The point at which alkalies become injurious is indefinite, and varies not only with the crop, but still more with the char- acter of the salt, the character of the soil and the presence of moisture. When the water content of the soil is large the dilution of the salt has an ameliorating effect, and as the soil dries out the solution becomes more concentrated, and hence more injurious. Clay and loam soils, by reason of their greater water-holding qualities, may carry more alkali without injury to plants than a sandy one. In general the salts of sodium are more injurious than others, carbonates are more injurious than chlorides, and chlorides are more injurious than sulphates. Potassium, calcium and phos- phorus are all valuable plant foods, and it is seldom that salts of these elements are present in quantities injurious to vegetation. Alkali is injurious of course only when it is in close contact with the tissues of the plant, that is when present in the root zone. The salts outside the root zone are harmless so long as they remain there. An excellent fertile soil containing a small percentage of alkaline salts may be ruined by the con- centration of salts in the surface layers of soil by the prolonged upward movement of water carrying the salts in solution and its evaporation from the surface. Wherever the water table is raised by percolation from higher lands and brought within a few feet of the surface capillarity does the rest, by establish- ing an upward movement from the water table to supply the draft of evaporation, and whatever salts the soil contains are carried to the surface in solution, and left there as the water evaporates. This concentration at the surface may be fatal INJURIOUS SALTS, OR ALKALI 11 to young plants whose roots are very delicate and are near the surface, while older plants of the same variety may not be injured because their roots are deeper where the salts are less concentrated, and because the older plants are more vigorous. On the other hand, the rising water table may injure deep- rooted plants before the salts are sufficiently concentrated at the surface to Injure those of shallow roots, and thus for a time a high water table may be fatal to alfalfa, while the cereals thrive on the same ground. This condition is usually temporary, however, as the tendency of a very high water table is to accumu- late soluble salts near the surface. On account of the wide variety of possible conditions affect- ing results it is impossible to lay down exact rules governing the amount of alkali that is injurious to vegetation. This varies with the salt and the infinite combinations of salts, with the crop, with the character of soil, with the moisture conditions, and with some minor circumstances. Any rule must therefore be regarded as only a general indication, and not an accurate guide. The following may be taken as rough limits: Sodium carbonate, Na 2 CO 3 o.i per cent Sodium chloride, NaCl 0.5 " " Sodium sulphate, Na 2 SO 4 i.o " " If any of these salts exceed these limits some of the ordinary crops will be injured and the soil is unsuitable for fruit. Resistance to Alkali. The investigations of Loughridge and others indicate relative alkali resistance of common crops roughly in the following order: 1. Salt grass 10. Barley 2. Salt bush n. Radish 3. Date palm 12. Sunflower 4. Modiola 13. Bean 5. Sorghum 14. Pea 6. Sugar beets 15. Grape 7. Hairy vetch 16. Artichoke 8. Kafir corn 17. Olive 9. Alfalfa (old) 18. Gluten Wheat 12 SOILS 19. Carrot 30. Onion 20. Wheat 31. Pear 21. Orange 32. Goats' rue 22. Celery 33. Canaigre 23. Almond 34. Mulberry 24. Lupine 35. Prune 25. Rye 36. Peach 26. Oats 37. Apple 27. Fig 38. Apricot 28. Alfalfa (young) 39. Lemon 29. Potato 6. Remedies for Alkali. 1 Where a field once fertile has been made sterile by the rise of ground water, bringing alkaline salts to the surface, there is no effectual remedy except to lower the ground water by means of deep drains. a. Leaching, If the condition is of long standing the alkali may have accumulated in the upper layers of the soil to such an extent that the land remains infertile after the water table has been lowered. Indeed the ground may then become still more sterile, and plants growing thereon may die, since, as we have already seen, a given percentage of alkali in the soil is less harmful with abundance of water than under conditions of less moisture. In such cases the soil must be leached of its super- fluous salts. This is accomplished by first providing adequate under drainage, and following this with copious irrigation, keeping the surface layers of soil saturated with water for protracted periods, so that there is a continuous downward movement of gravity water which escapes through the drains. -If this process is continued long enough it will effectually and permanently remove the superfluous salts, and of^ course much plant food at the same time. The time required will depend upon the freedom with which the water passes through the soil, the amount of salt to be removed, and some minor conditions, so that no rule can be given, but this should not consume more than one year, and under some conditions, it may be possible to produce some shallow- rooted crop at the same time. REMEDIES FOR ALKALI 13 Once the salts are removed to a sufficient extent, one or two years may be required to bring the soil to its original condition of fertility. The water-logged condition and also the presence of alkali operate to destroy the bacterial activities upon which the formation of plant food depends, and time and tillage are required to restore them. b. Plowing. Where soil containing only a moderate amount of alkali has, through bad tillage, had this accumulated at the surface to an injurious extent, advantage may be derived from deep plowing, so as to bring fresh soil without excessive alkali to the surface for the roots of the young plants, which will be more vigorous and resistant by the time the roots reach the alkali that has been turned under. c. Growth of Suitable Plants. Another practice from which benefit may be obtained where the excess of alkali is not great is to plant crops that are tolerant of alkali and consume or ab- sorb a considerable amount of it, and by repeated cropping gradually remove excess alkali from the root zone. 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 evaporation tends to restore the soil to its natural condition. Where mulching is practiced 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 nutritious, and has been successfully grown on alkaline land which will produce no other crop. This plant is remarkable for its productiveness and its drouth-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 reproduces itself from the same root. Its yield per acre is very large, being about the same as that of alfalfa. 14 SOILS d. Mulching. An excellent preventive against evaporation from the soil surface and the consequent rise of alkali is " mulching." A good 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 mini- mum, 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. Large quantities of straw produces also an effective mulch, since the straw keeps the sur- face moist and enables the grain to germinate. The depth or thickness of this protective layer is of the utmost importance for thereby the surface evaporation is diminished. After a proper plowing to a depth of, say, 10 to 12 inches, it requires a long time for the salts to come to the surface again in suffi- cient amount to injure the crop. e. Gypsum. Where the alkali is mainly carbonate of soda, much benefit may be derived by the application of ground gypsum or sulphate of calcium. This must be thoroughly mixed with the soil, and the two salts mingling in solution in the same water, in obedience to an elementary chemical prin- ciple, perform the following reaction: Na 2 C0 3 + CaS0 4 = Na 2 S0 4 + CaC0 3 . Forming Sodium Sulphate and Calcium Carbonate. The latter is only slightly soluble in water, and is harmless. The sodium is transformed into sulphate which is far less harmful than the carbonate, and is more easily removed by drainage. Experiments have been made by Prof. E. W. Hilgard which prove the value of gypsum in neutralizing the " black alkali," or carbonate of soda. In the case of this alkali 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 productive by the use of a ton of gypsum per acre. This is more effective when applied at the rate of about 500 pounds per acre per REMEDIES FOR ALKALI 15 annum in connection with some seeding at the same time, for the slightest growth aids in shading the ground and pre- venting 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 the gypsum plowed in, and water promptly applied. The sovereign preventive and cure for alkali of any kind, however caused, is deep drainage, supplemented if necessary by copious surface irrigation, to produce a downward move- ment of water from the surface to the drain. Where alkali is accumulated at or near the surface, efforts are sometimes made to remove it by heavy applications of water, drained off by surface drains. Such efforts seldom yield perceptible benefit, as the water that actually comes in contact with the salt, enters the soil and remains there or passes down- ward, while that which runs off the surface carries very little salt. REFERENCES FOR CHAPTER II BARK, DON H. Duty of Water Investigation in Idaho. 8th and pth Biennial Reports, State Engineer of Idaho, Boise, Ida., 1910-12. KING, F. H. Irrigation and Drainage. Macmillan Company, New York. ETCHEVERRY, B. A. Use of Irrigation Water. McGraw-Hill Book Company, New York. HILGARD, E. W. Soils. Macmillan Company, New York. LYON & PIPPIN. Soils. Macmillan Company, New York WIDTSOE, J. A. Principles of Irrigation Practice. Macmillan Company, New York. LOUGHRIDGE, R. H. Distribution of Water in the Soil in Furrow Irrigation. Office of Experiment Stations, Bulletin No. 203. CHAPTER III SOIL MOISTURE MOST soils in humid regions, and many in arid regions especially where irrigated, are permanently saturated with water at certain depths, and the surface of the saturated mass is called the " water table " or the surface of " ground water." 1. Free Water. When a soil saturated with water is provided with perfect drainage, a portion of the water will be drawn off by the action of gravity, and replaced by air. This water may be called " Free Water," or " Gravity Water." 2. Capillary Water. The soil thus drained will still remain moist, a considerable quantity of water being held by capillary attraction in the finer pore spaces, and as films on the particles of the soil. This is called ''capillary " water; and varies in percentage with the fineness of the soil, being more abundant in clay and loam than in sandy soils. The space vacated by the gravity water is at once occupied by air, so that with the gravity water withdrawn and the capillary water remaining the soil is well supplied with both air and water, which is a favorable condition for the growth of ordinary plants. The capillary water is gradually taken up by plants or evaporated, and unless a new supply is furnished, the soil becomes what we call " dry," and the plants wilt and die for lack of moisture. 3. Hygroscopic Water. After the soil has been as thor- roughly dried as possible without the application of artificial heat, it still retains some water, called " hygroscopic water " that may be driven off by a protracted application of heat, after which the soil, when exposed to a moist atmosphere, will reabsorb an equal quantity of water and still appear dry, and in fact actually be dry so far as plant needs are concerned. The hygroscopic moisture in soils varies with its texture, from i 16 CAPILLARY MOVEMENT 17 per cent in coarse sand to nearly 10 per cent in clay, and still more when certain salts are present. It is not available for plant consumption and is properly disregarded in considering irriga- tion needs. The soil must receive an appreciable addition of water usually over 50 per cent above its content of hygroscopic water, before any becomes practically available for plant use, and every addition above this point makes it more and more easily available; that is, it is more loosely held by the soil particle, until a plenitude of moisture is reached called the " maximum capillary capacity," after which additional water flows off the soil particles under the action of gravity and drops to lower levels or drier soil, or passes down to the water table, as gravity water. The capacity for holding capillary water varies with the density of the soil, from about 12 per cent for coarse sand to 20 per cent for very heavy clay, averaging about 16 per cent for loam. The amount of capillary water held by the soil particle before it becomes practically available for plant consumption must exceed i per cent for coarse sand, 2 per cent for fine sand, 3 per cent for sandy loam and 4 per cent and over, for heavier loams and clay. Even at these percentages, the water is taken *by plants slowly and with difficulty, and a larger quantity is necessary for the best growing conditions. When the amount of capillary water falls below these quantities, the plant begins to show signs of distress, growth ceases, wilting begins, and permanent injury or death will soon ensue unless water is supplied. The point at which wilting begins in any given soil is called the wilting coefficient of that soil. It is nearly the same for all ordinary crops. 4. Capillary Movement. Capillary water moves in any direc- tion toward drier soil under the action of capillary attraction. At the water table all the pore spaces of the soil are filled with water. Just above this level, the soil is wet to its " capillary capacity," and the remainder of its pore spaces are filled with air. The amount of capillary water held by the soil diminishes from the water table upward at a rate uniform for uniform soil 18 SOIL MOISTURE texture, and approximates zero at a distance above the water table, depending upon the fineness of the soil particles, and varying from about i foot for coarse sand, to 6 feet or over for heavy clay. Its motion is extremely slow in clay, and relatively rapid in coarse-grained soils. Lyon and Fippin have given the rate and extent of capillary movement for the various soils shown in the following table: TABLE II. EXTENT AND RATE OF CAPILLARITY CAPILLARY RISE IN INCHES Kind of Soil 15 i 2 i 3 8 13 19 min. hr. hrs. day days days days days Silt and very fine sand . . 2.7 4-7 7.0 2O. 30.0 45-0 52.0 56.0 Very fine sand 7-6 10. 12.4 21 .0 23.0 26.0 2 7 5 28.5 Fine sand 9.0 9-5 10. ii. 6 13-0 14.3 15-2 16.0 Coarse and medium sand 5-8 6.0 6-3 7-5 9.0 IO.O n-5 12-5 Fine Gravel 4.0 5-0 5-3 6.4 8.0 9.0 IO.O 10.8 Clay will give a greater total rise but at a slower rate than any of the above results. Instances have been recorded where water has risen by capillarity a total distance of 8 feet through heavy clay. Where water is applied in irrigation, the soil in proximity to the water is, of course, immediately saturated, and the gravity portion of the water seeks lower levels, under the influ- ence of both gravity and capillary attraction. This movement is rapid in coarse open soils like sand or gravel, but much slower in loam or clay. The wetted soil retains a sufficient quantity to satisfy its capillary capacity, and all the surplus continues to sink, filling the soil to the capillary capacity as it goes until ground water is reached, when the surplus is consumed in raising the ground-water table or passes away in whatever drainage channels are available. 5. Optimum Water Supply. The ideal quantity of water for most rapid plant growth is that quantity that will just fill the soil to its capillary capacity to the depth occupied or soon to be reached by plant roots, without affording any excess to OPTIMUM WATER SUPPLY 19 escape to the ground water table, or to the soil zone below the reach of crop roots. All water that escapes to the water table and passes off as drainage is usually wasted, carries with it in solution more or less plant food, and may contribute to raise the water table and produce seepage troubles. For these rea- sons it is usually better to stop short of the complete capillary saturation of the soil in the root zone than to risk the loss of water, by excess application. It is generally not possible to attain the ideal, for if the soil be charged to its capillary capac- ity to the bottom of the root zone, and the water table be not reached, the water will continue to descend under the combined action of gravity and capillarity, and thus escape beyond the reach of crop roots and leave the soil in the root zone with less than its full load of capillary water. At the end of each irrigation, the upper zone of the soil is saturated to a considerable depth, and the gravity water in this zone is slowly descending to lower levels. Evaporation from the surface begins almost immediately, and the moisture of the surface soil is soon reduced by the combined process to a point below capillary saturation, and shortly after, an upward move- ment begins of capillary water to supply the losses from evap- oration from the surface. The zone of saturation is thus slowly sinking in obedience to the force of gravity, and is also being depleted by capillary action both upward and downward, and unless an excess has been applied, the store of free or gravity water is soon dissipated and distributed through the soil as capillary water. Thus, after each irrigation, a condition is soon reached, in which a narrow zone a short distance below the surface is in a state of capillary saturation, and the per- centage of moisture diminishes both upward and downward, at a nearly uniform rate. If at this time the moisture at the lower limit of the root zone is just a little above the wilting coefficient, the water has been economically applied, and none wasted. The water content of the soil decreases gradually from this point by evaporation from the surface, and by plant con- sumption and transpiration throughout the zone occupied by plant roots. 20 SOIL MOISTURE As the evaporation all occurs from the surface, the general movement of moisture is upward soon after the supply of gravity water is dissipated. The tendency therefore is to accumulate the soluble portions of the soil at or near the sur- face, where the pure water is evaporated and the solids are left behind. It is important that this tendency be combated by retarding evaporation through cultivation. When crops are not cultivated, the evaporation from the surface may be nearly as great as the consumption of moisture by the plants, whereas if the soil is kept pulverized to a considerable depth, the volume of water taken up by the plants is 5 or 6 times as great as that lost by evaporation, which hence becomes almost negligible, and has little tendency to accumulate salts at the surface, and this is overcome by necessary deep plowing. Soil which is as dry as it can be made without artificial processes still contains a considerable amount of hygroscopic moisture adhering to its grain. The percentage by weight which this bears to the weight of the soil is called the hygro- scopic coefficient, and this must be increased at least 50 per cent before it becomes available for sustaining plant life. 6. Wilting Coefficient. The point at which vegetation wilts and dies for lack of moisture is called the wilting coefficient. The water available for plant consumption, therefore, is that portion of the capillary water which it contains in excess of the wilting coefficient. The water content of the soil upon which a growing crop depends must never fall as low as the wilting coefficient, nor be increased above the capillary capacity, except temporarily. 7. Water Required. The amount of water required for a single irrigation depends on the character of the soil, the depth to which it is desired to moisten it, and the amount of moisture it already contains. Prof. L. J. Briggs, Prof. Loughridge, Prof. Hilgard and others have made a large number of observations upon the hygroscopic and wilting coefficients of various soils, and a large number of comparisons of these are condensed in the following table, which gives also the capillary capacity, the available WATER REQUIRED 21 capacity or difference between the capillary capacity and wilting point, and the total capacity for moisture for various soils: TABLE III. PERCENTAGE BY WEIGHT OF MOISTURE CAPACITIES FOR VARIOUS SOILS Type of Soil Hygro- scopic Coeffi- cient Wilting Coeffi- cient Capillary Capacity Available Capacity Total Capacity Coarse sand I .0 1 .5 13 II .5 33 Fine sand 2 . I 7 . 2 14 10. 7 24 Sandy loam Fine sandy loam . 4-7 6.9 7.0 10.8 15 16 8.0 5 2 35 37 Loam I 124 18 4.6 38 Clay*loam Clay n. 8 13.2 15-0 16.5 iQ 20 4.0 3-5 40 42 It will be seen from the above that if a loam of the type above assumed is dried to the wilting point, it still contains 13.4 per cent of water by weight, and can retain by capillarity 4.6 per cent additional water, or about 4 pounds per cubic foot, and it would require about J cubic foot of water to fill a square foot of area to a depth of 4.2 feet to its full capillary capacity. Such an application to very dry loam of the type assumed would constitute a good irrigation. That is it would require 3 inches in depth applied to the land. Similarly, a sandy loam of the type given in the table would require under the same circumstances about 75 per cent more water, or a depth of about 5J inches; coarse sand would require about 7^ inches in depth, and clay would require a little less than 3 inches. Irrigation should always be applied before the soil moisture reaches the wilting point throughout the root zone, otherwise the plants will be severely injured or killed. CHAPTER IV PLANT FOOD THE essential mineral elements of plant food derived from the soil are calcium, potassium, phosphorus, magnesium, iron and sulphur. Other elements, equally important, are derived mainly from air, and water, or from decayed vegetation. These are nitrogen, oxygen, hydrogen and carbon. Magnesium, iron and sulphur are used in very small amounts, and occur in all natural soils in sufficient quantity to answer ordinary plant needs, but most soils require for best results the occasional artificial addition of some of the other elements. Nearly all the hydrogen, and most of the oxygen consumed by plants is furnished in the form of water (H^O). i. Functions of Water in Plant Growth. Water is the most abundant constituent of the body of the live plant, and thus forms a most important element of the plant's food. In addi- tion to this, it is the necessary vehicle for carrying in solution all the other elements of plant food that are absorbed from the soil by plant roots, and conveyed in solution to the various parts of the plant for assimilation. Hence the vital importance to the plant of having a constant and sufficient supply of water. When the water has performed its function as a vehicle the portion not required for food by the plant is transpired by the leaves, and absorbed by the atmosphere in the form of watery vapor. The amount of water consumed by the plant in forming a unit quantity of tissue varies widely with the character of the plant and the available plant food. The results of experi- ments to determine this are found in the following table: 22 MINERAL FOODS 23 TABLE IV. POUNDS OF WATER CONSUMED BY VARIOUS CROPS IN THE PRODUCTION OF ONE POUND OF DRY MATTER Lawes and Gilbert Hellreigel Wollny King Widtsoe Average Wheat 225 359 1006 530 Oats 402 665 CC7 541 Barley 262 3 IO 774 393 . . . 435 Peas 23S 2Q2 479 447 363 Red Clover 2 49 33 453 344 Corn 233 272 387 297 Potatoes 423 1440 93i Beans 214 262 . . . . . . . . . 238 Buckwheat 37i 664 5i8 Sugar Beets 662 662 Alfalfa 97 97 Average 530 2. Mineral Foods. Since the plant can take its food only in liquid form it follows that soil particles to be available for plant food must be soluble in water. All the chemical elements are to some extent soluble in water, but they differ widely in the rapidity of solution, and the amount that can be dissolved by a given quantity of water. All nitrates and most combinations of sodium and potassium are readily soluble in water in considerable quantities, but even these are strictly limited in the amount that can be dissolved in a given volume of water, which is said to be " saturated " when it can dissolve no more of a given solid. When such a saturation solution is subjected to evaporation, the water passes into the atmosphere, and leaves a portion of the dis- solved mineral in excess of that which the remaining water can hold in solution, which is accordingly deposited as solid crystals of the mineral with which the water is saturated. At the same time other minerals may be present in quantities below the point of saturation, and these may remain in solution. In general, nitrates dissolve in water rapidly and in consider- able quantities. Sulphates, phosphates and carbonates are soluble in less degree, and silicates still less so, except the 24 PLANT FOOD alkaline salts, most of which are readily soluble. Nitrogen is a rather inert element, having little chemical affinity for any other elements. Hence in nature it exists almost entirely as a free gas in the atmosphere, uncombined with any element. Pure air is composed of a mechanical mixture of oxygen and nitrogen uncombined chemically, in the proportion of 4 parts of nitrogen to i of oxygen by weight. The oxygen is vitally necessary to animal existence, while the free nitrogen, though harmless, is unnecessary except as a dilutant. This inert nitrogen, however, when combined with other elements, forms some of the most useful and necessary foods, both plant and animal, and in still other combinations forms some of the most powerful acids and explosives. It has a constant tendency to revert back to its atmospheric state, and hence the stores of natural combined nitrogen are rare and limited. Their pro- portion of the solid earth is negligible, and the existing stores of nitrates are valuable as fertilizers and for other uses. When natural rocks are disintegrated and broken up into fragments and soil particles, the more soluble portions are gradually dissolved by the rains and pass off with the drainage water. It thus occurs that the more soluble salts of sodium and potassium are carried to the ocean and held there in solu- tion in large quantities, while the silicates and other relatively insoluble rock particles remain as soil. The sulphates, phos- phates and carbonates of the non-alkaline metals being less soluble than the alkaline salts, pass away less rapidly, but being more soluble than the silicates of the same metals, have a constant tendency to leach out and leave the silica and silicates in the form of sand and clay to form the main constituents of the soil. The tendency is thus in humid regions except in swamps, gradually to deprive the natural soils of their mineral plant food, a tendency existing in far less degree in arid regions. Hence the soils of arid regions are much richer in mineral plant food than most of those in humid regions, but the latter are generally better supplied with nitrates, contained in humus or vegetable mold. FERTILIZING EFFECTS OF SEDIMENTS 25 3. Fertilizing Effects of Sediments. The value of silt-bearing water as a fertilizer is well known. In the valley of the Moselle, France, on land barren without 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 several 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. In the Nile Valley the turbid waters of the White Nile are recognized as far more valuable than the clear waters of the Blue Nile, on account of the fertility carried by the mud. The fertilizing value of the silts of some of our southwestern streams is shown by the following table, which compares their fertilizing contents with the food requirements of a ton of alfalfa: TABLE V. FERTILIZING VALUE OF SEDIMENT PLANT FOOD PER ACRE FOOT OF WATER River Date Phosphoric Potash Nitrogen Authority Acid Ibs. Ibs. Ibs. Rio Grande 1893-94 31-4 325-5 24.40 Goss Salt River 1899-1900 10-5 26.5 9.00 Forbes Colorado, minimum 1900-1901 2.26 l6. 3 1.03 Forbes Colorado, maximum .... 1900-1901 43-56 444.6 69.70 Forbes i ton alfalfa 16.7 33-0 42.00 Goss REFERENCES FOR CHAPTERS III AND IV BRIGGS, L. J. and SCHANTZ, H. L. Wilting Coefficient for Different Plants. Bulletin No. 230. Bureau of Plant Industry, Washington. WIDTSOE, J. A. Storage of Winter Precipitation in Soils. Utah Exp. Sta., Bulletin No. 104. ETCHEVERRY, B. A. Use of Irrigation Water. McGraw-Hill Book Company New York. 26 PLANT FOOD FORTIER, SAMUEL. Evaporation Losses in Irrigation and Water Requirements of Crops. Bulletin No. 177. Office of Experiment Stations, Washington. LOUGHRIDGE, R. H. Moisture in California Soils. Report of Agricultural Experiment Station, University of California, 1897-98. WIDTSOE, J. A. and MCLAUGHLIN, W. W. Movement of Water in Irrigated Soils. Utah Experiment Station. Bulletin No. 115. LYON & FIPPIN. Soils. Macmillan Company, New York. BARK, DON H. Alfalfa Growing. Address before Western Canada Irrigation Association. Bassano, Alberta, November, 1915. Goss, ARTHUR. Principles of Water Analysis as Applied to New Mexico Waters. Bulletin No. 34. New Mexico Agr. Exp. Station. FORBES, R. H. The River Irrigating Waters of Arizona. Bulletin No. 44. University of Arizona Agricultural Exp. Station, Tucson, Arizona. FOLLETT, W. W. Silt in the Rio Grande. International Boundary Commission, Dept. of State. SWINGLE, Z. T. Bulletin No. 53. Bureau of Plant Industry. HILGARD, E. W. Distribution of Salts in Alkali Soils. Bulletin No. 108. Univ. of Cal. WILSON, H. M. Irrigation in India. Part II of i2th Annual Report, U. S. Geo- logical Survey. ETCHEVERRY, B. A. Irrigation Practice and Engineering. McGraw-Hill Book Company, N. Y, CHAPTER V WATER SUPPLY ALL the water used by plants is precipitated from the atmosphere as rain, snow or dew, which in humid regions are sufficiently regular and abundant for crop production, but in arid regions are sufficient only for the precarious sustenance of a limited variety of grasses, shrubs and trees which have the property of becoming dormant without dying in times of drouth, and reviving and growing when sufficient moisture comes. The groups and ranges of mountains in arid regions by reason of their superior elevation have greater precipitation than the plains and valleys, and thus become the sources of such streams as occur, and the snows of winter falling on those mountains serve as storage reservoirs, to hold the moisture until the warm days of spring and summer melt the snow and swell the streams at the time their waters are needed for irriga- tion upon the valleys which they traverse. These streams constitute the principal source of water used in irrigation. i. Causes of Rainfall. Although meteorology is a rather elusive science, much progress has been made in the study of phenomena and some general laws regarding the cause and distribution of rainfall have been evolved. The capacity of air for holding water in the form of an invisible gas is a function of its temperature. Warm air can retain a large amount of moisture without any tendency of the moisture to condense; but if the air be cooled sufficiently a point will be reached where the water begins to condense, and separate as particles of vapor or cloud. At this point the air is said to be. saturated, and the relative humidity is 100 per cent. This critical temperature is called the dew point. The particles of vapor are very minute, and they may float about 27 28 WATER SUPPLY as clouds, but if formed rapidly they usually coalesce into large drops and fall as rain. The principal causes that contribute to abundant rainfall are: 1. Proximity to the ocean or other large body of water. 2. Mountain ranges, especially if their trend is at right angles to the direction of moisture-laden winds. 3. Location on or near the track of cyclonic storms. The North Pacific Coast combines all three tendencies, resulting in a heavy precipitation. The first condition is not always sufficient, as many islands in the Pacific Ocean are arid, as is the Pacific Coast of Southern California, Mexico and parts of South America. The greatest rainfall usually occurs in belts where moist winds from large bodies of water are forced to rise and pass over mountains which forcibly cool them and condense their moisture. Such conditions are most pronounced where a high mountain range parallels an adjacent sea coast and is at right angles to the direction of the prevailing winds. As the water- laden air rises, the overlying atmosphere becomes less, thus decreasing pressure, and allowing the elastic air to expand, which in turn causes rapid cooling, condensation and precipita- tion of the moisture. If the mountain range is high and exten- sive, the process is proportionately complete, and as the winds descend the leeward slope and are again compressed their moisture-absorbing qualities increase and they produce arid conditions unless the process is repeated by passage over a still higher range. This process is well illustrated on our own Pacific Coast, where the moist winds from the great ocean are inter- cepted by the Coast Range, and a large part of their moisture thereby precipitated. They pass over the Central Valley which is thus left with less than half the quantity of rainfall that falls on the Coast Range. Further inland the winds ascend the high Sierras and leave on their summits about as much moisture as precipitated on the Coast Range. Thus depleted the winds again descend to the plains of the Interior, as an CAUSES OF RAINFALL 29 O in o O O o CN m m m o o 30 WATER SUPPLY .2 CAUSES OF RAINFALL 31 m o "i O 32 WATER SUPPLY arid atmosphere, and the region is much drier than similar altitudes west of the mountains. Whatever the direction of the winds the general law of con- densation, due to dynamic cooling, usually causes an increase of precipitation with increase of altitude provided all other conditions are similar. The following table from Prof. D. W. Mead illustrates this law as manifested in the Vogesen Moun- tains and also shows the erratic variations: TABLE VI. RAINFALL IN THE VOGESEN MOUNTAINS Station Altitude, Feet Rainfall, Inches Increase per 100 ft. Altitudes Seunheirn QOO 32 28 Thann . IIOO ^8 IQ 3 inches Weller I26o ^ QO ii " St. Amarin I32O CTQ 06 5 2 " \Vesserling I4.OO 64 18 6 " Odern ISIO 7C 08 10 " Wildenstein 1870 QO 21 6 " ' Mean 6.9 inches This rule, however, must be accepted with great caution, as there are numerous exceptions hard to explain, besides the manifold differences traceable to topographic conditions. 2. Types of Rainfall. On the Pacific Coast of North America the precipitation is greatest in winter and least in summer, there being little or no rain from May to September. This rule is reversed on the Great Plains, where June is the month of greatest rainfall. A modification of the latter type prevails in Arizona and New Mexico, where the greatest rainfall is in July and August. Pacific Type. On the Pacific Slope there is a distinct division into the wet and dry seasons, the wet season being the winter and the dry the summer. In the northern part of this belt, on the coast of Washington, Oregon and Northern Cali- fornia, the wet season is long and the precipitation heavy, averaging 70 inches or more per annum, and the dry season TYPES OF RAINFALL 33 though shorter, is nearly or quite rainless. Passing southward the precipitation becomes gradually less, the rainy season shorter and the dry season longer, until at the Southern boundary of SIERRA NEVADA 61.18 in 33.06 in PACIFIC OCEAN SACRAMENTO VALLEY 22 77 in " 23<81 in .18 .41 in. ,10.78 in. .10.60 in I I K* ISan FrancieccJF'irficld |FolRonif%^ | Jaracm Z.//.|j 50 ' J K ' Sacramento | ?1 > jgoj^X Cisco. 47.71 in. Sea Level 25 miles 50 100 125 150 175 ; :I 200 225 250 FIG. 4. Diagram Showing Effect of Topography on Rainfall in California and Nevada. After Hamlin. FIG. 5. Discharge of San Joaquin River at Herndon, California, 1900. California the annual precipitation averages less than 10 inches, and the climate is distinctly arid, while still retaining the type form of long dry summers, and short and relatively wet winters. 34 WATER SUPPLY Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 10 20 10 20 10 20 10 20 10 20 I 10 20 I 10 20 10 20 10 20 10 20 10 20 10 20 FIG. 6. Discharge of Neosho River near lola, Kansas, 1900. Sec.-ft 16,000 FIG. 7. Discharge of Boise River at Boise, Idaho, 1899. TYPES OF RAINFALL 35 Rocky Mountain Type. A contrasted type of precipitation is less distinctly marked, but prevails with some variations over most of the arid region east of the Cascade and Sierra Nevada Mountain Ranges. Those mountains intercept the FIG. 8. Discharge of Salt River at McDowell, Arizona, 1899. 20,000 FIG. 9. Discharge of Green River at Green River, Wyoming, 1899. waterladen winds from the Pacific Ocean, and rob them of most of their moisture during the winter when the temperature is low enough to condense the vapors, but in late summer, those winds pass over the heated valleys and mountain ranges and carry their moisture further eastward, where the meteoric 36 WATER SUPPLY STREAM FLOW 37 fluctuations cause many local showers and thunder storms, and produce a pseudo-rainy season in the Rocky Mountain Region in the months of May and June, while the winters are drier than those of the Sierra Nevada Range. The precipitation in winter usually occurs in the form of snow except in the plains and valleys of the south and near the Pacific Coast, where winter rains occur. The diagram, Fig. 10, after Prof. A. J. Henry, shows several types of western rainfall, contrasted with various eastern types. In general the heaviest precipitation is in the mountains, which in winter is mainly in the form of snow. Notable excep- tions occur, however, and give rise to contrasting types of stream flow. 3. Stream Flow. Where the streams are mainly fed by snow, they have a comparatively regular habit. The first warm days of spring melt the snow on the plains, and the advancing season melts first the snow in the foothills aiid on sunny moun- tain slopes, and as summer heat increases the melting increases in rapidity and extends to higher altitudes and to more shady slopes. Thus the streams begin to rise in early spring about the time of seeding in the lower valleys, and continue to rise as heat increases, culminating usually in June on most American streams, declining as the reserve of snow diminishes, and reach- ing extreme low water in autumn or winter. This process has temporary variations due to occasional showers of rain, and to variations of temperature affecting the melting of snow, which is accelerated by bright warm weather, and checked by cloudy days. There is also a wide variation in the snowfall from year to year, profoundly affecting the water supply. A year of scanty snowfall not only furnishes a scanty supply of water, but the shortage is likely to be concentrated at the latter end of the flood season. That is, a scanty snow- fall may furnish nearly as much water early in the season as a year of abundance, but the small quantity of snow is sooner exhausted, and the low-water stage arrives earlier in the season. Where snowfall plays a small part or no part at all in the flow of streams, which are mainly supplied by rains as some of 38 WATER S&PPLY the small streams of the south and southwest, the regimen of the streams is far less regular than that of those dependent on melting snow. Such streams constitute a second type having a wide variety of characteristics and far less susceptible of approximate prediction. The runoff fluctuates more, and is characterized by high and low periods succeeding one another in quick succession. For these reasons, a much larger storage capacity in proportion to the total normal water supply is required on such streams than on streams of the first type. Streams of the first class, which depend upon melting snows for their main supply, vary in habit, but to a less degree than others. In general, since the flood season occurs entirely in the season of irrigation, it is very favorable to agricultural use, and a large proportion can be thus utilized without artificial regulation. Examination of a large number of instances shows the availability of from 40 to 60 per cent of the total supply in normal years without storage, and that the full supply can be utilized by a capacity for storage of about 40 to 60 per cent of the total volume. This storage would be supplied from the winter flow, and from the excess supply during the flood season, usually May and June. In planning the full utilization of a water supply, the close study of stream flow records necessary will show that there is a large variation in the total supply from year to year, in the low- water discharge, and also in the maximum flood wave that must be reckoned with. Moreover, these quantities bear only a very casual and uncertain relation to each other. For these reasons, it is important that as long a record of stream flow as possible be secured before final determination is made of the possibilities of irrigation. It will generally be found that the extreme low-water periods and the extreme flood waves occur only at long intervals, and it is usually unwise to limit development to the extent of fur- nishing a full normal supply to the lands served in the rare years of extreme low water, but rather to provide a full supply during most years, and in the exceptional years of low water, occurring only at long intervals, be content with 60 or 70 per STREAM FLOW 39 cent of a full supply for a brief period. By more careful use and better cultivation results can be obtained which will approximate the normal, while the total development from the stream will be much greater than if such limits were not allowed. Where an enterprise depends largely on a stored water supply, a threatened shortage is foreshadowed by a shortage in the reservoir, and this, in conjunction with other available indi- cations, serves as a warning of impending scarcity, and farm operations can be modified accordingly. For this reason it is admissible to tolerate a somewhat greater shortage in low years under a stored supply than if no storage is connected with the enterprise. For the same reason, if the conditions are such that the storage to be reasonably expected comes before the beginning of the irrigation season in which it is to be used, a somewhat greater shortage can be tolerated than if dependence is placed upon the surplus of May and June, which cannot be certainly known before the various farm enterprises for the summer are well under way. But even in this case there will be 30 to 60 days notice of a shortage, which is sufficient to avoid much wasted labor, and a few fields left fallow on such occasions are not a serious loss. In most irrigation enterprises the quantity, dependability, and manner of occurrence of the water supply is of first importance. This is sometimes obtained from wells either by pumping or by artesian flow, which are treated elsewhere. The great majority of irrigation systems obtain their supply from natural streams, supplemented in some cases by reservoirs. The stream or streams to be used should be carefully meas- ured at each point of diversion and at each proposed reservoir site. Measurements of many streams of the West have been made and published by the U. S. Geological Survey, and by some of the State Engineers, but often these are lacking or must be supplemented by stations located with special reference to the plans of storage and diversion under study. These measurements to be a safe guide must extend over 40 WATER SUPPLY several years, the more the better, and allowance must be made for somewhat greater extremes than those shown by the records, as it is highly improbable that any existing records show the greatest extremes that ever have occurred or ever can occur. The shorter the record the greater allowance must be made for this purpose. The misleading nature of a short record is shown by the experience with the Conconully reservoir in Northern Wash- ington, where a record of five years indicated a minimum annual supply of 29,000 acre-feet, which was followed by seven years in which the maximum was 24,700 and in which there were two years in succession of 19,220 and 15,860 acre-feet respectively. 4. Laws of Runoff. Where it is necessary to study the water supply of a given stream in the absence of actual meas- urements or with a very short record, recourse is sometimes had to formulae for computing runoff from data regarding rain- fall, evaporation, etc., which have been published from time to time. Great caution should be exercised in employing any such formulae, as the working data for this use is generally inaccurate, and it is impossible to allow properly for the variations from the complicated conditions upon which such formulae are based. It is necessary to especially emphasize this caution, as the formulae or rules referred to are sometimes promulgated with a confidence that has no adequate foundation. The runoff depends not only upon the rainfall and the drain- age area, but also upon a multitude of other conditions many of which are variable, and none of which can be accurately deter- mined within reasonable time and cost. The chief elements affecting the runoff are the following: a. Drainage area tributary to the stream above the point of diversion. This can be determined with practical exactness wherever the topographic divide is definite. b. The Rainfall. This varies widely in different years, and in corresponding months of different years, and in different parts of the basin in such an erratic manner that it can be only roughly approximated in a large basin by ordinary feasible methods. It is seldom that in a new country a record suffi- LAWS OF RUNOFF 41 ciently detailed and reliable for use in a computation of runoff can be had. c. The Character of Rainfall. A slow drizzling rain is more apt to be absorbed and later to evaporate than a driving storm which runs off quickly before absorption. This factor varies with every storm, without law, and it is impossible to define the different varieties. The absorption and residual runoff also varies with different conditions of moisture in- the soil. When rain falls on a dry baked surface it is not readily absorbed, and largely runs off. The same storm falling on the same sur- face, moderately moist, is more easily absorbed and the runoff is less. If the soil becomes saturated, however, the absorption ceases, and the rain runs off. d. Evaporation. This differs widely from day to day and from year to year with weather conditions, and especially with presence or absence of moisture to evaporate, and the varying relation of that moisture to the atmosphere. e. Topography. Steep slopes increase runoff, while gentle slopes encourage absorption and evaporation. /. Soil. Bare rock or clay or a covering of thin soil over rock or clay is favorable to heavy runoff, while a deep sandy soil favors absorption and subsequent evaporation. A given basin may present a great variety of soil conditions. g. Geologic structure affects total runoff by sometimes carrying absorbed water under ground to adjacent drainage basins. This influence is sometimes very important. h. Vegetation. Other things being equal vegetation retards runoff and subsequent evaporation. It also transpires a large amount of water through its leaves, and this varies widely with the character and density of the vegetation, and with the weather. The impracticability of expressing accurate mathematical relations for so many and such erratic and indeterminate fac- tors is obvious; and the attempt to apply such relations to a different basin with different conditions borders on the absurd. A knowledge of the area of the drainage basin from which the water supply is to be drawn, and of the rainfall at various 42 WATER SUPPLY . i ^OOO^ O HO O cst^-O M Oooio i/- PO '0 10 o J- Q (N 0) 00 ^ H ! H 3 H M CO -^J-M ; 10 10 10 VO M w S ^ Qs CN M M UO CS M (N M C/j < u M 6 SsS c sl N >0 cs r? 00 "*" 3 8 ^ Q | cT i-T 5- M -I S w 6 . 5 8 g g g s | o o o o o o ^^ o ^ Tj- O t^- 10 O OO 10 10 PO 10 "0 PO CC ro 00 O O rj- M |l M M M M II" I" 1 >S ^ 5 o Ov g ^5 1 o ro 8 1 : X sis O W M PO t^ ^- H ^ ^ : rt 0- M c c 5 . rt c o tc -^ 5 O QJ o; K HH ~ ^ ^^ ^ 44 WATER SUPPLY RUNOFF . fa cj ^ 66 6 6 6 6 6 6 H 4 6 6 6 M ANNUAL c x . oj +-> ir. g. C O-^t- -Ol-lOM(NOOOCl-HI-l(NOCO M M C^ \O t-< -M 8888888888188111s s i ^Jo 8 ^ ^ U SUBSURFACE WATER SOURCES 45 points in the basin extending over many years may, if intel- ligently 'studied, and interpreted by some actual measurements of the stream, sheds some light on the probable runoff, but can- not take the place of actual records of stream flow extending over a series of years. A long record of stream flow of undoubted accuracy on a stream draining a basin adjoining the one in question, and similar in area, altitude and topography, may be available and of great value as indicating probabilities, but even this should be used with caution, and can by no means take the place of actual measurements of the stream in question. Great caution should also be exercised in considering the reports of old inhabitants regarding the annual occurrence of great flood discharges, as these are likely to be exaggerated both in magnitude and frequency. Such floods make deep impressions on the average mind, while the years that glide by without them attract less attention, and are easily forgotten. 5. Subsurface Water Sources. A part of the water which falls on the high regions soaks into the soil and entering the pores and seams of the rocks passes slowly along under ground to the lower regions, where some of it reappears as springs and some is recovered by means of wells. Where the water-bearing stratum is overlain by tight material of great thickness, preventing the escape of the water to the surface, the pressure of the water from the hills upon that in the lower parts of the stratum may become considerable, and by piercing the overlying impervious strata by drilling machinery an outlet is furnished for the confined water and under the influence of the accumulated pressure it rises to the surface, forming an artesian well, which sometimes discharges its water with great force, depending upon the pressure.. The great majority of wells, however, do not flow at the surface, but to be used must be raised by pumping. Irrigation by means of wells is well adapted to individual effort, where conditions are favorable, as the construction of a well is often within the means of an individual, and the area it will irrigate no greater than he can control. The aggregate 46 WATER SUPPLY area thus irrigated is very large in India, and has possibilities of great development in this country, although now relatively small as compared with the acreage irrigated from streams and reservoirs. The water which enters the earth by percolation either from rain or from canals, reservoirs, or irrigation finds its way through the soil to some lower level where favorable geologic structure enables it to again reach the surface, or 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. Its total amount is enormous. a. Rate of Percolation. This ground water is exceedingly slow of motion, both in porous sands and in 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 subject are those of Mr. Allen Hazen, which for closely packed sand saturated with water are expressed in the formula 60 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; / is the temperature (Fahr.). The formula can be used only for sands with coefficients below five 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- SUBSURFACE WATER SOURCES 47 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 per cent. In the above the effective size is the size of grain such that 10 per cent by weight of the particles are smaller than this. The uniformity coefficient is the ratio of the size of grain which has 60 per cent of the sample finer than itself to the size of which has 10 per cent 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. At Agua Fria, Arizona, the measured rate of flow of ground water in creek gravels having 28 per cent voids was 4 feet a day. A thin film of water is held on each particle with extreme tenacity by a force called, " surface tension," and where the particles are fine the force of capillarity is also strong. In addition to this, the spaces between the particles a^e so narrow and tortuous that water cannot move through them except with great friction and extreme slowness. Experiments with the " permeable " materials of the North Dike at Wachusetts Reservoir gave the following rates of percolation through a cross section of 1000 square feet, with a water slope of 10 per cent: TABLE VIII. PERMEABILITY OF SOILS Material Gallons Ratios I. Soil . 51 I 2. Very fine sand 3 Fine sand 720 9,OOO 14 176 4 Medium sand 4OO,OOO 784 < Coarse sand 2,2OO,OOO 4,353 48 WATER SUPPLY The experiments of Slichter on various soils, upon the veloc- ity of water at a temperature of 50 degrees, flowing upon a gradient of 100 feet per mile, gave results shown in the following table, compiled by Fortier: TABLE IX. VELOCITY OF PERCOLATION Kind of Soil Diam. Grains m.m. VELOCITY Ft. per Day Mi. per Yr. Silt O.OI 0.04 0.05 0.07 O. IO 0-15 0.25 o-35 0.50 0.65 0.80 I .00 3.00 5.00 0.004 0.059 0.092 O.lSl 0.369 0.832 2.305 4.520 9.224 15-57 23.62 36.90 332.10 1067.00 0.0003 0.0041 0.0064 0.0125 0.0255 0-0575 0.1594 0-3125 0.6377 1.077 I-633 2.551 22.960 63.770 Very fine sand Fine sand Medium sand Coarse sand Fine gravel From the above it will readily be seen that unless a well can be made to tap an extensive bed of coarse material, no large yield of water can be obtained from it. 7. Artesian Wells. According to the common use of the term, an artesian well is one from which water flows at or above the surface of the ground. A broader meaning is any well in which the water rises considerably above the stratum to which it was confined before being relieved by the construction of the well. The former is the more generally accepted as well as the more practical definition. In order that water may rise in a well to the ground surface, it must be under pressure, and so confined between relatively impervious deposits, that it can more easily escape through the well than elsewhere. ARTESIAN WELLS 49 if a stratum of sand, sandstone, gravel, or other porous material is confined between relatively impervious strata of rock or clay, and is so inclined that one part of the open material is exposed to rain, and another part is depressed in the form of a basin, the water entering at the upper edge will percolate down the slope of stratification and accumulate in the basin, and place the water in the lower levels under such pressure as corresponds to the hydrostatic head of the water above it. If now the overlying clay be perforated by a boring, the water will rise in the bored well to the same height as the source from which the pressure is derived, and if this is sufficient to force the water to the surface, we have a flowing well. The accompanying diagram, Fig. u, illustrates the geo- logical conditions of an artesian basin. FIG. ii. Ideal Section Illustrating Condition of Artesian Wells. If the layer of sand be penetrated by a well drilled at D, the water will rise to a height regulated by the pressure of the water in the sand above the locality where the well reaches it. The source of the water that rises in artesian wells is mainly the precipitation on the edges of the pervious beds where they come to the surface. In some instances the porous beds are charged in this way at their outcrops, hundreds of miles from where the water is liberated by drilling wells. The height to which water rises in an artesian well, or, the height to which it would rise in a tube open at the top, if prop- erly attached to the well, is termed the " artesian head." This is illustrated in the waterworks of towns, where the water rises in the distributing pipes to the same level as the surface of the water in the reservoir from which it is drawn. Cases also occur of what are termed incomplete artesian basins, where an inclined bed of open material as sand or gravel thins out at its lower edge, and the impervious strata 50 WATER SUPPLY above and below approach each other. This is illustrated in Fig. 12. It will be noted that stratification and porosity are two neces- sary conditions and therefore massive, unstratified, crystalline rocks such as granite, schists quartzites and diorites, which are not porous, and are never underlain with porous stratified rocks, do not present favorable conditions for artesian wells. Where such rocks are exposed or occur near the surface of the ground, the prospects for artesian water are poor. The original bedding of such rocks has been generally obliterated by the changes they have undergone, and there is no succession of pervious and impervious layers. FIG. 12. Ideal Section Illustrating Thinning Out of Water-bearing Stratum. The condition of a flowing well depends on whether the pressure is sufficiently great to force the water above the sur- face. Frequently the water will reach within but a few feet of the surface, when an ordinary 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 pressure to considerable heights. In the San Gabriel and San Bernardino valleys in Southern California and many other regions, it has been found that after a 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. a. Examples of Artesian Wells. Some great wells have been sunk in different parts of the world. The celebrated Grin- nell 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 been bored in the neighborhood of Wheeling, West Virginia, ARTESIAN WELLS 51 to the great depth of 4500 feet, but is dry. At Sperenberg, 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 California and in the upper San Joaquin valley in the neighbor- hood of Bakersfield are some extensive artesian areas, and great artesian basins are found in the neighborhood of Waco, Texas, Denver, Colorado, and the James River valley and the neighborhood of Huron in the Dakotas. b. Capacity of Artesian Wells. The capacities of flowing wells are relatively small as compared with the volumes of water required in irrigation. Of the thousands of wells reported from the arid region comparatively few are of sufficient capacity for use in irrigation. The great majority 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 small 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. c. Storage of Artesian Water. An artesian well for irrigation 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 52 WATER SUPPLY storage reservoir of greater or less dimensions. In the case, how- ever, of a well which discharges about i second-foot, or enough to irrigate 100 acres from unstored flow, such a well may be made capable of irrigating several times this area if the water flowing at other times than the irrigating periods can be stored. Small reservoirs, sufficiently large to retain only enough water to produce 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. d. Size of Well. The yield of a well does not depend entirely upon its size. A 6-inch well will not necessarily discharge more water than 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 experience may show that it is not desirable to insert perforated ARTESIAN WELLS 53 pipe, but to let whatever comes to the well be discharged and collected in the storage reservoir. e. Manner of Having Wells Drilled. There are many respon- sible 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 of drilling 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. /. 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 rotar^y rigs which are adopted by different well-boring firms. The latter are dependent upon a rotary motion given to a piston-rod working by hydraulic power and turning a tubing with cutting edge. In hydraulic jetting machines, which can be used cheaply only in 54 WATER SUPPLY 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, 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 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. 13), and also jetting and hydraulic rotary rigs. These can frequently be purchased outright at prices which will render them cheaper than any other method of having wells drilled. g. 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 ARTESIAN WELLS 55 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 3 to 5 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 FIG. 13. Portable Artesian-well Drilling Rig. 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 56 WATER SUPPLY 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 " 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 hole 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 repeated if necessary to clear the hole before drilling is again ARTESIAN WELLS 57 resumed. The rate of drilling depends partly 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 with a sharpened steel shoe. The remainder of the casing above is of No. 12 sheet steel in lengths of only 2 feet, each following section being smaller than the last so as snugly to telescope for i 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. h. Capacity of Common Wells. The supplying capacity of common wells is frequently increased considerably by irriga- tion. 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 depends on the degree of fineness of the water-bearing stratum, 58 WATER SUPPLY 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 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., 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. 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 practiced only in a large way and irrigators 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, chiefly by windmills, and by mechanical lifts worked by horse-power, and similar to the Persian 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 1 20,000 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 from 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 TUNNELING FOR WATER 59 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. 8. Tunneling 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 pumped 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 extensive developments of water from subsurface sources yet recorded. One bed of gravel in a stream valley having an area of 1 200 acres absorbs practically all the drainage of 300 square miles. Into these gravels were sunk 91 wells which yield 36 acre-feet of water per day. Another similar bed has been developed by drifting over 14,000 feet of tunnel 5 feet 6 inches X 5 feet 6 inches with nearly as great a length of smaller branch tunnel. Into this drain several hundred driven wells (Fig. 14) which yield over 45 acre-feet of water per iay. a. 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 60 WATER SUPPLY 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 FIG. 14. Subterranean Water Tunnel and Feed- wells: California. inches at the top, placed 4 feet apart across stream, and planked on both faces with interstices of 3 inches on the upper face. The water caught in this cribwork was to be pumped to the surface. 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. 15) are 30 inches square, and about a mile of these have been built running up the bed of the OTHER SUBSURFACE WATER SOURCES 61 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. 9. Other Subsurface Water Sources. Earth waters may be gathered for irrigation by other means than springs, common or artesian wells, or tunnels. 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 FIG. 15. Gathering-cribs, Citizens' Water Co., Denver. bringing water to the surface. 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 Hke drainage ditches, receive a considerable supply of water and lead it off to the lands. 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." 10. Character of Water. Practically all waters found in nature contain some dissolved mineral matter. Spring and 62 WATER SUPPLY well waters usually contain more than surface storm waters, and those of the arid region more than those of humid regions This follows from the fact that the soils of arid regions contain more soluble salts than those of more humid climes, because the latter have generally been more thoroughly leached. Cases are numerous -where small streams fed by mineral springs carry injurious salts in such quantity as to be unfit for irrigation, and to seriously impair the quality of rivers into which they flow. The amount of mineral which water may carry and still be suitable for plant consumption depends of course on the character of the salt, and in general the salts of sodium are most to be feared, in the order of carbonate, chloride and sulphate. 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 he says sometimes 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 ditching 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. Under average conditions, however, where the total soluble salts exceed 300 parts in 100,000, water is objectionable for irrigating most crops, and if carbonates are present a lower limit is imposed, and if they predominate, a still lower limit must be set. CHARACTER OF WATER 63 Waters which contain a moderate amount of salts may be entirely suitable for irrigation on soils having good drainage, but if irrigation with such waters is long continued and no measures are taken to prevent the accumulation of salts in the soil, they may in time impair its fertility. Deep drainage and occasional copious irrigation is the preventive and the remedy. These are treated at greater length in Chapter XII. REFERENCES FOR CHAPTER V ALEXANDER, W. H. Relation of Rainfall to Mountains. Monthly Weather Re- view, 1901, p. 6. MEAD, DANIEL W. Hydrology. Part II. University of Wisconsin. TALBOT, A. N. Rates of Maximum Rainfall. Technograph, 1891-2. HOYT, J. C. Comparison between Rainfall and Runoff in the Northeastern United States. Trans. Am. Soc. C. E., Vol. LIX, New York. Discussions of Above. KUICHLING, EMIL. Unusual Flood Discharges. Trans. Am. Soc. C. E., Vol. LXXVII, p. 650. HENSHAW, LEWIS and MCCAUSLAND. Deschutes River and Its Utilization. W. S. P. 344, U. S. Geological Survey. LARUE, E. C. Colorado River and Its Utilization. W. S. P. 395, U. S. Geo- logical Survey. FOLLENSBEE and DEAN. Water Resources of the Rio Grande Basin. W. S. P. 358, U. S. Geological Survey. HENSHAW and DEAN. Surface Water Supply of Oregon. W. S. P. 370, U. S. Geological Survey. HENRY, A. J. Climatology of the United States. Bulletin Q, U. S. Weather Bureau. ALVORD, J. W. and BURDICK, C. B. Relief from Floods. McGraw-Hill Book Co., New York. HOYT and GROVER. River Discharge. John Wiley & Sons, New York - Report of Special Committee on Flood Prevention. Trans. Am. Soc., C. E., Vol. 81. 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 18, 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. 64 WATER SUPPLY 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. 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 B/KER, M. N. Sewage Disposal in the United States. D. Van Nostrand Co., New York, 1894. 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. HAMLIN, HOMER. Water Resources of the Salmas Valley, California. U. S. Geological Survey Water-Supply Paper No. 89, pp. 41, 42, 1904. McAoiE, A. G. Rainfall of California. California Univ. Pubs., vol. i, No. 4, p. 179, Feb. 19, 1914. CHAPTER VI EVAPORATION ALL the moisture that falls from the heavens must at some previous time have been taken from the earth by some form of evaporation. Conversely, all the moisture absorbed by the atmosphere is destined to fall again in the form of rain, snow, hail, etc. Hence in the long run, taking the earth as a whole, evaporation and precipitation are practically equal. Evapora- tion depends mainly upon the wind movement, and the tem- perature and relative humidity of the atmosphere. It also depends of course upon the presence of moisture to evaporate. An important form of evaporation is the transpiration of moisture from the leaves of plants, in the process of growth. A growing crop usually transpires several times as much moisture as would evaporate from the same soil if no vegetation were present. Hence the importance of destroying weeds which not only consume the moisture but the plant food needed by the crop. The evaporation from the surface of the earth varies widely, but the precipitation varies still more widely. In a region of prevalent fogs, evaporation is low, being zero during a fog, which may in fact precipitate some moisture. Where the atmosphere is very warm and dry the potential evaporation is correspondingly high. In a hot arid region, such as Southern Arizona, and Southeastern California, evaporation is at its maximum, and may reach 100 inches per annum. In the relatively cool and foggy regions such as Labrador, it may fall below 10 inches per annum. Evaporation from a moist soil surface may be two or three times greater than from a water surface, by reason of higher temperature, if exposed to the direct rays of the sun. Shading 65 66 EVAPORATION the soil decreases the evaporation 25 to 30 per cent, and a mulch of straw, leaves, or other loose material still more reduces it. Experiments in Southern California by the Department of Agriculture showed that evaporation from the bare soil could be reduced 57 per cent by a 3 -inch mulch, 81 per cent by a 6-inch mulch, and 87.5 per cent by a g-inch mulch. A soil mulch with similar effect may be produced by care- fully pulverizing the surface soil, or in other words, by cultiva- tion. The experiments showed a saving of 15 to 40 per cent of the evaporation by such cultivation. The advantage of reducing soil evaporation by cultivation or mulching is not alone the saving of water effected but there are two other advantages that may be still more important. Rapid evaporation causes rapid rise of soil moisture, which brings with it the soluble salts carried in solution by the soil water, and by evaporation leaves the salts on or near the sur- face, where they may in time, concentrate to a harmful extent. By holding the soil moisture in the soil until it can be taken up by plants, it is given time to dissolve a larger amount of plant food, and thus greatly nourish the plants when absorbed by them ; whereas, if evaporation is given full play, it soon exhausts the soil moisture, and fresh water must be more often applied, so that the water taken by the plants has not so much time to collect plant food and is less conducive to plant growth. i. Measurement of Evaporation. Several methods have been devised for measuring evaporation, which are more or less 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 apparatus and one quite successful as a means of measuring evaporation is that employed by the U. S. Geological Survey. It consists of a pan, Fig. 16, 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 measured. This evapora ting-pan is of galvanized iron 3 feet MEASUREMENT OF EVAPORATION 67 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 filled 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 FIG. 1 6. Evaporating-pan. it should float with its rim several inches above the surrounding 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 center 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- 68 EVAPORATION 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 Service 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 small 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 times; and 30 miles, 6.3 times. 2. Amount of Evaporation. In Table X 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 (Table XII), more reliable than those obtained with the Piche instrument. These experiments were unfortunately conducted for a relatively short space of time. 3. Evaporation from Snow and Ice. Some experiments were conducted at the Boston Water Works to determine the amount of evaporation from snow and ice. From snow it amounted to about .02 of an inch per day, or nearly 2\ inches in an ordinary season. From ice it amounted to .06 inch per day, or about 7 inches in an ordinary season. The evaporation from snow is greater than this in the arid regions of the West, especially EVAPORATION FROM SNOW AND ICE 69 on barren mountain-tops such as those in Arizona, Nevada, and Utah, where they are exposed to the wind and the bright sun- shine. TABLE X. DEPTH OF EVAPORATION, IN INCHES PER MONTH IN 1887-88 Stations and Districts. 00 00 ."OO c <-< OJ 1 ) OO .00 I" gs fc.00 a M 00 a M 00 -00 rtM |I .00 *3 M I 1 bO< TOO C/J 00 r oo "o " o roo 3" .00 "12 0) Q 13 <0 NORTHERN SLOPE: Fort Assiniboine.. . . Fort Custer Fort Maginnis Helena Poplar River Cheyenne North Platte MIDDLE SLOPE: Colorado Springs. . . Denver Pike's Peak 0.8 0.6 i . i 1. 1 0.4 3-3 0.8 3-0 2.8 2 . I I . 2 1.5 1.4 3.6 0.8 5-7 1.8 3-3 3-7 1 .3 I . 2 1.3 I . I 2. I 0.8 4-0 1.8 4.1 3-5 i . 5 3-1 5-4 3-3 6.1 2.7 8.2 5-4 6.7 7.6 2 I 4- i 6.8 3-2 4-3 4-9 5.2 3-9 It I 8 4.2 4-9 4.6 5-5 5.7 10.4 6.9 4-3 10. S I 9 6.8 9.6 6.8 7.2 6.0 8.0 6.0 6.7 8.3 3 o 5.5 8.0 4.6 7-7 4.8 7-7 4.8 7-2 8.5 4 o 4.8 6.1 3.8 6.4 4-4 8.6 3-7 6.8 6. i 3-5 3-4 2.8 4-3 2.5 . 5-8 2.8 4.6 4-9 2 3 2.5 2.9 2.0 3-0 1.7 6. i 2-3 4-2 4-2 2 8 I. I 1.5 i.. i 2. I 0.7 3-5 1. 1 2.9 3-1 39-5 52.0 35-8 53-4 35-4 76.5 41-3 59-4 69.0 26 8 Concordia 1.3 2.8 1.8 4.8 4-3 5-7 7-3 5-2 6 6 4-3 4-5 3.4 47.2 Fort Elliott SOUTHERN SLOPE;: Fort Sill Abilene 1.3 1.6 T 8 I .9 2.O 1 . 7 3-2 2.6 3 I 5-1 3-8 4. 2 5-4 4.0 5 o 8.2 4-4 5 8 7-6 4.8 9 5 6.2 7-5 7 5 5-4 5- i 6 2 4-7 4.2 4 5 4.2 4.1 2. 2 2.0 54-0 55-4 46. i Fort Davis Fort Stanton SOUTHERN PLATEAU: El Paso Santa Fe Fort Apache Fort Grant Prescott 5-4 3-9 4.0 3-0 2.6 5-2 I 4 5-7 3-9 3-9 3-4 3-0 4.8 2 8 6.7 5-2 6.0 4.2 3-6 6.4 3 6 8.5 7-3 8.4 6.8 6.8 9-2 II. 9-5 10.7 8.8 9-4 10.2 6 12.0 10.9 13.6 12.9 9-1 13-8 8 i 11.4 9.4 9.4 9.2 7-1 12.4 6 6 9.0 ii. 6 7-7 9.8 6.7 10.5 6 s 5-9 3-9 5-6 6.6 5-3 9.0 14 7 5-2 4.0 5-2 6.7 5.2 7-9 5-7 3-6 4.6 5-7 4.1 7.2 -y A 4-9 3-8 2.9 2.7 2.6 4.6 96.4 76.0 82.0 79-8 65-5 IOI.2 Yurna 4. 4 5 2 9 6 9 6 12 6 u.5 8 2 C C 4 6 Keeler 4 6 3 8 7 12 8 8 8 4 8 MIDDLE PLATEAU: Fort Bidwell o 8 8 i 8 4 6 8 8 8 i 4 6 Winnemucca Salt Lake City Montrose Fort Bridger NORTHERN PLATEAU: 0.9 1.8 1.8 1.6 i 6 .8 .7 -5 6.2 3-6 3-7 2.7 3 8 9-1 7-2 6.2 4-3 6 i 9-3 6.9 7-0 4-3 6 5 10. I 8.9 II. i 6.5 6 6 II. 5 9.2 IO.2 7-7 12.0 10.7 8.3 6.8 9-9 9-6 6.9 5-6 6.6 6.5 5-2 4.2 3-7 5-0 3-4 5-2 1.8 2.3 2.0 4-7 T 8 40. y 83-9 74-4 68.3 56.1 Spokane Falls. . . Walla Walla 0-7 i i .7 3 6 4-4 6 2 5-4 4-4 7-7 6.4 3-8 2.5 I J .0 1.4 42.8 N. PACIFIC COAST: Fort Canby I 2 I 8 2 8 I 8 I 8 I 8 : Olympia Tatoosh Island Roseburg MID. PACIFIC COAST: Red Bluffs Sacramento S. PACIFIC COAST: Fresno Los Angeles San Diego 1.3 1.2 I .2 3-0 1.8 1.8 2.3 2.9 . 2 .6 4.6 3-1 2.8 2.0 2.7 1.8 1.8 2.7 5-4 3-7 3-0 2.8 2.5 2.5 1.4 3-9 6.1 4-3 5-6 3-4 2.7 4.1 1.8 4-7 7.0 4.2 6.0 3-0 3-3 3-3 1.8 3-5 6.9 5-6 7.0 3-8 2.8 3.2 1.4 5-4 II .0 5-9 9. I 3-2 3.2 3- i 1.4 4-7 10.7 5.6 IO. 2 3-5 3-3 2.4 I .4 5-0 IO. I 6.5 7.6 3- 1 2.9 1.5 1.6 3-2 10.5 7.3T 6.7 4.1 4-3 ::: 3-9 3-8 3-0 3-2 i . i 1.4 1.6 3-6 2.4 2. 2 3.0 3-7 26.8 18.1 39.2 84.8 54-3 65.8 37.3 37.5 4. 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 70 EVAPORATION and 1875. From these it appears that the amount of evaporation from ordinary soil is about the same as that from water, some- times exceeding it a little and sometimes being a trifle less, though TABLE XI. DEPTH OF EVAPORATION PER MONTH, IN INCHES 'a *j s Place 3 C ji a r^ cd 8 >? 1 cx ^ > 0> I* c cs 1 1 OOO O >O>O ON^CO CN CM LOlO-^-O M coO cocoO tNOO ON ir> -Ln ir> u-) T3 . S O) o o ^ - CHAPTER VII PUMPING FOR IRRIGATION THE practice of lifting water from a lower to a higher level for use in irrigation is doubtless as old as the art of irrigation itself, and was probably the first form oi irrigation tried. In China, India, and other Oriental countries it is still customary to irrigate lands higher than the canals which conduct the water to them, lifting it a few feet by human or animal power. Many various devices of a primitive nature are still employed for this purpose. They are of course possible only where the lift is slight and labor very cheap. The familiar processes of pumping water for stock and domestic farm use, and on a larger scale for a city water supply is apt to mislead many persons when considering problems of pumping for irrigation, owing to the relatively large quantity of water required for irrigation and the corresponding low unit value of irrigation water. For example a city of 30,000 inhabi- tants, covering say 1000 acres, might well afford to expend a million dollars or more for a domestic water supply, while an equal quantity of water would be necessary to irrigate 1000 acres properly, and an expenditure of one-tenth that amount for the water supply might for this purpose be prohibitive. In other words, the value of water for domestic purposes is often more than ten times as great as the value of. the same quantity of water for irrigation. In fact, domestic water supply being indispensable, it must be obtained at any cost, and the value of irrigation water is limited by the value of the crops raised, in which it is only one element of cost. Pumping for irrigation is therefore generally feasible only where the water supply is ample, the lift moderate and power 73 74 PUMPING FOR IRRIGATION cheap. Exceptions to this combination occur only where the products of irrigation are exceptionally valuable. i. Ground-water Supply. Where an irrigation supply is to be obtained from the ground-water by means of wells, a careful study must be made of the quantity of water that can be made available from each well, and also the total supply, and the system carefully planned to accord with the facts developed by that study. One of the commonest errors made in irrigation engineering is the overestimate of the dependable supply of water from a well of given design. The total supply of ground water available in a given locality is also frequently over- estimated, and seldom underestimated. The ground-water supply depends not only on the presence of ground water at the site of the well, but also upon the facility with which additional water reaches the well as water is removed by pumping, and this in turn depends upon the size of the open- ings between the soil particles surrounding the well. If the water-bearing material is coarse sand or gravel in which the spaces occupied by water are relatively large, the water will move toward the well with comparative freedom as the water level in the well is lowered, and the yield from the well may be large, while if the water-bearing medium is clay or fine silt in which the interstices filled with water are very minute, the friction of moving is so great that the water moves through it with extreme slowness, so that the yield of each well is very small, although the total voids in the clay or silt may be and usually are greater in volume than those in coarse sand or gravel. The pore space in soils of the arid region will average nearly 50 per cent, varying from about 40 per cent for clean sand, to 55 per cent for clay. A well-graded mixture, however, contains much less open space, and may have below 30 per cent. Each particle of soil under field conditions is enveloped by a very thin film of moisture which will not drain out, and can be driven off only by heat. The area of these surfaces is 6 or 7 times as great in clay as in coarse sand, and the number of particles is in similar ratio. WINDMILLS 75 2. Windmills. A great deal of irrigation has been done in primitive systems by the employment of the power of the wind, and this is still in extensive use for lifting water from wells for domestic use, stock water, and to irrigate gardens and small orchards. Wind power comes next to animal power not only historically, but in cost. Although the power is free, pumping by windmills is on the average more expensive than any other methods except those employing animal power. This is due to the relatively small amount of power developed by any one unit, the inconstancy of the wind, and the large amount of attention and repairs required by the windmills. For these reasons, the cost of pumping water for irrigation by windmills is generally prohibitive except for intense cultivation of small tracts from which large returns are expected, and in addition the lift must be low and other conditions favorable. Even then the cost is seldom less than $100 per unit for first installation of well, storage tank and pumping machinery, and may reach several times that amount. Besides this the cost of maintenance is high, averaging over $10 per year, while the area which one windmill can serve is generally less than an acre, and may be much less. Windmills of standard make can be purchased of any large dealer in agricultural implements, but representations concern- ing the power to be developed by them should be usually dis- counted to eliminate optimistic assumptions, and liberal allow- ance should be made for the inconstancy of the wind. Notwithstanding its relatively high cost a windmill plant may be the most advisable and economical plant where the requirements or the water supply limit the irrigation to less than one acre. Many farms on the great plains devoted mainly to grazing or dry farming are thus furnished with a reliable supply of vegetables and small fruits which contribute materially to the support and the health of the family. Windmills are extensively used in the San Joaquin valley in California, on the great plains east of the Rocky Mountains and in other portions of the West, for pumping water for irriga- tion. The chief objection to windmills for this purpose is their 76 PUMPING FOR IRRIGATION unreliability, as they are wholly dependent upon the force of the wind for their operation. This objection is not so serious on the great plains between the Rocky Mountains and the Mississippi River, where there is generally a wind to keep mills turning. In most 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. 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 sufficient water to irrigate a considerable area. Ample capacity should be provided to store the water of several days' pumping when irrigation may not be necessary. This storage capacity may be obtained by using one of the various forms of elevated tanks which are supplied by windmill makers; or, 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 larger amount of water. It requires on an average a wind velocity of 5 or 6 miles an hour to drive a windmill, and on an average winds exceeding this velocity are to be had during only eight hours per day. Hence, about two-thirds of the total time 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 per month, or about 8 miles per hour. These averages are somewhat exceeded on the Great Plains, where the average hourly velocity is 10 miles. The following tables give roughly the force of the wind for ordinary velocities: TABLE XIII. WIND VELOCITY AND POWER Miles per Hour Feet per Second Pressure per Sq. Ft. in Lbs. Miles per Hour Feet per Second Pressure per Sq. Ft. in Lbs. 6 7 5 . 12 30 44.0 4-4 10 14-7 5 35 51-3 6.0 15 22.0 i . i 40 58.8 7-9 20 29-3 2 .0 45 66.0 IO.O 25 36.7 3-i 50 73-3 12.3 WINDMILLS 77 TABLE XIV. ENERGY OF WIND ACTING UPON A SURFACE OF 100 SQUARE FEET Velocity of Wind At Sea-level At 1000 Ft. above Sea-level At 2000 Ft. above Sea-level Miles per Hour. H.P. H.P. H.P. 5 0-0835 0.0780 0.0724 IO 0.6683 0.6237 0.5792 15 2.2550 2.1050 i -'9550 20 5-3470 4.9900 4.6340 25 10.4400 9 . 7460 9.0500 30 18.0400 16.8400 15.6400 The following table is derived from Mr. A. R. Wolff's excel- lent work on the windmill, and shows the capacity and economy 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. TABLE XV. CAPACITY OF WINDMILLS GALLONS OF WATER RAISED PER MINUTE TO AN Horse- Size of Revolutions ELEVATION OF Wheel, of Devel- Ft. Wheel 25 Ft. 50 Ft. 75 Ft. ioo Ft. 150 Ft. 200 Ft. oped 10 60 to 65 19.2 9.6 6.6 4-7 O. 12 12 55 to 60 33-9 17.9 n. 8 8-5 5-7 0.21 14 50 to 55 45-i 22.6 15-3 II . 2 7-8 4-9 0.28 16 45 to 50 64.6 3 1.6 19-5 16.1 9-8 8.0 0.41 18 40 to 45 97-7 52.2 32.5 24.4 17-5 12. 2 0.61 20 35 to 40 124.9 63.7 40.8 31.2 19-3 15-9 0.78 25 30 to 35 212.4 107.0 71.6 40.7 37-3 26. 7 i-34 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 former 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 78 PUMPING FOR IRRIGATION ! I'll 00 M V ^ . . o A . O vo O -t CO OC vo OC co (N . vo vo (? O O O t-- O O O r- o \s ,C 2 ~O O PO w 00 A OC oc 6 6 o a LO O O *N t^ O O O +J t) M CO N ro ro M g M a 3 G * O M VO O <"O O O O -* co VOOC* O O O vo Mo O M M VO o ^ o O t t ^ * t^ O O O O vo O O O N O O vo vo M ^ C o ^ ^O ^O H O \/ co O i^ O O OC 6- 6 6 w \y^ O O O i i o co A VO -S 3 P4 CN CO ^ rV M O 5 CO M M 97 80.7 267 21.3 _- 46 O)Vor>.'NCOfO '^t'MMOM 00 M O CO M CN i & i a, ^ "e 8 O Sill O Tt loco vooooO ^J-^-loO fOOO ^ lO Tj- N O t^ O . bJO _g ;^ ; a-S O s;.S 1 |v111 ll|fii!lilljJJJl 146 DUTY OF WATER Q W. X u 2 Q 2 O O AGRICULTURAL DEPARTMENT EXPERIMENTS 147 and greater rainfall. At Yuma, however, a high ground water table assists in keeping down the quantity of water needed. Altogether, without much question, considering all conditions, Salt River Valley shows the best practice in water economy of any of the projects. This is due to the evenness of surface and slope, to an excellent system of rotation, and to frequent cultivation, the outgrowth of the high value of water and ex- perience in its use. The best practice of any Northern project on the list is on the Huntley, although the high duty there is partly due to favorable climate and soil. The most wasteful practice is upon the Rio Grande project, where with shorter season, and some- what greater rainfall, more than twice as much water is applied as at Salt River. This is the less excusable as most of the Rio Grande Valley has a high water table, and some is actually water-logged; nor is there any very open soil, requiring much water. The main explanation is the community operation of laterals in which no control is exercised over the amount of water used, and the primitive methods of irrigation. It is fast ruining the land, and strenuous efforts are being made by the leading men to induce the small communities to surrender the canals to the Government, and to establish rigid control and severe penalties against water waste. Next in order of reckless waste is the Uncompahgre project, which uses in seven months more than twice as much water as Salt River does in twelve. Although the valley has a steep slope and good natural surface drainage, the excessive application of water has water-logged considerable areas of land, and this area is increasing. The sale of water by the second-foot instead of by the acre-foot is one of the leading causes, as it offers no inducement to economy except at the peak of the season. This practice is the outgrowth of local habit, and efforts are being made to change it. Excessive quantities of water are also used on the Umatilla Project, but this is due to open sandy soil with very coarse sub- soil, through which the water readily sinks beyond the reach of crop roots, and frequent irrigation is required. The same is 148 DUTY OF WATER true on a large part of the Minidoka and Orland projects, and on parts of the Boise and Truckee-Carson Projects. The Sun River, Milk River, Lower Yellowstone, Belle Fourche and Klamath Projects are in semi-arid regions, receiving the major portion of their rainfall in the growing season, and crops are often raised without irrigation. They therefore use only small quantities of irrigation water. 12. A Committee on Irrigation from the American Society of Agricultural Engineers addressed a questionnaire to several hundred leading men concerned directly or indirectly with irrigation, whose opinions on the subject were deemed important. The replies concerning the duty of water are condensed in the following table: TABLE XXVI. AMOUNT OF WATER USED ANNUALLY CEREAI CROPS FORAGE CROPS Class of Soil Depth Acres per Second-foot Depth Acres per Second-foot Light 2 . I I ^ 3 I 80 IVIedium I n 187 2 Z 75 Heavy I . 2 242 2. I I0 5 Average I 7 IQ^ 2 6 87 Independently of careful scientific observations, are numer- ous community experiences which throw valuable light on the duty of water in a large community in a long series of years. On this point Fortier says : * " Some twenty- five years ago the irrigators of the Greeley district in Northern Colorado were using a second-foot of water on 40 to 50 acres. In recent years the same quantity has served fully three times as much land with far better results when measured in crop yields. Again, in the early nineties, the farmers in the Bear River Valley in Northern Utah used a second-foot on 60 to 80 acres, but during the past few years the average duty has been a second-foot for 120 acres. Furthermore, when the Legislative Assembly of Wyoming in 1891 limited the duty throughout the State to one second-foot for each 70 acres, it was actuated by the best of motives. Such a duty was then high. Now it is too low and the State is handicapped by having apportioned so large a volume of its public waters on the limit fixed by statute." * Use of Water in Irrigation, page 135. AGRICULTURAL DEPARTMENT EXPERIMENTS 149 In a decision by the Supreme Court of Arizona in 1910, the duty of water for Salt River Valley was fixed at 48 miner's inches, or 1.2 second-feet, for each quarter section of land. This is equivalent to 133! acres to the second-foot. It should be noted that this use is in a very hot and very dry climate, where for months at a time no rainfall appears to assist in moistening the crops, the mean annual rainfall being about 8 inches. This rule limiting water usage has been in force for about seven years, and has aroused no complaint of shortage, as experi- ence shows this quantity to be ample even for those crops of greatest requirement, and on sandy soil. In fact the records of water, delivery show an average use throughout the year only about 3 feet in depth on the land actually irrigated, although the irrigation season is twelve months in length. This is only about one-half the full use of the above allow- ance as an average, so that it is evident that this full use is invoked only in mid-summer, and that the demand is reduced to an average of about one-half in spring and autumn, and one- fourth in winter. The marked improvement over the water duty of other regions, and of the same valley in former years, is due to the increased value of water, and a charge in pro- portion to quantity used, leading to more careful and more skillful use. The leading practices developed by this condition are: 1. An efficient system of rotation, delivering only a day in eight, and use of large heads. 2. Careful preparation of the land. 3. Re-use of waste water for irrigation, by picking it up at lower end of the field. 4. Cultivation of the land soon after each irrigation. Even with these practices considerable areas in Salt River Valley have become waterlogged, and these areas are growing. Of course there remains much room for improvement in these and similar practices, so that the high duty of water can be made practicably much higher. This will undoubtedly be done as the value of water advances. 150 DUTY OF WATER That such a hope is well founded is demonstrated by irrigation practices in Southern California, where nearly double this duty is obtained, by more thorough employment of the above precautions and by the use of pipes and lined canals, cement head ditches and other devices for saving water. Per- haps the most important measure that has led to such a high duty and such successful results from irrigation in Southern California is the habit of thorough cultivation of the surface as soon as possible after each irrigation and each heavy shower of rain. This provides a soil mulch which conserves the mois- ture and also destroys all weeds which has the same tendency. The results obtained in Arizona are easily reached in any region by the adoption of the simple measures enumerated, which are good in themselves, and should be applied nearly everywhere. The results in Southern California furnish the goal towards which Arizona and all the rest should strive. The Utah Agricultural College has done much useful work in teaching and spreading information in favor of greater care in the use of water. In conjunction with the State Conserva- tion Commission it has widely promulgated the following twelve rules for the use of irrigation water: 1. Store the Rainfall in the Soil. Deep, thorough plowing enables the soil to absorb and retain most of the rain and snow water. The more rainfall is stored in the soil the less irrigation water will be needed. 2. Cultivate Frequently and Thoroughly. Water is easily lost from soils by evaporation. Stirring the top soil reduces this evaporation. The soil should be thoroughly cultivated early in the spring, as soon as possible after irrigation, and usually once or more between irrigation. Thorough cultivation will reduce the water needed in irrigation. 3. Keep the Soil Fertile. The more fertile a soil is, the less water is needed to produce a pound or ton of the crop. Plow deeply, cultivate thoroughly, use barnyard manure, and less irrigation water will be needed. 4. Plant in Well-moistened Soil. Well-moistened soil at planting time permits better root development, and delays the AGRICULTURAL DEPARTMENT EXPERIMENTS 151 time of the first irrigation, and thus saves irrigation water during the summer. If rains and snow do not moisten soils sufficiently for planting, irrigate in fall, or in early spring, before planting. 5. Don't Irrigate too Early. By postponing as long as possible the first irrigation after planting, a better root develop- ment is secured and less irrigation water is needed to produce the crop. 6. Irrigate by the Correct Method. Where water is plentiful, the flooding method may be used; where water is scarce, the furrow method only should be employed. Lead the waste water from the furrows to other fields. 7. Irrigate at the Proper Time. Withhold water until the crop is in real need. When irrigating, apply enough water to supply the crop for at least ten days. Irrigate thoroughly when potatoes are in bloom; corn in tassel or silk; lucern just beginning to bud, and grains forming seed. 8. Use Water in Moderation. The acre yield of a crop increases as more water is used, up to a certain limit, beyond which more water causes a decrease in the yield. 9. Spread the Water over Larger Areas. The yield of crop per unit of water always becomes smaller as more water is added. The less water is used in irrigation, the more crop is obtained for the water used. In Utah land is plentiful, water is scarce; it is more important to get a large crop for each acre-foot of water than for each acre of land. 10. Kill the Weeds. Weeds use as much water as do many profitable crops. It costs usually 2000 pounds of water to produce i pound of weeds. Killing the weeds will leave more water for our crops. 11. Repair the Leaky Ditches. Tremendous quantities of water seep from most of our canals and ditches. Stop the leaky places. It will often pay to cement the whole canal. 12. Measure the Water. Land is measured carefully, but water, more valuable than land, is seldom measured. Great progress will be made by Utah as soon as farmers faithfully measure and keep an account of the water used on the land, 152 DUTY OF WATER This is one of Utah's greatest irrigation needs. The Cippoletti Weir may be used by any farmer for the measurement of water. REFERENCES FOR CHAPTER X WIDTSOE, JOHN A. Principles of Irrigation Practice. Macmillan Company, New York. BROWN, HANBURG. Irrigation, Its Principles and Practice. D. Van Nostrand Co., New York. FORTIER, SAMUEL. Use of Irrigation Water. McGraw-Hill Book Company, New York. CARPENTER, L. G. Duty of Water. Bulletin No. 22, State Agricultural College, Ft. Collins, Colorado. MEAD, ELWOOD, and Others. Use and Duty of Water in Irrigation. Bulletin No. 86, U. S. Office of Experiment Stations. U. S. Reclamation Service. Sixteenth Annual Report. WILSON, H. M. American Irrigation Engineering, Part II, i3th Annual Report, U. S. Geological Survey. MEAD, ELWOOD. Report on Irrigation on Investigations for 1904. Bulletin No. 158, U. S. Office of Experiment Stations. TEELE, R. P. Review of Ten Years of Irrigation Investigations. Annual Report of U. S. Office of Experiment Stations for 1908. NEWELL, F. H. Annual Reports on Operation and Maintenance of Reclamation Projects, 1910-11-12-13, U. S. Reclamation Service. BARK, DON H. Duty of Water Investigations in Idaho. Parts of 8th and gth Biennial Reports of State Engineer of Idaho, for 1910-11-12. Inquiry of Am. Soc. of Agricultural Engineers. Reclamation Record, April, 1918. CHAPTER XI MEASUREMENT OF IRRIGATION WATER WATER measurements in connection with an irrigation system are of two main classes. First are those measurements of the stream and of the main canal and larger laterals which are of use in the operation of the system, and do not bear directly upon the amount of water delivered to the individual irrigator. The streams or canals measured are of considerable size and the methods employed in measurement are similar to those used in gaging rivers. The second class of measurements are those designed to indicate the amount of water delivered to each irrigator. They are of relatively small amounts, and to obtain the necessary degree of precision, require the use of other means than those usually employed on large streams. i. Gaging Streams. The first step in the study of the water supply should be the establishment of systematic' observa- tions of stream flow at the various points where such data are required, and records of the daily flow should be kept. A gage should be provided by which to observe the height of the sur- face of the water in the river and should be observed daily or oftener so as to obtain correct results of the daily mean. The simplest form of gage is a wooden rod-, graduated in feet and tenths so as to be easily read, with the graduation made per- manent with nails or otherwise, so that the action of the water will not obliterate them. A position should be selected for the gage rod where it will be protected from driftwood, and yet be easily read, and show the true height of the water in the river. If no better plan presents itself, the rod may be laid on the ground sloping up from the river, and fastened firmly to stakes or posts. The graduations may then be located on it by means 153 154 MEASUREMENT OF IRRIGATION WATER of a Y level. Such a gage may be read twice a day, and this will give fair results on most streams. Somewhat more reliable results may be obtained by pro- viding a well near the river above high water, the bottom of which extends somewhat below low water, and connecting the bottom of the well with the river by a horizontal pipe, so that the water in the well will always stand at the level of the water in the river. By this arrangement difficulty with driftwood is avoided, and observations may be accurately taken with a hook gage. If greater accuracy is desirable, or if the river is subject to sudden fluctuation, it may be advisable to install a mechanical self-recording gage, of which several are on the market. They require frequent attention to keep them in order, but by making continuous record give much greater accuracy on a fluctuating stream than periodic observations of a gage. Measurements of the actual discharge of the stream should be made at frequent intervals, depending upon the character of the stream bed. If this is of permanent character, a complete series of measurements taken at high, low, and intermediate stages will serve to establish approximate values for the various gage heights, and permit the construction of a curve of discharge; and thereafter measurements need be made only sufficient to check the stability of the cross-section and to confirm the stability and reliability of the gage. There are few river chan- nels, however, except those in solid rock, that are naturally so stable that they do not undergo material modification in times of flood, so that in practice it is usually necessary to take a series of measurements every year. Especially is it important to secure measurements of extreme high and low water, so as to control the extremities of the curve of discharge. The discharge of the stream should be measured in the vicinity of the gage, so that no appreciable gain or loss can occur between. The depth may be measured by a rod or sounding line at measured intervals across the stream, each sounding represent- ing half the distance to the next sounding adjacent on each side. The frequency of the soundings should depend upon GAGING STREAMS 155 the roughness of the channel, a few soundings being sufficient where the stream is of nearly uniform depth, and only roughly approximate results are required. For convenience, the sound- ings may be made equidistant, and each sounding should be multiplied by the width of the section which it represents. This will give the area of that cross-section, and the sum of all these cross-sections will give the cross-section of the stream, and this multiplied by the mean velocity of the water will give the total discharge A rough preliminary measurement of velocity may be made by surface floats, timing their passage over a measured course. The mean velocity will be about nine-tenths of the average surface velocity in ordinary streams with smooth bottoms and FIG. 48. Haskell Current Meter. somewhat less, for rough gravelly sections. A convenient form of surface float is a tall bottle, with just enough water in it to make it float upright, and a white rag attached to the cork to make it conspicuous. Several such floats should be passed over the course at different parts of the stream and the time carefully taken. A straight course should be selected free from eddies or material changes in section. More, reliable and accurate measurements of velocity may be made with a current meter, of which several efficient types are obtainable. Those most used are the Price meter, Fig. 49, and the Haskell meter, Fig. 48. The Haskell meter has a slight advantage in responding only to the component of water motion parallel to the axis of 156 MEASUREMENT OF IRRIGATION WATER : FIG. 49. Price Electric and Acoustic Current Meters. GAGING STREAMS 157 the meter, but will not register velocities as low nor as high as the Price meter, and if the shaft on which it revolves becomes slightly roughened by rust, or otherwise, it seriously affects the coefficient of friction, and hence the rating of the meter. The electric meter which has been found to work most satisfactorily under nearly all the varying 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. 49). It is 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 portability and ease of handling as it weighs but little over a pound. In very shallow streams it gives the most accurate results 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 received 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. 49) , 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 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 158 MEASUREMENT OF IRRIGATION WATER feet and tenths of feet, thus rendering it serviceable as a sound- ing or gaging rod. 2. Use of the Current Meter. A bridge spanning a stream without piers in the channel is the most convenient provision for using a current meter. Even one or two piers in the stream may be tolerated if they are not clogged with drift, and do not greatly interfere with the smooth flow of the water. If the stream is sufficiently shallow, a resort to wading may be practi- cable at time of low water, but obviously will not do at high water, nor at any time when the velocity is high, as the body of the observer will cause eddies and vitiate the results. In the absence of a bridge without piers in the stream, the best provision for gaging is to stretch a cable across the stream, and from this suspend a small car in which the observer can ride, propelling the car by pulling on the cable, and stopping at certain points indicated by a tagged wire parallel to the cable. The diagram, Fig. 52, shows such a station. In the absence of the car a boat may be used, anchored to the cable, but this somewhat interferes with the current, and is apt to swing about during the observation and impair its accuracy. In lowering a current meter into a deep stream in time of flood, the strong current tends to carry it downstream, and to prevent its reaching the bottom or any considerable depth. To remedy this tendency, a heavy wire may be stretched across the river 50 or 100 feet above the gaging section, and upon this wire a small pulley is carried from which a smaller wire extends to the meter line, to which it is attached just above the meter and prevents its deflection downstream. A flowing stream has a sloping surface, and moves under the action of gravity, retarded by friction on the bottom, the banks, and in a small degree on the air. The lowest velocity is at and near the bottom and sides on account of their retarding effect. The maximum velocity is just below the surface, in the central portion of the channel, unless a deeper part exists, in which case the depth may vary that law. In order to find the mean velocity of the water in any vertical line, several methods are in use. USE OF THE CURRENT METER 159 1. The integration method is the moving of the -meter slowly and regularly from surface to bottom, and to surface again. This must be done so slowly that the vertical motion of the meter will be an insignificant fraction of the horizontal motion of the water, otherwise the correctness of the record may be affected especially with the cup type of meter such as the Price meter. 2. The measurement of velocity at six-tenths of the depth, has been found to generally give results approximating the mean velocity of the vertical line passing through the point measured. 3. In deep streams the mean of measurements of velocity at surface, mid-depth and bottom will give a close approximation to the mean velocity. Good results from current meter measurements cannot be obtained except at reaches where the channel is fairly straight and regular, and practically free from whirlpools, eddies and back currents. An overflow dam or weir furnishes an excellent opportunity for measuring the discharge of a stream, if it is fairly smooth and regular along its crest. If it has a large bay of nearly quiet water back of it, the discharge may be computed by one or other of the empirical formulae, by measuring the height of the water above the crest of the weir at a point above the line of accelerated velocity, where the measurement gives the general height of the still bay. If the pond above the dam has been filled with sediment, the various weir formulae are not applicable, but the weir may be calibrated by measuring the stream with a current meter a short distance above or below the weir, and when once this is well done, for all stages from extreme low water to extreme flood stage, the stability of the weir, if it be of masonry, insures accurate results as long as no change occurs in the shape or elevation of the weir crest. Where the section measured is sandy and constantly shifting, the gage readings cannot be depended upon as indications of discharge unless checked frequently by actual complete discharge 160 MEASUREMENT OF IRRIGATION WATER USE OF THE CURRENT METER 161 *-' u' FIG. 51. Cable Gaging Station, with Automatic Continuous Recording Gage. FIG. 52. Cable and Car Gaging Station. 162 MEASUREMENT OF IRRIGATION WATER measurements. Such streams are the Colorado, Rio Grande, Arkansas and Platte after they leave the mountains. These streams scour their channels at time of high water and fill them again at low stages, and at all times are building bars or cutting banks, and their channels are thus constantly shifting, so that unless a fixed weir can be used, it is necessary in order to get accurate results to make very frequent measure- ments, ranging from daily in times of high water, to semi- . 53. Wire and Boat Gaging Station. weekly or weekly at low stages. Even these results are not as accurate as less frequent measurements on streams with gravel channels. Where the channel is of coarse gravel or bowlders and hence relatively stable, the principal changes occur at times of flood and a measurement or two at or near the peak of the flood and at extreme low water, with a few at intermediate stages, USE OF THE CURRENT METER 163 generally give a good rating curve to serve till the next -flood stage. The rating curve at such places is often very stable, but should be checked carefully at and after each flood stage. Streams through clay regions are apt to be more shifting than those with gravel sections, but are generally susceptible of fair determination by the methods just described, with somewhat more frequent measurements. No section is entirely free from change unless of rock, or of concrete or other artificial con- struction. In cold countries like the Northern United States and Canada special problems and considerable difficulty are pre- sented in measuring frozen streams. In the early winter needle and anchor ice are apt to form in rapids and flow in masses, sometimes even clogging the stream where frozen over, and causing back water. The surface of the stream may freeze at the edges, leaving the center of the channel open, thus com- plicating the work of measurement. After the channel freezes over the discharge measurements are made through holes in the ice, large enough to allow the current meter to pass through freely. The depth of the stream is taken as the distance from the bottom of the ice to the bottom of the stream. The velocity is taken by the vertical velocity- curve method, which as adapted to winter use, may be described as follows: The meter is held just below the lower surface of the ice, and the velocity at that point recorded. This is repeated at different depths throughout the vertical. These results are plotted with velocities in feet per second as abscissae, and their corresponding depths in feet as ordinates, and a curve is drawn through the points. The mean velocity is obtained by dividing the area included between the curve and its axis, by the depth. This may be measured by planimeter, or estimated by squares. A close approximation may be more easily obtained by dividing the depth into a number of equal parts, taking corresponding velocities from the curve and averaging these. The mean velocity multiplied by the depth as measured will give the discharge. 164 MEASUREMENT OF IRRIGATION WATER 3. Hydraulic Formulae. In 1775, Chezy, a French engineer, developed a formula for computing the flow of water in conduits, either open or closed. Where F = the mean velocity of the water; R = The hydraulic radius of the stream obtained by divid- ing the area of cross-section of the stream by the wetted perimeter; 5 = the tangent of the angle of slope; C = a coefficient then supposed to be constant, but now known to vary with several factors, especially the friction of the channel. The researches of Ganguillet and Kutter produced important modifications of the above formula, in which the factor C is replaced by an expression which takes into account the roughness of the channel, and certain functions of the slope and the hydraulic radius. The friction is represented by the variable " ." This formula, which is in general use for open conduits, and also to some extent for closed conduits, is expressed thus: 1.81 .0028 h4i.6+- v. rs. The value of the factor " n " is empirical and must be assumed largely upon judgment, owing to the difficulty of defining with accuracy the multitude of details which effect the retarding influence of the channel. 4. Measurement of Water to the User. The accurate measurement of water to each irrigator is a prime necessity of every irrigation system. Where the water supply is limited, and the area of irrigation is thereby limited, as is generally the case, it is important that the most economical use of water be secured, in order that the largest area may be irrigated and the greatest production thereby secured. It is still more important MEASUREMENT OF WATER TO THE USER 165 to prevent excessive application of water, because where per- mitted it is almost certain to cause an injurious rise in the water table and the resulting injuries from rise of alkali, water logging etc., which are more likely to occur where water is plentiful than where it is scarce. It is thus very important to limit the amount of water supplied to that actually required for plant consumption, as nearly as this can be attained in practice. This requires great care, both in preparation of the land and in the application of the water, and no measures have been found more efficient than those which engage the direct financial interest of the irrigator by charging for water service by the quantity of water used. To do this requires careful and sys- tematic measurement of the water to each irrigator. The standard unit for the measurement of flowing water in English-speaking countries is the cubic foot per second. This may be defined as a stream of such velocity and volume that one cubic foot of water passes a given point in a second of time. If the mean velocity of the stream is one foot per second, and the cross-section is one square foot, the flow is one cubic foot per second. For brevity the cubic foot per second is called a " cusec " in India, and in America it is called a " second-foot." American irrigators often use another unit having its origin in placer mining, called the " miner's inch," from the discharge of a square inch orifice under a given head. The varying values of this unit under the wide variety of conditions of flow created such confusion that legislative attempts have been made to define the miner's inch in terms of the standard unit, the second- foot. In Colorado the statutes provide that 38.4 miner's inches shall equal one second-foot. In Arizona, California, Montana and Oregon, a miner's inch is one-fortieth of a second-foot, while in Idaho, Kansas, Nebraska, New Mexico, North Dakota and South Dakota it is one-fiftieth of a second-foot, and in other States no definite values have been assigned. This variation unfits the miner's inch for use as a common standard, and we are forced to adhere to the second-foot as the standard unit for expressing the volume of flowing streams. Where volume is considered independent of the element of 166 MEASUREMENT OF IRRIGATION WATER time, the acre-foot has been generally adopted. It is the quantity of water that will cover an area of one acre to the depth of i foot, and is hence 43,560 cubic feet. As a subdivision of the acre-foot, acre-inch is often used, being one- twelfth of the acre-foot, or 3630 cubic feet. The acre-foot is an especially convenient unit of volume from its ready applicability to land areas, and its simple relation to the second-foot. A stream flowing at the rate of i cubic foot per second will discharge about 2 acre-feet, or more exactly, 1.9835 acre-feet, in i day of 24 hours. In i hour it will discharge about i acre-inch. 5. Measuring Devices. The devices most used for measuring irrigation water are weirs, submerged orifices, and current meters, all these being accompanied by gages showing the stage or head of the water in the stream measured. Where there is sufficient available fall the weir is the most convenient and almost universal measuring device. Where there is less fall, and the quantity of water to be measured is small, some form of orifice can be used and is less affected by temporary variations of head than the weir, but must be kept free from trash. Where the quantity of water is too large or the available head is insufficient for the use of the weir, a current meter gaging station may be employed, as described on page 158. a. Weirs. A weir may be defined as a wall over which a stream of water flows. Experiments have shown that where the conditions are well defined the quantity of water discharged over a weir bears a definite relation to the depth of the flow, and by keeping this constant, or by noting its variations, the quantity of water passing in a given time may be accurately measured. This relation, however, varies with the length, shape and other conditions concerning the weir. Weirs are of two general types, namely, free weirs and submerged weirs. A free weir is one where the downstream water elevation is lower than the crest of the weir. A submerged weir is one where the downstream water eleva- tion is higher than the crest of the weir. A free weir is some- MEASURING DEVICES 167 times converted into a submerged weir by increasing the dis- charge sufficiently or by obstructing the stream below sufficiently to cause the downstream water elevation to rise above the level of the weir crest. Where the sides of the weir are placed so as to contract the channel in which the weir is situated, it is called a contracted weir, and where the sides of the weir are coincident with the stream it is called a suppressed weir, the contractions being in this case suppressed. When the sides of a weir are perpendicular to the crest, it is called a rectangular weir. In a trapezoidal weir, the sides make obtuse angles with the crest. A common form of trape- zoidal weir is called the Cippoletti weir in which the sides slope outward from the crest in the ratio of i horizontal to 4 vertical. It is so designed in order that the ratio of the end contractions of the sheet of water to its depth shall be constant. For the accurate measurement of water, weirs should be constructed with the following characteristics: 1. The crest and sides of the weir should be sharp and smooth, and should be distant from the bottom and sides respectively, both above and below the weir, not less than three times the depth of water on the weir. 2. The crest should be level from end to end. 3. The upstream face of the weir should be vertical. 4. Air should circulate freely under the overflowing sheet. 5. The cross-sectional area of the stream above the weir should be not less than seven times that of the overflowing sheet of water. 6. The depth of water on the weir should be not more than one- third its length. The measurement of the head on the weir should be the actual elevation of the water surface above the weir crest, from 5 to 10 feet upstream from the weir. Where the surface velocity of the stream is more than 3 feet per second at a point upstream from the weir a distance of ten times the depth on the weir, or where the area of its cross-section is less than six times that of the overflowing sheet, a correction must be made 168 MEASUREMENT OF IRRIGATION WATER for velocity of approach, which increases the discharge over the weir. From experiments on rectangular weirs, Francis developed the formula : In which Q = the quantity discharged in second-feet; Z, = the length of weir in feet; and H = the head on the weir in feet. The Cippoletti weir permits a simpler formula for the rea- sons above given, and Cippoletti's experiments indicated a slightly higher coefficient, resulting in the following: Where conditions encountered indicate a velocity of approach sufficient to affect the result, this may be computed from the following formula : In which V = the velocity of approach; Q = the discharge in second-feet; and A = the area of cross-section of the channel of approach. To adapt this to the formulae, V should be converted to terms of head by the following formula: In which h = the head due to velocity of approach. Where this results in a considerable value for //, that value may be substituted for h in the following formula proposed by Francis for cases requiring correction for velocity of approach : The corresponding formula for Cippoletti weirs is: MEASURING DEVICES 169 . Measuring Orifices. Where the amount of floating debris is negligible or can be thoroughly controlled and the quantity of water to be measured is not too great, some form of orifice is perhaps the best and most accurate of the cheaper forms of canal measurement. It can be used with smaller loss of head than required for a weir, and the results are less affected by errors in observing the head. It is worthless, however, whenever it is liable to be clogged in any degree. An orifice, as the term is here used, is any form of opening in the wall of a channel entirely below the surface of the con- tained water. The wall may have any position from horizontal to vertical, and the water may discharge either into water or into the open air. If it discharges into air it is said to be free. When it discharges into water, it is called a submerged orifice. A contracted orifice has its perimeter located far enough from the bounding surfaces of the containing channel, so that the filaments of water approaching the orifice are sharply deflected in passing out, and by their inertia contract the issuing stream to a smaller diameter than that of the orifice. A suppressed orifice has its perimeter so nearly coincident with the bounding surfaces of the channel of approach, as to eliminate this contraction. Between these limits are many degrees of partial contraction. If the opening is cut in a wall of considerable thickness, or if a discharge tube is attached, it requires entirely different coeffici- ents from a simple orifice. The most suitable orifice for measurement is the vertical sharp-edged rectangular, contracted, submerged orifice. This type can be accurately reproduced and its discharge coefficient has been carefully determined. The thin, sharp edges which form the boundaries of the orifice, must be at sufficient distance from the boundaries of the con- taining water prism, so that the filaments of water in passing out will have the maximum deflection from a straight line, as they enter the orifice, and thus cause the maximum contraction of the issuing stream. To accomplish this, the orifice must be 170 MEASUREMENT OF IRRIGATION WATER at a distance from the bounding surfaces of the prism, at least twice the least dimension of the orifice. The upstream face of the orifice should be vertical, and the sides should be vertical. The top and bottom edges of the orifice should be parallel and horizontal. The cross-sectional area of the water prism for 25 feet on each side of the orifice, should be at least six times the area of the orifice. The head on the orifice to be used in com- putation is the actual difference in elevation between the upstream and downstream water surfaces. As irrigation channels are usually much wider than their depth, it is convenient to make measuring orifices longer than their height. To simplify computations it is well, if practicable, to have the cross-sectional area of the orifice an even number of square feet. A length of 2 feet with a height of 6 inches, for example, gives an area of i square foot, which is the most con- venient area of all. The formula for computing the discharge of the standard rectangular submerged orifice follows: Q = o.6i\/2gHA. It will be noted that the discharge of the orifice varies with the square-root of the head, while that of a weir varies as the cube of the square-root of the head. For this reason the former is more accurate, especially under conditions where the head may be subject to temporary unrecorded fluctuations. For the same reason it requires considerably more velocity of approach to sensibly affect the discharge of an orifice, but when this is considerable, it may be allowed for by the following formula : the symbols having the same significance as heretofore. This need seldom be used where the conditions of accuracy are properly met. When it is necessary to place the orifice at the bottom of the channel or otherwise to suppress a portion or all of the contrac- MEASURING DEVICES 171 tion of the orifice, the discharge may be approximately obtained by the following formula: Q = o.6i(i+o.i$r)\/2gHA, where r ratio of the suppressed portion of the perimeter to the whole perimeter of the orifice, and the other symbols have the same significance as heretofore given. The coefficients in this formula are not well determined, and cannot be made as exact as those in the standard orifice, which is more accurately reproducible. Notwithstanding its theoretical accuracy, the uses of the orifice are limited in practice by three important conditions: 1. It is adapted only to small quantities of water. 2. Unless very large it is often liable to be partially clogged with debris, thus vitiating the results. 3. The necessity of observing both the upstream and down- stream head. For the first two reasons the weir is generally preferred where sufficient head is available and for this reason the free orifice is seldon used as this requires as much head as a weir; it may be convenient, however, in some cases where it is desired to measure a small quantity of water without trash. Where the available fall for measuring a canal is too small, or the amount of sediment too great to permit good results from the use of weirs or orifices, it may be necessary to establish a current-meter gaging station. This should be located in a straight uniform section of the canal with clean stable banks and bed, where velocities are unaffected by drops, checks and turnouts, or any other influence likely to affect the relation of gage height to discharge, upon the constancy of which relation the value of the results will largely depend. The essential elements of the observations are frequent or continuous records of the gage height at the station, and careful measurements of discharge taken at various stages of canal height, to indicate points of control by which a curve may be plotted which shall show for all stages, the relation of gage height to discharge. 172 MEASUREMENT OF IRRIGATION WATER The best provision for current-meter measurements is a bridge spanning the canal without any disturbance of the flow by piers or abutments. This should be divided into permanently marked sections of 10 feet for large canals, and less intervals for small ones. At each station the depth and velocity are carefully measured, and an assumption made that each measured result is the mean for equal distances on each side thereof, so that each measurement represents one of the sections. The velocity in feet per second, multiplied by the depth in feet, multiplied by the width of the section, will give the discharge in second-feet of that section, and the sum of the discharges of all the sections will be the discharge of the canal. As a temporary makeshift the velocity of the canal may be measured by means of floats, but where measurements are to be made frequently, both accuracy and economy require that the current meter should be employed. The meters and their use are described on page 157. Whether measurements are made on weirs, orifices or with current meters, they require records of gage height in order to determine the discharge. In a canal wherein the discharge is kept practically constant, it is sufficient to read the gage twice a day, with additional readings whenever the quantity of water flowing is changed. Where changes are frequent, either from changing the position of the headgates or from changes in the quantities taken out by laterals, an automatic instrument should be employed to make a continuous record. Various forms of water meters have been extensively used where greater accuracy is required than can be obtained with weirs and orifices, or where conditions make their use convenient. In general they are too expensive for practical application to the measurement of irrigation water, except where this is very valuable. Where a small quantity of water is delivered through pipes, the ordinary water meter used for city supplies is the most convenient and suitable. It consists of a set of blades caused to revolve by the passing water, and an indicator recording the revolutions of the blades. MEASURING DEVICES 173 When mechanically perfect they are very accurate, but they are too complicated and expensive for irrigation use, and are not suitable for measurement of the large quantities of water required in irrigation. The rate of discharge through the weirs and orifices described depends upon the head of water above, and in the cases of submerged weirs and orifices, the elevation of the water below must also be known. It thus becomes necessary to keep a record of these elevations, and this attention is the principal part of the cost of water measurement by these methods. If the gages are read only at intervals by an observer, no account is had of fluctuations between observations, and serious inac- curacies may be involved. Devices are therefore employed to make and keep a continuous automatic record of the gage FIG. 54. Rectangular Measuring Weir. height, and these again involve expense, and complicated clock- work and recording apparatus liable to disarrangement, and requiring considerable skill for repair. Several recording devices of reasonable simplicity and efficiency are obtainable from instrument makers, all dependent upon the rise and fall of the water as indicated by a float controlling a pen on a dial or cylinder driven by weights and regulated by clockwork. c. Banna Meter. F. W. Hanna has invented a recording device designed not only to record the height of the water but to translate this into discharge and to give the results in acre- feet, which it indicates on a counter. This machine is also controlled by a float, driven by weights and regulated by clockwork. Its advantage over the standard automatic gage is that it eliminates the need of using a table for interpreting the record. It is however, more complicated, of course. 174 MEASUREMENT OF IRRIGATION WATER To obviate the necessity of keeping and recording gage heights, and also to secure uniformity of flow, various devices have been proposed to keep the head constant over weirs or orifices, some of which are in limited use. d. The Azusa hydrant is simply a series of submerged orifices of different sizes which may be opened or closed at will, in accordance with the quantity of water desired. To keep a FIG. 55. Foote's Measuring Weir, A. Water Divisor, B. constant head, a weir is provided in the canal just below the hydrant, and an opening in this so adjusted as to keep the water in the canal just above the crest of the weir. If the weir is made with very long crest, any rise of water in the canal will mostly pass over the weir, but will also somewhat increase the discharge through the orifices. e. The Foote Measuring box is a device adjustable to cause any desired quantity of water to flow nearly constantly, and so MEASURING DEVICES 175 arranged as to measure this in miner's inches. It consists of a box flume fitted into the ditch from which the water is to be measured. This flume is divided longitudinally into two com- partments of unequal sizes, and the entrance of water into each is controlled by flash boards, so that in use, the water stands 3 or 4 inches higher in the small compartment than in the large one. The small compartment is closed at the lower end, and provided with a spillway into the large one, over which the water flows when it reaches a certain depth. On the opposite side of the small compartment is a long horizontal slot 4 inches high, the center of which is 4 inches below the crest of the spill- way, and closed by a gate sliding horizontally, adjustable to a scale, so that the opening may be adjusted to any length from zero up to the entire length of the slot. The area of the open- ing in square inches is thus four times the length of the opening as adjusted, and when the water stands at the crest of the spill- way, or 4 inches above the center of the slot, the area of the opening expresses the discharge in miner's inches. The success- ful use of this measuring device requires the loss of 4 or 5 inches of head in the supply lateral, and about a foot into the receiving lateral. It is therefore not adapted to use where such heads are not available, but is otherwise convenient and reasonably accurate. Many similar devices have been proposed and used to some extent, which are merely more or less ingenious combinations of weirs and orifices ? some of which are described in detail in Bulletin No. 247 of the Agricultural Experiment Station of Berkeley, California. All such weirs and orifices require considerable loss of head and a great deal of attention to the stage of water, involving an automatic time register if any great accuracy is required. To avoid these objections, several devices have been invented to measure the quantity of water more directly, without so much loss of head, and with increase of simplicity of mechanism. /. The Dethridge meter is a paddle wheel consisting of a drum on a horizontal axle, with projecting blades of metal attached at equal intervals to the periphery of the drum, revolving in a 176 MEASUREMENT OF IRRIGATION WATER box or flume, in which it fits closely without touching, so that very little water can pass without moving the blade and turning the wheel. The bottom of the box is curved to correspond to the circular path of the blades, so that in passing, a blade does not leave the proximity of the bottom until the next blade reaches it, and so that in use, the water always fills the box up to the bottom of the drum. By recording the revolutions of the wheel, information is obtained which can be readily translated into terms of flow. The axis of the wheel can be attached directly to a counter by reading which the revolutions are obtained, and by multiplying the velocity thus obtained by the cross-section of the space through which the water passes under the drum, the discharge is obtained directly, affected, however, by the leakage past the vanes, which in turn is affected by the friction involved in turning the wheel. A well-made instrument of this kind is very accurate, and measures the water with a very slight fall, depending on the quantity passing. It will give satisfactory results with quantities varying between maxima and minima in the ratio of 5 to i. In practice the box, if of wood, is liable to warp slightly, and thus vary the clearance around the blades, or the friction of turning, or both, which changes the coefficient of discharge. For this reason, the direct method of inferring the discharge from the cross-section and wheel readings is some- times rather rough and it is better to have a rating for the coefficient of discharge by actually measuring the discharge at the various stages. This rating should be renewed whenever conditions change perceptibly. It is best to construct the box surrounding the wheel of rich concrete carefully smoothed, and if this be properly founded, little change need be expected. This meter can be built of any size desired. It is moderate in cost, is extremely simple in principle, in construction and in operation. It gives satisfactory results, with very small loss of head, but requires attention to prevent interruption if much floating drift is passing. g. The Hill meter, devised by Louis C. Hill, consists of a short box or pipe in the form of an inverted siphon, through MEASURING DEVICES 177 which the water to be measured is made to pass, the issuing end being vertical and lower than the other and somewhat smaller. As the water rises through the issuing end of the siphon, it passes a set of inclined vanes attached to a central drum revolving on a pivot, and the flowing water striking the inclined vanes turns the drum, the axis of which drives a counter so arranged on a dial as to register the passing water directly in acre-feet. A single opening and meter can be used with an accuracy of about 2 per cent, over a range from i minimum to 5 maximum. Unless the entrance of the siphon is well screened the meter is liable to be choked by floating weeds or other drift. When kept free from drift and properly built, this meter is very accurate, reliable and simple. It requires very little loss of head in the measured water. h. The Grant-Mitchell or Australian meter is used to some extent in Australia, and is similar in principle to the Hill meter. It is, however, more expen- sive, and seems to have no special advantages over that instrument, but is said to give good results. Both are patented. i. The Venturi meter is a very simple and accurate device for measuring water, much used on city water supply, and recently intro- J . . FIG. 56. Australian Water Meter. duced to some extent on irri- gation works. The water is conducted under pressure through a pipe which is gradually and gently contracted, and then still more gradually returns to its normal dimensions. In passing through the contracted throat, the velocity of the water is increased in the same ratio that the cross-section of the pipe is diminished. By this means a portion of the pressure head is converted into velocity head, and by measuring the pressure at a point before contraction begins, 178 MEASUREMENT OF IRRIGATION WATER and also at the contracted throat, the quantity of water passing may be computed from the following formula: Q = Ca in which a = the area at the throat; A = area of the pipe before contraction; h = pressure head at A same at a; C = a coefficient usually from .97 to .99, dependent on the perfection of the meter. Chart Recorder continuously Records cubic feet per second FIG. 57. Venturi Meter and Recording Device on Lateral Head. The only complication about this meter is the measurement and registration of the pressures, a and A. Elaborate electric devices are sometimes used for this, which are very accurate but too expensive for irrigation uses. Floats can be used in connection with the ordinary automatic gages, which will give approximate results if kept in order. j. Venturi Flume. Mr. D. C. Hermy has proposed a simple and cheap modification of the Venturi meter, called the " Venturi Flume." In this flume a contraction is effected by a curved metal or reinforced concrete sheet placed between the sides of the flume, depressing the surface of the water. At the point of greatest depression the sheet is for a few inches parallel MEASURING DEVICES 179 with the floor of the flume and is pierced by several holes allow- ing water to rise above the sheet. One gage is installed in the flume above the measuring device, and the second one in the still water pond formed by the curved sheet and the sides of the flume. From the reading of these two gages " H " is found, from which the flow may be calculated by the above formula. The device was tested in 1915 in various forms on four projects of the Reclamation Service, the flow being checked by weir measurements. The quantity of water varied in these experiments between i second-foot and 7 second-feet, and the throat velocity from i to SyV feet per second. These showed deviations from correct results varying from about i to about ii per cent of the quantity of water measured, the more accurate results being generally obtained with the larger quantities of water. The loss of head through the throat varies between .03 foot and .05 foot, being greater for the higher velocities and for the smaller quantities of water. The loss varied from 13 per cent to 56 per cent of the velocity head. Losses exceeding 40 per cent of the velocity head at the throat occur only for height of throat less than 3 inches. With a throat height of 4 inches or over the losses are from 24 per cent down, the tendency being to a reduction of percentage as the velocity increases, although the actual loss of head may be greater. This measuring device, especially in the smaller sizes, is liable to clog with large weeds, but passes leaves and other small trash. It has not been commercially manufactured. In 1915 Mr. V. M. Cone of the United States Department of Agriculture designed and experimented with another form of " Venturi Flume " in which contraction is effected by drawing in the sides of the flume, leaving the water surface free. Experi- ments on this type of flume were made in connection with some of those of the Henny flume above described. The experiment showed that below a flow of 2 second-feet the coefficient fluctuates erratically with unreliable results. Above this amount the 180 MEASUREMENT OF IRRIGATION WATER TABLE XXVIL DISCHARGE OF STANDARD RECTANGULAR SUB- MERGED ORIFICES IN CUBIC FEET PER SECOND, COMPUTED FROM THE FORMULA Q = o.6iV^H. A Head H, Feet Cross-sectional Area A of Orifice, Square Feet 0.25 0.5 0-75 i .0 1.25 1-5 i. 75 2.O O.OI O. 122 0.245 0.367 0.489 0.611 0-734 0.856 0.978 O.O2 0.173 0.346 0.518 0.691 0.864 1-037 I . 2IO 1.382 0.03 O. 212 0.424 0-635 0.847 1-059 I.27I 1.483 1.694 0.04 0.245 0.489 0-734 0.978 1.223 1.468 I.7I2 1-957 0.05 0.273 0-547 0.820 1.093 1.367 1 .640 I-9I3 2.186 O.o6 0.300 0-599 0.899 1.198 1-497 1.797 2.097 2.396 0.07 0.324 0-647 0.971 1.294 i .617 1.941 2-265 2.588 0.08 0.346 0.691 1.037 1-383 1.729 2-074 2.42O 2.766 O.OQ 0.367 0-734 I . IOI 1.468 1-835 2. 2OI 2.638 2-935 O. IO 0.387 0-773 i . 160 1-557 1-933 2.320 2.707 3-094 O. II 0.406 0.811 1.217 i .622 2.027 2-433 2.839 3-244 O. 12 0.424 0.847 1.271 1.694 2.118 2.542 2.965 3-389 0.13 0.441 0.882 1-323 1.764 2. 2O5 2-645 3-086 3-527 0.14 0.458 0.915 1-373 1.830 2.287 2-745 3 . 203 3 . 660 0.15 0.474 0.947 i .421 1.895 2.369 2.842 3.316 3.790 0.16 0.489 0.978 1.467 1.956 2-445 2-934 3-423 2.912 0.17 0.504 1.008 1.512 2.016 2.520 3.024 3-528 4.032 0.18 0-5I9 1-037 I-556 2.075 2-593 3.II2 3-631 4-150 0.19 0-533 i. 066 1-599 2.132 2.665 3.198 3-731 4.264 o. 20 0-547 1.094 1.641 2.188 2-735 3.282 3.829 4-376 0.21 0.561 1. 1 20 1.681 2. 241 2.801 3-36I 3.921 4.482 O. 22 0-574 1.148 1.722 2. 296 2.870 3.464 4.018 4-592 0.23 0.587 1.172 1-759 2-345 2.931 3-517 4-103 4.690 0.24 0.600 1.198 1-797 2.396 2-995 3-599 4-193 4.792 0.25 0.612 1.223 1-834 2.446 3-057 3.668 4.280 4.891 0.26 0.624 1.247 1.871 2.494 3-II7 3-741 4-365 4.988 0.27 0.636 1.270 1.906 2.541 3.176 3.811 4-446 5.082 0.28 0.646 1.294 1.942 2.589 3-236 3-883 4-530 5.178 o. 29 0.659 i-3i9 1.978 2.638 3-297 3-956 4.616 5.276 0.30 0.670 1-339 2.009 2.678 3-347 4-017 4.687 5-356 MEASURING DEVICES 181 TABLE XXVII. Con tin ncd Head //, Cross-sectional Area A of Orifice, Square Feet Feet 0.25 o.S 0.75 i .0 1.25 i. 5 1.75 2.0 0.31 0.681 I-363 2.045 2. 726 3.407 4.089 4-771 5-452 0.32 0.692 1.382 2.073 2.764 3-455 4.146 4.837 5.528 0-33 0.703 I-405 2. IO7 2.810 3-5I3 4-215 4.917 5.62O 0-34 0.713 1 .426 2.139 2.852 3-565 4.278 4.991 5.704 0-35 0.724 1.446 2. 169 2.892 3-615 4.338 5.061 5.784 0.36 0-734 1.467 2. 201 2-934 3-667 4.401 5-135 5.868 0-37 0-745 1.488 2.232 2.976 3.720 4.464 5.208 5-952 0.38 0-754 1.508 2. 262 3.0l6 3-770 4.524 5-278 6.032 0-39 0.764 1.527 2.291 3-054 3.818 4.582 5-345 6. 109 0.40 0-774 1-547 2.321 3-094 3.867 4.641 5.415 6.188 0.41 0.783 i-S 6 7 2-350 3-133 3.917 4-7oo 5.483 6.266 0.42 0.792 1-585 2-377 3.170 3.962 4-754 5-547 6-339 0-43 0.802 i .604 2.406 3.208 4.010 4.812 5-614 6.416 0.44 O.Sll 1.622 2-433 3-244 4.055 4.866 5-677 6.488 0-45 0.820 i . 640 2.461 3.28l 4.101 4.921 5-741 6.562 0.46 0.829 1.659 2.489 3.318 4-147 4-977 5-807 6.636 0.47 0.839 1.678 2.517 3-356 4-195 5-035 5-874 6.713 0.48 0-847 1.695 2-542 3.389 4.237 5.084 5-931 6.778 0.49 0.856 1.712 2.568 3-424 4.280 5.136 5-992 6.848 0.50 0.805 1.729 2-594 3.458 4-323 5-i88 6.052 6.917 0.52 0.882 1.763 2.645 3-527 4.409 5-290 6. 172 7-054 0-54 0.898 1.797 2-695 3-593 4.491 5-390 6.288 7.186 0.56 0.915 i . 830 2-745 3.660 4-575 5-490 6.405 7.320 0.58 0.931 1.862 2-794 3-725 4.656 5.587 6.518 7-450 0.60 0.947 1.895 2.842 3-790 4-737 5-684 6.632 7-579 0.62 0.963 1-925 2.887 3-850 4.812 5-775 6.737 7.700 0.64 0.978 1.956 2-934 3.912 4.890 5.868 6.846 7.824 0.66 0-993 1.987 2.980 3-974 4.967 5.960 6-954 7-947 0.68 1.008 2.016 3.024 4-032 5.040 6.048 7.056 8.064 0.70 1.023 2.046 3.069 4.092 5-II5 6.138 7.161 8.184 0.72 1.038 2.076 3-II4 4-152 5-I90 6.228 7.266 8.304 0.74 1 .052 2. 104 3.158 4. 210 5- 260 6.311 7-369 8.421 o. 76 1. 066 2.132 3.198 4.264 5-330 6.396 7.462 8.528 0.78 1. 080 2. 160 3.240 4.320 5.400 6.480 7.560 8.640 0.80 1.094 2.188 3.282 4-376 5-470 6-564 7-658 8.752 182 MEASUREMENT OF IRRIGATION WATER accuracy is about the same as that for the Henny flume. It has the disadvantage that the formula by which the flow is to be calculated must take into account not only " H " but also separately the depth at either of the two gages. Stilling boxes are necessary with high velocities to permit accurate observations of the surface of the swiftly flowing water. It has the advantage, however, of being less easily clogged with drift, as the upper surface is free from obstruction. The successful and practical meter for measuring water to each farm must be both simple and cheap. It is used so fre- quently that any complication or trouble with each one aggre- gates a large amount and hence the importance of simplicity and reliability. This extends also to the formula for computing results. It is important to have these computations worked out and tabulated for all possible cases, not only for convenience and economy of time, but also to eliminate liability to errors. One of the greatest economies possible in the measurement of water is the use of the rotation system, by which each irriga- tor takes a much larger quantity of water than he would be entitled to continously, and shortens the time of use propor- tionately, allowing his neighbors to do the same. By this means it is necessary to measure the quantity used by all those who rotate together, and the length of time this volume is received by each indicates the total quantity each receives. This reduces the number of measurements to be made by meter, and is more accurate than meter measurements to individuals, as the time of delivery to each user can be easily determined to a second if desired, which is a much closer measurement than any meter measurement. This is one of the minor advantages of the rotation system. In the present state of the art, the weir, either rectangular or Cipolletti, is the most practicable meter for irrigation pur- poses. If great accuracy is required, the mechanical register is employed to record the head, and if the forebay is kept clean good results are obtained. MEASURING DEVICES 183 REFERENCES FOR CHAPTER XI 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. 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. WEISBACH, P. J. Hydraulics and Hydraulic Motors. Translated and Edited by A. Jay Du Bois. John Wiley & Sons, New York, 1891. HANNA, F. W. Measurement of Water for Irrigation, U. S. R. S. Handbook. DRAKE, E. F. Report of Hydrometric Surveys for 1916, Dept. of Interior, Ottawa, Canada. SCOBEY, F. C. Flow of Water in Irrigation Channels. Bulletin 194, U. S. Office of Experiment Stations. CONE, V. M. The Venturi Flume. Journal of Agricultural Research, Vol. IX, No. 4. Washington, D. C. MEAD, DANIEL W. Water Power Engineering. McGraw-Hill Book Co., New York. BARK, DON H. Experiments on the Economical use of Water in Idaho. Bulletin 339, U. S. Office of Public Roads and Rural Engineering. Some Measuring Devices used in the Delivery of Irrigation Water. Bulletin 247, Agr. Exp. Sta., University of California, Berkeley, Cal. MORITZ, E. A. Flow of Water in Pipes, Eng. Record, Vol. LXVIII, page 667. CHAPTER XII DRAINAGE FOR the health and vigor of the most useful plants, the roots require air just as certainly as they require water. If the soil in the root zone is saturated with water this excludes the air, and if this continues for any considerable length of time the plant suffers and eventually, unless this is corrected, it dies. There is much difference in the rapidity with which various plants are so affected, and a few water-loving plants require their roots to be in saturated soils for the best results. The tules, rushes, water grasses and willows are the commonest spontaneous growths of this kind, and several varieties of coarse grasses also thrive in wet places. The principal useful plants which grow best in saturated ground are rice, cranberries, and some varieties of dates. It is difficult in most localities to apply to the surface of the land in irrigation, sufficient water for the maximum crop pro- duction, without allowing a considerable quantity of the water applied to escape to the underlying water table. In addition to this, every irrigated region is traversed by numerous canals and laterals, continually wet during the irrigation season, from which water steadily percolates downward to the water table in considerable quantity unless the canals are well lined with concrete. For these reasons it generally occurs that after a large valley has been irrigated for a few years, the ground water begins to rise, and unless there is free escape through coarse subsoils to deep drainage lines, the water table rises to a point where it injures vegetation, and wherever it continues to rise, it eventu- ally kills all vegetation except aquatic, or water-loving plants. This generally occurs first in low places, and ponds and marshes 184 SIGNS OF SEEPAGE 185 are apt to form which gradually increase in area unless means are taken to prevent or cure the trouble. This result is so universal that there is scarcely a large valley in the world that has been irrigated for several years that does not have trouble with seepage, and a problem of drainage. In many places this result is wide-spread and disastrous. It is said that large areas in India, formerly subject to occa- sional famines caused by failure of crops on account of drouth were relieved by irrigation works to counteract the drouths only to find that the mortality from malaria induced by the marshes resulting from irrigation was greater than that formerly due to famine. Large areas in Egypt have been abandoned on account of the rise of ground water and accompanying alkaline conditions. In the Murgab Valley in Turkestan the irrigated lands have been largely abandoned on account of the rise of water and alkali, and the canals built to new lands. Large areas in the Valley of California have had their fertility reduced or destroyed from the same cause. In the San Luis Valley of Southern Colorado, where irriga- tion has been widely practiced, nearly 400,000 acres of land have been waterlogged. The Rio Grande Valley in New Mexico and Texas shows extensive results of high water table and alkali. Many of the projects recently built by the U. S. Reclamation Service already show similar problems which have been or are being met by the construction of drainage works. It is thus evident that the subject of drainage and swamp reclamation is a necessary branch of irrigation engineering and should be studied as such. i. Signs of Seepage. No definite rules can be formulated to indicate where seepage is likely first to appear or to develop as irrigation proceeds. A careful study of soil and topographic conditions may furnish evidence to indicate whether seepage is likely to occur, but it is seldom that the movements of ground water can be foretold with any certainty, and trouble is often experienced where least expected. For this reason it is impracti- 186 DRAINAGE cable to wisely plan and construct drainage works for irrigated lands in advance of their actual irrigation. It is nevertheless very important that the rise and movement of the ground water be closely observed from the time that irrigation begins, for the rising water will bring alkali to the surface if any is available in the soil, and the longer this accumu- lates, the longer it will require to reclaim the lands and the greater will be the expense thereof. The first surface evidence of a dangerous rise of ground water may be a temporary increase in crop production induced by the abundant and constant water supply not yet excessive. Numerous cases have occurred where the rising water table has produced large crops, and the continuing rise as the crops matured has so softened the ground as to render it too boggy to permit machinery to harvest the crop. Usually, however, the progress is much slower than this. In order to have proper warning of the approach of dangerous seepage, it is necessary to keep close observation on the position of the ground water by means of wells located at suitable inter- vals over the irrigated tract. It is usually found that there is an annual oscillation of the water level, which rises during the irrigation season and begins to decline slowly soon after the water is shut out of the canals. If this decline is each year back to the level at which it began the irrigation season, and this level is not too high, it may be that the ground water has ample escape to neighboring drainage lines through the subsoil. Its move- ments should be carefully watched, however. Fig. 58 shows the fluctuation of ground water in the Rio Grande Valley, New Mexico, and its relation to the application of water in irrigation. The ground-water curve is a composite showing averages in twenty representative wells scattered over an area of 8500 acres. The net irrigated area was 5300 acres, on which the average seasonal application was 4.3 feet in depth, which would cover the gross area of 8500 acres to a depth of 2.7 feet. Fig. 59 shows the seasonal fluctuation and continual yearly rise of ground water in an irrigated section of the Boise Valley, Idaho. Fig. 60 shows for another portion of the Boise Valley, the fluctuation of the water table before and after drainage. SIGNS OF SEEPAGE 187 Moisture rises above the water table by capillary attraction, the height to which it will thus rise varying from a foot in sandy soil, to a maximum of 8 feet in clay. When the capillary water FIG. 58. Curve Showing Fluctuation of Ground Water and Application of Irriga- tion Water in the Rio Grande Valley. After Burkholder. approaches the surface, evaporation takes place, and in coarse soil this may prevent moisture from showing on the ground until the water table actually reaches the surface. When this happens free water will appear in pools, unless the rate of seepage 188 DRAINAGE is less than the evaporation, in which case the free water does not appear although the water table may be practically at the surface. By taking frequent and careful observations of the position of ground water it is possible, in most cases, to predict the injury of the land. These observations also serve another useful purpose. An accurate knowledge of the ground-water level 19/3 19/4 J9/ /9t7 to 18 ceL PX FIG. 59. Curve Showing the Seasonal Fluctuation and Rise of Ground Water in Boise Valley, Idaho. After Burkholder. over a considerable tract may indicate the movements of the water, by applying the simple rule that water tends to flow down hill, the slope of its surface showing the direction of flow. This knowledge will often show the origin of much of the seepage, and suggest means of cutting off the supply by providing intercepting drains. Alluvial streams with shallow channels often feed the water table as shown by its response to the rise and fall of the stream. If the subsoil be coarse, this response may be quick and complete, but there is always a lag SIGNS OF SEEPAGE 189 DEPTH OF GROUND WATER BELOW GROUND SURFACE-FEET SNOW MZLTL MAR flPff do N DEPTH OF GROUND WATER BTLOW GROUND SURFACE -FEET FIG. 60. Curve Showing Rise of Ground Water before Construction of Drains and Effect of Drains at Considerable Distance in Lowering and Keeping it Below the Danger Point. Record from a well in a drained district of the Boise Valley, Idaho. 190 DRAINAGE in time and elevation. That is, a water table controlled by a stream never reaches so high a maximum elevation as the stream, and reaches its culmination at a later date than that of the stream. Where this maximum is so high as to injure vegeta- tion, it may be necessary to install an intercepting drain near and parallel to the river. The same conditions are sometimes fulfilled by a canal. In fact the canals and laterals always contribute a considerable portion of the seepage water unless they are lined with concrete, and where water users are rea- sonably careful in the application of the water in irrigation, the canals and laterals in open soils may contribute the major part of the seepage water. On the other hand, if water is lavishly applied in irrigation, its contribution to the ground water may greatly exceed the seepage from canals. It is important to ascertain the source of seepage water. Where the soil is fine-grained and the water table remains permanently 4 to 6 feet below the surface, the capillary action may keep the soil moist in the root zone, and good crops may be produced by means of the ground moisture without surface irrigation. If the soil contains injurious salts, however, the constant rise of water from below and its evaporation from the surface will accumulate those salts at or near the surface in the soil occupied by plant roots, gradually injure the soil, and eventually make it perhaps entirely barren. The rise of alkali is sometimes the most serious phase of the seepage problem. In an arid region nearly all except very coarse soils contain alkaline salts and a high water table is sure to bring these toward the surface. If the salts are abundant the destruction of fertility may follow closely after the rise of the seepage, and accumulate in the upper strata of soil in such quantity as to make the reclamation of the land a long and expensive process. The remedy is to provide drainage followed by irrigation. By the former the water table is lowered, and the irrigation water applied to the surface and descending to the water table is carried off through the drains. In this journey downward through the soil it carries the alkali in solution, and it is dis- CLASSIFICATION OF DRAINS 191 charged through the drains. The effort, therefore, must be to reverse the upward movement of water, and produce conditions by which it will move from the surface downward, carrying the salts with it. 2. Classification of Drains. With respect to their functions, drains may be divided into two classes: 1. Relief drains, or those furnishing ready escape for ground water to the most available natural drainage line, in order to lower the water table. They are generally built on the lowest available ground. 2. Intercepting drains, or those designed to intercept seepage waters between their source and the lands to be protected. They are often built on higher ground than the land they are designed to protect, but may also serve as relief drains for the lands above them. These two classes of drains are by no means distinct, and the two functions are often combined to some extent in both. With respect to their form, drains are of two classes: 1. Open drains are those designed to act as open channels, to traverse the water table and conduct the surplus water away. 2. Closed drains consist of tiles laid end to end in a channel in the water table and covered with earth, so that farming or other operations can proceed over the ground without disturbing the action of the drains. Where they will answer the purpose, closed drains are of course preferable, but their use is restricted by their limited capacity and their cost. Where the slope of the country limits the grade available for the drain to a very moderate amount, the tile drain, restricted by the size of the tile, carries only a small amount of water, unless the tile be made very large. The sizes most commonly used as main drains are 10 inches and 12 inches in diameter, but larger sizes up to 18 inches in diameter are sometimes employed. Above 18 inches in diam- eter the standard tile sometimes fails under the overburden of 10 or 12 feet of soil, and larger sizes than 18 inches are seldom used except when made extra heavy for this purpose, in which case they are very expensive. Where the capacity of an 1 8-inch 192 DRAINAGE FIG. 61. Excavating Trench for Tile Drain, Montana. FIG. 62. Dragline Excavator on Drainage Work, Idaho. DESIGN OF A DRAINAGE SYSTEM 193 tile is insufficient, it is generally best to build an open drain, if practicable. 3. Design of a Drainage System. The work of designing such a system of drains as to remove the menace of a high water table and of rising alkali, and to leach from the upper strata of soil the accumulations of alkali, in the most effective and economical manner, is generally complicated, and requires long and close study of the positions and movements of both surface and ground water over several years. Moreover, this study must continue until the construction of the drainage system has been practically completed, so as to note the effect of drains after they are in service, and correct any errors of assumption that may have been involved in the original plan. Every such plan should therefore be considered tentative, and subject to modifications as the work progresses. 4. Location of Drains. To decide the position and direction of the drains to be built, it is important to know the various sources of the seepage water, and also to know the surface topography and underground structure of the land to be drained. In the treatment of underground waters, page 45, it is shown that the flow of percolating water varies with the slope of its surface. Also that the movement of water on a given grade is many times more rapid through sand and gravel than through clay or loam having smaller openings between the particles. Hence, if a drain be located entirely in a fine-grained soil like clay, it can lower the ground water only a very short distance back from the drain; for no considerable quantity of water can travel through the clay soil except on a steep grade, and this brings the gradient quickly to the level of the water table. Therefore, if a drain is to be effective, it is necessary that it shall tap a stratum of sand or gravel, or at least some medium through which water can travel with reasonable velocity on a slight gradient. It frequently happens that a clay or loam soil needing drainage extends to a depth too great for a drainage ditch, and although the water table may stand several feet above the bottom of the ditch, it will drain only a few rods 194 DRAINAGE on each side owing to the steep gradient maintained by the percolating waters in the tight soil. In such case, relief is often found by boring wells at frequent intervals in the bottom of the drain until a coarser stratum is tapped, and in these wells the water rises from the open stratum into the drain and flows away. This draws on the ground water from a distance, and lowers the water table accordingly. Whenever such an open stratum is situated under an irrigated region, it receives the gravity water from the soil above, and conducts it down the slope frequently under tighter soils, and having insufficient outlet for all the water it can carry, accumu- lates pressure equal to the hydrostatic head of its source of supply minus the loss of head due to friction. Acting under this head, it percolates upward through the overlying clay and loam and waterlogs the land, which may not have been irrigated at all. This roughly describes many artesian basins, which are located in " cienegas," or swamps formed in this manner. The hydrostatic head may be insufficient to bring the water to the surface of the ground but ample to cause it to flow into the bottom of a drain if a well be provided as an outlet. The foregoing illustrates the need of a thorough knowledge of the subterranean structure of the country to be drained, in order that the drains may be so located as to take advantage of water-bearing materials that may be available to a properly located drain. It is important to build closed drains on as steep a grade as possible in order to increase their discharge capacity and to keep them clear of detritus. Whether a drain be open or closed it is usually desirable to give it all the grade available. In the case of the open drain, a good velocity tends to keep it scoured out, and to prevent the growth of aquatic plants which are the bane of drainage ditches. A sluggish velocity not only encour- ages aquatic growth, but it promotes clogging by other means. Tumble weeds often blow into the ditches, forming shoals where weeds can start, and sand or silt, either from dust storms or caving banks, accumulate in the ditches if the velocity be low, whereas a swifter current would carry out both weeds and silt. DEPTH 195 The small quantity of water usually carried by a drain and its rough perimeter make it seldom possible to give it grade enough to permit destructive erosion, and for these reasons it should generally be given all the grade available. For the same reasons it is desirable to avoid abrupt turns in the alignment of the ditch, and to avoid inverted siphons, and to give necessary culverts liberal openings, and in all respects to avoid sacrificing grade, or introducing structures which may promote obstruction by sand or floating debris. To obtain the requisite grade for the ditches it is generally necessary to build them in the direction of the greatest slope of the country. 5. Depth. The ground water on irrigated land should be kept 5 feet or more below the surface of the ground. To accom- plish this the bottoms of drainage ditches must be considerably lower, in order to make allowance for three principal factors: 1. The depth of water in the ditch when in service, which deducts that much from its drawing depth. 2. The gradient which the water table must assume to dis- charge its surplus water. 3. The inevitable decrease in depth of the ditch due to sloughing and accumulation of detritus. It often occurs that in excavating a drain sand is encountered below the water table, which under the influence of inflowing water oozes into the ditch, and it becomes impossible to excavate to the required depth without holding the banks by artificial means. This is the only remedy where tile drains are being placed, and greatly retards the work and increases the expense. Where such material is encountered in constructing an open drain, the best plan is to make the ditch as deep as practicable, and to go over it again a few weeks or months later. In the meantime the water table will have been lowered by the drain, and it becomes possible to make the drain considerably deeper, and perhaps deep enough, although sometimes a third effort may be necessary. 6. Capacity. One of the most difficult problems to be solved in designing a drain is to determine the necessary capac- 196 DRAINAGE ity which depends of course on the amount of water to be removed. No general rule can be given as a safe guide to the solution of this question. Some waterlogged lands yield very little water to drainage works. In other cases, where the soil is open where seepage from canals is large, and water is lavishly applied in irrigation, leading to heavy accretions to ground water, the land may discharge into the drains more than half of the water brought to it by canals. These conditions, moreover, may not be permanent. Canals which at first lose heavily by seepage may and often do improve with age by silting their channels, or they may be lined in the worst places to save water. Irrigators who apply water lavishly at first may learn the folly of this practice and use water more sparingly. All these conditions and possibilities must be taken into account in estimating the capacity of the drains. In the case of the open drain, which is sure to deteriorate, it is safe to make its capacity liberal and let it suffer deterioration to the necessary capacity, thus saving in maintenance costs. If provision is made in advance for future enlargement this is easily accom- plished with open drains, so that foreknowledge is not absolutely essential. Not so with closed drains. If the tile is not large enough to discharge the necessary water, it cannot be enlarged without entirely rebuilding the drain. If it is too large considerable extra expense is wasted, but as this is much less serious than if too small, it is best to make the capacity liberal. The bottom width of an open drain should be fixed according to the required capacity with due allowance to rough construc- tion by machinery so that its coefficient of friction is large. A factor of roughness in the Kutter formula, # = .03, is about an average for new ditches, but to preserve such a factor the main- tenance must be fairly well cared for. 7. Form of Tile. The best form of tile used for drainage purposes is the vitrified clay tile, cylindrical, without the bell mouth employed for sewers. These tiles are laid end to end as close as possible, and a strip of tar paper 3 inches wide, with a length one-half the circumference of the pipe, is laid over each MANHOLES 197 joint to prevent the entrance of sand which might clog the tile. The water can then enter the joints below the horizontal diameter. A board of a width nearly or quite as great as the diameter of the tile should be laid in the bottom of the trench to keep the tiles from settling out of line. As the tiles are laid, it is well to pack some earth against them to hold them in line horizontally until the trench is backfilled. If the drain is laid in quicksand it is best to use a better foundation than the board above described. This may con- sist of two pieces of 2 inch by 4 inch lumber spaced parallel with a space between about half the diameter of the tile, and nailed together by three or four cross-pieces, forming a ladder. This is laid in the trench with the cross-pieces underneath, and the tiles are fitted into the space between the sides of the ladder which holds them in place both horizontally and vertically. When convenient it is best to allow the tiles to remain in place a few days before backfilling, and to inspect them to see that they have not become displaced. The backfilling should be performed carefully so as not to displace the tiles, and where a choice is possible, it is well to place the coarsest material available next to the tiles. Any tile drain is improved by placing gravel next to the tile before back- filling. 8. Manholes. At intervals of about 100 feet it is advisable to provide an open well to serve as a manhole. This can be lined with lumber, and the drain from above can discharge into the well, and the lower drain carry the water away. These wells have several uses. They may serve as sand traps, to catch any sand that may be traveling down the drain which might clog it. For this purpose, the bottom of the well should be 2 or 3 feet below the grade of the drain, and should be kept cleaned out. The well should be at least 3 feet in diameter so as to permit a man to work in it. Such wells serve to show whether the drain is operating under a hydrostatic head, in which case the water will stand in the well higher than the top of the tile. Such a well should be placed at any point where 198 DRAINAGE the grade of a drain changes in such a way as to check the velocity of the drainage water, for at and below such critical points there is a tendency to deposit sand, and it is desirable to remove this by means of the well. In case of a broken tile or other derangement of the drain, frequent manholes assist in locating the trouble. Where the slope of the ground changes, making it necessary to reduce the slope on which the drain is laid, the size of the tile should be increased so as to give it at least a greater capacity than the portion of the drain above. Such a change is most conveniently made at a manhole. The manhole or well is a convenient loca- tion for a weir to measure the discharge of the drain, a record of which should be carefully kept, as it is of great value in denoting the action of the drain, and its effect on the ground water. 9. Wooden Drains. Where earthen drain pipe is very expensive on account of freight charges, and lumber can be cheaply obtained locally, wood has been used instead of clay tile. The economy of this is generally doubtful, unless it is cer- tain that the wood will be continuously saturated. Otherwise, its early decay will require its replacement so soon as nearly or quite to neutralize its advantage in low first cost. Where wood is used, it may be formed into a square box, of such length as convenient, and if the box is large, the top should be laid with the grain transverse to the length of the drain, to give it the required strength. Each board forming the top should be slightly gained at each end, so that it will fit to the sides, and prevent their collapse from lateral pressure. A similar precau- tion may be taken with the bottom, so that little dependence need be placed upon nails to hold the parts of the box in place. The bottom should break joints with the sides, to preserve the alignment. 10. Cement Drains. In some cases cement pipe may be cheaper than clay tile, and it answers the purpose well unless alkali is present. If the soil contains much alkali, especially sulphates, there is danger of the cement pipe disintegrating especially if not running full continuously. CEMENT DRAINS 199 The U. S. Bureau of Standards in cooperation with the Reclamation Service has made a series of tests on the use of cement pipe as drain tile, exposed to soils containing alkaline salts, and draws these conclusions: 1. The use of cement tile in soils containing alkali salts in large quantities is experimental. 2. Porous tile due to the use of lean mixtures or relatively dry consistencies are subject to disintegration. 3. Some dense tile are under certain conditions subject to surface disintegration. 4. Disintegration is manifested by physical disruption caused by the expansion resulting from the crystallization of salts in the pores and by softening, resulting from chemical action of the solutions with the constituents of the cement. 5. While results obtained will not permit of a definite state- ment as to the relative effect of the various constituents of the salts, indications are that the greater the quantity of sulphate and magnesium present and the greater the total concentration of salts the greater will be the disintegrating effect. 6. Tile made by the process commonly used, which allows the removal of forms immediately after casting, are subject to disintegration where exposed to soils or waters containing TO per cent or more alkali salts similar in composition to those en- countered in this investigation. 7. The hand- tamped tile of plastic consistency as made in this investigation are not equal in quality to machine-made tile of the same mixture, and they do not resist alkali action as well. 8. Steam-cured tile show no greater resistance to alkali action than tile which are cured by systematic sprinkling with water. 9. Tile made of sand cement have less resistance to alkali action than the tile made of Portland cement of the same proportions. 10. The tar coating as used is not effective in preventing the absorption of alkali salts from the soil. 12. No advantage is found in introducing ferrous sulphate into the cement mixture. 200 DRAINAGE If cement drain tile are to be used in alkali soils or waters containing o.i per cent or more of salts they should be made of good quality aggregate in proportions of not less than one part Portland cement to three parts aggregate. The consistency should preferably be quaking, which has proved the most resist- ent of all mixtures used. ii. Drainage Works of the U. S. Reclamation Service. TABLE XXVIII. OPEN DRAINS COST Project Mites Cu. Yds. Acres Per Mile Per Cu. Yd. Per Acre Boise Alinidoka 130.0 108 o 5,533,002 3,367018 64,680 72,000 $5281 6143 $-067 ill $10.58 22 Yuma North Platte. . . . Carlsbad 16.8 23o 11.7 375,ooo 410,640 292,248 8,000 2,900 4,320 7650 4000 6336 .250 . 140 .255 I4.OO 30.00 17. 2S Rio Grande Umatilla 22.8 IO.O 865,300 225,000 6,000 2,000 8815 5481 115 2 44 16.00 27.40 Klamath Shoshone Huntley 77-5 13-5 13 . 2 972,000 486,500 504,150 17,400 2,000 19,400 3718 72OO 7630 . 2OO 174 I 5 16.50 26.50 16. 25 TABLE XXIX. CLOSED DRAINS Project 8 INCHES 10 INCHES 12 INCHES Length, Feet Unit Cost Length, Feet Unit Cost Length, Feet Unit Cost Yuma I Huntley 11,470 $0.97 22,089 3o50 15^50 17,107 . 89,334 Si. 37 i-39 1.46 0.98 1.14 99,217 39,838 4,445 25,661 151,428 $1.44 1-39 1.62 1.04 i. 20 North Platte Carlsbad Klamath Shoshone Total 11,470 $0.97 147,330 $1.27 320,589 $i-34 DRAINAGE WORKS OF THE U. S. SERVICE TABLE XXIX. CLOSED DRAINS Continued 201 Project 15 INCHES 18 AND 20 INCHES Total Cost. Length, Feet Unit Cost Length, Feet Unit Cost Yuma Huntley 5,525 ioi,935 31,102 $1.50 1 .46 1-39 15,400 13,635 $I. 7 I i-37 $34,597 358,893 126,104 44,013 43,452 460,940 North Platte Carlsbad Klamath Shoshone. . . 90,275 i-3i 60,586 1.44 Total 228,837 sSi-45 89,621 $1.50 Remark: Average cost of closed drains in table $1.35 per foot. REFERENCES FOR CHAPTER XII KING, F. H. Irrigation and Drainage. The Macmillan Company, New York. DAVIS, ARTHUR P. Irrigation Works Constructed by the United States. John Wiley & Sons, New York. HART, R. A. Drainage of Irrigated Land. Bulletin No. 190, Office of Experiment Stations. TANNATT AND KNEALE. Seepage and Drainage. Bulletin No. 76, Montana Agricultural College, Bozeman, Montana. Engineering Record. Cost of Excavating Drainage Ditches with Steam and Electric Machines. Vol. LXX, No. 26. YARNELL, D. L. Trenching Machinery used for Construction of Trenches for Tile Drains. ELLIOTT, C. G. Drainage of Farm Lands. Farmers' Bulletin No. 187, U. S. Office of Experiment Stations. CRONHOLM, F. N. Drainage System for North Side Minidoka Irrigation Project. Engineering Record, April 15, 1914. MURPHY, D. W. Drainage of Shoshone Irrigation Project. Engineering Record, June 6, 1914. BURKHOLDER, J. L Conserve your Little Drop of Water and Help Keep Down the Peak. Reclamation Record, December, 1917. CHAPTER XIII CANALS AND LATERALS i. Capacity. To decide upon the necessary capacity of an irrigation canal, it is necessary to know approximately the three main factors which control : 1. The acreage of land to be served. 2. The duty of water. 3. Seepage losses to be expected. Unless great care is exercised in considering each of these factors and conservative estimates are made, much danger exists of serious error in the determination of each one. The principles upon which decisions must be based are given in the preceding pages. The data for such decisions are not accurately determinable in advance, and careful consideration must be given to the margin of safety to be allowed to guard against unavoidable errors both in the data and the conclusions drawn from them. Having determined the three factors above listed, the capacity of the canal may be conveniently found by the following formula: Let c = capacity required in cubic feet per second; a = area to be irrigated in acres ; d = average depth of water in feet required on the land in the 15 days period of maximum use; p = percentage of loss by seepage and evaporation. Remembering that a stream flowing at the rate of i cubic foot per second carries 29.7 acre-feet of water in 15 days, we have ad I p\ c = i- -I (i) 29. 7 \ loo/ Example : Required the capacity at head of main canal, necessary to serve 10,000 acres of land, where the maximum requirement 202 CAPACITY 203 of crops for a 1 5-day period is an average depth over the irrigable area of .3 foot, and the losses in canals when operating at full capacity will be 20 per cent of the water diverted, or a =10,000, d--3, p = 20. Then by (i) .3X10,000 3,000 5 = 7 = 126.26. 29.7X80 23.76 In the design of the canal some excess capacity should be pro- vided to allow for possible errors in the assumptions which must be made from uncertain data. Excess capacity is not wasted, for a canal begins to deteriorate as soon as built. Wind, rain, frost and the trampling of animals work the banks down and tend to fill the canal with dirt and trash, and the capacity thus gradually diminishes unless restored by annual repairs. This is especially true where the water contains much silt. In such cases, it is always best to provide considerable excess capacity so that a substantial lining of silt may be allowed to remain in the canal, as this not only saves the cost of removing the same, but improves the canal by rendering it less pervious and decreasing its coefficient of friction. Unless such excess is allowed, especially in laterals, the silting may so decrease the capacity as to make it impossible to deliver sufficient water for the needs of the crops while it may be impossible to close the canal for cleaning without heavy loss to the farmers requir- ing the water. The requirement for a large excess capacity is most advisable on the small laterals, where the tendency to deposit silt is often great, and where the cost of constructing such excess is generally small. It may sometimes even be advisable where water is very silty to build the laterals of two or three times the capacity absolutely necessary for service, and allow them to accumulate silt until the capacity diminishes to that required, as this is both better and cheaper than frequent removal of small quantities of silt. Larger quantities can be removed at a lower unit cost. 204 CANALS AND LATERLAS N = 0.2o V=2.95 S=.OC017 Q=1418 ^ -45;5- N = 0.25 S =.00016 V = 2.87 Q = 1415 Scale of Feet 15 15 30 45 FIG. 63. Cross-sections of Interstate Canal, North Platte Valley, Nebraska. DESIGN 205 2. Design. The problems of canal design and location may be divided into two general cases: 1. Cases in which the water supply is greater than the avail- able land, making it necessary to give the canal the least practi- cable grade, in order to command by gravity canal the maximum area of land, or to reach a sufficient area without undue length of canal. 2. Cases in which the area of good land readily commanded by the canal is in excess of the available water supply, or the configuration of the country is such that abundant fall is available. Where it is very desirable to save grade, as in case i, the canal should be given a section such that it will have a large hydraulic radius, and hence have a reasonably high velocity on the gentle grade given. In a rectangular channel, the hydraulic radius, and consequently the velocity, is a maximum when the depth of water is one-half the width. A rough rule for trapezoidal channels is that the depth should be about half the bottom width, to give maximum capacity, but this rule is generally modified by considerations of economy of construction and operation, which require less depth and greater width, except on side hills; especially is this true of large canals. The advisable section lies somewhere between the cheapest section and the one affording the highest velocity. It must be deter- mined in each individual case by a consideration of all details affecting the problem, such as the value of the land to be gained, . and whether the water carries silt, making a good velocity necessary to prevent silting of canals. In the second case cited where ample grade is available, it is generally desirable to give the canal as much velocity as the earth will stand without erosion, and where rock, gravel, or hardpan must be excavated economy may often be promoted by increasing the grade and velocity of the canal so as to reduce the cross-section and thus save excavation. It should be remem- bered, however, that in such places there is often danger of seepage through the seams of the rock or gravel, and where velocities are high it becomes impossible to close such crevices 206 CANALS AND LATERALS by the process of silting, and it may be necessary to line the section with concrete, in which case a further increase of velocity due to the greater smoothness is secured, and the cross-section may then be further reduced. In fact where it is necessary FIG. 64. Canal Cross-sections for Varying Bed-widths. to cut through rock for any great distance the cost may often be reduced by lining the cut with concrete, which so reduces the friction that the higher velocity permits a reduction in cross- section sufficient to save the cost of lining. This is especially the case with deep cuts or side hill location. SIDELONG GROUND-W.L. ABOVE G.L. 6'0" vr 46 GTround May require Puddle Wall as indicated SOD REV.EJMENTS WITHOUT BERMS-W.L BELOW G.L. W.L-- Level WITH BERMS-W..L. BELOW G.L. Ground FIG. 65. Various Canal Cross-sections. In the construction of earthen canals, economy requires that embankments be utilized to assist in forming the waterway, and the most economical form is that in which the excavation is sufficient to form the embankment with a small allowance for wastage and shrinkage, usually assumed about 10 per cent for small canals, and 5 per cent for large ones. On level or gently DESIGN 207 sloping ground, a wide and shallow canal in which excavation equals embankment is, for a given cross-section cheaper than a narrower and deeper one. It has a greater perimeter and less hydraulic radius, and hence requires more grade for a given velocity, but if this is available a wide canal may be advisable. This, however, introduces another element that must be studied. In general the seepage from a canal is roughly proportional to the wetted area, and therefore in uniform material more seepage may be expected from a wide than from a narrow canal. If the material is naturally porous, this result may be emphasized, FIG. 66. Rock Cross-section, Turlock Canal. for in such cases, an artificial bank can often be made tighter than the natural material, and the narrow canal with its greater proportion of embankment may be tighter than the wide one. Local conditions, however, may greatly modify this result. It often happens that the upper soil which contains loam is better adapted for making a tight waterway than that which underlies it, and the narrow canal with its deeper cut may expose a coarse gravelly subsoil, into which seepage may be so rapid as to overbalance the decreased surface of percolation. For these reasons it may be advisable to adopt varying types of cross-section on different parts of the same canal in accordance with the soil and subsoil conditions. On nearly level ground a given canal cross-section requires less excavation if wide and shallow than if narrow and deep. 208 CANALS AND LATERALS A given amount of material is required for the formation of banks of a certain height, and the wider apart these are placed the greater the cross-section of the waterway. Where the location is on a side-hill slope, this rule does not obtain, as the difference in elevation between the two sides of the canal requires a high bank on one side and none on the other. Further widen- ing requires a still higher bank on the lower side, and a heavier cut on the upper side, so that on hillsides, the narrow, deep section is generally cheaper, and this is the more emphatic as the hillside becomes steeper. Where the side hillside slope is very steep, the slope of the canal section will intercept the surface ry Rubble SECTION IN ROCK =37.7 P = 15.4 r= 2.44 W=.012 s =.00124 U=7.96 Q=SCO A B FIG. 67. Rock Cross-section; Umatilla Canal. slope of the ground at some distance above the canal, and to prevent excessive cost it becomes necessary to make the canal slopes as steep as possible and in extreme cases to make them of the character of a masonry retaining wall. At the same time it may be advisable to make the lower bank of earth on the usual slopes, giving rise to cases where the two sides of the waterway have different slopes. The economic section will depend also, to some extent, on the character of the material to be excavated. In hard rock the cost of excavation makes yardage predominant, and a lined channel is generally economi- cal. In open or porous material, the area exposed to seepage is important, and may require the minimum attainable wetted perimeter. DESIGN 209 Where the water to be carried is clear, and growth of aquatic plants is to be anticipated, the deeper canal has advantages, because less likely to permit the growth of such plants. They require bright sunlight, and deep waters shade the bottom of the canal too much for their fullest development. Large canals on nearly level ground are sometimes con- structed with a berm, or level width of natural ground between the excavated channel and the banks. This has the advantage of affording a shallow section and therefore low velocity next to the banks and less tendency to erode them, but this also encourages the growth of weeds and aquatic plants, and the provision of berms is not usually advisable practice. The side slopes of canals in earth should be made somewhat flatter than the natural slope of repose of the material, in order to add to their stability and diminish their tendency to slough and to work down the slope. Slopes of two horizontal to one vertical are common, and are good practice in average ground. Banks of sandy soils are sometimes made flatter, and very firm soils may be left steeper, especially in cut, which may some- times retain stability on steeper slopes than the same material requires in embankment. In deep cuts economy demands that the banks be left as steep as safety will permit. In loose sand and gravel this is about i| horizontal to i vertical, being very little flatter than the angle of repose. Firm clay may stand much steeper than this, as may also indurated material of all kinds. Fairly firm rock will stand practically vertical, except in very deep cuts, and between this limit and the slope given for sand, all other materials find their safe slopes. The top width of canal banks should vary with the size of the canal. Where large canals follow nearly on contours, with higher ground on one side, and lower ground on the other, the upper bank may be rather light, as its rupture will not threaten serious damage, while the lower bank must be made much heavier to give necessary security against disastrous breaks. It is generally advisable to make the lower bank of a large canal wide enough to form a wagon road. This facilitates the patrol of the canal, saves other land necessary for such a road, and 210 CANALS AND LATERALS adds stability and security to the canal. Such a road should not be less than 10 feet in width, and a greater width is better, especially in light sandy soil. Turnouts for passing teams should be provided, which can be done without extra expense at points where excess cut furnishes considerable surplus material. The lower or main bank should be at least 3 feet above the water level of the canal in large canals, but may be less in small canals. The lower bank of the canal must be carefully built, and if the excavated material available for canal building is coarse, care must be taken to place such fine material as it contains on the water slope, and the coarser material on the outside. If not enough fine material is found in the canal prism for this purpose, it may be necessary to haul clay or loam from a distance for this purpose, or in some cases it may be advisable to line with concrete. A bank of coarse gravel or broken rock on a good foundation is an ideal bank, provided the water slope is made practically impervious with clay or otherwise. Cross-section with Subgrade. In light soils 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 center 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. 68) is given by practically designing the canal as if it were to have a trapezoidal cross-section with berm, and then evening off the slope by removing the berm and contin- uing the slope from the bottom of the canal toward the center. It is sometimes necessary to locate a conduit, along a steep hillside, where the material naturally lies about the angle of repose, so that the excavation of a canal would so weaken its support as to cause such a tendency to slide that the canal would be unsafe. Several alternatives are then presented. 1. To excavate a bench and build a flume upon it. It may be that this will too greatly weaken the hillside, and invite sliding, especially in the presence of the water of the canal. 2. Without disturbing the natural material, build a flume DESIGN 211 on a trestle, elevated sufficiently to permit rolling rocks to pass under. If this flume is to be of concrete, it would be expensive. If of wood or steel, it would be rather short lived. 3. A pipe may be built and buried, leaving the slope in its original condition. This would be the safest, but most ex- pensive of the solutions, and might be prohibitive. FIG. 68. Cross-section of Galloway Canal in Sand, showing Subgrade. 4. A compromise among the above alternatives sometimes adopted is to excavate a bench and build thereon a concrete flume with sufficient strength to support the upper bank like a retaining wall, and thus restore the support to the slope, without involving as heavy expense as the pipe in solution 3. The lined canal or flume in the Tieton Canyon of Washing- ton may be classed as a case of this kind. Fig. 70. This flume FIG. 69. Typical Section of Lined Canal. is of circular section, with a segment cut off the upper part, and concrete chords provided to restore its rigidity. The cir- cular section and the chords were both reinforced. They were manufactured in 2-foot sections in the bottom of the canyon, where ample room and materials were available, and were hoisted to place and joined in a continuous flume in place by cement joints. Where stretches of lined canal are on a very steep grade the water assumes a correspondingly high velocity, and measures to destroy this velocity may be necessary at the foot of the steep grade, and it may also be necessary to provide a regulator 212 CANALS AND LATERALS at the upper end, to shut out the water at times. Such a com- bination is called an inclined drop, or chute. It is, of course, located at the point where the necessary fall can be compressed into the shortest practicable distance. It consists essen- tially of an inlet structure, a trough to conduct the water down the hill, and a pool at the bottom to receive the water and destroy its c,ccumulated energy. The inlet structure forming the transition is provided with splayed wing walls, and well equipped with cut-off walls for the wing walls, floor and sides, to prevent percolation of water along the structure. At the lower end, where the water enters the trough, it is provided with con- trol gates. The trough converges to a narrow channel a short distance below the gates, to correspond to the increased velocity, which may reach about 40 or 50 feet per second, the section again increasing as it approaches the pool at the bottom. Cut- off walls are provided under the trough at frequent intervals to prevent erosion by leakage or rain water. These are generally i foot deep, except at expansion joints, where they are deeper. 3. Alinement. Owing to its moderate velocity, the alinement requirements of canal location are not so rigid as in railroad work. Location upon the contour that will keep the cut and fill in ap- pr ximate balance is generally the cheapest per foot, but on rolling ground this may make the line so crooked as to intro- duce excessive curvature and to increase the length to such an extent as to actually increase the yardage excavated, over a less tortuous location. On curves there is always a tendency to erode the bank on the convex side of the canal and unless the velocity is very low this must be carefully provided for. Where the convex side is an embankment, as when passing around the end of a ridge, it is generally best to throw the location into cut in order to resist the tendency to erode, and this will also eliminate part of the curvature. This will shorten the line, im- prove the alinement and make a safer location, and accordingly some increase of cost can be justified. A great variety of rules have been suggested concerning curvature limits, but these are of little value, as the limits must be determined by circumstances above discussed. A straight alinement is best, but curvatures A LI N EM EN T 213 can be introduced to almost any extent demanded by economy, and not prohibited by safety. Various rules have been proposed, limiting the curvature to certain relations to the width or depth of the canal, but these 2-^"corr. bars ""- 10 (fig. STANDARD TUNNEL SHAPE S.ECTION D-D FIG. 70. Tunnel and Canal Sections, Tieton Main Canal. appear illogical as the erosion will depend not so much upon the width nor the depth, as upon the velocity of the water, next to the bank. It is true that the larger the volume of the flowing water, the greater the difference between the maximum and min- 214 CANALS AND LATERALS imum velocities, and on curves the maximum tends to approach the bank on the outside of the curve, and in this way to increase the liability to erosion. This tendency increases as the curva- ture increases, and also as the velocity increases. Any rule for curvature must, therefore, recognize all these influences, the greatest of which is the velocity. Different materials resist erosion in differing degrees, and any rule fitting average earth must be modified for lighter or heavier soils. For average loam soils, the following is a safe formula: R=V 2 \/A+40. In the above equation R = Smallest permissible radius of curvature of the center line of canal on exterior curves, expressed in feet; F = The mean velocity of the stream, in feet per second; A = The cross-sectional area of the stream in square feet. The constant, 40, insures a radius exceeding 40 feet under all circumstances, however small or sluggish the canal. A canal having a mean velocity of 2 feet per second may have a curvature radius one-half that of one with a mean velocity of 2.83, since the squares of these velocities are 4 and 8 respectively. Shorter radii may be used on interior curves, and in firmer material, but the radius should be made longer in very light soils easily eroded, and where a break in the canal would be especially disastrous, as on steep side hills. The tendency to erode the bank on the outer side can be counteracted to some extent by a superelevation of the bottom of the canal, or in other words, deepening the canal on the inner side of the curve and making it shallow on the outer side. This tends to keep the thread of maximum velocity from the outer bank. If very sharp curvature is necessary, the outer bank can be protected by a blanket of gravel, or in extreme cases by rip-rap of brush or rock. Very sharp curvature increases the friction on the banks, and may require a slight increase of grade to compensate, but the amount of this is not accurately known, and for moderate or low velocities is practically negligible. VELOCITY 215 For high velocities some compensation for sharp curvature must be made, varying with the roughness of the channel. Where the rolling character of the country requires heavy cuts through ridges to prevent an excess of curvature, the same reason suggests fills across low places to utilize the excavated material, and further straighten the alinement. But while cutting the ridges increases the safety of the canal and reduces maintenance charges, the construction of high fills has the opposite effect, and may be a serious matter in countries where the banks are attacked by burrowing animals. In such cases, therefore, there may be an excess of excavated material which cannot be utilized, both for the above reason and the long hauls that its utilization may involve. Where the above circumstances afford a latitude of choice, it is generally advisable to make two or more preliminary loca- tions and compare their estimates of cost, considering at the same time the relative safety and alinement of the several locations. Where one location is undoubtedly safer than another, considerable expense may be justified to secure such safety, especially on large canals, not only on account of the cost of maintenance, but also the security of the water supply where a break in a large canal may do great damage directly, and indirectly involve loss of crops. 4. Velocity. The velocity given a canal must not be so great as to involve destructive erosion to the channel, as this will increase the difficulty of diverting the water into laterals for use, endanger the foundations of bridges and other struc- tures, and sometimes by progressive cutting of banks destroy fertile lands. The eroded material will be largely deposited at points where the velocity slackens, and the regimen of the canal will be thus deteriorated. It is, however, desirable for many reasons to give the canal as high a velocity as possible without destructive erosion, if the necessary grade is available. Such a velocity will tend to prevent the growth of aquatic plants, and the deposit of silt and trash in the canal, and the necessary water can be carried in a smaller canal if the velocity is high than if it is low. 216 CANALS AND LATERALS The maximum permissible velocity depends on the resistance to erosion of the banks of the canal, which varies widely with different materials. Where these are composed largely of clay, they may have a considerable adhesion and consequent resistance to erosion, and any loosened particles in suspension are easily transported by a velocity that will not attack the mass of clay in the bank. With fine sand or silt the margin is not so great, and it becomes a problem of some difficulty to select and attain the velocity which will transport all the silt in suspension with- out cutting the banks. When such a velocity is found for the canal running at full capacity, trouble may be encountered when the canal is operated at part capacity, when of course the veloc- ity is diminished, and the tendencies characteristic of low velocities are all increased. For this reason it is important to secure the highest velocity that will not erode the banks, and even to provide considerable protection at curves to prevent destruction of banks by erosion. The reduced velocity at part capacity causes canals carrying silt-laden water to deposit silt when running part full, and as this may be of frequent occur- rence such canals are often badly silted and require much clean- ing. For this reason a canal which is to carry muddy water should generally be constructed with considerable excess capacity, so that a moderate amount of silting may be endured without embarrassment, and the cleaning postponed till the winter season. It is well, also, to permit some silt to remain permanently in the canal because of its tendency to close the crevices and pores of the soil and reduce seepage losses from the canals and laterals. A thin lining of silt also increases the dis- charge of a canal by forming a surface smoother than the original, and decreasing the friction of the water upon its conduit. Very few soils, unless indurated or gravelly, will resist a higher mean velocity than 3 feet per second, and it is ordinarily necessary to keep the velocity considerably below this. Most soils will safely stand a mean velocity of 2 feet per second, and a general rule is that velocities in earth should be somewhere between these extremes, varying with the character of the soil and the requirements for grade, and also with the depth of the canal. LATERAL SYSTEMS 217 The erosive power of a current depends not upon the mean velocity of the stream, but upon the velocity of the film of water around the perimeter of the prism. This is greater in proportion to the mean velocity in shallow than in deep canals. It follows that deep canals will stand a higher mean velocity than shallow canals in the same material. 5. Lateral Systems. Every large canal system ramifies throughout the land to be irrigated somewhat like the branches of a tree. Beginning with the main canal, this follows the upper edge of the land to be irrigated, except in cases where the water is to be pumped to still higher tracts. It may proceed some distance before it reaches any irrigable land. When it does, the land may be in a narrow strip which can be irrigated from a single tap box or two in the side of the main canal, but eventually a wide tract is reached which requires the diversion of a large lateral, to carry a considerable body of water to a large area reaching some distance from the main canal. Such a lateral must also be located on high ground with reference to the land which it will serve, and must send off branches located also on relatively high ground. On typical rolling ground where the normal system of natural drainage depressions occur, the lateral system follows a rule generally the reverse of the general drainage system. That is, the main canal cutting across the country drainage sends out a main lateral down each main ridge, and this lateral sends out smaller laterals down the subordinate ridges, from which sub- laterals diverge on each side. Thus, every ridge is crowned by a lateral and bounded on each side' by a ravine, or depression. The rules for locating a lateral system on such land are rela- tively simple as above indicated, but the system itself may be complicated and difficult to design, construct, maintain and operate. The topography may require a large number of sub- laterals to follow each ridge, with a corresponding number of turnouts and tap boxes. Each farm must have at least one tap- box to deliver water at the highest point of irrigable land, from which it can be led by gravity to lower ground. If the individual farm is cut by a ravine a second turnout may be needed, on the 218 CANALS AND LATERALS opposite side of the depression, and conditions may be such that several of these may be required on a farm of moderate size. The slopes also may be so great as to induce destructive veloci- ties unless drops are introduced, and in some systems hun- dreds of these are required. Such a system will also have numer- ous drainage crossings of various forms. All these add to the complication and expense in design, construction, maintenance and operation, and demand immense and intense preliminary study of the numerous alternatives which will present them- selves. These can be made most efficiently and economically FIG. 71. Diagram Illustrating Distributary System. on an accurate topographic map of the entire irrigable area of suitable scale and contour interval. From this conventional topographic condition, with a defi- nitely marked system of natural drainage, we have all shades of variation to the smooth alluvial valley with two main slopes, one down the valley, and one normal to this, toward the stream. With such smooth topography, on moderate slopes, the distri- bution system is greatly simplified and cheapened as compared with that on more rolling country. In rare cases the slope may be insufficient to furnish the necessary fall for economical gravity irrigation. An illustration of such a case is the Minidoka Project of the U. S. Reclamation Service, where in order to obtain and keep the requisite slopes for the gravity canals, it was neces- sary to build a diversion dam 46 feet high, and to build most of LATERAL SYSTEMS 219 the canals and laterals between high banks constructed from borrow pits, so that the water surface is held high above the adjacent country, thus giving slope to make the water run over the surface of the fields. Such instances, however, are rare, as most irrigable tracts have ample slopes, and excess slope is far more common than deficiency. The smoothest valley, appearing to the eye to be absolutely level, generally has slope enough for gravity irrigation, and may even have an excess. Perhaps the most difficult type of land surface to supply with a distribution system is that of eolian origin, where the sur- face, originally a series of sand dunes and depressions, may be modified by time but still maintains the character, and is under- lain with a subsoil coarse enough to absorb the meager rainfall promptly, and no surface drainage system is formed. Such a topography, with its low hills and hollows without law or system, presents peculiar difficulties to the topographer, and especially to the engineer designing a distribution system. Many of the shallow depressions are bowls or sinks without sur- face outlet, and many of the low mounds are isolated and can be reached by the laterals, if at all, only by means of high fills, or by pressure pipes to carry the water across low ground. The studies necessary for planning a system for such lands require a good topographic map with less vertical interval between con- tours than most other classes of topography require, and such a map, though expensive, is imperatively necessary. The shallow depressions in this class of land, having no outlet, may become swamps or ponds from the accumulations of surface drainage or the rise of ground water, or both, and the lowest parts of such bowls should generally be excluded from the area classed as irrigable. Many of the isolated elevations will be too expensive to reach, or the long fills necessary may be too burdensome in mainte- nance, and it is then best to eliminate them, or to postpone their development until land values have increased enough to justify their reclamation. It should never be forgotten that canals running on high fills present especial hazard and expense in main- tenance. Not only may they be subject to slides, especially if 220 CANALS AND LATERALS of clayey material, but they are the favorite haunts of burrow- ing animals, and incipient breaks have such head of water that they rapidly enlarge, and become disastrous. 6. Design of Laterals. In cross-section, laterals should usually have a greater depth in proportion to width than larger canals. This reduces the area exposed to seepage and evapora- tion and economizes in drops, bridges and other structures. It gives better hydraulic conditions for economizing grade, which may be important in level country. It also gives less encour- agement to the growth of weeds on the margin and of aquatic plants on the bed of the lateral. In any canal through arable soil, vegetation is sure to grow along the margin of the water, and this gradually encroaches on the waterway, affording a lodgment for sand and silt that may roll down the bank or be carried there by the water or the wind. Thus, gradually a turf is formed, building farther out into the canal, protected by the roots of the grass and weeds growing upon it and forming a new bank steeper than the original below the water surface with a berm just above. Where ample capacity has been pro- vided, this may be a desirable development, as it furnishes a berm to catch the material that may ravel from the bank, and has no injurious effects on the waterway if not carried too far, and if care is taken to prevent the development of noxious weeds thereon. This tendency to steeper banks shows the fallacy of giving lateral sides especially flat slopes for the sake of stability. Such slopes are often made as steep as 45 degrees or steeper, and it may be difficult to maintain them much flatter, even if this were desirable. For the sake of stability previous to the development above described, it is necessary to provide side slopes not steeper than 1 1 to i or about 38 degrees from the horizontal, and not flatter than 2 to i, or 30 degrees from the horizontal. The height of banks above the surface of the water in the lateral will vary with conditions. Where the lateral is in fill, the freeboard must be greater than in cut, and where banks are of light, loose material, liable to wind erosion, they must be higher than in clay or gravel. A high freeboard is not so impor- CAPACITY OF LATERALS 221 tant where the banks are thick and heavy as where they axe thin. In any case they should have some allowance for shrinkage and wear down, and still be high enough to be safe against over- topping with the most extreme use to which the lateral can be subjected. The top v/idth of banks of laterals, should vary from about 3 feet for small laterals, to 5 or 6 feet for the large ones. Above this, it is generally best to make at least one bank wide enough for a roadway, at least 10 or 12 feet, but this is advisable only for the largest laterals or main canal. As the science of irrigation develops, and as the value of water advances, it is becoming more and more common to line lateral systems, especially when located in porous soil such as sand or gravel where seepage losses would be heavy without such lining. In such cases, pipes may be freely used where the grade is abundant without excessive cost, and with important saving in maintenance. Lined canals may and should have greater depth, less bottom width, and steeper side slopes than unlined, as these differences are necessary to economize in the labor and material of the lining, and also increase the velocity obtained which is generally desirable in a lined canal, as tending to keep it clear of sediment and vegetation. 7. Capacity of Laterals. The capacity of laterals is affected by several considerations, the main one being the acreage to be served. Of course the larger the tract, the larger the lateral necessary to serve it, but the ratio is not constant. A small tract is more likely than a large tract to require irrigation all at once, and hence requires a relatively larger lateral. Laterals should in general have a capacity not less than 10 second-feet, as such a quantity may be necessary for economical irrigation at one time for a single irrigator. Lateral capacity should never be less than i second-foot to every 60 acres served', nor less than 10 second-feet. Between these limits a rough rule is: where c = capacity of lateral in second-feet, and a = area to be irrigated in acres. 222 CANALS AND LATERALS Where irrigation water carries much sediment likely to settle in laterals, it is necessary to allow a large margin to permit the use of the lateral throughout the season without shutting off the water for cleaning it. This margin is not included in the above rule, but must be added to the value of c, obtained from the for- mula. In the case of the Imperial Valley, California, where irrigation is required twelve months in the year, and the irrigation water is loaded with silt, an irrigation engineer experienced in its man- agement advocates building the lateral system in duplicate, so that one system can be used while the other is being cleaned, and irrigation water can be delivered without interruption. This, however, would require some provision for carrying water from one lateral across its duplicate, and the complications involved would hardly be justified. It is generally possible to close a lateral for a time in the slack season, which varies somewhat with the crop, but generally occurs in winter, so that cleaning may be accomplished without detriment to the crops. Various mechanical devices have also been invented by which laterals may be economically cleaned without turning out the water, and this subject will be more fully treated under the head of " Maintenance," page 518. What has been said, however, clearly shows that considerable excess capacity of laterals is a .great advantage, and is never a bad investment where sediment is carried in the irrigation water. 8. Location of Laterals. Laterals must be so located as to deliver water to the highest point of irrigable land on each farm unit, and their number and distribution will hence depend in some degree upon the probable size of farms. Where the topography will permit, they should follow property lines so far as possible, for thus they cause the least inconvenience, and give the greatest service, by reaching the maximum number of hold- ings. In smooth valleys it may be possible to run a lateral down each section line, thus conforming to legal subdivisions of the land, and probably farm units. It is not always desirable, how- ever, to place lateral headings in the main canal at such frequent intervals as one mile, as such structures increase the costs of LOCATION OF LATERALS 223 construction, maintenance and operation, and are in some degree a menace to the continuity of service, as they usually constitute points of weakness in the canal banks. In some cases where conditions of topography or land ownership require laterals at frequent intervals, one turnout is made to serve two or more laterals, by carrying the water parallel to the main canal for the distance necessary. The objections to this are the increased seepage losses from the parallel canal and the land it occupies. These are in some cases unimportant, and in other cases may more than offset the disadvantages of additional turnouts. The bottom of each lateral at its head should be a foot or two higher than the bottom of the main canal, so that sand moving along the bottom may be kept out of the lateral, but more than this should be avoided when possible, as any greater elevation may require the provision of a check in the main canal to permit the diversion of water into the lateral when only part capacity is being run, and checks are to be avoided when possible, espe- cially in silt-bearing canals. Where the slope of the country is very slight, and the grade and velocity of laterals are necessarily low, it is generally best to make each lateral serve the greatest possible area, as the larger lateral on a given grade will have a greater velocity, and the disadvantages of low velocities may be partly avoided. Laterals are commonly located on fairly level ground, and can and should in that case be so located when feasible, that the material excavated for the channel will be just sufficient to form the banks, and the channel and banks together, form the water- way of the required dimensions and capacity. Where the ground is very broken, however, this rule, if strictly followed, may introduce too much curvature, and to secure better aline- ment it may be advisable to locate partly in cut and partly in fill, in which case it is often possible to balance the cut and fill so that by a moderate longitudinal haulage of material the fills may be built of the materials taken from the cuts near enough so that excessive haulage is not required. In making such location, it is always best to make the cut somewhat in 224 CANALS AND LATERALS excess of the fill, rather than run any risk of having a balance the other way. 9. Abnormal Leakage from Canals. In numerous cases serious trouble has been caused and some canals have been rendered useless, by subterranean cavities not previously observed, which are developed by the introduction of water into the canals. On the Flathead Project of the U. S. Indian Service, a series of systems of small canals has been constructed, on which bad sink holes and cavities have appeared without any previous surface indications. On one system there is an average of twelve such holes to the mile, and these average from 12 to 15 feet deep and 200 feet long. On another small system there are about four holes to the mile, which average 6 feet deep and 100 feet long. When these canals were constructed, the ground was in apparently satisfactory condition for carrying water, being of stratified clay. In a few places minute cracks occurred in cuts about 3 feet below the surface, being so small, however, as to be hardly nc ticeable. When water was turned in, these cracks enlarged, and in a short time the substrata seemed to melt away, and great cavities appeared, absorbing the entire flow of the canal, which disappeared entirely. Sometimes by letting the water flow into the holes for a time they would puddle themselves, fill with water, and some repair would restore the canal. In the greater number of cases, however, no such result followed, and after developing the holes thoroughly the water was turned out, the sides of the holes blasted in, and the canal restored by careful puddling, after which no trouble was experienced. Many sink holes occurred at the structures along the canal, where the water followed down the cutoff trenches, and thus reached the substrata. They are more numerous in cuts that reach the substrata than at other places. The surface of the country in this region is peculiar in having a large number of potholes many of which form small ponds. These may have been formed by the collapse of underground caverns similar to those described. ABNORMAL LEAKAGE FROM CANALS 225 In the GRAND VALLEY, on the western slope of the "Rocky Mountains, near. Palisade, Colorado, is a region where the soil having no abnormal appearance in its natural state, settles from i to 5 feet vertically soon after becoming thoroughly saturated with water. Settlers, preparing this land for irrigation, prepare to " settle " the land with as much deliberation and matter of course, as in other regions they clear or level it. The " settle- ment " must be performed with care and skill, or great trouble FIG. 72. Cavity Developed in Canal Bed, Flathead Reservation, Montana. will result. It is necessary to saturate a large area at once in order that the settlement may be as uniform as possible, and not result in potholes and undulations that would be expensive to level. With the utmost care, however, the settlement is often uneven and erratic. This tendency, of course, introduces com- plications into the problem of canal construction, and it is nec- sary in building large canals to provide 2 or 3 feet of extra bank height, lest sudden settlement cause disastrous breaks. Occa- sionally cracks or cavities develop in the canal perimeter through which much water wastes, and which require careful puddling. 226 CANALS AND LATERALS FIG. 73. Cave Developed in Bottom or Canal, Flathead Indian Reservation. CONSTRUCTION OF CANALS 227 The main canal of the Reclamation Project on Spanish Fork River, Utah, showed settlement of the natural ground in several places of from i to 2\ feet, the subsidence appearing several weeks after the canal had been in use for the convey- ance of water. These phenomena occurred on steep side hills on what was at one time the shores of Lake Bonneville, in material varying from fine silt sand and gravel to heavy clay containing some small stones. The settlement here seems to be due to the closure of cracks and cavities left by the caving and sliding of the mate- rial on the hillside, where the meager precipitation had never furnished enough water to settle it. The North Side Twin Falls Irrigation System, Idaho, is built in a country underlain by lava rock through which the Snake River flows in a gorge several hundred feet deep. Any crevices in the lava, therefore, have ready communication with this deep gorge, and any water in them readily escapes. Numerous springs are in evidence on the walls of the canyon. Many cases occurred on the North Side Twin Falls canals where annoying leaks developed. These were dug clown to the rock and the crevices closed with concrete, after which the earth was puddled back. The canal system as a whole now shows fair average tightness. The canal system of the Pecos Irrigation Company near Carlsbad, N. M., where it traverses gypsum formations, was beset by leaks which enlarged by erosion and solution until they became so serious that for some distance the canal location had to be abandoned and the canal rebuilt on a lower elevation. In other places the leakage was corrected by placing a lining of concrete in the canal. 10. Construction of Canals. Where large canals are located in heavy cutting, it is sometimes economical to employ heavy machinery, such as the steam shovel, or the drag-line excavator. The latter is especially adapted by its long boom, to conditions where a wide canal in earth requires a long reach. The steam shovel is better adapted to handling rock. These are justified only where the yardage to be moved is large. A smaller invest- 228 r CANALS AND LATERALS FIG. 74. Building Lateral in Montana with Ditching Machine. FIG 75. Building Lateral in Montana with Elevating Grader. CONSTRUCTION OF CANALS 229 ment in plant will secure economical results by using the ele- vating grader, which loosens the earth and elevates it into a wagon alongside, or on a canal of moderate size may deposit the earth directly in the bank. Fig. 75. Small quantities of work, especially on small laterals, are sometimes performed with the common slip scraper, drawn by two horses. But the great bulk of earthwork on canals and laterals is performed by means of the Fresno scraper (Fig. 29), a modification of the old-time Buck scraper. The Buck scraper is especially useful in sandy soil with a low lift and short haul, and cheaper work FIG. 76. Building Canal with Elevating Grader. has been done with it than with , any other implement. A common form of Buck scraper consists of a working or frond board with an effective length of about 9 feet and a height of 22 inches. This board rests horizontally 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 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 tail board 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 230 CANALS AND LATERALS g OOO OO OO 10 OOO O OOO y OOO OO CO O tN O 10 10 000 | O O <^ i^-to do rj- ci M M 10 10 10 O u 1 J^ t^ 00 IN OC M ^0 OC *3- w O 8 CO ON OC 00 rO^t-rorOM co N H He, H -*. ^. M rt|M ^^ M .*c! O ^O 00 10 10 ^ Mg x:^c ^5i > e^-5 .3 3 rt 'rf ^ 3 ^ '3 g o X< c^ | S ^^WgS^c^ -1 co ^ o o P m 5 8 o ^5 p 'O *^ CO rt '^ ^ fi ^^ 5 'rt 3 o * S .s 1 ^ 3 CONSTRUCTION OF CANALS 231 o o u~> iJ"> Qv Tf Tj- -Tt *O O OO ^O co < ^- 00 00 vo MD CO UO O M H)C^ rl|N rH|lN CNOM : 'il ^ u ^ S ^_ : .| : : f ,- i h i : ^^ c .S ^ tj ^ ^ tl ? 6 ^ a ^ |l .2 M ' "^ A o tj ^^5 c M ^ C S 'S c ^ OJ n"] rt - ^^U S; : : : c 1) w ^-< cti uH g : -0* g c - s J fi a -i SjliSl 5 "u u j3 ^3 K . - ^ ^Z 11 a^ - n ^ i i u o n r-:^i 01 ..g O^ 'O ^'^IOOPO to to OC CO ^ ^ ^ !^ ^ ^ ^ ^ ^ ^ 5- ^ ?o O - OC 6 M t-~ | 10 PO O 15 Tf to J| COO tl-C^ t^ rfCNOiciQ ^" O O O O ra ; ; ; ; ; ; ; : ; ~~^ ' '. '. '. '.'.'.'. C 1 U ! ! a a : ::..:: u : ' S a! ; ; ; ; o ; O o ; ' *J S" -^ ^G x N . . 'r** s~~^ O 't/5 ] P 4-* ^ 4-J S I ? 'S ^ P i : J | 111! ^ ^ . .s^, . . c ^ . -< O ' > ^3 3 Q 13 *-" ri u ^j 4-1 < *j . ^ . . o O xT' H- 3 u o v u . P ?5 _ .^ rt-' 1 ' tlTlll|lll|l 5 j | r->U^r^^ t - >:3 U>^ ^ 5 it! P W K J rj 13 .. C rt .Si, C r rf C $ w rt A ^ U rt ^ 3 U ^ cillil' llllll 1^ C/2 CANAL LOSSES AND THEIR PREVENTION 233 merely stepping off the tail board, 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 tail board. The Fresno scraper is most satisfactory in handling tough earth too heavy to be handled by a Buck scraper, and which would even FIG. 77. Building Canal with Fresno Scrapers. give trouble to a road scraper. This implement is usually drawn by four horses and may handle 10 cubic yards per hour, with an average load of ^ of a cubic yard. Its operation is illustrated in Fig. 77. ii. Canal Losses and their Prevention. All earthen surfaces, whether natural or artificial, absorb more or less water when brought in contact with it. This is the principal cause of the loss of water carried in a canal. Though some water is also lost by evaporation this is generally less than 10 per cent of the quantity lost by seepage. The quantity lost varies widely 234 CANALS AND LATERALS with the character of the material through which the canal runs, being greatest in coarse sand and gravel, less in loam, and still less in clay. The clay may have as great or greater percentage of open space than the sand, but the passage of water through it is slower, owing to the extreme minuteness of the openings. In nearly all cases the losses from seepage constitute an important factor to be provided for and guarded against. The few excep- tions are where a canal passes through swampy ground, in which case there may be an actual gain in water, the canal serving somewhat the function of a drain. Where the canal carries silty water, there is a tendency to seal the pores of the channel and for this reason the seepage from a new canal is often much greater than it becomes' after a long period of use, the time required for improvement depend- ing upon the rate of silt deposit. The seepage rate increases with increased temperature, as the water partakes to some extent of the quality of viscosity exhibited by most oils. Where conditions are favorable, much of this seepage water finds its way back to natural drainage lines. 12. Seepage Losses. In 1912 and 1913, Bark measured 118 sections of canals in Idaho for determination of seepage losses. These canals varied in capacity from i to 3200 cubic feet per second and the tests included 287 miles of length. Seven of the canals in wet ground showed a gain. From the 109 canals showing a loss, the following results were obtained: Per Mile per cent Loss per Sq. ft. per 24 Hours. Cu. ft. Maximum loss 58 3 6.32 Average loss 7-4 I. 21 This average, of course, includes many canals with losses so large as nearly to destroy their value. In fact all the canals showing losses greater than 1.5 feet in depth per day over the wetted area should be classed as poor in holding quality, and improvement by silting, puddling or lining should be given SEEPAGE FORMULA 235 consideration. For unlined canals the following classification may serve as a rough guide: Poor, where losses exceed 1.5 feet in depth per day. Fair, where losses are from i to 1.5 feet per day. Good, where losses are from .5 to i foot per day. Excellent, where losses are less than .5 foot per day. The wisdom and character of improvement will depend in each case not only upon the losses, but also upon the value of the water to be saved and the damage being done by the seepage, and whether other economies are to be secured thereby. 13. Seepage Formula. The following formula is proposed as representing the results of existing data, to be used in esti- mating seepage to be expected from contemplated canals: PL > where / 4, ooo + 2 ,000 VV S = Seepage in cubic feet per second; C = Coefficient depending on material of canal; d = Mean depth of water in feet; p = Wetted perimeter in feet; L = Length of canal in feet ; F = Mean velocity of water in canal. Values of C are as follows: C = i = Concrete, 3 to 4 inches thick; C = 4 = Clay puddle, 6 inches thick; C = 5 = Thick coat of crude oil, new; C = 6 = Cement plaster, i inch thick; C = 8 = Clay puddle, 3 inches thick; C = 10 = Thin oil lining; cement grout; C = 1 2 = Clay soil, unlined ; C= 15 = Clay loam soil, unlined; C = 20 = Medium loam, unlined. C 25 = Sandy loam, unlined; C = 30 = Coarse sandy loam, unlined; C = 40 = Fine sand, unlined; C = 50 = Medium sand, unlined; C = 70 = Coarse sand and gravel, unlined. 236 CANALS AND LATERALS Care should be taken not to give too much weight to the above arbitrary values of C, as the seepage depends not only upon the surface of the canal perimeter, but also to some extent upon its backing. Any one of the linings above listed will make a tighter canal if placed on a clay or loam soil, than if it has a backing of sand or gravel, which transmit the water freely. 14. Canal Lining. It is becoming more and more the prac- tice to line irrigation canals and laterals, mainly for the reasons following : 1. To prevent loss of valuable water. 2. To avoid softening the lower bank on side hills, and con- sequent sloughing. 3. To avoid waterlogging land and thus destroying its fer- tility. 4. To prevent erosion of the canal bed where high velocities are convenient or economical. 5. To reduce friction and thus avoid excessive excavation in heavy rock cuts. Seepage from canals located on side hills often threatens the safety of canals by softening the lower bank and causing it to slough or slide. Where water is valuable the cost of lining is often less than the value of the water thereby saved. Such cases are becoming more frequent as water increases in value. Many cases occur where seepage from canals saturates and water- logs valuable land at lower levels, and lining may be required to prevent this. Where the topography of the country requires or permits a very heavy grade to be given a canal, concrete lining may be necessary to prevent erosion, and by thus utilizing excess grade the cost of drops is saved. In heavy rock cuts it may be found economical to provide a lining to diminish friction and thus secure a sufficient velocity and discharge with less cross- section so as to save expensive excavation. The existence of one or more of the various reasons may jus- tify the lining of a canal and lateral system throughout. This has been done by the U. S. Reclamation Service where the land is very sandy, upon the west extension of the Umatilla Project covering about 10,000 acres. It is also frequently done in CANAL LINING 237 Southern California where water is very valuable. It is thus possible to eliminate many drops that would otherwise be re- quired upon the lateral system, and to employ velocities higher than earth sections would permit, and thus keep the canals free from silt, trash and vegetation. Canal lining is usually of cement mortar or concrete, but in some cases other materials have been used. Where a canal is constructed on a long fill which might settle unevenly and thus crack a concrete lining, and where seepage would endanger its safety if unlined, lumber is sometimes used for lining, with the expectation of replacing this when decayed, with concrete lining, FIG. 78. Cross-section of Lined Channel, Santa Ana Canal. after the bank is well settled. Wooden lining may be used where the ground-water is impregnated with salts to such extent as to disintegrate concrete lining. Concrete linings are usually made from 2 inches to 4 inches in thickness, and joints running across the canal are necessary at intervals of from 20 to 40 feet, to prevent irregular contraction cracks. It is best to place the concrete in cold or cool weather, to avoid subsequent cracking, and to build alternate slabs which are allowed to harden before the intermediate slabs are placed. In cold climates, where hard freezing is common, it may be advisable to reinforce the slab with steel fabric or mesh to hold it together against heaving. If there is possibility of collection of water behind the slabs, this may be relieved by the provision of one or more weep holes near the center of the bottom slabs, and in the side slabs near the bottom. The joints may be relied upon to allow the escape of water in their vicinity. 238 CANALS AXD LATERALS If the side slopes are made 45 degrees or flatter, they may readily be placed without forms, by taking care to have the consistency of the concrete suitable to such use. If the depth of cut requires for economy a steeper slope than 45 degrees, it will be necessary to provide forms for the lining, which will increase its cost. The outside bank can sometimes be made flatter, and the form avoided. In countries where the winters are mild, a very thin lining has sometimes been used made of cement mortar or of concrete with small aggregates, plastered directly on the earth bottom and slopes, from f to i| inches thick, without forms, and without reinforcement. If this is carefully placed in cool weather, and protected from drying until thoroughly set, good results may be obtained very cheaply. Such linings have been extensively and successfully used on the Umatilla Project of the U. S. Reclamation Service. They would not succeed, however, where the ground is subject to heaving. Ir cases where ground-water is strongly impregnated with alkaline sulphates which threaten to disintegrate the concrete lining, the difficulty may be met by providing free drainage for the ground-water, and by placing 2 or 3 inches of screened gravel under the concrete slabs to facilitate the escape of ground- water through tiling placed for the purpose. In some cases where canals are located on steep side hills, they may be threatened by slides of snow or earth from the steep hillside above, and a protective covering may be necessary to prevent disastrous breaks from this cause. A reinforced con- crete arch has been successfully used for this purpose in the Spanish Fork Valley by the U. S. Reclamation Service. Concrete lining should be placed only on well-settled banks; otherwise unequal settlement will be likely to rupture the lining, thus reducing its efficiency, and hastening disintegration. The earth upon which the lining is built should be carefully smoothed and rolled, and if dry it is best to moisten it before placing the concrete, as dry earth will absorb some of the moisture which the concrete requires for the chemical process of setting. The concrete mixture should be about one part of cement to CANAL LINING 239 FIG. 79. Check Gates and Canal Lined on One Side. Interstate Canal, Nebraska-Wyoming. FIG. 80. Semicircular Concrete-lined Section of Main Canal, Umatilla Valley, Oregon. 240 CANALS AND LATERALS two of sand and four of gravel. The diameter of the largest particles of the gravel should not exceed one-half the thickness of the lining and where the lining is less than ij inches thick, it is usually best to omit the gravel, and use a mortar of i part cement to three parts of well-graded sand. FIG. 81. Concrete Lining. Truckee-Carson Canal, Nevada. A typical paved lining is that given the Santa Ana canal in California, in alluvial soil, sand, and gravel. This canal is almost wholly in excavation (Fig. 78) ; the water is permitted a velocity of 5 feet per second, and the depth is as great as 7^ CANAL LINING 241 feet for a bed width of 6J feet and top width of 12^ feet. In order that the lining may have a stable footing and the bottom be less liable to bulge, this is curved downward with a versed sine of i \ 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, grouted and faced with cement plaster. On the Tie ton canal, Washington, of the Reclamation Service, the lined sections in earth and loose rock are semicircular (Fig. r ~& \: ; \_|^Mortar Joint DETAIL OF JOINT l" Square^ ^ -T)--^ PA Back fill rrig'2- : - --^ FIG. 82. Reinforced Concrete Canal Lining. Tieton Canal, Washington. 82). The lining is of reinforced concrete, 4 inches in thickness, and extends i foot 10 inches above the center of the circular section. The upper edge is cross-braced every 2 feet by a 4-inch square brace. The diameter of the lined section is 8 feet 2 inches, depth of water 5 feet 3 inches, 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 242 CANALS AND LATERALS SECTION "A-A" its top. This steel canal is 19 feet 8 inches in diameter with i foot 8 inches straight sides at top, making a total depth of 21 feet 4 inches. The inner shell of J-inch steel plates is riveted to outer semicircular ribs of heavy T-rail placed 2^-feet centers. The top is braced with 3-inch flat and 3 inch by 2\ inch angle iron. The canal rests on a wall of concrete beneath its center and has expansion joints every 330 feet. Experiments conducted by B. A. Etcheverry in Southern Cali- fornia to determine relative per- colation from lined and unlined ditches showed the following rela- tive efficiency ratios. Using un- lined earth channels e i.o; heavy oil lining, 3! gallons per square yard, e = 2.o' y clay puddle, e = i.8; cement concrete 3 inches thick, 6 = 7.2. Careful cost records kept on the Orland Irrigation System embracing both unlined canals, and others lined with concrete, show a maintenance cost for the unlined canals of $123 per mile per annum, and $10 for the lined FIG. 83. Transition from Rock to canals. The lining has also re- Earth Cross-section, Lined Canal, duced the see page losses, Until this Reclamation Sendee. , f , ,. , loss from the lined canals is about one-tenth as great relatively as from those that have not been lined. On the main canal of the Carlsbad, New Mexico project, 37,300 linear feet of canal were lined with concrete two- tenths of a foot in thickness. This required 7,191 cubic yards of concrete at $13.67 $98,313, or $2.64 per linear foot, or, $13,820 per mile. The lining of the laterals on the same project, was accom- Rip Rap 6 "thick CANAL LINING 243 plished at a cost of $10.37 P er cubic yard of concrete of a thick- ness of .2 of a foot. The lining of the main canal on the Umatilla project, Oregon, with concrete, 3 inches thick, in the proportion of i : 3.5 : 5.2, cost $8. 1 6 per cubic yard, and carried a little more than a barrel of cement to the cubic yard. The side slopes were ij to i, and were lined without forms. The main canal of the Boise project was lined with concrete 4 inches thick, with joints at 16 foot intervals. The records show the following costs: Cost per Cu. yd. of Concrete Cost per Linear Foot of Canal Plant charge. . $0 858 $0 80 1 Gravel and sand Cement 1.079 2 06^ 1.008 2 76? Water O 222 o 207 Forms o 177 o 165 Mixing and placing I 603 I CQ7 Supplies. O IO7 O TOO Superintendence and accounts 0172 o 161 Engineering. o 008 o 092 Total for concrete . $7 279 $6 708 Preparation of foundation 2 . 349 2 . I(K Grand Total $9 628 $8 QQ3 The U. S. Reclamation Service has in several instances employed clay puddle with satisfactory results, to tighten the open soil of the canal perimeter. Puddle lining, 4 inches thick, has cost on an average about i cent per square foot, exceeding this where the haul for the clay was long, and being less where all the conditions were favorable. On the Grand River project in Colorado, some of the canal location was in shale with many open- seams which wasted much water to the injury of lands below upon which the water emerged, forming bogs or swamps. After some exposure to the air, the shale disintegrated to some extent on the surface, and then was 244 CANALS AND LATERALS plowed, and after some weathering was harrowed, the water turned in, and harrowed again, forming a clay puddle which was very effective in reducing the seepage. In addition to this muddy water was turned into the canal and ponded at points where seepage was great, and by depositing its mud greatly reduced the seepage. Similar measures have been employed in many other places with good results. FIG. 84. Lining Canal with Concrete, Idaho. On the Minidoka project clear water was carried in a canal built partly through coarse sand in which losses were very great, and it was after several years decided to try to reduce the losses by depositing silt in the canal. To accomplish this, a deposit of clay was selected near the canal, and water was pumped from the canal through a hydraulic monitor and the clay was by this means washed into a flume and carried into the canal and deposited by ponding or checking the canal where the puddle was needed. The result of this work was the AMOUNT OF RETURN SEEPAGE 245 deposit of about 100,000 cubic yards of clay over the perimeter of the canal at a cost of about 20 cents per cubic yard. Where this was done the losses from the main canal were reduced from no cubic feet per second in 1912, to 71 cubic feet per second in 1915, besides important reduction of losses in the laterals. 15. Amount of Return Seepage. 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. 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 proportional 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 point in the same direction. The amounts of returned water by seepage indicated in the above experiments must not be taken as a cri- terion of what may be expected in other regions. The cir- cumstances surrounding these cases were especially favorable for the return of seepage water. In other regions 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 trib- utary to them. Observations made at storage reservoirs for New York and 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 largely due to the fact that the water plane of the surrounding country 246 CANALS AND LATERALS 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 refill while no water is entering from streams, and similar additions from seepage have occurred in other reservoirs. As a result, the actual available capacity of a storage reservoir may be found to be greater than its measured capacity. REFERENCES FOR CHAPTER XIII FORTIER, SAMUEL. Concrete Lining as Applied to Irrigation Canals. Bulletin No. 126, U. S. Office of Experiment Stations. MEAD AND ETCHEVERRY. Lining of Ditches and Reservoirs to Prevent Seepage Losses. Bulletin No. 188, Agricultural Experiment Station, Berkeley, California. ETCHEVERRY, B. A. Conveyance of Water. McGraw-Hill Book Company, New York. CARPENTER, L. G. Losses from Canals from Filtration or Seepage. Bulletin No. 48, State Agricultural College, Fort Collins, Ccl. MORITZ, E. A. Seepage Losses from Earth Canals. Engineering Neu's, Aug. 28, 1913. HANNA, F. W. Water Losses in Irrigation Canals, and Methods of Prevention. Engineering and Contracting, Oct. 9, 1912. FORTIER, SAMUEL. Conveyance of Water. Water Supply Paper 43, U. S. Geo- logical Survey, CHAPTER XIV CANAL STRUCTURES i. Classification. The term " Canal Structure " is usually applied to all structures necessary in connection with the canal, aside from the earthen waterway itself, and its lining, which may be classified as follows: 1. Works for controlling canal water. a. Headworks. b. Turnouts. c. Spillways. d. Drops, and checks. e. Measuring devices. 2. Drainage crossings. a. Flumes, and superpassages. b. Inverted siphons. c. Culverts. d. Pipes. 3. Highway crossings. 2. Location of Headworks. The first requirement for a suitable diversion point is permanence of the stream channel, so that the stream will not leave the works after they are built, nor wash them out. Preferably both sides of the stream should be rock or hard gravel not easily eroded. It is especially desirable that the side on which the regulator is built should be of this character, for the safety of the works, which should, if possible, be founded upon rock. It is desirable that the ground in which the first few rods of the canal is built should be of firm material, and so high as to be not subject to overflow from the stream, so that the canal will thus be protected until it gets away from the river. 247 248 CANAL STRUCTURES The diversion works should be located so far as physical conditions will permit, at such an elevation as to command the land to be irrigated, with ample grade allowance for the canal, without an excess of grade. The location should permit of the construction of regulating works parallel to the stream so that the current of the stream may have a clear sweep past the regulator, and close to it, to facilitate sluicing away sand and gravel that threaten to pass into the canal. It is always desirable to secure rock foundation for the diversion weir, but if this is impracticable, a safe dam can be EUCC7.0 sq. bars 6"c.to c. \"\ El. 1612.0 ?.5WP.9'.9.\ft.<5?.-.a.V.'.4 ?????.?.? '$O& ^> G ''* Q&& ^O.S 4 nd;< jrfavel^n^ UulQ Cut off wall to extend SECTION A-A 3 into shal. FIG. 85. Cross-section of Corbett Weir, Shoshone Project, Wyoming. built by taking proper precautions, upon gravel, sand, silt or clay. 3. Canal Headgates. Every canal should have one or more headgates so located that the quantity of water admitted to the canal shall be at all times under control. On streams carrying sediment or transporting sand or gravel, means should be provided for preventing the entrance to the canal of sand and gravel likely to deposit and clog the canal. The lighter silt which is easily carried in suspension is not so objectionable, as it can be mostly carried through the canals and laterals and deposited on the fields, where it has considerable CANAL IIEADGATES 249 fertilizing value. The heavier silt, sand and gravel are more likely to be deposited in the canals and entail great expense for removal, and even if carried to the fields are nuisances which should be eliminated at every opportunity, and if possible they should be left in the river bed. To accomplish this three precautions may be employed: 10 20 30 F IG< 86. Plan of Corbett Dam and Head works, Shoshone Project, Wyoming. 1. The stream velocity may be reduced before entering the canal, thus causing the settlement of the heaviest particles in suspension. 2. The water entering the canal may be required to flow in a thin sheet over the top of a long weir so that only the sur- face water can enter the canal, as the surface carries only the lightest sediment. 250 CANAL STRUCTURES 3. Means should be provided for sluicing the deposited sand away from the headworks, and causing it to pass on down stream. To secure these conditions, a diversion dam is necessary, to form a settling basin, and to furnish head for sluicing it out when needed. The gates through which the water enters the canal should be parallel to the stream, so that the water passing into the canal shall move normal to the river channel. Immedi- 4 I NOTE: 7 a 5 gates each 1 feet high W "'"" "'<*- -"5'5 ,.-" ' ""*! SECTIONAL " i * 4 11 ---* | ELEVATION CROSS SECT'ON DETAILS OF GATE FIG. 87.' Wooden Gate, Leasburg Canal Regulator, Rio Grande, N. M. FIG. 88. Iron Regulator Gate, Minidoka Canal, Idaho. ately adjacent to the entrance of the canal, and at right angles thereto, at the end of the diversion dam, one or more sluice gates should be placed, with their sills at the normal bed of the river, which can be quickly opened and as readily closed. When opened the water will rush through under the : head equivalent to the difference of water level above and below the dam, and the high velocity thus generated will scour the channel immedi- ately in front of the entrance to the canal, and thus furnish CANAL HRADGATES 251 capacity for subsequent use as settling basin, to be again sluiced out when filled. The entrance to the canal should be controlled by flash boards or some similar device so arranged that the water will flow into the canal as a thin film from the surface only, and thus carry on a skimming process, the heavier sediment being TOP VIEW Cast [ron Shutter & ^ cl FRONT VIEW SEC. C-d i . . j ', !,} 5 2 z % Bronze J^ . ^^v^v^xv vvw ^^^^ -r SEC. a-b FIG. 89. Cast-iron Sluice-gate, Interstate Canal, Nebraska-Wyoming. generally some distance below the surface, especially after the velocity of the water has been checked. One of the best examples of the system here described is in use at the Laguna Dam on the Colorado River, at the head of the Yuma main canal (Fig. 94.) In this case the canal entrance or " regulator " is controlled by flash boards On the Carson River the regulator is a movable gate which is depressed into a chamber below the canal bed to open the gate, and is 252 CANAL STRUCTURES CANAL HEADGATES 253 254 CANAL STRUCTURES CANAL HEADGATES 255 256 CANAL STRUCTURES I I CANAL HEADGATES 257 lifted to close it, the water entering over the top of the gate like a weir, which thus exercises the skimming function. A similar effect is obtained by inclined gates at the head of the Goulburn Canal, Australia (Fig. 92). Flash boards, though cheap, are slow and laborious in manipulation, and except on very silty streams, the practice is usually to use ordinary iron gates as regulators. Where the conditions of water supply are such as to require the diversion of all the water in the stream most of the time, FIG. 95. Whalen Diversion Dam and Headgates, Normal to Dam. North Platte River, Wyoming. there is little virtue in the skimming process. Headgates are usually, therefore, of the ordinary type, which .open at the bottom by raising on a stem, and are sometimes called under- shot gates, because the water passes under them. Sluicing devices are most needed upon streams carrying much sediment like those of the Southwest, but are also very useful upon many Northern streams which may generally run clear, but nevertheless carry much sand and gravel by rolling 258 CANAL STRUCTURES along the bottom, and if this is allowed to enter the canal, it causes much annoyance and expense. Instances are not rare where the gravel carried into the canal during the June rise so depleted its capacity that it could not carry the water needed for irrigation, and it became necessary to close the canal and clean it during the height of the irrigation season, at great expense, and to the great injury of crops. BB FIG. 96. Sprague River Dam, Klamath Indian Reservation, Oregon. The headworks of a large canal are of great importance for protecting the canal against floods, and for regulating the flow into the canal. They should be founded upon rock if possible, and should be of masonry of gravity design, heavy enough to resist any tendency to shear, slide or overturn when subjected to the maximum pressure which can occur. They should be flanked with ample wing walls and unless founded on rock should have deep cut-off walls to prevent seepage around or under them. CANAL HEADGATES 259 260 CANAL STRUCTURES Fro. 98. Jackson Lake Dam, Downstream Face, Wyoming. FIG. 99. Headgates and Sluice Gates, Montrose and Delta Canal, Uncompahgre Valley, Colorado. CANAL IIEADGATES 261 FIG. loo. Division Gates and Drops on Tsar Canal near Byram All, Murgab Valley, Turkestan. FIG. ioi. Headworks of Sultan Yab Canal at Sultan Bend Reservoir, on Murgab River, Turkestan. 262 CANAL STRUCTURES TURNOUTS 263 4. Turnouts. Each lateral branch from the main canal and all the sublaterals down to the individual farm laterals, should be provided with regulators. They are similar in function to the regulator at the head of the main canal, but differ widely E I if * w E DETAIL OF MEASURING WEIR rn Kn B1 ro ^ g\~ Sjff*" I'll 111 1 V - = Var 1 at.-; 1 5 =f= | [j [ 3 Z; v L "*"i a Measuring Weir PI > j TT7 .AN -Holes l" j Icctplack ; - Tl 2 "**" -fl r-Z x 10- : A > 1 2 "x 12 " h i i j 2"xl2" n ; i 2"xl2" a n Note: All openings V >ver 5 tt-9 2'x8" S rinpeiB . . o_ \ ] I \ / J (r ELEVATION FIG. 103. Wooden Head to Lateral, Sun River Canal, Montana. from it, not only in size, but in not being required to withstand the torrents of the river, and instead of keeping out sediment, should facilitate its passage through the system and its deposit upon the land. They are consequently best of the undershot type, so as to stop as little of the sediment as may be. Turn- 264 CANAL STRUCTURES outs are usually located in an artificial bank of a canal, and must be carefully designed and built with a view to preventing the percolation of water around them. They must be provided with wingwalls with earth carefully puddled against them. The tendency of percolating water is to follow in straight or nearly straight lines the seam formed by the contact of the structure with the bank, and this tendency can best be met by providing numerous abrupt angles to interrupt the path around the struc- FIG. 104. -Check and Parm Turnout with Inclined Valve. ture. If the structure is of concrete, angular corrugations may be' produced by nailing 2- by 4-inch lumber vertically to the forms against which the concrete is afterward built, and into these corrugations the earth fill should be carefully puddled and tamped. The smaller turnouts are often in the form of a box or pipe leading through the bank, with a gate on the upper end. Earthen sewer pipe is best for this purpose, and standard steel gates TURNOUTS 265 and gate frames are on the market which are conveniently fastened to such pipes. Turnouts should be located at or near the bottom of the canal % from which they take water, in order that a supply of water may be drawn when the canal is running at part capacity. Where the elevation of the land is too high to permit this, it may be necessary to locate the turnout several feet above the bottom of the canal, and such cases will require the provision of FIG. 105. Cast-iron Valve on Small Lateral Turnout. a check in the canal below, in order to hold the water up and enable a supply to be taken when the canal is only partly filled. Such checks are, however, to be avoided if possible. In early canal building most of the structures were made of wood, and this is still common practice with the small lateral turnouts, which can be replaced with little interference with the water service. All large turnouts which serve important areas, and require considerable time for renewal, should be built of 2(>G CA NA L STRUCTURES TURNOUTS 267 268 CAXAL STRUCTURES concrete or other permanent construction. The capacity of the conduit should be sufficient to take the required amount of water at the lowest stage of the canal. Bars from both side and -mg walls round corners. Alternate bars from both sets in f fillet. FIG. 108. Reinforced Concrete Turnout with lo-Foot Drop, Garland Canal, Wyoming. The velocity of flow may be obtained from the formula V = C\ / 2gh, where h is the available head in feet, g represents the acceleration of gravity, in feet per second, and C represents a TURNOUTS 269 constant depending partly upon the shape, and partly upon the size of the orifice, and is greater for a bell-shaped approach i \ < Cast \ Iron /^ 1 / / * I 1 + c 3 Vc 1 * r " ^ _ 5 .> 5 ^ o 1 1 1. 'III ELEVATION SECTION Cl-b iiolior Bolt .1 SECTION C-d FIG. 109. Cast-iron Gates for Laterals, Interstate Canal, Nebraska-Wyoming. than an angular opening. It is usually somewhat less than .8, so that the formula may be written roughly V = 6V//. 270 CANAL STRUCTURES n CANAL SPILLWAYS 271 The capacity of the turnout will of course be the area of its cross-section multiplied by the velocity of the water, or 5. Canal Spillways. Any large canal system must for safety be provided with a number of spillways in order to discharge any surplus water it may contain, and avoid overtaxing its capacity. Also to discharge all the water, when it becomes FIG. in. Lateral Headgates North Platte Valley, Nebraska. necessary to quickly empty the canal in case of a break or a threatened break. The break of a large canal discharging its great volume of water across the country, may be very disastrous, especially if the canal is on a side hill high above the country threatened, or where the torrent crosses valuable improved lands. Some- times these conditions are aggravated by treacherous materials in which the canal is built, in which case the need of adequate spillways is greater. This need is also emphasized where the canal receives considerable local drainage into its prism, and in 272 CANAL STRUCTURES ex C/2 CA NA L SPILLWA YS 273 274 CANAL STRUCTURES CANAL SPILLWAYS 275 case of abnormal rains may occasionally have its capacity overtaxed. A large canal is usually provided with a permanent weir in its lower bank immediately below the headgate, the crest of the weir being placed at the elevation of normal water surface of the canal so as to discharge any water that may enter the canal in excess of its normal capacity. Such a spillway will not discharge any considerable quantity of water until the water stands considerably above its lip, and though the discharge increases with the rise of the water surface, it does not prevent such rise. The longer the weir, the less the rise it permits. Where it is necessary to have a close regulation of the level of the canal or basin controlled by a spillway, this may be secured by the provision of one or more siphons, of the type shown in Fig. 115. The interior lip / is located at the level at which it is desired to hold the water level. The intake lip i, is located a few inches below the same level. The outlet o is located as far below the lip as circumstances will permit, and is submerged under water, so that air cannot enter there. When the water rises above the level of the lip / it overflows into the pool o, and as it falls, it entrains the air in the siphon, creating a partial vacuum, which is filled by water forced in by the outside pres- sure and this process quickly exhausts the air from the siphon, and it is soon discharging full, under the head due to the dif- ference of level between the pond c and the pool o, less the loss of head due to friction velocity head, and any imperfections of construction. Velocity and discharge are found by the following formulas: and The discharge continues until the decline of the water surface permits air to enter under the lip i, in such quantities as to fill the siphon. While this device is in action, the surface of the pond <;, is depressed by an amount due to the entry head of the siphon, and this must be allowed for in fixing the elevation 276 CANAL STRUCTURES ...,..-. SF.CTION A-A FIG. 115. Plan and Section of Siphon Spillway, on Canal in Colorado Valley, California. CANAL SPILLWAYS 277 of the intake lip i, otherwise the action of the siphon will be stopped by the entrance of air before the pond is drawn down to the level desired. The coefficient of discharge c in such a siphon is usually between .6 and .7 when in full operation. Where a large canal is located in rock or other firm material, or in good soil protected by grass sod on very gentle slope, spillways are often provided by so locating the canal that the water surface of the full canal will be just even with the natural ground level on the downhill side, and omitting any bank for a ''8 both ways^ 1 Kk8" ao'o- 4^ SECTION Fro. 1 1 6. Spillway, Fort Shaw Canal, Montana. considerable distance. When the water rises above the normal level, it flows gently over this spillway, in a thin sheet, without destructive velocity. Care must be taken to prevent con- centration of the water where it would cause damage. Such a spillway costs practically nothing, and affords impor- tant protection to the canal against overtopping of banks where breaks would be the result. In addition to those automatic spillways above described which are designed only to discharge surplus waters, every large canal should be provided with one or more wasteways through 278 CANAL STRUCTURES which the canal can be safely and quickly emptied in case of a break. In the absence of such a provision, if the canal should break the water would rush through the break and continue to do so until the canal is emptied, after closing the headgates. This might occupy several hours or even days and cause a large amount of damage, both to the canal itself, and to the farms below which lie in the path of the flood in seeking its way back to the river. Such a spillway is usually called a wasteway. One such wasteway should be located every 10 or 20 miles according to the needs. If natural drains are crossed that can carry safely the full capacity of the canal, these furnish good locations for wasteways, and the necessary structure may be \o)*7>vPresent Surface :f^vV^>^o Ground Kote s Structure to be reinforced throughout with K'sq. steel bars spaced 12 c's both ways equidist. from concrete faces FIG. 117. Standard Sluiceway, Lower Yellowstone Canal, Montana. combined with the structure required for crossing the natural drainage channel. Where no such opportunity exists, location should be sought where the distance to the river is short, and it will be necessary to provide a substantial lined channel to the river, to prevent damage to the lands traversed. At the head of the wasteway, if possible, the bottom of the canal should be depressed several feet below the regular grade of the canal and the sill of the spillway gates should be at the lowest part of the depression. This will give the water in the wasteway a high velocity, and enable it to draw strongly from both directions in the canal, and thus empty it quickly. The depressed section of the canal will also serve to gather gravel, sand or heavy silt that may be traveling on the bottom of the canal, and the wasteway will serve as a means of sluicing such material back to the river, and thus perform a double function. In case the canal is heavily silt-laden, it may be advisable to CANAL SPILLWAYS 279 I 280 CANAL STRUCTURES widen as well as deepen the canal at the head of the wasteway, so as to greatly enlarge the canal section and reduce the velocity of the canal at this point, and thus form a settling basin for silt. A wasteway located within a short distance below the head of the canal at a point near the river may be so arranged that when opened it will produce a scouring velocity in the canal clear back to the headgate, and be made very effective in ridding the canal of accumulations of gravel, sand and silt. In such cases it is well to provide a set of check gates in the canal just below the wasteway, so that by closing these, the influence of the wasteway may be concentrated upon the scouring of the section above, and in case of a break in the canal below, the check gates may be left open to permit the emptying of that part of the canal also. The gates of the wasteway should be of some type that can be quickly opened, as they are primarily for emergency use. For this reason it is generally best to provide some form of power for opening them. A small turbine wheel acting under the greatest head available from the canal may be thrown instantly in action by a small valve operated by hand, or by electricity from a distance, and this wheel, generating 10 or 20 horse-power, may be made to open the gates very quickly. Where the canal is located high on a mountain side so that the great head and steep slope will cause a break to be especially destructive, a series of spillways may be electrically connected with automatic floats, so that if the water suddenly rises or lowers in the canal the floats close the circuit and open the spill- way, instantly. A slide from above may obstruct the canal, and cause it to overflow, but if the rising water opens the waste- way, the canal may be relieved before much harm is done. Conversely, if the canal water surface is lowered by an incipient break, this also opens the wasteway, and empties the canal before great damage is caused. A type of automatic spillway that has been successfully employed on the Tieton Canal in the State of Washington is described as follows: On the course of the canal where a spillway was desired, a CANAL SPILLWAYS 281 282 CANAL STRUCTURES pit was built about 4 feet below the grade of the canal. A cast- iron sluicegate 4 feet by 5 feet is operated by a lo-inch vertical turbine located just outside the wasteway pit with its intake at such an elevation that the sluicegate is entirely opened when the receding water falls to the center of the intake opening. The turbine shaft is connected to the gate shaft by a system of gears. To the turbine gate shaft is attached a drum around which a small cable is wound, having attached to its end a suspended weight. When the turbine gate is closed the weight is suspended and holds a projecting pin from the handwheel against the magnet release, which is electrically connected with floats placed at frequent intervals along the canal. Any abnormal change of water surface in the canal makes a connec- tion at the float that causes the magnet to release; this drops the weight, which opens the turbine gate and starts the turbine, which opens the wasteway gates. To close the gate the opera- tion must be started by hand until the water rises in the pit enough to enter the turbine intake, after which the clutch may be thrown in and the gate closed by water power. 6. Checks, Drops, and Chutes. Where the slope of the country over which a canal passes is greater than the safe grade of the canal, it becomes necessary to provide one or more structures in which the surplus grade can be concentrated, and the canal transferred from a higher to a lower elevation without injury to the canal. Such a structure is called a " drop " and may be either vertical or inclined. In the former, the water falls freely, while an inclined drop is one in which the water is carried down an inclined pipe, channel or chute, protected against erosion by some form of lining. A Check is a bulkhead in a canal designed to hold the water above it at a higher level than it would otherwise stand, so that when the canal is carrying only part of its capacity, water may be taken into a turnout location above the bottom of the canal. It may be desired at all times to maintain the water level above the check at a higher level than below it, in which case the check performs also the function of a drop. Where this is not the case, and the structure is simply a check to be used only when CHECKS, DROPS, AND CHUTES 283 the canal is running part full and water is being taken into the lateral, it should be so arranged that practically all of the bulk- head can be removed when not needed, so as not to greatly interfere with the flow of water in the canal. During the time that the check is in use, it acts of course, as a drop; i.e., the water stands at a higher level above than below the check, and in fall- ing exerts an amount of mechanical energy, depending upon the quantity of water and the amount of the fall. Precautions must be taken to prevent the destructive erosion of the earthen sides and bottom of the canal just below the check. FIG. 120. Concrete Drop with Water Cushion, Truckee-Carson Canal, Nevada. The necessity of providing drops under various conditions is a matter of judgment based upon experience. It involves a knowledge of the erosive power of the quantity of water to be handled at the velocity to be expected, and the capacity to resist erosion of the ground over which the water will pass. Some of these elements are variable and others may not be accurately predicted. It is therefore unprofitable to attempt any exact rules or fine distinctions. Some of the earlier irriga- tion works were built without any special provisions for excess grade, and although erosion was certain, the rule seemed to be " let it cut." These have in some cases resulted in gullies, which have done no great harm. On the other hand, some 284 CANAL STRUCTURES FIG. i2i. Notch Drop, Chenab Canal, India. CHECKS, DROPS, AND CHUTES 285 engineers carry to an extreme the theory that the theoretical slopes and velocities must be exactly secured regardless of cost. The true test of the problem is the inquiry " What will happen if no provision is made?" If the ground traversed is a loam or sand to a great depth, excess velocities will cause the eiosion FIG. 122. Crops-section of Drop, Bear River Canal. of deep gullies, and the deposit of the eroded material at some point lower down. Even when the channel is straight, slight obstructions or inequalities of material will cause a tendency to meander, and to undermine banks on the outside of curves. If this proceeds it may destroy good land, and load the stream with material to be deposited further down to the detriment 286 CANAL STRUCTURES of other property; it may become necessary to provide expensive protection to the banks, and this expense and the damage caused may exceed the cost of the drops that should have been provided in the first place, and may ultimately still be necessary. On the other hand, cases occur where the alinement of the canal is straight, and where rock, shale, hardpan or other IJTop of bank Bottom width of c&r.al **, Riprap canal for [-Top of bank !' varying distances ELEVATION FIG. 123. Notch Drop, Interstate Canal, Nebraska-Wyoming. indurated material occurs a short distance below the surface, that will resist erosion, and may be utilized to save expense in the provision of structures and their subsequent maintenance. The hard material may be irregular in its occurrence and quality, and when it is reached by the water, erosion is checked, and a steeper grade is soon established through the hard material CHECKS, DROPS, AND CHUTES 287 which becomes permanent. In this way the surplus grade is taken up, and with some bank protection, stability is secured. Where the country has considerable slope it may be neces- sary to provide hundreds of drops in the lateral system, and it thus becomes important to decide on the most effective and economical design as a standard for each grade, character of soil and quantity of water. Where the slope is considerable and the soil sandy, careful consideration should be given to lining the canal with concrete to prevent erosion, instead of the construction of drops. The high velocities thus secured will m/3"x 4" 2 x!2' *#'. '<:': ' Gruvel FiUin- v^ -[ [ _^J.L--- ' . , F^2"x 2"* &*j$ 2 x!2 x!2 FIG. 124. Timber Drop, Lower Yellowstone Laterals, Montana. permit reduction of the cross-section of the canal and thus save in excavation, besides eliminating the cost of the drops; and though the lined channel may be more expensive, it may still be justified on account of the saving of water and in maintenance cost, both of which are important. A cheap and efficient drop on a small lateral is formed by excavating the channel for the necessary distance on a grade of three or four to one, lining it with concrete, and providing a depressed basin at the foot of the slope to receive and check the rushing water. The lower side of this basin should be vertical to form an effective check to the water. A small cutoff 288 CANAL STRUCTURES CHECKS, DROPS, AND CHUTES 289 wall should be provided at the upper edge of the lining where the water reaches it, to prevent under-cutting. Such simple drops have been successfully used in light soils by the U. S. Reclamation Service, and are very cheap, requiring very little forming for the stilling basin, and none at all for the lining. For large volumes of water more elaborate structures are required. These are sometimes of wood, but are more per- manent and reliable when built of concrete. FIG. 126. Cylinder Drop on Franklin Canal, Rio Grande Valley, Texas. The notched drop, introduced in India and employed to some extent in this country, has the crest of the fall surmounted by a weir with a series of notches with their bases level with the canal bed, and the top of the weir at or above the full supply level. The notches are designed wider at top than at base, so as to discharge at any given level, the same amount of water that the canal carries at that level at normal velocity, and thus prevent undue fluctuation of velocity as the volume of water 290 CANAL STRUCTURES varies. Below each notch is provided a semicircular horizontal lip or bracket to receive the falling water and spread it out into a semicircular sheet. This has a tendency to dimmish the action of the water on the banks below. The U. S. Reclamation Service has used a novel form of drop in the Rio Grande Valley, consisting of a concrete structure FIG. 127. Series of Concrete Drops on South Canal, Uncompahgre Valley, Colorado. in which the water is controlled by balanced cylinder gates which can be adjusted to such opening as will produce the proper velocity to prevent scour and deposit of silt at all stages of canal flow. See Fig. 126. 7. Protection Against Erosion. The tendency to erosion arises from three main causes: 1. The impact of the water on the bottom of the canal as it falls from the higher to lower level. This usually requires some sort of paving. 2. The increased velocity generated by the surplus fall, PROTECTION AGAINST EROSION 291 which if not somehow checked will persist for some distance down the canal and erode its banks. This may be counter- acted by providing a stilling pool at the foot of the drop with depressed bottom and larger section than the regular prism of the stream, in which the energy is dissipated in surges and eddies, and from which the water flows away at normal velocity. 3. The waves produced by the commotion of the falling water, and which generally persist for some distance down the Fr. 128. Concrete Chute and Stilling Basin, Boise Valley, Idaho. canal in spite of elaborate control of the velocity of the water. This generally requires paving or other protection, of the bank for 30 to 50 feet below the drop, or in very light soil, a still greater distance. This protection may be a lining of concrete or of grouted rip-rap, or other form of paving. Open rip-rap without mortar soon fails in light soils by the washing out of soil through the cracks. In many cases sage brush held in place by stakes and wire has been successfully used. 292 CANAL STRUCTURES The amount and character of protection necessary depends upon the quantity of water falling, the amount of the fall, and the character of the material in which the drop occurs. Unless the latter is rock or very firm gravel or hardpan, some paving or other artificial protection is always necessary. The size and depth of the stilling pool has been much discussed, but engineers are not agreed upon any general rule to govern these points. The best practice is to provide a pool depressed from i to 3 feet below the bottom of the canal below the drop, and having a cross-section from 50 per cent greater than the normal water prism, to three times as great, varying between these limits according to the three factors above mentioned, namely, the height of fall, the quantity of water, and the character of soil in which the drop occurs. In some cases it is necessary to carry the water down a long slope requiring either a series of drops or a long chute, consisting of a lined channel with a stilling basin at the bottom. The choice between these types will depend mainly upon the cost, but if properly built the maintenance of a chute is generally less than that of the vertical drops that would take its place. The inclined drop or chute consists essentially of an inlet structure, a trough to conduct the water down the hill, and a pool at the bottom to receive the water and destroy its accumu- lated energy. The transition from the canal to the drop must be provided with numerous and deep cutoff walls for the wing- walls, floor and sides, carefully puddled in, to prevent percolation of water along the structure. Where the water enters the trough control gates should be provided. A short distance below, the trough converges to a narrow channel to correspond to the increased velocity, which may reach 40 or 50 feet per second. Cutoff walls must be provided at frequent intervals under the trough, and great precautions must be taken to prevent erosion under the trough, either by rainfall or by leakage from the structure, as the steep hillside will favor rapid and destructive erosion if an opportunity occurs. Trouble was encountered on the Boise Project of the Reclama- tion Service with the spilling of water over the sides of the stilling DRAINAGE CROSSINGS 293 basins at the end of concrete chutes and investigation was made to find a remedy. The cause of the trouble apparently was that in designing the structure no allowance was made for the great amount of air carried into these basins with the water. Eleven structures were investigated and the remedy generally adopted was to raise the sides and cover the basin. The investigations seem to indicate that in designing stilling pools, consideration should be given to the increased volume of the discharge due to mixture of air with water. For velocities from 15 to 40 feet per second, the increased bulk is estimated to be from 15 to 35 per cent. The pool or check basin at the bottom of the chute must be of massive construction to receive the shock of the rushing waters, and stop it without injury. An excellent form for such a check basin is one on the Sulphur Creek wasteway on the Yakima Project in Washington, which is designed to receive and stop a stream of 500 cubic feet per second flowing at a velocity of about 25 feet per second. This structure is of concrete, rectangular in plan 14 by 18 feet, by 18 feet high. The water comes in at one end of the box near the top, and escapes through two rectangular openings in the sides, each i2j by 4 feet. The water plunges into the basin and dissipates its energy by impact on the water already there, and is turned practically through 3 right angles before it can escape. This structure accomplishes its object satisfactorily, as the water flows quietly down the unlined canal without erosion. Deep gullies are unsightly and may be dangerous if very deep with precipitous banks, and it requires important saving of expense to justify the omission of sufficient drops to consume the excess grade. Where the drop can be located in rock it may be unnecessary to provide any special protection to the bottom or sides. 8. Drainage Crossings. Where a canal location intercepts a natural drainage line or torrent, as it is sometimes called, it is necessary to decide what disposition to make of the drainage water that may be expected, in order that it may not damage 294 CANAL STRUCTURES DRAINAGE CROSSINGS 295 the canal. There are four possible methods of dealing with' such problems, each of which is suitable to a certain class of cases. i. The drainage may be received into the canal, in cases where it is small in amount and the canal is large. _.ZJT_. - -x -(,0 -x- FIG. 131. Elevation and Cross-section of Iron Flume on Corinne Branch, Bear River Canal, Utah. 2. The canal may be carried over the drainage channel in a flume, or upon an embankment provided with a culvert through which the drain water passes under the canal. 3. The canal may be carried under the ravine in an inverted siphon or pressure pipe, or the drainage may be conducted over the canal in a broad flume called a superpassage. 296 CANAL STRUCTURES 4. The drainage may be intercepted by a diversion dam and canal and conducted along and parallel to the canal, to a point where sufficient drainage is concentrated to justify the provision of one of the structures above mentioned. Span varies from 14 to 30 -I r rf3355t tf-^rp^rfr. j -jjl III. 1-1-4 4- 1 ' 1- ---+-4-4- 1 Span s Span s - .^44-j-|4 r f '--t--i-irji-Izi-i :- [ttitbJ Kfi ' *-14' 10' 13' 70" 24' 8'0> 8'0' 20' 8'8' i)'o' 28' 9'*" C * H- Upper girder"^ bars over Kf. * ELEVATION OF FLUME,- 7 4 is supports only/f , 6varies from 4 'to 1 I > ^Longitudinal rs ^Rl2' c. to c. May be used for outlet when " desirable .| Bars in Floor placed in ccntt SECTION A-B Method of bonding flume to inlet VERTICAL SECTION AT COLUMN ELEVATION OF COLUMI Top of column base = , .I . 6 = 10 2 9'x 13 3'o'x 15 0' PLAN OF COLUMN BASE J-..JI LONGITUDINAL SECTION OF INLET FIG. 132. Standard Reinforced Concrete Flume, Reclamation Service. Wherever a large canal is built on ground sufficiently sloping so that no bank is required on the uphill side, some rain water will inevitably flow into the canal from the surface of the ground. From the admission of such rain water, it is but a step to the admission of small drainage channels which seldom carry water, DRAINAGE CROSSINGS 297 oint and carry but little at any time. Where it is necessary to admit considerable quantities of surface water to the canal, its safety may be protected by providing in the vicinity a spillway of one of the types described in Art. 5. Even when the water brought in may be thus taken care of, the admission of drainage to the canal is often objectionable because such drainage usually 4- Square :arries sediment and detritus which may be expensive to re- move. Care must be taken in all cases to protect the side of the canal where drainage enters, against the erosion of gullies which destroy the sym- metry of the canal, and fill it with detritus. This protection may consist of a short concrete retaining wall, over which the drain water falls into the canal. The provision of a combined wasteway and settling basin with bottom opening for sluic- ing sediment, may justify the admission to the canal of much drainage in the vicinity other- wise inadmissible. Cases sometimes occur where the collection of drainage water is one of the important functions ! | of a canal, the object being to FIG. 133. Circular Reinforced Con- increase the water supply above crete Flume and Trestle, Tieton ill rr^i Canal, Washington. that otherwise available. The water supply thus obtained is usually so irregular that a storage reservoir is necessary to utilize the full benefit of such supplies, and it thus becomes especially important to provide for ridding the canal of sediment brought in with the drainage to avoid filling the reservoir with solid matter and destroying its useful- 298 CANAL STRUCTURES ness. This may best be done by means of settling basins with bottom opening for sluicing purposes as described in Art. 5. FIG. 134. Headworks of Cavour Canal, Po River, Italy. FIG. 135. Brick Aqueduct, Carrying Cavour Canal, Po Valley, Italy. In all cases the drainage to be admitted should be carefully estimated, especially as to its probable maximum volume, and provision made for such maximum with a considerable margin FLUMES 299 of safety. The lower bank of the canal must be of ample height and thickness, and must be rigidly inspected for the works of burrowing animals, so that a sudden rise in the water level shall not disclose a hole to lead water through the bank and cause disaster. 9. Flumes. Where the drainage line intercepted is in a ravine or canyon of moderate depth, but well below the grade of the canal, the latter may be carried across in a flume. This may best be of concrete, especially if very large, but on account of the high cost of the concrete structure, flumes are more often built of steel, upon wooden trestles, or entirely of wood. These are more expensive in maintenance, and will require renewal of the wooden parts in from 10 to 20 years, even when well cared for. In any case the trestle bents should be founded upon concrete or rock, and contact between wood and earth at any point entirely prevented, to avoid quick decay. The most common form for wooden flumes is a rectangular box, and should provide for a water depth of about half the width, as this gives the maximum value of r in the formula and consequently the maximum velocity and capacity. For the same reason, the inside of the flume must be made as smooth as possible. The lumber should be planed, and placed longitudinally, so as to have the minimum number of joints across the course of the water, and every care taken to avoid friction or obstruction to the flow. The flume must be so constructed that it is firmly held against the tendency to spread which will develop when filled with water. This is accomplished by means of the sills at the bottom, and the sides may be held at top by means of braces across the top, either of timber or of heavy wire, or the sides may be braced by inclined studs placed upon extensions' of the sills. A standard form of box flume is shown in the drawing, Fig. 138. The lumber forming the box of the flume must be carefully milled so as to fit well, and some measures must be proviqled to make the cracks water-tight. This is sometimes secured by milling a small bead on one or both edges of the lumber which can by reasonable pressure be made to form a tight seam. Very 300 CANAL STRUCTURES FLUMES 301 302 CANAL STRUCTURES effective sealing may be secured by caulking with oakum. To facilitate the caulking process the lumber may be slightly beveled on one edge, thus leaving a small opening on the inside of the crack for the insertion of the oakum. The caulking may '10'- FIG. 138. Cross-section of San Diego Flume, California. require repetition every spring for two or three years after which longer intervals may be found permissible. Another means of closing the seams of the box flume is by inserting asphalt or coal tar, and holding it in place by means of a batten along the seam, or a similar end may be secured by milling the lumber so as to admit and hold the sealing ma- terial. An objection to the use of battens on the bottom of the flume is that if fastened to both planks forming the seam, the shrinkage that is likely to follow when FIG. 139. Cross-section of Stave and Binder water is turned out of Flume, Santa Ana Canal, California. the flume Will split the batten and cause leaks with no convenient means of repair except by replacing the batten. FLUMES 303 Coal tar or asphalt should in use be applied hot and preferably in warm weather, so that all cavities may be penetrated before the asphalt solidifies. Another serviceable form of wooden flume is the half circle, formed of wooden staves supported by iron or steel rods, the ends of which are held by stringers. These rods are fastened by nuts which, when screwed up cinch the staves and close all cracks tightly. This means can be used each year to take up the shrinkage of staves and keep the flume tight. The necessity -^ 1 Steel Rods spaced 6 ce The longitudinal reinforcing rods of the flume are to be carried W)"iuto the concrete face of approach 'Floor of flume SCALE OF FEET 10123456789 10 FIG. 140. Section through Reinforced Concrete Aqueduct, Interstate Canal, Nebraska-Wyoming. of caulking may thus be avoided,' if the staves are carefully milled, and this constitutes an important advantage of the circular over the rectangular form of flume. The screw threads must be kept well greased to prevent rust, and keep them available for the annual cinching. When properly built and maintained such a flume is generally more satisfactory than the box flume. Steel Flumes. Closely similar to the circular wooden flume is the steel flume supported on wooden trestles. The metal takes the form of the half circle, and is supported by iron rods. The sheets of steel are purchased in standard sizes, the largest 304 CANAL STRUCTURES FLUMES 305 obtainable being usually 10 feet in length. A half -circular flume formed of such sheets has an area of 31.76 square feet, or leaving i foot freeboard, about 25 square feet of waterway. If a capac- ity greater than this is desired, it becomes necessary to duplicate the flume, or adopt some other type. The transverse joints have been formed in various ways more or less efficient, the most essential requirement being that they present the least possible obstruction to the flow of water, and hence be flush with the surface of the flume. If the flume is over 50 feet in length, it should be provided with joints that will absorb expansion and contraction due to temperature changes. If the flume can be conveniently built in cold weather, while the metal is contracted, fewer contraction joints will be required than if placed in summer. The metal sheets should be galvanized and after construction the waterway should be treated with two coats of tar paint, the first of water-gas tar and the second of coal tar. If the flume carries sand or gravel this will quickly wear through any protective coating, such as tar or zinc, and leave the iron exposed to rust, so that it is very important to eliminate sand or gravel if present. This may be done by providing a settling basin and sluice gate at the upper end of the flume, either in the flume itself or above its entrance. With such a provision, and careful attention, a metal waterway may be expected to last much longer than a wooden one. All parts of the flume should be amply heavy, so that its load will not cause notable deflection and develop leaks. It is of prime importance that the lumber be well seasoned so that it will not seriously warp and shrink after construction. The life of the wood may be somewhat increased by some form of treatment by antiseptic preparations. The cheapest of these is a bath in hot crude petroleum. This should be sufficiently prolonged so as to permit the escape of all confined air, and its replacement with oil. Treatment with creosote or zinc oxide as practiced with railroad ties prolongs the life of the wood, but where it is kept 306 CANAL STRUCTURES FLUMES 307 L 308 CANAL STRUCTURES away from earth, the benefits derived from treatment are hardly commensurate with its cost. Some benefit may be derived by treating the structure after completion with a wash of any of the common preparations from petroleum or coal tar; or of the more durable paints. Painting lumber not seasoned does more harm than good. Care should be taken to prevent contact with earth, which hastens decay whenever it occurs. Footings and mud sills may generally be built of concrete. 10. Behavior of Various Metals in Presence of Alkali. Cer- tain preparations of iron and steel have shown resistance to the IP , iti p HALF SECTION SCALE OF FEET 10 20 FIG. 144. Half Longitudinal Section, Reinforced Concrete Aqueduct, Interstate Canal, Nebraska-Wyoming. attacks of acids as shown by standard tests, but western waters are often alkaline, and resistance to alkali is a different problem. The U. S. Reclamation Service has made a series of experiments to test the virtues of various metals in the presence of alkali such as occurs in many western soils. The results of these tests as reported by the project managers on three different projects are shown in the following table. All the sheets were planted in alkaline mud, the tests samples being side by side, under conditions as similar as possible. The results speak for themselves: BEHAVIOR OF VARIOUS METALS 309 TABLE XXXI. METAL SHEETS IN ALKALINE SOILS Material. Weight, Ounces. Length of Test, Years. Loss, Ounces. Loss, Per Cent. Project. Toncan metal, galvanized . . 81.75. 4 I .00 1.36 Sun River Ingot iron, galvanized 88.0 4 I .00 1.14 ( i Mild steel, galvanized 79-50 4 I .00 1.26 c Toncan metal, ungalvanized. 73-75 4 5-50 7.46 " Ingot iron, ungalvanized. . . . 78.50 2 2.25 2.87 1 1 Mild steel, ungalvanized.. . . 75-50 4 4-50 5-96 ( I Toncan metal, galvanized. . . 81.00 a* 50 .60 Uncompahgre Ingot iron, galvanized 89.00 a* I .00 I . IO i ( Mild steel, galvanized 81.00 a* 1 .00 1 . 20 i e Toncan metal, ungalvanized. 73-50 a* 4.50 6. 10 ( i Ingot iron, ungalvanized . . . 81.50 2| 4-50 5-50 ( i Mild steel, ungalvanized.. . . 76.00 2| 3-oo 4.00 " Toncan metal, galvanized. . . 82.50 a* 2.50 3-03 Belle Fourche Ingot iron, galvanized 91 .00 at 2.50 2-75 ( ( Mild steel, galvanized 81.00 at I . 20 i . 48 ( t Toncan metal, ungalvanized. 78-5 at 5.10 6.50 (( Ingot iron, ungalvanized . . . 83-5 at 4-70 5-63 < i Mild steel, ungalvanized.. . . 76.0 aj 2.20 2.90 The most striking result brought out by these tests is the immense advantage of galvanized sheets over those of plain metal. It is also made clear that none of the different special preparations tested have any great or uniform advantage over any others. Where the cost is not too great, flumes should be constructed of concrete, as this will generally form a structure of permanent character if properly built. If the waterway to be crossed is large and the canal also large, such a flume becomes a very heavy structure, and must be very solidly founded to prevent settlement and failure. The most desirable foundation of course u rock, although indurated sand, clay, shale or gravel may be depended upon if the foundation is spread enough to prevent dangerous unit stresses. A foundation of shale some- times contains seams of soluble salts, which unless well protected, may later dissolve and cause trouble. In several localities where the surface is underlain by shale, the structures founded thereon, and even the lining of canals 310 CANAL STRUCTURES FlG. 145. Reinforced Concrete Aqueduct, Spring Canyon, Interstate Canal, Nebraska-Wyoming. FIG. 146. Concrete Flume, Spanish Fork Valley, Utah, showing Warped Transi- tion from Canal to Flume. BEHAVIOR OF VARIOUS METALS 311 I I I 312 CANAL STRUCTURES m & FIG. 148. Continuous Wood-Stave Pressure Pipe, Idaho Irrigation Company' Canal. BEHAVIOR OF VARIOUS METALS 313 have settled and cracks have formed, causing leakage and other annoyance. This seems to be due to the water penetrating the indurated shale and removing a portion of the soluble salts FIG. 149. Elevation and Cross-section of Nadrai Aqueduct, Lower Ganges Canal, India. from the seams and crevices which they fill. In many places where canals are constructed through hard shale requiring powder to loosen, they have settled badly when water was 314 CANAL STRUCTURES turned through them. In a few instances the shale has swelled, causing the bottom to bulge. One of the most important of the necessary provisions is to make safe allowance for changes of temperature which cause expansion and contraction of the flume structure. This is apt to cause openings between the concrete ends and the earth filling, and to start a leak which will rapidly enlarge under the high velocities generated, and cause a break difficult to repair, and more difficult to guard against in future. The problem is to devise a junction between the concrete and earth that will permit movement without leakage. Such a junction has been successfully used at the termini of the Spring Canyon flume on the North Platte project, by means of suc- cessive layers of canvas saturated with tar, to make it imper- vious. ii. Culverts. Where the grade of the canal is high enough to permit its passage over the intercepted drainage channel, and the volume of the torrent to be intercepted is not too great, the canal may be carried across in an earth fill, and the drainage water carried through the fill in a cast-iron pipe, or if too great for this, in a concrete conduit. The fill must be carefully con- structed, observing all the rules of earth dams as to water tight- ness and careful connection at the ends with the natural banks, and at the bottom with good material for foundation. The culvert should have flaring approaches to conduct the water gently into the conduit, and these should be founded deeply and provided with wingwalls to prevent percolation around them. The culvert, whether of iron or concrete, should be provided with several cutoff collars passing entirely around them, and well puddled in with good material at least one- third of which should be clay. The central portion of the fill, and all that portion adjacent to the canal water section should be wetted and rolled, or carefully puddled, to the end that no percolation from the canal shall endanger the fill. Culverts are sometimes made of wood, but this is not permanent work, as the wood in contact with moist earth does not last long. Small culverts may be made of galvanized, corrugated iron where the fill is CULVERTS 315 not too high for this, but care must be taken to allow for the retarding influence of the corrugations, and to provide all the precautions necessary with cast-iron pipes. Where a large canal intersects a large drainage line so nearly at grade that it is not practicable to carry the canal over the drainage, the canal may be carried below grade in a pressure conduit, or the torrent may be carried over the canal in a large flume, which is called a " super- passage." The superpassage must be amply large with a wide margin of safety to discharge the largest torrent that the drainage line may bring, without danger of overtopping and should be carried upstream on a grade of not less than i in 5000, a sufficient dis- tance to intersect the natural grade of the torrent, pass under it to a depth of several feet, and terminate in a cutoff or curtain wall carried considerably deeper unless rock or impervious or indurated material is encountered sooner. No exact rules can be laid down except that the upper end of the bottom and sides of the superpassage must be so bonded and incorporated with the bottom and sides of the torrential channel as to leave no danger of the water working between and passing under or around the structure, and it must be remembered that these torrents 316 CANAL STRUCTURES a CULVERTS 317 in flood, often erode under their channels far below the customary bed, and fill them again on the declining flow. The superpassage must deliver the torrent to its natural channel, or other safe channel in a manner, and at a distance FIG. 152. Inlet to Rawhide Siphon, Interstate Canal, Nebraska-Wyoming. FlG I53 ._si p hon Crossing under Rawhide Creek, Interstate Canal, Nebraska- Wyoming. from the canal such as to insure against injury or menace to the canal. As the concrete superpassage will have a much smoother surface than the channel of the torrent, its effect will be to accelerate the velocity of the water, and it may be advisable 318 CANAL STRUCTURES to provide a protected stilling pool or other means of checking its velocity to avoid destructive erosion. The provision of a superpassage applies mainly to cases where the torrent to be controlled is very large, and no loss of grade in the canal can be permitted. Where one or both of these conditions is absent, it may be preferable to carry the canal under the torrent in a pressure conduit in which the pressure of the entering water forces the water to the same elevation at the issuing end, less certain losses. On account of the expense of a such a conduit built underground, it is generally necessary to make it of much smaller cross- section than the canal and give it a correspond- ingly greater velocity. This consumes head, or grade, and hence is to be avoided where the conservation of head is impor- tant, and must be taken into consideration when comparing this with other methods of handling such torrents. The canal should be lined with concrete for a short distance above the entrance to the structure, and the section of the conduit gradually warped from that of the canal to that of the pressure tube, so as to present no angles, nor sharp turns to the entering water, that would create eddies or otherwise retard its velocity. In this way the head consumed in entry may be reduced to a minimum, but some allowance must still be made therefor, while due allowance must also be made for the head or fall in water surface necessary to produce the velocity required in the pressure conduit. This head is found from the formula. 72 V = V 2/z, which may be transformed into h = . 2 In this case V = the difference in velocity between the water flowing in the canal and that required in the pressure conduit. As the water issues from the conduit into the canal it is generally necessary to change its velocity and section to that of the normal canal section. If the section is changed by warped surfaces so slowly, gently and gradually as to cause no waves nor eddies, it is possible to recover nearly all the velocity head, so that the main losses of head will be the entry head and the friction in CULVERTS 319 the conduit. When the approach and exit are properly warped, and the inside of the conduit made as smooth as practicable, these losses of head are all small except when the conduit is long, or its velocity very high, in which cases the friction losses are heavy. It is practicable in most cases to secure an entry coefficient between 80 and 90 per cent, by proper construction of the entrance, and to recover at least 75 per cent of the velocity head by proper construction of the conduit at the exit upon grade. To secure these results, the bounding surfaces of the conduit must be very gently curved, and a distance at entry must be Vertical Rods %"x %'haeh abutment ] a_Rodajn Cen. WallL 66 Longitudinal FIG. 154. Reinforced Concrete Twin Siphon, Interstate Canal, Nebraska- Wyoming. consumed in the transition equal to twice the difference between the greatest dimension of the original water prism, and the corresponding dimension of the pressure conduit. The issuing conduit must consume in transformation about double the distance required for the entrance by the above rule. The junction of the structure at both ends must be safe- guarded by curtain and wingwalls, and the usual precautions taken to prevent percolation around them. The pressure conduit must be built well below the grade of the torrent it crosses, in order to avoid the danger of a washout. Where a flume or a pipe is required on a canal line, it is 320 CANAL STRUCTURES advisable to give some increased grade, in order to induce an increased velocity and to force the required quantity of water through, without building a structure as large as would be required with a low velocity. The quantity of water carried is expressed by the equation, Q = Av, where A is the area of cross- section of the conduit, and v is the mean velocity of the flow- ing water. Hence, the greater the velocity, the less may be the area of cross-section, and as a flume or pipe will admit of CULVERTS 321 322 CANAL STRUCTURES PIPES 323 high velocities without injury much expense may often be .saved by increasing the grade, and velocity, at the entrance of such a structure. The high velocity is also desirable to prevent the deposit of sand or gravel in a pipe. 12. Pipes. The use of pipe for conveying and distributing water for domestic use is nearly universal, and it has the impor- tant virtues of cleanliness, convenience and economy of water. The great expense involved generally prohibits its use for the large volumes of water handled in irrigation, except in Southern California and such localities where water has a very great value, and in special cases where pipe may be used as inverted siphons to carry water across depressions under pressure, or around steep hillsides where canals cannot be built. Short pipes are also used as culverts to carry drainage waters under roads, railroads or canals. The material of construction may be cast iron, sheet steel or iron, wood, reinforced concrete, vitrified clay, or cement. When properly constructed, reinforced concrete is the most permanent, and has been successfully used by the Reclamation Service for heads as high as no feet. For heads much greater than this, steel, cast iron or wood may be used. For heads below 20 feet clay tile or cement is sometimes employed without rein- forcement. Wood pipe is the most widely used pipe for irrigation, but the use of concrete is increasing, as it becomes better known and the cost of wood increases. Wood decays rapidly unless kept saturated with water, and its decay is much hastened by contact with earth, unless the saturation with water is thorough and continuous. Confinement of water under high pressure is the best means of keeping it saturated, and hence wood pipe should be used only under high pressure, unless it is laid under water or in ground perpetually saturated. Where pipe is exposed to the air, or to dry earth it may require a pressure of 50 feet head or more to force the water through the pores of the wood fast enough to supply the evaporation from the surface. The head required is of course much greater in an arid than in a humid region with less evaporation. Where the head is less 324 CANAL STRUCTURES than 100 feet, especially in arid regions, the pipe should be protected from contact with earth, and its life may be greatly prolonged by keeping it well painted outside. A good practice is to build a pressure pipe of wood for the distance where its pressure head exceeds 50 feet, and build the ends of reinforced concrete where the pressure is less. The pipe should be left full of water during the non-irrigation season, and any con- siderable loss from leakage should be replenished. Redwood is the most durable wood for this use, but cedar and Douglas fir are good and many varieties of pine have been used. Wooden pipe was formerly manufactured by boring the center out of logs, and such pipe is reported to have had a durability of over 200 years in England, and over 100 years in Philadelphia, under conditions where it was continuously saturated with water. . The bored log is very wasteful of material, and has been superseded by two modern types, both widely used in irrigation work, namely the continuous stav^e pipe, and the wire-wound pipe. Continuous stave pipe is built in place of staves carefully milled from selected lumber, to have concentric circular surfaces and radial edges. The ends of the staves are arranged to break joints, and are joined by metal plates inserted in sawkerfs in both staves, and slightly wider than the stave. The staves are held in place by steel bands, the ends of which are lapped in a cast-iron shoe, and one is fitted with a screw nut which is used to tighten the band. Specifications found in Chapter XXII of this book give in detail the best modern practice. Wire-wound wooden pipe is made in joints of convenient length, by placing the staves in the position desired, and binding them firmly in that position by winding heavy wire around them in spiral form. The lengths manufactured vary from 20 feet for small diameters, to 8 feet for the largest. The pipes are usually from 4 inches to 24 inches in diameter, though larger and smaller sizes are sometimes used. Larger sizes than 36 inches can best be made on the ground, of the continuous stave type. Where water freezes in the pipe during winter it should be PIPES 325 carefully examined for leakage before the opening of the 'irriga- tion season, and repaired if necessary. There is little economy in using wooden pipe for pressures exceeding 200 feet, as above that head the necessary steel in the bands is nearly sufficient for heavy steel pipe, which is thus much cheaper. Wood pipe, has, however, been used for heads up to 400 feet, where the short length of such head did not justify a change in design. Reinforced concrete pipe may be manufactured in place by means of portable forms, and good results have been obtained in this way. It is necessary to keep the work going continu- ously, or nearly so, as concrete does not bond well with other concrete that has been cured. The difficulty of entirely accom- plishing perfect continuity, and of obtaining thoroughly first- class work under the handicaps of field conditions, led to the introduction of another method, by which the pipe is constructed in sections of about 8 feet, in a yard where ideal conditions can be approximated and the concrete can be made particularly dense and ideally cured. After thorough seasoning, these are hauled to the field, and placed during weather as cold as permis- isble without freezing the mortar used in forming the joints. A movable collar form is placed at each joint, and a rich cement mortar is poured in at the top and thoroughly rammed. As soon as the forms are removed, the joints are covered with wet burlap and kept moist continuously for several days. By placing the pipe in cold weather while it is contracted by cold, any rise of temperature places it in compression and tends to prevent cracks. It should be backfilled as soon as possible after seasoning the joints. Pipe 46 inches in diameter, made and laid in this manner near Hermiston, Oregon, has withstood a pressure of no feet for several years without notable leakage or any repair. Steel pipe is often used for heads exceeding 60 feet, but is seldom economical for a less head. It Is commonly formed by curving a sheet of steel till the edges lap, and riveting them in that position. If considerable head must be withstood it is greatly strengthened by having two rows of rivets, parallel. 326 CANAL STRUCTURES Another and more efficient method of riveting is to wind the steel in a spiral and fasten the spiral lap seam by a single row of rivets. The transverse seam is formed by forcing the end of one joint into another far enough to rivet, or if the pipe is especially heavy, making a butt joint with an exterior sleeve riveted to each pipe. The life of the pipe is greatly increased by keeping it well coated with paint or tar. The smaller sizes of steel pipe are formed by welding the longitudinal seams instead of riveting, and are joined by screwing the ends into exterior sleeves made to fit. Lock-bar pipe has the longitudinal joint formed by upsetting the edges of the plate, and inserting them in grooves of a bar which are then closed by hydraulic pressure. This makes a joint equal to the strength of the plate if the workmanship is good, and avoids the interior roughness caused by rivets. The use of small pipe in distributing irrigation water is rapidly growing as water becomes more valuable, and the means of the irrigators grow. Where this is simply a substitution for open ditches it is customary to employ cement pipe, which can be manufactured in place by machines used for the purpose. Cement pipe without reinforcement is often used to cross undula- tions involving pressures up to 15 feet, and hao been used for 20-foot pressures. In these cases, however, it must be built with especial care, and heads above 10 feet should be avoided when practicable, or a light reinforcement in the form of a spiral steel wire may be used. The use of cement pipe as of cement- lined ditches is growing and is to be commended and encouraged. There are many formulae for computing the discharge capac- ity of pipes, all based more or less on experiment, seventeen of which are given in the Engineering Record, Vol. LXVIII, p. 667. The most noted of these perhaps are those of Bazin, D'Arcy, Kutter and Weisbach, which all differ considerably in results. A careful study of these, and the reasoning on which they are based, leads to the conclusion that great refinement of com- putation is useless, and that we can hardly hope with present knowledge to predict much nearer than 8 or 10 per cent, the capacity of any pipe in advance of its construction, and that PIPES 327 p 328 CANAL STRUCTURES PIPES 329 L FIG. 1 60. Removing Inside Steel Forms from Concrete Pressure Pipe, Boise Project. FIG. 161. Manhole and Concrete Collars on Concrete Pressure Pipe. Boise Project. 330 CANAL STRUCTURES such a margin of safety should usually be provided where the capacity is important. The U. S. Reclamation Service has adopted the following formulae for the capacity of pipes used in irrigation and drainage : Wood-stave pipe Q = 1.35 D 27 H 555 Cast-iron pipe <2 = i-3i D 27 H 555 Concrete pipe Q = 1.24 D 27 H 555 Riveted steel Q = 1.18 D 27 H 555 Drain tile Q= D 27 H 555 where Q = Discharge in cubic feet per second ; D = Diameter of pipe in feet ; H = Available head in feet per 1000. 13. Tunnels. Where the canal location must leave the contour grade line in order to avoid a long detour around a ridge or hill, or to escape a hazardous location on its steep slopes, it may pass through the hill in a deep cut, or if this is too deep, may tunnel through. Whether a cut or tunnel is to be preferred depends mainly upon the depth of cut and the character of material, and is chiefly a question of cost. Other conditions being equal, a tunnel is to be preferred, as it will generally give less trouble and expense in maintenance. There is frequently presented also the alternative of going around on a grade line in a flume or canal, or a combination of both. The cost must be largely in favor of the latter to justify its construction, as side-hill canals and flumes are expensive to maintain, and may be very hazardous. This depends largely on the material, and is not easv to estimate in advance. Cases are not rare where a canal located around a hill gave so much trouble by seepage and developing slides that it was later abandoned for a safer location in tunnel. In a majority of cases tunnels require lining to prevent caving or swelling of the material in which they are built, and in many instances where this is not the case lining may be advisable to present smoother surfaces to the flowing water, reduce the friction and thus increase the capacity. This is TUNNELS 331 generally the case where grade is valuable, but where there is a surplus of grade and the rock is hard and firm, the lining may be omitted from a tunnel of moderate size. A small tunnel with good smooth concrete lining will discharge nearly twice as much water as one with rough rock interior of the same dimensions and grade. A lining may in some cases be required to prevent loss of water through crevices in the rock, but such conditions are infrequent in material firm enough to stand without lining. The smallest tunnel in which it is economical to carry on heavy work is about 4 feet wide and 6 feet high, and there is little or no economy in making a tunnel smaller than this. It is best to leave about a foot of vacant air space above the water in any tunnel, to prevent waves or any chance obstruction from causing the water to touch the top of the tunnel, and thus causing it to " seal," that is to fill to the top, and thus increase the friction which would reduce the velocity and resulting discharge. It is generally advisable to construct the top of a tunnel in the form of an arch. This shape has a tendency to resist caving of the top and gives the maximum holding power to any lining that may be provided. It also provides an air space that is effectual against sealing without sacrificing much cross-section for this purpose. The sides of the tunnel are generally straight vertical lines, and the bottom a straight horizontal line, or a slight curve concave upward. It is generally considered cheapest to make such simple lines, especially in case lining is required, for which forms must be provided. This advantage, however, is not great, and wherever the ground to be tunneled is insecure, greater resistance to caving may be secured by giving the per- imeter of the tunnel a curved form, so as to present arch action in every direction against outside pressure. For this purpose a circular section is sometimes provided, but .this is incon- venient of construction and not entirely logical for its purpose. The first tendency of caving ground is downward in obedience to gravity, and where this is resisted, and the mobility consider- able, a secondary tendency is in a horizontal direction. It is therefore logical to build the top of the tunnel on a curve of shorter radius than that of the sides or bottom, but to curve 332 CANAL STRUCTURES these also, if outside pressures are to be expected. A logical and convenient shape conforming to these principles, has become standard, and is as follows: The top of the tunnel is a half circle, drawn to such radius as the desired capacity requires, which may be indicated by the symbol R. From each end of the horizontal diameter, with a radius 2R, an arc is described connecting with the half circle and continuing its lines downward. From highest point, or apex of the circular top as a center, with a radius 2R, an arc is described to form the bottom or invert of the tunnel, intersecting the sides. This shape is shown in Fig. 250, and is sometimes called a " horseshoe " section, for obvious reasons. Clay and shale and some other materials have a tendency to swell when exposed to atmospheric influences and may con- tinue the swelling process long after lining has been placed. Where such tendency exists, it is important to employ a curved section of lining in order, by arch action, to resist the thrust of the " swelling ground." Where it is desirable to Duild the tunnel of the smallest economical size, the invert may be drawn to a radius of 3^ instead of 2R, and by giving the R a value of 2 feet, we obtain an extreme height of 6 feet and an extreme width of 4 feet, which is about the minimum desired. The standard section, however, Fig. 249, produces a greater hydraulic radius, and hence involves less friction losses, and wherever it gives a total height of 6 feet or more, is more convenient and hence more economical in construction and operation. The equipment and operations for tunnel construction vary widely. They depend chiefly upon the character of material and the length of the tunnel. Tunnel work at best is quite slow. The room for work is so restricted that only a few men can engage upon it at one time, and if the tunnel is very long it generally is the feature that determines the necessary time consumed in the construction. The utmost speed therefore becomes important and it is cus- tomary to work night and day upon both headings. If any central portion of the tunnel is near enough the surface TUNNELS 333 to be reached from a shaft of moderate depth, this may be made a means of expediting its completion by affording other points of attack. Sometimes it may be entered at the side from a canyon nearby through a branch tunnel called an adit. In deciding upon the location of the tunnel it is not uncommon to deviate from a straight line sufficiently to permit the use of an adit to cheapen construction and expedite completion. The length of a tunnel not only increases the time of con- struction but greatly increases the unit cost. It determines the distance through which men must travel to and from their work and through which all the excavated material must be transported and all of the materials for timbering and lining the tunnel must also be taken, together with gpwder and other materials for construction. A long tunnel must also be provided with ventilation. The gases generated by explosives are unfit for breathing and may be very injurious or fatal if taken into the lungs in considerable quantities. It is therefore necessary to provide ventilation by some means. With a short tunnel it may be feasible to work only alternate shifts or to provide such intervals between shifts that the gases will dissipate themselves so that artificial ventilation may not be necessary. As the work advances farther and farther from the entrance, artificial ventilation becomes more and more necessary, especially if speed require- ments are such as to prevent the suspension of work for con- siderable intervals. Necessary ventilation is generally provided by running light sheet-iron pipe from the portal or from a shaft and with a blower either pumping air from the heading or forcing fresh air in to displace it. Usually the suction process is used immediately after the blast to bring out the concentrated gases. When these are fairly well disposed of the current is reversed and fresh air blown in next the heading. In this way only a few minutes need be lost from the work after a blast and by setting the blast off just before meal time the atmosphere is satisfactory for the resumption of work immediately after the meal is finished. There is a large variation in the speed that can be achieved 334 CANAL STRUCTURES in constructing a tunnel, even where the best facilities are provided. Where the material is of shale or of indurated sand or similar substances which are sufficiently coherent to stand temporarily without much timbering and yet are soft enough to be cut rapidly with power augers and do not require the slow process of drilling, the work can proceed rapidly and 20 or 25 feet of progress may be made in one day on a single heading. Where the rock is hard, requiring much drilling, the process is necessarily slow .and may be only a tenth of what it would be under the most favorable circumstances. TABLE XXXII. TUNNELS Project Tunnel Capacity, Sec. ft. Length, Feet Cost Excl. G. E. Cost per Foot Grand Valley No i I42s 7,723 $265,200 $71 Grand Valley .... No. 2 1425 1,655 117,400 71 Grand Valley No. 3 670 7,292 334,ioo 46 Uncompahgre .... Gunnison IOOO 30,645 3,100,000 101 Sun River Pishkun No. i IOOO 695 54,100 78 Sun River Pishkun No. 2 IOOO 1,022 80.900 79 Sun River Pishkun No. 3 IOOO 2,277 142,700 63 Klamath Main Canal. I2OO 3,^OO 190,700 58 Belle Fourche. . . . S. Canal 35 I,3O6 33,200 25 Strawberry Strawberry 600 19,897 1,076,000 54 Strawberry Power Canal No. i . . 500 800 27,600 34 Strawberry Power Canal No. 2. . 500 705 21,800 3i Okanogan Conconully Outlet ooo 39C 12 800 32 Yakima (Tieton) . 6 tunnels 300-350 11,863 397,100 33 Shoshone Corbett IOOO 17,355 1,133,000 65 The most difficult tunnel work, however, is where the material to be penetrated is running sand which requires close tight timbering to prevent enormous caves and filling of the tunnel with loose sand. Various means of solidifying this have been suggested, but without much success so far. One method is to inject water into the sand ahead of the work, which makes it more coherent and affords time for placing timber after excava- tion. Another suggestion is to inject cement grout for the same purpose. These processes present difficulty in securing an even HIGHWAY CROSSINGS 335 distribution of the injected material, but where this can be accomplished they help materially in holding the refractory sand. The above table of tunnels constructed by the Reclama- tion Service, shows the entire cost excluding overhead, general and indirect charges, and show a great variety of unit costs. The highest unit cost, that of the Gunnison Tunnel, is due partly to the fact that it is the longest in the list, but still more to the extremely difficult and hazardous conditions there encountered. These included great deposits of mud and gravel which were difficult to hold, large quantities of water, much of it scalding hot, and numerous difficulties with carbon dioxide and explosive gases imprisoned in the rocks and liberated by the tunnel work. The construction was frequently shut down from these means; heavy pumping, elaborate ventilation and equipment were re- quired, and in the process many lives were lost. Tunneling is a highly developed specialty, requiring for economical and efficient prosecution a high degree of skill in the use of explosives, in the timbering and holding of refractory material, and in organizing, training, and operating a crew to work efficiently under cramped and disagreeable circumstances. 14. Highway Crossings. In general it is necessary to provide highway bridges where irrigation canals cross public highways in use at the time the canals are constructed. These should usually have abutments of concrete or steel cylinders filled with concrete, as wood will rapidly decay in contact with earth. The superstructure of small bridges may properly be built of wood, and the larger bridges requiring trusses may have all compression members of wood and the tension members of steel. It is very undesirable to permit any piers in the water prism of the canal, as they cause some loss of head, and catch drift- wood, weeds, etc., and increase maintenance cost in several ways. Where it is necessary to cross existing railways, the railway company is sure to require a very safe structure, and there is sometimes a tendency to carry this requirement to an extreme. There should never be reluctance to provide such structures 336 CANAL STRUCTURES m FIG. 162. High Line Canal, Spanish Fork Valley, Utah, Covered to Protect against Land and Snow Slides. FIG. 163. Headgates, Sluice Gates, and Sand Basins, High Line Canal, Spanish Fork Valley, Utah. SAND TRAPS 337 with ample margin of safety, as a failure might lead to the wreck of a railway train, an accident usually far more serious than a canal break. Crossings of railways established after the canal is built should be at the expense of the railway, and should be of the same character and margin of safety as those built at the expense of the canal authorities. The same rules apply to highway crossings required after the construction of the canal. Where the grade of the railway or highway is several feet above the surface of the canal water, and the canal is not too large, it is best to carry the road across on a fill over a culvert provided for the canal water. This avoids interference with the road in any way, and the earth distributes the pressure upon the culvert. Where the grade of the canal is about the same as that of the railroad, it is seldom that the latter is willing to change its grade, and it becomes necessary to introduce a pressure conduit to carry the canal under the railway. The chief objection to this is the tendency to collect sand and silt in the conduit under the railways. Where possible the conduit should be given a velocity sufficient to carry through any material the canal can bring in. For this purpose, velocities of 3 feet per second for silt, 4 feet for sand, and 5 feet for fine gravel will prevent deposit, but higher velocities may be required to pick up and carry out material previously deposited. Where it is not feasible to provide increased velocities, it may be necessary to provide that the lowest point of the conduit be at one side of the railway, where it may be cleaned out through a manhole. This is seldom necessary unless the canal is heavily silt bearing. 15. Sand Traps. The frequent presence of sand in canals where it is often a serious nuisance, requires the employment of devices by which it may be removed and these are variously called, sand traps, sand boxes, sand gates, and sluicing devices. On p. 250 reference occurs to devices for preventing or minimizing the entrance of sand into a canal from the river. These are not always possible, and where provided are seldom completely effective, and hence, where water is taken from a sandy stream, it is usually necessary to employ some means to get rid of the 338 CANAL STRUCTURES sand entering the canal. In addition to this, the canal may receive sand from side drainage taken into the canal. The objections to sand in the canal are several: i.It. tends to deposit in siphons near the inner bank on curves, and at other points where the velocity is checked or eddies occur, and to form bars which reduce the capacity of the canal, and cause much annoyance and expense in their removal. 2. Sand occurring in water carried through siphons, flumes, or lined channels at high velocities, has a tendency to wear such channels, or other structures subject to the abrasion of the sand. FIG. 164. Cross-section of Sand Box, Santa Ana Canal, Cal. 3. Sand occurring in water to be used for power causes rapid wear and destruction of water wheels. 4. Where sand, is successfully carried through the canal system to the farm, which is difficult to accomplish, it soon fills the farm distributaries, and as it contains very little fertility it is a nuisance without redeeming benefits. 5. Sediments of all kinds and sizes carried in a feed canal to a reservoir tend to fill the reservoir and destroy its storage capacity. SAND TRAPS 339 The first four of these objections do not apply in the .same degree to the finer sediment in the form of silt or clay, which have less tendency to deposit and clog the works, and contain a much larger percentage of available plant food, and although these finer sediments do cause some annoyance and expense, they are, when in moderate quantities, much to be desired for their fertilizing value when deposited in the field, and such sediments deposited in moderate quantities in the canal system, tend to seal it and thus to reduce seepage losses, especially where the canal is located in coarse and porous materials. A film of clay over the perimeter of a canal also tends to reduce friction and thus increase discharge. FIG. 165. Sand Box, Leasburg Canal, Rio Grande Valley, New Mexico. Fortunately the coarser particles, which are so objectionable, are more easily separated from the water by settlement, and it thus becomes practicable to eliminate them in a large degree. The measures available for combating the sand nuisance may be divided into two classes, one of which is essentially preventive and the other curative: 1. Processes of settling, sluicing and skimming the water so as to prevent the entrance of sand into the canal. These are preventive measures. 2. Processes of settling the sediments in basins or depressions in the canal system, and sluicing them back into the stream, or into other drainage lines. The preventive measures are described in the article on headworks on p. 248. Various devices are employed to rid the canal waters of sand. 340 CANAL STRUCTURES In the vicinity of cross- drainage or of the parent stream the canal may be given an abnormally large section and a depressed bottom, and the slow velocity corresponding to the enlarged section causes a deposit of the heavier and coarser solids, which are depos- ited in the bottom of the en- larged section. A gate or set of gates is provided with its sill at the bottom of the depressed portion, and when this is opened, the increased grade induces a high velocity over the deposited sediment, and the rushing waters carry it out into the drainage line utilized, which is flushed by its natural freshets. The efficiency of this method may be increased by providing a false bottom to the canal on a level with its normal bed. This false bottom may be formed of triangular bars with a sharp edge upward, spaced a slight distance apart, so that sand set- tling will fall through between the bars, to the bottom of the depression. The space below this false bottom, should be provided with curved guide walls or grooves to guide the water to the sluice gates. The false bottom serves to prevent upward currents and SAND TRAPS 341 eddies that retard settlement of the sand, and the curved guide walls accelerate the sluicing velocity of the water and facilitate the movement of the sand under its influence. The channels between the guide walls may be each provided with a separate gate so that they may be separately sluiced if desired. The combined capacity of all the gates should be somewhat greater than the capacity of the canal, in order to achieve maximum efficiency. Where the canal waters are carried across a stream or a large ravine in a flume, this may be provided with a series of hoppers reaching below the grade of the flume, in which the sand may settle, and a valve in the bottom of each hopper may be opened at proper intervals to let the sand fail out. Some device of this kind is generally employed just above a power plant fed by a canal from a sandy stream. It is also wise to provide such an arrangement for desilting above a pressure pipe or inverted siphon where low velocities occurring at times when the canal is being used at part capacity might clog the pipe with deposits of sand if not prevented. Desilting devices are in successful practical operation in numerous localities, and their efficiency is greatly assisted by the fact that the coarser particles of sand have a tendency to travel on or near the bottom of the stream. A considerable proportion of the coarsest are simply rolled along the bottom in miniature waves or dunes of sand, and are easily deposited in traps like those described. In some cases settling basins are arranged in duplicate, side by side, so that while one is in use the other may be cleaned, and thus by alternating the closure of the canal is avoided. CHAPTER XV STORAGE RESERVOIRS i. Classes of Storage Works. Reservoirs are employed to regulate the flow of water in such manner as to accommodate the rate of use, and prevent waste when the supply exceeds the demand, holding it for use at the time the requirements exceed the natural supply. The storage of water for ordinary irrigation purposes requires favorable topographic conditions to make it financially feasible. Such conditions must make possible the storage of a large quantity in a broad capacious basin, wholly or partly natural, where the dam or other structures necessary to complete it are of moderate dimensions and cost, as compared with the quantity of water stored. A location where storage can be obtained at moderate cost is called a reservoir site, and such sites may be classified with respect to their topographic features into four classes as follows: 1. Natural lake basins; 2. Those located on natural drainage lines, the flow of which they regulate; 3. Those located in depressions away from natural streams, requiring the water for storage to be conducted to them; 4. Artificial reservoirs located in places having no special natural adaptation to such use. Natural lakes are often, in their natural state important regulators of drainage waters which they receive. By con- trolling the outlet, by means of a dam and regulating gates, a large amount of storage may often be secured very cheaply; the cheapest storage works in the world in proportion to capac- ity, are those which utilize natural lake basins. 342 SELECTION OF A RESERVOIR SITE 343 The most abundant reservoir sites are those on natural drainage lines, but they require careful precautions to safely discharge the flood waters of the stream, and are often quite expensive in proportion to capacity. Many natural depressions in plains or benches partially enclosed by high ground can be converted into reservoirs by banks of moderate dimensions to close the gaps between the hills, and many natural " dry lakes " can be made available by cutting outlets to draw off stored waters. Such reservoirs must have their water supply carried to them by canals from natural streams. Some reservoirs are constructed on small drainage lines on account of favorable topographic conditions, and receive their main water supply through feeders from larger streams in the neighborhood. Natural depressions, forming dry or intermittent lakes, are sometimes caused by the collapse of subterranean caverns caused by the solvent and erosive action of subterranean waters, or otherwise. Depressions thus formed are unsuitable for reservoirs on account of the easy escape of the waters through the subterranean passages in their vicinity. Dry lakes should be carefully examined for the existence of those conditions, before being adopted as reservoir sites. Artificial reservoirs are sometimes constructed by excavating basins and using the material in the formation of banks to confine the water. Such reservoirs are very expensive per unit of storage capacity, and can be used only in cases where water has a high value, as for domestic purposes or the irrigation of gardens. Shallow reservoirs are usually to be avoided, as the losses from them by evaporation and percolation are relatively large, and where they are shallow enough to permit the sunlight to penetrate to the bottom, they are likely to be infested by aquatic vegetation. To prevent the growth of this, shallow reservoirs for city supplies should be covered to exclude the sunlight. 2. Selection of a Reservoir Site. Among the more important considerations affecting tke feasibility and value of a reservoir site are: i. Its relation to the irrigable lands. 344 STORAGE RESERVOIRS 2. Its relation to the water supply. 3. The topography of the site. 4. The geology of the site. A careful examination should be made of the region where storage is desired, to discover all possible reservoir sites and compare their value and cost in order that the most favorable may be selected. This requires a practiced eye and trained judgment capable of selecting the most advantageous locations for survey, otherwise much time and money may be wasted on the survey of indifferent locations. The reservoir must lie at a sufficient altitude above the irrigable lands to permit the delivery of water to them by gravity flow, or in special cases by pumping to moderate heights, and should be as near as possible to those lands so that the losses in transportation may be small. The site must be at such a point as to intercept a sufficient water supply, or so that such a supply can be conducted to it. Where the reservoir is on a stream, it often happens that it is such a distance above the lands to be irrigated that when the water is needed it is released from the reservoir and allowed to flow down the stream bed for some distance, until it reaches the point where it is necessary to divert it to reach the lands for which it is intended. If this distance is long, consideration must be given to the losses in transit to be expected. Due regard must also be had to the drainage intercepted by each possible site, and the bearing of this element on the water supply. It is always desirable to locate the reservoir as near as pos- sible to the irrigable lands, as otherwise, the long time required in transit from the reservoir to the lands makes it difficult to regulate the water supply according to the fluctuating needs of irrigation, and much water must be wasted most of the time in order to insure a full supply when needed. 3. Geology of Reservoir Sites. Having ascertained the desirability of the reservoir site topographically and hydro- graphically, the geology should be carefully studied, to ascertain the character and dip of the strata underlying the proposed reservoir. The geological conformation may be such as to GEOLOGY OF RESERVOIR SITES 345 contribute to the efficiency of the reservoir, or it may prove so unfavorable as to be irremediable by engineering skill. A reservoir site which is situated in a synclinal valley is gener- ally favorable. In this the strata incline from the hills towards the lower lines of the valley, and water which may fall on to these hills will find its way by percolation into the reservoir, thus adding to its volume. An anticlinal valley is much less favorable for a reservoir site. In such a valley as this the strata dip away from the reservoir site and may permit of the escape of much of the impounded water. A class of geological forma- tion intermediate between these two is that in which the valley has been eroded in the side of strata which dip in one direction. Here the upper strata tend to lead water from the adjoining hills into the reservoir, while the strata on the lower side tend to carry it off from the reservoir. If the surface of the proposed reservoir site is composed of a deep bed of coarse sand or gravel the percolation through this may be so great as to seriously impair the efficiency of the reservoir. The most careful scrutiny should be given to reservoir sites in regions of extensive lava flows, as such formations often contain hidden crevices and caverns through which the water may escape from the reservoir. Oregon, Idaho and Arizona each furnishes an instance of bad holding power of a reservoir built in lava formation. Limestone and gypsum formations are also liable to caverns and in gypsum especially these are frequent, and are subject to rapid enlargement by erosion and solution by the waters that may leak through them. Natural basins or " dry lakes " are sometimes formed by the collapse of such caverns, and where it is proposed to employ such basins as reservoirs, careful study should be made of the geology before deciding upon its construction. Where caverns, crevices, or gravel beds under the reservoir afford easy escape for ground water, no dependence should be placed upon an overlying blanket of soil to make the reservoir tight, as the losses by vertical percolation through such soil 346 STORAGE RESERVOIRS will be too great for satisfactory results, provided there is free escape for the percolating waters. To illustrate this, let us suppose a reservoir covering 5000 acres of any average depth of 50 feet, and having, therefore, a storage capacity of 250,000 acre-feet, and that the ground sur- face of the reservoir site is composed of average alluvial soil, underlain with coarse gravel, or with cavernous rock, which affords' ready escape for any water reaching it. The table on p. 235 shows a coefficient of seepage from good canals of .5 foot per day. The seepage loss from the reservoir would at that rate, be when full, 2500 acre-feet per day, or a rate sufficient to empty the reservoir in 100 days. The great head on a deep reservoir would greatly accelerate the rate of seepage, and the decline of the water would diminish the wetted area, but it is readily seen that such a reservoir would be worthless for most purposes. The good holding qualities of many reservoirs with earth bases is explained by the fact that in some cases they are backed by rock which is nearly impervious, and in which such crevices and interstices as exist are soon filled with water, and are of such minute dimensions as to make the escape of such water extremely slow. In other cases the seepage from the reservoir is large at first, but having no ready escape to an open stream, gradually raises the ground water, until this rises to the surface, and then we have a tight reservoir, in which the leaks are sealed with water, which can escape only very slowly, in a direction nearly horizontal. 4. Leakage from Reservoirs. It is useful in this connection to review some instances of reservoirs that have developed abnormal leakage in such degree as to become nearly or quite useless. Tumalo Reservoir. This reservoir was built by the State of Oregon in connection with the Tumalo Project. Prior to its construction, a board of engineers recommended that it be first built to only partial capacity, and that it be tested for water tightness before heavy expenditures were incurred. It appeared, however, that this would delay completion until the appropria- tion for its construction would lapse into the general fund, LEAKAGE FROM RESERVOIRS 347 the wise recommendation was disregarded, and the dam' was completed to. its full height. Water was delivered to the reservoir through the feed canal, until it had risen about 20 feet above the outlet. At this juncture a large hole developed in the bottom of the reservoir about 1000 feet from the dam, discharging over 200 cubic feet per second, which soon emptied the reservoir. This hole was puddled, and the water ( again turned in, but new breaks in the bottom occurred, and it was found impossible to raise the water again to the height first attained. The holes developed varied from small cracks to as much as 50 feet across, and from 10 to 30 feet deep. Sometimes the ground would drop very suddenly. Considerable money was spent in puddling these holes, and the rapid flow through them has been stopped; but seepage over the whole submerged area occurs to an extent sufficient to render the reservoir worthless for storage. When the water covered a surface of 30 acres, the observed loss was from 6 to 8 inches per day, which is normal seepage through good earth, but too rapid for storage requirements. The country rock is of igneous origin and is so fissured that the ground water escapes rapidly to the Deschutes river, thus giving free vent to the water of the reservoir as fast as it can penetrate the surface soil. The Deer Flat Reservoir is located on the valley near Boise, Idaho. It is formed by joining a series of low hills by embank- ments, and is supplied with water by a canal from the Boise River. It is about 10 miles from the nearest point of the Boise River, and its bottom is about 100 feet above the river at that point. When full it covers an area of 9800 acres, and contains 180,000 acre-feet of water. It was placed in service in 1909, when about 60,000 acre-feet of water were run into it, the greater part of which was lost by seepage, and not more than 17,000 acre- feet was in the reservoir at one time, 2500 acres being then submerged. The next year 3900 acres were submerged, and about half of the water was lost by seepage. Many persons believed the reservoir was doomed to failure on account of 348 STORAGE RESERVOIRS 1916 FIG. 167. Curves of Seepage from Deer Flat Reservoir, Showing the Improve- ment with Use, LEAKAGE FROM RESERVOIRS 349 excessive losses, but subsequent service showed rapid improve- ment, and in 1917 the seepage losses were equivalent to less than 2 tenths of an inch per day, or about equal to the evap- oration. TABLE XXXIII. DEER FLAT RESERVOIR LOSSES Year Mean Acreage Sub- rr.erge i Maxim urn 1 Acreage Sub- merged Evapora- tion in Acre-fee. , Total Loss in A ere- fee: Seepage Loss in Acre -feet AVERAGE SEEPAGE Loss Acre-feet Inches per Acre per Day IQOQ L355 2.500 4.;50 57.600 - 39. 1.28 IQIO 3.002 3.900 10.500 c ?45j 4.983 * 0-93 I9II M 59 6.300 15.600 r 5 c.- I35-238 30-3 I. 00 IQI2 4-625 ; 7.000 16.200 85.080 68.889 14.9 0.49 IQI3 5.^50 8.200 18.400 89.489 71-089 13-5 0-44 1914 5-337 l 8.400 18.700 - : 084 63.384 12.0 0.40 1015 5-i- n 3 8.100 17.900 67.400 40.500 97 0.32 1916 4-S20 i 6.000 16.900 43.970 27.070 5.6 0.18 IQI7 4.500 ---.-: II.OCO ::.4co 21.400 48 o 16 Mean Total 4-274 6.540 14-440 78.150 5^- ; * > 5o j 120.950 704.353 The losses during 1009. IQIO and 19 n were less per area submerged than would be expected in a canal in good tight soil, and in the last two years this is reduced to less than what might be expected from a canal with heavy concrete lining. The steady improvement and remarkable tightness attained are due to the tilling of the subsoil with water which cannot rapidly escape, and not to any abnormal tightness of the soil. Lake McMillan. On the Pecos River, near Carlsbad. Xew Mexico, is a project originally designed and built by a private corporation, in a region in which the country rock is mainly gypsum, or sulphate of lime, a very soft rock easily eroded by water, and to some extent soluble therein. The main reservoir. Lake McMillan, is formed by a dam across the Pecos River. and the eastern bank of the reservoir is formed by a gypsum bluff. When the reservoir was filled, the water freely entered crevices in this blutt. and found ready escape underground. 350 STORAGE RESERVOIRS away from the reservoir. By erosion and solution these open- ings steadily enlarged and were cut down to the bed of the river, so that they received and carried away the entire ordinary flow of the stream amounting to several hundred second-feet. Num- erous sink holes also appeared in the bottom of the reservoir into which the water escaped in considerable quantities. The main leaks in the gypsum bluff were excluded by building an earth and rock dike parallel to the bluff for a length of about 4000 feet, to a height of 19 feet. The holes in the bottom are puddled from time to time, but not completely cured. Hondo Reservoir. In the same valley, near Roswell, N. M., a reservoir was formed by a natural depression which was increased by connecting the surrounding hills by dikes, and water was supplied through a feed canal. Leaks developed soon after the water was turned into the reservoir, and these rapidly increased by the enlargement of holes in the bottom of the basin, which apparently connected with subterranean caverns. Efforts at puddling the leaks were una\ ailing, and they increased to about 200 cubic feet per second, and the reservoir had to be abandoned. The country rock in this region is composed largely of gyp- sum, which is readily eroded and dissolved, and contains water- formed caverns which constitute the seat of the trouble. The depression which forms the reservoir site may be due to the collapse of such caverns. Depressions of this nature are to be regarded with suspicion. Walnut Canyon Reservoir. In Walnut Canyon, Arizona, a reservoir was built to store water for railroad uses by the Atchison, Topeka & Santa Fe Railroad Company, but although the dam was tight and the ear them bottom appeared good, the losses have persisted at the rate of more than half a foot per day over the submerged area, and this is sufficient to nearly empty the full reservoir in about seven months, and largely destroys its value. The country rock is sandstone, and evidently has enough seams to carry off the water fast enough to keep the water table down, and keep the seepage in progress in nearly a vertical direction. The rate of seepage is not as great as LEAKAGE FROM RESERVOIRS 351 generally occurs from a well-built canal in good earth, and much less than a majority of the canals in service, yet it is great enough to destroy most of the benefits expected from this reservoir. The North Side Twin Falls Irrigation System is built in a country underlain by lava rock through which Snake River flows in a gorge several hundred feet deep. Any crevices in the lava, therefore, have communication with this deep gorge, and water in them can readily escape, Numerous springs are in evidence on the walls of the canyon. The Jerome Reservoir is constructed on this plain, and fed by the Main Canal. In this reservoir the seepage losses are about 0.85 foot in depth per day, or about what would be expected from a canal in good earth. There are sufficient holes and fissures in the underlying rock so that the seepage waters have ready escape to the Snake River Canyon, and this rate of seepage is there- fore permanent and continuous so long as water is in the reservoir. As the area of the reservoir is 4000 acres, the seepage is over 2000 acre-feet per day on an average. This means a loss of over 60,000 acre-feet per month, which is so serious that the reservoir is considered practically worthless. Many holes developed in the reservoir bottom, usually starting from a badger hole, connecting with a blow hole in the lava, and enlarged until the hole in the lava received all the water it could carry. Most of these holes were less than 6 inches in diameter, but a few were found much larger. The smaller holes generally became clogged with moss and debris, and the rest were dug down to a depth of several feet, and care- fully puddled with earth, which usually made a permanent cure of the particular leak. The large loss of water, amounting to 1000 second-feet more or less, was due to the fact that the crevices in the under-lying rock would carry off the water as fast as it could filter through the soil. The absence of any water table, permitting the continuance of the seepage in a vertical direction, was the cause of the reservoir's failure, and this will be true of any reservoir, no matter how good the soil is, if the conditions permit the seepage to travel on vertical rather than nearly horizontal lines. 352 STORAGE RESERVOIRS Tule Lake is a broad shallow lake in Northern California. The basin was formed by a lava flow known as the " Modoc Lava Beds." The lake receives the entire flow of Lost River, which is disposed of by evaporation and leaking through the lava, which is very seamy. The indications are that the water formerly escaped through the crevices in the lava as rapidly as it entered, and that the lake in its present dimensions is of very recent origin, due to the clogging of the seams with drift, grasses, etc. A combination earth and rockfill dam, built for storage purposes on the Zuni River in New Mexico near an Indian Pueblo of the same name, had for its south abutment a lava- capped mesa, underlain with several strata of sand and clay which were exposed in the margin of the reservoir, and passing under the lava cap, cropped out in the canyon below. When the reservoir was filled, the sand strata leaked to an erosive extent, and soon developed a discharge estimated at 5000 cubic feet per second. This cut away the sand and clay, undermining the hard basalt cap, which fell a distance of 7 to 9 feet. It is often difficult to recognize in advance the conditions that produce failure of a reservoir from leakage, and where they exist, they appear to be generally irremedial. A few rules of caution may, however, be of use : 1. Avoid reservoir sites adjacent to gypsum deposits and to limestone deposits which show evidence of caves. 2. Reservoir sites in volcanic rock should be carefully examined for the prevalence of seams or cavities. 3. Coarse-grained sandstone should be regarded with suspicion. 4. Natural depressions are often treacherous and should be avoided if near cavernous rock or deep canyons, or are under- lain with coarse material where water might readily escape. Under such conditions, no superficial tightness will remedy the trouble. 5. Seams of sand or gravel in the reservoir and out-cropping below, are apt to cause trouble. SURVEY OF RESERVOIR SITES 353 5. Survey of Reservoir Sites. In order to furnish data for comparison, and for estimating the value and cost of contem- plated reservoirs, a careful preliminary survey of each is neces- sary. The catchment basin of each should be accurately out- lined and enough topographic information secured to show the general character of the soil and slopes and the runoff result to be expected therefrom. Stream measurements should be started early at such locations as will show the flow available for each site; inquiries of the inhabitants and others, and care- ful examinations of flood marks should be made to shed all possible light upon the maximum and minimum flow. Some determinations should also be made of the rate of evaporation to be used in each location. Each reservoir site considered should be surveyed topo- graphically, by means of a plane table. The highest point which the dam may reach should be considered, and the top contour of the corresponding reservoir meandered around the entire site, showing its outlines and total area. A main traverse should be run through the axis or lowest line of the site, ter- minating at the dam at one end and the top contour at the other. These traverses should be controlled in elevation by careful leveling, and from them enough intersections and stadia locations can usually be made to control the topography of the entire site unless it is timbered, in which case additional traverses may be necessary. The scale of the survey should be from 1000 feet to an inch for small or medium-sized sites, to 2000 feet to an inch or even smaller scale for very large sites where the map on a large scale would be unwieldy and inconvenient. The contour interval should be 10 feet for reservoirs with bold mountainous topography, and 5 feet for those of moderate slopes. When the contour map is completed the area enclosed by each contour should be measured by planimeter, and from these data the capacity for the various depths may be computed, and the results from various heights of dam compared. In computing the capacity allowance must be made for any 354 STORAGE RESERVOIRS dead space or unavailable capacity below the bottom of the lowest outlet, since the water below this cannot be drawn off. This space, will however, ordinarily fill with sediment in time, as all streams carry some sediment at times, and in some cases the accumulated sediment soon detracts from the capacity of the reservoir and its disposition becomes a serious problem. In general the streams in the upper portions of a drainage basin carry less solid matter in proportion to volume than those in the lower basin, and for this reason reservoirs on the upper reaches may be preferable to those below. This is especially the case with streams in the southwestern portion of the United States, which carry much sediment. 6. Spillway Provisions. It has been said that the most important feature of an earthen dam is the spillway; and in the sense that it is the essential feature that is most often neg- lected, this is perhaps true. This is due largely to the extreme uncertainty of the contingency to be provided for, and the certainty of disaster if the water is allowed to overtop the embankment. It is easy to calculate water pressures and allow for them, and the permeability of materials can be tested and controlled. But who can tell the magnitude or manner of occurrence of the largest flood on any stream that the future has in store? Even where a long record is available serious errors are possible. The floods of 1913 in the Miami Valley swept away structures that had stood unharmed for half a century. Nor is it certain that the flood of 1913 will never be exceeded. The plans adopted for controlling such floods contain provision for a much larger flow. A board of experts once carefully studied a history of forty years on the Sacramento River and concluded that the greatest flood to be expected there was 80,000 cubic feet per second. A few years after this a flood occurred exceeding 200,000 cubic feet per second at the same point. The Sweetwater Dam in Southern California was built of masonry with a spillway capacity of 1500 second-feet, which was the estimated discharge of the greatest flood within the SPILLWAY PROVISIONS 355 memory of the " oldest inhabitant." A few years after .the completion of the dam it was overtopped and much damage done by a flood approaching 18,000 cubic feet per second. The damage was repaired and spillway capacity provided for about 20,000 second-feet. In 1915 this capacity was exceeded and considerable damage resulted that could have been obviated by a larger spillway. Before the construction of the Cold Springs Dam in Oregon a careful examination was made of the valley for signs of floods, but none were found indicating any considerable overflow of the waterway, the capacity of which was less than 1000 second-feet; yet during the construction of the work, a heavy rain falling on snow caused a flood of over 6000 cubic feet per second. These examples show the futility of depending on local signs or short records, or even upon fairly long records unless a liberal factor of safety is applied to their indications. It would be indeed marvelous if an available record of ten or twenty years should contain the largest flood of all the centuries. The floods of 1913 in Ohio and Indiana appear from the evidence to have exceeded by 40 or 50 per cent any that had occurred there for 105 years and to be considerably greater than the next highest in 1805. In 1827 the Ardeche River in France was visited by a flood much greater than any that has occurred in the succeeding ninety years. , The flood of 1846 in the Loire River in France has not been equaled since that date. Many illustrations might be cited of the fact that extreme local rainfall or runoff may occur only at long intervals of time but are nevertheless likely to occur. It is necessary, therefore, in estimating extremes to be provided for to consider the extremes observed on areas as nearly similar as possible, and to allow a factor of safety sufficient to eliminate all risks involved in the necessary assumptions, giving due regard to the time and geographic extent covered by the available data. Comparatively few measurements of great floods have been made. Systematic stream measurements of accuracy are 356 STORAGE RESERVOIRS TABLE XXXIV. EXCESSIVE RAINFALLS Station Kiev. ! Aver- age An- nual Date INCHES IN i TO 5 DAYS i 2 3 4 5 Lick Observatory Magalia, Cal Mono Ranch, Cal 4209 2320 3210 2750 4975 3216 5350 2250 5280 600 427 32.28 83-12 zoo. 14 ioo| 9it 44 1 6 9 f 37-22 33-33 3-52 Dec., 1884 Jan., 1911 Jan., 1906 Mar. 1906 Dec., 1913 Dec., 1913 Dec., 1910 Jan., 1916 Jan., 1916 Jan., 1916 Jan., 1911 July, 1914 10.86 11.50 10.40 10.35 10.00 11.24 12.95 16.81 6.15 3-75 9-05 *9.IQ 14-75 !3- 2 3 13.60 17.24 15-99 22.64 9-95 15-47 14-23 14-25 20. 76 18.79 25.66 13-30 22. 6l 20. l6 26.87 16.15 23.12 20. 27 27.32 16.31 Helen Mine, Cal Inskip, Cal . West Branch, Cal Nellie, Cal Rialto, Cal Squirrel Inn, Cal Los Gatos Cal Needles, Cal * Precipitation probably occurred in two or more days, f Average annual rainfall approximate. Station Aver- age An- nual Date INCHES OF RAINFALL IN i day 2 days 3 days^ days 5 days Monterey, Mexico 25.0 Aug., 1913 June, 1886 July, 1916 Jan., 1913 Nov., 1909 Aug., 1865 Aug., 1866 June, 1876 Sept., 1879 Oct., 1846 June, 1886 May, 1835 Aug., 1899 Oct., 1893 Feb., 1893 Oct., 1844 May, 1889 ii -3 21.4 22. 2 20.6 15-8 17.6 18.8 48 21.6 II4-5 Alexandria, La. Alapass N C 8.0 40.* Montell, Texas Jamaica. . Hyderbad, India .... 10. 2 20.0 40.8 35-o 20.6 16.0 12.0 18.0 35-5 29.4 30-7 20.4 8-3 12.7 10.6 i5-o 31-8 21.8 35-o 8.8 34-0 r 5-4 36.0 Dorbajee, India Cherrapanji, India Purneah. N. Bengal. 50.00 50.8 33-i 46.0 30.0 61.6 72.3 88.1 Madras, India Bombay, India. Calcutta, India Himalaya Foothills, India. . . . Tabana, Japan. Sama, Japan . . ! Crohamhurst, Queensland Port Jackson, N. S. W Sidney, N. S. W Windsor, N. S W Newcastle, N. S. W Delanason, Figi I. Mar., 1871 Mar., 1871 Dec., 1897 May, 1881 July, 1911 Apr., 1883 Neydunkeni, Ceylon Hongkong, China Baguio, P. I Rio Janeiro, Brazil * Average annual rainfall approximate. SPILLWAY PROVISIONS TABLE XXXIV. EXCESSIVE RAINFALLS. Continued. 357 [Station Aver- age An- nual Date INCHES IN i TO 5 DAYS i 7-8 13-7 14-7 8.8 12.4 7-3 5-6 10.5 6.2 10.6 6.9 i?-S 5-4 2 . 05 ir n. in 3 in. in in. in in. in 3 in. in in. in 2 3 4 s San Francisco, Cal Philadelphia, Pa.. Dec. 19, 1866 Sept. 22, 1882 9-57 7.8 in 3 in. i. in i hours i houi 14 hoi 5 houj 30 m c year. . in 4 in 2 h< hour. irs. s. nutes lours Durs. Mayport Fla Jewell, Md Greytown, Nic July 27, 1897 Dec. 5, 1892 T\ov. 4, 1899 Nov. 17, 1906 Dec. 3, 1906 Dec. 3, 1906 Dec. 3, 1906 Sept. 3, 1900 1901 Oct. 13, 1901 Aug. 3, 1898 Aug. 22, 1899, Aug., 1843, 1 6 i Aug., 1906, 9.3 June, 1871, 3.9 May, 1868, 1.5 Feb. n, 1894, , 700 Grey town, Nic La Boca, C. Z. . Culebra, C. Z Gatun, C. Z Empire, C. Z Santiago, Cuba Matanzas, Cuba. Guantanamo, Cuba Philadelphia, Pa Boston, Mass Concord, Penn. Guinea, Va Galveston, Texas Ft McPherson Neb Sydney, N. S. W Himalaya Foothills, India. mostly of recent origin and the points of measurement are still comparatively few, and it has frequently happened that the really destructive floods have destroyed the facilities for mea- surement, and the extremely rare opportunities for measuring great floods are thereby sometimes lost. On the other hand, rainfall measurements are far more widely distributed, have been continued for a much longer period, and in general may be regarded as more reliable than flood measurements of streams, on account of their greater simplicity. For these reasons we are often compelled to rely more upon rainfall records than upon measurements of runoff for estimating the magnitude of floods for which we must provide spillway capacity. A study of the longest available rainfall records shows that it is possible here and there to select consecutive periods of a 358 STORAGE RESERVOIRS half century or so which contain no excessive precipitation approaching that shown by other parts of the same record. It is seldom, however, that a period is found in which the maxi- mum of 1000 years exceeds very much that shown by any period of 100 or 200 years. Professor Kuichling has compiled and published a list of high discharges from which the most extreme floods have been selected and condensed into a table along with other data, which are given in the last chapter of this book. 7. Outlet Works. One of the most vulnerable features of an earthen dam is the provision for drawing water from the reservoir through or past the dam. The danger consists in the fact that unless elaborate precautions are taken, the conduit presents a convenient path for the percolation of water, which may carry earth with it, and gradually enlarge the opening until a breach is made and the dam destroyed. The outlet conduit is generally of concrete although cast-iron pipe is sometimes used for small reservoirs. In a few cases wooden conduits have been provided, but this is bad practice, as any decay at once opens passage for leakage. It is best to locate the conduit in an open trench cut in rock, hardpan or clay, and to build the concrete directly against the sides and bottom of the trench, which will thus form a good bond between the artificial work and the natural ground. The trench above the conduit should be filled with selected material carefully puddled and rammed in place. The conduit should be provided with wide collars or diaphragms of concrete, extending entirely around the circumference, and these should also be built against the natural material in place as far as possible. The collars may be of any convenient thickness, as i or 2 feet, and should extend into the foundation and the fill at least 3 feet beyond the outer lines of the conduit proper. The masonry in contact with the natural and filled material should be rough and corrugated and every precaution taken to form a tight bond between them, as this is one of the most difficult as well as the most important problems in connection with earth dam con- struction. OUTLET WORKS 359 The valves controlling the admission of water to the conduit should be placed at the upper end, at or near the upstream toe of the embankment, and some means should be provided by which access may be had to the valves at any time that they might need attention. This position of the valves, if ordinary valves are used, requires a tower built over them at a distance from the crest of the dam, which must be reached by means of a bridge. The bridge could be avoided and the tower much cheapened by placing the valves near the axis of the dam, but this is objection- able, as it would admit water to half the conduit under pressure of the full head in the reservoir, and any leaks would introduce water into the heart of the dam, and might in time cause satura- tion and softening of the interior of the dam and give rise to danger that might otherwise be avoided. The controlling valves may be of the balanced type controlled by water pressure as described on p. 365. The pipe controlling the leakage which governs the position of the valve may be led through the conduit or up the slope of the dam, and thus avoid building a tower in the reservoir for control purposes. Such a control is in successful use on the Owl Creek Dam in South Dakota. Slide valves may be installed on the upper end of the conduit at the toe of the dam, placed in the plane of the water slope of the dam, sliding in grooves and attached to gate stems following up the slope to the top of the dam, where they are controlled by gate stands on top of the dam. This type of control does not always give satisfaction. The stem following the slope of the dam is long and requires a number of supports to hold it in line. These are placed on the earth fill and are subject to unequal settlement, and unless protected, to the attacks of ice, of drift and of waves. It is not surprising that they often get out of line and become difficult to operate. A successful valve of this type is in use on the Conconully reservoir of the Okanogan project in Washington, which is closed by an earth dam 83 feet high. The outlet is a circular conduit of reinforced concrete 4 feet 6 inches inside diameter. This is controlled by a cast-iron valve gate 3 feet 6 inches in diameter, 360 STORAGE RESERVOIRS placed in a gate-well 7 feet square for access, and operated from a gate house 62 feet above by a steel shaft and geared wheel. This shaft is supported in an inclined tunnel 5 feet 10 inches in section and 103 feet in length, the reinforced concrete walls of which are from 15 to 24 inches in thickness (Fig. 168). X Steel Rote 2'c.toc. SECTION E- FIG. 1 68. Gate House, Conconully Dam, Wash. If the Ensign type of balanced valve be used, see Fig. 172, the control pipe may pass through the conduit, and thus be thoroughly protected, and does not require any special alinement. The balanced valve moving with little friction is less likely to get out of order or require attention than ordinary slide valves. A simple outlet gate (Fig. 169), designed by Mr. J. D. Schuyler to be built on the face of Fay reservoir dam, is adapted OUTLET WORKS 361 SECTIONAL. BOTTOM PLAN. ENLARGED SECTION OF FRAME AND BOLIING.EAR. FIG. 169. Vertical Lift Outlet Gate, Fay Lake Reservoir, Arizona. 362 STORAGE RESERVOIRS to closing an outlet of either circular or rectangular form. The gate is hung on its center by one heavy lug, over which the stem is placed, expanded to the form of a flat eye-bolt, having sufficient play to enable the gate to accommodate itself to its seat freely, to which it is forced by inclined planes on six lugs and guides. The frame of the hoisting apparatus rests on top of the masonry, to which it is anchored, and the nut and beveled gear are of hard brass. Ball bearings are fitted under the nut, and a light capstan wheel takes the place of the ordinary crank, rendering the gate easily handled under the maximum head of 25 feet. A. B. FIG. 170. Valve-plugs, A, Sweetwater, and B, Hemet Dams. Two other very simple devices designed by the same engineer are illustrated in Fig. 170. Each of these consists of a simple cast-iron plug let into the top of the pipe, the end of which is bent upward to receive it. The plug is held in position by the pressure of water, and is opened by a chain operated from above by a windlass. Butterfly and Needle Valves. One of the safest and most satisfactory forms of outlet for delivering water through an earthen dam is that in use at the Minitare Dam of the U. S. Reclamation Service, in North Platte Valley, Nebraska. It consists of a concrete tube with arched top and invert, built in cut averaging somewhat less than the height of the tube, or about 8 feet, with cut-off collars at frequent intervals on the outside to check percolation along the tube. Inside this tube OUTLET WORKS 363 u 1 ri *-^" -j Ele Elc K ?'o" > ^.4070 b^:;v . 10(10 ' r 4 ll^llli \ I "" --7-0\x< -.9 V280 -' AXIS' OF VALVE AND OUTLET 'TUBE\ , ^^' FIG. 171. Outlet Works, Lahontan Dam, Carson River, Nevada. 364 STORAGE RESERVOIRS are laid side by side two heavy steel pipes, each 30 inches in diameter, with their upper ends projecting through a heavy concrete bulkhead into the reservoir. Just back of this bulk- head each pipe is equipped with a butterfly valve, which being approximately balanced, is easily operated under full head, and is use'd as an emergency valve. Its operating chamber is an enlargement of the concrete tube. The service valves are installed at the downstream ends of the pipes, and are of the needle valve type, similar in design to that shown on P . 3 68. The tunnel is drained at the lower end, and room is afforded for careful inspection of the pipes throughout. In this arrangement there is no opportunity for water to escape by leakage into the interior of the dam, any leakage of pipes being led away by the drainage of the tunnel, and being also accessible for repair. Although the butterfly valves cannot be made entirely tight under high heads, they can be made nearly so if carefully installed, and being simple and seldom operated are not likely to get out of order. By closing one of them, the needle valve on the lower end of the same pipe may be taken apart and repaired at any time, even while the other needle valve is dis- charging water. No gate tower in the reservoir is necessary with its menace from ice and waves. Altogether this is regarded as the most satisfactory regulating system connected with an earthen dam yet tried. Balanced Piston Valve. A type of valve used on several of the reservoirs of the Reclamation Service, Fig. 17 2, has shown especial suitability for use where it is necessary to draw large quantities of water under high heads. It utilizes the enormous water pressures to open and close the valve. It consists of a steel cylinder closed at the outer or downstream end, in which slides a piston, the inner, end of which forms a needle, operating to regulate the amount of water discharged and closing like a check valve. The piston may be removed by removing the cylinder head. It is kept in alinement with the axis of the cylinder by bronze guides. OUTLET WORKS 365 366 STORAGE RESERVOIRS FIG. 173. Outlet Conduit, Keechelur Dam, Washington, Showing Concrete Cut-off Collars, Corewall and Track for Backfilling on Left. FIG. 174. Butterfly Valve, Minitare Dam, Nebraska. OUTLET WORKS 367 It is opened and closed by the regulation of the pressure of water behind the main piston, the pressure being supplied by the restricted leak past the piston, and relieved by a drain or control pipe leading out from the cylinder head. To open the valve the pressure on the piston is reduced by opening the outlet of the SELL DOWNSTREAM ELEVATION VERTICAL SECTION ON C.'L, FIG. 175. Elevation and Section of Butterfly Valve. control pipe. As long as this discharges freely the valve will continue to move until completely open, and it may be stopped at any point partially open by properly regulating the leakage through the control pipe. To close the valve, the outlet from the control pipe is closed and pressure applied from a tank far above the reservoir to start the piston, after which ,it will slowly 368 STORAGE RESERVOIRS close itself, the rate of movement depending on the volume of leakage around the piston. 19 FIG. 176. Needle Valve in Outlet Conduit, Minitare Dam, North Platte Valley, Nebraska. In order to give positive and accurate regulation of discharge from the reservoir a positive control is also provided as shown OUTLET WORKS 369 in the drawing. The leakage is regulated by a movable sleeve fitting over a conical seat which stops the leakage when closed and when opened permits the escape of water, thus removing the pressure from that side of the piston, causing the valve to open. The valve thus follows the sleeve, maintaining just enough area between the sleeve and the conical seat to regulate the leakage to the quantity required for balance. The sleeve being movable at will, by means of a hand-wheel, rod and screw, the position of the valve can be accurately controlled. An indicator is provided to show the position of the valve at any time. CHAPTER XVI SEDIMENTATION OF RESERVOIRS ALL natural streams erode their channels to some extent, and carry more or less silt in suspension and roll along their bot- toms sand and gravel. Where a dam is built across the stream and the water impounded, the sediment settles, and may in time seriously impair the reservoir capacity if not removed. In high mountainous regions where the slopes are protected from erosion by forests, and where the water comes chiefly from springs or melting snows, the streams are usually clear and very little sediment is carried. On such streams the silt problem is generally considered negligible or so far in the future as to be met by constructing new reservoirs when needed. Lower down the same stream may accumulate more sediment, and this problem may assume considerable importance. In other regions less protected by vegetation and subject to torrential rains, as in the southwestern part of the United States, the streams carry enormous quantities of solid matter, and it becomes a serious question whether any given storage project is feasible in view of the rapidity with which the capacity will be destroyed by filling with detritus. The Colorado and the Rio Grande are typical streams of this class. Where it is feasible to locate the reservoir off the stream, and conduct the water to it through a feed canal, it may be possible to discard most of the coarse material by means of settling basins and scouring sluices, but these require much attention, waste much water and are not very effective in eliminating the finer silt. The problem involved by the sedimentation of reservoirs constructed on silt-bearing streams is one which has received 370 SEDIMENTATION OF RESERVOIRS 371 much study, and various theories have been advanced for its solution, but none of them have been proved out in practice. Several efforts have been made to determine a reliable factor to express the relation between the dry weight of silt obtained by observation, and the volume of the same silt as it would lie in the bottom of a reservoir, the question being, " What is the dry weight of a cubic foot of silt deposited in a large reservoir by sedimentation of the flood waters of the stream?" The following table shows the results of the four most reliable of these attempts: TABLE XXXV Observer Weight of Cubic Foot of Wet Deposited Silt Dry Weight Specific Gravity Follett C-2 O Coghlan. I O4. 7 Q2 7 2 64 Hughes 80 ^ 76 I 2 << Lavvon 86 o 2 60 Averaging the above results, we have 77 pounds as the average dry weight of a cubic foot of silt deposited in a reservoir. This however, can be taken as only a very rough guide, as would be inferred from the wide discrepancy in the results quoted. The variation is doubtless due in part to actual difference in character and weight of the different samples of silt tested. It is probable that a more important reason is the difference in judgment of the different observers as to what constitutes a sample of silt representative of conditions in the bottom of a large reservoir, under the pressure of overlying mud and water. Such conditions will vary widely, and we cannot hope to obtain any results that would serve as more than a rough guide for future estimates. Systematic observations of silt carried in suspension by the waters of the Rio Grande have been made by the United States Government, from 1897 to the present time. These observations up to and including 1912 were carefully studied by W. W. Follett and the results obtained are summarized in the following table: 372 SEDIMENTATION OF RESERVOIRS TABLE XXXVI. SILT IX RIO GRAXDE PASSING SAN MARCIAL, N. M. Year Acre-feet Water Per Cent Silt Acre-feet Silt 1897 2,215,953 1.72 38,051 1898 960,981 1-55 14,858 1899 239,434 2.14 5,127 1900 467,703 2.02 9,459 1901 656,252 2.82 18,503 1902 200,729 3-05 6,123 1903 1,272,069 0-97 12,319 1904 700,796 2-37 16,838 1905 2,422,008 0.78 18,875 1906 1,563,737 0.89 13,901 1907 2,157,709 I . II 23,889 1908 774,109 2.00 15,469 1909 1,279,934 I-5I 19,318 1910 852,692 o. 76 6,520 1911 1,799,733 4.14 74,563 1912 1,499,614 1-47 22,018 Total 19,072,453 315,832 Mean 1,192,028 1.66 19,739 These silt determinations were made by taking samples of the muddy water as found flowing in the river, and removing the silt by settlement and filtration, drying at 60 C. and weighing it. The percentages are by volume, and are based upon a dry weight of 53 pounds for a cubic foot of wet sediment in place in the reservoir. This factor of 53 was found by taking the dry weight of a 3 -inch cube of wet silt from a slough where a body of flood water had stood until the sediment settled, the water evaporated, and the silt began to shrink from the drying process. These observations show that if a reservoir of 300,000 acre- feet capacity had been constructed in 1897, it would have been practically filled with sediment several years ago, unless this had been somehow removed. They show, further, that any reservoir constructed on this stream would, unless prevented, have its capacity seriously impaired in a time so short as to present a problem of importance. This must be solved before SEDIMENT ROLLED ALONG THE BOTTOM 373 deciding upon the construction of an expensive storage project, where thousands of homes are to be established through its agency which will be destroyed if it fails of its purpose. The measurement of sediment in the Colorado, Gila and Pecos Rivers reveal similar problems concerning storage projects thereon, and the same may be said in some degree of many other streams in this and other countries. A study of scattered observations of silt carried by the Gila River made by D. E. Hughes,* leads him to the conclusion that its water carries an average of 1.3 per cent of its volume of solid matter. Various reservoirs in Europe, Asia and America have had their capacity largely destroyed by the accumulation of mud and sand. From a consideration of all available results of experiment in India and America, Etcheverry concludes that: 1. One cubic foot of saturated silt settled in a tube for one year, contains about 30 pounds of dry silt. The per cent by volume, of saturated silt is equal to the per cent by weight multiplied by 2.1. 2. One cubic foot of moist silt, as deposited under natural conditions in a river or canal or on a field, will contain about 50 pounds of dry silt. For this condition the per cent by volume of moist silt is equal to the per cent by weight multiplied by 1.2. 3. One cubic foot of dried silt will weigh about 90 pounds. The above results cannot be considered accurate for any particular silt sample, nor for any particular stream, as individual cases vary widely. It is, however, about as good a statement of averages as present knowledge will afford. 2. Sediment Rolled along the Bottom. In addition to the sediment which is held in suspension and carried by the current of the stream there may be larger and heavier particles of sand which are too heavy to be held in suspension but which under the influence of flowing water gradually move downstream along the bottom. This frequently happens in streams of per- fectly clear water, and careful observations of such streams will * House Doc. 791, 6$d Congress, 2d Session. 374 SEDIMENTATION OF RESERVOIRS show the sand in small knolls or dunes on the bottom of the stream. The grains of sand on the surface -gradually move down the stream. The small sand bars are usually very gentle in slope on the upstream side and steep on the downstream side. The moving grains of sand are carried slowly up the slope of the little bar or dune and reaching the summit are dropped on the downstream side, forming on that side a slope usually about 45 degrees near the top, flattening slowly toward the bottom, while the slope on the upstream side may be 5 or 6 to i. Where the major portion of the solid matter carried by the stream is in the form of sand this material moving on the bottom becomes an important element in measuring total solids. Where the eroded material is mainly clay the amount of sediment on the bottom may be insignificant. The quantity of all material carried can, of course, be accurately measured by impounding it, but aside from this method little effort has been made to measure this in flowing streams. The only attempt of this kind on any large scale was that made by the Nicaragua Canal Commission in 1898 upon the streams in Nicaragua in connection with the investigation of an inter-oceanic canal. The method devised was as follows: A galvanized sheet-iron pan was provided (see Fig. 177), i meter square and 8 inches deep, with one side hinged so that it could be opened to lie in the same plane as the bottom of the pan, and a weight and stays were provided to hold it in this horizontal position. Four chains, attached one to each corner of the top of the pan, met about 4 feet above the pan, and united in a ring, and the whole was suspended from a cable stretched across the river, with the door open upstream. An anchor was thrown about 100 feet upstream to hold the pan firmly in position, while it was gently lowered from the cable by means of a rope from shore, working in tackle blocks. The pan was allowed to settle firmly on the bottom, and to remain for a limited time, usually one hour. The attempt is to cause the minimum disturbance of natural conditions in the stream, and to intercept and hold in the pan the sediment traveling along SEDIMENT ROLLED ALONG THE BOTTOM 375 the bottom in the section it occupies. When it is desired to close the observation, a small copper wire which has been fas- tened to the open door and passed through the ring above the pan, is stoutly pulled until it raises the lid from the bottom of the stream, whereupon the current catches and slams the lid shut, where it is automatically fastened by a latch on each side. Then, by means of a windlass on shore, the pan is hoisted and brought to land, and the entrapped sediment measured. There is nothing about this operation to increase the motion of sediment along the bottom into the pan, so it is thought that FIG. 177. Trap for Measuring Sand Rolling on Bottom of Stream. results can never be too large. On the other hand some sand may pass under the edge of the lid, when the bottom of the river at this point is marred with local inequalities. This is supposed to be one cause of the small results on certain days, when other observations immediately before or after, give large results. Another persistent source of error of unknown magnitude is the washing out of the sediment by the current over the weir formed by the back of the pan. To test the importance of this theoretical possibility, a temporary partition was placed in the pan, perpendicular to the current, and nearly as high as the 376 SEDIMENTATION OF RESERVOIRS sides of the pan, the theory being that if all sediment were stopped by the partition and deposited in front of it, that would be good evidence that in the absence of the partition all would be stopped by the back of the pan, and none lost. In the first experiment more sediment was deposited behind than in front of the partition, and the quantity that passed out of the pan is unknown. This result was essentially repeated for most of the experiments, showing conclusively that more or less sediment is carried out over the back of the pan by the scour which it occasions. It is important to bear this fact in mind, when studying the results, for it is certain that the results are quantitatively too small, and should be regarded as showing that large quantities of sediment are traveling on the bed of the stream, and as roughly indicating the relative amount. 3. Removal of Silt from Reservoirs. The great Assuan Dam in Egypt, forms a reservoir on the Nile, which has a very large discharge and carries great volumes of silt. The large capacity of the reservoir is formed mainly by the very slight slope of the river, so that the dam causes slack water for a distance of over 40 miles up the river, making a long narrow reservoir, with no very wide valley submerged. The dam is provided with 180 large sluices, and during the rising flood each year, when the river is carrying most sediment, the sluices are left open, and the rushing torrent carries its load through the reservoir and also scours out a portion of the sediment deposited the previous year. As the flood declines in volume it carries less sediment, and the sluice gates are then closed and the waters stored. The sediment deposited during the storage period is largely washed out by the first part of the next year's flood. This program seems to be effective in preserving sufficient storage capacity for present needs of irrigation, but it requires the waste of the major portion of the water supply in normal years, and also depends upon the extremely long narrow reser- voir, in which a swiftly flowing stream is very effective in cut- ting out the deposited sediment. The variations of flow of the Nile are, moreover, so regular that a predetermined program is possible, which would be utterly impossible upon many streams. REMOVAL OF SILT FROM RESERVOIRS 377 This combination of conditions is so rare that the solution adopted has little application to most cases, and presents no general solution for the problem in hand. According to Table XXXVI, waters of the Rio Grande during the 16 years carried if per cent of their volume of sediment on an average. The detailed observations from which this summary was compiled show several monthly averages in excess of 10 per cent, and in general the percentage fluctuated widely, but the heaviest percentages are found in the four months of July, August, September and October, and especially August and September. These are the months when the sudden torrential rains occur, and this accounts for the large percentage of sediment in those months; but a greater portion of the water is discharged in April, May and June, while the snows in the mountains are melting, and though the percentage of sediment is less in those months, the total quantity is often greater, due to the greater quantity of water flowing. The flow in the late summer is very unreliable, and it is necessary to meet irriga- tion needs by storage to be drawn upon at that time, and it is therefore impracticable to apply the methods in use on the Nile, of allowing the muddiest water to flow through the sluice gates unchecked by the reservoir. That method is also impracticable for the further reason that usually all the water is needed for irrigation, and must be stored for that use. The figures show an accumulation of sediment so rapid that unless we can provide some means of disposing of it and of preserving the storage capacity, it would be unwise to construct the reservoir and build the homes that must depend upon it, as without reliable storage they must be abandoned. The method proposed as feasible for solving this problem on the Rio Grande is applicable to many other streams, and a description of it may therefore be of value here. It is recognized that to excavate the mud from the reservoir and transport it to locations outside of the reservoir by ordinary mechanical methods would be very expensive, and at present values prohibitive. Even if it could be accomplished at a price of 5 cents per cubic yard, that would amount to about $80 per acre-foot, whereas 378 SEDIMENTATION OF RESERVOIRS the cost of constructing the reservoir was about $2 per acre- foot, and an enlargement of 50 per cent can probably be acccom- plished at about the same rate. Therefore, as a first step in the solution of the silt problem it was decided to construct a reservoir of nearly twice the capac- ity absolutely needed to control the flow of the river, so that the accumulations of sediment will not seriously encroach upon the necessary storage capacity for a period of perhaps 40 to 50 years. At that time the works will have been long paid for, and the development of the valley will be such that an enlarge- ment can easily be made which will furnish storage capacity sufficient for another period of 40 or 50 years. The reservoir thus formed will be over 50 miles long, and will not be very wide at any point. On the headwaters of the stream and its tributaries are several smaller reservoir sites, capable of development to the amount of several hundred thousand acre-feet at moderate cost, which are fed by melting snows and will fill with water carrying very little sediment. Whenever the reservoir at Elephant Butte is so far filled with mud that additional storage is needed, one or more of the mountain reservoirs can be built, and the necessary storage capacity thus provided. In the management of the storage works it would be the policy to hold the mountain reservoir full of water as long as possible, and draw on the lower reservoir for needed water as long as any water remains there to be drawn. When the lower reservoir becomes empty, the natural flow of the river, reinforced if required, by water from the upper reservoir, would flow through the sea of mud accumulated in the lower reservoir, and cut a channel therein, carrying the mud thus eroded out of the reservoir through the open gates as the water is needed for irrigation. Such a channel extending 50 miles through the axis of the reservoir varying in depth from 240 feet at the dam to zero at the head of the reservoir, and having a bottom width of 250 feet, and side slopes of 3 to i would itself have a volume of over 500,000 acre-feet. All the water flowing through the reservoir, both natural flow and stored, would carry from 10 REMOVAL OF SILT FROM RESERVOIRS 379 to 15 per cent of its volume of mud until such a channel was cut, and nearly as much for a long time after, by cutting the banks of the channel, and because of their natural tendency to slide and to slough. In this way, an equilibrium could be established, by which the amount of sediment flowing in annually would be offset by the average amount annually discharged as above. Just how much mountain storage would be necessary to accomplish this could be established only by experience, but until such equilibrium is established the needs of storage would be supplied by building reservoirs, which is cheaper than mechanical removal of silt, provided good reservoir sites exist, as they do in the basin of the Rio Grande. It will be seen that the application of such a remedy depends upon the topographic and hydrographic characteristics of the drainage basin, including the shape of the reservoir, a long narrow and deep reservoir being most favorable. These con- ditions would not be found in every case, and each problem would require special consideration. A method of handling the silt in the Elephant Butte Reservoir proposed by W. W. Follett, is as follows: About halfway between the dam and the head of the reservoir, in a gorge that occurs at that point, it was proposed to build a dam 40 or 50 feet high, forming a small reservoir within the main large reservoir. On this dam provide a gate tower, extend- ing above the flow line of the reservoir. The gates controlled from this tower were to open into a conduit through this small dam, which would pass on down the valley as a large pipe, to and through the main reservoir dam. This conduit was to be used to draw water from the reservoir whenever possible. During low stages of the main reservoir the small reservoir formed by the small dam would receive the water of the river, and much of the sediment would be deposited therein before the water passed over its spillway into the main reservoir below. At such times as the small reservoir was low, the turbid natural flow of the river would pass through the conduit, cutting out any silt deposited in the small reservoir, carry its load of fertile 380 SEDIMENTATION OF RESERVOIRS sediment to the irrigated lands, and any additional water required would be drawn from the main reservoir. This provision would surely have provided muddy water for irrigation much of the time, instead of the clear water now uniformly furnished, and while this would not have prevented the encroachment of sedimentation upon the storage room, it would have retarded it. Its greatest recommendation, however, is that it would have 'preserved the fertilizing qualities of the irrigation water and thereby increased the fertility of the lands. This plan was carefully considered by a board of engineers and rejected mainly on account of its cost. REFERENCES FOR CHAPTERS XV AND XVI STRANGE, W. L. Indian Storage Reservoirs. Spon & Chamberlain, New York. Report of Special Committee on Flood Prevention. Trans. Am. Soc. C. E.. vol. 81, p. 1218. DAVIS, ARTHUR P. Irrigation Works Constructed by the United States. John Wiley & Sons, New York. SCHUYLER, J. D. Reservoirs for Irrigation, Water Power and Domestic Water Supply. John Wiley & Sons, New York. FLINX, A. D. Rainfall, Runoff and Development of Croton Watershed. Engi- neering News, Feb. 6, 1908. DAVIS, ARTHUR P. Water Storage on Salt River. W. S. P. 73, U. S. Geological Survey. LIPPINCOTT, J. B. Water Storage on Gila River. W. S. P. 33, U. S. Geological Survey. FOLLETT, W. W. Silt in Rio Grande. Engineering News, Jan. 15, 1914. HUGHES, D. E. San Carlos Irrigation Project. House Doc. 791, 63d Congress, 2d Session. Davis, Arthur P., Report on Hydrography of Nicaragua, 1899. CHAPTER XVII DAMS A DAM is a structure placed across a stream or gap to obstruct or confine water. When designed to permit water to flow over the top, it is called a weir. In such a case it must be built of such material as will resist a tendency to wash away by the flow of water. This may be either masonry, steel, or some form of wood. i. Conditions of Safety. All dams, of whatever magnitude or type, must fulfill certain essential conditions for safety. 1. They must have practically impervious foundations and abutments sufficiently stable to sustain the stresses to which they will be submitted. 2. They must be safe against sliding either on foundation or on any internal joint. 3. They must be safe against overturning. 4. They must be practically impervious, and have water- tight connections with their foundations and abutments. With respect to their functions, dams may be divided into two classes: 1. Diverson dams. 2. Storage dams. A diversion dam is one intended only for raising the surface of the water to such height as required for diverting the flow of the stream into a canal or penstock, for power, irrigation or other purposes. The great majority of them are very low, raising the water only a few feet, and intended mainly to pro- vide a permanent sill or crest at the proper elevation instead of a shifting, fluctuating channel. Some diversion dams, how- ever, are as high as 200 feet, and these are often used also partially for storage purposes. 381 382 DAMS Storage dams are those intended to form reservoirs to store water at times when it is flowing at greater volume than needed for use, and to hold it until so required. Most of the high dams in existence are intended for storage purposes, and in general they are built higher than those intended only for diversion. 2. Diversion Dams or Weirs. Most dams intended only for diversion purposes are of the weir or overfall type, designed to permit water to flow over the top, on account of the expense of providing safe means of flow elsewhere for the floods. For such use they are generally built of wood or concrete so as to resist the erosion of the flowing water. a. Timber Dams. The earliest dams were built by beavers, and were composed of small logs and brush. These have been improved upon by man, by adding large rocks and rude piling to hold the brush in place. Such rude dams were general in the early stages of irrigation, and were employed even in fairly large streams, not to raise the water, but to divert it into a canal built at about the same elevation as the river bed. Such dams were often breached and sometimes entirely destroyed by floods in the stream, thus depriving the canal of water after the subsidence of the flood until it could be replaced, to be again destroyed perhaps after a short time. One of the earliest types of such structures was the so-called " burro " dam. This consisted of a series of forked stakes driven into the sand of the river bed at intervals of 6 or 8 feet across the stream, inclined slightly upstream. These stakes were as large as could be driven firmly by hand, and poles were placed in the crotches of the stakes, and lashed firmly to them, thus forming a one-pole fence across the river, 3 or 4 feet high. Brush was leaned against this fence from the upstream side, lashed to the fence, and rock piled upon the brush ends where they lay upon the river bed ; earth was dumped on the rock to make it tight. Larger rock was sometimes placed as a pavement on the downstream side of this rude dam, to resist the erosion of the falling water. Improvements on this form of dam by the use of heavier piling driven by machinery and the use of larger rock constituted DIVERSION DAMS OR WEIRS 383 384 DAMS the essential features of most of these temporary structures which were cheap, but very precarious. They could be built only when the river was low, and often caused partial or total loss of crops by going out when most needed. When sub- jected to alternate wet and dry conditions, wood decays rapidly. When a timber dam is built in a stream which is subject to great fluctuations of head and perhaps dry at times, the wood tends to decay, and it is good practice to combine timber and concrete construction in such cases. The foundation, apron and other parts which will be perpetually wet may be built of wood, and be considered permanent, while those parts which may be dry at times, the superstructure and abutments, are built of concrete. A form of low timber diversion dam sometimes built con- sists of a plank platform held in place by a series of piling driven into the river bed. On this foundation timber frames are erected at close intervals in the form of the letter A. These are firmly bolted to the foundation, and the upstream legs of the frames closed with heavy planking. The water is allowed to flow over the top of this diaphragm and fall upon the plant platform below, which is placed a little below the natural river bed, and is perpetually submerged. Such dams have been used successfully in many cases. b. 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 centers. Between these is driven sheet piling to prevent the seepage 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 structures cannot be employed where the flood height is great, as they would soon be undermined unless substantial aprons were constructed. DIVERSION DAMS OR WEIRS 385 egulator CROSS SECTION OF WEIR. FIG. 179. Folsom Canal Plan and Cross-section of Weir. 386 DAMS c. Open and Closed Weirs. 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, 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, and the scour pro- duced by opening the gates prevents the deposit of silt. 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 downstream. 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. 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 or lower, and is protected from erosive action by curtain-walls up- and downstream. The I /Cx J^ CALIFORNIA Colorado liii-( SCALE OF FEET 200 400 GOO 150 Feef Concrete'; jj ' - 6"Wood Sheet Piling-^pj i Concrete -67'6- 1'il MAXIMUM FIG. i So. Plan and Sect 3000 3500 ORINGS ON LINE A 5000 141.0 Kiev. Low Water 1004 'ION ON C-D Laguna Dam, Colorado River. To face page 386. DIVERSION DAMS OR WEIRS 387 pieis are grooved for the recep- tion of flashboards or gates so that by raising or lowering these the height of the river can be controlled. The distance between the piers varies be- tween 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 auto- matically when the water rises to a sufficient height to top them. It is sometimes neces- sary 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, in order that in time of flood the height of water may not be appreci- ably increased above the fixed diversion height. Should the height be increased in such cases the water would back up, flooding and destroying valuable property in the cities above. Under such circumstances open weirs are sometimes so con- structed that they can be entirely removed, piers and all, leaving absolutely no obstruc- tion to the channel of the stream, and in fact increasing 388 DAMS its discharging capacity, owing to the smoothness which they give to its bed and banks. d. 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 structure 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 founda- tion 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. A more common type of frame or flashboard weir is that employed on the Kern River in California. (Fig. 182.) An example of this is the weir at the head of the Galloway canal (Fig. 183), 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, forming compartments filled with sand on which the waters fall. This apron is carried up- and downstream 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 two pieces, the upstream piece being 1 5 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 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 trans- versely the entire width of the stream. On the upstream face of the trusses planks or flashboards which slide between grooves formed by nailing face-boards on the trusses are laid on to the DIVERSION DAMS OR WEIRS 389 390 DAMS required height. This weir is 10 feet in height above the wooden floor, which is flush with the river bed. e. Indian Type Weirs. A substantial form of 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 foundations of masonry, in such manner that they practically float on the sandy beds of the streams. FIG. 183. Cross-section of Open Weir. Galloway Canal. 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 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, depending partly for its stability on the friction against its sides. This form of construction is illustrated in Fig. 184. DIVERSION DAMS OR WEIRS 391 NARORA WEIR- LOWER GANGES CANAL length 7260 metres OKHLA WEIR -AGRA CANAL., Length 743 metres DEHREE WEJR-SOANE CANAL length 5825 metres ITT. 6EZWARA WEIR - KISTNA CANAL. length 1150 metres. 60DIVERY WEIR, length 6274 metres. FIG. 184. Cross-sections of Indian Weirs. 392 DAMS f. Automatic Shutters and Gates. The use of flashboards or any similar permanent obstruction in a wasteway in order to increase the storage capacity of the reservoir is to be discouraged. Such obstructions must be removed at the time of great floods or else these will top the dam, which depends upon the attention of watchmen, who may be absent or negligent. Automatic shutters, however, have been used with considerable success in a few instances. One of the most desirable forms of these is that shown in Fig. 185. It consists of a row of upright iron shutters, each 1 8 feet long and 22 inches high. These are supported by ten- sion-rods hinged to the crest of the weir on the upstream side, and to the upper side of the shutter at about two-thirds of the distance from its crest, or, in other words, below its center FIG. 185. Cross-section of Shutter on Soane Weir, India. of pressure. As soon as the water-level approaches the top of the shutter it causes its lower end to slide inward and the whole falls flat against the top of the weir, offering no obstruction to the passage of the water. g. Automatic Drop-shutters. The shutters, added in 1901 to the crest of the Betwa weir at Paricha, India, to increase the reservoir capacity may be taken as illustrative of the latest Indian practice in the design of automatic drop-shutters. The shutters are each 6 feet high and 12 feet long, and as the length of the weir crest is 3600 feet there are 300 such shutters. They are made entirely of steel, consisting of }-inch plates joined along their middle and stiffened both longitudinally and laterally by angle-iron 3^ by 2\ by f inch (Fig. 186). To the flanges of the vertical stiff eners are pivoted if -inch tension-bars. The other end is similarly attached to anchor- DIVERSION DAMS OR WEIRS 393 bolts built 2 feet into the masonry crest of the weir. There are four such tension-bars to each 1 2-foot gate. The point of attachment of the tension-bar and shutter is so designed that the gates fall automatically with a given depth of water passing 331.90 P.O. Concrete \ D "Lime Concrete >28.5 5V OLD WEIR RUB. MASONRY. 12V-' \ M.S. Plate / ShoeJ* ELEVATION. nTTllL Jllililllii'v TT / M.S. Plate T' L.I. Stiffene M Plate SECTION ,L.I. Stiffened >L.I. Brace 3^'x 2&\ %" y Shoe M.S. Plate %" BOTTOM PLAN. L.I. Stiffener 3>* x FIG. 1 86. Automatic Drop-shutter, Betwa Weir, India. over them, thus securing safety in case of excessive floods. The bottom of each gate is supplied with four steel shoes, which rest upon sliding-plates built into the weir crest, thus reducing the frictional resistance when the gates fall. Wooden baulks 4 by 4 inches are fixed to the ends of the shutters, which have a 394 DAMS space of i inch separating them, which is caulked when the gates are raised. If the 300 shutters were to fall together the shock would unduly strain the weir and tne flood volume submerge the river- banks below. Hence the attachment of the tension-bars has been so arranged that each third gate falls under different depths of water. The first third fall with a depth over top of 2 feet, the next with 3 feet, and the last with 4 feet. Thus after the first third fall the released water reduces the flood depth, and the latter must increase considerably to top the second third, and so on for the last third. These shutters were subjected to an unusual test, immediately after completion, in the form of an extraordinary flood which passed over the weir crest to the height of 16.4 feet, when it had been designed to withstand a previous known flood height of only 6.5 feet. Fortunately the shutters worked success- fully and neither weir nor shutters sustained material injury. h. French Type. The weirs on the River Seine in France differ materially from the 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 channelway 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 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 passageway of the floods over, around, and through them (Fig. 188). i. Roller Dams. A movable dam invented and patented in Germany, consisting of steel rollers, capable of being rolled up an incline when required to pass floods, has been used in that country and also in a few instances in the United States. DIVERSION DAMS OR WEIRS 395 FIG. 187, Falling Sluice-gate, Soane Canal, India. 396 DAMS The largest one built in this country is on Grand River, about eight miles above Palisade, Colorado. In the diversion of Grand River, the problem presented was to raise the level of the river at low stages sufficiently to divert 1400 cubic feet of water per second into the head of the canal, and yet at high water to pass a flow of 50,000 cubic feet of water per second without raising the water to a level where it would endanger the roadbed of the railroad adjacent. This required a movable crest upon a concrete weir. FIG. 1 88. View of Open Weir on River Seine, France. The dam developed is a concrete base of ogee section with projecting apron, surmounted by a series of seven movable roller dams, six of which are 70 feet long and 10.25 feet high, over the dam proper, while the seventh has a span of 60 feet and a height of 15.3 feet, and is used to control the sluiceway. The total length of the structure is 536.5 feet. When the rollers are closed at low water it raises the water 20 feet above the bed of the river. See Fig. 190. The canal regulator gates are parallel to the river, and nearly on a line with the natural bank, and the sluiceway roller closes upon a sill 5.1 feet below the sills of the other rollers, and 8.3 DIVERSION DAMS OR WEIRS 397 398 DAMS DIVERSION DAMS OR WEIRS 399 feet below the sills of the canal gates, so that gravel will be deposited instead of passing into the canal, and can be sluiced out by raising the 6o-foot roller, and thus a deep settling basin FIG. 191. Section through Body of yo-foot Roller Dam, Grand River, Colorado. can be maintained in front of the gates, to prevent the river gravel from entering the canal. The hoisting apparatus for the sluicing roller is located on the right abutment of the dam, which serves also for the left abutment of the headgate structure. The other six rollers are 400 DAMS operated by three hoists located on alternate piers, each hoist serving two rollers. These piers are 10 feet wide, and the other three are 8.25 feet wide. A steel truss bridge spans each open- ing. Each hoist is equipped with an electric motor receiving current from a gas engine in the gate house on the right abutment . ' (thru, c. of halt circle) ' /^/Filler plate # 6 "jc8*& 354 ''3' Illllllllll FIG. 192. Section through Driven End of 7o-foot Roller. pier. The rollers are lifted by rolling them up the inclined tops of the piers. The advantages of this type of movable dam, are its long span, requiring but few piers to obstruct drift, the ease and speed with which it can be opened, and the tightness of closure, per- mitting little leakage. DIVERSION DAMS OR WEIRS 401 j. Crib Dams. A type of dam much employed in early days, and still frequently built, consists of a series of cribs built of logs firmly bolted or pinned together, and filled with large and small rock to give weight and stability. The cribs are rectangular, from 12 to 1 6 feet square, and longer timbers extend from one crib to the next to bind them firmly together. A floor of heavy timbers is provided near the bottom of each crib for holding the rock. The bottom of each crib should be drift-bolted to the foundation if of rock, and sunk as low as possible into any softer foundation, and sheet piling may be added to stop per- colation under the dam. It is best to give the dam a slope of 45 degrees or flatter on the upstream face, and to cover this with . FIG. 193. Cross-section of Bear River Weir. planking for water tightness. The lower side may be likewise sloped and covered with planks, but it is best to make this slope steep at top, and gradually flatten it toward the bottom to give the falling water gradually a horizontal direction as it leaves the dam. The bottom of the river for some distance below the dam should be protected from erosion by submerged cribs covered with heavy planks or sawn timbers, and filled with the largest available rock. Where a crib dam is of considerable height, the downstream slope is sometimes made in a series of steps to break the fall of the water and dissipate the greater part of its energy before reaching the toe of the dam. 402 DAMS k. Submerged Dams. In desert regions, it frequently happens that small streams emerge from the mountains and are lost in the sands and gravels of the desert before reaching any larger stream, or other outlet. In times of flood the water flows stjfl a much greater distance over the desert than normally, and in so doing forms a water course which is usually dry on the surface or nearly so. Numerous attempts have been made to bring the underflow to the surface by sinking concrete or wooden dams, called submerged dams, in the ground across DIVERSION DAMS OR WEIRS 403 the water course. These have at times collected some water, but the quantity has usually been disappointing. One such structure is the dam on Pacoima Creek in Cali- fornia, the property of the San Fernando Land and Water Company. 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 _^ FlG. 195. View of San Fernando Submerged Dam. trench was excavated across the canyon in which a rubble masonry wall was built, its base being about 3 feet thick and its top 2 feet reaching 2 or 3 feet above the stream bed. On the line of this wall are two large gathering wells, and on its upper 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 irrigation. 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. A somewhat similar submerged dam is in operation at King- man, Ariz., for providing a small supply to the town and railway. 404 'DAMS A masonry wall 173 feet long on top, 6 feet wide at base; and 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 per- forated with f-inch holes placed J inch apart. In this is col- lected the water which gathers behind the dam to the full height of its crest. 3. Storage Dams. Storage dams may be classified into four general groups according to the materials of which they are composed as follows: 1. Earth dams or embankments. 2. Rock-filled dams. 3. Steel dams. 4. Masonry dams. Numerous modifications and combinations of the above types are often employed, as for example, a combination of the earth and rock-fill types, of which this chapter treats. The type of dam to be constructed at any given site is deter- mined chiefly upon consideration of three leading elements which are usually capable of interpretation in terms of cost. 1. Character of available materials for construction. 2. Character of foundation and abutment. 3. Length and height of dam. It often happens that the dam-site is in a rocky canyon, where there is not available within reasonable distance a suffi- cient quantity of material suitable for an earthen dam, and the difficulty of making a tight bond between the rock and an earth embankment, furnishes additional reason for rejecting this type. Where the dam-site is a narrow gorge with good rock founda- tion and abutments so that a masonry dam of light section depending on arch action can be built, this type is usually the cheapest, and commends itself to the general public for its safety and stability if well built. If the gorge is more than 600 feet wide at the top of the pro- posed, dam, so that little advantage can be secured from arch STORAGE DAMS 405 action, the* rock-fill type may be worthy of consideration in comparison with a masonry dam. Where the dam is to be of considerable length, and con- ditions are at ail favorable for an earthen dam, this type is generally cheapest, can be made perfectly safe, and its choice is therefore advisable unless it is to be very high, in which case masonry should also be considered if a foundation of good rock is available. a. Earthen Dams or Embankments. The essential features of a serviceable earthen dam are five : 1. That it is protected by an ample spillway, from the flow of water over any portion. 2. That the water slope or the center, or both, be practically impervious to water. 3. That the foundation and abutments be practically imper- vious, and connected with the dam by a water-tight bond. 4. That the water slope be protected from wave action by paving or riprap. 5. That both slopes be sufficiently flat to insure the class of material used against sloughing. There are three general types of earthen dams, classified with reference to the portion made impervious: 1. Dams having a central core of puddled earth, or a central wall of masonry. 2. Dams having the water face and center built of selected material made nearly impervious, and coarser material used on lower face. 3. Dams built in layers of homogeneous material throughout, which must of course be nearly impervious. It must be remembered that all earthen masses, and most rock and concrete is capable of absorbing and transmitting some water if sufficient pressure be applied, and so when we speak of impervious materials in earthen dams, we speak relatively. b. Foundation. No feature of the site for an earthen dam is more important than the foundation, and this should be examined with great care. If it consists of alluvial material deposited by water, it is likely to contain pervious strata of sand or gravel, 406 DAMS STORAGE DAMS 407 and these if left undisturbed will produce leakage under the dam, which under the head of water in the reservoir might attain destructive velocities and cause disaster. Free percola- tion must be entirely prevented, and all percolation must be made so slow and devious that it will be inert, and without danger of destructive erosion. In general it is necessary to provide a wide cut-off channel or core wall, carried down to rock, or to a thick bed of relatively impervious material, through which such percolation as occurs will be very slow. The best foundation for an earthen dam is a thick bed of impervious clay mixed with a large proportion of sand and gravel thus combining water- tightness with stability. A foundation of fine sand is not permissible unless it contains some clay or impalpable silt. In the case of any foundation which will permit some percolation, there is an advantage in making the path which the water must follow in order to reach a free escape, as long as possible, which may be secured by spreading the base of the dam if this is made of impervious material, thus confining the per- colating waters for a greater distance before they can escape. It was upon this theory that the Gatun Dam on the Canal Zone was given very flat slopes, and a very wide base. If an earthen dam is to be connected with rock either in its founda- tions or abutments, it should be by means of one or more walls of concrete, cemented tightly to the rock, and extending several feet into the earthen embankment. The earth around these concrete cut-off walls should be carefully selected, puddled and rammed, so as to give the tightest possible connection. In preparing the foundation of an earthen dam for the embankment, the surface soil should be removed from the foundation to a depth sufficient to remove all coarse vegetation, and the entire foundation scored by deep furrows running longi- tudinally of the dam, so as to form a good bond with the embank- ment material. If pervious strata of sand or gravel occur below the surface, one or more trenches should be carried down through such strata for the entire length of the foundation, and refilled with selected material carefully rammed or puddled in place. 408 DAMS c. Springs in Foundations. It sometimes happens that one or more springs occur at the site where it is desired to build an earthen dam. This is very undesirable, and if possible a site should be selected which is free from this menace. Where TRUCKEE-CARSON PROJECT NEVADA LAHONTAN DAM GENERAL PLAN OF DAM FIG. 197. Plan of Lahontan Dam, Carson River, Nevada. this is not possible, the utmost precaution must be taken to prevent the spring from endangering the structure. If possible the spring should be followed to its point of emergence from the rock. If the rock is hard and firm, it may be possible to seal STORAGE DAMS 409 the spring with a mass of concrete. If this is done, careful examination should be made to determine whether the spring has broken out at some other point. If the spring does not flow from rock, it may be followed to relatively firm material, and there confined into a pipe and led away and discharged at a distance from the dam, due precaution being taken against the percolation of water through the bank along the pipe. Or still better the pipe may be carried upward and sloped upstream if necessary, until its top is above the flow line of the reservoir, and the water allowed to flow out at the top if it will, and fall into the reservoir. If the springs are small, it may be possible to smother them by puddled material, but this should be done with caution, and careful examination made to detect their escape at other points. This method should never be attempted, however, unless excellent and abundant puddle material is used for the purpose, and the spot is buried under a great mass of which the weight and character is a guarantee against any escape of the water or any portion of it. This process should never be applied to springs below the center line of the dam, where they might saturate the lower portion of the dam and cause a tendency to slough. The handling of springs in foundations is a very impor- tant and delicate problem requiring experience and mature judgment, as an error in the solution of this problem may lead to serious consequences. d. Safe Slopes for Earthen Dams. One of the strongest tendencies to failure of an earthen dam is the saturation of its mass with water, with a consequent tendency to neutralize its cohesion and to cause parts of it to become of a semi-liquid nature, so that it will slide or slough. This is one great reason for the importance of making the water face as tight as possible against the entrance of water, and of providing drainage under the downstream half of the embankment. For this reason, the water slope of the dam is made relatively flat, generally i on 3 or flatter, and the downstream slope always i on 2 or flatter, although the natural angle of repose of the earth used may be nearly as steep as i to i. The gentle slope of the water 410 DAMS STORAGE DAMS 411 face of the dam contributes to its stability not only by providing a large amount of weight, but by giving the direction of water pressure a downward tendency, the direction of pressure of a liquid being always normal to the surface upon which it is exerted. The water pressure on a 3 to i slope of a dam being more nearly vertical than horizontal increases its effective weight, and increases its stability against sliding, and also against overturning if such a method of failure were possible. It appears therefore that the mass and shape of an earthen dam as thus determined is such that no attention need be paid to its stability against sliding on its base or on any horizontal joint, on account of the pressure of the water in the reservoir. The other considerations, however, make the slopes of the two faces of the dam very important. It is impossible to arrive by theoretical reasoning at reliable general rules for the slopes upon which any given materials will be stable when saturated with water. In general, a clay bank when supersaturated has very little stability, and the same is true in a less degree of a clay loam and of a sandy clay loam where the clay content predominates. Where clay must be used it is very important to prevent its saturation, by excluding the water so far as possible, and providing an exit for such water as may enter it. For this reason it is desirable to employ gravel for the downstream half of an earthen dam, as this will permit the slow escape of contained water, without danger of sloughing or erosion. For the same reason it is highly desirable that the impervious portion of the dam also be composed largely of gravel, using fine sand and clay only so far as necessary to completely fill the void spaces in the gravel. The great Gatun Dam on the Canal Zone, Panama, is built on the gentlest slopes of any dam of which we have record. The outer slope is about 16 to i for 40 feet in height, and there increases to 7 to i, and finally to 4 to i near the top. The water slope averages about 4 to i for most of the height. The base width is thus 2640 feet while the height is only 105 feet, and the contents over 21,000,000 cubic yards. 412 DAMS The reasons for adopting these very conservative slopes are several: 1. The sluiced clay of which the base of the dam is com- posed was considered practically impervious, or at least much less pervious than the valley material of the foundation. The broad blanket of sluiced clay confines waters percolating in the foundation and prevents their escape until they have traversed so long a distance that the accumulated friction has destroyed any possible hydraulic head and rendered the seepage inert. At the same time any seepage through the dam would produce a plane of saturation the surface of which in the clay material would be steep enough to intersect the foundation long before reaching the surface of the slope, and thus minimize any possible tendency to slough. 2. The adopted method of construction was the sluicing of clay into the body of the dam which is always very slow to drain and consolidate, and especially so in the wet climate of Gatun, and it was necessary to provide flat slopes for stability during construction. 3. It was desired to make an embankment so heavy that an alien enemy temporarily in possession could not quickly cause a break for the purpose of destroying the dam. The practice so common as to be considered almost standard is to build earthen embankments with slopes of 3 to i on the water face and 2 to i on the outer or downstream face. These slopes may be flattened to fit cases where conditions of stability are not favorable, and may be somewhat steeper where rock or gravel predominates on the slopes, or other conditions favor unusual stability. The slopes are frequently made steeper near the top than lower down, and this is a logical practice, as it broadens the base by the use of less material than required for uniform slopes. On the water face the steeper slope near the top tends to check the advance of waves. The top width is generally made to vary from 10 feet for banks of moderate height to 20 feet or more for high dams. The top should be slightly crowned to prevent rain water from STORAGE DAMS 413 standing on it in pools and causing saturation. The top of the dam should be high enough above normal high water so that no danger will ensue of waves from the reservoir overtopping the embankment. Where great wave action is to be expected a concrete wall is sometimes provided at the water edge of the top to break the waves. See Fig. 201. e. Slope Protection. The flattening of the slopes of an earthen dam, while increasing its security against sloughing and sliding, and adding to the security against the wave action upon the material of the slope, adds materially to the cost by increasing the yardage, and on the water slope by increasing the area that has to be protected from wave action by pavement or riprap. Where suitable rock is abundant for this purpose it may be inexpensive, but in some cases a concrete pavement is necessary, and it becomes desirable, for reasons of economy to reduce this area to the smallest dimensions. This reason led to the adoption of slopes for the Owl Creek Dam, South Dakota, of 2 to i on the water side for the most part, and con- stitutes it one of the boldest earth dams for its height now in existence. Its water face is protected by a heavy concrete pavement. Where rock is plentiful the water slope should be protected by a pavement of dry laid rock not less than i foot thick where wave action is moderate to 2 feet where heavy wave action is to be expected. Precaution should be taken to prevent the washing out of the earthy material from behind the pavement through the crevices. To prevent this a layer of small broken rock or screened gravel of diameters from i to 4 inches should be provided, directly under the pavement. This will be too coarse to wash out through the crevices of the pavement, and will break the force of the water running in and . out of the cracks between the paving stones as waves advance and recede. If rock is very abundant, and of poor shapes to form a suitable pavement, it may be dumped roughly on the slope without placing by hand, but in such case a greater thickness should be used, and small broken rock or screened gravel should be employed for its foundation as described above. 414 DAMS STORAGE DAMS 415 Where rock is not to be obtained at reasonable cost it some- times becomes necessary to protect the face of the dam from wave action by the use of concrete pavement. This may be made in place on the slope, or may be manufactured in blocks at a more convenient point and placed on the dam as paving blocks. Such blocks should extend at least 10 feet up and down the slope, and may be any convenient width in the other direction. The ample dimension up and down the slope is important, as other- wise in a great storm the receding waves may leave a sufficient hydrostatic pressure behind the blocks to move them if too light, and thus cause a breach in the pavement. Such accidents have occurred in a number of cases in the region of the great plains, where rock is scarce and concrete has been extensively employed for paving dams. Probably the best form of concrete pavement yet employed is a series of concrete strips, 15 or 20 feet wide, running from the toe to the top of the dam, with vertical joints the entire length of the slope, but no horizontal joints. This pavement should be 4 or 5 inches thick if reinforced, or 6 inches if not. Under each joint, running from toe to top of the dam, should be a concrete sill, about 6 inches square, built into the earth- work and flush with its surface. After seasoning, the upper surface of these sills should be oiled or tarred, to prevent adher- ence to the concrete slabs afterwards built upon them, and to make a tight joint. This will permit these joints to absorb the expansion and contraction in a horizontal direction, and the vertical movement to be communicated to the top. Where rock and concrete are very costly and coarse gravel is conveniently available, it may be possible in some cases to depend on using this in great abundance for slope protection, as has been done on the two large embankments of the Deer Fat Reservoir in Idaho. In these cases, after finishing the dam to a 3 to i water slope and 20 feet top width, the top was widened by dumping from cars on the water slope, the coarsest gravel available, which was sand and gravel varying from bowlders of 50 pounds weight through all intermediate sizes to fine sand and silt, the 416 DAMS STORAGE DAMS 417 proportion of coarse material varying, but never great. - In this way the upper embankment received about 95,000 cubic yards of extra material, which took its natural angle of repose and widened the top of the embankment from 20 feet to 51 to 67 feet. As the waves of the reservoir attack the gravel slope they gradually undermine and cause the gravel to creep down the slope. The finest materials are carried into the lake and slowly deposited, those a little coarser washed down to the toe of the slope, and the other materials are carried down less and less freely as they become coarser. In this way by the automatic sorting of the water, the fine materials are deposited on the bottom of the reservoir near the toe of the slope and serve to make this area more impervious. The coarser sand collected near the bottom serves to give the bank a flatter slope, and the materials, left on the slope become gradually coarser from the bottom upward, and the coarsest cobbles and bowlders are left on the upper part of the slopes in the capacity of riprap, and finally each material will take the slope at which it can resist the wave action, resulting in a flattened slope paved with water-selected coarse material of gravel and cobbles. Experi- ence so far indicates success for this experiment, with a large saving over the cost of paving the slopes with concrete. /. Percolation. The flow of water is ordinarily due to a slope in the water surface. The action of gravity causes it to move from the point where its surface is highest, toward the point where it is lowest. This is true of a stream, or a lake, and is equally true of underground waters. The resistance to flow by the materials of the soil is very great, so that subter- ranean waters move very slowly, and their movements are further complicated by capillary action, but gravity flow depends upon slope, and will not occur without slope. The rate of transmission of water through any given soil varies with the sine of the angle which the surface of the per- colating water makes with the horizontal. It also varies with the size of the interstices in the material traversed. Clay, for example, may have and usually does have, a larger percentage 418 DAMS FIG. 201. Owl Creek Dam, near Belle Fourche, South Dakota, Showing Concrete Paving. FIG. 202. Upper Deer Flat Embankment, Showing Beaching of Gravel slope. STORAGE DAMS 419 of voids than sand or gravel, but they are so minute that perco- lating water is greatly retarded by friction, and moves very slowly, and for this reason clay is regarded as the best earthy material to resist the passage of water. After long and careful investigation Slichter gives the rate of flow for a grade of 10 feet per mile, in various materials as follows : TABLE XXXVII Material Miles per Year Velocity Feet per Year Fine sand O.OI 52.8 Medium sand o 04 216 o Coarse sand o 16 84 c o Fine gravel 1.02 5386.0 The more minute the openings through which the water must pass, and the greater the friction of passage, the greater must be the slope necessary to induce a perceptible motion. Well-compacted clay presents great resistance to the passage of water, and is therefore very desirable as a leading element in the upstream half of the dam. Since we cannot make an earthen bank entirely tight, it is important to make it so nearly so that the slope of percolation of water from the reservoir will be steep, and will reach the ground before it reaches the lower toe of the dam, so that the downstream slope of the dam will not become saturated and induced to slough. For this reason it is desirable that the entire upstream half of the dam be made as tight as practicable, and for the same reason, some relief in the downstream half is desirable. This may be obtained by making this portion of the dam of coarse material, as coarse sand or gravel, "which will allow small quantities of percolating waters to escape freely without danger of erosion. The same result may be obtained by installing under-drains about the center of the lower third of the foundation. These methods of relief, however, should not be permitted, unless reasonable tightness is sure to be 420 DAMS attained in the upper half; for if spaces of any size occur in the fine material, the free escape provided may permit erosive velocities, which by enlarging the channels, may cause disaster. Fragments of quartz or granite of which sand and gravel are often composed, are practically impervious, and large fragments of such material in an earthen mass tend to make it impervious provided the spaces between such fragments are properly filled. Following the above principles to a conclusion, we find that the tightest mixture we can make consists of large fragments of impervious gravel, with enough smaller fragments to fill the space between, and still smaller fragments to fill the space between these, and so on, ending with the finest clay. The author has observed some mixtures in nature that proved to be remarkably water-tight under considerable pressure, two of which were shown by mechanical analysis to be graded as follows : TABLE XXXVIII Material Passing Held on Percentage No. i No. 2 Gravel 2-inch sieve 8 7 I r -} Gravel 2-inch sieve i -inch sieve 9-4 9-o Gravel i -inch sieve No. 4 sieve 44-5 43 - 1 Sand No. 4 sieve No. 20 sieve 18.4 171 Sand No. 20 sieve No. 50 sieve 5-i 4-8 Sand No. 50 sieve No. 100 sieve i .4 . Z Sand No. 100 sieve No. 200 sieve i.4 . i Clay and silt No. 200 sieve ii . i 10. I Total IOO.O IOO.O Sample No. i was taken from near St. Mary Lake, Flathead Reservation, Montana, and No. 2, from near Lake Kachess, Washington. In each case the samples were taken from the sidewalls of test pits in the immediate vicinity and far below the water in the lake, and were so tight that practically no leak was noticeable. Both samples were from glacial moraines, STORAGE DAMS 421 unstratified, and thoroughly mixed. Classifying the material as gravel, sand, and fine material corresponding in size to Port- land cement (taking for this purpose all the material passing the loo-mesh sieve) we have: TABLE XXXIX Sample No. i, Per Cent Sample No. 2, Per Cent Gravel, held on sieve No. 4 Sand held on ^ieve No 100 62.6 2A O 67.4 22 A Fine material passing No. 100 12.5 10. 2 In combining such materials for the purpose of producing a tight mixture, it is well to add some excess of the finest materials, rather than run any risk of leaving unfilled voids between the coarse ones. The ratio of 1:2:5 corresponds almost exactly with sample No. i, and if we allow for the small percentage of clay and fine silt usually occurring in natural sands, we have nearly the percentages of cement, sand and gravel found in good concrete, which is also designed to be nearly impervious. This mixture can be further improved by increasing the percentage of coarse gravel to near the maximum that can be used and still have the voids well filled by finer material. Experi- ments show that the amount held on the 2-inch sieve can with advantage constitute fully half of the mixture when the parts are measured separately. The size, shape and relations of the different sizes are so indefinite and so variable in practice that no exact rules can be adopted with profit, but the following proportions constituted a rough guide: Coarse gravel, held on 2-inch sieve i.oo cu.yd. Fine gravel, held on No. 4 sieve 35 " Sand, held on No. 100 sieve 40 " Clay and silt, passing No. 100 sieve 25 " Total . . 2 .00 These proportions, when well mixed and compacted with a small quantity of water and rolled, can be reduced to about 422 DAMS if cubic yards in bulk. Such a mixture can rarely be obtained in practice, but it gives the maximum weight and stability, as well as water tightness. Much discussion has been held in the past regarding the merits of the various types of earthen dam mentioned, especially between the partisans of masonry corewalls as against those opposing such walls. Both types have their uses, depending on the local conditions. A wooden or plank core should never be employed, as this is sure to decay, and both before and after decay it affords a convenient path along which leakage water may freely travel and find an outlet if any exists. A central core of puddled earth is advisable only when material suitable for such puddle is too scarce and expensive to permit the upstream third or half to be so composed, which is better when feasible. A masonry corewall affords excellent facilities for making connection with the outlet conduit, with rock foundation or abutments, and with masonry extensions or other structures. The corewall may be necessary in cases where no impervious earth in procurable, or where it contains a considerable per- centage of soluble salts, so that percolating water might in time carry out in solution enough salts to leave the mass pervious and unsafe. Such a case was the Avalon Dam on the Pecos River in New Mexico, built by the Pecos Irrigation Company, which failed in 1904, without overtopping. The most plausible explanation, being the gradual leaching of the sulphates of calcium and magnesium, until a finely honey-combed con- dition was reached after which a slight concentration of the leakage, afforded openings permitting destructive velocities, and disaster followed. In the reconstruction, a corewali of concrete was used in the new portion, and the remnant of the old bank was provided with one of steel sheet-piling. These have now been in successful service over ten years. Where these special reasons for a corewall do not exist, the tendency for it to produce supersaturation of the upper slope of the dam is objectionable and it also interferes with the best consolidation of the interior of the embankment. STORAGE DAMS 423 The most general practice in dam building in America inclines to type 2, where great effort is put forth to make the upstream portion of the dam tight with selected material care- fully placed and compacted, and building the downstream portion of coarser material, affording drainage, and having less tendency to slough when saturated. Frequently this plan is supplemented by providing a corewall of rubble or concrete, to insure against erosive velocities and to guard against the ravages of burrowing animals. The latter provision is most important where frequent inspection of the slopes of the dam cannot be assured. Where clay is the only material available for construction, a very good structure can be secured by building it homogeneously in thin layers, moistened and thoroughly rolled. It is important that the moisture added to clay be merely sufficient to permit compacting, as any excess of water in clay carries a tendency to flow, and also causes swelling which may lead to cracking as the water is withdrawn. The embankment being thus finished nearly dry, any absorption of water from the reservoir will tend to swelling and to make the structure tighter. Such a structure is the Owl Creek Dam of the U. S. Reclamation Service near Belle Fourche, South Dakota. A novel method of preventing the saturation of the down- stream half of an earthen dam has been employed in the design of the dam built .at the outlet of Sherburne Lake on Swift Cur- rent Creek in northern Montana. At this site it was not practicable to obtain clean gravel in sufficient quantity for the downstream slope to obviate the danger of sloughing if the material were saturated with water. To prevent seepage from reaching this portion of the dam by percolation through the upstream half, a core was placed about midway of the location, not of concrete or puddle, to stop the water, but of screened gravel to receive and conduct it freely downward to a system of drain pipes through which it could drain into the stream below the dam without coming in contact with the dam below the core at all. This provision seems to have accomplished its purpose perfectly. 424 DAMS g. Methods of Construction. The materials for constructing an earthen dam may be excavated and transported to place in various ways. Where sand, clay or loam or their combina- tions occur near the dam site, one of the commonest and cheapest methods is to plow and load it into dump wagons by means of elevating graders, drawn by horses or by traction engines. This method is well adapted to localities where the soil is shal- low and underlain by rock. The dump wagons, drawn by horses, deposit the earth while in motion, and additional spread- ing is accomplished by road graders or Fresno scrapers. Where the material occurs in deep deposits so that a face of 10 feet or more can be obtained, steam shovels may be employed to load it into dump wagons or cars in which it is transported to place. Where the earth is transported in cars, it is often best to carry it to place on the dam on a track laid on the embank- ment, and moved back and forth as the work progresses. Some- times when the abutments of the dam are steep, it is necessary to build a high trestle along or parallel to the axis of the dam, and dump the cars from a track built on this trestle. The cross braces of the trestle should be removed as the bank rises, as they otherwise would furnish routes for the lateral passage of water, and thus encourage leakage. The vertical members offer no such menace, and it is necessary to leave them in place. Material dumped from trestles is transported to its place in the dam by means of scrapers, and may be further spread and leveled, with road graders. Before sprinkling or rolling it is best to remove all rocks more than 4 inches in diameter, from the body of the dam, as these may prevent the proper action of the roller, and leave uncompacted spots in the bank. All such rocks are valuable parts of the bank, and are most useful on the upper and lower slopes, where they serve to protect the dam against the elements and are also valuable as an influence against sloughing. If further mixing is required, it may be secured by the use of a common two-horse cultivator equipped with 4 or 6 shovel plows, like that used for cultivating row crops. After the spreading and mixing is accomplished it is generally necessary to sprinkle with water in order to prepare the material STORAGE DAMS 425 so it will " pack." This may not be necessary in wet weather, or in a moist climate, but usually is in regions where irrigation is practiced. The .cheapest method of sprinkling is to lay a 3 or 4-inch pipe along the edge of the embankment, into which the water is forced under pressure by a pump, or by gravity if practicable, and then attach hose to branches of this pipe at frequent intervals, from which the layer of earth is sprinkled preparatory to rolling. Care should be taken to apply the water uniformly, so that dry spots will not be left imperfectly FIG. 203. Wheeled Scraper. compacted, and if considerable clay or loam occurs in the material, the water applied should be only that required to make it pack, as an excess of water causes swelling of clay, and may cause a boggy condition which will give trouble in rolling,- When a bank of clay is thus built, nearly dry, any further absorption of water causes some tendency to swell and thus further compact the material and increase its tightness. The compacting should be accomplished by spreading in layers 5 or 6 inches, sprinkling and rolling with a traction engine, or other suitable roller. 426 DAMS Grooved rollers drawn by horses are often used, and the com- mon road roHer is sometimes employed, but neither of these give as good results as a heavy traction engine, driven longitudinally along the embankment. It may be advisable to provide such an engine with steel tires to widen the tread, but one of its chief virtues is the fact that it does not leave a wide, smooth plane, as does a road roller, but rather compresses the earth in a series of grooves, and it also concentrates greater weight on each spot at one time. h. Hydraulic Fill. Under some circumstances it is economi- cal to excavate and transport the material to place in the dam by means of water. Very good results may be obtained by this method properly carried out. To do this it is necessary to have water under heavy pressure, so that delivered through a nozzle a stream can be projected with sufficient force against the material to be excavated, to loosen and carry it away. This is then transmitted through pipes or flumes to its place in the dam. The necessary pressure to produce a cutting jet of water may sometimes be secured by diverting a stream at a higher elevation and bringing it in a ditch or flume to the vicinity of the dam site, from 100 to 200 feet above the deposit of material to be excavated, so as to provide the necessary head by gravity. The water is then confined in pipes and conducted to the barrow pit where a hydraulic monitor with movable nozzle projects it with force against the material to be excavated. Where the conditions do not permit the method above described, the necessary head may be obtained by means of large pumps pushing the water through pipes of ample capacity, at a velocity sufficient to cut and carry the material from the barrow pit. If, then, it is necessary to elevate the material to place it in the dam, other pumps may be installed and the material mixed with water may be pumped through pipes and deposited where required. Where the hydraulic method of transportation is used, it is necessary to build dikes at the upper and lower faces of the dam, and discharge the water laden with solid material between them, STORAGE DAMS 427 FIG. 204.- Cold Springs Dam under Construction, Umatilla Valley, Oregon. < FIG. 205. Grooved Concrete Roller. 428 DAMS where the solid matter is settled and the water drawn off nearly clear. Where the material sluiced is all or mainly clay, it is slow to settle, and remains in a liquid or semi-liquid condition for a long time. It is then necessary to keep the retaining dikes strong and heavy, in order to sustain the heavy side-pres- sure of the mobile core. Where the material to be sluiced is mostly clay, a serious problem is presented of draining the sluiced material. The clay holds on to the contained water with great tenacity, and when saturated, assumes a semi-liquid character which exerts a hydro- static pressure on the retaining dikes which may become greater than their powers of resistance. The pond of water constantly maintained on top of the fill is apt to keep the mass of clay Scale of Feet -Stripped Surface U u ^Original Surface DAM AT NECAXA, MEXICO FIG. 206. saturated, and in some cases the lateral pressure of the mobile clay has broken the dikes and caused slips. Two notable accidents of this kind have occurred with very high dams, under circumstances so similar as to attract widespread atten- tion and comment. The cases were the Necaxa Dam in Mexico, and the Calaveras Dam in California. At Necaxa the design of the dam was such as to give two embankments of porous material, largely rock, resting upon a central embankment of clay, the latter having theoretical side slopes of i to i. The base width of the outside embankments composed of rock and sand, was about 350 feet on the upstream side, and 250 feet on the downstream side, leaving for the cen- tral core a base width of about 365 feet. The outer slope of the upstream bank was 3 to i, and that of the downstream bank 2 to i. STORAGE DAMS 429 The theory of the design was that, as the rock embankments advanced in height and rested upon the clay, they would aid in forcing the water out of the clay by the superimposed weight, so that the portion of the clay underlying the rock at least would become hard, while the center would harden later as the weight of the clay increased. The materials were used in about the proportions they occurred in the pits. Owing to construction difficulties the progress of the upstream embankment fell behind, and was frequently left very narrow, the place being filled with clay. This defect persisted at a cer- tain point near the center where the sluicing flumes from the two sides should have met but did not, leaving this part of the rock very thin for a considerable elevation, and at this point the break occurred. The clay suddenly burst through the bank and flowed out into the reservoir to the quantity of about 720,000 cubic yards. Also the defective bank was largely composed of an eruptive rock having a specific gravity of only about 1.8, whereas the downstream bank was largely of limestone with a specific gravity of 3 or more. The reservoir was empty at the time of failure. The Calaveras reservoir contained a depth of 55 feet of water at the time of the slip, but in other respects there was a strong similarity of conditions as shown in the following tabulation from the Engineering News- Record: TABLE XL. TWO Iv\RTH DAM SLIPS Xecaxa Calaveras Yardage of completed dam Yardage in place Percentage complete at slip Length of gap feet .... 2,130,000 1,926,000 90.4 39 3,085,000 2,8oo,OOO 90.7 700 975 1300 Approximate height of slip, feet 172 170 The similarity of yardage in the two slips, notwithstanding the longer gap at Calaveras, was due to the fact that no material below the level of the water in the reservoir moved. 430 DAMS At the Calaveras dam a movement of the upstream dike occurred on June 18, 1917. Sluicing was immediately stopped and the movement continued at a decreasing rate for three days and then stopped, the total movement being between 2 and 3 feet. Sluicing was resumed on July 7, and continued for 12 days, when movement was again noticed and sluicing was stopped. The steam shovel work on the dikes was continued, however, and each dike widened 60 feet into the pool and raised 30 feet or so. The central core of liquid clay was raised 12 feet by the sinking of the rock-fill into it. On February 12, 1918, sluicing was resumed, and again stopped on March 4, on account of further movement, which continued irregularly until March 24 when the failure occurred as a sudden movement. The upstream dike broke and the liquid clay flowed out into the reservoir, overturning and burying the outlet tower. These two accidents, as well as small slips at the Gatun Dam and else- where, emphasize the importance of providing self-sustaining stable dikes to confine sluiced clay, during the very slow hard- ening process. Where the material sluiced into the dam contains coarse elements, as gravel or rock fragments, it is desirable to deposit this on the slopes of the dam, and the finer material in the interior, where it will form a tight puddle core. The coarse material placed on the water slope will, if sufficiently coarse and abundant, protect the dam from the destructive action of the waves, and that en the lower slope will protect it against the erosion of wind and rain, and on both slopes will guard against sloughing. The entire body of the dam being of sluiced material settled in water will, if properly consti- tuted and disposed as above described, form an ideal structure in stability and efficiency for its purpose. Fig. 207 illustrates the method of transporting mixed materials and disposing them as above described. Parallel flumes are built lengthwise of the dam, which receive the materials brought from the pit. These flumes are provided with gates on both sides that can be opened and closed at will, and at the point where it is desired to dis- charge the load, an iron screen or grillage with openings large STORAGE DAMS 431 432 DAMS enough to pass most of the sluicing materials, but small enough to stop the coarsest, is placed in the flume at an angle of about 45 degrees, just below an open gate on the side of the outer slope of the dam, and this grillage deflects the coarse material which falls on the slope, while the water carrying the finer material rushes through and is discharged on the inner side into the central pond. As it falls, the coarsest of the material is deposited, and the water, no longer confined to a narrow channel, can carry only the sand and clay. As the slope flattens the sand is deposited, the coarsest first, and the fine nearer the pond, while the clay and impalpable silt is carried into the pond, and settles but slowly. A weir is provided where the surface water is drawn off at a point as remote as convenient from where the water enters the pond with its load of silt. There is always a tendency to stratification in the central pond, and due precaution must be taken to prevent continuous strata of sand from extending through the puddle core, as this would furnish an opportunity for the passage of water. Such strata may be broken up by men wading about in the pond, and plung- ing boards or paddles into the mud as far as possible in such a position as to cut the strata and permit the deposit of clay in the cavities made by the paddles. Hydraulic methods are best adapted to mixed materials, as the sorting capacity of water can be utilized to separate the different sizes and produce outer slopes of rock or gravel, which have no tendency to slough, and will resist the action of waves on the water side and the wind and rain on the other. The finer material can thus be concentrated in the center, where if it contains considerable loam or clay it forms a puddle core and imparts a water-holding capacity to the structures. Sometimes it is found desirable to excavate and transport the material to the dam by dry methods, deposit it in dikes along both faces, and then wash a portion of it into the center with a hydraulic jet, forming a pond in the center and producing a puddle core. This combination of hydraulic and mechanical methods is best adapted to localities where the material is a mixture of coarse and fine, with many rocks too large to be STORAGE DAMS 433 transported with water or consolidated with a roller, and too numerous to be rejected. Except where the hy- draulic method is used, it is best to put the finest and most imper- vious material near the water face, and if enough of this is readily available, one-half or two-thirds of the dam should be so built, leaving the lower third to be built of gravel or other coarser material, grading from fine to coarse as gradually as convenient, so that the coarsest material used is on the downstream face. The transition from fine to coarse material should be as gradual as possible, however, to pre- vent any tendency for percolating waters to carry the fine material through the gravel. The ideal condition is analo- gous to a filter, where a very fine material is em- ployed on the water side and becomes very gradu- ally coarser in the di- rection of the flow of water. The voids being 434 DAMS everywhere too small for the passage of the finest particles of earth in their vicinity. At least one-third, however, and better still one-half or two-thirds of the dam on the water side, should be made as tight as possible. There is decided advantage, however, in having the downstream part of the dam composed of gravel, as this has no tendency to slough when wet, and it is practically impossible for percolating water to erode channels through gravel, as it will not bridge over like clay or loam, but will generally fall into any cavity formed and clog it. It thus offers ready and safe drainage for any waters that may percolate through the upstream part of the dam, and prevents saturation of the interior, with its tendency to slough. For Adjustable Spillway Crest and ^ e ^^*^ 3 ^J^! ] ^/ GraVel Maximum Water Surface E1.4793^^ -JT'Hi'Vv = _-ZZL-=T^^r IJ^fe^GravelCore Permanent Crest of Spillway, El.i7SS- / ^ < ^^ s( *T!oncret Parapet W Coarser "^.-^"Gravel El iic-i :-l ^<,. elected Mater d and Rol FIG. 209. Section of Sherburne Lake jL. j am, showing Gravel Core and Drains to Provide for Seepage Water. these reasons, gravel is a very valuable building material for dams, canal banks, and many other irrigation requirements. Even the impervious portion may be, and preferably should be largely of gravel, as we have seen, although it requires an admix- ture of finer materials to make it tight. An advantageous use of gravel in an earthen dam is illustrated in Fig. 209. In this case it was difficult to obtain sufficient gravel to form the entire downstream half of the dam, and so a core of screened gravel 10 feet thick was placed in the axis of the dam to receive any water that might percolate through the upstream half of the dam and conduct it readily to the base, where it is carried away by tile drains. This is to prevent the saturation of the lower half of the dam and the consequent tendency to slough. The screening of the gravel was for the purpose of removing STORAGE DAMS 435 436 DAMS any sand which would tend to clog and render the drainage imperfect. Fig. 196 illustrates another use of gravel, on the lower toe of the Owl Creek Dam. This gravel was hauled a long distance, and placed in position to load the foundation at the lower toe, where seepage under the dam might soften the earth. The gravel prevents any tendency to slough, while allowing seepage waters to escape harmlessly. 4. Rockfill Dams. The rule that earthen dams should be built of material fine and water tight on the water face, and grade very gradually into coarser material toward the down- CROSS SECTION OF LOOSE-ROCK AND EARTH DAM 40 60 SCALE OF FEET FIG. 211. Rock-Fill Dam, Snake River, Minidoka Project, Idaho. stream face, suggests a combination often employed, of earth and rock-fill, where earth is used on the side toward the reservoir, and loose rock on the other side. The transition, however, should be as gradual as possible, to prevent any leakage from washing the earth through the rock-fill and causing a breach. If suitable earth is plentiful near by, it is much cheaper to place than the rock, and will naturally predominate, but where it is scarce, or must be transported a long distance, economy may require the use of rock in the main body of the dam, with only enough earth to form a water-tight blanket on the water face. Where insufficient earth for this purpose is available, it becomes neces- sary to secure water-tightness by other methods, and we have the rock-fill type, pure and simple. Where a dam is built of loose rock, it is necessary to employ some special measures to secure water-tightness. This is some- ROCKFILL DAMS 437 times obtained by providing a deck of lumber on the water face, carefully caulked and fastened to timbers built into the rock. The lumber deck should be liberally treated with asphalt or PLAN C ft oss SECTION FIG. 212. Plan and Cross-section of Bowman Dam. durable paint to preserve it from warping and deterioration, and it should be inspected and repaired whenever the water is drawn out of the reservoir. 438 DAMS Steel has also been employed to form a water-tight deck on a loose-rock dam, and serves the purpose well if protected from oxidation. It must have frequent expansion joints to provide for changes in temperature. In some cases a corewall of masonry is built in the center to secure water-tightness, and in one case, the lower Otay Dam in Lower California (Fig. 214) a diaphragm of steel was employed in conjunction with the corewall. This diaphragm was one- third of an inch thick near the base, and one-quarter of an inch ELEVATION FIG. 213. Elevation, Plan, and Cross-section of Castle wood Dam, Colorado. in the upper part. It was anchored firmly to the masonry foundation, and coated with asphalt applied hot. A layer of burlap was applied to the asphalt while still hot, and over this a harder grade of asphalt wp,s applied, and the whole was encased in a rubble masonry wall laid in Portland cement concrete. This wall was 6 feet thick at the base, tapering to 2 feet at the height of 8 feet, which thickness was maintained to the top. The top width of the dam was 12 feet, and the rock was dumped in place with face slopes about i to i. The dam was 150 feet high above the bottom of foundation, and 565 feet long ROCKFILL DAMS 439 440 DAMS FIG. 215. Elevation and Cross-section of Walnut Grove Dam. Vv.-,..-r : .<..^ ,', oo. 40- 60' ' gSg/^-z^ '/<~12/L J CROSS-SECTION OF DAM FIG. 2 1 6. Rock-filled Steel-core Dam, Lower Otay, Cal. ROC KF ILL DAMS 441 on top, forming a reservoir of 42,000 acre-feet capacity. A few hundred feet east of the dam a channel was cut through the rock, 30 feet wide, to a depth 10 feet below the crest of the dam, to form a spillway. This proved to be insufficient, and in the great storm of January, 1915, the reservoir filled and the dam was overtopped by the flood and destroyed. The drainage area is about 12 square miles, and the capacity of the spillway about 5000 feet per second, with water standing even with the crest of the dam. The Walnut Grove Dam in Arizona is another case of a rock- fill dam that was washed out by overtopping of the structure by a great flood wave. These failures do not condemn the rock-fill type of construction, but emphasize the importance of providing abundant spillway capacity so that by no possibility can the dam be overtopped by flood waters. For similar rea- sons it is desirable that the largest and best rocks obtainable be placed at and above the downstream toe of the dam, to resist any excessive leakage that might accidentally occur. When properly built of good, sound, durable rock, and supplemented by an ample spillway, the rock-fill type of dam has no superior for safety and permanency, and has, indeed, some apparent advantages in resisting earthquake shocks, CHAPTER XVIII MASONRY DAMS MASONRY DAMS may be classified with reference to their materials of construction into four main types : 1. Coursed masonry, or cut stone laid in cement mortar. 2. Rubble masonry, or rough uncoursed stone laid in cement mortar or concrete. 3. Cyclopean concrete or concrete with large stones or " plums " embedded therein. 4. Plain concrete. Where rock is of best quality, coursed cr ashlar masonry will require the minimum quantity of cement, and will also afford the maximum weight and resistance to crushing, since this type employs the maximum proportion of stone and the mini- mum of mortar, and first-class stone is both heavier and stronger than any mortar or concrete that can be made. By reason of the courses it is less firmly bonded together than other types of masonry, and may have therefore less shearing strength along horizontal courses. The work of shap- ing the stones also involves expense, and for these reasons ashlar masonry is not often used unless cement is very costly or a good appearance is especially desirable. Rough uncoursed rubble requires .more cement, but unless cement is very costly is generally cheaper than ashlar because of less labor involved, and its random character and use of very large rock bind the dam together into a monolith, and thus give it greater shearing strength, with less tendency to crack. This type is much used and is very desirable and economical where good rock is abundant. The stones are usually embedded in cement mortar, while concrete may be used to fill vertical joints. 442 CLASSIFICATION OF MASONRY DAMS 443 Cyclopean concrete has large and small rock embedded in it, and differs from rubble mainly in the fact that the former uses rock to a greater extent, while in the latter concrete predominates. It requires less manual labor, and is cheaper under most cir- cumstances, while giving very satisfactory results. It is now more generally employed than any of the other types. The fourth type, Plain Concrete, is used where good rock is not convenient, and gives good results, though not so heavy nor theoretically quite so strong as the other types, unless reinforced with steel. i. Classification of Masonry Dams. Dams built of masonry may be divided into two classes according to their design: 1. Gravity Dams, or those depending for stability entirely upon their weight. 2. Arch Dams, or those depending for stability mainly upon their action as an arch, by which the water pressure is trans- mitted to the abutments. There are many instances of dams in service that would instantly fail under water pressure if weight were the only dependence for stability. They are curved in plan, and resist the pressure of water by arch action. On the other hand there are also many dams which are straight and cannot possibly act as arches, and are stable only because of their weight. Since every masonry dam must have considerable weight, this con- stitutes in every case an important element of its stability, and the two types merge into each other in a very indefinite manner. Many high dams have been built on gravity lines, theoretic- ally safe as gravity structures, but also curved to form an arch as an added assurance of stability. Intermediate types with scant gravity section but arched in plan, and others of gravity section and only slightly curved have also been constructed. Some curvature of plan is always desirable in every masonry dam, and should be provided unless the expense is excessive. Whatever its coefficient of safety as a gravity structure, this can be increased by curving the plan, so that the dam can 444 MASONRY DAMS neither slide nor overturn without crushing the masonry or its abutments. This precaution does not prevent nor interfere with the stability due to gravity and cohesion, and only comes into play to supplement them in case they prove insufficient, and the arch action takes only those stresses which are beyond those provided for by gravity. 2. Methods of Failure. A masonry dam may fail by any one or more of three methods: (a) By sliding on the foundation or on any horizontal joint. (b) By overturning around the downstream toe or any part of the downstream slope as a fulcrum. (c) By crushing the foundation or the masonry. (d) By undermining the foundation, either by blacklash of water pouring over the top, or by piping underneath the dam by water under pressure. Failures sometimes occur by a combination of the above causes. For example the excavation of a deep hole by water falling below the toe of a dam on a weak foundation may remove the supporting rock to such an extent as to cause failure by sliding or overturning, which might not have occurred had the toe been properly protected. A masonry dam generally has an indefinite but important element of strength due to the cohesion of its parts, if care be taken to make it of monolithic character. This is an added security especially against failure by sliding on a joint of the masonry, as this also involves in that case the shearing of the monolith along that joint. This applies especially to gravity dams, the monolithic character being not quite so important in arch dams, which cannot fail without crushing the masonry or abutments, except by undermining. 3. Pressures in Masonry. One of the first questions arising in the design of a high masonry dam is the safe limit of pressure in the masonry and in the foundation. There are really two questions requiring careful consideration, namely, the bearing power of the natural rock in place, and the crushing strength of the concrete. If the foundation is a good quality of lime- PRESSURES IN MASONRY 445 stone, sandstone or crystalline rock, it will sustain a greater pressure than any concrete, and the problem is reduced to the question of safe pressures on concrete, as this must in the base sustain substantially the same pressures as the foundation. If, however, the rock is one of the numerous varieties of soft rock or shale it should be carefully tested for its bearing power. This may be done by carefully smoothing a measured portion of the rock in place, building a concrete block upon it, and loading this with steel rails or other heavy material to an amount greater than the load it is desired to have it carry in the con- struction. Any subsidence should be carefully noted, and the experiment should be repeated on various parts of the rock in question, especially if it appears to vary in quality. Weak zones are to be feared most near the toe of the dam, and next to this in importance is that at the heel. The interior parts of the foundation have less maximum load, and are confined so thoroughly that they will sustain higher pressures. If tests of rock near the toe show notable yielding under the load to be imposed, the limits of pressure must be lowered by spreading the base or otherwise, until they can be safely carried by the material available. The safe bearing loads for natural rock is a very broad subject upon which much has been written and many experi- ments have been made. Many elaborate formulas have been proposed for computing the bearing power of various natural soils, but the impossibility of accurately defining the properties of the many variable materials prevents any exact mathematical treatment of the subject. For the same reason it is difficult to formulate any but rough rules for guidance. Pure clay is poor foundation wherever it is subject to satura- tion, as it becomes plastic when wet, and unless thoroughly confined when in that condition, has little bearing power. If well compacted, and heavily loaded, it excludes the water to such an extent that it will safely sustain a pressure of 4 tons per square foot. Sand has safely carried loads of from 4 to 5 tons to the square foot, and gravel will carry still more. Soft rock and shale have 446 MASONRY DAMS been safely loaded to the extent of 8 to 10 tons, and harder rocks will carry much heavier loads with safety, reaching in the case of granite a crushing strength of hundreds of tons per square foot. Any good sandstone, or limestone, or any rea- sonably hard rock has a higher crushing strength than cement mortar or concrete, and hence the safe bearing loads upon masonry, where good rock is used, depend upon the quality of the mortar or concrete with which the masonry is bonded, and the thinner the mortar joints the greater bearing power. For this reason ashlar or cut-stone masonry with thin joints has especially high resistance to crushing. As concrete is nearly always used in compression, it is impor- tant to make crushing tests upon samples to be used in any important structure. These tests are usually made upon 6-inch cubes, or upon cylinders 6 inches in diameter. Any of the standard testing machines are satisfactory for this purpose, and if such are not obtainable, the test pieces may be loaded with pig iron, sacks of cement, or other convenient heavy materials of known weight, or more conveniently, a lever may be used and an equivalent test made with much less weight. It is important that such tests be made to try out the sand and gravel to be used, as these are sometimes unsuitable, without showing any signs of their defects except upon test. Table XLI gives some pressures of actual service conditions, and some tests to destruction. Creager gives the following for the compression strength of concrete of various combinations; in pounds per square foot: Proportions. Age I Month. Age 6 Months. 1:2:4 35> 000 470,000 1:2^:5 310,000 420,000 1:3:6 280,000 380,000 1:4:8 230,000 300,000 1:5:10 180,000 250,000 i : 6 : 1 2 1 50,000 200,000 FAILURE BY SLIDING TABLE XLL PRESSURES ON MASONRY 447 Structure Material Pressure per Sq.ft. Tons Authority Bridge Pont-y Prydd, Wales. Limestone rubble . . 20.7 I. O. Baker Brooklyn Bridge Granite ashlar 39-5 Duryea and Mayer Washington Monument Cut marble 25-4 Col. T. L. Casey St. Louis Bridge Cut limestone 38-0 Hist. St. Louis Bridge Rookery Building, Chicago. . Cut granite 30 . o I. O. Baker Bear Valley Dam Granite rubble .... 40 . o J. D. Schuyler All Saints Church, Angers . . . Forneaux stone. . . . 43.0 J. T. Fanning Chapter House, Elgin Red sandstone 20. O " St. Paul's, London Portland limestone. 19-7 ' St. Peter's, Rome Calcarious tufa. . . . 16.7 " Various Arch Bridges Cut masonry 60 . o Estacado Hollow-Dam Concrete 17.5 " Vrynwy Dam Prisms Concrete 181 .0 Tests by Sir Andrew Clarke Roosevelt Dam, Arizona. . . . Quartz rubble 23.0 U. S. Reclamation Service Shoshone Dam, Wyoming. . . Concrete 21 .O " Arrowrock Dam, Idaho Concrete. 30.O " " Elephant Butte Dam, N. M. Concrete 14.2 " Kensico Dam, N. Y Concrete 15.8 A.S.C.E. Transactions, Vol. 75. p. 170 Olive Bridge Dam, N. Y . . . . Rubble 15-4 Morrison and Brodie Burrin Juick Dam, Australia 21 .O Bligh, Dams and Weirs, p. 66 Barossa Dam 17.2 P. 112 Lithgow Dam. 13 . o P. 112 Granite Ashlar Test specimens. . . . 583 Austrian Soc. Eng. and Arch. Sandstone Rubble Test specimens. . . . I8 4 it ii Gravel Concrete 1:2:3.... Test specimens .... 128 ii Gravel Concrete 1:3:5.. Test specimens . . . 66 4. Failure by Sliding. The number of failures of dams from sliding on their foundations emphasizes the necessity and importance of taking such precautions as to insure against its occurrence. The first essential is to provide the dam with sufficient weight to overcome the tendency to slide with the coefficient of friction to be expected. This coefficient of friction, however, is so uncertain as to be practically indeterminate except very roughly. The difficulty is to learn exactly the conditions that exist in the foundation, and that will exist after construction of the dam. These may vary at any point, and our investigations may be at points not truly representative. Great dependence, therefore, must finally be placed on expert judgment, after weighing all the obtainable evidence. A few simple rules are, however, of value in this connection. The following 448 MASONRY DAMS values for friction have been published, but should be accepted with caution, because of the impossibility of reproducing the exact conditions: TABLE XLII. EXPERIMENTAL COEFFICIENTS OF FRICTION Materials Coefficient Authority Masonry and brickwork, dry Masonry and brickwork, with wet mortar Masonry and brickwork, on dry clav .65 47 rj Morin < i ( i Masonry and brickwork, on moist clay . ? 2 1 1 Soft limestone on hard, well-dressed 65 i ( Soft limestone on soft wcll-dre^seJ 67 1 1 White clay, fine grained, wet White clay, fine grained moist 34 4.2 Scheidenhelm : i Yellow clay, containing some grit Yellow clay, moist. .68 83 1 1 Yellow clay very wet ro i t Black loam, moist Black loam, wet 74 72 t 1 1 1 Black gumbo, wet 71 i ( If the foundation is of material horizontally stratified, or nearly so, especial care must be taken to exclude water from the foundation and to afford easy means of exit for any small quantity which enters. An imperative requirement in the design of a gravity masonry dam is that there shall be no tension in the masonry on the face of the dam which is exposed to water pressure. Should any tension occur here it will tend to form horizontal cracks or to open existing cracks and permit the entrance of water under pressare and thus produce flotation or uplift, which in turn would increase any tendency to slide or overturn the masonry above the cracks. Tension of the masonry at other points while undesirable, is not nearly so dangerous as on the water face. Where conditions permit, one of the surest and cheapest methods of providing an ample factor of safety against sliding in spite of uplift in the foundation, is to build the dam on a curve convex upstream. If this be done, it cannot slide nor FAILURE BY OVERTURNING 449 overturn without crushing either the masonry or its abutments. Any good masonry is well-adapted to withstand compressive stresses, and it is on this that reliance should be placed when feasible. It is sometimes urged that with a moderate curve to a long radius the compression on the voussoirs of the arch and the abutments would exceed safe limits. This argument is based on the assumption that all the pressure upon the dam is taken by the arch and transmitted to the abutments. This is impossible. Since it is impossible to deprive a masonry dam of its weight, it has resistance as a cantilever irrespective of its plan, and no strains can be transmitted by the arch to the abutments until the resistance due to gravity and shear have been brought into play. The arch can be made to take only the residue, and if large strains are transmitted to the abut- ments, it merely emphasizes the necessity of the curved plan, and proves that a straight dam on the same section would be likely to fail. 5. Failure by Overturning. The tendency of a masonry dam to overturn is in practice less than appears from a theo- retical examination of any short section of the dam. The ten- dency to overturn of such a short section of the dam, if near the center, is met by the necessity of shearing away from the adjoining sections, and the shearing strength of so large a mass of good masonry is very great. The foundation of the dam is usually V-shaped, and the whole dam cannot overturn on the lowest point of the foundation as a fulcrum, and the only line available as a fulcrum for the entire dam is near the top. To overturn around such a line, the dam must rupture on a hori- zontal plane passing entirely through the dam, the resistance to which would be very great if the dam is well built. These considerations all add to the security of the dam against overturning over that indicated by the weight of the masonry and the pressure of the water, both of which are definite elements, in which the probable error of calculation is small. It is significant that our records furnish no instance of failure of masonry dams by overturning, while failures by sliding have been numerous. 450 MASONRY DAMS 6. Miscellaneous Forces. The above discussion considers merely the water pressure in the reservoir, as resisted by the weight of the masonry. There are many other forces to be taken into account under certain circumstances, which may be at times of considerable importance: 1. Ice pressure. 2. Hydrostatic uplift. 3. Wind pressure. In tropical and semitropical regions, ice pressure need never be considered, and the same rule applies to the southern tier of States of the United States. But where winter extremes go below zero Fahrenheit, and the reservoir is likely to be full at such times, ice pressure should be considered. In some cases, where reservoirs are used mainly for irrigation, in cold or tem- perate regions, they are drawn down in the autumn and cannot be entirely filled until the snows melt in the spring, and in such cases ice pressure cannot occur with full reservoir and need not be considered. Little positive data is available as to actual ice pressures in large reservoirs. Ice forms at temperatures of 32 F. and below, and contracts in volume as the temperature falls. If this contraction produces cracks, they usually fill with water which freezes, forming a solid mass again. When the tempera- ture rises the ice expands, and if confined between rigid bodies, such as adjacent bridge piers, may exert a thrust equal to the crushing strength of the ice, which may vary from a small amount to something like 800 pounds per square inch. In a reservoir with sloping sides, no such stresses can occur, and it is seldom that much allowance must be made for this thrust. Local conditions should be carefully considered in each case. A precedent often quoted is a recommendation of a board of eminent engineers that an allowance of 43,000 pounds per linear foot be made for ice pressure in the design for the Quaker Bridge Dam. No definite reason was given for this large allow- ance, and the precedent was not extensively followed. Ice pressure may be prevented by breaking or cutting it MISCELLANEOUS FORCES 451 along the dam when it forms. Its thrust may be minimized by presenting a sloping face to the reservoir at the surface of the water when full. a. Hydrostatic Uplift. The most important force to be considered and provided for in addition to the water pressure in the reservoir is the buoyant force of water entering the foundation or the masonry of the dam under the hydrostatic head of the reservoir, with a tendency to lift or float the dam. Since most materials in nature are not perfectly water- tight, but generally contain seams along which water can travel, it is practically impossible to exclude water entirely from the foundation. It is almost equally difficult to construct masonry so perfect in all its parts as to entirely prevent water under pressure from entering the structure to some extent. For these reasons it is necessary to make some allowance for uplift in the design. With the greatest practicable care, it is impossible to determine in advance to what extent uplift will take place in the completed structure. Reasoning thus, some engineers have contended that the only safe course is to assume that the dam will be subjected throughout any horizontal plane to an uplift equal to the entire hydrostatic head corresponding to the depth of water in the reservoir above the surface of the water in the stream below, and that the dam must be made heavy enough to be stable under such conditions.* If such a cond'tion were possible, it would be necessary to consider it, and to make provision for such part of it as could not with certainty be prevented or overcome. The condition assumed cannot in fact exist or even be approximated in practice. For full hydrostatic head to be exerted upon an entire horizontal joint, requires that there be no point of contact between the masses of rock or masonry above and below the plane or joint in which such pressure occurs. It requires, moreover, that there be no escape for the water at the lower face of the dam, but that it be absolutely confined without loss of head. Both these conditions are practically impossible even with the most unfavorable conditions and the poorest * Van Buren, Trans. Am. Soc. C. E., Vol. 34, p. 493. 452 MASONRY DAMS materials and workmanship. Under the worst conditions that cculd obtain in practice, actual contact would exist through nearly one-half the area of any horizontal joint, and if the struc- ture were reasonably homogeneous, it would afford escapes from the lower face of the dam so abundant that though large leak- age might occur, the hydrostatic head would be nearly or quite consumed in friction in its passage through or under the dam, and could not be in full force throughout the joint as assumed. We know from abundant experience that concrete can be made so nearly impervious that any leakage must be extremely slow and through such minute passages that any appreciable velocity of the percolating waters must consume a large amount of head in friction. We also know that many natural rocks, such as limestones, shales, and most crystalline rocks, are prac- tically impervious except along seams, and that the existence of these may be discovered and largely provided for. As far as the masonry is concerned, it is entirely possible with proper design and good workmanship to practically elimi- nate internal water pressures, first by excluding the water by extra care in placing the best selected materials used in the construction of the water face of the dam, and second by pro- viding an adequate drainage system just below the water face so that any percolating waters may be intercepted and carried away harmlessly before penetrating any considerable distance into the structure. Such provisions have been made in many recent high dams and results show them to be effective. In the Arrowrock Dam on the Boise River in Idaho, besides using a rich mixture of Portland cement mortar and placing it with special care in the water face of the dam, further tightness was secured by coating the surface of the structure with " gunnite " or the product of the cement gun, projected with great force against the face of the dam to which it firmly adheres, and form.s a dense and practically impervious plaster of cement. At a distance of 5 feet downstream from the upstream face of the dam a series of open wells were built into the masonry, at intervals of 5 feet parallel to the axis of the dam, and 5 feet DESIGN OF GRAVITY DAMS 453 back of this row another similar row of wells was provided with the location of each well staggered with reference to the wells of the first row. This reservoir has been filled to overflow several times, and each time remained full or nearly full for several weeks. In all this time the only leakage has been through those drainage wells that coincide with the contraction joints of the dam. Similar provisions against uplift in the masonry have been carried into effect with complete success at the Elephant Butte Dam in New Mexico, and the Narrows Dam on the Yadkin River in North Carolina. At the latter the water-proof coating was of gas tar instead of gunnite. It is thus shown to be entirely practicable to prevent any con- siderable uplift in the masonry itself by rigidly providing certain simple precautions. To exclude such forces from the foundation, however, is not so easy. The precautions to be taken must depend to a large extent upon the character of the foundation, extending far below the base of the dam where detailed con- ditions can be only imperfectly known. In addition to these precautions these dams were built in vertical sections or columns formed by providing joints or seams passing through the dam normal to its axis, and oiling these seams to prevent adhesion of adjacent sections. Alternate sections were carried to con- siderable height and allowed to season before the intervening sections were built, and the latter were placed in cold weather, so that in warm weather the entire structure was placed in compression by the expansion due to temperature. Each of the vertical joints through the dam was provided with one of the drainage wells above described, to intercept any leakage due to opening of the joint from any cause. The pre- caution of building alternate sections in cold weather seems to have been effective in tightly closing these joints as very little leakage has been detected. 7. Design of Gravity Dams. From the preceding pages it appears that the gravity dam must be so designed and con- structed as to have the following characters : i . It must be free from tension, especially on the water face. 454 MASONRY DAMS 2. It must be safe against sliding on any joint or on foundation. 3. It must be safe against overturning. 4. The pressures upon any plane of the masonry or foundation must be kept within safe limits. 5. The entrance of water under pressure into the masonry or foundation should be prevented as far as possible, and where it occurs, should be relieved by drainage. 2% Core Hole. *- Grouted. FIG. 217. Section of Elephant Butte Dam, Rio Grande, N. M. DESIGN OF GRAVITY DAMS 455 456 MASONRY DAMS If the character of the work and the materials of construction are good, and the foundation is good rock, the first three of the above requirements are generally met by so designing the dam that the resultant line of pressure of all forces acting upon the dam will, under all conditions, fall within the middle third of the foundation or of any horizontal joint. If practicable it is desirable to provide a spillway at such a distance from the dam as to avoid any menace to the dam or its foundations from the energy of the falling water, and avoid the necessity of passing water over the top of the dam. If the foundation is good, however, it is feasible to pass the flood waters over the top by making suitable provisions therefor in the design. Any mobile liquid like water, when free to move, exerts a pressure at any point which is equal in all directions. The pressure of a uniform column of water upon a unit sur- face is equal to the height of the column multiplied by the weight of a unit volume of water. At the surface of a lake the pressure is zero. At the depth of 10 feet the pressure upon a square inch surface is equal to the weight of a column of water of i inch cross-sectional area and 10 feet high. In other words, the pressure of water on a unit area of a dam increases directly as the depth, and may be resisted by a reaction increasing in like progression. It may therefore be represented by a triangle having its apex at the surface of the water and its base in the plane of the bottom of the reservoir. Considering this triangle as made up of a series of horizontal courses of masonry, the width of base of the triangle may be found by the following formula: T- ~W'j where T = thickness in feet of dam at a given depth ; d = depth in feet ; w = weight of a cubic foot of water in pounds ; W = weight of a cubic foot of masonry in pounds; / = coefficient of friction of one course of masonry upon the course below it. DESIGN OF GRAVITY DAMS 457 Taking the weight of masonry as 2.3 that of water, and the coefficient of friction as .6, we have from the above equation, as a condition of equilibrium so far as sliding is concerned, A margin of safety against sliding may be provided by increasing the coefficient of d, and still more by bonding the dam firmly to its foundation, and building it as a monolith, so that it cannot slide without shearing the masonry of the structure, or the rock in its foundation. Reference is made above to the advantage of building a gravity dam as a monolith, as this introduces a resistance to shear that strengthens it against sliding on a horizontal joint, and also against some other methods of failure. There are some reasons, however, for providing definite vertical joints normal to the axis of the dam, and these reasons have led to the adoption of such joints in the design of some of the large masonry dams recently built. The principal reasons for this provision are two: Experience has shown that any mass of masonry of con- siderable length subjected to wide ranges of temperature is liable to crack under the influence of cold, and if built mono- lithic, these cracks are ragged and irregular and grains of sand and mortar are loosened to be crushed when warm weather closes the crack, and thus incipient disintegration is invited. They may admit water to the interior of the dam and introduce internal pressures at points where no provision has been made for taking care of it. These troubles may be reduced by build- ing the dam in separate sections with definite predetermined contraction joints normal to the axis of the dam, which can open in cold weather without rupturing the masonry, and where any leakage caused can be intercepted by drains provided in advance. Another good reason for providing such joints is the advisa- bility of avoiding any horizontal joints. New concrete does not adhere well to that which has been seasoned for some time. When masonry work is spread over a large surface like the 458 MASONRY DAMS - = r , s- 8JI DESIGN OF GRAVITY DAMS 459 horizontal section of a large dam, where the surface area may reach 20,000 or 30,000 square feet, it is impossible to always place masonry on former work before it has become seasoned, Elcv. 3215 ' _j<15-G> ff t Spillway BOISE PROJECT IDAHO ARROWROCK DAM MAXIMUM CROSS SECTION SCALE OF FEET | 30 20 10 20 40 GO Xist of Drawings 1 General map and plan of construction work 2 Maximum cross section 3 Plan of dam and diversion works 4 Elevation of developed upstream face 5 Plan and section of spillwaj G Typical section of diversion tunnel 7 Cross sections north wingwalls at tunnel inlet and outlet 8 Cross sections south wingwalls at tunnel inlet and outlet 9 Cross sections of cofferdam ut holes at 10 ft. erg. FIG. 220. Maximum Section of Arrowrock Dam. in fact this desirable condition is more likely to be the exception than the rule. If, however, the work be confined within forms bounding certain definite sections of limited area, this can be carried on at such a rate that new work can always be placed 460 MASONRY DAMS on previous work not yet seasoned, and good bond thus obtained while work on that section is continued. When it becomes desirable, after several weeks or months of concentration on that section, to leave it and go to another, elaborate pains can be taken to leave the surface in such shape with projecting stones, etc., that a good bond will be obtained when work is resumed at that point. We thus secure greater immunity from horizontal joints by providing a limited number of predeter- mined definite vertical joints. DESIGN OF GRAVITY DAMS 461 It is, however, important to take precautions against the liability of the contraction joints to open in cold weather. To prevent this, it is important to carry the masonry up in alternate columns, leaving a number of gaps in the dam to be filled with masonry after the adjacent columns have become seasoned. Considerable heat is generated in the chemical process that takes place in setting cement, and as this stage passes, the cooling process contracts the concrete, producing a tendency to crack. If the intermediate sections are postponed until this contraction has taken place, and also while the further contrac- tion of cold weather is at or near its maximum, a condition is reached wherein the masonry in place is at minimum volume, and by then filling in between them in late winter and early spring, the summer temperature will place the whole mass in compression, and tend to prevent cracking. It is best to make the sections built last much smaller than their predecessors, so as to secure the greatest effect of the precaution described. The vertical joints should be designed with offsets so as to present a series of right-angled turns in the path of any leakage water passing through. The joints should be oiled to prevent adherence, and each joint should be provided with a vertical drainage well near the upstream face, to intercept any leakage and conduct it to the drainage tunnel. (See Fig. 219.) The construction of the dam in columns is illustrated by the view of Elephant Butte Dam, where this was done. (See Fig. 222.) This dam is a demonstration of the success of this measure, which has had no bad effects, and has reduced the leakage to a very small amount. The condition that the line representing the resultant of all the forces acting upon the dam shall everywhere fall within the middle third of the cross-section of the dam, usually requires a thickness from two-thirds to three-fourths of the depth of water to be sustained, depending upon the weight of the masonry. This gives a factor of safety of two or more against failure by overturning by revolving about the lower toe as a fulcrum. As the lower toe is an undulating line, rising to- ward both ends of the dam, it cannot constitute such a fulcrum, 462 MASONRY DAMS and no part of the dam can overturn without shearing the masonry in one or more planes, which gives a large added coefficient of safety in this respect. Pure theory of resistance of water pressure requires that the dam have a thickness of zero at the highest water level. To prevent overflow from wave action or abnormal rise of the water and as a margin of safety it is necessary to carry the FIG. 222. Elephant Butte Dam, showing Construction in Alternate Columns. masonry somewhat higher, and practical considerations demand an appreciable thickness at the top. It is usually desirable to use the top of the dam as a roadway and for this and other practical reasons to give it a thickness of from 10 to 16 feet, depending upon the circumstances. The water face is usually made vertical or nearly so, and the lower face may also be vertical down to the plane where the thickness must increase in order to meet the requirement that the resultant of forces fall within the middle third. This is secured in the average DESIGN OF GRAVITY DAMS 463 case by sloping the downstream face on a slope of about 3 horizontal to 4 vertical, varying, however, with the weight of the masonry. These slopes may continue downward from the top to the point where the pressure on foundation at the lower toe, reservoir full, and on the heel, reservoir empty, reaches the safe limit of pressure either upon masonry or upon foundation. Rubble Concrete Scale, 1 inch =50 feet FIG. 223. Cross-section of Periar Dam, India. At this point the slope of the lower face must be increased to about i on i, to prevent increase of unit pressures, reservoir full. To prevent increase of pressure on the heel a slope of the upper face must be adopted, which will increase the bearing surface as fast or faster than the vertical pressure. It is sufficient, as a rough rule, to begin the batter just above 464 MASONRY DAMS the point where the limit of pressure is reached, and carry it down on a ratio of i horizontal to 10 vertical. It is reasonable and logical to assume a higher limit of safe pressure at the heel of the dam than at the toe, because the for- mer limits can be reached only when the reservoir is entirely empty, which will seldom occur in practice, and a failure at that time will affect only the structure itself, without menace to human life or to other property than the dam. Riveriftd FIG. 224. Cross-section of Masonry Dam, New Croton Dam, Cornell's. On the other hand the pressures on the toe reach their maxi- mum only when the reservoir is full, which is supposed to happen frequently, and failure under such circumstances would entail awful havoc, devastation, and loss of life. Such possibilities always -demand much higher factors of safety than cases where such vast risks of life and property are not involved. The primary reason for the requirement that the resultant of DESIGN OF GRAVITY DAMS 465 forces always fall within the middle third is the desirability of avoiding any tensile stresses in the masonry. This is far more important on the water face of the dam than on the down- stream face. If the resultant of forces, reservoir full, falls with- out the middle third, it tends to produce tension on the water face. This is extremely undesirable, as it tends to open cracks in the masonry at times when water under pressure is ready to enter such cracks and exert a pressure tending both to over- turn the dam and to cause sliding, at the time when failure would be most disastrous. At the same time the requirement in question gives us a margin of safety against overturning. The avoidance of tension on the water face of the dam or foundation is so important that the resultant of pressure, reser- voir full, should be kept sufficiently inside the middle third to amply cover any errors that can occur in the assumed weight of masonry, force of wind and waves, ice thrust, or extreme height of water in the reservoir. Should the resultant fall outside the middle third, reservoir empty, it will tend to produce tension on the downstream slope of the dam, which is theoretically undesirable, but not nearly so important as if it occurred on the other side, first, because there is no water to enter the masonry on the downstream slope, and second, because it occurs with reservoir empty, when there is no real danger of failure, and no life or property menaced thereby. On the other hand the tension that theoretically begins as the resultant passes from the middle to the outer third, is based on the assumption that the masonry is rigid and inelastic. Any elastic yield will tend to modify the theory, and slightly shift the point at which the tension begins. Moreover, well- built masonry will stand some tension and good practice some- times allows a tensile stress in concrete of 50 pounds per square inch. Standard specifications require a strength of 150 pounds per square inch at thirty days, for Portland cement mortar, and good cement will greatly increase this with further age. Any tendency of the resultant to fall outside of the middle third on the water side, reservoir empty, is necessarily accom- panied by greater vertical pressure at and near the water face, 466 MASONRY DAMS DESIGN OF GRAVITY DAMS 467 FIG. 226. Plan of Roosevelt Dam, Arizona. 468 MASONRY DAMS -158 feet- Scale of Feet 10 20 30 40 50 FIG. 227. Maximum Cross-section, Roosevelt Dam, Arizona. DESIGN OF ARCH DAMS 469 and this tends at all stages of the reservoir to close and keep closed possible horizontal openings, and thus to exclude water from the masonry. There is, of course, no danger of the dam overturning toward the reservoir when it is empty. It is thus seen that there is no valid objection to allowing the resultant of pressure, reservoir empty, to fall slightly out- side the middle third, so long as the actual pressures on masonry are kept within safe limits. 8. Design of Arch Dams. As pointed out on page 449 any masonry dam can be made more secure against sliding and overturning than it would otherwise be by building it on a curved plan, convex upstream. This makes it impossible for the dam to yield to the water pressure, without crushing the masonry or abutments, thus utilizing forces not brought into play by its resistance simply as a gravity structure. Navier's formula for computing water stresses on the vois- soirs of an arch is as follows: Where Q = the compressive stress upon any strip of unit width extending through the dam, at any given depth; P = horizontal pressure on unit surface at the same depth ; R = radius of the curve of the extrados of the arch. This value is based entirely on the assumption that all the pressure is sustained by the arch. It shows that the pressure is inversely as the length of the radius, and therefore the longer the radius the greater the pressure, and the thicker must be the dam section. As we shorten the radius we reduce the stresses and thus permit reduction of the thickness of the dam, but at the same time we have increased its length. Jorgenson has shown that the gain exceeds the loss in a decreasing amount until we have a radius equal to less than five-ninths of the width of the canyon at the dam site, shortly after which the balance gradually shifts the other way. This gives an arc of a little over 133 degrees. The theoretical advantage in using so long an arc, or in other 470 MASONRY DAMS FIG. 228. Pathfinder Dam, North Platte River, Wyoming. Lower face showing concrete ladder, and 6500 second-feet of water discharging from tunnel. DESIGN OF ARCH DAMS 471 472 MASONRY DAMS words, so short a radius over that of a somewhat longer radius is small, as the diminished thickness of the dam tends to diminish its resistance as a cantilever, and increase its susceptibility to vibration. In practice, therefore, it is desirable to make the included angle about 120 degrees if the physical conformation of the dam site is suitable. SECTION A-B SECTION C-D FIG. 230. Meer Allum Dam, India. Plan and Section of One Arch. All dam sites are wider at top than at bottom, and most of them have a shape somewhat resembling the letter V. It follows, therefore, that to obtain the greatest practical benefit from the arch action it becomes necessary to vary the radius from a very short one near the bottom, to a longer one at the top. This design of dam has been called the " variable radius " dam, or more often the " constant angle " dam, and has been patented by F. G. Baum & Company, of San Francisco, Cali- fornia. The Salmon River Dam near Juneau, Alaska, has been DESIGN OF ARCH DAMS 473 built on this principle, and to a less degree of exactness, the Lake Spaulding Dam on the South Yuba River in California. The most convenient and clearest expression is to state the curvature in terms of the radius, and this in terms of the width of the canyon, or in other words the chord of the angle. A rough rule for the change of curvature in an arch dam which secures the benefit of the variable principle and gives due weight to practical con- siderations, is to begin at the bottom with a radius of about three-quarters of the chord at that level, and change this radius gradually and uniformly i-. 20 '-- toward the top, ending at the FIG. 231. Cross-section of Bear top with a radius nearly five- Valley Dam, California. ninths the length of the chord at that level. This will vary the subtended angle from about 84 degrees at the bottom to about 120 degrees at the top. It will secure the benefit of cantilever action near the bottom where most important and FIG. 232. Plan and Elevation of Bear Valley Dam, California. avoid most of the practical difficulties of construction involved in a too rigid adherence to a constant angle. In many cases a dam site widens rapidly near the top, and becomes too wide to be closed by a dam acting as an arch, 474 MASONRY DAMS while the lower part of the site is well adapted to such an arch design. In such a case, it is often possible to build masonry abutments as gravity structures of moderate height, and thus --=^--891- r --SI 881 9 make a necessary span for the arch, of 400 or 500 feet, well- adapted to closure by an arch. The artificial abutments become simply tangential continuations of the arch. They are straight gravity dams, and receive endwise the thrust of the arch. MASONRY OVERFALL DAMS 475 9. Masonry Overfall Dams. Where it is intended that water shall flow over the top of a dam the prevailing practice is to give the top and lower slope a compound curve, such that the water in flowing over will everywhere rest upon masonry and not leave a vacuum behind the sheet of falling water, and so that the water will be guided into a horizontal direction as it leaves the dam. Where water falls, as in flowing over a dam a quantity of energy is generated, equal to the weight of the falling water El. 100.2' FIG. 234. Cross-section of New Holyoke Weir, Mass. multiplied by the height of the fall. This energy must some- how be dissipated in friction either in its own mass, or upon its channel. Different engineers hold different theories con- cerning the best method for preventing this energy from destroy- ing or injuring the dam. One method is to dissipate the energy as soon as possible at the time and place of its generation. To this end the water is made to fall as nearly vertically as possible upon steps or shelves of masonry on the lower side of the dam, and finally into a pool or water cushion at the toe of the dam, 476 MASONRY DAMS El. 1310 where the desired end is accomplished by impact and friction upon the masonry and upon the bottom and sides of the pool, and by the lashing and churning of the water in its own mass. It is caused to emerge quietly from the pool at moderate veloci- ties that will not erode the channel below. This method, of course, requires the best of massive construction to prevent damage at the points of impact and erosion, and it is usually necessary to protect the river banks for some . distance be- low, from erosion by the waves of the agitated water as it leaves the vicinity of the dam. The other method is to guide the water down the lower slope of the dam and gently deflect it to a hori- zontal direction, disturbing its velocity as little as pos- sible, and leading it as far as possible from the dam before much of its energy is dissipated. The object is to cause the water to expend its stored energy in over- coming the friction of the river ^bed at some distance from the dam, instead of on the dam itself. This method also requires protection of the river banks from erosion for a considerable distance below, unless they are naturally composed of good rock. Where this method is adopted, the water falling over the dam arrives at the toe with a very high velocity, which is that of a body falling through the same height under the action of gravity, minus the friction losses upon the dam and the air. If the vertical motion is changed by the curves of the masonry, very Katural ground * ,/,,;, rock Cll f,./] 1 rods, 3-o'long, grouted C L'lf WA J SECTION EJED ROCK ELEVATIONS 1275-1284 FIG. 235. Cross-section of Granite Reefs Weir, Salt River, Arizona. MASONRY OVERFALL DAMS 477 gently, to a horizontal direction, it will retain nearly the same velocity and flow away from the dam at that rate for a short distance, and suddenly, and with great commotion check its velocity, and increase its depth in proportion. This is called the " hydraulic jump." Where this change, and the correspond- ing commotion occurs, a great deal of work is done by the water upon its own mass and upon its channel, the work being sufficient to absorb the difference in energy between the velocity above and below the hydraulic jump. If the channel at this point is too soft or friable to resist this violent action, it must be well pro- tected, or measures must be adopted to check the velocity and dissipate the energy nearer the dam. This latter alternative FIG. 236. Cross-section of Norwich Water Power Company's Weir. was adopted at the spillway of the Gatun Dam on the Canal Zone, and at the Bassano overflow dam in Alberta, Canada. At Gatun, two rows of staggered rectangular baffle piers of concrete were placed near the toe of the dam to intercept the swift water, deflect parts of the stream upon other parts, and thus destroy the major portion of the energy stored in the swift water. The object was attained, but the -impact of the water upon the baffle piers was so destructive that it was nec- cessary to protect them with heavy cast-iron plates to receive the shock. This provision has accomplished the purpose. The Bassano Dam is equipped with two staggered rows of " baffle piers," shaped like snowplows pointed upstream, and designed to split up the high-velocity sheet of water before it 478 MASONRY DAMS can strike the bed of the stream, and throw one jet against another so that the energy will be ab- sorbed as much as possible by eddies within the body of the downstream pool, and not by tearing the foundations. The ^ baffle piers are not designed to destroy tf the energy by impact, '2 but to start eddies in concrete apron. Q ^ 10. Hollow Con- crete Dams. An in- KS troduction of com- I. paratively recent * years, is a variety of 8 hollow or cellular pU| dams, built of rein- forced concrete. These are develop- ments of the timber dams built with rather flat water slopes, so as to in- troduce a vertical component of water pressure, tending to give weight to the dam and hold it in place. The corresponding concrete HOLLOW CONCRETE DAMS 479 480 MASONRY DAMS type consists of a series of buttresses, supporting a sloping deck composed of reinforced concrete slabs. A modification of this This Furring Piece to to' 1,12 Ej 15 Ibs. with Back; SIDE ELEVATION FIG. 239. Steel Forms. McCall's Ferry Dam, Susquehanna River, Penn. type employs arches of plain concrete instead of reinforced slabs to close the gaps between buttresses. This is called the multiple arch type of dam. In favor of this type is the fact that FIG. 240. Cross-section of La Grange Dam, California. it does not require reinforcement, which in time might corrode, but this is met by the argument that in the case of the multiple arch dam, the failure of one arch would remove the support HOLLOW CONCRETE DAMS 481 1 482 MASONRY DAMS FIG. 242. East Park Reservoir Spillway, Orland Project. FIG. 243. Diversion Dam, East Park Feed Canal, Orland Project. HOLLOW CONCRETE DAMS 483 I 484 MASONRY DAMS .from its buttresses, and cause them to fail under the lateral thrust of the adjacent arches, thus causing the failure of all the arches in succession. This objection to the multiple arch type can be overcome in various ways. The most obvious way, and the one usually relied upon, is to build each arch so conservatively that it will not fail, and the side thrusts will balance. Another method is' to eliminate the side thrust. If each arch is made nearly a half circle, the buttresses can be each made to take the thrust of either arch independent of any support from the adjacent arch. A third method is to tie adjacent buttresses together at the springing of the arches, with beams to take either compression or tension, thus making each buttress sustain its neighbor. Jorgensen has shown that the angle of arch requiring the least quantity of concrete is 133^ degrees, but that one having a longer radius, and subtending only 120 degrees, contains for the same stresses only i per cent more concrete, but gives 6 per cent greater thickness. As this requires less forming, and less labor in placing, it is somewhat cheaper, besides offering greater resistance to percolation of water, and is therefore preferable. Similarly very short spans, with small buttresses close together, require theoretically less concrete than longer ones, but thin buttresses and arches, especially if high, are more likely to collapse, require more forming and labor in placing, and the arches are more likely to permit the passage of water. These practical reasons indicate spans of 40 to 50 feet, depending upon the height. With buttresses 40 feet from center to center, a radius for the upstream face of 23.1 feet will give an arc of about 120 degrees, and make economical construction. Cellular concrete dams of either type, if low, require much less cement than the ordinary gravity type. This advantage grows less as the height increases up to heights of about 120 feet, above which, owing to increased thickness of buttresses and arch rings and necessary bracing the advantage soon dis- appears. The cost of steel reinforcement if used, and of forms, tends to counter balance any advantage in cement, and each HOLLOW CONCRETE DAMS 485 case must be carefully considered in the light of local conditions. 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, is but n feet high and consists of a number of circular Expansion Joint Maximum high water El. 188.7 * Cut off wall 1 18" Wide, to be FIG. 245. East Park Multiple Arch Spillway, Orland Project, California. walls of 13! feet radius, convex upstream and sustained by concrete buttresses of 8 feet thickness, sloping downstream with gradient of ij to i. These walls (Fig. 245) are of reinforced concrete 18 inches thick, resting on a floor 12 inches thick, and below the walls and between the buttresses are subsidiary wails 2 feet high forming 486 MASONRY DAMS water-cushions. Downstream is a concrete apron 8 inches thick extending for a distance of 30 feet. An important advantage of any hollow type of dam is the fact that the pressures on foundation can be limited to a small FIG. .246. Cross-section of Iron Weir, Cohoes, N. Y. amount by spreading the base of the dam as desired and dis- tributing the pressure nearly equally over it. For this reason foundations of soft rock, clay, or shale can be utilized with a much higher factor of safety than possible with a gravity dam. Rods FIG. 247. Cross-section of Reinforced Concrete Weir, Theresa, N. Y. This possibility seems to have led to the careless preparation of foundations in some cases, and two failures of such dams have occurred, due to erosion of foundations bv water under STEEL DAMS 487 pressure, in regard to which the hollow dam has no advantage over the gravity type. Percolation under the dam must be prevented by a cut-off wall carried down to rock and also by grouting the seams of the rock if there is any probability of erosion by percolating waters under pressure. In short, the foundation should be prepared for a hollow dam very much as for a solid dam. ii. Steel Dams. Hollow or cellular dams, built first of wood, and later of concrete, may also be constructed of steel, and several dams of this type have been actually built. A sloping water-face is supported by a steel frame of standard shapes taking the water pressure mainly in compression. The water-face is a deck of steel plates, which, instead of being in the form of arches as in the multiple arch dam, or of beams as in the Ambursen type, are placed in the form of half -cylinders, concave upward toward the reservoir, so that the pressure of the water places the plates in tension. Such dams are comparatively cheap, and if properly pro- tected from corrosion should have long life. A steel dam on the Missouri River failed, and was replaced by a masonry structure, but the failure was of the foundation and not due to the type of dam employed. a. 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. 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 upstream face of the bents. The foundations of the steel bents are of Portland-cement concrete and the vertical posts rest on concrete walls (Fig. 248). There are 24 bents, each a right-angled triangle, with the inclined side having a slope of 45 degrees, facing upstream, the rocky bottom of the canyon forming the base. The dimensions 488 MASONRY DAMS 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 verti- cal 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 bed-plate as the vertical post. Bents Nos. 10, 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 bed-plate as the verti- cal post while above it are truss members connecting the face FIG. 248. Steel Dam, Ash Fork, Arizona. 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 20-inch 65-pound 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 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 connection- plates. STEEL DAMS 489 j I iliM:d i/<5 490 MASONRY DAMS 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 is composed of steel plates f inch thick and 8 feet lof 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 widths 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- pressure are well caulked. A weakness of the structure is that 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 seepage 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. 12. Foundations of Masonry Dams. The foundation of a masonry dam, especially a high dam, is an element of first importance. The structure should, if possible, rest upon rock, which must be of such hardness and strength as to resist the pressures to be applied. For dams not exceeding 50 feet in height, foundation of clay or gravel may be made to answer with proper cut-off provisions. If of clay, sand, or fine gravel, or any material into which piling can be driven, the weight should be carried on piles, providing a liberal coefficient of safety. The foundation must in any case be practically impervious, so as to allow no water to flow through under such pressure as to cause erosion, and so undermine the dam. The exclusion from the foundation of water under pressure is important, also, for another reason. If water can enter the foundation FOUNDATIONS OF MASONRY DAMS 491 from the reservoir, and has not free exit, it produces a hydro- static pressure under the dam tending to lift or float it, and unless large provision is made for this in the design, it may cause failure. We have already seen the importance of pre- venting tension in the masonry of the upstream face of the dam because of its tendency to admit water under pressure into the masonry, and thus produce uplift. The method of failure of masonry dams most common is by sliding on foundation. This has occurred in at least two notorious cases in America, accompanied by loss of life and property. These were both undoubtedly caused by uplift of water in the foundations. In each case the dam was founded on horizontally stratified rock, the bedding seams of which were filled with clay or other soft material with little cohesion, and serving as a lubricant when wet. Such foundation also affords maximum facilities for the entrance of water under the dam and the exercise of upward pressure upon the dam, thus neutralizing part of its weight, and inducing failure for lack of effective weight. The determination of the perviousness of natural formations is very difficult, as any examination which disturbs them changes the conditions it is desired to know. In general, it may be said that water will more readily traverse seams in rock or bedding planes than devious paths through the material of the rock. It follows that it will generally pass more readily and in larger volume in the direction of strati- fication, than in any other direction. Similarly stratified rock will permit percolation more easily and in greater volume than good massive rock, such as granite. Granular rock, such as sandstone, is likely to transmit more water through the rock itself than one of finer grain or denser structure, like shale or limestone. Meyer states (" Hydrology " page 264), that granitic rocks usually contain less than i per cent of voids, limestone i to 5 per cent, and sandstone 6 to 25 per cent. The percentages of voids in clay and shale are greater, but the grains and the voids between them are so small that water moves through them with extreme difficulty and slowness. 492 MASONRY DAMS No exact rules of this nature can be laid down, because there are many varieties of each kind of rock, with different percolating capacities. In general, however, the following rules may be taken as rough guides: 1. Massive or crystalline rocks such as granite gneiss and schists will transmit water less freely than sedimentary rocks. 2. Stratified rocks will transmit water more readily in the direction of stratification than transverse thereto. 3. In the direction normal to stratification, sandstone will generally transmit water more readily than limestone or shale. 4. Stratification on a plane approximately horizontal is the worst condition for introducing upward pressures beneath a dam. Conversely, the most favorable position in this respect for stratified rock is in nearly vertical beds. As all rock contains some seams, and nearly all rock is more or less pervious, it is unsafe to assume that any foundation is entirely impervious. It follows that in every masonry dam, some provision should be made to prevent or counteract upward pressure of water in the foundation. The amount of this force cannot possibly be foreseen with accuracy, and under ordinary circumstances cannot be foretold within rather wide limits. Any foundation for a masonry dam should be excavated to a plane below any surface disintegration. Where the founda- tion is seamy and pervious, a deep trench should be excavated along the heel of the dam to be later filled with rich concrete, thoroughly rammed and bonded with the masonry of the dam. In the bottom of this trench holes may be drilled to a depth of 50 feet or more below the bottom of the trench, and by forcing into these holes cement grout under high pressure, seams and cavities intercepted may be filled and sealed against percolating waters. The drilled holes should be placed at intervals of 5 to 20 feet or more according to the conditions of greater or less permeability found to exist. The attempt is to form an imper- meable curtain wall to a great depth, to prevent water from pass- ing from the reservoir under the dam. A short distance downstream from this cut-off curtain another series of holes or drainage wells should be provided EXPLORING FOUNDATION 493 to intercept whatever water may find its way into the founda- tion. These should be about 6 inches in diameter, and 8 to 10 feet apart, along the entire length of the dam. The wells should be continued upward in the masonry to a drainage gallery just above the natural ground surface, which will discharge any water received into a cross conduit leading to the open river below the dam. If the foundation is of very good granite, or other relatively impervious rock with few seams, the cut-off and grouting pre- cautions need not be as elaborate as those described, but the drainage system should be provided in any case of a high masonry dam, to insure against uplift in the foundation. 13. Exploring Foundation. Before deciding upon the suita- bility of any proposed dam site it is necessary to ascertain the character of the foundation and the depth and character of the bed rock. Where it is feasible to sink open shafts and test pits these are the most satisfactory means as they afford the opportunity of examining the material, in place, but they are expensive, and where water is to be encountered, may be impracticable or ineffective, and are very costly. Where the material passed through is to be used as the foundation of dam without removal so that its imperviousness is important, the material itself is not more important than the manner of its deposit, and test pits are the only satisfactory means of examining the material in place. Where the problem is the depth and character of bed rock, without much concern as to the character of the overlying material, the most economical procedure is to sink an iron casing to bed rock and take cores from the rock by means of the diamond drill. The process of sinking of the casing is performed by two general methods, called the method of driv- ing and the method of wash boring. In the driving method, the casing used is extra heavy steel pipe from 2 to 3 inches in diameter, cut to convenient lengths, which are fastened together by exterior sleeves. The bottom is shod by a short cutting bit of tool steel, and the top is provided with a solid head. 494 MASONRY DAMS This pipe is driven like a pile, and the interior is occasionally washed out with a chopping bit on a smaller pipe, provided with a water jet. When bed rock is reached the chopping bit is used and the pipe driven until some penetration of the rock is secured so as to make a tight connection between the casing and the rock, and thus exclude sand and gravel. The diamond drill is then applied operating inside the casing, and circular cores of the rock are secured. By the " wash-boring " method flush- joint pipe is used, which is not so strong, but sinks more readily than that with sleeve joints. The flush-joint pipe is not driven, but the chop- ping bit working inside is freely used with a strong water jet. The pipe is turned round and round by means of tongs, and sinks of its own weight or by weights resting on its top, following the hole made by the chopping bit which clears the way. This method is usually faster and cheaper than the driving method. When the diamond drill is used, it may pass through the rock into sand and thus demonstrate that a bowlder and not bed rock has been reached. In such a case a few sticks of dynamite are lowered into the hole drilled in the bowlder, and after with- drawing the casing a few feet to avoid injury the cartridge is exploded electrically, and thus the bowlder is shattered so that the casing may be sunk through it like gravel. The diamond drill should be made to penetrate the rock to a sufficient depth to be sure that it is bed rock and not a detached bowlder or fragment of rock, that is encountered, and if the rock is not of satisfactory character, the drilling should continue until better rock is reached, or the prospect of satis- factory rock disappears. Drilling machinery like that described is manufactured in such a way as to be adapted to operation by hand, and separable into parts capable of transportation by laborers or pack animals. Where much drilling is to be done it is usually more economical to use heavier machinery with steam motive power. Such a machine operated by hand is capable of drilling 200 feet into solid rock. It will make 5 to 10 feet per day in hard EXPLORING FOUNDATION 495 rock and more in soft rock. By the use of steam machinery much faster progress can be made. REFERENCES FOR CHAPTERS XVII AND XVIII CAIN, WM. Stresses in Masonry Dams. Trans. Am. Soc. C. E., vol. LXIV, p. 208, New York. THOMPSON, S. E. Impurities in Sand for Concrete. Trans Am. Soc. C. E., vol. 65, p. 250, New York. JORGENSEN, L. R. The Constant-angle Arch Dam. Trans. Am. Soc. C. E., vol. 78, p. 685, New York. CREAGER, W. P. Masonry Dams. John Wiley & Sons, New York. BLTGH, W. G. Dams and Weirs. American Technical Society, Chicago. HARRISON, C. L. Provision for Uplift and Ice Pressure in Designing Masonry Dams. Trans. Am. Soc. C. E., vol. 75, p. 142. RANDS, HAROLD A. Grouted Cut-off for the Estacado Dam. Trans. Am. Soc. C. E., vol. 78, p. 447, New York. WEGMANN, EDWARD. Design and Construction of Dams. John Wiley & Sons, New York. JORGENSEN, L. R. Arch Action in Arch Dams. Proceedings, Am. Soc. C. E., May, 1918. SCHEIDENHELM, F. W. Reconstruction of Stony River Dam. Trans. Am. Soc. C. E., vol. 81, p. 907. MEYER, A. F. Elements of Hydrology. John Wiley & Sons, New York. CHAPTER XIX WATER RIGHTS 1. Nature. The title to water is no less important than that to the land which is worthless without it. Water titles, however, rest upon different principles from those to land and personal property. 2. Riparian Doctrine. The English Common law, upon which our own laws are based, recognizes the riparian doctrine, which vests in the owner of the land abutting on a stream, the right to have the stream flow past his land in perpetuity, undiminished in quantity and unimpaired in quality. He may use the water for domestic and milling purposes, but must return to the stream before it leaves his property, practically the same quantity of water unpolluted; otherwise he infringes the rights of the proprietor of the land below him on the stream. This law was developed in England in a humid climate, and provided for the uses of water then and there common, but is not adapted to the development of irrigation, being antagonistic to the diversion and consumption of the water in the growing of crops. In consequence, the needs of irriga- tion give rise to a radically different set of rules for the control of water. All irrigated countries recognize the right to divert and consume the water in irrigation, and in fact, many streams flowing in arid regions are thus diverted and almost entirely consumed. 3. Doctrine of Appropriation. In the United States the right to the use of water in irrigation originates in Federal Laws - recognizing and authorizing such use.- Most of the land of the arid and semi-arid region was originally public land, and under the riparian doctrine the ownership of streams was 496 DOCTRINE OF APPROPRIATION 497 an accompaniment of the ownership of the land. The necessity of diverting these streams to irrigate the land was early recog- nized and was provided for specifically by the passage in 1877 of the Desert Land Act, which required the irrigation of the land as a condition of ownership. This law was a dedication of the water by its owner to the uses of irrigation, and thus made all unappropriated waters of the arid region perpetually subject to appropriation for irrigation, except when expressly forbidden as in the case of navigable streams. Exceptions to this rule are the cases of streams running through large Mexican land grants which never belonged to the United States, and the public lands of Texas, which belonged to the State under the provisions of the act admitting that State to the Union. Notwithstanding the Desert Land Act, and the need of irrigation, a number of the Public Land States have attempted to apply the riparian doctrine to the waters within their boundaries. This is particularly evident in those States which are partly arid and partly humid. The first American attempt to assert State control over the use of water in irrigation was a statute passed by the State of Colorado in 1879. This law was a crude one, making diversion the test of appropriation, and ignoring beneficial use. Adjudications under this law were made by courts of law, distant from the lands affected, and many absurd and extrav- agant claims were allowed. Many cases might be cited where allowances were made of over twenty times the quantity of water that could be beneficially used, and far in excess of the capacity of the ditches. The aggregate of allowances were many times as great as the flow of the stream in the irrigation season. The incompatibility of the riparian doctrine with the needs of irrigation was recognized in the early development of irriga- tion, and the eight States which are entirely arid or semi-arid have all abrogated this doctrine, and have substituted the reverse doctrine of appropriation of waters. These arid States are Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah and Wyoming. There are eight other States, however, 498 WATER RIGHTS which are partly arid and partly humid, where the riparian doctrine still prevails in the humid portion. Most of these States have the bulk of their population in the humid portion, where riparian rights are consistent with normal development, and where the inhabitants are unwilling to reverse their rules of property tenure and thus interfere with vested rights for the accommodation of a small minority or to encourage the develop- ment of a distant part of the State. In these cases the humid portion of the State was first settled, and as the needs of irriga- tion developed various attempts were made to reconcile the antagonistic riparian and appropriation theories. In two States, Washington and Kansas, the problem was attacked logically, by statutory action applying different rules to the arid and humid regions. In Washington the principle of appropriation was applied to Yakima County alone, where the main irrigation interests lay, and in Kansas it was applied only to the region west of the ggth meridian, which is the arid portion of the State. In California, Oregon, Texas, Nebraska, and South Dakota efforts were made to apply both doctrines and the result was a large volume of diverse and inconsistent court decisions, but mainly having a tendency to modify the riparian theory as derived from the common law in order to adapt it to the needs of irrigation. As an early step in this process, the right of appropriation was recognized in the owner of riparian lands, and he could apply the water to such area as he saw fit. Some decisions held that unless this right was exercised, it was liable to lapse, and another could appropriate and apply the water to beneficial use. Whatever the theory on which rights to the use of water in irrigation are founded, all of them recognize beneficial use as the indispensable condition of a permanent right; but this is a long and expensive process in most cases, and statutory protection is very desirable to protect invest- ments until it can be perfected. In the absence of statutory provisions, it is often the custom to initiate a water right by filing a notice at or near the point of diversion, and record this action in some county record. DOCTRINE OF APPROPRIATION 499 Such claims are often made to quantities of water far in excess of the total normal flow of the stream, and should be controlled by engineering authority on behalf of the State. Until recent years the title to irrigation water was in a very chaotic state, not only by reason of conflicting theories, but for the lack of definite statutory direction regarding the procedure to acquire and perfect a title to the use of water. In too many cases this has been left to the varying judgment of the courts and diversion and inconsistent rules and practices have been established. More recently, however, many of the States have adopted codes recognizing the right of appropriation, and have defined the legal steps necessary to thus initiate a right, which, however, remains inchoate until perfected by the application of the water to beneficial use. The insistence of all irrigation laws upon the application of water to beneficial use as a condition of title, constitutes a radical difference between water title and titles to land which may be perpetual and incontestable, without any pretense of using the land at all. Not only is beneficial use required, but the tendency is to make this requirement more and more stringent. A well established title to water may in most States be forfeited by abandonment, or by non-use for a specified time. In most cases, not only use, but a reasonably economical use is required. Although the quantity of water usually allowed by statute or by court decision is excessive, the prin- ciple is maintained that there can be no title to water to be wasted. Some of the constitutions of arid States assert that the waters belong to the public. This is a fundamental denial of riparian rights, but is always followed by provision for the appropriation of water to private use. As soon as this is accom- plished the assertion that the water belongs to the people becomes a fiction. Attempts are made to disguise this fiction by contend- ing that the private title is not a title to the water, but only a right to use. But as this right to use is perpetual, and in- volves the right to consume the water in irrigation, with no 500 WATER RIGHTS obligation to return it to the public nor to the stream, it is in reality an absolute title, limited only by the obligation to use it beneficially. 4. Appurtenance to Land. Aside from riparian rights there are two distinct theories of the ownership of water rights. One requires the appropriation of a specific quantity of water to a specified tract of land. When it is desired to detach a water right from the land to which it is appurtenant, it is neces- sary to give a statutory reason, comply with certain statutory formalities, and secure official permission, at the same time attaching the water to certain other lands, so that, under this theory no water right can exist except as appurtenant to certain land. The other theory permits the separate ownership of land and water, and thus the ownership of water is more nearly analagous to that of land than under the requirement of appurtenancy. Each of these forms of water right has its advantages and disadvantages. A separate owner of water may own no land whatever, and may lease the use of water to one land owner one year, and to another the next, so that conceivably some land may be left without water, and perennial crops may die, and the land may pass out of cultivation to the ruin of its owner. It is argued that this discourages permanent improvement; and while this is theoretically true, such results do not often follow in practice, as the delivery of water is limited by the location and capacity of the canal system, which cannot be conveniently changed. Permanent improvements and perennial crops such as fruit trees and alfalfa are abundant in Utah where separate ownership obtains. The possibility of the owner of water to deny its use on the land where it has been used, or by taking advantage of the farmer's needs to demand an exorbitant price, is to be avoided, and it is generally recognized that the doctrine of appurtenancy is the better public policy. On the other hand, when a given quantity of water is attached permanently to a certain tract of land, it often occurs that after some years the land does not require as much water as has been attached to it, and the tendency is to continue the APPURTENANCE TO LAND 501 excessive use of water to a 'disastrous extent; whereasj if the water right is owned separate from the land, although both titles may be and usually are in the same person, the owner has the incentive of self interest to spread it over all the land it will properly serve, to secure the maximum use, and thus to promote the economy of water, which is so desirable in an arid region. This objection to appurtenant water rights can be removed by laws and customs limiting the water right to the quantity actually required for economical use, and basing operation and maintenance charges on quantity used so as to put the onus of economy upon the user. This is becoming more and more the practice, and with this, and other wise provisions to secure economy there can be little doubt that the appurtenant water right is to be preferred. REFERENCES FOR CHAPTER XIX MEAD, ELWOOD. Irrigation Institutions. Macmillan Company, New York. CHANDLER, A. E. Elements of Western Water Law. Technical Publishing Co., San Francisco, Cal. JOHNSTON, C. T. Some Principles Relating to Administration of Streams. Trans. Am. Soc. C. E., vol. 78, p. 630, New York. LEWIS, JOHN H. State and National W T ater Laws. Trans. Am. Soc. C. E., vol. 76, p. 637. New York. CHAPTER XX OPERATION AND MAINTENANCE THE operation and maintenance of a system of irrigation canals and laterals is a highly specialized activity, involving different branches of skill for different systems. All of them, however, involve human as well as physical problems. Some of the most successful operators have become so by experience on some large systems, without special training in any other branch of engineering, but there are advantages in a general technical training which appear wherever new problems arise. i. Personnel. Every irrigation system of considerable size must have both office and field forces, under the general charge of a single responsible head. a. Manager. The Project Manager should be responsible for the safe and permanent maintenance of the system, and also for its efficient and economical operation. In addition to ability in many various lines, he must be well equipped with experience, judgment, industry and tact. If he is deficient in any of these qualities he will not be successful. He should have an assistant manager of his own selection and in close touch with him, who can act in his place during his absence, and to whom he can delegate many of the details of manage- ment. They should alternate to a certain extent between office work and field supervision, so that one of them may usually be found at headquarters, and both will be familiar with the business of the project, in field and office. b. Canal Superintendent. A large project is generally divided into districts each of which is in charge of a superin- tendent directly responsible to the Project Manager for the efficient delivery of water and the execution of maintenance 502 PERSONNEL 503 work. He is provided with equipment for rapid travel; and is assisted by such canal riders and gate tenders as may be neces- sary. The Superintendent should be provided with a telephone in his sleeping quarters, and be subject to call at all hours in case of a break in the canal, or other emergency requiring his attention. c. Canal Riders. Each canal rider should be assigned a definite portion of the canal and laterals for patrol, and for delivery of water therefrom to water users. He reports to the superintendent every day by letter the water deliveries, and promptly by telephone any urgent matters of business con- cerning the condition of the works and the needs of the water users of his district. The canal rider must be an intelligent man, should have some agricultural training, and be able to keep neat, accurate records. He must be energetic and vigilant and possess sufficient tact to enforce rigid regulations without unnecessary friction. He must be able and willing to perform arduous physical labor in case of a break or threatened break in the canal. Some construction experience is very valuable to him. The canal riders should usually be employed the year round, being engaged in cleaning and repair work and bringing the records into shape during the non-irrigation season. It is good practice to select these men from among the water users, but they should give their time to the duties of canal rider. Canal riders must be able to make accurate measurements of small streams, and to use intelligently all apparatus employed for this purpose. The canal rider should patrol his beat on horseback or with a small cart. A bicycle, automobile or motor cycle tends too much to distract his attention from the condition of the canal and its structures, which it is his peculiar duty to inspect. He should usually be provided with two horses to alternate on duty. d. Hydrographers. On large systems it may be advisable to have an assistant engineer skilled in all kinds of stream measurement, and in the installation and repair of apparatus for this purpose, to keep records of stream flow at points not 504 OPERATION AND MAINTENANCE immediately connected with any canal rider's beat, to inspect such observations throughout the project, and to digest the results. Particular attention should be given to the measure- ment of canals and laterals at points where the results will show seepage losses, and furnish data on which to plan improve- ments and repairs. e. Cooperation with Water Users. One of the most important duties of all, from Project Manager to Canal Rider, is to keep in sympathetic touch and cooperation with the water users. The first duty of the project management is to give good water service, and by vigilance and activity prevent or promptly repair breaks, and thus obviate interruptions. This will go far to secure public confidence, but is not alone sufficient. A patient hearing should be given all complaints, and careful investigations should be made with a view to the removal of all just grievances, however small. Suggestions for improvements will often be made, and these should be carefully considered, and if not practicable, the reasons for not adopting them should be clearly explained. The project personnel should show public spirit and concern for the common welfare, even along lines not strictly connected with the project management. In every community may be found broad-minded and experienced men whose cooperation along progressive lines it is possible to obtain, such as improved methods of irrigation, drainage, proper selec- tion and rotation of crops, road improvement, cooperative marketing and other measures for the common good. By such a policy it is possible gradually to secure the con- fidence and cooperation of the water users, and it is possible to accomplish far more by cooperation than by antagonism. 2. Economy of Water. The first duty of a project manager is to insure the protection and maintenance of the irrigation works. The second duty is to so operate them as to give reliable and efficient service to those entitled to their use. The third and most difficult, and consequently most often neglected duty he has to perform is to see that the water is economically used and not wasted. The average water user knowing that water is a valuable ECONOMY OF WATER 505 commodity is apt to regard it in the same light as he would regard money or any valuable commodity, and he feels the more he can get the better he is off, while in fact, however, from a strictly selfish standpoint, the reverse is more nearly true. The excess application of water is often positively harmful to the crops that receive it, which would produce better with less water. If the surplus drains away it carries with it plant food in solution and impoverishes the soil. If it does not drain away but remains in the water table it soon raises this water table until it curtails the root zone in which plants can feed and limits production in this way. If it continues to rise it eventually kills all useful vegetation, and this condition con- tinued forces to the surface whatever alkaline salts are contained in the soil and destroys its fertility. In addition to all the above reasons it is to the interest of the country at large and in a broad sense to each irrigator to make the best possible use of the water supply, which in most parts of the arid region is the limit upon agricultural development. The area of land available for irrigation, and nearly worthless without it, is far in excess of the water supply available there- for, except in a few restricted districts. The measures for securing the best use from the available water supply depend mainly upon the farmer himself, but such measures can be encouraged and promoted by the management not only by agitation and other educational methods but by methods of water delivery and the adjustment of rates of payment therefor. The encouragement of water conservation is hampered by the necessity which exists of using more water upon new land than upon land which by cultivation and the incorporation of humus therein has been reduced to a high state of tilth. This is due to the extreme dryness of new soil in the arid region, the absence of humus and the lack of that homogeneity or mel- lowness which follows from cultivation and mingling of organic matter in the soil. The presence of organic matter or humus renders the soil more retentive of water and less subject both to evaporation and to loss of water into the water table. 506 OPERATION AND MAINTENANCE Another reason even more important is the inexperience of the average irrigator. During the period of settlement when only a fraction of the land is in cultivation there is usually a large surplus of water available and this fact, together with the reasons above mentioned, make the practice universal of using more water on new lands than they really need, and a great deal more than they need at a later date. As cultivation proceeds all these conditions are changed. The farmer to succeed must put humus into the mineral soils characteristic of the arid region and must by irrigation and cultivation break up the stratification and induration of the various constituents of the soil, making it more homogeneous and mellow. The irrigator acquires experience with time, and the wider use of water reduces the redundant water supply to an amount just sufficient for economical irrigation with all the land in cultivation. But in the meantime habits have been formed. Each farmer who has not achieved maximum results is apt to attribute at least a part of his failure to a fancied insufficient supply of water at some time in the season, whereas in reality such shortage as he may have suffered has been due not to lack of water but to inadequate cultivation. It has been previously shown that soil kept in a thorough state of cultivation with the surface thoroughly pulverized at frequent intervals loses water much less rapidly than unculti- vated ground. At the same time the lack of cultivation permits the growth of noxious weeds which extract large amounts of water from the soil and thus in two ways the water supply is exhausted and the crops actually suffer from drouth even though the amount of water applied has been sufficient for their economical use under proper conditions. Thus the farmers are apt to resist any attempt to cut down the supply of water as furnished during the early stages of development and the opinion of the manager or any other expert who advises greater economy is apt to be denounced as the vaporings of swivel- chair theorists, as against the experience of the practical farmer. The result is generally a continued over- application of water with attendant rise of ground water and acute seepage con- ECONOMY OF WATER 507 ditions, calling for expensive drainage works in some regions, and a serious loss of plant food from the soils of other regions. One of the distressing results is that the farmer who uses water most lavishly may not perceptibly injure his land except from loss of plant food, which no one realizes, but the excess water he applies seeps to lower levels and waterlogs the lands of his neighbors who may be using water with a fair degree of economy. It thus often happens that it is difficult or impossible to induce those chiefly responsible for seepage conditions to join in the movement to correct them or tc provide drainage works neces- sary for the salvation of the lower lands. This creates a condition where the management is blamed on the one hand for shortage of water due to alleged inadequacy of the works to provide the lavish quantity used in the early days, and criticism of the builders of the project for the water- logged condition and a demand that they provide drainage works. The Project Manager must keep careful records of the water delivered and the acreage cultivated from the inception of the project, and also of the position and fluctuations of the water table, especially as this approaches the root zone of perennial plants. It is only by having complete records of this kind that the management can be equipped for the inevitable cam- paign of education, and the possible coercion that may be necessary to prevent the destruction of values in an irrigated valley. As soon as feasible the practice should be established by charging for water in proportion to the amount used. This practice is not so easily inaugurated as may appear on its face. In the first place it requires careful measurement of water thus irrigated, which involves considerable investment in meas- uring devices, and considerable skill and labor on the part of the operating force. The cost of this may be criticized by the water users to whom it is charged, and their resistance has prevented proper administration in many cases. The full application of the principle without modification places a premium upon the non-use of water and consequently 508 OPERATION AND MAINTENANCE upon the non-cultivation of the land which is the reverse of what is desired. On the other hand a project just being opened and having sandy soil with a porous subsoil may be difficult to irrigate without applying an excess quantity of water at very frequent intervals while other lands perhaps even more productive owing to different soil conditions may be served with a fraction of the quantity of water necessary on the sandy lands. If a uniform charge for water by quantity is established it may happen that in order to collect a sufficient sum for the operation and maintenance of the project, the price must be fixed so high as to be oppressive or prohibitive upon the owners of the sandy lands and thus more harm than good might proceed from such a rule. For these reasons much care and judgment must be exercised in fixing the rates to encourage economy of water and penalize its waste, without restricting cultivation or oppressing those who are unfortunately situated regarding topographic and soil conditions. It is obvious, therefore, that every individual project presents a problem or series of problems all its own which must be met and solved upon their merits. The correctness of the principles here advocated are recog- nized and provided for in the United States laws applying to the United States reclamation projects. Section 5 of the Act approved August 13, 1914, provides as follows: " That in addition to the construction charge, every water-right applicant, entryman, or landowner under or upon a reclamation project shall also pay, whenever water service is available for the irrigation of his land, an opera- tion and maintenance charge based upon the total cost of operation and maintenance of the project, or each separate unit thereof, and such charge shall be made for each acre- foot of water delivered; but each acre of irrigable land, whether irrigated or not, shall be charged with a minimum operation and maintenance charge based upon the charge for delivery of not less than one acre-foot of water." This while establishing a principle, leaves wide discretion in the executive officers in applying the principle. To start with, ECONOMY OF WATER 509 physical conditions make it necessary to collect a different total amount and different amount per acre upon each system in order to pay the cost cf operation and upkeep. Different systems and different parts of the same system require different quantities of water for proper irrigation due to soil and climatic and other conditions, and this necessitates a different rate in order to raise a given amount of money. Another important consideration not yet mentioned is the necessity of bringing some pressure to bear upon the irrigators to accommodate each other and meet the demands of the system concerning the time of application of the water. Where the charge is made by quantity there is a general tendency to post- pone irrigation in the hope of rainfall or cool weather by which a little water would be saved, then a hot spell may cause wilting of the crops and everybody rushes at once to the management for immediate delivery of water. As no system can be econom- ically constructed adequate to irrigate all the land at once, it becomes impossible to fulfill all these requests on demand, and inevitably some crops must go short of water during the criti- cal time, and heavy losses may ensue. To avoid this the carry- ing system is overtaxed and the overloaded canals, attended by an overworked operating force, are apt to give way at the critical time and cause widespread destruction both to the lands devastated by the broken canals and to those that need the water thus suddenly shut off. It thus becomes necessary to make rules by which a farmer must give several days' notice of his needs so that these needs can be adjusted to the carrying capacity available, and the tendency to concentrate the requests all at the same time must in some cases be counteracted by an adjustment of charges. It is therefore advisable in many cases to charge more for water during the peak of the season than at other times in order to induce earlier use of water and prevent overtaxing the system as above described. Experiments have shown that a limited quantity of water delivered to growing plants during the earlier stages of growth yields better returns than the same quantity of water applied 510 OPERATION AND MAINTENANCE at a later date. Furthermore, water applied early in the season is available for plant use throughout the season so long as it is within the root zone, while late irrigation often leaves the root zone charged with water after growth has ceased and the water is thus wasted, and perhaps contributes to raise the water table. Still another reason is very important. Most projects are supplied by streams which yield a super-abundance at certain seasons, and decline to small dimensions at other seasons and must be supplemented by expensive storage works. To get the full value of the investment in storage works the requirements of economy are much greater during the season when stored water must be used than during the season of abundance when water may be running to waste. In most regions the spring and early summer is the season of abundance, and streams decline in July reaching a very small flow in August and Septem- ber. In order to induce early irrigation and better conserve the storage supply it may be advisable to adjust the charges so as to encourage early use of water and penalize excessive application of storage water later in the season. The law above quoted has been found adaptable to all of these varied requirements and the result is a wide variety of terms and rates, applied to the different projects and even different parts of the same project. In order to avoid penaliz- ing the use of water it is customary to make a flat rate which shall apply to all the land whether water is used or not and which when paid will entitle the landowner to a quantity of water which is sufficient for economical irrigation under the most favorable circumstances. This secures the collection of a cer- tain amount of money from every acre and thus insures the recovery of most of the cost of operation and maintenance. A moderate charge for additional water will make it to the interest of every man to use water with economy. This charge should be moderate until the limit is reached beyond which any applica- tion is unquestionably wasted; thereafter, the charge should increase rapidly and finally become burdensome so as to prop- erly penalize the prodigal waste of water. On the pumping tract of the Minidoka Project, Idaho, WANTON WASTE 511 where it is necessary to prevent a sudden demand from exceeding the capacity of the pumps in the peak of the season, the price of water is fixed, at 50 cents per acre-foot for deliveries on or before June 5, and at $1.00 per acre-foot after that date. The high price is continued after midsummer on account of the use of expensive stored water in the late summer and fall. A minimum charge, however, of Si. 50 is made against each irrigable acre whether water is used thereon or not, and this charge is credited on payments for water under the acre-foot rates. From long investigations and study of results in Utah, Dr. Widtsoe, President of the Utah Agricultural College, concludes: " The Utah results would lead to the belief that where the annual rainfall is from 12 to 15 inches, a depth of water from 10 to 20 inches is best for ordinary farm crops, and that the best quantity lies nearer the smaller figure. A depth of 12 inches probably represents the average requirement of ordinary farm crops, providing the water is measured at the intake to the farm." 3. Wanton Waste. First of all, rules must be rigidly enforced forbidding wanton waste of water, such as allowing it to run at night without benefit, on account of the inconvenience of night work, allowing it to waste in large quantities from the lower end of the field, into the roads or waste ditches, and other similar practices. a. Irrigation at Night. In the early development of some valleys, while irrigation uses are small and the water supply abundant, the practice grows up of irrigating during daylight and at dusk turning the water into some draw or slough, and allowing it to run to waste until the irrigator is ready to resume irrigation the following day. In this way from a third to half of the water is wasted, and perhaps contributes to raise the water table and aggravate the need for drainage, which is almost certain later to become acute. This practice may be hard to break, and attempts to do so should be preceded by courteous explanations of the necessity for the reform. It is, however, necessary finally to do this, and all communities where good 512 OPERATION AND MAINTENANCE results are obtained with a reasonable quantity of water, give the same attention to the control of water at night that they give it by day. 4. Rotation. In some regions, especially in the early stages of development, it is the practice to deliver a constant flow of the average quantity to which the irrigator is entitled, and where water is abundant this delivery is often greatly in excess of the needs. As the owner of a small farm cannot give his entire time to applying irrigation water but must attend to other duties, it is obviously not practicable to use water economically in this way. Much better results can be had, higher economy attained and much time saved by delivering water at intervals in larger volumes. This practice also promotes important economies for other reasons as when a small quantity of water is turned on at the upper end of the field it is absorbed by the land first reached and progresses very slowly to the lower end, and before a sufficient quantity has reached the lower end of the field for proper irrigation a great deal of the upper end of the field has become over-saturated and water is flowing by gravity into the subsoil, finally to reach the water table and be wasted. Much higher economy both in time and water can be obtained by turn- ing on a large quantity at once so as to cover the ground several inches in depth and while the water in contact with the soil is being absorbed the surface water is run rapidly toward the lower end of the field. The entire surface is thus soon wet and the irrigation of a given district is soon over and the water is carried to additional fields. If a farm of 100 acres is entitled to an average flow of i cubic foot per second, it is best to commute it into a flow of 5 to 10 cubic feet per second, deliver for one-fifth or one- tenth of the time; then by giving careful attention to the use of the water, irrigation is accomplished better and the irrigator has a major portion of his time for other duties, and while engaged upon them his neighbors are using water in a similar manner. Such a system requires turnouts, laterals and farm ditches constructed with rotation methods in view and these should be provided in the construction of an irrigation system. ROTATION 513 It is necessary to use much larger heads for irrigation on very sandy soils where percolation is rapid than upon tight soils which require a great deal of time to absorb the requisite amount of water. It is also practicable to use much larger heads on comparatively level ground than upon steep slopes, and next to the skill of the irrigator, the grade of the land to be irrigated is the most important element in the limit of head which it is practicable to use. The introduction of such a rotation system is a matter of considerable difficulty and it will be difficult to overcome the established habits and prejudices. The rotation method of delivery of water is employed on the Okanogan System in Washington, the system being to allow a water user for one week double the amount of water which would be required for constant flow, and then one week without any water delivery. This schedule is worked out before the irrigation season begins and each water, user is notified of the dates on which he will receive water. The schedule is adhered to as nearly as possible, but numerous modifications have to be made to accommodate the irrigators. The system as worked has been found reasonably economical of water and of labor, and is satisfactory to the water users. The lateral system on the Salt River Valley, Arizona, was so designed as to deliver to each quarter section of land a head of 10 second-feet of water. For many years the custom was followed of delivering such head for a period of twenty-four hours in every eight-day period, seven days without water, and for smaller farms, a proportionately shorter time, with the same interval. In 1912 the basis of charge was changed from, the flat rate to payment for quantity of water used in order to encourage economy, and the rigid rotation system was varied, water being delivered in large heads, but instead of a regular rotation, deliveries are made in accordance with requests which are required to be presented twenty-four hours or more in advance of the need. From these requests, rotation schedules are made 514 OPERATION AND MAINTENANCE up from day to day as far in advance as possible, and in most cases, it is feasible to deliver water in accordance with the requests made. During the maximum demand for water, these requests frequently conflict to such an extent as to make their compliance impossible, and notice is served that the water will be de- livered on a rotation system. When a lateral is on a rotation basis, it is the custom to begin at the lower end and work up to the head of the lateral, giving to every water user a head from yj to 10 second-feet for from twenty-four to thirty-six hours for each quarter section of land. Generally when the demand for water at any partic- ular time has been greater than the capacity of the canal to supply, it is necessary only to advise the farmers that the canal will be placed on a regular rotation basis and the demand immediately decreases, the farmer being willing to wait a few days for water rather than have the canal placed on regular rotation. The delivery head, however, is the same for both plans of delivery, and the method followed on the Salt River Project is very economical, both of time and of water. Most of the irrigation in Salt River Valley is done under the border method described on page 112. Regardless of crops raised, the border system is the best method of irrigating porous soils, unless the ground is too steep for this method. On very rolling land, so steep that the flood- ing or border method is not practicable as a means of distribut- ing water the furrow system is generally used. The furrows may be run on any grade desired between the steepest, directly down the hill, and a level line along contours. The more open the soil the steeper must be the slope of the furrows. This may range from about 2 per cent on open sandy soil where the water must be hurried across the field, to about one- tenth of this slope, or 2 feet per thousand for loam or clay soils where more time for absorption must be given. 5. Basis of Charges. It is becoming more and more the practice to fix charges for operation and maintenance in accord- CULTIVATION 515 ance with the quantity of water used, and to encourage economy by this means. To insure the collection of sufficient revenue for expenses, and also to compel those who do not cultivate their holdings to pay a proper share of expenses, it is best to establish a flat rate of charge per acre, which will entitle the irrigator to about the quantity of water necessary for economical irrigation, and then fix a reasonable charge for all additional water used. This has a tendency to encourage proper use of water and to penalize waste, but accomplishes little, unless accompanied by a system of rotation delivery, and careful night irrigation. The variety of human and physical con- ditions lead to widely various application of the above rules for charges. The projects vary widely in many respects. Some are expensive to operate in proportion to the acreage served and some are cheap. Some have an abundant water supply, and on others, the supply must be stretched to the utmost. Some have stored water, while others depend on natural stream flow. On some delivery capacities are rigidly limited by pumps, expensive tunnels, or similar works, while simpler projects are more generously endowed in this respect. Some have a rea- sonably uniform soil, while on others the soil ranges from heavy clay to coarse sand with gravel subsoil. Some have a growing season of 4 or 5 months while others range from 6 to 12. Some lands require but a small quantity of water for good results, while others require several times as much. These varying characteristics occur in all conceivable com- binations, and each project presents a distinct problem which must be considered by itself, and changes from year to year, as development progresses. The provisions applying the above law are given in Table XXIV, page 145. 6. Cultivation. Experiments have shown that a vigorous growing crop transpires more water to the atmosphere than is evaporated from the surface shaded by such a crop, but the evaporation from the ground still remains very important unless it is assiduously cultivated. After each irrigation there is a tendency for the surface of the ground to bake under the 516 OPERATION AND MAINTENANCE hot sun, except on very sandy soils. When this occurs, capil- lary attraction is very strong, and the water is rapidly drawn to the surface and evaporated. This can be remedied by thoroughly stirring the surface of the soil breaking the crust and providing a mulch of pulverized loose soil, which holds the moisture and reduces evaporation to one-half or one-third what it would be without such cultivation. This also kills the weeds and conserves plant food, by keeping the water in the ground a long time before taken up by the plants thus giving it time to dissolve the minerals of the soil which serve as food for the plants. Fresh water applied to a field can convey but little nourishment to the plants, especially of the mineral character, and for this reason it is much better to conserve water in the soil for a long time than to allow it to evaporate rapidly and irrigate with fresh water. It is impor- tant, therefore, to cultivate soon after irrigation as the surface is sufficiently dry for the purpose, and it is necessary for constant effort to be put forth to induce the farmers to do so. 7. Winter Operation of Irrigation Canals. In semi-tropical regions it is usually necessary to operate irrigation canals the year round and it then becomes at times difficult to secure enough respite to afford opportunity for necessary cleaning and repairs. This must usually be obtained in short periods in the winter season between crops or immediately after rains. In the extreme North the long severe winters make winter operation not only practically impossible but relatively unde- sirable; in middle latitudes, however, where six months of the year are frosty and irrigation is not required, it may be neces- sary, and on new projects usually is desirable, to have water available for domestic and stock use and the demand for this use is sometimes very insistent. Arguments are also advanced that winter irrigation is beneficial and is necessary also for sprouting of winter grain crops and the moistening of land for winter plowing. The operation of canals through months of freezing weather is open to many objections: i. It delays or prevents adequate cleaning and maintenance WINTER OPERATION OF IRRIGATION CANALS 517 work and therefore cripples the efficiency of the canals for their real purpose of summer irrigation. 2. Water held continuously in canals results in serious deterioration of the banks which, becoming saturated, freeze and by the expansion of the ice leave the banks more or less open and porous, increasing the dangers of seepage and sloughing. 3. It increases the leakage of the canals by extending this through the winter and thus results in increased seepage and rise of water table, tending to destroy the agriculture of lands under the canal or to add to the cost of drainage. 4. Irrigation works are not designed with a view to operation under frost conditions, and the effect of freezing upon concrete structures often causes rapid deterioration. 5. Irrigation canals do not ordinarily furnish water supply suitable for domestic purposes and their unavoidable contami- nation renders the water unsanitary and dangerous. 6. Live stock is much better off in winter when supplied with clean and wholesome well water at underground tempera- ture, which conserves animal heat and health and saves much feed. It is best, therefore, to provide supplies of well water for stock and domestic purposes as soon as practicable. Experience shows that after the first year or two most of the settlers provide themselves with domestic water supply of better quality than canal water if this is at all feasible, and the demand for winter operation is usually by a small minority of the settlers. But even where this is not so the financial and sanitary considera- tions involved are strongly on the side of closing the canals as early as possible in the autumn, thus giving plenty of open weather for cleaning and repairs and letting the banks dry out before the hard freezing weather arrives. The canals are then in shape to secure satisfactory results when opened in the spring. This policy also has usually a beneficial effect on the ground water conditions, as the contribution of water from the canals is thus shut off. In some localities, where the water table is already high near the canals, they operate as drains for a time 518 OPERATION AND MAINTENANCE after the water is shut out in the fall, and thus hasten the lowering of ground water which occurs during the non-irrigation season. Where winter delivery is necessary the burden of operation cost should be borne by those who demand it, and deliveries made only to those who share the expense. This problem is met on one of the Government systems by the following regulation : a. Optional Water Service. Until further notice, after October 20 of each season no water will be furnished except upon request, and at an additional charge for each farm-unit of eighty acres or fraction thereof, of $2.00 for each day of water service given. Provided, however, that every person desiring this service shall, before receiving same, deposit with the Special Fiscal Agent of the United States, a sum of money sufficient to cover the number of days that he desires water and designate the turnout where he wishes to have the water delivered and the size of stream he will require. So far as may be practicable, water will be delivered to each depositor for the days covered by his deposit, but whenever the aggregate deposits for any day are less than $200, delivery of water will cease and will not thereafter be resumed. Any unused deposits will be returned to the persons by whom they were made. This service will not be commenced, however, unless deposits aggregating $200 per day for a reasonable period shall be made prior to October 20. 8. Maintenance. An efficient rotation system will give occasional opportunities during the irrigable season for necessary cleaning and repair work on small laterals, and the opportunity to perform this work when most convenient or economical is an important advantage of such a system. This, however, can- not apply to the main canal, nor to the larger laterals, which must be used throughout the summer. In Southern Arizona and California the demand for irrigation water throughout the year presents a difficult problem in maintenance and repairs, and great care and energy are essential to perform these neces- sary duties properly, without seriously interfering with proper irrigation. The demand for water is much less in winter than EROSION 519 in summer, and a brief shortage produces less disastrous results. Such work as can be done with water running in the canals, is so performed, and the rest is, if possible, postponed till the fall or winter months. By closing one large lateral at a time after due notice to the irrigators, concentrating a large force there and pushing the work, the annual maintenance work may usually be performed on these with little inconvenience to any- one. The main canal is treated in the same way, selecting for this the period of least demand for water, usually in January. In more northern latitudes with shorter season, the water should be turned out of the canals after ample notice to every- body, as early in the fall as conditions will permit, and a strong force previously organized should immediately be set to work to perform the annual maintenance work. A careful inspection of the canal and all structures should be made, and their con- dition recorded for present and future use. 9. Erosion. Where erosion of one bank is noted, this should be attended to. If it is due to some obstruction on the other side of the canal as a sand bar or other drift this should be removed. If the erosion is on the outside of a curve in the canal this may be corrected by deepening the canal on the inner side of the curve, to induce a stronger current on that side, and using the material removed to flatten the slope on the opposite side. If gravel can be obtained a carpet of this may be placed on banks showing moderate erosion. In case of necessity the points attacked may be protected by riprap of rock, or in some cases sage brush had better be employed. Rock riprap has been much used, but is always costly and is not efficient unless laid in a very expensive manner. Unless the riprap is started below the canal bottom and the joints well plastered, it soon fails in sandy soil by the washing out of the sand between the cracks. Brush of any kind, weeds and grass will do temporarily, but the latter are good for but one season. Sage-brush is especially adapted to this purpose, being bushy, flexible, durable and tough. A method extensively used is to plow a deep furrow in the bank about a foot below where the damage is likely to occur 520 OPERATION AND MAINTENANCE and smooth this out with a small V-shaped scraper which leaves a terrace about i\ feet wide. On this a layer of brush is placed with butts to the bank and tops sloping toward the water and downstream 30 to 40 degrees, the tops being kept in careful alinement. After the first row has been laid, another furrow is plowed higher up the bank and smoothed out with a scraper, pushing the dirt over the first layer and effectively binding it without the use of stakes. This process is repeated until the riprap is a foot above the maximum water surface. When finished, the tops of the brush should extend 8 inches beyond the earth they are buried in, but must not encroach upon the original canal section. The distance vertically between layers of brush and the den- sity of each layer should vary with the velocity of the water. For velocities below 3 feet per second, the density of the riprap may be about equal to that of the branches in the average sage- brush, and this should increase with higher velocities. On the Minidoka Project a large amount of such riprapping was done at costs varying from 10 to 14 cents per square yard. 10. Silt Deposits. Accumulations of sand or silt should be removed and their cause noted. If it is due to some local obstruction producing an eddy or other removable cause, this should be corrected. Dead weeds drifting into the canal should be removed and burned. Weeds, brush and grass growing in or very near the waterway will obstruct the flow and cause deposits of silt, and should be removed. If this is done cleanly annually or oftener it will be less expensive than if postponed until the nuisance becomes acute. Where excessive seepage has occurred it may be advisable to excavate the channel larger and refill with clay puddle. This method is described on page 233. Where the water carried is heavily silt-laden, extensive deposits of silt may occur through- out the canal system, and must be removed by mechanical means. This is done from small canals in the southwestern valleys where this problem occurs, by means of a V-shaped drag or plow with a cutting edge, pulled by one or more traction ALKALI 521 engines. It is necessary for the V to travel down each side, and it is not applicable to canals of more than 10 feet bottom width nor 4 feet depth. Larger canals may be cleaned of silt by dredges traveling on the banks, or floating on barges. The drag line type is best adapted to this use. 11. Alkali. In some regions concrete is attacked and slowly disintegrated by alkali, usually sulphates. The damage is generally caused by alkaline ground water, which is absorbed by the concrete, whence the water evaporates leaving the salts to crystallize in the body of the concrete, and disintegration follows, apparently as a mechanical result. The structures usually attacked are those in contact with the ground on one side, and with the air on the other, such as culverts, and canal linings while not covered by canal water. A structure standing in alkaline ground may absorb ground water, which by capillary attraction percolates upward, and evaporates from the surface above ground, and disintegration begins just above the ground, and extends as high as the ground water rises. The preventive most often attempted is to make the concrete as dense as pos- sible by careful mixing and placing, so as to reduce its absorp- tion to a minimum. It may be that a coating of tar or other waterproof material can be placed on the side next the ground water, and this may prevent attack. Another method, applicable to canal lining and some other cases, is to drain the ground water from the vicinity of the concrete by a layer of screened gravel, leading to some escape. 12. Growth of Aquatic Plants. Where clear water is run in earth canals, especially at a low velocity, the growth of aquatic plants sometimes reaches a profusion that gives serious trouble. There are several species of these plants some of which have long stems, and by friction upon the flowing water, impede the velocity and thus cut down the capacity of the canal until it often becomes imperative to remove the vegetation in order to restore sufficient capacity for the needs of the crops. Such growths seldom become troublesome when the water is continuously turbid, nor under bridges where the shade is dense. They are more troublesome in shallow than in deep canals, 522 OPERATION AND MAINTENANCE and do not thrive generally, in water more than 4 or . 5 feet in depth. They need sunlight and heat, and seldom bother when temperatures of water are kept below 65 degrees. They are especially troublesome in canals of low velocity, although when other conditions are favorable, they occur in canals with velocity as high as 2j feet per second. The experience of the U. S. Reclamation Service indicates that the velocity should be at least 2\ feet per second to insure against troublesome growth of aquatic plants. Etcheverry concludes from study of all available data that instances of troublesome growths in velocities above 2 feet per second are few and practically none for velocities greater than 2 J feet per second. Numerous methods of combating these pests have been tried from time to time, with various degrees of success. Where the climate is especially hot and dry the plants are sometimes killed by shutting the headgates and allowing the water to drain out of the canals and laterals affected, which dries the plants and kills them in from two to five days under favorable conditions. This will not work, however, where the grade of the canals is slight as the water is then held by the plants as a sponge, and does not drain sufficiently to kill the plants in a reasonable time, but where the grade and velocity are ample and the humidity low it has been known to succeed. It seems to be more effective with some species than with others. Aquatic plants do not grow to a harmful extent in muddy water, and where the conditions are favorable benefit may be derived from an application of the silting process, so as to keep the water muddy for several weeks. To be effective, this remedy must be applied before the plants have reached any considerable size and vigor, and should be continued until its effect is complete. Where neither of these means can be successfully used, the plants may be removed by mechanical means. Several devices have been tried for this purpose. A small chain to which are attached lead weights has been dragged along the bottom of the canal by a team on each bank GROWTH OF AQUATIC PLANTS 523 attached to the ends of the chain. Little success has followed such efforts, as the chain slides over much of the vegetation without killing it. A springtooth harrow is rather effective in small laterals where the water is not over a foot deep, but has to be frequently cleaned, and is a failure in larger canals. Brush scythes wielded by hand can also be successfully employed in small laterals. The most effective weapon in large canals is the submarine saw, which consists of a flexible steel tape with teeth on both edges, and is pulled back and forth across the bottom of the canal by a man on each bank. It has lead weights to hold it against the bottom, and a rope handle is attached to each end. The work of sawing progresses against the current of course, the saw is operated at an angle of about 30 degrees to the cross- section of the canal, and the pull toward the upstream end does the cutting. The vegetation when cut rises to the top of the water and floats downstream, where it is taken out at the first bridge by one or two men with pitchforks. One crew can pro- gress at the rate of from 1000 to 5000 feet per day. The cut- ting is effective at the time, but does not injure the roots, which often send up new shoots which grow rapidly and it may be necessary to repeat the process two or three times in a season. This method is not effective unless there is enough current in the canal to hold the plants firmly against the saw. Where the canal is free from stones and gravel good results may generally be obtained by the use of the Acme harrow, or orchard cultivator, a machine consisting of long parallel blades attached to and following an iron frame, with the sharp edges of the blades turned to a horizontal position. It cuts the roots just below the surface of the ground, and the plants float to the top of the water and pass downstream to the first structure where they are removed with pitchforks. The cultivator is drawn by means of long chains, by a team on each bank of the canal. By adjusting the length of the chains the machine can be made to work on either side or bottom, of the canal. Results are obtained much cheaper with this method than with the saw. Where there is a tendency to silting this machine 524 OPERATION AND MAINTENANCE stirs up the silt which is then carried along and deposited upon the land, while the muddy water tends to retard the growth of the aquatic plants, and helps to puddle leaky stretches of the canal. Where conditions permit, canal velocities of 2\ feet per second and over should be provided, and if grades sufficient for this cannot be secured, it may be advisable to provide a canal depth of 5 feet or more, remembering that the narrow deep canal will have a higher velocity on a light grade than a shallower one, and that both velocity and depth tend to pre- vent trouble with aquatic plants. The narrow deep canal having a higher velocity for a given grade, and deeper water for a given capacity, presents for both these reasons greater security against the growth of algae or other aquatic plants. 13. Wind Erosion. New canal banks built of sand or other light soil in a windy country are often attacked by wind, and may be gradually destroyed unless protected in time. It may be necessary to provide a blanket of gravel or clay if these are obtainable, but this may be too expensive, and in any case it is desirable to clothe them in vegetation, and this should be undertaken as soon as possible in order to forestall wind erosion. The natural vegetation, the climate and the soil involved should be carefully studied and in many cases it may be advisable to sow seeds of plants that will grow under the adverse con- ditions, and yet not become a nuisance. In most parts of the West, the Russian thistle appears spontaneously after a time, unless the climate is too dry and hot. This plant protects the soil from wind erosion, wherever it thrives, but becomes itself a nuisance in the fall, by breaking off at the ground and blowing across country as a tumble weed, lodging against structures, clogging turnouts and even obstructing the canal itself. A pile of these weeds becoming waterlogged in the canal will sometimes collect silt and other drift, thus forming bars which reduce the capacity of the canal, and perhaps divert the current against the opposite bank, and ' start erosion. Nevertheless even this thistle is often a welcome assistant against wind erosion, on account of its persistence where nothing else will NOXIOUS PLANTS 525 grow. Rye is sometimes sown, furnishing valuable protection, and reproducing itself under rather unfavorable conditions. It has the important virtue of never becoming a nuisance. Care should be taken to avoid semi-aquatic vegetation such as willows and various water-loving grasses, which will encroach upon the water section of the canal, collect sediment and gradu- ally reduce the capacity of the canal. Some of these plants are very difficult to check and control when once started, and are most apt to give serious trouble in canals of low velocity. 14. Noxious Plants. It is not always possible to draw a definite line between plants which are helpful and those which do more harm than good. In general the control of weeds on the canal banks is a serious matter, and a constant expense in maintaining the canals at their required capacity. Various methods of fighting weeds and grasses on the canal banks are employed, such as mowing them frequently, cutting below the ground surface with hoes or shovels, and sometimes where the problem is most difficult sheep and goats are success- fully employed by confining them on the canal banks with fences. They must be furnished in sufficient numbers so that they will be constantly hungry and keep all the weeds cropped close to the ground, otherwise they will choose those they like best, and let others grow. This method has been successfully employed in Southern Arizona, New Mexico and Texas in controlling Johnson grass, willows, and other persistent weeds. 15. Burrowing Animals. The maintenance of a canal system is a perpetual warfare between the manager and a horde of burrowing animals, such as gophers, ground squirrels and muskrats. The newly built banks offer favorite locations for their holes, and where one emerges on the canal side below the water line the water follows it and quickly- enlarges the hole until it becomes a break carrying all the water of the canal, and sometimes causing great damage not only to the canal, but to the irrigated crops and to the land itself. One of the most important of the duties of the canal rider is to scrutinize the banks for signs of burrowing animals and when found, place grain, raisins, or other food thoroughly soaked in poison 526 OPERATION AND MAINTENANCE at and near the entrance to the hole, and mark the spot so that it can be readily found again. Various forms of traps have been devised which are some- times employed with efficiency, and small rifles and shotguns have been used. It is absolutely essential that these pests be held in check, or it becomes impossible to operate the system with safety. 1 6. Land Slides. Where a canal is located on sidehill it frequently gives trouble in inducing land slides. These may be of two kinds. On a hillside where the natural slope is steep, the cutting for the canal may remove so much material as to leave what remains in an unstable situation, with a tendency here and there to slide into the canal. The other form of slide is that resulting from the saturation of the lower bank of the canal, inducing it to move away from the canal channel. Both types of slide are promoted by mois- ture, which in the case of the latter is furnished by the canal, and therefore most likely to happen in the summer. The first type or upper slide is more likely to become and remain saturated in early spring while snows are melting, and may therefore occur before the beginning of the irrigation season. In fact, a full canal has some tendency, by its weight of water, to balance and retard a slide from above. Since both types of slide are promoted by saturation of the material, it follows that the provision of good drainage is in some degree a remedy. If ponds occur above the canal they may have a tendency to promote sliding, and drawing them off by adequate drainage may be sufficient to prevent this. The same may be said of any system of surface or subsurface drainage which tends to prevent the saturation of the material above the canal, or of any stratum therein. The probable occurrence of slides from above is often the factor that determines the infeasibility of building and main- taining a canal on any given sidehill, and conditions should be carefully studied before deciding this question. In order to counteract the weakening effect of the cut in the material it may be advisable in some cases to provide a canal LAND SLIDES 527 section 01 some rigidity, as a concrete flume or pipe which can transmit the pressure from above to the lower bank, and to the ground under tne conduit, which thus serves as a retaining wall. Such a device was employed for this purpose on the Tieton Main Canal (Fig. 119). Where there is danger of sliding of the lower bank this may be diminished to a large extent by lining the canal with concrete, and for this reason and the further reason that the lined canal by reason of diminished friction will carry the required amount of water with less cross-sectional area, and will, by preventing seepage save valuable water, many sidehill canals are lined when first constructed, and many others are lined later, as a maintenance precaution. But when done as an afterthought, there is loss of economy. The character of the soil most affected by saturation is clay, some forms of which become semiliquid, and have very little stability when in that condition. Certain strata on which the bank rests may be of material which is rather porous overlying other strata which while not so porous, become unstable when saturated, and act as lubricants on which the overlying bank can readily move. If these strata dip down the hill, we have favorable conditions for sliding, and it may be that they make a proposed canal location infeasible, and that it will be neces- sary to build a flume or tunnel to avoid danger. This is especi- ally true where the location is above a railway or other valuable property that would be damaged by a canal break. In doubt- ful cases the condition may be materially improved by providing deep tile drainage to prevent saturation of the treacherous material. The only remedy for sliding is to prevent saturation. REFERENCES FOR CHAPTER XX HARDING, S. T. Operation and Maintenance of Irrigation Systems. McGraw- Hill Book Company, New York. NEWELL, F. H. Irrigation Management. D. Appleton & Co., New York. BROWN, HANBURY. Irrigation, its Principles and Practice. D. Van Nostrand Co., New York. CHAPTER XXI INVESTIGATION OF A PROJECT 1. Reconnaissance. To investigate the feasibility and cost of a proposed irrigation project it is necessary to consider all the various factors affecting the probability of the existence of a feasible project. First, is there a sufficient area of good land, apparently accessible to the water supply? If this seems doubtful it may be necessary to make reconnaissance surveys, to ascertain how much land can be reached, and its general quality. Before much expenditure is incurred for this purpose, however, inquiry should be made into existing data regarding the water supply, for if this is scanty or precarious, further expenditure may be unwarranted. If a reconnaissance shows ample good land fairly smooth, an apparent water supply without storage, or a storage site if necessary, with no obvious insuperable obstacles in the way of putting the water on the land, surveys may be started to measure the water supply and determine the cost of controlling and bringing it to the land. 2. Surveys. Early attention should be given the water supply. For unless a long record of stream flow kept by the government is available, or the water supply is a great river far more than the needs of the project, the measurements should begin as soon as possible, for they must continue several years to be a safe guide. One or more gaging stations should be established, and continuous record kept. Students of water supply problems are often misled by formulae for computing runoff from data upon rainfall, evapora- tion, etc., put forth by over-confident authors, or derived from 528 SURVEYS 529 observations of totally different conditions. Nothing must be allowed to take the place of actual measurements of the stream. If the data available indicate that storage will be necessary to provide a sufficient supply of water when needed, the existence, capacity and cost of storage opportunities must be carefully investigated. If these are wholly or partly in private owner- ship liberal allowance must be made for their purchase, and this is an expense that is difficult to forecast, and is commonly under- estimated. Careful examination should be made of the dam site, especially the character of its foundation and abutments and the available material for construction. The amount of sediment carried by the stream should be considered with reference to its effect on the life of the reservoir, and if con- siderable should be carefully measured. These measurements can usually accompany the measurements of the stream and add very little to the cost. A topographic survey of the reservoir site or sites should be made, in 10 foot contours if the reservoir is deep, and closer intervals for shallow reservoirs. The scale may be 2000 feet to an inch for very large reservoirs, to 500 feet to an inch for small ones. The dam site should be mapped on a scale of 100 feet to an inch or larger, in 5 foot contours if precipitous and i or 2 foot contours if the slopes are .gentle. Careful examination should be made of the rock and other material with reference to its suitability for abutments and foundation, and its availability for construction purposes. If the funds are available and construction seems probable exami- nation by means of test pits or borings should be undertaken. As a thorough exploration of this kind is expensive, it may be wisest to confine preliminary investigations to a few test pits at first, until more expenditure appears warranted. Examination of diversion facilities should be made early, as these may have an important bearing on the cost and feasi- bility. -It is desirable to divert the stream at such an eleva- tion that the canal will deliver the water by gravity flow along 530 INVESTIGATION OF A PROJECT the upper edge of the land to be irrigated. This may be some- times attained by a diversion sufficiently upstream to achieve this, or if the grade of the stream is moderate and good dam sites appear, it may be best to build a diversion dam of considerable height to raise the water to the necessary elevation and lead the canal from that point. In this way heavy canyon con- struction may sometimes be avoided. Surveys of all promising alternatives should be made and compared before decision is reached. Involved in the above alternatives may be different eleva- tions on which the canal may be located. It may be that to command all the irrigable land by gravity will involve an undue amount of heavy construction, and economy will require a canal location on lower and smoother ground, leaving certain tracts of land above the canal to be abandoned or perhaps eventually to be pumped upon. Trial lines may be run to test various alternatives, and if these are numerous it may be wise to make a topographic contour map of the country under study, on which all alternatives may be examined before making any very detailed survey. On such a map, such alternatives as those of tunnel and open canal, flume and inverted siphon, and the like, may be compared. It also furnishes the preliminary information for planning a distribution system. When the main canal line is decided upon, a detailed contour map is advisable for estimating quantities. On this map the character of material to be moved should be shown, whether rock, shale, sand or clay, so as to give a correct indication of the probable cost of excavation. This detailed map, the general topography map, and the borings at the dam site, are all rather expensive details that are not justified unless most of the other serious doubts of the feasibility of the project have been removed. A detailed soil survey of the irrigable land is to be desired before construction is begun so as to determine the area of good land available, and its water requirement. However attractive the water supply and the engineering features of the project, the returns must depend on the area and fertility of the lands from which crops ESTIMATES OF COST 531 may be secured. This information is therefore just as important as the water supply, and it is as often overlooked or over- estimated. The character of the crops to be raised and their market are important factors, and these may depend upon railroad facilities to a large extent. All these must therefore be given due weight in estimating prospective returns. 3. Estimates of Cost. At every stage of the investigation it is necessary to make tentative estimates of cost, for com- parison of alternatives, for elimination of unpromising features, and for forecasting the ultimate outcome, so that unnecessary expenses in surveying an infeasible project may be avoided. These preliminary estimates may be controlled by unit prices adopted for all, which may serve their purpose fairly well though not accurate, provided the different items of cost bear the correct relations to each other. But when it comes to the estimate on which the feasibility depends, it is important that these unit prices and all other items of cost be not only relatively but actually as accurate as possible, and this presents a problem of great difficulty in many cases. The tendency to underestimate construction costs is nearly universal. Even in the construction of a building in a city, where the materials and processes are well standardized, labor conditions are stable and well-known and daily experience furnishes abundant data for estimates, the owner generally finds when his house is finished it has cost more than he expected. But when new conditions are encountered, and the multitude of variations in materials, transportation and labor conditions are involved, this tendency is greatly intensified, and nearly always, costs exceed the estimates, unless great effort is made to make these liberal. There are several distinct causes for this tendency to underestimate costs. a. Bias. There is no attempt here to consider dishonest estimates made with a deliberate or conscious purpose to present an attractive showing calculated to favorably influence investors regardless of the facts. We are now dealing with the influences that bias honest effort. Everyone has a natural 532 INVESTIGATION OF A PROJECT desire that work he has done achieve some result. The investi- gations would generally not have been started except for the existence of a strong belief that a feasible project would be developed, and thus exists a strong if unconscious desire that the investigation shall result favorably. b. Influence. There frequently exists also, a strong desire on the part of someone interested in the results, who is in touch with the inquiry, who continually presents arguments and facts favorable to cheap construction and large returns, which are likely to have considerable influence on the most judicial mind. c. Inaccurate Data. The estimator's principal guide is previous experience. So far as this is his own, and intelligently used, it is the safest possible guide, although subject to the limitations of careful and discriminating use. But usually, the engineer must depend less upon his own personal experience than upon the records made by others, and here he is upon dangerous ground, for these records are mostly one-sided. Where work has been performed very cheaply, it is the subject of boast or exploitation, and its cheapness is often greatly exaggerated by the omission of such charges as plant cost, overhead, preliminary work, etc. Reports of unit costs are often selected from the most favorable periods of work, thus omitting expensive delays, repairs or other contingencies, and may thus be less than half the average actual cost. Where reports of excessive costs accidentally become public, they are generally accompanied by explanations of unusual difficulties, abnormal conditions, storms, accidents, or the stupid blunders of someone else; contingencies not to be expected again, so that large or even average costs are thus discredited and atten- tion focused upon those that are the minimum, whether reliable or not. For these reasons, cost data are often very misleading. d. Omissions. One of the commonest errors in estimates is the omission of certain elements of cost, owing to the inherent difficulty of foreseeing everything. This applies not only to ESTIMATES OF COST 533 unforeseeable expenses but those which could be easily fore- seen but were overlooked or forgotten. For these reasons, the beginner should understand that the path of the estimator is beset with pitfalls which he must be careful to avoid, and he should be cautious about accepting current opinions or even published records of cost until these have been verified and their completeness and reliability established. CHAPTER XXII SPECIFICATIONS IT is important to have clear, concise specifications cover- ing engineering work required, and they should be as specific as conditions will permit, leaving a minimum of discretion with the engineer. The important points are to cover the subject thoroughly, and avoid ambiguity or possibility of more than one obvious meaning. The samples here given are in the main those evolved by fifteen years' experience on large works by the U. S. Reclamation Service, and their provisions have been thoroughly tested. It is not intended, however, that they be used without modification, but only as a guide for drawing specifications adapted to local conditions in each case. The above applies especially to work let by contract, for which written specifications are obviously necessary. It has also been found advisable, on large works, where construction is performed by the direct method of hired labor without the intervention of a contractor, to draw similar specifications for the guidance of the engineer in charge and his subordinates, where the superintendent of construction occupies a position in authority similar to that of a contractor, and although under the orders of the engineer, is held independently responsible for the construction forces and their work. In this manner the Lahontan Dam in Nevada, and the Arrowrock Dam in Idaho were built. The specifications of the latter are given as a sample of how this work was performed. There are also pre- sented standard specifications for some of the most important work required in irrigation. 534 SPECIFICATIONS FOR ARROW ROCK DAM 535 SPECIFICATIONS FOR ARROWROCK DAM GENERAL PROVISIONS 1. The Requirement. The purpose of the work covered by these specifications is the construction of a masonry dam and its appurtenant features across the Boise River at Arrowrock, in section 13, T 3 N, R 4 E, about 20 miles east of Boise, Idaho. 2. List of Drawings. 1. (14,302) General map and plan of construction works. 2. (14,303) Cross-section of dam. 3. (14,304) Plan of dam. 4. (14,305) Elevation of developed upstream face of dam. 5. (14,306) Plan and sections of spillway. 6. (14,307) Typical sections of diversion tunnel. 7. (14,308) Cross-sections of north wing walls at tunnel inlet and outlet. 8. (14,309) Cross-sections of south wing walls at tunnel inlet and outlet. Q. (14,310) Cross-sections of cofferdams. 3. Organization. The work covered by these specifications is authorized by the Secretary's order dated January 7, 1911, and shall be done with Government forces. The Director of the Reclamation Service, through the supervising and construction engineers and superintendent of construction, will purchase all materials, equipment and supplies and will employ all labor necessary for the con- struction and completion of the dam and its appurtenant features. A scale of wages shall be fixed from time to time by the supervising engineer, after having received suitable written recommendations covering such scale of wages from the construction engineer and superintendent of construction. The supervising engineer shall divide the organization as would be done if the work were to be per- formed by contract, into the engineering division, under the direction of the con- struction engineer, and the construction division, under the direction of the super- intendent of construction. The duties of the engineering division shall be similar to those of the engineering force on contract work; the principal duties of this division being to make esti- mates and designs for the works and to see that the works are built in accordance with the plans and specifications, and this division will be held strictly responsible for this feature of the work. This division shall also give the construction division such help as may be necessary in getting out designs and estimates for the construc- tion plant. For the purpose of executing his duties, the construction engineer shall organize office and field engineering corps that shall report, directly to him. All work, other than clerical, in connection with the construction, maintenance and operation of the Arrowrock Railroad, the power house at the Boise River Diversion Dam and the transmission line leading therefrom to Arrowrock shall be under the charge of the construction engineer. The duties of the construction division shall be similar to those of the con- struction force on contract work; the principal duties of this division being to pro- vide methods and plans for actually executing and building the works and to construct the work. This division will be held particularly responsible for the 536 SPECIFICATIONS progress and cost of the work. In any work on designs and estimates for the construction plant that, under contract work, would be done by the contractor's engineering forces, the construction division shall be assisted as much as may be necessary by the engineering division. The superintendent of construction shall select his foremen and principal assistants, who shall report to him, and he will be held responsible for the efficiency of the entire construction force. He shall detail one man as costkeeper, who shall obtain from the clerical and engineering forces all data necessary for compiling the required reports of costs. At the end of each calendar month the costkeeper shall furnish the construction engineer (with a copy to the supervising engineer) a detailed statement, certified by the superintendent of construction of all costs, including estimated apportionment of general expenses, depreciation, unit costs of work done, etc. The supervising engineer's office at Boise shall handle all advertisements, pur- chases and vouchers covering materials and supplies for use in the construction of the dam, and the chief clerk of the supervising engineer's office shall be responsible for all clerical work. He shall conduct the clerical work in such a manner as to relieve the engineering and construction divisions from the necessity of occupying their time with clerical matters. The chief clerk shall detail any clerks who may be necessary at Arrowrock or other points on the Storage Unit, and these employees shall be responsible to him in connection with clerical matters, but shall be sub- ject to the orders of the construction engineer or superintendent of construction in connection with administrative matters. Pay rolls shall be made up in the super- vising engineer's office, based on time books certified by the superintendent of construction and transmitted from Arrowrock, and the fiscal agent at Boise will pay all employees, including those receiving time checks. 4. Reports and Estimates, At the end of each calendar month the engineer shall make an approximate estimate of the work done to that date, and these esti- mates shall be prepared with the same degree of completeness as would be required in the case of contract work. As soon after the end of each calendar month as possible, a complete approximate cost report shall be prepared as outlined in paragraph 3 and transmitted to the supervising engineer's office with the con- struction engineer's regular monthly report. Upon the completion of each feature, a detailed report of that feature shall be prepared and shall include a complete history of the feature and a final estimate of quantities with total and unit costs. 5. Progress of Work. Work shall be commenced on such features as wagon roads, telephone lines, etc., within thirty days after the authorization of construc- tion, and the work on main features, the dam and its appurtenant structures, will be begun as soon thereafter as practicable. The diversion works will be com- pleted to such extent that water may be diverted from the present river channel immediately after the June floods in 1912. Work of excavation in the river channel shall then be begun and the work will be prosecuted with all practicable speed until the concrete in the dam shall have been placed to about elevation 3000. After that time the rate of progress shall be as great as is consistent with proper economy, and as the apportionment of funds will permit. 6. Cement. All Portland cement shall be purchased through the cement expert of the U. S. Reclamation Service at Denver, Colorado, and shall be inspected under his direction before shipment. The same care shall be observed in the unloading, storing, and safe keeping of the cement, and for the return of the full number of SPECIFICATIONS FOR ARROW ROCK DAM 537 cement sacks to the railroad station in serviceable condition, as is used on Construc- tion work under contract. Upon-the delivery of the Portland cement at the dam site, it shall be reground with granite or other suitable material to form sand- cement, which shall be used throughout the dam, spillway weir, and lining, in the same manner as Portland cement, unless otherwise specifically ordered by the engineer. Hereafter in these specifications the term " sand-cement " will signify the product of regrinding Portland cement with suitable blending material in pro- portions fixed by the chief engineer, and these proportions shall be one part sand to one part cement by weight, unless otherwise directed by him. All sand-cement shall be inspected and tested before being used in this work. 7. Electric Power Plant. The United States will build and operate a aooo-H.P. hydro-electric power plant at the Boise River Diversion Dam, about 14 miles west of Arrowrock, together with the necessary transmission lines for furnishing power for construction purposes at the dam site. So far as may be possible and economi- cal, all construction machinery shall be operated by electrical power. This power plant will not be completed and in operation until about June i, 1912, but electric power purchased in the local market will be available for construction purposes at the dam about October i, 1911. A fair rate, to be determined by the super- vising engineer, for the power used from this plant, shall be charged against the work at the dam, and the power plant will be given a corresponding credit. 8. Steam Railroad. The United States will build and operate a standard gage steam railroad between Arrowrock and Barberton, Idaho, connecting at the latter point with the Barberton branch of the Oregon Short Line Railroad. This road will be in operation by November 15, 1911. Freight rates on this line shall be established from time to time, by the supervising engineer. 9. Telephone Lines. Telephone lines will be built and operated by the United States between Arrowrock and Boise, Idaho, and will be ready for service about May i, 1911. 10. Wagon Roads. About 25 miles of wagon roads will be built by the United States to replace roads that will be flooded by the Arrowrock Reservoir and for various other purposes. Some of these roads will be of service in hauling lumber and other materials and supplies. The location of these roads is shown in drawing i . 11. Construction Camp. A construction camp to accommodate about 800 men will be built and maintained at Arrowrock by the United States, and the sanitary conditions at this camp shall be kept at a high degree of excellence at all times. 12. Sawmill.' The United States will build and operate a sawmill in the Boise National Forest about 16 miles east of Arrowrock and, as far as may be feasible and economical, all lumber needed in the construction of the dam and its appur- tenant features, including the construction cam'-- shall be manufactured at this mill. GENERAL FEATURES 13. Description. The work contemplated under these specifications consists of constructing a storage reservoir with a concrete masonry dam and a concrete masonry spillway, together with the incidental work of excavating and construc- ting diversion works. The dam will be a gravity type, concrete dam, curved in plan. It will be about 1050 feet long on top and its maximum height will be about 350 feet above the 538 SPECIFICATIONS deepest part of the excavation. The lowest portions of the foundation will be about 80 or 90 feet below the present bed of the river. The spillway will consist of a concrete weir about 400 feet long, discharging into a channel, to be cut in the hillside. This channel will convey the water around the north end of the dam and will discharge into Deer Creek. The diversion works will consist of two crib cofferdams across the Boise River and a tunnel about 490 feet long, with a cross-sectional area of about 670 square feet and a capacity of about 20,000 second-feet, having an inlet bell mouth about 90 feet long and an outlet bell mouth about 150 feet long. EXCAVATION OF TUNNELS 14. Description of Diversion Tunnel. The tunnel will be located in rock for its entire length, and for the greater part will be in firm, hard granite. Pockets of loose lava rock may be encountered but it is expected that such pockets will be of small extent. Where the nature of the rock makes it necessary the sides and roof of the tunnel shall be supported by suitable timbering and lagging. All expense of such timbering shall be classed as timber lining, but the cost of the lagging shall be charged to excavation. As the tunnel is to be lined with concrete on the bottom and sides and with timber above the springing line of the arch, special care shall be exercised to reduce the overbreak to a minimum and to have the exposed rock in good condition, free from cracks and other objectionable defects. 15. Classification of Material in Diversion Tunnel. All material excavated for the diversion tunnel between stations 1+50 and 6 + 20 and within the limits of the required cross-section as shown in the drawings shall be measured and estimated in cubic yards and classified as follows: Heading and Arches. All material above the springing line of the arch. Bench. Alt material below the springing line of the arch. 1 6. Shaft. A shaft about 6 feet square for use in refilling the tunnel shall be driven as directed by the engineer. As this shaft will also be refilled with concrete, it shall be of the smallest cross-section practicable. The excavation of this shaft shall be measured and estimated by the linear foot. 17. Cut-off Tunnel. A cut-off tunnel shall be driven along the line of contact between the lava and granite and shall later be filled with concrete. This tunnel shall be of the smallest practicable dimensions and the excavation of the same will be measured and estimated by the linear foot. EXCAVATION FOR DAM, SPILLWAY, TUNNEL PORTALS AND COFFERDAMS 1 8. Description. The excavation for the dam will cover all excavation required to obtain a suitable foundation for the dam, including excavation for keyways, cut-off trenches, steps or benches, unless such excavation is included under special preparations of rock foundations for dam as outlined in paragraph 46. The mate- rial in the river channel consists mainly of river sand, gravel, and boulders, and constitutes the greater part of the material to be excavated for dam foundation. On the south side of the river, the excavation will consist of stripping the dam site of a shallow covering of loose material and cutting suitable foundation in the rock. The work on the north abutment will consist mainly of removing a mass of seamy rock and large boulders embedded in loose rock and loam, and of cutting a suit- able foundation in the ledge rock. SPECIFICATIONS FOR ARROW ROCK DAM 539 The greater part of the material to be excavate:! for the spillway consists of granite rock, covered by a shallow layer of loam and sand. The excavation for the tunnel portals will cover all excavation required for the inlet and outlet bell mouths and not included in the tunnel proper. The material consists of a lava rock talus overhang sand, gravel, boulders, and ledge rock. The excavation for the cofferdams will consist of excavating the river bottom to a level bed and excavating cut-off trenches at the abutments on the north side of the river. 19. Classification. All excavation for the dam, spillway, tunnel portals and cofferdams shall be measured and estimated by the cubic yard under the following classes: Dry Excavation. All material excavated above elevation 2960, which is about the mean low water level of the Boise River. Wet Excavation. All material excavated below elevation 2960. The classifications of material shall be the same under each of the above desig- nations and shall be as follows: Loose Material. The excavation of loose material shall include the excava- tion and disposal of all loam, sand, gravel, mud, loose rock, and all other mate- rial not included in rock excavation, except as hereinafter specified under Para- graph 46. Rock Excavation. Rock excavation shall include the excavation and disposal of all solid rock removed by blasting, boulders of one-half a cubic yard or more in volume, and all rock removed by barring and wedging. Wherever the excava- tion consists of a large proportion of boulders of one-half a cubic yard or more in volume occurring in gravel, earth, or loose rock, as is the case near the river level on the north side of the river channel, the amount of " rock excavation " may be estimated as a percentage of the total excavation if deemed advisable by the engi- neer. 20. Rock Excavation for Foundations. Rock shall be excavated to a sufficient depth to secure a foundation on sound ledge rock, free from open seams or other objectionable defects. It is the intention to build the masonry against the sides of these rock excavations. To preserve the rock outside the lines of the excava- tion in the soundest possible condition and to obtain over the whole foundation a rock surface free from open seams or cracks, unusual precautions shall be used in excavating. Rock excavation may be done by blasting to the extent directed by the engineer, with explosives of such moderate power and in such positions as will neither crack nor damage the rock outside of the prescribed limits of the excava- tion; and whenever, in the opinion of the engineer, further blasting is liable to injure the rock upon or against which the masonry is to be built, blasting shall be discontinued and the excavation of the rock continued by wedging and barring, or other approved methods. 21. Preparation of Rock Foundations. The surfaces of the rock foundations shall be left sufficiently rough to bond well with the masonry and, if required by the engineer, shall be cut into rough benches or steps, and great care shall be taken not to open or break the ledge rock unnecessarily in doing this work. Before laying the masonry on or against the ledge rock, the latter shall be scrupulously freed from all dirt, gravel, scale, loose fragments, and other objectionable substances by means of jets of water, air, or steam under effective pressure, or of stiff brooms 540 SPECIFICATIONS hammers and other effective tools. Steam jets shall be used to remove thoroughly any ice or snow that may be on the ledge rock when it is desired to lay masonry. All springs shall be piped and grouted in a satisfactory manner. After cleaning and before concrete is laid on or against the ledge rock the water shall be removed from the depressions so that the surface can be inspected to determine whether seams or other defects exist. All expense of preparing rock foundations except as hereinafter stated in paragraphs 44, 45, and 46 shall be included in the cost of " rock excavation." GENERAL REQUIREMENTS FOR CONCRETE 22. Composition. All concrete shall be composed of cement, sand, gravel and water, or cement, sand, gravel, water and cobblestones, in the proportions fixed by the construction engineer for the character or work in hand. The cement used will in general be sand cement, but in the diversion works and in other special cases when directed by the engineer. Portland cement may be used. 23. Sand. The sand used in concrete shdl be of a quality satisfactory to the construction engineer, shal 1 be free from organic matter, and shall not contain more than 10 per cent by weigh of clay or other foreign matter. The particles of sand shall be well graded, ana the coarsest particles shall not be larger than those that will pass a screen having f-inch square holes The sane shall be of the best quality obtainable at reasonable cost in the vicinity of the work. 24. Gravel. The gravel used in the concrete shall be either clean, hard, broken rock, or clean, screened gravel and shall be well graded and of such sizes as will pass a grizzly having bars set 3 inches apart and will be retained on a screen hav- ing | -inch square holes. 25. Cobblestones. Cobblestones used in the concrete shall be sound, clean gravel or broken rock of such size as will pass a grizzly having bars set about 6 inches apart and be retained on a grizzly having bars set 3 inches apart. 26. Water. The water used for the concrete shall be reasonably clean and free from objectionable quantities of organic matter, oil, grease, or other like impurities. 27. Mixing. The sand, gravel, cobbles, and cement shall be mixed and the quantity of \vater added shall be such as to produce a homogeneous mass of uni- form consistency. Except in cases of emergency when small quantities are needed, the concrete shall be mixed by one of the standard " batch '' machine mixers. Whenever any machine fails to perform the mixing thoroughly, it shall be made satisfactory or removed and another machine substituted. When from any cause resort to hand mixing is necessary, the mixing shall be done in a thorough and satisfactory manner. Concrete shall be mixed " wet " wherever practicable and " dry " only when the nature of the work renders such use unavoidable. 28. Placing. The concrete shall be handled in such a manner that initial set or the separation of the ingredients before depositing shall be avoided. Should separation occur, the concrete shall be thoroughly remixed. Xo concrete that has received its initial set Ibefore being deposited shall be used in the work and any such mixture shall be immediately removed from the vicinity of the work. All surfaces upon which concrete is laid shall be cleaned as specified or directed and thoroughly wet immediately before concrete is deposited. If so directed, a bed of fresh mortar of the thickness required or a thin coat of grout shall be spread SPECIFICATIONS FOR ARROW ROCK DAM 541 over the foundation and thoroughly worked into all depressions and crevices. Under no circumstances shall concrete be laid in deep, moving, or muddy water. All exposed faces of concrete work shall be moulded against steel forms, or, if timber forms are used, against lagging that has been sized to uniform thickness and placed so as to prevent leakage of the fluid concrete. All forms shall be accu- rately and rigidly placed to conform to the lines established by the engineer. The bracing and tying devices must have sufficient strength and stiffness to with- stand the pressure of fluid concrete without springing or warping. The con- crete shall be placed against these forms and so manipulated by spading and tamping as to secure a body of concrete having the maximum possible density and showing smooth and uniform faces. Where the use of contraction joints is speci- fied for the separation of adjoining masses, the expense of constructing all such joints shall be included in the cost of placing concrete. 2Q. Building Neiv Concrete on Old. In order to insure a thorough bonding and a perfect joint between fresh concrete and that which has set, such provision shall be made of steps, dovetails or other devices or methods as may be prescribed. Whenever fresh concrete and concrete that has set are joined, the contact sur- faces of the old concrete shall be thoroughly roughened and cleaned, and it shall be clean and wet, but free from pools of water, at the moment the fresh con- crete is placed. If directed, a bed of fresh mortar or a coat of grout shall be applied to the contact surfaces of the old concrete and thoroughly worked into all depressions and crevices. Special efforts shall be made to remove very thoroughly all laitance and other substances which would prevent complete cohesion of the concrete throughout the main body of the dam. 30. Laying Concrete in Freezing Weather. No concrete shall be laid during freezing weather unless special precautions are taken to prevent damage from freez- ing. Whenever concrete is laid during freezing weather, the materials of the aggre- gate shall be thoroughly heated to remove all frost and warm water shall be used in mixing. No frozen materials shall be used in making concrete and no concrete shall be allowed to freeze in any part within ten days after mixing nor shall any concrete be built upon a frozen surface. 31. Embedded Rock. In all mass concrete having a thickness of 15 inches or more, sound and clean cobblestones or rock fragments of a size that can be lifted and handled by one man, shall be incorporated in the concrete. The proportion of such rocks shall be as nearly uniform throughout as practicable. No rock shall be laid in actual contact with an adjacent one or wjthin 2 inches of the forms. In the main body of the dam, there shall be placed hard, sound, clean, and durable rocks of derrick size, carefully shaken to position in fresh beds of concrete. When- ever possible, smaller rocks shall be embedded in the concrete between the large rocks. The object is to obtain, especially in the main body of the dam, a mono- lithic mass of stone and concrete containing as large a proportion of rock and as impervious to water as it is practicable to secure. Stones to be used as embedded rock wherever used shall be thoroughly cleaned before being brought to the place where they are to be used, by washing with water under pressure from a nozzle, by the use of brushes, or as otherwise directed, and shall be satisfactorily clean when placed in the concrete. All rock shall be thoroughly wet at the time of plac- ing in the work. 32. Sprinkling. During all of the year except the colder months, all concrete 542 SPECIFICATIONS shall be kept thoroughly wet by sprinkling with water until the concrete shall have become thoroughly set. 33. Finishing Concrete Surfaces. Immediately after the removal of the forms, all rough surfaces and irregularities of exposed work shall be dressed and all voids that may occur shall be filled with mortar. The floors of the spillway and diver- sion tunnel shall have their top surface finished by straight-edging and floating similar to a sidewalk finish, except that the standard mixture of concrete shall be used without any additional surface coat of mortar. Such surfacing shall be done immediately after placing the body of the concrete. A wash of thin cement grout shall be applied to all exposed surfaces of concrete except floors and similar surfaces. The outlet conduits shall be finished smooth and particular care shall be taken by hand troweling or otherwise, to make a hard, smooth, surface. CONCRETE FOR SPILLWAY 34. Description. The concrete work in the spillway will consist of constructing of mass concrete the spillway weir, which will be about 400 feet long, and of lining the sides and bottom of the spillway trench with reinforced concrete and of con- structing the roadway and parapet walls below the end of the dam. 35. Classification. All concrete placed in the spillway weir shall be classed and estimated as " spillway weir." All other concrete placed in the spillway structure shall be classed and estimated as " spillway lining." 36. Special Foundation of Broken Stone. The foundation for certain portions of the concrete used in the spillway lining shall be a layer of broken stone, not less than 4 inches thick at any point, thoroughly rammed. The top of this layer of rock shall be at the bottom of the concrete lining as shown in the drawings. This special foundation shall be measured and estimated in cubic yards on a basis of a 6-inch thickness, unless a greater depth of broken stone is required by the engi- neer, in which case the additional rock required shall be measured and estimated. Details of this work are shown and described further in drawing 5. CONCRETE FOR DIVERSION TUNNEL 37. Description. The bottom lining of the tunnel will consist of plain concrete and the side lining will consist of plain concrete suitably bonded to the rock sides where necessary by means of steel bars. The inlet and outlet wing walls will consist of concrete lining placed on the rock sides and suitably bonded thereto, and, in most cases, surmounted by a concrete wall of gravity section. The inlet and outlet floors will consist of a lining of plain concrete where the foundation is ledge rock and of reinforced concrete where the foundation is sand and gravel. The tunnel refilling will consist of placing mass concrete in the portion of the tunnel underlying the foundations of the dam. All expense incurred in such refilling, including cofferdams, and bulkheads, shall be charged to this item. 38. Classification. All concrete placed as lining between stations 1+50 and 6+20 of the diversion tunnel shall be classed and estimated as " diversion tunnel lining." All concrete placed in inlet and outlet walls and portals and not included as tunnel lining shall be classed and estimated as " diversion tunnel inlet and outlet wing walls." All concrete placed in the floors and cut-off walls of the inlet and outlet and not included in tunnel lining shall be classed and estimated as SPECIFICATIONS FOR ARROW ROCK DAM 543 " diversion tunnel inlet and outlet floors." All concrete placed in refilling the tunnel shall be classed and estimated as " refilling diversion tunnel." 39. Refilling Shaft. The shaft shall be refilled with concrete as directed by the engineer. This refilling shall consist of mass concrete and shall be measured and estimated by the cubic yard. CONCRETE FOR COFFERDAMS 40. Classification and Description. All concrete placed in the cofferdams shall be classed and estimated as " cofferdam concrete." This item consists mainly of plain concrete to be placed in the core walls of the abutment. CONCRETE FOR CUT-OFF TUNNEL 41. Classification and Description. All concrete placed in refilling the cut-off tunnel shall be classed and estimated as " refilling of cut-off tunnel." CONCRETE FOR DAM 42. Description. It is planned to build the main body of the dam of concrete consisting of about i part sand-cement, 2\ parts sand, 5 parts gravel and 3 or 4 parts cobblestones, in which large rock and boulders of various sizes will be em- bedded. These proportions may be varied to suit conditions as they may develop. A small amount of reinforced concrete will also be used. 43. Classification and Measurement. All concrete in the dam shall be classed and estimated under one item. Deductions shall be made from the gross volume for the space occupied by the inspection tunnel and the outlets, but no deductions shall be made on account of the drainage system. SPECIAL PREPARATION OF ROCK FOUNDATION OF DAM 44. Description. After the rock foundation for the dam has been prepared as outlined in paragraph 21 of these specifications, all further work on said founda- tion whether shown in the drawings or required by the engineer, shall be designated as " special preparation of rock foundation of dam," provided such further work is not included under paragraph 28 of these specifications. 45. Classification. Special preparation of rock foundations of dam shall be measured and estimated under the following classes: Areas Receiving Special Preparation. All areas receiving special preparation as outlined in paragraph 46 shall be measured and estimated by the square yard and at least 5 square yards shall be allowed for any area on which such special preparation is required. Pressure Grouting. All pressure grouting as outlined in paragraph 47 shall be measured and estimated by the barrel of cement used in such grouting. Drilling Drainage Holes and Main Grout Holes. All drilling for drainage holes and for the main grout holes shown on the drawings and not included under para- graph 46 shall be measured and estimated by the linear foot of holes drilled. 46. Areas Receiving Special Preparation. Portions or the whole of the founda- tions of the dam .may be designated for special preparation and in all areas thus designated seams and cavities shall be traced as far as directed by the engineer by drilling holes or by other approved means. All such seams and cavities shall then be filled with concrete, mortar, or grout. Whenever directed by the engineer, 544 SPECIFICATIONS grout shall be pumped under pressures required by him through hose or pipe of at least 2 inches in diameter, and the connection between the hose or pipe and the rock shall be made tight. Such grouting does not include grouting the main grout holes shown in the drawings and described under paragraph 47. 47. Pressure Grouting and Drilling Drainage Holes and Main Grout Holes. In addition to the drilling and pressure grouting that may be required under paragraph 46, deep grout and drainage holes shall be drilled as shown on the drawings or as directed by the engineer, and after a portion of the masonry in the dam has been placed, grout under suitable pressure shall be pumped into the grout holes as directed by the engineer. STRUCTURAL TIMBER 48. Description. Structural timber will be required for the upper and lower cofferdams, for portions of the diversion tunnel inlet and outlet wing walls, and for the timber lining for the roof of the diversion tunnel. All structural timber shall be of the dimensions shown in the drawings, free from loose knots, shakes, or other imperfections that impair its strength for the uses for which it is intended. Unless otherwise specified or required, all structural timber shall be of pine or fir obtained near the sawmill mentioned in paragraph 12. 49. Measurement. All structural timber shall be measured by the thousand feet board measure in place. COFFERDAMS AND TIMBER WING WALLS 50. Description. The upper and lower cofferdams and the timber of the diversion tunnel wing walls will consist of timber cribs of the dimensions shown on the drawings, thoroughly filled with loam, sand, gravel and rock as specified in paragraph 53. Longitudinal timbers shall break joints and shall butt only at intersections with cross timbers. At butting joints, two drift bolts shall be placed in the end of each butting timber and at all other intersections the timbers shall be secured by two drift bolts. TIMBER LINING IN DIVERSION TUNNEL 51. Description. The timber lining in the diversion tunnel will consist of 4 X 12- inch planks securely spiked to i4Xi4-inch timber sets as shown on the drawings. The 4 X i2-inch planks shall be of Oregon fir or other suitable material, carefully dressed to the required thickness. These planks shall break joints and butt only at intersections with the timber sets. At butting joints three lo-inch boat spikes shall be placed in the end of each abutting plank, and at all other intersections the planks shall be secured by three zo-inch boat spikes. The space between the tim- ber sets and the excavated section shall be thoroughly filled with blocking and lagging as directed by the engineer. All cost of such blocking and lagging, not provided for in paragraph 14, shall be charged to the cost of timber lining. PILING 52. Description and Measurement. Round piles and sheet piles of the dimen- sions shown in the drawings will be required in the construction of the cofferdams. Round piles shall be measured as the number of such piles actually placed in the cofferdams.. Round piles shall be of lengths shown on the drawings and shall SPECIFICATIONS FOR ARROW ROCK DAM 545 be cut from sound, growing timber of either pine or fir, straight and tape'ring, and not less in diameter than 8 inches at the smaller end. Sheet piles shall be made of sound fir or pine timbers of the size and lengths required with strips of 3X4- inch timber securely spiked on two opposite sides in such a manner as to form a tongue and groove on each pile. Sheet piles shall be measured and estimated under two heads, " number of piles driven " and " feet board measure." The ." number of piles driven " shall include only the number of piles actually driven and left in the cofferdams. " Feet board measure " shall include only such piles as are driven and left in the cofferdams but shall include the waste by cut-off from such piles. ROCK FILL 53. Description and Measurement. Rock fill will be required in the cofferdams and in the crib portions of the tunnel wing walls. It shall consist of rock frag- ments of varying size, sand, gravel and loam in proportions fixed by the engineer, the whole mass being classed as rock fill. The manner of placing rock fill shall be subject to the approval of the construction engineer and will vary in different parts of the work, but wherever practicable the voids in the rock fill shall be filled with the fine material by hydraulicking this material compactly in place. Rock fill will be measured in place and estimated by the cubic yard. RIPRAP 54. Classification. Riprap will be classed as follows: Grouted Riprap. All riprap grouted with cement grout or with concrete. Plain Riprap. All riprap not included in grouted riprap. 55. Description. Riprap will consist of rock of good, hard durable quality, not less than 12 inches in thickness, placed upon a bed of gravel or broken stone not less than 9 inches in thickness. The riprap shall be laid by hand and the base of each stone shall be bedded in the foundation with its top conforming to the surface required. All spaces between the stones shall be filled by smaller stones and gravel. The thickness of the riprap shall be as required by the engineer, and the thickness of the foundation shall be not less than two-thirds the required thickness of the rock. If grouting is required the grout shall be composed of i part cement and 3 parts sand, or of concrete in about the proportions of i part cement, 3 parts sand and 6 parts gravel or broken stone, which shall be well worked in between the rocks after the latter are laid. DRAINAGE 56. Description and Classification. When indicated in the drawings or directed by the engineer, drainage conduits shall be placed to lines and grades as required, and due precautions shall be taken to maintain the same in perfect condition until the completion of the work. Drains shall be measured and estimated by the linear foot. PLACING METAL WORK 57. Description. The gates, frames and appurtenances, steel for concrete rein- forcement, the cast-iron lining for the outlet conduits, and all other metal work, shall be set as shown in the drawings or as required by the engineer. Anchor bolts 546 SPECIFICATIONS shall be properly built into the concrete, all gates, frames, screens and operating devices shall be set in correct position at the proper time, the rising stems shall be properly alined, and the whole finally left in good working order. Embedded surfaces shall have all dirt or other objectionable material removed before being placed in the concrete. Such steel bars for concrete reinforcement as are required by the drawings or by direction of the engineer shall be accurately placed and per- fect contact shall be secured between the bars and the mortar of the surrounding concrete. Bars shall be tightly wired together at all points of intersection and so secured in position that they will not be disturbed during the placing of the con- crete. All of the above-mentioned metal work, except steel for concrete reinforce- ment, shall be purchased through the chief electrical engineer. 58. Measurement.' Placing metal work shall be measured and estimated as the number of pounds of metal work in place. 59. Pair.ting. All exposed metal work after erection shall be thoroughly cleaned and finished with two coats oi paint. The paint shall be of good quality graphite, or other material, as selected by the engineer. The cost of painting shall be included in the cost of placing metal work. OUTLET CONDUITS 60. Description and Measurement. The dam will contain 25 or more outlet conduits having a diameter of 5 feet throughout the greater part of their length. The outlet conduits will be measured and estimated by the linear foot, the length of a given conduit being considered as the length measured on the center line of that conduit. All cost of constructing the outlet conduits shall be charged to " outlet conduits " except the cost of setting the cast iron linings, anchor bolts, etc., which will be charged to " placing metal work." INSPECTION GALLERY 61. Description and Measurement. An inspection gallery of varying size and elevation shall be constructed in the body of the dam as shown in the drawings or as directed by the chief engineer. The inspection gallery shall be measured and estimated by the linear foot, the length being considered as the actual length of the center line of the gallery measured along planes parallel to the general bottom surface of the gallery. LOG HOIST 62. Description and Classification. When log driving in the Boise River is resumed and it becomes necessary for log drives to pass the dam, suitable means shall be provided for hoisting the logs from the reservoir and transporting them to the river below the dam. All expense incurred in connection with such hoisting and transportation shall be considered a single item and classed as " log hoist and chute." CONTRACT SPECIFICATIONS 547 CONTRACT SPECIFICATIONS GENERAL REQUIREMENTS 1. Form of Proposal and Signature. -The proposal shall be made on the form provided therefor and shall be enclosed in a sealed envelope marked and addressed as required in the notice to bidders. The bidder shall state in words and figures the unit prices or the specific sums, as the case may be, for which he proposes to supply the material or machinery and perform the work required by these speci- fications. If the proposal is made by an individual it shall be signed with his full name, and his address shall be given; if it is made by a firm it shall be signed with the copartnership name by a member of the firm, who shall also sign his own name, and the name and address of each member shall be given; and if it is made by a corporation it shall be signed by an officer with the corporate name attested by the corporate seal, and the names and titles of all officers of the corporation shall be given. 2. Proposal.- Blank spaces in the proposal should be properly filled. The phraseology of the proposal must not be changed, and no additions should be made to the items mentioned therein. Unauthorized conditions, limitations or provisos attached to a proposal will render it informal and may cause its rejec- tion. Alterations by erasure or interlineation must be explained or noted in the proposal over the signature of the bidder. If the unit price and the total amount named by a bidder for any item do not agree, the unit price alone will be con- sidered as representing the bidder's intention. A bidder may withdraw his proposal before the expiration of the time during which proposals may be sub- mitted, without prejudice to himself, by submitting a written request for its with- drawal to the officer who holds it. No proposals received after said time or at any place other than the place of opening as stated in the advertisement will be considered. Bidders, their representatives, and others interested, are invited to be present at the opening of proposals. The right is reserved to reject any or all proposals, to accept one part of a proposal and reject the other, and to waive tech- nical defects. 3. Certified Check. Each bidder shall submit with his proposal an uncondi- tional certified check for the sum stated in the notice to bidders, payable to the order of Any condition or limitation placed upon a certified check will render it informal and may result in the rejection of the proposal under which such check is submitted. If the bidder to whom an award is made fails or refuses to execute the required contract and bond within the time specified in para- graph 4, or such additional time as may be allowed by the engineer, the proceeds of his check shall become subject to forfeit, and the proceeds of said check are hereby agreed upon as liquidated damages on account of the delay in the execution of the contract and bond and the performance of work thereunder, and the neces- sity of accepting a higher or less desirable bid resulting from such failure or refusal to execute contract and bond as required. The proceeds of the check of the suc- cessful bidder will be returned after the execution of his contract and the approval of his bond, and the proceeds of the checks of the other bidders will be returned at the expiration of forty-five days from the date of opening proposals, or sooner if contract is executed prior to that time. 548 SPECIFICATIONS 4. The Contract. The bidder to whom award is made shall execute a written contract with and, if bond is required, furnish good and approved bond within fifteen days after receiving the forms of contract and bond for execu- tion. If the bidder to whom award is made fails to enter into contract as herein provided, the award will be annulled, and an award may be made to the bidder whose proposal is next most acceptable in the opinion of the officer by whom the first award was made; and such bidder shall fulfill every stipulation embraced herein as if he were the party to whom the first award was made. The adver- tisement, notice to bidders, proposal, general conditions, and detail specifications will be incorporated in the contract. A corporation to which an award is made will be required, before the contract is finally executed, to furnish evidence of its corporate existence and evidence that the officer signing the contract and bond for the corporation is duly authorized to so do. 5. Contractor's Bond. Unless another sum is specified in the notice to bidders, the contractor shall furnish bond in an amount not less than 20 per cent of the estimated aggregate payments to be made under the contract, conditioned upon the faithful performance by the contractor of all covenants and stipulations in the contract. Bonds in amounts less than $5000 will be made only in multiples of $100; in amounts exceeding $5000 in multiples of $1000; provided that the amount of the bond shall be fixed at the lowest sum that will fulfill all conditions herein set forth. If during the continuance of the contract any of the sureties die or become irresponsible, may require additional sufficient sureties, which the contractor shall furnish to the satisfaction of that officer within ten days after notice, and in default thereof the contract may be suspended by and the materials purchased or the work completed as provided in paragraph 10. 6. Engineer. The word " engineer " used in these specifications or in the con- tract means the Chief Engineer of He will be represented by assist- ants and inspectors, authorized to act for him. On all questions concerning the acceptability of material or machinery, the classification of material, the execution of the work, conflicting interests of contractors performing related work; and the determination of costs, the decision of the Chief Engineer shall be final, and binding upon both parties. 7. Contractor. The word " contractor " used in these specifications or in the contract means the person, firm, or corporation with whom the contract is made. The contractor shall at all times be represented on the works in person or by a fore- man or duly designated agent. Instructions and information given by the engi- neer to the contractor's foreman or agent on the work shall be considered as having been given to the contractor. When two or more contractors are engaged on in- stallation or construction work in the same vicinity the engineer shall be authorized to direct the manner in which each shall conduct his work so far as its affects other contractors. 8. Material and Workmanship. The contractor shall submit samples or speci- mens of such materials to be furnished or used in the work as the engineer may require. All materials must be of the specified quality and equal to approved samples if samples have been submitted. All work shall be done and completed in a thorough, workmanlike manner. Work, material, or machinery not in accordance with these specifications, in the opinion of the engineer, shall be CONTRACT SPECIFICATIONS 549 made to conform thereto. Unsatisfactory material will be rejected, and, if so ordered by the engineer, shall, at the contractor's expense, be immediately re- moved from the vicinity of the work. 9. Delays. If any delay is caused the contractor by specific orders of the engi- neer to stop work, or by the performance of extra work ordered by the engineer, or by the failure of to provide material, or necessary instructions for carrying on the work, or to provide the necessary right of way, or site for instal- lation, or by unforeseen causes beyond the control of the contractor, such delay will entitle the contractor to an equivalent extension of time, except as otherwise provided in paragraph 27. Application for extension of time must be approved by the engineer and shall be accompanied by the formal consent of the sureties, but an extension of time, whether with or without such consent, shall not release the sureties from their obligations, which shall remain in full force until the dis- charge of the contract. If delays from any of the above-mentioned causes occur after the expiration of the contract period no liquidated damages shall accrue for a period equivalent to such delay. 10. Suspension of Contract. If the contractor fails to begin the delivery of the material or to commence work as provided in the contract, or fails to make delivery of material promptly as ordered, or to maintain the rate of delivery of material or progress of the work in such a manner as in the opinion of the engineer will insure a full compliance with the contract within the time limit, or if in the opinion of the engineer the contractor is not carrying out. the provisions of the con- tract in their true intent and meaning, written notice will be served on him to pro- vide within a specified time for a satisfactory compliance with the contract, and if he neglects or refuses to comply with such notice the engineer may suspend the operation of all or any part of the contract, or he may in his discretion after such notice perform any part of the work or purchase any or all of the material included in the contract or required for the completion thereof without suspending the contract. Upon suspension of contract, the engineer may in his discretion take possession of all or any part of the machinery, tools, appliances, animals, materials, and supplies used on the Work covered by the contract or that have been delivered by or on account of the contractor for use in connection therewith, and the same may be used either directly by or by other parties for it, in the completion of the work suspended; or may employ other parties to perform the work, or may substitute other machinery or materials, purchase the material contracted for in such manner as it may deem proper, or hire such force and buy such machinery, tools, appliances, animals, materials, and supplies at the contractor's expense as may be necessary for the proper conduct and completion of the work. Any cost to in excess of the contract price, arising from the suspension of the contract, or from work performed or purchases made by either before or after suspension, and required on account of failure of the contractor to comply with his contract or the orders of the engineer issued in pursuance thereof, will be charged to the contractor and his sureties, who shall be liable therefor. A special lien to secure the claims of in the event of suspension of the contract is hereby created against any property of the contractor taken into the possession of under the terms hereof, and such lien may be enforced by a sale of such property, and the proceeds of the sale, after deducting all expenses thereof and connected 550 SPECIFICATIONS therewith, shall be credited to the contractor. If the net credits shall be in excess of the claims of against the contractor the balance will be paid to the contractor or his legal representatives. In the determination of the question whether there has been such noncompliance with the contract as to warrant its suspension or the furnishing of material or the performance of work by as herein provided, the decision of the engineer shall be final and binding upon both parties. Suspension of the contract, or any part thereof, shall operate only to terminate the right of the contract or to proceed with the work covered by the contract or the suspended portions thereof. The provisions of the contract per- mitting to make changes and to make proper adjustment of accounts to cover any increase or decrease of cost on account of such changes, and all other stipulations of the contract except those giving the contractor the right to proceed with work on the items covered by the suspension, shall be and remain in full force and effect after such suspension and until the contract shall have been com- pleted and final payment or final adjustment of accounts made. 11. Changes. The engineer may, without notice to the sureties on the contrac- tor's bond, make changes: (a) in the designs or materials of machinery; (b) in the plans for installation or construction; (c) in the quantities or character of the work or material required. The changes in plans for installation or construction may also include: (a) modifications of shapes and dimensions of canals, dams, and other structures; (b) the shifting of locations to suit conditions disclosed as work progresses. If such changes result in an increase of cost to the contractor, the engineer will make such additions on account thereof as he may deem reason- able and proper, and his action thereon shall be final. Extra work or material shall be charged for as hereinafter provided. 12. Extra Work or Material. In connection with the work covered by this con- tract, the engineer may at any time during the progress of the work order work or material not covered by the specifications. Such work or material will be classed as extra work and will be ordered in writing. No extra work or material will be paid for unless ordered in writing. Extra work or material shall be charged for at actual necessary cost, as determined by the engineer, plus 15 per cent for profit, superintendence, and general expenses. The actual necessary cost will include all expenditures for materials, labor, and supplies furnished by the contractor, but will in no case include any allowance for office expenses, general superintendence, or other general expenses. At the end of each month the contractor shall present in writing any claims for extra work performed during that month and extra mate- rial delivered during that month and, when requested by the engineer, shall fur- nish itemized statements of the cost and shall permit examination of accounts, bills, and vouchers relating thereto. No such claim will be allowed which is not presented to the engineer in writing within thirty days after the close of the month, during which the extra work or material covered by such claim is alleged to have been furnished, and any such claim not so presented will be deemed to have been waived by the contractor. 13. Delays No Extra Compensation. The contractor shall receive no com- pensation for delays or hindrances to the work except when, in the judgment of the engineer, direct and unavoidable extra cost to the contractor is caused by the failure of to provide necessary information, material, right of way, or site for installation. When such extra compensation is claimed a written CONTRACT SPECIFICATIONS 551 itemized statement setting forth in detail the amount thereof shall be presented by the contractor not later than sixty days after the close of the month during which extra cost is claimed to have been incurred. Unless so presented the claim shall be deemed to have been waived. Any such claim, if found correct, will be approved and the amount found due as actual extra cost will be covered by the next estimate thereafter paid under the contract. The decision of the engineer whether extra cost has been incurred and the amount thereof shall be final. 14. Changes at Contractor's Request. If the contractor, on account of conditions developing during the progress of the work, finds it impracticable to comply strictly with these specifications and applies in writing for a modification of requirements or of methods of work, such change may be authorized by the engineer if not detrimental to the work and if without additional cost to 15. Inspection. All materials furnished and work done under this contract will be subject to rigid inspection. The contractor shall furnish without extra charge complete facilities, including the necessary labor for the inspection of all material and workmanship. The engineer, or his authorized agent, shall have at all times access to all parts of the shop where such material under his inspection is being manufactured. Work or material that does not conform to the specifica- tions, although accepted through oversight or otherwise, may be rejected at any stage of the work. Whenever the contractor on installation or construction is permitted or directed to do night work or to vary the period during which work is carried on each day, he shall give the engineer due notice, so that inspection may be provided. Such work shall be done without extra compensation and under regulations to be furnished in writing by the engineer. 16. Contractor's Financial Obligations. The contractor shall promptly make payments to all persons supplying labor and materials in the execution of the contract, and a condition to this effect shall be incorporated in the contractor's bond. 17. Experience. Bidders, if required, shall present satisfactory evidence that they have been regularly engaged in furnishing such material and machinery and constructing such work as they propose to furnish or construct and that they are fully prepared with necessary capital, machinery, and material to begin the work promptly and to conduct it as required by these specifications. 1 8. Specifications and Drawings. The contractor shall keep on the work a copy of the specifications and drawings and shall at all times give the engineer access thereto. Any drawings or plans listed in the detail specifications shall be regarded as part thereof and of the contract. Anything mentioned in these specifications and not shown on the drawings or shown on the drawings and not mentioned in these specifications shall be of like effect as though shown or men- tioned in both. The engineer will furnish from time to time such detail drawings, plans, profiles, and information as he may consider necessary for the contractor's guidance, unless otherwise provided in the proposal, agreement, or detail specifica- tions. 19. Local Conditions. Bidders shall satisfy themselve as to local conditions affecting the work, and no information derived from the maps, plans, specifica- tions, profiles, or drawings, or from the engineer or his assistants, will relieve the contractor from any risk or from fulfilling all of the terms of his contract. The 552 SPECIFICATIONS accuracy of the interpretation of the facts disclosed by borings or other preliminary investigations is not guaranteed. Each bidder or his representative should visit the site of the work and familiarize himself with local conditions; failure to do so when intelligent preparation of bids depends on a knowledge of local conditions may be considered sufficient cause for rejecting a proposal. 20. Data to be Furnished by the Contractor. The contractor shall furnish the engineer reasonable facilities for obtaining such information as he may desire respecting the character of the materials and the progress and manner of the work, including all information necessary to determine its cost, such as the number of men employed, their pay, the time during which they worked on the various classes of construction, etc. The contractor shall also furnish the engineer copies of freight bills on all machinery, materials, and supplies shipped to or from the project in connection with the work under the contract. 21. Restrictions on Disposition of Plant, etc. The contractor shall not make any disposition of the plant, machinery, tools, appliances, supplies, materials, or animals used on or in connection with the work, either by sale, conveyance, or incumbrance, inconsistent with the special lien created by this contract. 22. Damages. The contractor will be held responsible for and required to make good, at his own expense, all damage to person or property caused by carelessness or neglect on the part of the contractor, or subcontractor, or the agents or employees of either. 23. Character of Workmen. The contractor shall not allow his agents or employ- ees, his subcontractors, or any agent or employee thereof, to trespass on premises or lands in the vicinity of the work. None but skilled foremen and workmen shall be employed on work requiring special qualifications, and when required by the engineer the contractor shall discharge any person who commits trespass or is in the opinion of the engineer disorderly, dangerous, insubordinate, imcompetent, or otherwise objectionable. Such discharge shall not be the basis of any claim for compensation or damages. 24. Methods and Appliances. The methods and appliances adopted by the contractor shall be such as will, in the opinion of the engineer, secure a satisfactory quality of work and will enable the contractor to complete the work in the time agreed upon. If at any time the methods and appliances appear inadequate, the engineer may order the contractor to improve their character or efficiency, and the contractor shall conform to such oroler; but failure of the engineer to order such improvement of methods or efficiency will not relieve the contractor from his obliga- tion to perform satisfactory work and to finish it in the time agreed upon. 25. Climatic Conditions. The engineer may order the contractor to suspend any work that may be subject to damage by climatic conditions. When delay is caused by an order to suspend work given on account of climatic conditions that could have been reasonably foreseen the contractor will not be entitled to any extension of time on account of such order. 26. Quantities and Unit Prices. The quantities noted in the schedule or pro- posal are approximations for comparing bids, and no claim shall be made for excess or deficiency therein, actual or relative. Payment at the prices agreed upon will be in full for the completed work and will cover materials, supplies, labor, tools, machinery, and all other expenditures incident to satisfactory compliance with the contract, unless otherwise specifically provided. CONTRACT SPECIFICATIONS 553 27. Removal and Rebuilding of Defective Work. The contractor shall remove and rebuild at his own expense any part of the work that has been improperly executed, even though it has been included in the monthly estimates. If he refuses or neglects to replace such defective work, it may be replaced at the expense of the contractor, and his sureties shall be liable therefor. 28. Protection of Work and Cleaning Up. The contractor shall be responsible for any material furnished him and for the care of all work until its completion and final acceptance, and he shall at his own expense replace damaged or lost material and repair damaged parts of the work, or the same may be done at his expense, and his sureties shall be liable therefor. He shall take all risks from floods and casualties and shall make no charge for detention from such causes. He may, however, be allowed a reasonable extension of time on account of such detention, subject to the conditions hereinbefore specified. The contractor shall remove from the vicinity of the completed work all plant, buildings, rubbish, unused material, concrete forms, etc., belonging to him or used under his direc- tion during construction, and in the event of his failure to do so the same may be removed at the expense of the contractor, and his sureties shall be liable therefor. 29. Roads and Fences. Roads subject to interference from the work covered by this contract shall be kept open, and the fences subject to interference shall be kept up by the contractor until the work is finished. 30. Bench Marks and Survey Stakes. Bench marks and survey stakes shall be established by the engineer and shall be preserved by the contractor, and in case of their destruction or removal by him or his employees, they will be replaced by the engineer at the contractor's expense, and his sureties shall be liable therefor. 31. Right of Way. The site for the installation of machinery or the right of way for the works to be constructed under this contract and for necessary borrow pits, channels, spoil banks, ditches, roads, etc., will be provided by 32. Sanitation. The engineer may establish sanitary and police rules and regu- lations for all forces employed under this contract, and if the contractor fails to enforce these rules the engineer may enforce them at the expense of the contractor. The use or sale of intoxicating liquor is absolutely prohibited on the work, except for medicinal purposes, and every such use or sale shall be under the direction and supervision of the engineer. 33. Infringement of Patents. The contractor shall hold and save and his officers, agents, servants, and employees harmless from and against all and every demand, or demands, of any nature or kind, for or on account of the use of any patented invention, article, or appliance included in the material or supplies hereby agreed to be furnished under this contract, and should the contrac- tor, his agents, servants, or employees, or any of them, be enjoined from furnishing or using any invention, article, material, or appliance supplied or required to be supplied or used under this contract, the contractor shall promptly substitute other articles, materials, or appliances in lieu thereof, of equal efficiency, quality, finish, suitability, and market value, and satisfactory in all respects to the engineer. Or, in the event that the engineer elects, in lieu of such substitution, to have sup- plied, and to retain and use, any such invention, article, material, or appliance, as may by this contract be required to be supplied, in that event the contractor shall pay such royalties and secure such valid licenses as may be requisite and necessary to enable his officers, agents, servants, and employees, or 554 SPECIFICATIONS any of them, to use such invention, article, material, or appliance without being disturbed or in any way interfered with by any proceeding in law or equity on ac- count thereof. Should the contractor neglect or refuse promptly to make the sub- stitution hereinbefore required, or to pay such royalties and secure such licenses as may be necessary and requisite for the purpose aforesaid, then in that event the engineer shall have the right to make substitution, or may pay such royalties and secure such licenses, and charge the cost thereof against any money due the contractor from or recover the amount thereof from him and his surety, notwithstanding final payment under this contract may have been made. The provisions of this paragraph do not apply to articles which the contractor is required to manufacture or furnish in accordance with detail drawings furnished by and included in this contract. They shall apply, however, where such drawings and the specifications cover only the type of device without restriction as to details. SPECIAL REQUIREMENTS 34. The Requirement. It is required that there be constructed and completed in accordance with these specifications and the drawings hereinbelow listed, (items) (feature) (project) (State). The work is near the line of the Railway and in the vicinity of the towns of 35. List of Drawings. 36. Commencement, Prosecution and Completion of Work. Work shall be commenced by the contractor within days, and shall be completed within days after the execution of the contract. The contractor shall at all times during the continuation of the contract prosecute the work with such force and equipment as, in the judgment of the engineer, are sufficient to complete it within the specified time. 37. Failure to Complete the Work in the Time Agreed upon. Should the con- tractor fail to complete the work or any part thereof in the time agreed upon in the contract, or in such extra time as may have been allowed for delays by formal extensions, a deduction of dollars per day for each schedule will be made for each and every day, including Sundays and holidays, that such schedule remains uncompleted after the date required for the completion. The said amounts are hereby agreed upon as liquidated damages for the loss to on account of all expenses due to the employment of engineers, inspectors and other employees after the expiration of the time for completion and OH account of the value of the operation of the works dependent thereon, and will be deducted from any money due the contractor under this contract, and the contractor and his sureties shall be liable for any excess. 38. Progress Estimates and Payments. At the end of each calendar month the engineer will make an approximate measurement of all work done and material delivered up to that date, classified according to items named in the contract, and will make an estimate of the value of the same on the basis of the unit prices named in the contract. To the estimate made as above set forth will be added the amounts earned for extra work to the date of the progress estimate. From SPECIAL REQUIREMENTS 555 the total thus computed a deduction of 10 per cent will be made and from the re- mainder there will be further deducted any amount due to from the contractor for supplies or materials furnished or services rendered and any other amounts that may be due to as damages for delays or otherwise under the terms of the contract. From the balance thus determined will be de- ducted the amount of all previous payments and the remainder will be paid to the contractor upon the approval of the accounts. The 10 per cent deducted as above set forth will become due and payable with and as a part of the final payment to be made as hereinafter provided. In case of the suspension of the con- tract, the said 10 per cent shall be and become the sole and absolute property of to the extent necessary to repay any excess in the cost of the work above the contract price. When the terms of the contract shall have been fully complied with to the satisfaction of the engineer, final payment will be made of any balance due, including the percentage withheld as above, or such portion thereof as may be due to the contractor. 39. Materials Furnished by the United States. All (list items) , required for the completion of the work in accordance with these speci- fications, will be furnished to the contractor by and will be delivered to him f. o. b. cars at the railway station most convenient to the work. The con- tractor shall haul all materials from the points of delivery to the work. He shall provide suitable warehouses for storing materials and will be charged for any mate- rial lost or damaged after delivery to him. He shall return to all unused material and will be charged for any material not used and not returned the same amounts that the material cost at the point of delivery to him. When material is furnished to the contractor on cars he shall be responsible for the prompt unloading of such material and will be held liable for any demurrage charges which may be incurred by his failure to unload the material promptly. The cost of unloading, hauling, handling, storing and caring for materials furnished by shall be included in the unit prices bid for the work in which the materials are to be used. STANDARD PARAGRAPHS FOR PURCHASE OF MATERIAL 40. Test Pieces. The contractor shall provide, at his own expense, the neces- sary test pieces, and shall notify the engineer or his representative when these pieces are ready for testing. All test bars and test pieces shall be marked so as to indicate clearly the material they represent, and shall be properly boxed and prepared for shipment if required. 41. Tests. Physical tests and chemical analyses of material will be made by at his own expense; or they may be made at the plant by the con- tractor or his employees, acting under the direction of the engineer or his repre- sentative; or certified tests may, at the option of the engineer, be accepted in lieu of the above-mentioned tests. 42. Shipment. All shipments shall be made to the points directed by the engineer. 43. Payment. per cent of the contract price of each shipment will be paid on the acceptance of the material by the inspector and receipt by the engineer at of the bill of lading, properly receipted, and the remainder shall be paid when all of the material covered by the contract shall have been received 556 SPECIFIC A TIONS at its destination and finally inspected, checked and accepted by the engineer, and the terms of the contract shall have been fully complied with to the satis- faction of the engineer. EARTHWORK ON CANALS 44. Classification of Excavation. All materials moved in the excavation of canals and for structures, and in the construction of embankments will be measured in excavation only, to the neat lines shown in the drawings or prescribed by the engineer, and will be classified for payment as follows: Class i : Material that can be plowed to a depth of 6 inches or more with a six- horse or six-mule team, each animal weighing not less than 1400 pounds, attached to a suitable plow, all well handled by at least three men; also all material that is loose and can be handled in scrapers, and all detached masses of rock, not exceeding 2 cubic feet in volume, occurring in loose material or material that can be plowed as specified. Class 2: Indurated material of all kinds that cannot be plowed as described under class i but that, when loosened by powder or other suitable means, can be removed by the use of plows and scrapers, and all detached masses of rock more than 2 and not exceeding 10 cubic feet in volume. Class 3: All rock in place not included in classes i and 2, and all detached masses of rock exceeding 10 cubic feet in volume not included in classes i and 2. If there be required the excavation of any material which, in the opinion of the engineer, cannot properly be included in any of the above three classes, the engineer will determine the actual necessary cost of excavating and disposing of such mate- rial and payment therefor as extra work will be made under the provisions of paragraph .... of these specifications. No additional allowance above, the prices bid for the several classes of material will be made on account of any of the material being frozen. It is desired that the contractor or his representative be present during the measurement of material excavated. On written request of the con- tractor, made by him within ten days after the receipt of any monthly estimate, a statement of the quantities and classifications between successive stations in- cluded in said estimate will be furnished him within ten days after the receipt of such request. This statement will be considered as satisfactory to the contractor unless he files with the engineer, in writing, specific objections thereto, with reasons therefor, within ten days after receipt of said statement by the contractor or his representative on the work. Failure to file such written objection with reasons therefor within said ten days shall be considered a waiver of all claims based on alleged erroneous estimate of quantities or incorrect classification of materials for the work covered by such statement. 45. Canal Sections. The canal sections are shown in the drawings, but the undetermined stability of the material that will form the canal banks may make it desirable during the progress of the work to vary the slopes and dimensions depen- ent thereon. Increase or decrease of quantities excavated as a result of such changes shall be covered in the estimates and shall not otherwise affect the payments due to contractor, unless it is found by the engineer that the unit cost is thereby increased, in which case the engineer will estimate, and include in the amount due the contractor the amount of such increase. The canal shall be excavated to the full depth and width required and must be finished to the prescribed lines and SPECIAL REQUIREMENTS 557 grades in a workmanlike manner. Runways shall not be cut into canal slopes below the proposed water level. Earth slopes shall be neatly finished with scrapers or similar appliances. Rock bottoms and banks must show no points of rock projecting more than 0.3 foot into the prescribed section. Above the water line the rock will be allowed to stand at its steepest safe angle and no finishing will be required other than the removal of rock masses that are liable to fall. Payment for excavation of canals will be made to the neat lines only as shown in the drawings or as established by the engineer. 46. Preparation of Surfaces. The ground under all embankments that are to sustain water pressure, and the surface of all excavation that is to be used for em- bankments, shall be cleared of trees, brush and vegetable matter of every kind. The roots shall be grubbed and burned with other combustible material that has been removed. The surface of the ground under the entire embankment shall be scored with a plow making open furrows not less than 8 inches deep below the natural ground surface at intervals of. not more than 3 feet. The cost of all work described in this paragraph shall be included in the unit-prices bid for excavation. 47. Construction of Embankments. Embankments built with teams and scrapers or with dump wagons shall be made in layers not exceeding 12 inches in thickness and kept as level as practicable. The travel over the embankments during construction shall be so directed as to distribute the compacting effect to the best advantage. Any additional compacting required over that produced by ordinary travel in distributing the material will be ordered in writing and paid for as extra work under the provisions of paragraph Embankments shall be built to the height designated by the engineer to allow for settlement, and shall be leveled on top to a regular grade. (Note: If the engineer proposes to permit the use of machinery in canal excavation full specifications should be drafted in each individual case.) No embankments shall be made from frozen materials nor on frozen surfaces. Should the engineer direct that unsuitable material be excavated and removed from the site of any embankment, the material thus excavated will be paid for as excavation. When canal excavation precedes the building of struc- tures, openings shall be left in the embankments at the sites of these structures and, except when the construction of the structures is included in the contract, the contractor will not be required to complete such omitted embankments. The cost of all work described in this paragraph, except as herein specified, shall be in- cluded in the prices bid for excavation. 48. Disposal of Materials. -All suitable material excavated in the construc- tion of canals and structures, or so much thereof as may be needed, shall be used in the construction of embankments and in backfilling around structures. Where the canal is on sloping ground, all material taken from the excavation shall be deposited on the lower side of the canal unless otherwise shown in the drawings or directed by the engineer. Where the canal is on level or nearly level ground, the material from the excavation shall be deposited in embankments on both sides to form the top portions of the waterway. If there is an excess of material in excava- tion it shall be used to strengthen the embankment on either side of the canal as may be directed by the engineer. Material taken from cuts that is not suitable for embankment construction and surplus material may be wasted on the right of way owned by , at such points as shall be approved by the engi- neer. Unless otherwise shown in the drawings or directed by the engineer, no 558 SPECIFICATIONS material shall be wasted in drainage channels, nor within feet of the edge of the prescribed or actual canal cut. On side hill locations all material wasted shall be placed on the lower side of the canal unless specific written authority is obtained from the engineer to waste such material elsewhere. Waste banks shall be left with reasonably even and regular surfaces. Whenever directed by the engineer, materials found in the excavation, such as sand, gravel or stone, that are suitable for use in structures, or that are otherwise required for special purposes, shall be preserved and laid aside in some convenient place designated by him. 49. Borrow Pits. Where the canal excavation at any section does not furnish sufficient suitable material for embankments, the engineer will designate where additional material shall be procured. Unless otherwise shown on the drawings or directed by the engineer a berm of 10 feet shall be left between the outside toe of the embankment and the edge of the borrow pit, with provision for a side slope of two to one to the bottom of the borrow pit. Borrowed material will be measured in excavation only, and unless the engineer gives the contractor specific written orders to excavate other than class i material from borrow pits, all material obtained from this source will be paid for at the unit price bid for class i excavation, regard- less of its actual character. Payment for excavation from borrow pits will be made for only such quantities as are required for embankments or backfilling or such as by direction of the engineer are excavated and wasted or laid aside. 50. Overhaul. All material taken from the excavation and required for em- bankment or for other purposes shall be placed as directed by the engineer. The limit of free haul will be 200 feet. Necessary haul over 200 feet will be paid for at the price bid per cubic yard per hundred feet additional haul, but no allowance will be made for overhaul where the excavated material is wasted, except where such overhaul is specifically ordered in w r riting by the engineer. Where material is taken from borrow pits, the length of the haul will be measured along the shortest practicable route between the center of gravity of the material as found in excava- tion and the center of gravity of the material as deposited in each station. Where the material is taken from canal excavation, the length of the haul shall be under- stood to mean the distance measured along the center line of the canal from the center of gravity of the material as found in excavation to the center of gravity of the material as required to be deposited. 51. Surface and Berm Ditches. If, in the judgment of the engineer, it should be necessary to construct surface and berm drainage ditches along the lines of the canal, the contractor shall perform such work and the excavation will be paid for at the unit prices bid in the schedules covering the excavation of the canal along which such surface and berm ditches are built. 52. Excavation for Structures. Unless otherwise shown in the drawings, excavation for structures will be measured for payment to lines outside of the foundation of the structures and to slopes of ; provided, that, where the character of the material cut is such that it can be trimmed to the required lines of the concrete structure and the concrete placed against the sides of the excavation without the use of intervening forms, payment for excavation will not be made outside of the required limits of the concrete. The prices bid for excavation shall include the cost of all labor and material for cofferdams and other temporary structures and of all pumping, bailing, draining and all other work necessary to maintain the excavation in good order during construction. SPECIAL REQUIREMENTS 559 53. Backfilling. The contractor shall place and shall compact thoroughly all backfilling around structures. The compacting must be equivalent to that obtained by the tramping of well distributed scraper teams depositing the mate- rial in layers not exceeding 6 inches thick when compacted. The material used for this purpose, the amount thereof and the manner of depositing the same must be satisfactory to the engineer. So far as practicable, the material moved in excavating for structures shall be used for backfilling, but when sufficient suitable material is not available from this source, additional material shall be obtained from borrow pits selected by the engineer. Payment for backfilling will be made at the price per cubic yard bid therefor in the schedule. 54. Puddling. Backfilling and embankment around structures within . . . .feet of the structure shall be made with material approved by the engineer, and where practicable shall consist of the sand and gravel, with an admixture of clay equal to one-fourth to one-half the volume of sand and gravel. The material shall be deposited in water of such depth as is approved by the engineer, unless the quantity of clay predominates, in which case the engineer may in his discretion order the material deposited in layers of 6 inches or less, and compacted by tamping or roll- ing with the smallest quantity of water that will insure consolidation. Payment for the work specified in this paragraph will be made at the unit price bid for pud- dling and will be in addition to the payment made for excavation and overhaul. 55. Blasting. Any blasting that will probably injure the work will not be permitted, and any damage done to the work by blasting shall be repaired by the contractor at his expense. CONCRETE 56. Composition. Concrete shall be composed of cement, sand and broken rock or clean gravel, well mixed and brought to a proper consistency by the addi- tion of water. Ordinarily one part by volume, measured loose, of cement shall be used with parts of sand and parts of broken rock or gravel. These proportions may be modified by the engineer as the work or the nature of the mate- rials used may render it desirable, and the contractor shall not be entitled to any extra compensation by reason of such modifications. 57. Cement. Cement for the concrete will be furnished to the contractor by as provided in paragraph The contractor shall give the engi- neer not less than thirty days' notice in writing of his cement requirements. The requirements shall be stated, so far as practicable, in quantities not less than single car lots. The contractor shall return to the railway station at , all empty sacks securely bound in bundles in such manner and of such sizes as the engineer may direct. For all sacks not returned in serviceable condition, he will be charged the same amount that the sacks cost. 58. Reinforcement Bars. Steel bars shall be placed in the concrete wherever shown in the drawings or prescribed by the engineer. The steel will be furnished to the contractor by as provided in paragraph The exact position and shape of reinforcement bars are not shown in all cases in the drawings accompanying these specifications, but the contractor will be furnished supple- mental detailed drawings and lists which will give him the information necessary for cutting, bending and spacing of bars. The steel used for concrete reinforcement shall be so secured in position that it will not be displaced during the deposition 560 SPECIFICATIONS of the concrete, and special care shall be exercised to prevent any disturbance of the steel in concrete that has already been placed. The cost of hauling, storing, cutting, bending, placing and securing in position of reinforcement bars shall be included in the unit price bid for placing reinforcement bars. 59. Sand. Sand for concrete may be obtained from natural deposits or may be made by crushing suitable rock. The sand particles shall be hard, dense, dur- able rock fragments, such as will pass a |-inch mesh screen. The sand must be free from organic matter and must not contain more than 10 per cent of clayey material. The sand must be so graded that when dry and well shaken its voids will not exceed 35 per cent. 60. Broken Rock or Gravel. The broken rock or gravel for concrete must be hard, dense, durable rock fragments or pebbles that will pass through a inch mesh screen when used for plain concrete, and through a inch mesh screen when used for reinforced concrete, and that will be rejected by a jj-inch mesh screen. 61. Water. The water used in mixing concrete must be reasonably clean and free from objectionable quantities of organic matter, alkali salts and other impuri- ties. 62. Mixing. The cement, sand and broken rock or gravel shall be so mixed and the quantities of water added shall be such as to produce a homogeneous mass of uniform consistency. Dirt and other foreign substance shall be carefully ex- cluded. Machine mixing will be required unless specific authority to use hand mixing is given by the engineer. The machine and its operation shall be subject to the approval of the engineer. Hand mixing, if permitted, shall be thorough and shall be done on a clean, tight floor. In general, enough water shall be used in mixing to give the concrete the consistency ordinarily designated as " wet." Concrete containing a minimum amount of water, ordinarily designated as " dry " concrete, will be permitted only where the nature of the work renders the use of " wet " concrete impracticable. If concrete is mixed in freezing weather, the materials shall be heated sufficiently .before mixing to remove all frost and main- tain a temperature above 32 F., until the concrete has been placed in the work and has attained its final set. 63. Placing. Concrete shall be placed in the work before the cement takes its initial set. The cement used in any concrete that is wasted or rejected will be charged to the contractor at its cost, at the point of delivery to him. No con- crete shall be placed in water except by permission of the engineer and the method of depositing the same shall be subject to his approval. Foundation surfaces upon which concrete is to be placed must be free from mud and debris. When the placing of concrete is to be interrupted long enough for the concrete to take its final set, the working face shall be given a shape, by the use of forms or other means, at the option of the engineer, that will secure proper union with subsequent work. All concrete surfaces upon or against which concrete is to be placed and to which the new concrete is to adhere, shall be roughened, thoroughly cleaned, and wet before the concrete is deposited. " Dry " concrete shall be deposited in layers not exceeding 6 inches in thickness, each of which shall be rammed until water appears on the surface. " Wet " concrete shall be stirred with suitable tamping bars, shovels or forked tools until it completely fills the form, closes snugly against all surfaces and is in perfect and complete contact with any steel used for rein- SPECIAL REQUIREMENTS 561 forcement. Where smooth surfaces are required a suitable tool shall be worked up and down next to the form until the coarser material is forced back and a mortar layer is brought next to the form. No concrete shall be placed except in the pres- ence of a duly authorized inspector. 64. Finishing. The surface of concrete finished against forms must be smooth, free from projections and thoroughly filled with mortar. Immediately upon the removal of forms all voids shall be neatly filled with cement mortar, irregularities in exposed surfaces shall be removed and minor imperfections of finish shall be smoothed to the satisfaction of the engineer. Exposed surfaces of concrete not finished against forms, such as horizontal or sloping surfaces, shall be brought to a uniform surface and worked with suitable tools to a smooth mortar finish. All sharp angles where required shall be rounded or beveled by the use of moulding strips or suitable moulding or finishing tools. 65. Protection. The contractor shall protect all concrete against injury. Exposed surfaces of concrete shall be protected from the direct rays of the sun and shall be kept damp for at least two weeks after the concrete has been placed. Concrete laid in cold weather shall be protected from freezing by such means as are approved by the engineer. All damage to concrete shall be repaired by the contractor at his expense, in a manner satisfactory to the engineer. 66. Forms. Forms to confine the concrete and shape it to the required lines shall be used wherever necessary. Where the character of the material cut into to receive a concrete structure is such that it can be trimmed to the prescribed lines, the use of forms will not be required. The forms shall be of sufficient strength and rigidity to hold the concrete and to withstand the necessary pressure and ram- ming without deflection from the prescribed lines. For concrete surfaces that will be exposed to view and for all other concrete surfaces that are to be finished smooth, the lagging of forms must be surfaced and bevel-edged or matched; provided, that smooth metal forms may be used if desired. All forms shall be removed by the contractor, but not until the engineer gives permission. Forms may be used repeatedly provided they are maintained in serviceable condition and thoroughly cleaned before being re-used. 67. Measurement. Concrete will be measured for payment to the neat lines shown in the drawings or prescribed by the engineer under these specifications. No payments will be made for concrete outside of the prescribed lines and in case cavities resulting from careless excavation are required to be filled with concrete, the cement used for such refilling will be charged to the contractor at its cost at the point of delivery to -him. 68. Payment. The unit price bid for concrete shall include all material and labor entering into its construction, except that cement will be furnished as pro- vided in paragraph . . . . , and reinforcement bars will be furnished when required as provided in paragraph STRUCTURAL STEEL Based on " Standard Specifications for Structural Steel for Buildings " of the American Society for Testing Materials, adopted August 25, 1913- 69. Manufacture. Structural steel may be made by either the open-hearth or Bessemer process. Rivet steel and plate or angle material over f inch thick, which is punched, shall be made by the open-hearth process. The steel shall 562 SPECIFICATIONS conform in all respects, not specifically mentioned herein, to the " Standard Specifications for Structural Steel for Buildings " of the American Society for Testing Materials, adopted August 25, 1913, and tests shall be made as provided in said specifications. 70. Chemical and Physical Properties of Structural Steel, Steel made by the Bessemer process shall contain not more than o.io per cent phosphorus and steel made by the open-hearth process shall contain not more than 0.06 per cent phos- phorus. All structural steel shall have an ultimate tensile strength of 55,000 to 65,000 pounds per square inch; an elastic limit, as determined by the drop of the beam, of not less than one-half the ultimate tensile strength; a minimum per cent of elongation in 8 inches of 1,400,000 divided by the ultimate tensile strength; a silky fracture; and capability of being bent cold without fracture 180 flat on itself for f-inch material and under; around a pin having a diameter equal to the thickness of the test piece for material over f inch to and including if inches; and around a pin having a diameter equal to twice the thickness of the test piece for material over i| inches in thickness. A deduction of i from the specified per- centage of elongation will be allowed for each f inch in thickness above f-inch; and a deduction of 2.5 will be allowed for each ^ inch in thickness below j^ inch. 71. Chemical and Physical Properties of Rivet Steel. Rivet steel shall contain not more than 0.06 per cent phosphorus nor more than 0.045 P er cen t sulphur. It shall have an ultimate tensile strength of 48,000 to 58,000 pounds per square inch; an elastic limit of one-half the ultimate tensile strength; a minimum per cent of elongation in 8 inches of 1,400,000 divided by the ultimate tensile strength; a silky fracture; and capability of being bent cold without fracture 180 flat on itself. 72. Finish. Finished material must be free from injurious seams, flaws, or cracks, and have a workmanlike finish. 73. Marking. Every finished piece of steel shall be stamped with the melt or blow number, except that small pieces may be shipped in bundles securely wired together with the melt or blow number on a metal tag attached. 74. Test Pieces. (See paragraph 40.) 75. Tests. (See paragraph 41.) 76. Payment. (See paragraph 43.) STEEL REINFORCEMENT BARS Based on " Standard Specifications for Billet-Steel Concrete Reinforcement Bars " of the American Society for Testing Materials, adopted August 25, 1913. 77. Manufacture. Steel may be made by either the open-hearth or Bessemer process and the bars shall be rolled from billets. It shall conform in all respects, not specifically mentioned herein, to the " Standard Specifications for Billet-steel Concrete Reinforcement Bars " of the American Society for Testing Materials adopted August 25, 1913, and tests shall be made as provided in said specifications. 78. Type of Bars. All reinforcement bars shall be of the deformed type. Bidders shall submit samples or cuts of the type of bar they propose to furnish. 79. Chemical Properties. Bars of steel made by the Bessemer process shall contain not more than o.io per cent phosphorus, and not more than 0.05 per cent phosphorus if made by the open-hearth process. SPECIAL REQUIREMENTS 563 80. Physical Properties. Bars of steel shall have an ultimate tensile strength of 55,000 to 70,000 pounds per square inch; an clastic limit of not less than 33,000 pounds per square inch; a minimum per cent of elongation in 8 inches of 1,250,000 divided by the ultimate tensile strength; and capability of being bent cold without fracture 180 around a pin having a diameter equal to the thickness of the test piece for material less than f inch in thickness, and around a pin having a diameter equal to twice the thickness of the test piece for material of | inch and over in thick- ness. For each increase of \ inch in diameter or thickness above f inch and for each decrease of -^ inch in diameter or thickness below ^ inch, a deduction of i will be allowed from the specified percentage of elongation. 81. Variation in Weight. Bars for reinforcement are subject to rejection if the actual weight of any lot varies more than 5 per cent over or under the theo- retical weight of that lot. 82. Finish. Finished material shall be free from injurious seams, flaws, or cracks, and shall have a workmanlike finish. 83. Test Pieces. (See paragraph 40). 84. Tests. (See paragraph 41.) 85. Payment. (See paragraph 43.) GRAY IRON CASTINGS Based on " Standard Specifications for Gray Iron Castings " of the American Society for Testing Materials, adopted September i, 1905. 86. Manufacture. Castings shall be of tough gray iron made by the cupola process. In all respects, not specifically mentioned herein the castings shall con- form to the " Standard Specifications for Gray Iron Castings " of the American Society for Testing Materials, adopted September i, 1901, and tests shall be made as provided in said specifications. 87. Light Castings, Physical and Chemical Properties. Castings having any section less than ^ inch thick shall be known as light castings. The sulphur con- tent shall be not greater than 0.08 per cent. The minimum breaking load of a bar i| inches in diameter, loaded at the middle of a 1 2-inch span, shall be 2500 pounds. The deflection shall in no case be less than o.i inch. 88. Heavy Castings, Physical and Chemical Properties. Castings in which no section is less than 2 inches thick shall be known as heavy castings. The sul- phur content shall be not greater than 0.12 per cent. The minimum breaking load of a bar i i inches in diameter, loaded at the middle of a 1 2-inch span shall be 3300 pounds. The deflection shall in no case be less than o.i inch. 89. Medium Castings, Chemical and Physical Properties. Medium castings are those not included under " light " or " heavy " castings. Their sulphur content shall be not greater than o.io per cent. The minimum breaking load of a bar 1 1 inches in diameter loaded at the middle of a 1 2-inch span shall be 2900 pounds. The deflection shall in no case be less than o.i inch. 90. Finish. All castings shall be true to pattern, free from cracks, flaws, porosity, cold-shuts, blow-holes and excessive shrinkage and shall have a work- manlike finish. 91. Test Pieces. (See paragraph 40.) 92. Tests. (See paragraph 41.) 93. Payment. (See paragraph 43.) 564 SPECIFICATIONS MALLEABLE CASTINGS Based on " Standard Specifications for Malleable Castings " of the American Society for Testing Materials, adopted November 15, 1904. 94. Manujacture. Malleable iron castings may be made by the open-hearth or air furnace process. In all respects not specifically mentioned herein the cast- ings shall conform to the " Standard Specifications for Malleable Castings " of the American Society for Testing Materials, adopted November 15, 1904, and tests shall be made as provided in said specifications. 95. Chemical and Physical Properties. Castings shall contain not more than 0.06 per cent of sulphur nor more than .0225 per cent of phosphorus. They shall have a tensile strength of not less than 40,000 pounds per square inch and the elonga- tion measured in 2 inches shall not be less than i\ per cent. The transverse strength of the standard test bar i inch square, loaded at the middle of a 1 2-inch span shall be not less than 3000 pounds per square inch; and the deflection shall be at least \ inch. 96. Finish. Castings shall be true to pattern, free from blemishes, scale and shrinkage cracks, and shall have a workmanlike finish. 97. Test Pieces. (See paragraph 40.) 98. Tests. (See paragraph 41.) 99. Payment. (See paragraph 43.) STEEL CASTINGS Based on " Standard Specifications for Steel Castings " of the American Society for Testing Materials, adopted August 25, 1913. 100. Manufacture. Steel for castings may be made by the open-hearth, crucible or Bessemer process. Castings shall be annealed unless otherwise speci- fied, and in all respects not specifically mentioned herein their material and manu- facture shall conform to the Standard Specifications for Steel Castings of the Amer- ican Society for Testing Materials adopted August 25, 1913, and tests shall be made as provided in said specifications. 101. Chemical and Physical Properties. Castings shall contain not more than 0.05 per cent of phosphorus nor more than 0.05 per cent of sulphur. Castings shall be classed as " Hard," " Medium " and " Soft " and shall have the following physical properties: Hard. Medium. Soft. Tensile strength, pounds per square inch 80,000 70,000 60,000 Elastic limit 36,000 31,500 27,000 Elongation, per cent in 2 inches 15 18 22 Contraction of area, per cent 20 25 30 102. Finish. Casting shall be true to pattern, free from blemishes, flaws or shrinkage cracks. Bearing surfaces shall be solid and no porosity shall be allowed in positions where the resistance and value of the casting for the purpose intended will be seriously affected thereby. 103. Test Pieces. (See paragraph 40.) 104. Tests. (See paragraph 41.) 105. Payment. (See paragraph 42.) SPECIAL REQUIREMENTS 565 CEMENT 106. The Requirement. It is required that there be furnished in accordance with these specifications the quantity of Portland cement set forth in the accom- panying advertisement, f. o. b. cars at the place named by the bidder in his pro- posal. The right is reserved by to increase or decrease the quantity to an extent not to exceed 20 per cent. The contractor shall store cement in suf- ficient quantities to provide for the completion of necessary tests thereon before shipment is required. 107. Progress Estimates and Payments. At the end of each calendar month the engineer will prepare a statement of the amount of cement delivered to that date and an estimate of the value of the same on the basis of the unit .price named in the contract. From the total thus computed there will be deducted any amount due from the contractor under the terms of the contract. From the amount thus determined will be deducted the sum of all previous payments and the remainder will be paid to the contractor on approval of the accounts. 108. Definition. The cement shall be the product obtained by finely pulver- izing clinker produced by calcining to incipient fusion, an 'ntimate mixture of prop- erly proportioned argillaceous and calcareous substances, with only such additions subsequent to calcining as may be necessary to control certain properties. Such additions shall not exceed 3 per cent, by weight, of the calcined product. 109. Composition. In the finished cement, the following limits shall not be exceeded : Loss on ignition for 15 minutes 4 per cent Insoluble residue i " Sulphuric anhydride (SO 5 ) 2 " Magnesia (MgO) 5 " no. Specific Gravity. The specific gravity of the cement shall be not less than 3.10. Should the cement as received fall below this requirement, a second test may be made upon a sample heated for thirty minutes at a very dull red heat. in. Fineness. At least 78 per cent of the cement by weight, shall pass through the No. 200 sieve. 112. Soundness. Pats of neat cement prepared and treated as hereinafter prescribed shall remain firm and hard and show no sign of distortion, checking, cracking, or disintegrating. If the cement fails to meet the prescribed steaming test, the cement may be rejected or the steaming test repeated after seven or more days at the option of the engineer. 113. Time of Setting. The cement shall not acquire its initial set in less than forty-five minutes and must have acquired its final set within ten- hours. 114. Tensile Strength. Briquettes made up of i part cement and 3 pnrts stand- ard Ottawa sand, by weight, shall develop tensile strength per square inch as fol- lows: After 7 days, i day in moist air, 6 days in water 200 pounds After 28 days, i day in moist air, 27 days in water 300 " The average of the tensile strengths developed at each age by the briquettes in any set made from one sample is to be considered the strength of the sample 566 SPECIFICATIONS at that age, excluding any results that are manifestly faulty. The average strength of the briquettes at 28 days shall show an increase over the average strength at 7 days. 115. Brand. Bids for furnishing cement or for doing work in which cement is to be used shall state the brand of cement proposed to be furnished and the mill at which made. The right is reserved to reject any cement which has not established itself as a high-grade Portland cement, and has not been made by the same mill for two years and given satisfaction in use for at least one year under climatic and other conditions at least equal in severity to those of the work proposed. 116. Packages. The cement shall be delivered in sacks, barrels, or other suit- able packages (to be specified by the engineer), and shall be dry and free from lumps. Each package shall be plainly labeled with the name of the brand and of the man- ufacturer. A sack of cement shall contain 94 pounds net. A barrel shall con- tain 376 pounds net. Any package that is short weight or broken or that contains damaged cement may be rejected, or accepted as a fractional package, at the option of the engineer. If the cement is delivered in cloth sacks, the sacks used shall be strong and serviceable and securely tied, and the empty sacks will, if practicable, be returned to the contractor at the point of delivery of the cement. On final settlement under the contract, cents will be paid the contractor for each sack furnished by him in accordance with the above requirements and not returned in serviceable condition. 117. Inspection. The cement shall be tested in accordance with the standard methods hereinafter prescribed. In general the cement will be inspected and tested after delivery, but partial or complete inspection at the mill may be called for in the specifications or contract. Tests may be made to determine the chemical composition, specific gravity, fineness, soundness, time of setting, and tensile strength, and a cement may be rejected in case it fails to meet any of the specified requirements. An agent of the contractor may be present at the making of the tests or they may be repeated in his presence. CONTINUOUS WOOD STAVE PIPE 118. Description. The pipe shall be of the continuous-stave metal-banded type with metal tongues driven into slots in the ends of the staves to form the butt joints. The alinement and profile of the pipe are shown in the drawings. Each proposal shall be accompanied by drawings showing clearly detail dimensions of staves, bands and tongues, which shall comply with the requirements of the speci- fications. Omission of drawings from proposals or any uncertainty as to detail dimensions will be sufficient cause for rejection. 119. Material. All material of whatever nature required in the work shall be furnished by the contractor. The price bid for wood staves in place shall include the cost of all necessary tongues, and all royalties for special material or devices used in the pipe or in its construction. The price bid for bands in place shall include all necessary shoes and fastenings and asphaltum coating, and all royalties for special devices used in the pipe or in its construction. 120. Diameter of Pipe. The inside diameter of the pipe shall be inches, measured after completion of the work. No diameter at any point shall differ more than 2 per cent from the average diameter of the pipe at said point, and SPECIAL REQUIREMENTS 567 the average of the vertical and horizontal diameters at any point shall not be less than the specified diameter. 121. Staves. All lumber used in staves shall be Douglas fir or redwood. It shall be sound, straight-grained, and free from dry rot, checks, wind shakes, wane, and other imperfections that may impair its strength or durability. Redwood shall be clear and free from sap. In Douglas fir sap will not be allowed on more than 10 per cent of the inside face of any stave and in not more than 10 per cent of the total number of pieces; sap shall be bright and shall not occur within 4 inches of the ends of any piece; pitch seams will be permitted in not over 10 per cent of the total number of pieces, if showing on the edge only, and if not longer than 4 inches nor wider than YS inch; no through knots nor knots at edge nor within 6 inches of ends of staves will be allowed; sound knots not exceeding | inch in diameter, not falling within the above limitations, nor exceeding three within a lo-foot length will be accepted. All lumber used shall be seasoned by not less than sixty days' air drying in open piles before milling or by thorough kiln drying. All staves shall have smooth planed surfaces and the inside and outside faces shall be accurately milled to the required circular arcs to fit a standard pattern provided by the contractor. Staves shall be trimmed perfectly square at ends and the slots for tongues shall be in exactly the same relative position for all ends and according to detail drawings furnished by the contractor. Staves shall have an average length of not less than 15 feet 6 inches and not more than i per cent of the staves shall have a length of less than 9 feet 6 inches. No staves shorter than 8 feet will be accepted. The finished thickness of staves shall not be less than inches. All staves delivered on the work in a bruised or injured condition will be rejected. If staves are not immediately used on arrival at the site of the work, they shall be kept under cover until used. 122. Bands. A band shall consist of one complete fastening and shall include the bolts, shoes, nuts and washers necessary to form same. 123. Band Spacing. The distance center to center of bands shall be as marked on the profile, except that where the spacing as marked is such as to make the dis- tances from bands to the ends of staves more than 4 inches extra bands shall be used to keep such distances within 4 inches. 124. Bolts. All bolts shall be of inch diameter steel and shall conform to the following specifications: (See specifications for structural steel.) Bolts may have either button or bolt heads. They shall be at least as strong in thread as in body and threads shall permit the nut to run freely for the entire length of thread. Nuts shall be of such thickness as to insure against stripping of threads. 125. Shoes. There shall be malleable iron shoes to each band. Shoes shall fit accurately to the outer surface of the pipe and shall have the dimensions shown on the drawing, or the contractor may submit for approval a drawing or sample of some other type of shoe which he may desire to furnish. If required, such shoe shall be shown under suitable test to be stronger than the bolt. The material for shoes shall conform to the following specifications: (See standard specifications for malleable castings.) 126. Tongues. Shall be of galvanized steel or iron inch thick and ... ... wide. Their length shall be such, that when in place, they will penetrate into the sides of the adjacent staves without undue injury. The tongues and slots shall be 568 SPECIFICATIONS so proportioned as to insure a tight fit of the tongues into the slots without danger of splitting the staves. 127. Coating of Bands. The bands shall be coated by being dipped when hot in a mixture of pure California asphalt, or equivalent. Bolts shall be bent to the required arc before dipping. If the bands are dipped cold they shall be left in the hot bath a sufficient length of time to insure that they have acquired the tem- perature of the asphalt. This coating shall be so proportioned and applied that it will form a thick and tough coating free from tendency to flow or become brittle under the range of temperature to which it will be subjected. Where the pipe is uncovered and exposed to the full range of atmospheric temperatures, not less than 7 per cent and not more than 10 per cent of pure linseed oil shall be mixed with the asphalt. 128. Erection. The pipe shall be built in a workmanlike manner. The ends of adjoining staves shall break joint at least 3 feet. The staves shall be driven in such a manner as to avoid any tendency to cause wind in the pipe and the required grade and alinement must be maintained. Staves shall be well driven to produce tight butt joints, driving bars or other suitable means being used to avoid marring or damaging staves in driving. In rounding out the pipe, care shall be exercised to avoid damage by chisels, mauls or other tools. The pipe shall be rounded out to produce smooth inner and outer surfaces. Bands shall be accurately spaced and placed perpendicular to the axis of the pipe. Shoes shall be placed so as to cover longitudinal joints between staves and bear equally on two staves as nearly as practicable. They shall be placed alternately on opposite sides of the pipe so as to be out of line and cover successively on each side at least three joints. Shoes shall not be allowed to cover the butt joints. Bolts shall be hammered thoroughly into the wood to secure a bearing on 60 degrees of the circumference of the bolt. All kinks in bolts shall be carefully hammered out. Bands shall be back-cinched to the satisfaction of the engineer so as to produce the required initial compressive stresses in the staves. All metal work shall be handled with reason- able care so as to avoid injury to the coating as much as possible. In hammer- ing shoes into place they shall be struck so as to avoid deformation or injury. After erection the contractor shall retouch all metal work, where abraded, with an asphaltum paint satisfactory to the engineer. 129. Painting. After erection and while the pipe is dry the entire outer surface shall be given a coat of refined water-gas tar, followed by a coat of refined coal-gas tar, thinned with distillate, applied with brushes or sprayed on with air pressure. Before application of the paint the surface of the pipe shall be thoroughly cleaned of dirt, dust and foreign matter of every kind. All checks, cracks and sur- face irregularities of every kind shall be thoroughly filled with paint. The finished thickness of the coating shall be not less than ^ inch. The cost of all work under this paragraph shall be included in the price bid for pipe in place. 130. Inspection. Final inspection of materials, as well as erection will be made on the work, but if the contractor so desires, preliminary inspection of staves may be made at the mill at the contractor's expense. Mill inspection, however, shall not operate to prevent the rejection of any faulty material on the work. Tests of metal work will be made at the point of manufacture by at his own expense; or they may be made at the plant by the contractor or his employees acting under the direction of the engineer or his representative; or certified tests SPECIAL REQUIREMENTS 569 may, at the option of the engineer, be accepted in lieu of the above-mentioned tests. The contractor shall provide, at his own expense, the necessary test pieces, and shall notify the engineer or his representatives when these pieces are ready for testing. All test bars and test pieces shall be marked so as to indicate clearly the material that they represent, and shall be properly boxed and prepared for ship- ment if required. 131. Tests of Pipe. On completion of the work, or as soon as possible there- after, the contractor shall make a full pressure test of the pipe, water being furnished therefor by ............ All leaks found at the time of the test shall be made tight by the contractor. If the leakage is not so large as to endanger the founda- tion of the pipe, the pipe shall be kept under full pressure for two days before plug- ging of leaks is started in order to allow the wood to become thoroughly saturated. The cost of making the test, except furnishing water, shall be borne by the con- tractor. 132. Payments. At the end of each calendar month 50 per cent of the price for material in place shall be paid to the contractor for material delivered on the work; 25 per cent additional shall be paid after erection and preliminary cinching; and the remainder shall be paid after final test and acceptance of the pipe by the engineer and when the terms of the contract shall have been fully complied with to the satisfaction of the engineer, and a release of all claims against .............. , under, or by virtue of the contract, shall have been executed by the contractor. MACHINE BANDED WOOD STAVE PIPE 133. Description. The pipe shall be of the jointed, wood-stave, machine banded type. 134. Lengths of Pipe Sections. Pipe shall be furnished in lengths of 10 to 20 feet and the average length shall be not less than 16 feet. Shorter sections shall be furnished only if required for making sharp curves in which case the lengths shall not be more than i foot shorter than will be required to keep the joint opening at the outside of the cur/e due to throw within a limit of Y inch. 135. Material. All material of whatever nature required in the manufacture of the pipe in accordance with these specifications shall be furnished by the con- tractor. 136. Diameter of Pipes. The diameters of pipes shsdl be as listed in the sched- ules. No diameter of any pipe shall differ more than i per cent from the specified diameter of the pipe, and the average of the vertical and horizontal diameters at any point shall not be less than the specified diameter. 137. Thickness of Staves. The finished thickness of staves shall be as follows: 4 to 6 inches I -J 8 to 10 " ll I 2 tO 14 ' ' 16 to 18 " ... jl 2O tO 24 " . Il 5 138. Lumber for Staves. All lumber used in staves shall be Douglas fir or red- wood. It shall be sound, straight-grained, and free from dry rot, checks, wind 570 SPECIFICATIONS shakes, wane and other imperfections that may impair its strength or durability. Redwood shall be clear and free from sap. In Douglas fir sap will not be allowed on more than 10 per cent of the inside face of any stave and in not more than 10 per cent of the total number of pieces; sap shall be bright and shall not occur within 4 inches of the ends of any piece; pitch seams will be permitted in not over 10 per cent of the total number of pieces, if showing on the edge only, and if not longer than 4 inches nor wider than Y& inch; no through knots or knots at edges or within 6 inches of ends of staves will be allowed; sound knots not exceeding \ inch in diameter, not falling within the above limitations, nor exceeding three within a lo-foot length will be accepted. All lumber used shall be seasoned by not less than sixty days' air drying in open piles before milling or by thorough kiln drying. All staves shall have smooth planed surfaces and the inside and outside faces shall be accurately milled to the required circular arcs. 139. Banding. Size and spacing of banding wire shall be adjusted for a working stress of 12,000 pounds per square inch on the wire. The spacing shall in no case be greater than 4 inches center to center of wires, nor greater than will produce a pressure of wire on the wood of 800 pounds per square inch as calculated from the pRf formula B= /n_,\> where B = pressure on wood in pounds per square inch; p = water pressure in pounds per square inch; /= spacing of wire in inches; R = inside radius of pipe in inches; r radius of wire in inches; and / = thickness of staves in inches. No wire smaller than No. 8 U. S. Standard gage shall be used. Wire shall be of medium steel double-galvanized and shall have an ultimate tensile strength of 55,000 to 65,000 pounds per square inch, and capability of being bent flat on itself without fracture. The bidder shall state in his proposal the size of banding wire he proposes to furnish. 140. Joints. Inserted joint pipe shall be furnished for diameters of 12 inches and less and for heads not exceeding 50 feet. For pipes of larger diameter than 12 inches and for all pipes under more than 50 feet head, wood sleeve collars shall be furnished. The banding on collars shall be 50 per cent stronger than the banding on the pipe. 141. Individual Bands. Individual bands shall be used on all collars for pipe 1 2 inches and greater in diameter. The smallest bolts used shall be f inch in diam- eter. The bolt shall have an ultimate tensile strength of 55 ; ooo to 65,000 pounds per square inch; an elastic limit of one-half the ultimate tensile strength and capability of being bent back flat on itself without fracture. The shoes shall be malleable iron and shall be stronger than the bolts, with sufficient bearing on the wood at the tail to prevent injurious indentation in cinching. The shoes shall be sound and free from blow-holes, and shall have an ultimate tensile strength of not less than 40,000 pounds per square inch. Bidders shall submit samples or drawings of the type of shoe they propose to furnish. 142. Coating. After manufacture the outside of the pipe and collars shall be dipped in a bath of hot coal tar and asphaltum. Previous to dipping the collars in coal tar and asphaltum they shall be dipped for a depth of i inch at each end for a period of ten minutes in a bath of creosote. Care should be exercised to keep the coal tar and asphaltum from the tenon ends and inside surfaces and, if neces- sary, the tenons shall be wrapped with paper while being dipped. After dipping the pipe and collars shall be rolled in fine sawdust while the coating is still soft. SPECIAL REQUIREMENTS 571 143. Inspection. Inspection of pipe will be made at the mill, but the manufac- turer will be held responsible for any damage in transit caused by improper loading of the pipe. 144. Marking. Each section of pipe shall be plainly marked on the inside at one end, showing the head for which the section was wound, and the number of the banding wire used. LAYING MACHINE BANDED WOOD STAVE PIPE 145. Point of Delivery. Pipe will be delivered f. o. b. cars at in lengths of 12 to 20 feet. The contractor shall unload cars at once and will be held responsible for all demurrage charges. 146. Handling. In unloading and hauling, the pipe shall be handled carefully. To avoid injury to the ends, the pipe should not be carried by means of sticks inserted in the ends. The contractor will be held responsible for any damage due to careless handling. 147. Laying. The pipe should be laid with coupling or mortise end in the direction of the laying. Care should be taken in inserting the tenon to see that it is started around the entire circumference and the joint should first be driven lightly until it is assured that a good connection is being made, then drive to the shoulder. The bands on couplings should not be fully cinched until the joint has been driven home. The bands on couplings should be placed symmetrically about the middle of the coupling and in cinching a few turns should be given alter- nately to each band in order to maintain approximately the same tension on each. 148. Alincment and Grade. In laying the pipe true alinement and. grade must be maintained. If necessary, short sections of pipe shall be used for making sharp curves and the pipe shall be anchored by staking the outside at each joint. Curves shall be made by driving the joint on a tangent and then springing into place. 149. Fittings. Elbows, tees and other special fittings shall be securely anchored in concrete as directed by the engineer. 150. Tests. After the pipe has been laid it shall be subjected to tne full pres- sure of water and the contractor shall stop all leaks. Damages to the pipe caused by the pressure of water, that are due to improper or careless laying shall be repaired by the contractor, but he shall not be responsible for damages due to defec- tive manufacture. If the leakage is not so large as to endanger the foundation of the pipe, it shall be kept under full pressure for two days before plugging of leaks is started in order to allow the wood to become thoroughly saturated. Water for tests will be furnished by , but the expense of making the test, except furnishing water, shall be borne by the contractor. 151. Payments. On the completion of a pipe line per cent of the con- tract price, on the basis of the unit price bid per linear foot of pipe in place, will be made. The remainder will be paid after final test and acceptance of the pipe by the engineer, and when the terms of the contract shall have been fully complied with to the satisfaction of the engineer, and a release of all claims against .... under, or by virtue of the contract, shall have been executed by the con- tractor. 572 SPECIFICATIONS STEEL PIPE 152. Description. Steel pipe may be either of the lockbar or riveted steel type. Riveted steel pipe shall have < I courses. Circular seams may i taper j { triple \ ^ I double shall submit with his bid a drawing showing details of joints, size and spacings of rivets, etc. Failure to submit such drawing will be sufficient cause for rejection of the bid. 153. Thickness of Metal. The thickness of steel sheets shall be as follows: Length, Feet. Thickness, Inches. Head, Feet. Riveted. Lockbar. 154. Planing and Scarfing. When necessary the edges of plates shall be pre- pared for caulking by planing and scarfing at the factory. 155. Riveting. The riveting and other details of longitudinal seams shall be designed to withstand the heads given in paragraph 198. The rivets for cir- cular joints shall be of the same size as for longitudinal seams. The intensity of working stress on rivets shall be 7500 pounds per square inch in shear and 15,000 pounds per square inch in bearing on riveted plates. All rivet spacing shall be arranged to give the greatest possible efficiency of joint. Size of rivets and rivet spacing shall be submitted to the engineer for approval. All riveting shall be done in the field, but sufficient of the work done with different templates must be assembled at the shop to prove the work correct. (When appropriate shop rivet- ing should be specified.) 156. Punching. Rivet holes may be punched and shall be no larger than is necessary to pass the required size of rivet. Drift pins shall not be used except for bringing together the several parts, and drifting with such force as to distort the holes will not be allowed. Wrongly punched plates shall not be corrected by plugging the holes and a re-punching, but shall be rejected. All burrs and ragged edges on plates shall be smoothed off before leaving the shop. All punching shall be done at the shop before shipment. 157. Material. All steel shall be made by the open-hearth process. Steel for plates shall be of the grade known as " boiler plate." Steel for rivets shall be of the grade known as " boiler rivet steel." SPECIAL REQUIREMENTS 573 158. Chemical and Physical Properties of Boiler Plate Steel. Boiler plate steel shall contain not more than .05 per cent phosphorus, .05 per cent sulphur, and from 0.30 to 0.60 per cent manganese. It shall show an ultimate tensile strength of 55,000 to 65,000 pounds per square inch; an elastic limit of not less than one-half the ultimate tensile strength; an ultimate elongation in 8 inches of not less than 1,500,000 divided by the ultimate tensile strength; and capability of being bent, cold or quenched, 180 flat without fracture. The steel shall be in all respects such as to stand punching, caulking and riveting without showing the least tendency to crack. Plates shall withstand, without cracking of the material, a drift test made by driving a pin into a f-inch hole, enlarging same to a diameter of i inch. In all respects not covered in these specifications boiler plate steel shall conform to the " Standard Specifications for Boiler Steel " of the American Society for Testing Materials, adopted August 25, 1913. 159. Chemical and Physical Properties of Rivet Steel. Steel for rivets shall con- tain not more than 0.04 per cent of phosphorus, 0.45 per cent sulphur, and from 0.30 to 0.50 per cent of manganese. It shall show an ultimate tensile strength of 45,000 to 55,000 pounds per square inch; an elastic limit of not less than one-half the ultimate tensile strength; an ultimate elongation in 8 inches of not less than 1,500,000 divided by the ultimate tensile strength, but need not exceed 30 per cent; and capability of being bent, cold or quenched, 180 flat without fracture. Rivet rounds shall be tested of full size as rolled. In all respects not covered in these specifications steel for rivets shall conform to the " Standard Specifications for Boiler Rivet Steel " of the American Society for Testing Materials, adopted August 25, 1913. 1 60. Marking. Each plate shall be distinctly stamped with its melt or slab number. Rivet steel may be shipped in securely fastened bundles with melt number stamped on a metal tag attached. Plates and other parts shall be plainly marked for identification and assembly in the field. 161. Test Pieces. (See paragraph 40.) 162. Test of Material. (See paragraph 41.) 163. Erection. Erection of pipe shall be commenced at the point directed by the engineer. The contractor shall haul all material and distribute same along the trench and shall furnish a compressed air plant and full equipment for air rivet- ing, and all other equipment, tools and supplies required for the erection of the pipe and completion for service. The pipe shall be carefully caulked and painted as the work progresses. The work of assembling, riveting and caulking shall be done by workmen experienced in this line. Riveting shall show first class workmanship, rivet heads shall be full and concentric with the body of the rivet, and the rivet shall completely fill the hole and thoroughly pinch the connected pieces together. Rivets that are loose or have defective heads shall be removed and other rivets substituted therefor. 164. Painting. Inside and outside of pipe shall be covered with three coats of a reliable brand of asphalt paint which shall be subject to the approval of the engineer. Before painting all surfaces shall be thoroughly cleaned by scrubbing with wire brushes or other means as directed by the engineer. All riveted joints shall be painted before riveting. All paint shall be applipd while the pipe is warm and thoroughly dry. 165. Defective Work. The contractor shall guarantee the material and work- 574 SPECIFICATIONS manship furnished by him to he free from defects of material and construction, and he shall replace free of cost to any material that shall develop faults during construction or tests. 166. Test of Pipe. On completion of erection, or as soon as possible thereafter, the contractor shall make a full pressure test of the pipe, water therefor being furnished by The pipe shall be water-tight under this test and the contractor shall correct any defects that develop. JOINTED REINFORCED CONCRETE PIPE 167. Description. The pipe shall be composed of concrete reinforced with steel rods or wire and built in vertical forms in lengths of feet; the sections being connected in the trench by concrete collars reinforced with steel. 1 68. Diameter of Pipe. The inside diameter of the pipe shall be inches and no diameter shall differ more than 0.5 per cent from the specified diameter of the pipe. Each section of pipe shall be a true right cylinder with the plane of the ends perpendicular to the axis of the pipe. 169. Thickness of Shell. The shell of the pipe shall have a thickness of inches which shall be uniform around the entire circumference. In no case will a variation of more than 10 per cent from the specified thickness be allowed. 170. Manufacture. The concrete shall be thoroughly mixed in a mechanical batch mixer. It shall be deposited in such a manner that no separation of ingre- dients will occur and suitable tools shall be used to thoroughly settle the concrete and produce smooth surfaces. Great care shall be exercised to maintain proper spacing of the reinforcing rods. No pipe shall be manufactured when the tempera- ture of the atmosphere is above 90, except by permission of the engineer. During manufacture the concrete and forms shall be protected from the direct rays of the sun, and for five days thereafter the sections shall be kept both moist and cov- ered, and they shall be kept moist for fifteen days additional. Manufacture shall not be carried on in freezing weather, except in a heated enclosure and the sections of pipe shall be prevented from freezing. Immediately after removal of the forms all defects in the surface of the concrete shall be smoothed up with a i to i mixture of cement and fine sand, especial care being taken to produce smooth interior surfaces. Forms shall not be removed in less than twenty-four hours after the concrete has been poured. 171. Forms. The forms used shall be subject to the approval of the engineer. All steel forms are preferred, but wooden forms with steel linings may be used pro- vided the desired results can be obtained therewith. Forms shall be strong and rigid with sufficient bracing to prevent warping in handling, or pouring concrete. They shall be provided with suitable attachments for making the joint grooves at the ends in accordance with the drawings. A sufficient number of forms shall be provided to allow the manufacture of not less than sections of pipe per day, or such additional number as may be necessary to complete the work within the specified time. 172. Reinforcement. The transverse reinforcement shall consist of medium steel rods or wire and shall be spaced as shown on the drawings. Sufficient longi- tudinal reinforcement shall be used to fasten the transverse rods and hold them rigidly in place. The transverse reinforcement may be either individual rods SPECIAL REQUIREMENTS 575 welded or lapped and wired at the ends for a length of 24 diameters, or it may be wound in helical coils. The latter method is preferred where its use is practicable. 173. Steel. Steel may be made by either the open-hearth or Bessemer process. It shall contain not more than o.i per cent phosphorus if made by the Bessemer process and not more than 0.05 per cent if made by the open-hearth process. It shall have an ultimate tensile strength of 55,000 to 70,000 pounds per square inch; an elastic limit not less than 33,000 pounds per square inch; a minimum per cent of elongation in 8 inches of 1,400,000 divided by the ultimate tensile strength; and capability of being bent cold without fracture 180 around a pin having a diameter equal to the thickness of the test piece. Bars or wire will be subject to rejection if the actual weight of any lot varies more than 5 per cent over or under the theoretical weight of that lot. 174. Concrete. Concrete shall be composed of cement, sand and gravel, well mixed and brought to a proper consistency by the addition of water. The pro- portions will depend upon the nature of component materials and upon the head of water that the pipe will be subjected to, but will vary in general from one part cement to five parts aggregate, to one part cement to six parts of aggregate. The contractor shall not be entitled to any extra compensation by reason of such vari- tions. 175. Cement. Cement for concrete will be furnished to the contractor. The contractor shall give the engineer not less than thirty days' notice in writing of his cement requirements, which shall be stated, so far as practicable in quantities not less than single car lots. The contractor shall return to the railway station at all empty sacks securely bound in bundles in such a manner and of such sizes as the engineer may direct. For all sacks not returned in serviceable condition he will be charged the same amount that the sacks cost The contractor shall provide suitable warehouses for storing the cement and he will be charged at the same price that it cost for all cement wasted and damaged after delivery to him, and also for all unused cement not returned. 176. Sand. Sand for concrete shall be obtained from natural deposits. The particles shall be hard, durable, non-organic rock fragments, such as will pass a j-inch mesh screen. The sand must be free from organic matter and must contain not more than 10 per cent of clayey material. The sand must be so graded that, when dry and well shaken its voids will not exceed 35 per cent. 177. Gravel. Gravel for concrete shall consist of hard, durable rock pebbles that will pass through a inch mesh screen and that will be rejected by a j-inch mesh screen. 178. Water. The water used in mixing concrete shall be reasonably clean, and free from objectionable quantities of organic matter, alkali salts and other im- purities. 179. Mixing. The cement, sand and gravel shall be so mixed and the quan- tities of water added shall be such as to produce a homogeneous mass of uniform consistency. Dirt and other foreign substances shall be carefully excluded. Machine mixing will be required, and the machine and its operation shall be sub- ject to the approval of the engineer. Enough water shall be used to give the con- crete a mushy consistency. If concrete is mixed in freezing weather the sand and gravel or water shall be heated sufficiently before mixing to remove all frost. 180. Placing. No concrete shall be used that has attained its initial set. and 576 SPECIFICATIONS such concrete shall be immediately removed from the site of the work. No con- crete shall be placed except in the presence of a duly authorized inspector. 181. Hauling. In handling and hauling the sections of pipe great care shall be taken to avoid injury to the pipe and suitable cradles shall be provided to avoid concentration of the entire weight on small areas. The sections of pipe shall be distributed along the trench as directed by the engineer. Any pipes that are seriously injured in handling or hauling will be rejected and shall be immediately removed from the site of the work or demolished and the contractor shall replace the same with other sections of pipe having the same quantitiy of reinforcement. 182. Laying. The sections of pipe shall laid be true to line and grade accord- ing to stakes established by the engineer and with only sufficient joint space between to allow for satisfactory caulking. Before making the joints the adjacent sections of pipe shall be firmly bedded or supported by blocks to prevent the slightest movement while the joint is being made. 183. Joints. Joints may be made by sectional collars separately moulded and set in grooves in the ends of the pipe sections, or by pouring concrete on the outside of the pipe into suitable flexible forms and at the same time pointing and smoothing off on the inside with a i to i mixture of mortar. The concrete used for joints shall be equal to or better in quality than that used for the pipe. Each joint shall be reinforced with steel rods, or the equivalent in area of some other form of reinforcement satisfactory to the engineer. As soon as the joint has been made it shall be covered with wet cloths and kept so covered for ten days thereafter. If desired, after the concrete has attained its final set, damp earth may be substituted for the wet cloths. 184. Tests of Pipe. On completion of the work, or as soon as possible there- after, the contractor shall make a full pressure test of the pipe, water being furnished therefore by All leaks found at the time of the test shall be made tight by the contractor. The cost of making the test, except furnishing water, shall be borne by the contractor. 185. Measurement. The price bid per linear foot shall be for pipe complete in place, ready for service, and shall include all material, except cement, entering into or used on the work, manufacture, hauling, laying, jointing, testing, repairing leaks, etc., until final inspection and acceptance by the engineer. The number of linear feet of pipe in place will be measured along the axis of the pipe after completion. 1 86. Payments. At the end of each calendar month 60 per cent of the contract price for pipe in place shall be paid to the contractor for all pipe manufactured during that month; 30 per cent additional shall be paid for pipe laid and jointed; and the remainder shall be paid after final test and acceptance of the pipe by the engineer, and when the terms of the contract shall have been fully complied with to the satisfaction of the engineer, and a release of all claims against , under, or by virtue of the contract, shall have been executed by the con- tractor. METAL FLUMES 187. Type of Flume. All flumes furnished under these specifications shall be made of metal and shall be of the semicircular, smooth-interior type. Bidders SPECIAL REQUIREMENTS 577 shall submit with their proposals a drawing or catalogue cut showing clearly the type of construction and detailed dimensions of the flume that they propose to furnish. Smoothness of interior surface and ease of erection will be important factors in the consideration of proposals. 1 88. Dimensions and Weight of Flume. The assembled flume shall have an interior diameter of feet inches and the depth shall be that of the full semicircle. The bidder shall state the weight of the completed flume per linear foot. A complete flume shall consist of sheets carrier rods, compression bars, shoes, nuts and washers. 189. Thickness of Metal Sheets. The thickness of the metal sheets shall be sufficient to provide necessary rigidity and stiffness. The following minimum thicknesses shall be used: No. of Flume. U. S. Standard Gage. 24 to 108 20 120 to 156 18 168 to 204 16 216 and larger 14 For the larger sizes of flumes intermediate carrier rods or reinforcing ribs shall be furnished, if necessary, to maintain the true semicircular shape of the sheets when subjected to the full weight of water. 190. Size of Carrier Rods and Compression Bars. Carrier rods shall be designed for a working stress of 8000 pounds per square inch when subjected to the full weight of the water; provided that the smallest allowable carrier rod shall be |-inch in diameter or its equivalent. Carrier rods shall be threaded at both ends and provided with nuts and washers. They shall be stronger in thread than in body. Compression bars shall be equivalent to or larger in cross-section than the corresponding carrier rods. Compression bars shall be provided with shoes for distributing the pressures on supporting timbers. The size and shape of shoes and washers shall be such as to properly distribute the pressures on the wooden timbers supporting the flume, and the average pressure on the timbers due to the full weight of the water in the flume shall not exceed 400 pounds per square inch. All carrier rods, compression bars, shoes, nuts and washers shall be coated before shipment by being dipped when hot in a mixture of pure California asphalt, or its equivalent; not less than 7 per cent nor more than 10 per cent of pure linseed oil shall be mixed with the asphalt. Materials for coating shall be subject to the approval of the engineer. 191. Joints. The joints between successive sheets comprising the flume lining shall be designed to be rigid and water tight and shall offer the -least possible obstruction to the flow of water through the flume. All necessary crimping of sheets to form the joints shall be done by the contractor. 192. Curves. The metal sheets for curved flumes shall be fabricated so as to conform exactly to the degree of curvature required. The engineer will furnish the contractor a list of lengths of flumes required of each degree of curvature and the degree of curvature shall be plainly stamped on each sheet. 193. Materials for Sheets. The metal sheets shall be manufactured from steel and shall be galvanized. The chemical and physical properties shall be as follows: 578 SPECIFICATIONS Elements Considered. Open-hearth Steel. Bessemer Steel. Carbon max. per cent 0.07-0.14 0.07-0.14 Manganese, per cent o . 34-0 .46 i . oo Phosphorus, per cent .03 .10 Sulphur, per cent .05 .07 Silicon, per cent .02 .02 Copper, per cent Recorded Recorded Ultimate strength 50,000-60,000 50,000-60,000 Elastic limit 25,000-35,000 25,000-35,000 Minimum elongation in 8 inches. 25 per cent 25 per cent The material shall show homogeneity of structure as exhibited by the ends of the broken test specimens. 194. Material for Compression Bands and Carrier Rods. These shall be made of medium steel and shall have an ultimate tensile strength of 55,000 to 65,000 pounds per square inch; an elastic limit of not less than one-half the ultimate tensile strength; a minimum per cent of elongation in 8 inches of 1,400,000 divided by the ultimate tensile strength; a silky fracture; and capability of being bent cold, without fracture, 180 degrees around a pin having a diameter equal to the thickness of the test piece. 195. Material for Shoes and Washers. The bearing shoes and washers for com- pression bands and carrier rods may be made of either gray or malleable cast iron. Gray iron castings shall conform in all respects to the standard specifications for such castings adopted September i, 1905, by the American Society for Testing Materials, except that no tensile test will be required. Malleable iron castings shall conform to the standard specifications for such castings adopted November 15, 1904, by the American Society for Testing Materials. 196. Test Pieces. All test pieces shall be furnished by the contractor at his expense. The number and shape of test specimens for gray and malleable castings shall be as prescribed in the specifications of the American Society for Testing Materials specified in paragraph hereof. For all other materials at least one test specimen shall be taken from each melt and where possible shall be cut from the finished material. Specimens not cut from finished material shall, in so far as possible, receive the same treatment before testing as the finished product. Tensile test pieces shall be f inch in diameter and shall have 8 inches of gage length. 197. Inspection and Tests. All necessary facilities and assistance for making inspection and tests shall be furnished to the engineer by the contractor at the ex- pense of the contractor. Physical tests and chemical analysis will be made by at his own expense; or they may be made at the factory by the con- tractor or his employees, acting under the direction of the engineer or his represen- tative; or certified tests may, at the option of the engineer, be accepted in lieu of the above-mentioned tests. No material shall be shipped until all tests and final inspection have been made, or certified tests shall have been accepted. 198. Galvanizing. The metal sheets shall have a coating of tight galvanizing. The grooving for joints and bending of sheets shall be done in such a manner as to avoid any injury to galvanizing. All sheets on \vhich the galvanizing is cracked or otherwise injured will be rejected. The galvanizing shall consist of a coating of pure zinc evenly^and uniformly applied in such a manner that it will adhere SPECIAL REQUIREMENTS 579 firmly to the surface of the metal. Each square foot of metal sheets shall hold not less than 2 ounces of /.inc. The galvanizing shall be of such quality that clean, dry samples of the galvanized metal shall appear black and show no copper-colored spots when they are four times alternately immersed for one minute in the standard copper sulphate solution and then immediately washed in water and thoroughly dried. The coating shall fully and completely cover all surfaces of the material, and shall appear smooth and polished and be free from lumps of zinc. 199. Measurement and Payment. Payment will be made on the basis of the actual assembled length of flume measured along the center line and at the prices bid in the schedule per cent of the contract price of each shipment will be paid on the acceptance of the material by the inspector and receipt by the engineer at of the bill of lading, properly receipted; and the remainder shall be paid when all the material covered by the contract shall have been received at its destination and finally inspected, checked and accepted by the engineer, and the terms of the contract shall have been fully complied with to the satisfaction of the engineer. STEEL HIGHWAY BRIDGES ( riveted 1 f deck 1 200. Description.-^^ bridge shall be of the ( pin _ connected j \ through } truss type, having a span, center to center of end bearings, of feet inches, and a clear width between trusses of feet. The bridge shall consist of spans. 201. Stress Sheets and Loading. The bidder shall furnish with his bid a stress sheet showing the maximum stress to which members are to be subjected, based on the following loading: / = span in feet; w = weight of steel per square foot of floor; ^ = live load per square foot of floor. Dead load: u>= not less than the actual weight of steel. Wooden floor = 15 pounds per square foot. Live load: pioo -^j or a concentrated load of 30,000 pounds on two axles'8 feet center to center with wheels spaced 6 feet center to center, and two-thirds of the load on one axle, assumed to occupy a space 16 feet in the direction of traffic by 12 feet at right angles thereto. Impact: for chords 25 per cent of uniform live load. for web and floor, 40 per cent of either uniform or concentrated live load. Wind load: unloaded chord, 100 pounds per linear foot of bridge, loaded chord, 200 pounds per linear foot of bridge. NOTE. Neither wind nor concentrated loads are assumed to act simultaneously with uniform live load. 202. Detail Drawings. The contractor shall prepare all detail and shop draw- ings. Each proposal shall be accompanied, in addition to the stress sheets, by such general drawings of members and details as will clearly show the type of construc- tion proposed at all points, and all items that are necessary to enable the engineer 580 SPECIFICATIONS to determine the strength of all parts of the structure and whether, as a whole and in all its parts, it complies with these specifications. As soon as practicable after the award of the contract complete detail and shop drawings shall be fur- nished to the engineer by the contractor and these shall receive the approval of the engineer before work is commenced. Working drawings shall be furnished in triplicate. The approval of general and working drawings shall not relieve the contractor from the responsibility for any errors therein. In case the engineer requires additional copies of drawings for use during construction or for record these shall be furnished by the contractor without charge. 203. Unit Stresses. The following limiting working stresses in pounds per square inch of net cross-section shall be used : Tension on rolled sections 16,000 Shear on rolled sections 9,000 Bearing on pins 20,000 Shear on pins . . . 10,000 Bearing on shop rivets 20,000 Shear on shop rivets 10,000 Bearing on field rivets 15,000 Shear on field rivets 7, 500 Bearing on columns 16,000 70 R Bearing on expansion rollers per linear inch $ood d = diameter of roller in inches; L = unsupported length of column in inches; R = least radius of gyration in inches. No compression member shall have an unsupported length exceeding 1 20 times its least radius of gyration for main members, or 140 times its least radius of gyra- tion for laterals. 204. Reversed Stresses. Members subject to reversion of stresses shall be de- singed to resist both tension and compression and each stress shall be increased by eight-tenths of the smaller stress for determining the sectional area. The con- nections shall be designed for the arithmetical sum of the stresses. 205. Combined Stresses. Members subject to both direct and bending stresses shall be designed so that the greatest unit fibre stress shall not exceed the allowable unit stress for the member. 206. Net Sections. The net section of any tension flange or member shall be determined by a plane cutting the member square across at any point. The greatest number of rivet holes that can be cut by any such plane, or whose centers come nearer than 2^ inches to said plane, are to be deducted from the cross-section when computing the net area. 207. Minimum Sizes. No metal less than ^ inch in thickness shall be used except for filling plates. The smallest angles used shall not be less than 2\ X 2\ X TS inches. A single angle shall never be used for a compression member. 208. Connections. All connections shall be designed to develop the full strength of the members. Connecting plates shall be used for connecting all members and in no case shall any two members be connected directly by their flanges. Angles SPECIAL REQUIREMENTS 581 subject to tensile stress shall be connected by both legs, otherwise only the section of the leg actually connected will be considered effective. 209. Portal Bracing. Portal bracing shall consist of straight members and shall be designed to transmit the full wind reaction from the upper lateral system into the end posts and abutments. The clear head room below portal and sway bracing for a width of 6 feet on either side of center line shall be not less than 15 feet. 210. Sway Bracing, Sway bracing of an approved type shall be provided at each panel point. 211. Lateral Systems. Upper and lower lateral systems shall be designed to resist the maximum wind pressures from either direction. The members shall be nearly as practicable in the plane of the axes of the chords. 212. Floor System. All floor beams and stringers shall be rolled or riveted steel girders. Floor beams shall be rigidly connected to the trusses, and stringers shall be rigidly connected to the floor beams and their tops shall be flush with the tops of floor beams. 213. Intersection of Axes of Members. The axes of all members of trusses, and those of lateral systems coming together at any apex of a truss or girder must intersect at a point whenever such an arrangement is practicable, otherwise all induced stresses and bend of members caused by the eccentricity must be provided for. 214. Batten Plates and Lattice Bars. The open sides of compression members shall be stayed by batten plates at the ends and by diagonal lattice bars at inter- mediate points. Batten plates shall be used at intermediate points when, for any reason, the latticing is interrupted. Lattice bars shall be inclined to the member not less than 60 degrees for single latticing not less than 45 degrees for double latticing. 215. Eyebars. The thickness of eyebars shall be not less than f inch nor less than one-seventh the width of the bar. Heads of eyebars shall be formed by upsetting and forging and shall be so proportioned as to develop the full strength of the bar. Eyebars shall be prefectly straight at the time they are bored, and all bars composing one member shall be piled, clamped together, and bored in one operation. The eyebars composing a member shall be so arranged that their surfaces are not in contact. 216. Rods. No rod shall be used which has a cross-sectional area less than f square inch. Screw-ends shall be stronger in thread than in body. 217. Riveting. The rivets used shall in general be f inch in diameter; smaller ones being allowable where made necessary by the size of the member, but no rivets smaller than f inch in diameter shall be used in legs of an angle iron equal to or greater than 3! inches wide. Not less than three rivets shall be used in any main truss, portal or lower lateral connection or in any compression' strut or sway bracing, portal bracing or upper lateral system connection. The pitch of rivets in all classes of work in the direction of the stress shall never exceed 6 inches nor be less than three diameters of the rivet. At the ends of compression members it shall not exceed four times the diameter of the rivets for a length equal to twice the width of the member. No rivet hole center shall be less than one and one-half diameters from the edge of the plate, and whenever practicable this distance is to be increased to two diameters. The rivets when driven must completely fill the holes. The rivet heads must be round, and they must be of uniform size 582 SPECIFICATIONS for 'the same size rivets throughout the work; they must be neatly made and con- centric with the rivets and must thoroughly pinch the connected pieces together. Whenever possible all rivets shall be machine driven. No rivet excepting those in shoe plates and roller and bed plates is to have a less diameter than the thick- ness of the thickest plate through which it passes. The effective diameter of any rivet shall be assumed the same as its diameter before driving, but in making deductions for rivet holes in tension members the diameter of the hole shall be assumed f irich larger than that of the rivet. The amount of field riveting shall be reduced to a minimum, and all details are to be made so that the field rivets can be driven readily. Rivets shall not be used in direct tension. The contractor will be held responsible for the correct fitting of all parts upon assembly in the field, and, if necessary, to insure this, all members shall be assembled in the shop, and fitted before shipment. 218. Pins. All pins shall be turned smoothly to a gage and shall be finished perfectly round, smooth and straight. All pins up to and including 3! inches in diameter shall fit the pin-holes within -^- - inch, all pins over 3^ inches in diameter shall fit their holes within -^ inch. The contractor must provide steel-pilot nuts for all pins to preserve the threads while the pins are being driven. 219. Camber. All trusses shall be cambered by making the top chord sec- tion longer than the corresponding bottom chord section by -^ inch for each 10 feet of length. 220. Expansion and Contraction. Provision shall be made for changes in length due to temperature variations of at least f inch for each 10 feet of span. 221. Roller Ends. Each truss of more than 60 feet span shall be provided with one roller end. For spans 60 feet and less a sliding end may be used. Rollers shall be turned accurately to gage and must be finished perfectly round and to the cor- rect diameter or diameters from end to end. The tongues and grooves in plates and rollers must fit snugly so as to prevent lateral motion. Roller beds must be planed. The smallest allowable diameter of expansion rollers is 3! inches. 222. Anchorages. Every span must be anchored at each end to the pier or abutment in such a manner as to prevent lateral motion, but so as not to interfere with the longitudinal motion of the truss due to changes of temperature. The shoes or bolsters shall be so located that the anchor bolts will occupy a central position in the slotted holes at a temperature of 40 F. Bedplates shall be de- signed to distribute the load over a sufficient area to keep the pressure on the masonry below 400 pounds per square inch. 223. Hand Railing. A suitable latticed hand railing shall be provided for each truss. 224. Shop Painting. Before leaving the shop all structural steel, except as below specified, shall be thoroughly cleaned of all loose scales and rust and given one coat of good iron ore paint mixed with pure linseed oil, which shall be well worked into all joints and open spaces. All surfaces of steel that will come in contact with each other shall be painted before being riveted or bolted together. Pins, pinholes, screw threads and all finished surfaces shall not be painted but shall be coated with white lead and tallow as soon as they are finished. SPECIAL REQUIREMENTS 583 MATERIAL 225. Manufacture. Structural steel shall be made by the open-hearth process and shall conform in all respects, not specifically mentioned herein, to the Standard Specifications for Structural Steel for Bridges of the American Society for Testing Materials adopted August 25, 1913. 226. Physical and Chemical Properties of Structural Steel. Steel shall contain not more than 0.05 per cent sulphur, and not more than 0.04 per cent phosphorus for basic open-hearth nor more than 0.06 per cent phosphorus for acid open-hearth. It shall have an ultimate tensile strength of 55,000 to 65,000 pounds per square inch; an elastic limit, as indicated by the drop of beam of not less than one-half the ultimate tensile strength; a minimum per cent of elongation in 8 inches of 1,500,000 divided by the ultimate tensile strength; a silky fracture and capability of being bent cold without fracture 180 degrees flat on itself for material f inch thick and under; for material over f inch to and including if inches around a pin having a diameter equal to the thickness of the test piece; and for material over ij inches thick, around a pin having a diameter equal to twice the thickness of the test piece. A deduction of 2.5 will be allowed in the specified percentage of elonga- tion for each ^ inch in thickness below ^ inch and a deduction of i will be allowed for each inch in thickness above f inch. 227. Physical and Chemical Properties of Rivet Steel. Rivet steel shall contain not more than 0.04 per cent, each of sulphur and phosphorus. It shall have an ultimate tensile strength of 45,000 to 55,000 pounds per square inch; an elastic limit as determined by the drop of beam of not less than one-half the ultimate tensile strength; a minimum per cent of elongation in 8 inches of 1,500,000 divided by the ultimate tensile strength; a silky fracture; and capability of being bent cold without fracture 180 degrees flat on itself. 228. Finish. Finished material must be free from injurious seams, flaws, or cracks, and have a workmanlike finish. 229. Marking. Every finished piece of steel shall have the melt number stamped or rolled upon it. Steel for pins and rollers shall be stamped on the end. Rivet steel and other small parts may be bundled, with the above marks on an attached metal tag. 230. Test Pieces. (See paragraph 40.) 231. Tests. (See paragraph 41.) 232. Payment for Fabricated Material. per cent of the contract price of each shipment will be paid on the acceptance of the material by the inspector and receipt by the engineer of the bill of lading, properly receipted (and the re- mainder will be paid when all of the material covered by the contract shall have been received at its destination and finally inspected, checked and accepted by the engineer, and the terms of the contract shall have been fully complied with to the satisfaction of the engineer). (NOTE. Portion in parentheses is to be omitted here when erection is included in the contract.) ERECTION 233. Material and Labor. The contractor shall furnish all labor, tools, machin- ery and materials, except wood flooring, for erecting the bridge complete in place, 584 SPECIFICATIONS including all hauling, erection and dismantling of all falsework and staging, setting of anchor bolts, and all other work necessary for the completion of the structure ready for traffic . 234. Wood Floor. Lumber for flooring will be furnished by , but shall be put in place by the contractor and he shall furnish all necessary fas- tenings. The lumber will be delivered to the contractor at the railroad station most convenient to the work and the contractor shall haul same to the bridge site. 235. Painting after Erection. After erection all metal work shall be thoroughly cleaned of mud, grease and other objectionable matter and evenly painted with two coats of paint of the kind and colors specified by the engineer. Linseed oil shall be used as the vehicle in mixing the paint for each of these coats and the separate coats shall have distinctively different shades of color. All recesses which might retain water shall be filled with thick paint or some waterproof material before final painting. The first coat shall be allowed to become thoroughly dry before the second coat is applied. No painting shall be done in wet or freezing weather. 236. Final Payment. Final payment will be made upon completion of the erec- tion and acceptance of the finished structure by the engineer, and when the terms of the contract shall have been fully complied with to the satisfaction of the engi- neer. TUNNELS 237. Excavation. The tunnel, shafts and adits shall in all cases be excavated in such manner and to such dimensions as will give suitable room for the necessary timbering, lining, ventilating, pumping and draining. The contractor shall use every reasonable precaution to avoid excavating beyond the outside lines of permanent timbering and beyond the outside neat concrete lines where no per- manent timbering is required. All drilling and blasting shall be carefully and skill- fully done so as not to shatter the material outside of the required lines. Any blasting that would probably injure the work will not be permitted and any damage done to the work by blasting shall be repaired by the contractor at his expense, and in a manner satisfactory to the engineer. Tunnel excavation will be paid for at the price bid per linear foot. Partial excavation, as in the case of a heading, amounting to not less than one-half the full section will be allowed for in the monthly progress estimates at one-fourth of the price named in the contract for full excavation. 238. Timbering. Suitable timbering and lagging shall be used to support the tunnel, sides and roof wherever necessary. If practicable, this timbering may be removed before the construction of the concrete lining. Timbering may be left in place, provided it is constructed in such a manner as not to weaken the concrete lining and is in accordance with designs approved by the engineer. An approved design for such permanent timbering is shown in the drawings but, in case this design is found to be inadequate it may be modified from time to time, subject to the approval of the engineer. Lumber for timbering shall be furnished by the con- tractor. The cost of furnishing and placing permanent and temporary timbering shall be included in the price per linear foot bid in the schedule for excavating the tunnel, except that in addition thereto the contractor will be paid the sum of dollars per M feet B. M. for permanent timbering in place. No payment will SPECIAL REQUIREMENTS 585 be made for temporary timbering nor for timber used in filling cavities. In meas- uring permanent timbering for payment, the net length of pieces and the commer- cial cross-sectional dimensions will be taken. Nothing herein contained shall prevent the contractor from placing such temporary timbering as he may deem necessary nor from using heavier permanent timbering than that shown in the draw- ings, nor shall be construed to relieve the contractor from sole and full responsi- bility for the safety of the tunnel and for damage to person and property. 239. Concrete Lining. The tunnel shall be lined throughout with concrete. The tunnel lining side walls and arch, where permanent timbering is not required, shall have an average thickness of inches, with a minimum thickness of inches over projecting points of rock. The average thickness of the con- crete tunnel invert shall be inches. Where permanent timber is required it shall be set back so far that the concrete lining will cover the timber at least inches. The concrete for such timber portions of the tunnel will be esti- mated as having an average thickness of inches. If the tunnel is excavated to greater dimensions than necessary for placing the prescribed average thickness of the concrete lining, the excess space shall be solidly rilled with concrete, or the lining shall be confined with forms to the prescribed thickness and properly back- filled. Concrete tunnel lining will be paid for by the cubic yard at the unit price named in the contract, measured to the neat lines shown in the drawings, based on the average thickness herein specified. 240. Lines and Grades. The contractor shall provide such forms, spikes, nails, troughs for plumb-bob lines, light, etc., and such assistance as may be required by the engineer in giving lines and grades, and the engineer's marks shall be care- fully preserved. Work in the shafts, adits and tunnel shall be suspended for such reasonable time as the engineer may require to transfer lines and to mark points for line and grade. No allowance will be made to the contractor for loss of time on account of such suspension. 241. Draining. The contractor shall drain the tunnels and adits where neces- sary to rid the same of standing water. Pumping shall be done where gravity flow to an outlet can not be secured. i 242. Lighting and Ventilating. The contractor shall properly light and venti- late the tunnel during construction. 243. Storage and Care of Explosives. Caps or other exploders or fuses shall in no case be stored or kept in the same place in which dynamite or other explosives are stored. The location and design of powder magazines, methods of transport- ing explosives and in general the precautions taken to prevent accidents must be satisfactory to the engineer; but the contractor shall be liable for all damages to person or property caused by blasts or explosions. 244. Backfilling. Any space outside of the concrete tunnel lining shall be com- pactly refilled at the expense of the contractor with such of the excavated material from the tunnel as may be approved by the engineer. Large cavities in the tunnel roof may be filled with waste timber. The backfilling to the springing lines of the arch shall be placed before the arch is constructed, and shall be brought up evenly on both sides of the tunnel; it shall be spread in layers not exceeding 6 inches in thickness and well rammed. The invert and side walls shall be braced, if required, during the placing of the back-filling. 245. Adits and Shafts. The contractor shall construct at his own expense such 586 SPECIFICATIONS adits and shafts as he may desire to use to expedite the tunnel work. The sides and the arch of the tunnel lining situated immediately beneath the opening of each shaft shall be increased to such suitable thicknesses as the engineer may prescribe; and each adit shall be closed at the point where it meets the tunnel with a block of concrete averaging at least 4 feet in thickness, extending into the sides of the adit 2 feet and having a foundation 2 feet below the bottom of the tunnel. All concrete required for this purpose shall be furnished by the contractor at his own expense, the cement for which will be furnished to the contractor at its cost on the work. All shafts must be compactly refilled. Dumping from the top will not be allowed until the tunnel arch has been covered to a depth of at least 10 feet. After the completion of the block of concrete required for closing an adit the adit shall be refilled and the filling tamped into place for a distance of 20 feet from the tunnel. TELEPHONE SYSTEM NOTE. For short telephone lines serving a small number of stations a ground return circuit will in general give satisfactory service. For long lines or those having many sta- tions a metallic circuit will be preferable. In determining whether to use the ground circuit or metallic circuit the engineer should carefully study the importance of continuity of ser- vice, the length of line and number of stations, the liability of disturbance by existing or contemplated electrical systems and other local conditions. For the usual telephone systems No. 12 wire will be amply large, but for lines subjected to exceptionally heavy loads of sleet and snow the use of No. 10 wire may be necessary. 246. Pole Line. The pole line will follow tangents and curves as shown in the drawings and will have the number of corners therein shown. An average of thirty poles per mile shall be used on tangents. The spans adjoining a pole on a curve at a corner shall not exceed 150 feet each for a pull of 5 feet, and the allow- able length span shall decrease 10 feet for each increase of 5 feet in the pull up to and including a pull of 30 feet. When a bend made on a single pole produces a pull of more than 30 feet the pole shall be thoroughly braced or guyed and the adjoining spans shall not exceed 100 feet each, or such a bend shall be made on two poles and the lengths of the adjoining spans adjusted with the foregoing pro- visions relating to span and pull. The term " pull " as herein used means the per- pendicular distance from the pole under consideration to a straight line joining the two adjacent poles. When a span of from 200 to 250 feet is necessary, the adjoin- ing spans shall not exceed 100 feet each, and where a span of from 250 to 500 feet is necessary, the adjoining two spans at each end shall not exceed 100 feet each. On uneven ground the spans shall be so chosen and the poles so set as to avoid abrupt changes in the direction of the wire line vertically. In distributing poles, the heaviest shall be placed so far as practicable on corners and at the ends of long spans. 247. Poles. Telephone poles shall be in general 5-inch poles 25 feet in length. At crossings of highways, railroads and gullies 6-inch poles of requisite length shall be used, and for this purpose poles 30 feet in length and poles 35 feet in length will be required. The poles shall be cut from growing trees, shall be reasonably well proportioned for their length and shall be peeled, neatly trimmed, well seasoned, reasonably sound and free from unsightly wind twists, injurious butt rot and other defects that materially impair them for the use intended. Butt rot in the center, including small ring rot outside of the center, the total of SPECIAL REQUIREMENTS 587 which does not exceed 10 per cent of the area of the butt, will be permitted. Sweeps not exceeding i inch for every 5 feet in length of pole will be permitted. The tops of seasoned 5 -inch poles shall measure not less than 15 inches in circumfer- ence and those of 6-inch poles not less than 18 inches. If the poles are measured when green 5 -inch poles shall be not less than 16 inches in circumference at the tops and 6-inch poles not less than 19^ inches. The top of each pole shall be trimmed so as to form a right-angled roof. The roofs of poles shall be painted with two coats of good quality of iron oxid paint. 248. Setting Poles. On tangents the poles shall be set in a vertical position, and on curves and at corners they shall be raked 10 inches for a pull less than 5 feet, 15 inches for a pull of from 5 to 10 feet and 25 inches for a pull of more than 10 feet. Each pole hole in earth shall be 5 feet in depth and shall be dug of suf- ficient size throughout to admit of tamping around the entire perimeter of the pole. On hillsides the depth of the holes shall be measured from the lowest side of the opening. Where the line crosses solid rock, pole holes shall be blasted to a depth of 3 feet, unless such solid rock can be covered by a single span not exceeding 250 feet. Each pole shall be carefully held in proper position while the hole is being filled. Filling holes with earth shall be done by one man and the earth firmly tamped simultaneously by three men. Rock debris when used for filling holes shall contain sufficient earth to fill all cavities therein and shall be homogeoneously placed and thoroughly compacted. When the hole is filled, earth or rock shall be piled and firmly packed about the hole to a height of i foot above the original ground surface. The filling for holes and the general manner of setting poles shall be such as will enable each pole to withstand the strains to which it will be sub- jected. 249. Braces. Braces shall be 5 inches in diameter at the top, shall be long enough to attach to the pole at two-thirds the height thereof above the ground, to make an angle of 30 degrees therewith and to extend into the ground at least 4 feet measured along the brace and shall conform in all other respects to the specifications for poles braces feet in length, braces feet in length and braces feet in length will be required. 250. Setting Braces. Each brace shall be set in the ground at least 3! feet in vertical depth. The brace shall be cut slanting at the top to fit close to the pole and shall be attached to the pole with a f-inch bolt supplied with a washer at each end. This bolt shall be placed at the lowest point of the joint. In fitting the brace to the pole all trimming shall be done on the brace. 251. Guys and Anchors. Guys shall consist of No. 6, B.W.G., galvanized steel wire. Guy anchors in earth shall consist of and galvanized iron rods. (If cast-iron anchor plates are used they shall be 8 inches square and \ inch thick and shall be provided on the lower face with a cylindrical lug at the center having a diameter of 2 inches, and a height of i^ inches and with diagonal ribs \ inch thick rising from zero elevation at the corners and terminating in the cylindrical lug with elevation equal thereto. Each cast-iron plate shall have a f-inch cored hole through its center for the reception of the anchor rod.) Each galvanized iron rod shall be f inch in diameter and 6 feet in length and shall be provided at the upper end with a suitable eye and a wire rope thimble for a J-inch rope and at the lower end with U. S. standard threads and a galvanized iron nut. Guy anchors in rock shall consist of galvanized iron rods of the combination eye and wedge-bolt 588 SPECIFICATIONS type i inch in diameter and 18 inches in length, each provided with a suitable wedge and a wire rope thimble for a j-inch rope. 252. Placing Gtiys and Anchors. Each guy shall be attached to tb~ pole imme- diately below the bracket by making two turns around the pole and wrapping the end eight times around the guy and shall be secured to its rod by passing around the thimble and terminating on itself in eight turns. The turns about the pole shall be secured by at least three 2-inch galvanized iron staples. The angle between the guy and its pole shall be as nearly 45 degrees as is practicable. 253. Guying and Bracing. Guys and braces shall be placed wherever considered essential by the engineer. On tangents and on curves having pulls less than 10 feet double side guys will be required about every 1000 feet of line; and on curves or at corners where the pull is from 10 to 30 feet each pole shall be provided with a guy or brace. On curves and at corners each pole at which the pull exceeds 30 feet shall be provided with either a guy or a brace placed in the plane of each of the adjoining spans and the adjacent poles shall be provided with appropriate supplemental bracing or guying. At least one head and one back guy shall be installed on every mile of line. Additional head and back guys or braces shall be used wherever the slope of the ground, length of span, change in direction or extra pole height at road crossings requires them for stability. 254. Brackets (Ground Circuit). Pony telephone side brackets 15X2X10 inches shall be used. They shall be made of the best quality of well-seasoned, sound, straight-grained oak, free from knots and sapwood, shall have the insulator threads truly cut and complete and shall be painted with two coats of the best quality of iron oxid paint. Each bracket shall be securely fastened to the pole with one 4od and one 6od galvanized wire nail in such a position that the base of the bracket will be about 14 inches below the top of the pole. Where the change in direction of the wire at any pole is more than 60 degrees an extra bracket shall be used. Brackets shall be placed on the same side of all poles except on curves or at corners, where they shall be so placed that the strains produced by the wires will tend to press the insulators toward the poles. 255. Brackets (Metallic Circuit). Pony telephone side brackets 1^X2X10 inches shall be used. They shall be made of the best quality of well-seasoned, sound, straight-grained oak, free from knots and sapwood, shall have the insulator threads truly cut and complete and shall be painted with two coats of the best quality of iron oxid paint. Each bracket shall be securely fastened to the pole with one 40^ and one 6od galvanized wire nail. Where the change in direction of the wire at any pole is more than 60 degrees an extra bracket shall be used for each wire. On tangents the brackets shall be placed one on each side of the pole and on curves and corners they shall be so placed that the strains produced by the wires will tend to press the insulators toward the poles. The top bracket shall be so placed that its base will be about 14 inches below the top of the pole, and the bottom bracket so that its base will be 12 inches below that of the top bracket, except on transposition poles on tangents. On transposition poles the brackets shall be at the same elevation so placed that the insulator for each wire will be as nearly as practicable on a straight line between those for the same wire on the adjacent poles. 256. Insulators (Ground Circuit). Standard pony, glass, lo-ounce insulators shall be used. They shall be made of common glass, shall be free from cracks. SPECIAL REQUIREMENTS 589 blow-holes, flaws and sharp edges and shall have smooth threads of uniform pitch accurately fitting the threads on the brackets. 257. Insulators (Metallic Circuit}. Standard pony, glass, lo-ounce insulators and two-piece transposition insulators of equivalent strength shall be used. They shall be made of common glass, shall be free from cracks, blow-holes, flaws and sharp edges and shall have smooth threads of uniform pitch accurately fitting the threads on the brackets. 258. Line Wire. The line wire shall consist of No. 12, B.W.G., galvanized iron wire of the quality known as " Best Best," having an average resistance at 68 F. not to exceed 34-4- ohms per mile. The wire shall be of uniform cross-section, shall weigh approximately 170 pounds per mile, shall have an ultimate tensile strength of not less than 560 pounds and shall be capable of withstanding at least fifteen twists about its axis in a length of 6 inches. It shall be soft and pliable and capable of elongating 15 per cent without breaking, after being galvanized. The diameter of the line wire in inches shall be not more than 0.113 nor less than o.i 06. The wire shall be furnished in coils of \ mile or i mile continuous lengths, without welds, joints or splices, and each coil shall be drawn from a rod without welds, joints or splices of any kind. The galvanizing shall consist of a coating of pure zinc evenly and uniformly applied in such a manner that it will adhere firmly to the surface of the metal. The galvanizing shall be of such quality that clean dry samples of the galvanized wire shall appear black and show no copper- colored spots after they have been four times alternately immersed for one minute in the standard copper sulphate solution and then immediately washed in water and thoroughly dried. 259. Stringing Wire. The wire shall be strung with as few joints as possible and shall be joined by twisting the wires for a distance of about 3 inches around each other two complete turns and soldering, the end of each wire terminating in five tightly fitting contiguous turns around the other wire. The line wire shall be tied to the insulators with tie wires of No. 12, B.W.G., galvanized iron wire cut in suitable lengths. The line wire shall first be laid in the groove of the insulator on the side away from the pole, after which the tie wire shall be passed entirely around the insulator and line wire and terminate at each end in five tightly fitting turns around the line wire. The tension on the line wire for each span shall be, in the judgment of the engineer, as high as will be safe for the minimum tempera- ture for the locality. 260. Transposition (Metallic Circuit}. In general a transposition of the line wires shall be made once in each mile, but the exact number and location of trans- positions shall conform to the local requirements therefor. Each transposition shall be made without the use of transposition insulators by interchanging the wires laterally in one span and vertically in the two succeeding spans. 261. Trimming Trees. All trees along the line of such character and location as to render them liable to being blown over so as to interfere with the telephone wires shall be cut down and removed or burned, and all trees close to the line that in the judgment of the engineer will not endanger the telephone wires shall be so trimmed as to leave a clear space of 10 feet about the telephone wires in all directions under stress of the heaviest probable wind storms. 262. Lightning Rods. Lightning rods consisting of No. 12, B.W.G., galvanized iron wire shall be installed throughout the line at intervals of about \ mile. Each 590 SPECIFICATIONS rod shall be located about one-fourth the distance around the pole from the bracket and shall be attached to the pole with 2-inch galvanized iron staples. The upper end of each rod shall project about 3 inches above the top of the pole and the lower end shall terminate beneath the butt of the pole in a flat coil containing about 6 feet of wire. 263. Lightning Arresters. A lightning arrester shall be installed on each line pole at which the current is transferred from the line wire to a station wire. The arrester shall be of the double-pole, lightning and sneak-current type, shall have adjustable and removable carbon blocks mounted upon porcelain bases and shall have fuses that will adequately protect it from lightning and sneak currents. The arrester shall be connected with No. 12, B.W.G., galvanized iron wire to any exist- ing water pipe system nearby or to a galvanized iron ground rod \ inch in diameter and 6 feet in length driven into permanently moist earth. The connecting wire shall be carefully soldered to the water pipe or to the ground rod. Twenty-five extra sets of fuses shall be furnished with each arrester. 264. Station Wiring (Ground Circuit). The current shall be carried into build- ings on No. 1 8, B. & S. G., rubber-insulated copper wire covered with black braid saturated with waterproof compound and carried on porcelain knobs having a diameter of not less than i^ inches. The return pole of each instrument shall be connected by means of a similar wire to any existing water pipe system nearby or to a galvanized iron ground rod | inch in diameter and 6 feet in length driven into permanently moist earth. The connecting wire shall be carefully soldered to the water pipe or to the ground rod. Inside wiring shall consist of No. 18, B. & S. G., rubber-insulated copper wire covered with braid of a greenish color. All inside wiring shall conform to the best practice and shall be done only by expert electricians. Where wires pass through walls and partitions insulated bushing shall be provided. 265. Station Wiring (Metallic Circuit}. The current shall be carried into and out of buildings on No. 18, B. & S. G., rubber-insulated copper wire covered with black braid saturated with weatherproof compound and carried on porcelain knobs having a diameter of not less than i| inches. Inside wiring shall consist of No. 1 8, B. & S. G., rubber-insulated copper wire covered with braid of a greenish color. All inside wiring shall conform to the best practice and shall be done only by expert electricians. Where wires pass through walls and partitions insulated bushings shall be provided. 266. Instruments. Each proposal shall be accompanied by a complete descrip- tion of the various essential parts of the telephone that the bidder proposes to fur- nish, which shall be subject to the approval of the engineer. VITRIFIED PIPE, FOR CULVERTS 267. Quality. All vitrified pipe shall be of the best quality of smooth, well burned, salt-glazed, vitrified clay sewer pipe. It shall be of the hub-and-spigot pattern free from cracks due to rough handling, cooling, frost and other causes and free from chippings and clear fractures that will impair it for the purpose in- tended. All pipes that are designed to be straight shall not deviate materially from a straight line, and those designed to be curved shall substantially conform to the required radius of curvature and other general dimensions. SPECIAL REQUIREMENTS 591 268. Size. Both the bodies and bells of all pipes shall have a thickness not -less than one-twelfth the inside diameter of the pipe. Each hub shall freely receive to its full depth the spigot end of the succeeding pipe without any chipping of either and leave a space of not less than \ inch all around for the cement joint; it shall also have a depth from its face to the shoulder of the pipe on which it is moulded at least 2 inches greater than the thickness of said pipe. The length of pipe sections shall be between 2 and 3 feet exclusive of the socket. 269. Rejection. Any pipe that does not meet the above requirements will be rejected. CHAPTER XXIII TABLES TABLE XLIIL EXTREME FLOOD DISCHARGES , Maxi- Drain- mum Dis- Stream Locality age Area, charge in Cu.ft. Date of Flood in Sq. Miles per Sec. per Sq. Mile I. AMERICAN STREAMS: Columbia River Dalles, Ore 237.000 5-9 Ohio River Paducah, Ky 205,750 7 o Feb., 1884 Susquehanna Harrisburg, Pa 24,030 30.6 Mar., 1865 Susquehanna Harrisburg, Pa 24,030 30. June, 1889 Tennessee Chattanooga, Tenn 21,382 34 3 Mar, ii, 1867 Ohio River Pittsburg, Pa 19,100 22.9 Mar. 15, 1907 Sacramento Red Bluff, Cal 10,400 24.4 Feb., 1909 Potomac Point of Rocks, Md 9,654 48 . 9 June 2, 1889 Potomac Point of Rocks, Md 9,654 22.6 Mar., 1902 Allegheny Kittanning, Pa 9,010 26.6 Mar. 20, 1905 Savannah Augusta, Ga 7,500 40.0 Sept. ii, 1888 Delaware Lambertville, N. J 6,855 37- I Jan. 8, 1841 Salt McDowell, Ariz 6,255 26.1 Monongahela Lock No. 4, Pa 5,430 38.1 July n, 1888 Hudson Mechanicsville, N. Y 4.500 26.6 Mar. 28, 1913 Kennebec Waterville, Me 4,270 35-3 Dec. 16, 1901 Neosho lola, Kans 3,670 20.3 July 10, 1904 Feather Oroville, Cal 3,640 51-3 Mar., 1907 Mohawk Cohoes N Y 3,472 28.5 Mar. 27, 1913 Chattahoochee West Point, Ga 3,300 26.8 Dec. 30, 1901 Shenandoah Millville, W. Va 2,995 46.6 Oct., 1896 Catawba Rock Hil!, S. C 2,987 50.5 May 23, 1901 Hudson Glens Falls N. Y. 2,760 25 . 3 Mar. 28, 1913 New River Radford, Va 2,725 63-3 May, 1901 Savannah Near Calhoun Falls, S. C.. . 2,712 27-7 Feb. 14, 1900 Kennebec Bet. Forks and Waterville 2,700 48. 5 Dec. 16, 1901 Chemung Chemung, N. Y 2,440 21.5 Mar. 28, 1913 Ocmulgee. Macon Ga. 2,425 2O . Mar. i, 1902 Androscoggin Rumford Falls, Me 2,320 23-8 Apr. 22, 1895 592 EXTREME FLOOD DISCHARGES 593 TABLE XLIII. EXTREME FLOOD DISCHARGES Continued Stream Locality Drain- age Area, in Sq. Miles Maxi- mum Dis- charge in Cu.ft. per Sec. per Sq. Mile. Date of Flood N. Fork Feather Big Bend, Cal Fair Oaks Cal ,940 56.3 Mar. 19, 1907 Near Sanger Cal 74.0 Avonmore, Pa. 720 Allegheny San Joaquin S. Fork Shenandoah Chattahoochee Red House, N. Y Hamptonville, Cal Near Front Royal, Va. . . . Oakdale Ga ,640 ,637 ,570 560 25.0 36.5 48.9 Mar. 2, 1910 Jan., 1881 Mar., 1902 Dec 30 1901 Catawba Catawba N. C 535 61 8 May 23 1901 Tuolumne Lagrange Cal 500 Jan 1911 Cheat. Morgant&wn W. Va 380 30 3 Jan. 1911 Chagres Yuba Merced Scioto Flint Stanislaus Clarion Schoharie Creek Schoharie Creek Youghiogheny Passaic Gatun, Panama Near Smartsville, Cal .... Near Merced Falls, Cal.. . Columbus, Ohio Near Woodbury, Ga Knight's Ferry, Cal Clarion, Pa Fort Hunter, N. Y Fort Hunter, N. Y Below Confluence, Pa. ... Dundee N J ,320 ,220 ,OQO ,047 988 935 910 909 900 875 823 93-9 90.9 34-1 80.8 30.6 6i.l 43-2 44-5 55-1 52.6 38 I Dec. 28, 1909 Jan., 1909 Jan., 1911 Mar. 25, 1913 Feb. 28, 1902 Mar., 1907 Mar., 1905 Mar. 27, 1913 Mar. 2, 1901 Aug. 21, 1888 Raritan Bound Brook, N. J 806 64 5 Sept. 24, 1882 Putah Creek Hudson Chagres Broad Little Tennessee Monocacy McCloud Hoosic Winters, Cal North Creek, N. Y Bohio, Panama Near Carlton, Ga Judson, N. C Near Frederick, Md. ..... Near Gregory, Cal Johnsonville, N. Y. 805 804 779 762 675 660 608 605 37-2 35-0 II5-5 38.2 85.3 31-0 68.2 38 o Mar., 1907 Mar. 28, 1913 Dec. 27, 1909 Feb. 28, 1902 Dec., 1901 Mar., 1902 Mar., 1904 Mar. 28, 1913 Stony Creek Tugaloo Near Fruto, Cal Near Madison S C 60 1 48.7 36 8 Feb., 1909 July I 1905 Santa Catarina Aug 27 1909 Coosawattee Cosumnes Clentangy Carters, Ga Michigan Bar, Cal Columbus Ohio 531 524 514 31 -9 42.7 70.0 May 21, 1901 Jan., 1911 Mar. 25, 1913 Deerfield San Luis Rey Ausable River Cattaraugus Creek Casselman Shelburne Falls, Mass. . . . San Luis Rey, Cal Ausable Forks, N. Y Versailles, N. Y Confluence Pa 5oi 500 487 467 448 42.5 ' 200. o 45-2 53.5 Apr. 15, 1909 1916 Mar. 27, 1913 Mar. 25, 1913 Mar., 1907 Youghiogheny Chagres River Rio Mora Confluence, Pa Alhajuela, Panama Weber N. Mex 435 427 52.0 398 . 1 f.f 7 Mar., 1907 Dec. 26, 1909 Hiwassee Tygart River . Murphy, N. C Belington, W. Va 410 54-5 40 8 Mar. 19, i899 594 TABLES TABLE XLIII. EXTREME FLOOD DISCHARGES Continued Stream Locality Drain- age Area, in Sq. Miles Maxi- mum Dis- charge in Cu.ft. per Sec. per Sq. Mile Date of Flood Pocolet 400 88 9 Jennv Lind Cal 395 176 2 Middle Oconee Near Athens Ga 395 49 5 Feb 28 1902 Black Lick Pompton Rondout Creek Black Lick, Pa Two Bridges, N. Y Rosendale, N. Y 386 380 380 50.8 61.6 51 3 Mar., 1905 Oct. 10, 1903 Apr 26 1910 Esopus Creek Mt. Marion, N. Y 378 65 3 Apr 26 1910 W. Canada Creek Trenton Falls, N. Y 376 96 5 Dec 15 1901 W. Canada Creek W. Canada Creek Piscataquis Bear River East Canada Creek Trenton Falls, N. Y Hinckley, N. Y Foxcroft, Me Van Trent, Cal Dolgeville N Y 376 372 286 263 256 69. i 104.5 77-6 98.1 54 3 Mar. 28, 1913 Apr. 21, 1869 Sept. 29, 1909 Mar., 1907 Esopus Creek Toccoa Olivebridge, N. Y Near Blueridge Ga 239 231 64.4 53 o Apr. 26, 1910 Aug 23 1901 San Gabriel San Gabriel Near Azusa, Cal Near Azusa, Cal Near Soledad, Cal 229 222 215 117.0 215 .0 140 o Feb., 1914 1884 Nov 21 1900 Catskill Creek Fishkill Creek S. Cairo, N. Y Glenham, N. Y 2IO 198 IOO.O 69 2 Spring, 1901 Mar. i 1902 Sweetwater River E. Branch Fish Creek Ramapo River Rio 'Mora Turtle Creek Devil's Creek Santa Ysabel Creek E. Branch Fish Creek Little Stony Creek Wanaque River Putah Creek Cedar River Loramie Reservoir Outlet. . California Taberg, N. Y Pompton, N. J Below Mora, N. Mex East Pittsburg, Pa Near Viele, la Near Escondido, Cal Point Rock, N. Y Near Lodoga, Cal Pompton, N. J Guenoc, Cal Near Seattle, Wash Ohio Macopin, N. J. 186 169 160 159 146 143 128 104 102 101 91 79 72 62 96.0 65 .O 65.8 139-7 6 4 .2 1300.0 50.7 80.5 69.2 83-6 198.9 I2O.O 97-2 90 8 1915 Mar. 27, 1913 Sept. 22, 1882 Sept. 29, 1904 Mar., 1904 June 10, 1905 Jan., 1909 Fall, 1897 Feb., 1909 Oct. 10, 1910 Mar., 1904 Nov., 1911 Mar. 25, 1913 Oct. 10, 1903 N. Fork Cottonwood Creek Six Mile Creek Elkhorn Creek Ono, Cal Ithaca, N. Y Keystone, W. Va 52 46 44 77-7 185.0 1363 .0 Feb., 1909 June 21, 1905 June 22, 1901 Basic Creek Freehold, N. Y 4i 38 81 .0 84 o Spring, 1901 Feb 6 1896 Arroyo Seco Bear Grass Creek Devil's Gate, Cal Louisville, Ky Near Bridgeport, Conn. . . 30.5 27-5 25 o 352.0 IOO.O 157 o Feb., 1914 Feb. 22, 1908 July 29, 1905 Pinal Creek Globe, Ariz 25 o 560 o Aug. 17, 1904 Bakersville, N. C 22 .O 1341 .0 May 20, 1901 Willow Creek 20 1800 o June 14 1903 Yuba River 19 o 368 Mill Creek Erie Pa 12 9 850 o Aug 3 1915 EXTREME FLOOD DISCHARGES 595 TABLE XLIIL EXTREME FLOOD DISCHARGES Continued Stream Locality Drain- age Area, in Sq. Miles Maxi- mum Dis- charge in Cu.ft. per Sec. per Sq. Mile Date of Flood Goodyear, Pa. . . 12 2 96 o Jan. 30 1911 Mill Brook Sunland Wash Estanzuela Starch Factory Creek Rio Grande Sherburne, N. Y Near Pasedena, Cal Near Monterey, Mex New Hartford, N. Y Near Culebra, Panama. . . Cherryvale Kans. 9-4 6-5 3-5 3-4 2.3 2 O 241 .0 712.0 825.0 151 .0 161 .0 930 o Sept. 4, 1905 Feb., 1914 Aug. 28, 1909 July ii, 1905 May 25, 1911 Utica, N. Y. . I i I2O O Mar 25 1904 Beacon Brook II. EUROPEAN STREAMS: Durance River Allier River Pishkill, N. Y Bonpas, France At junction with Loire, France Mirabeau France. 0.2 5714 5548 4533 32OO.O 37.0 30.0 52 o July 14, 1897 Nov. ii, 1886 1856 Nov. ii. 1886 Allier : Vistula Nevers, France Gracow Galicia 4500 3180 37-0 34 o 1813 Rhine Oder At Lake Constance, Switz. Sagan, Silesia, Germany . . Galicia, Austria. 2555 1638 1420 48.0 43-0 64 o July 31, 1897 1897 Eder River At junction with Fulda, 1298 35 .0 Jan., 1841 Verdun River Germany At junction with Durance, 932 63 .0 Nov. i, 1843 Glatzer Neisse Ardeche Werre Eder Buech Bober France Silesia, Germany At junction with Rhone, France At mouth, Germany Hemfurt, Germany At junction with Durance, France 906 831 575 552 552 467 47-0 382.0 48 .0 32.0 58.0 84.0 91.0 1827 Feb., 1799 Nov., 1890 Nov. i, 1843 July, 1897 Hotzenplotz Ubaya At junction with Oder, Germany At junction with Durance, 302 361 77.0 127 .0 July 21, 1903 Nov. i, 1843 Coulon Bleone Moselle Asse River. France Epinal, France At junction with Durance, 352 351 313 285 IOO.O 116.0 90.0 i ii .0 Nov. i, 1843 Wupper Ardeche France At mouth, Westphalia, Germany Vans France. .... 240 215 90.0 525 .6 1890 Bober River Queis River Rohrlach, Germany Lauban, Germany 204.6 187.4 160. i 161 . 2 July 30, 1897 July 30, 1897 596 TABLES TABLE XLIIL EXTREME FLOOD DISCHARGES Continued Maxi- Drain- mum Dis- Stream Locality age Area, charge in Cu.ft. Date of Flood in Sq. Miles per Sec. per Sq. Mile Ardeche Aubenas, France 178.0 694.41 1890 Queis River Marklissa, Germany 118.0 262 . 7 Aug. 3, 1888 118.0 233-3 July 30, 1897 Queis River Greiffenberg, Germany . . . 78.0 172.0 July 30, 1897 Bargaglino Creek Genoa, Italy 35.6 485.0 Oct., 1892 ' 1 ' 35-6 421 .0 July 18, 1908 Eyach River Balingen, "Wurtemberg . 2 A 7 C 7 CfS O June 5 1805 Urnasch St. Gallen, Switzerland o--f / ;> 30 o OOvJ . u T r ? o Goldbach. At Arnoldsdorf, Germany TO 7 1 DO *J 268.8 July 21, 1 903 Queis River Near Head, Germany. . . . *y / 12.34 358.0 July 31, 1897 Little Aupa Near Head, Germany .... ii .9 385.63 Furens River St. Eitenne, France 9.65 478.0 1849 Bargaglino Creek Above Genoa, Italy 8.8 732.0 Oct., 1892 Eyach River Margarethausen, Wurtem- 7-34 788.8 June 5, 1895 burg Dabrowka Creek Near Sambor, Austria. . . . 5-02 253.2 III. INDIAN STREAMS Irawaddy India 149,800 12.7 Khrishna India 345 342.6 Tansa. India. 52 667 . o Professor Kuichling has proposed a formula for maximum discharge which he calls especially applicable to the South Atlantic States: Q= 41.6(620+10 2 4 +M Fanning gives the following: in which Q = Maximum Discharge; M = Drainage area in square kilometers. Neither of these formula makes allowance for differences in rainfall, grade or steepness of country, character of soil or EXTREME FLOOD DISCHARGES 597 topography, all of which, especially the first, have great influence on the volume of maximum discharge. Colonel Ryves has derived the following formula from experience in India: in which M is area in square miles, D is the flood discharge, and C is a coefficient varying with the rainfall and slope of the country. For regions where maximum rainfalls are from 4 to 5 inches in twenty-four hours, the values of C in the above formula have been found to be in flat country C equals 400 to 500; in hilly country C equals 500 to 650. A formula is here proposed as follows: in which R equals the maximum rainfall in inches in twenty- four hours; C varies from 100 for undulating areas, to 200 for mountain- ous areas; and M equals area in square miles. None of these formulae can be expected to give approximate results, on account of the many complications involved, and the uncertainty of all the data except the area of drainage basin. The shape of the basin, the character of the soil and vegetation and many minor factors which affect the result, are impossible to allow for with any approach to accuracy. Cost and Dimensions of Some Great Storage Reservoirs. In Table XLIV are given the capacities, material, dimensions, purpose and cost per acre-foot of some of the great storage reservoirs built by the U. S. Government for irrigation. 598 TABLES TABLE XLIV. RESERVOIRS BUILT BY U. S. RECLAMATION SERVICE Name and Locality Area, Acres Capacity, Acre-feet Annual Draft Cost Year Built Roosevelt, Ariz East Park Cal. 16,832 i 850 1,365,000 5 1 ooo 450,000 30 ooo $3.883,000 IQII Deerflat Ida 9 835 177,660 177,660 Jackson Lake, Ida Minidoka, Ida Arrowrock Ida. 25-530 ii,350 2,860 789,000 150,000 250,000 700,000 53,500 200,000 1,253,000 6go,ooo IQI5 1906 Pathfinder, Wyo Minatare, Neb 22,700 2,240 1,070,000 67,025 500,000 67,025 1,827,000 564,000 1909 1914 Lahontan, Xev MacMillan, N. Mex.* Avalon, N. Mex Elephant Butte, N. M Cold Springs, Ore Clear Lake, Ore.-Cal Belle Fourche, S. D Strawberry, Utah Bumping Lake Wash 12,000 7,86o 970 40,080 1,500 25,000 8,010 8,370 290,000 70,000 6,200 2,368,000 50,000 462,000 203,000 100,000 290,000 40,000 720,000 40,000 10,000 203,000 IOO,OOO 1,580,000 143,000 4,866,000 446,000 138,000 1,237,000 612,000 1915 1892 1912 1916 1908 1910 1911 1913 1910 Lake Kachess, Wash Lake Keechelus Wash 4,800 2 55O 210,000 l8o,OOO 840,000 1912 1917 Shoshone, Wyo 6,600 70,000 47O,OOO 1,350,000 1910 * Built by Pecos Irrigation Co. EARTH DAMS AND ROCKFILL DAMS 599 TABLE XLV. EARTH DAMS AND ROCKFILL DAMS Name and Locality Purpose BUILT Crest L'gth Maxi. Hight Volume, Cu. Yd. Cost By Year Arrowhead, Cal Calaveras, Cal Horseshoe Bend, Can .... Las Vegas, N. M Sugar Loaf, Col San Pablo, Cal Talla, Scotland Dixville, N. H Laramie River, Wyo Power Domestic Irrig. Irrig. Indus. Domestic Domestic Power Irrig. Irrig. Private Private Private Public Private Private Public Private Private 1908 1901 1894 1911 1897 1893 1899 1884 1875 1890 1893 1895 1914 1913 1872 850 1,300 7,000 1,400 5,ooo 1,300 1,050 500 8,000 12,709 3,900 635 480 I2OO 975 380 565 1,686 IOO 2,200 850 640 1,380 1,686 470 550 365 1,300 I, IOO 1, 060 2,080 505 425 57 4i 75 33 40 30 47 222 24O 45 75 40 165 80 76 34 58 47 41* 54 116 190 76 161 52 83 50 93 95 48 52 55 69 101 IOO 77 106 265 IOO 1,273 886 1312 510 682 351 78i 3,085,000 1,000,000 450,000 90,200 1,500,000 500,000 83,500 344,000 127,655 54-400 44,965 86,946 200,000 40,000 170,000 17,000 124,000 143,000 200,000! I.IOO.OOO 1 151,521 Balmorhea Tex Irrig. Irrig. Domestic Domestic Power R. cont'l Irrig. Domestic Irrig. Irrig. Irrig. Domestic Domestic Private Private Public Public Private Public Private Private Private Private Private Public Public Public Public Public Private Private Private Private Private Private Private Private Private Private Private 84,000 732,000 2,130,000 21,000,000 37,159 180,000 102,400 McAlester Okla. Xinder River Eng. Necaxa, Mexico Gatun, Panama Escondido, Cal Lower Otay, Cal McMillan, N. M E. Canyon Creek, Utah . . Merced, Cal San Andres, Cal Pilarcitos, Cal Pecos Valley, No. i, N. M. Pecos Valley No 2 N M 38,000 680,000 651,000 306,000 5S,ooo 270,400 58,890 497,250 41,808 7.6,634 42,510 59,800 La Mesa, Cal Lagastrello Italy Irrig. Irrig. Domestic Flood Power Domestic Power Power Power Power Power Power Power , Domodossola Italy. Sevier R., Utah Morris, Conn . Throttle, N. M Somerset Morena, Cal Bowman, Cal Seros Project Dams: No. i No. 2 No 3 No. 4 No. 5 No. 6 No. 7 1 With accessories. 600 TABLES TABLE XLVI. MASONRY DAMS Name and Locality Purpose BUILT Crest L'gth Max. Hight Volume, Cu. Yd. Cost By Year Arrowrock, Ida Ash Fork, Ariz Assiout, Egypt Assuan, Egypt Auckland, N. Zealand Azischos, Maine Irrig. Railroad Irrig. Irrig. Domestic Power Domestic Irrig. Power Public Private Public Public Public Private Public Public Private Public Private Public Public Public Public Public Public Public Public Private Public Public Private Public Public Public Public Private Private Public Public Public Public Public Private Public Public Private Public Private Private Public Public Public Private Private Private Private Public Private IQI5 1898 1902 1912 1870 1909 1903 1911 1912 1890 1897 1891 1912 1906 1870 1886 1908 1892 1902 1909 1911 1914 1910 1894 1916 1891 1866 1875 1882 1913 1904 1873 1913 1904 1913 1912 1890 I9IS 1913 IIOO 300 2769 6400 533 881 715 625 472 784 363 580 3296 4067 918 2150 670 530 640 580 811 1300 787 755 986 IIOO 170 IIIO 250 590 1674 476 330 700 771 492 233 410 755 1200 4OO 1300 1210 834 IO8O 140 677 207 1850 4278 349 46 48 131 7i 78 157 188 185 95 240 92 ITO 6 4 130 203 114 78 US 42* 125 102 180 585.130 1,500 221,694 1,179,000 132,000 140,000 320,000 4,684 60,000 332,000 255,327 27,000 50,000 58,400 146,242 4,404,000 45,776 2,450,000! 18,660,000 190,000 465,000 Badana Italy Barker Colo 3,68o,ooo 2 133,528 570,000 170,000 404,800 i,4i6,ooo 4 i,500,ooo 3 370,000 130,000* Barren Jack, Australia .... Big Bear Valley, Cal Beetaloo, Australia Betwa, India Bhatgur, India Bober, Germany Boonton, N. J Boyds Corner, N. Y Brasimone, I + alv Irrig. Irrig. Domestic Irrig. Irrig. Power Domestic Domestic Domesdc Domestic Domestic Domestic Domestic R. cont'l Domestic Domestic Domestic Domestic Irrig. Domestic Irrig. Domestic Irrig. Power Fid. prot. Power Domestic Domestic Irrig. Irrig. Power Power Domestic Domestic Irrig. Domestic Indus. Power Domestic Power Bridgeport, Conn Cabbage Tree, Australia. . . Cataract, Australia Chartrain, France Chaustiere, Canada Chuviscar, Mexico Coolgardie, Australia Cross River, N. Y Croton Falls, N. Y Crowley Creek, Ore Derwent, England East Park, Cal Einsidedel, Germany Elephant Butte, N. M . . . . Folsom Cal 1,602,000 420,000 174 197 170 173 60 114 139 93 318 98 170 112 154 121 70 96 197 76 50 96 124 25 117 100 61 47 310 37 156,467 290,540 800 1,389,120 12,500 12,200 3I,6OO 6O5,2OO 48,590 52,300 8,5OO 325,000 14,422 24,000 I4O,OOO 155,727 312,500 4,913,000 318,000 Furens France Gem Lake Cal 874,000 109,194 114,290 46,000 Gorzente, Italy Granite Springs, Wyo Habra, Algiers Male's Bar, Tenn Hatfield, Wis Hemlock, Conn Henne, Germany Hindia Barrage, Mesopot.. Howden, England Huacal, Mexico Hume-Bennett Indian River, N. Y Kensico, N. Y Keokuk, la 4,988 2,207 913.050 Contract price. - Estimated. Approximate 4 With accessories. MASONRY DAMS 601 TABLE XLVI. MASONRY DAMS Continued Name and Locality Purpose BUILT Crest L'gth Max. Hight Volume, Cu. Yd. Cost 550,000 500,000 630,000 300,000! 243,750 By Year La Boquilla, Mexico La Grange, Cal Irrig. Irrig. Domestic Irrig. Irrig. Domestic Irrig. Flood Irrig Irrig. Domestic Domestic Domestic Irrig. Power Flood Domestic Domestic Irrig. Irrig. Domestic Irrig. Power Irrig. Domestic Irrig. Domestic Power Domestic Irrig. Domestic Domestic Domestic Domestic Domestic Domestic Domestic Domestic Storage Flood Power Domestic Private 1894 1902 1904 1909 1895 1913 1905 1912 1913 1905 1917 1906 1911 1905 1878 1909 1897 1892 1911 1907 1914 1889 1898 1910 1893 1916 1905 1888 1891 1895 1913 1904 1889 1878 1906 1902 1894 1907 1843 840 320 1800 710 5136 360 840 880 427 918 1580 535 2IOO I20O l800 490 750 1 IOOO 14650 432 1231 1125 480 592 580 643 200 50O 155 552 1250 380 8800 534 148 741 T350 547 900 1476 600 385 367 1400 205 261 129 87 227 98 135 98 200 I 4 8 203 180 133 131 IOO 238 85 132 88 251 H3 218 173 82 280 135 225 151 146 68 328 98 50 150 144 98 118 124 109 50 190 136 170 160 228 75 46 95 217 123 390,000 39,500 92,000 103,000 360.000 32,500 37,400 140,000 83,700 332,000 205,000 28,000 353,000 8,300 855,000 92,000 85,000 36,200 488,200 60,210 185,000 22,886 342,325 63,000 139,000 28,511 78,576 35,887 180,000 20,507 408,520 149,000 260,000 Lake Cheesman, Cal Lake Fife India Public Private Public Private Private Public Private Private Public Public Public Public Private Public Public Public Public Public Public Public Private Private Private Private Private Public Public Private Public Private Public Public Public Private Public Publ'.c Private Public Public Private Public Private Public La Prele Wyo Lauchensee, Germany Lister, Germany Little Bear Valley, Cal. . . . 595,000 1,416,000 200,000 5,000,000* 90,000 6,886,872 540,000 204,000 853,200' 256,000 91,154 3,893,000 400,000 150,000 1,356,000 366,499 234,074 988,000 204,372 933,065! Medina, Tex Mercedes, Mexico Mountain Dell, Utah New Croton, N. Y New Dam, Mexico New Hauser, Mo Olive Bridge, N. Y Pas Du Riot, France Pathfinder, Nebr Periar, India Remscheid, Germany Rio Das Lages, Brazil Salmon River, Idaho San Jose, Mexico San Mateo, Cal Seligman, Ariz Sodom N Y Scovell Creek, Australia . . Spiers Falls, N. Y Swanzy, Wales Sweetwater, Cal Tansa, India Ternay, France Titicus, N. Y Triunfo Creek, Cal Urft, Germany Vyrnwy, Wales Villar, Spain Waldeck, Germany Wauchusetts, Mass Wigwam, Conn Williams, Ariz Wofelsgrund, Germany. . . . Yadkin Narrows, N. C. . . . Zola, Spain 2,957,000 390,000 1,880,9502 2,378,206 150,000 52,833 102,000 274.439 14,887 5,226 26,200 525,000 1 Contract price. 2 Estimated. 3 Approximate. 4 With accessories. 602 TABLES VELOCITY TABLES Tables XL VII to LIII give the values of the mean velocity of water in open channels computed from Kutter's formula: 1.811 , , 0.00281 -+4I.6+ n s 0.00281 ) n The values of n, the coefficient of roughness, to be used in finding v, depend on the roughness of the materials forming the bed and banks of the channel, irregu- larities and imperfections in the bed or banks, curves, eddies, aquatic plants, and other conditions that tend to produce a retardation of flow. Experimental data on the subject are limited and the commonly accepted values of n for specific conditions must be considered as mere approximations. These approximate values, based on a consideration of the data available, are as follows: n = 0.010 for clean, straight channels of planed lumber carefully laid; neat cement plaster; glazed, coated and enameled surfaces in perfect order. n = 0.012 for clean, straight and regular channels of planed boards not in perfect order due to inferior workmanship or age; unplaned boards carefully laid; metal flumes of the smooth interior type and gentle curvature in alinement; concrete linings having steel troweled surfaces of i : i mortar, sand and cement plaster; clean brickwork. n = 0.014 for clean, regular channels of concrete having wooden troweled or formed surfaces of good construction, the alinement consisting of tangents connected by gentle curves; unplaned boards not in perfect order due to inferior work- manship or age. n = 0.015 for construction as in the preceding case but with sharp curvature or with deposits of silt on the bottom of channel; straight and regular channels of ordinary brickwork; smooth stonework; foul and slightly tuberculated iron. w = o.o2o for channels of fine gravel; rough rubble; or tuberculated iron; or for canals in earth, in good condition, lined with well-packed gravel, partly covered with sediment, and free from vegetation. n = 0.0225 for canals in earth in good condition, or composed of loose gravel with- out vegetation. n = 0.025 for canals and rivers of tolerably uniform cross-section, slope and direc- tion in average condition. n = 0.030 for canals and rivers in rather poor condition, having bed partially cov- ered with debris, or having comparatively smooth sides and bed but a chan- nel partially obstructed with grass, weeds or aquatic plants. n = 0.035 f r canals and rivers in bad order and regimen, having the channel strewn with stones and detritus or about one-third full of vegetation. VELOCITY TABLES 603 Canals in earth with their channels half full of vegetation may have n ='0.040, and when two-thirds full of vegetation may have n = 0.050. In exceptional cases the value of n may reach 0.060. 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 25. 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 n= 0.035 the velocity is 2.05 feet per second and the discharge 49.2 second-feet; thus showing that with the better channel the dis- charge is 60 per cent greater than with the inferior channel. NOTE. To find velocities for slopes other than those given in this table, multiply the tabular velocity found in the column of " ^ = 52.80 " by ten times the square root of the slope. The velocity thus obtained is accurate for slopes greater than 6 feet per mile, and approximate for all slopes greater than 4 feet per mile. 604 TABLES w oio-=9 MU? o, : t^ 10 (N oo ro oo M inoo w M M M WMCSNOl N(S(SH M PO Tt lOOO t^ Soo-- 9 0^-92 = ^ O'O'O.O'- too' 9 IOO OC 00 rO 4ui oVocooO OM^ro ^^u^.00 00' c _ POPOPOO, ^ OtO^oO OOi-i r> r> in M oo o o 9S'oi- ^ r^OOOOO MCSC-iroro t^u^oO ^ ^ ^OC OO OOOO "SK5 S^S Jo N""O N ro O M 1-1 00 OOiOMOO-3- OiOwOO i^O^Oro t-MioOrO r-O'tt^M OC o OIOO' ' o o - o ro O 'too OOO Tt O ~t^ t^t^-ooocoo OCOCO^^O O fr8I-f 00 TtOO N OroOOM ^tOO-ro O OC O ^- O r- O M PO ^O 00 O M o . $2000- = 9 t^ 000 M TtOO*-<^t Oocorqpo tot^OOiN Ttt/5t^cCO WP^^-IOO ro (NN^roro roro^Tt^t ftTt;tn ui Siooo-= 9 O O OOO ^t 1O O M 1000 O ro to t^- O M ro -*O 00 O'-iN'tiO OOCOO^ ro ** ""'^C OO ro oiooo' 9 Occor.ro toooo 0~ ^^^7 0^ rr.^^0^ 0000'= 9 00 000 ^tO M M M M M "M cT'S M PO M M PO t >O POPO POPO to POOO O r- O O IH oo 10 POO oo OM M PO t OO 00 28SSS? 1 10 100 t~- 00 00 M M M ro PO ro goo' 9 tO IH IO PO M M 10 C\ N t^500 IO IO t M IH OO t M Oi O POOO PO 89'i = d PO 10 r-oo o IH PI PO t 10 O t^-OO O O IH M POPO t IOO O t> Soo* 5" t- o o o r- 00 OO tOO O M POPOPON M 000 10 PO OOO 10MOO t M t^POO\ IO IH of -t)z= j M tO t- O\ M M PO t 1000 t^oo IH IH M .PO PO t t tOO froo-=s- 1/5 o n\ 00 POOO POOO zi'iz j MM'SSeT 00- =s M M IO PO M M r O O O O J^ t>00 00 MOO tOO M 10OMO Sioo-=s- SoSSS OOO t t^-OO o o Z6-L- M M POtt 10OO t- t- OOOO OO^ oioo- = S" M MOO tO 10 o 10 o PO 1OOO IH t t> M roo O M t>OM t O r t r oooo o ao M M M M M M -o tino 6000* OIH Ooo M M O O M 00 M OO M PO HI t t^ 00 00 00 t^O O POO O M PO O 1OOO M POO 00 M POO 00 OiO OiOi M M N POPO ttioioo O O t~ t^ t^. 00 00 00 00 O O\00 O M M M M M t t 1C 8000- = s M O PO O\ O M 00 IO OO t^ O IH O t^ 10 OPOO PO l> O IH M POO O PO o2r O 10 O too MtOt^OM t- t^OO 00 00 oo ooo\a O M M PO t IT) Looo-=s O t- POOO PO ^M^SPO O O ts ooo w POO OM to oo M PO 000 IO t- O M t tfOM O g6g-=j 00 OO 00 O O\ O\OiOO M M PO t POOO r-M M C\ IOOO O M IH O t~- t O 10 O- ro t^ O M PO t IO ooo to 10 M M M PO 10 10 1000 O O t- t^ t-- f-00 00 00 00 00 OOO Oi 2 S 2 2 Sooo - = $ 0^9 ' z _tj M to - ZII'Z jj ro 10 t 7 M 101010100 M M nlSrS "MM^ tt^o.t O 00 O M t O 00 O M PO <0000 OM Ol M VO t- OM tO 5 OO PO 0. 10 O M PO tO MO tt- 00 O M M PO too t- o o to r- o M M M M P0100 r-oo r- ro M O M O o o >*" Siooo - = 9 1 10 POOO o M O 00 O M t^- O O OO O IH O PO 1000 O PO t 100 00 N t too r- 00 M N PO oo 00 O O O t too r-oo POOO t O tO 00 M ^ rojj JOOO j-oo 2SS3 SS'^^^^^^^'S^^^^^ C 900- =.9 rt Ooo >-i "3 t~- f) en in 89 ' ie= ^ W ro 't w 'tO O 00 i-i k, K' c o-= 5- ' ' 4o ' oe od o M M* <4 4 4 O R tools' ^ H$H t^roa^M P4 21-12- j/ fe 00- = .9 10 - t^ 00 00 00 Oi w Sioo-= S' OOCOO O. 10 t^iOM TO 10 ro O O O M O,O M 00 rooc fO t- M to Oi fOO O "to 00 8 z6 L d ^^^o ooo oo Q 0100'= s ' M oi ci n n r^ 4 4 ^> w ui lAo'o p 4 ^F^ ?^" u H C/2 6000'= S' *!?n? ^444^^2^ C^OOC. ro^foio^ u,trocso ooo^tc.0 S 8000-= s H , W a OOO'= S 1 ------ 1O.IOO OO OOt^t^t^ t- t^oo OOOOOOOOOOO\O\O\OOOi-i i-i 14 > i rt 9000'= S' ^^.^^^t^ H H i-ooo-=s- VOMU,OOC 10^0 r^u, ^C^^tO S > fe t-ooo - = s 10 fOO C?v _ 't _ 0, _ fO _ _ < 't^t't-t't loioioioio 1010000 oooot^ t^t-t^oooo oo > H i ( w -.=5 fOf'5'tTl-Tt rl-'t't't^t 10 10 10 10 10 10 10 100 O t- t- t- U o 2000'= S 1 ^^ roio ^ H. ro -t 000 O M ei "t^.Ooc OMro^iOO t^ooOO ^^ r 7t U ? 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O 'tOO M ON M OO M OO M M Tt t to t OO O 00 t M t^ oo 00 t ON t O> t ON OOOO M O M 10 ON M O O 1 1^ M 00 to O t l7 =$ ZI-IZ = OOMMOOIO M oo oo ON t ON 'too 00 l^ MOO 'too M O ON OOO Ooot-OoO OOOOt^O MMOooot lOiOOOt^ t^oooOONO\ OO-' l - < M nc\ic^oooo rt't'T'totoOoOONM eoo- = g d M t- ON 1-1 ONO < -OOOO OOONONOlO OOMMM MMMOOl ZOO' =S 9$-oi = d OONMM t^ONOoOO t-nioooOM MwOoOO MONTOto ON M M M OO OO <* t -t^OOOO 000 00 O ON ONONON O> O O O O M oo 4 4 Sioo - = g JOOOOCNOv OWM(N 0100-= s 1 o o o oo 6000-= S' '=d M t- M O ON M oo 50 OO OOO C r^ oo O 00 00 O\ O gooo- =5 J s/zz-^ = d 10 10 to to to too OOOOO l^oo 00 ON iooo-=s- 969-9=^ to ON M O 00 M OOOwM't Mt^MOO tOOOOO t^C^OOOO 9OOQ- = <," Wi"=d M oo oo oo oo oo OO tototo toioiotoio ot^t^c ?ooo-= S' ot79'z= j s ZII'Z= J 5^S; =.9 = d t- M O ON M iO( MM M M M M O, M oo t 10 OOOOO OOtOiOrt 00 MMOOOOOO oooooooooo oooO't't't 'ttOtOiO Szooo-=S' O't'tooo OMOOt oo 10 t- ON M M'tiOt^-OO O ON M oo 'f too O t^ t^- t^O Otot OOMMOOO ONt^oot^ ON O M oo Tt too t^ooON OMCsoot too I>oo oo M O O oo zooo^S" Siooo-=s- z6i-=^ 't >O t^OO ON O 0-1 OO 01000-= s" r^oo Ox O i-t o* 0000-= s V()z~ = jj O 10 O 't ON oo c 0oo ^ O 00 O N . " ?. d HI HI HI oioo- = S 00 ^^^OCS O^OMro ^^OOC, ^.^OM r,^^ t-oo U ? N .. t d 6OOO' = 9 COt^- i^O^OOO (NfO^ooCN OoCOfOC 1 O -tO ro Sooo- = 9 rOO M ro ? 7 M -o -tO r- N ro -tO ^ 00 O M * ro -t ^O 092 tooo = ?* ON -t-0 ^ o. ro -to t ? 00 M ro -t u,O ^OO O O M 00 NO M HI &\^C> (N O O o t- a OCNOOOiOrOHi oOOroOt^- rOOOMOO TtOOo O >o O *t ON fOOO N O t^O t N JO goo- =g O \7Z-ZV= t^POI^MON PONOOMM ON>0 M 04 PO 't Tj- IONO r*r-OO OOOvOOM MWC-IPOPO PO^t't^O^O^NONOt^t^ ONMCNIT}- II * 8 ?e:f M M ONVO POON-l>OC\ 'tOO N NO O TOO wiOOCPOON-' w Soo~= s HH Ot-<)Z=d O OOMxOPOlO POt^ONOit^ POt^O \ r foo'= c siS 0;^%o;^oSoT"Soo5ioMS 1 5'M a tMrt^OroOONMTj-^0,M C N, Hemco^rMflirtujOO^t-^OOoooOOa O-OOOM MMMPJN PO TO t- fe O oo-=,9 MMMPOrorott^io^NOvONO t-r-^^oo OOOOONONOl OiCOOO MPOTT fc W 200-= 5- >0 M ^ 00 U,00 H ^t^ U, ^ C , t ^. i =' .00 too M rt^orO^OOO^iOt-ONtOOO ONPOiO^ONMCSTO TMOO^ N rococo ro^'*'*'* wioiotrtujvovovo-o-o NOt-r-t-t-oo aao Q - 0100;- s- 1 too M rf t~ OMtr-O\ HPOior-o> OfNTiot^ ONONPOIO\OOOCNOP* OOOOO U 6000- =g TOO M to Cs M n >o t- a M n -o t- oo o o -iPOTOoOONMts L^ y j iooo- = $ W 969-9=^ MNro^.0 r-ooaMN t-rot>N r- 2" 9000- =s- K 89i'=dr nX ^^^Mro tO^S^ T.0^000 H^^O 00 ON O M O Sooo- = p 0179-2 =J <; OQO ci T.O ^ 0, ro TO ^ 00 H ^ N ro T^^OO 0; 0".?t * I ?*7 H . 1 ? ? ^ frooo- S -r, = J MUSI- 00 Ntiot^oo OMMroT^OoCO.O M N PO T U, t-OC^ 0; 00 ^ M u-iCO OO t^OOONOi-itS POT >OO r- 00 O\ ON O M N N PO T O TOO ^ 1^00 t-i T t^ ON M T 901 J - . y Siooo-=5 t ^ z6L-=d M roToo t-oo ao M N N nrtm oo r- t-oo C^CNOMM NNOOTtt-CNT^a W ^ oiooo < =5' PQ 82S'= 1 >/ < - rOTTPOP* OooOf*5O J^TOt^PO ON"O^-OP M 04 PO T iO O O t^OO O\ O. O M w P4 (NPOTTiO l^ rocx: ^tO\ TO^tC^ l-COOO 00 trjso O t-- r- 00 oo O. Ov O N n r^ O O w H 0000-=^ OiHNNPOTTiOiOOOr^t^oCOO ONOOOO 9 s // uad ;9M MTOOOO P4TOOOO NTvCOCO NTOOOO CN.TOOOO NTOOOO OOO G9JB 0000 MMMMP, (N^MP.rororomrOT TTTT^>0>0^100 t-oo 00 M o, 610 TABLES oio'= " o t N o PO N r- ooo to M to r^ t^ ' CMMOOOIO NOO'TtOO o^ior^-Oi wroioi>C\ Mroi^r^oo ocsroO i O oCON^cs^l" wr^rto u t6'L- d POPOPO 000 00 Q 0100-= s POO OMtOOOOCMt lOt-OOCM ttOOOOO WCMPO IOO 1-OOOWP4 OOPOOOPO o o%zS d CM (N tooo' s* CMt.0^00 OM it 10 .r-oe >00 MCMrotio Ot-^000 O H ,M N co ^ O t ^ fe >< eooo-=. 9 CM PO IOO t- 00 O M CM PO t IOO Ot-~OOOO"M CMPOttlOOr- t^OO O CM IOOO l-l H 8 i d U o Scaeo'-s Mt ozoo-= S ^^ ^cg^^c? ^S^^ 1 ^ %S5^^ o%o"2 ^S"^ ^^t 9 o i ^ t-H Siooo-= 5 1 ^pTS^^ o^^^O g^M^C? S^tSS 00^^^? ^?000 ^J^^O l-l c J S K 01000-= 9 8z'= j 2SS%$ ^5S25SSSS oSErSJ; ftf?^^ --^- ?^t tS ?oooo'= 9 o-^^f?* S35li ^o>oS^ ^5o. ?*ooo 2^SS 4^^ Vgz = jj U3d ^3M CM tO 00 O CM tO 00 O CM tO 00 O R R R R* R R 0. I 0.0887 1 .2702 o . 0066 0.177 o. 1961 1.6962 o. 1156 O. I 0.0587 0.9020 0.0561 0.2 0.2340 1.7462 o. 1340 O.2 0.1635 I .2870 o. 1270 0.3 0.4050 1.9620 0.2064 0.3 0.2955 1.5908 0.1858 0.4 0.5828 2.1736 0.2681 0.4 0.4473 1.8546 0.2413 o.S 0.7656 2.3816 0.3230 0.5 0.6142 2 . 0944 0.2936 0.6 0.9573 2.5869 0.3700 0.6 0.7927 2.3186 0.3410 0.7 I. 1510 2.7900 0.4126 0.7 0.9799 2.5322 0.3870 0.8 1.3478 2.9916 0.4505 0.8 I. 1735 2.7389 0.4285 0.9 I 5407 3.1922 0.4845 0.9 I.37H 2.9412 0.4662 I.O 1-7465 3.3923 0.5148 I.O 1.5708 3.1416 0.5000 . i 1.9462 3.5926 0.5417 i.i 1-7705 3.3419 0.5298 . 2 2.1438 3 . 7949 0.5649 1.2 I .9681 3 - 5443 0.5553 3 2.3374 4.0017 0.5841 1.3 2. l6l7 3-7510 0.5763 4 2.5246 4-2153 0.5989 1.4 2.3489 3 9646 0.5925 .5 2.7031 4-4395 0.6089 1.5 2.5274 4. 1888 . 6034 .6 2.8700 4-6793 0.6134 1.6 2 . 6943 4.4286 0.6084 .7 3.0218 4-9431 0.6113 1.7 2.8461 4.6924 0.6065 .8 3.1538 5 - 2469 0.6011 1.8 2.9781 4.9962 0.5961 9 3.2586 5.6318 0.5786 1.9 3.0829 5.38II 0.5729 2.0 3.3173 6.5339 0.5077 2.O 3.I4I6 6. 2832 0.5000 NOTE. Figures in first, third and fourth columns are to be multiplied, by adopted value of R. Figures in second column, by R-. VELOCITY TABLES 613 TABLE LVI. AREA IN SQUARE FEET, A, AND HYDRAULIC RADIUS IN FEET, r, OF SEMI-CIRCULAR FLUMES FOR VARIOUS VALUES OF FREE- BOARD IN FEET. F Diam- F = 0.2 F = 0.3 F = 0.4 F = o.S F = 0.6 Flume eter No. in Feet A r A r A r A r A r 24 1.273 0-39 0.24 0.27 o. 20 30 I.S92 0.68 0.32 0-53 o. 28 0.38 0.23 0.25 0.18 36 1 .910 1.05 0.41 0.87 0.36 0.69 0.32 0.52 0.27 42 2.228 i.SO 0.48 1.29 0.45 i. 08 0.40 0.87 0.36 0.68 0.31 48 2.546 2.04 0.57 1-79 0.53 1.54 0.49 1.31 0-44 i. 08 0.39 60 3-183 3-34 0.73 3-03 0.69 2.72 0.65 2.41 0.61 2 . II 0.56 72 3.820 4-97 0.89 4-59 0.85 4.21 0.81 3.84 0.77 3-48 0.73 84 4.456 6.91 1.05 6.47 .01 6.03 0.98 5-59 0.93 5.16 0.89 96 5-093 9-17 I .21 8.66 17 8.16 13 7.66 i .09 7.16 .06 108 5-730 ii. 8 1.29 II . 2 33 10.6 .29 10. 1.26 9.48 .22 I2O 6.366 14.6 1.53 14.0 49 13-4 45 12.7 1.42 12. I 38 132 7.003 17.9 1.69 17 .2 .65 16.5 .61 15-8 1.58 I5.I 54 144 7.639 21.4 1.84 20. 6 .81 19.9 77 19.1 1-74 18.4 .70 156 8.276 25-2 2.OO 24.4 97 23.6 93 22.8 1.90 21.9 .86 168 8.913 29.4 2. 16 28.5 .13 27.6 .09 26.7 2.06 25-9 2.02 180 9-549 33-9 2.32 32.9 .29 32.0 25 31.0 2.22 30.1 2.18 192 10. 186 38.7 2.48 37-7 45 36.7 .42 35.7 2. 3 8 34-6 2.34 204 10.823 43.8 2.6 4 42.8 .61 41.7 57 40.6 2.54 39-5 2.50 216 11-459 49-3 2 . 8O 48. i .76 47.0 73 45-8 2.70 44-7 2.66 228 12.096 55-0 2.96 53-8 93 52.6 .89 51-4 2.86 50.2 2.82 240 12.732 61.1 3-12 59-8 3.08 58.6 3-05 57-3 3.01 56.0 2.98 252 13-369 67.5 3.26 66.2 3.24 64.8 3-21 63.5 3.18 62.2 3-14 Diam- F = 0.8 F = I.O F = 1.2 F = 1.4 F = i.S Flume eter No. in Feet A r A r A r A r A r 72 3.820 2.76 0.64 2.08 0-54 84 4-456 4-31 0.80 3-49 0.71 2.71 0.61 96 5-093 6.18 0.97 5-22 0.88 4-30 0.78 3.41 0.68 108 5-730 8.37 1.14 7.28 1.05 6.22 0.96 5-19 0.86 4.69 0.81 120 6.366 10.9 1.30 9.65 I .21 8.46 I . 12 7-29 1.03 6.72 0.98 132 7.003 13-7 1 .46 12.4 1-38 II .O 1.29 9-72 i . 20 9.07 i. IS 144 7.639 16.9 1.62 15-4 1-54 13-9 1.46 12.5 1.37 11. 8 1.32 156 8.276 20.3 1.79 18.7 1.70 17- I 1.62 15-5 1.53 14.8 1-49 168 8.913 24.1 1.95 22.4 1.87 20.6 1.78 18.9 1.70 18.1 1.65 1 80 9-549 28.2 2 . II 26.3 2.03 24.5 1.95 22.6 1.86 21.7 1.82 192 10.186 32.6 2.27 30.6 2. 19 28.6 2. II 26.7 2.03 25-7 1.98 204 10.823 37-4 2-43 35-2 2.35 33.1 2.27 31-0 2.19 3O.O 2.14 216 11-459 42-4 2.59 40.2 2-51 37-9 2.43 35-7 2.35 34-6 2.31 228 12 .096 47-8 2.75 45-4 2.67 43-0 2.60 40.7 2.52 39-5 2.47 240 12.732 53-5 2.91 5i o 2.83 48.5 2.76 46.0 2.68 44-7 2.63 252 13.369 59-4 3-07 56.9 2.99 54-2 2.92 51.6 2.84 50.3 2.80 614 TABLES TABLE LVII. THEORETICAL VELOCITY OF WATER IN FEET PER SECOND FOR VARIOUS HEADS V=\ / 2gh. g =32.16 Head in Ft. O.OO O.OI O.O2 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0. I 2.536 2.660 2.778 2.892 3.OOI 3.106 3.208 3.307 3-402 3.496 0.2 3-586 3.675 3.762 3 846 3.929 4 oio 4.089 4.167 4.244 A -319 0.3 4 393 4.465 4.536 4.628 4-676 4 745 4.812 4.878 4 944 5 . 008 0.4 5.072 5.135 5-197 5 259 5-320 5.38o 5-439 5 - 498 5.556 5-614 0.5 5.671 5.727 S.7S3 5 . 838 5.893 5-947 6.001 6.054 6. 107 6.160 0.6 6. 212 6.263 6.315 6.365 6.416 6.465 6.525 6.564 6.613 6.662 0.7 6. 710 6.757 6.805 6.852 6.899 6.946 6.992 7.038 7.083 7.128 0.8 7.173 7.218 7 . 262 7.306 7-350 7-394 7.438 7.481 7.523 7.566 0.9 7.608 7-650 7.692 7-734 7.776 7.817 7.858 7-898 7-939 7-979 1.0 8.020 8.060 8.099 8 139 8. 179 8.218 8.257 8.296 8.335 8.373 i . i 8.412 8.450 8.487 8.525 8.563 8.600 8.638 8.675 8.712 8.749 I . 2 8.785 8.822 8.858 8.894 8.930 8.967 9.002 9-038 9-073 9. 108 1-3 9 . 144 9.179 9-214 9-249 9 . 284 9-3T8 9-353 9.387 9-421 9-455 1-4 9.489 9.523 9-557 9-590 9.624 9.657 9.690 0.724 9-757 9-790 1.5 9.822 9.855 9.888 9.920 9-953 9.985 10.017 10.049 10.081 10. 113 1.6 10.145 10. 176 10.208 10.239 10. 271 10.302 10.333 10.364 10.395 10.425 1.7 10.457 10.487 10.518 10.549 10.579 10.611 10.640 10.670 10.712 10.730 1.8 10.760 10.790 10.820 10.849 10.879 10.908 10.938 10.967 10.996 ii .026 1.9 11.055 ii .084 ii . 113 11.142 11.171 i i . 199 11.228 11.257 11.285 11.314 Head in Ft. o.o O. I O. 2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 2 II. 3 ii. 6 II. 9 12 . 2 12.4 12.7 12.9 13.2 13-4 13-7 3 13.9 14.1 14-3 14-6 14-8 15.0 15.2 15-4 15-6 15-8 4 16.0 16.2 I6. 4 16.6 16.8 17.0 17.2 17-4 17.6 17.8 5 17-9 18.1 18.3 18.5 18.6 18.8 19.0 19.2 19.3 19-5 6 19.6 19.8 20. O 20. i 20.3 20.5 20.6 20.8 20.9 21 . I 7 21 . 2 21.4 21.5 21 .7 21.8 22. O 22 . I 22.3 22.4 22.5 8 22. 7 22.8 23 .O 23. 1 23 3 23-4 23-5 23.7 23-8 23-9 9 24.1 24.2 24-3 24.5 24.6 24.7 24.8 25.0 25-1 25-2 10 25.4 25.5 25-6 25.7 25.9 26.0 26. i 26. 2 26.4 26.5 II 26.6 26.7 26.8 27.0 27.1 27.2 27.3 27-4 27.5 27-7 12 27.8 27-9 28.0 28.1 28.2 28.4 28.5 28.6 28.7 28.8 13 28.9 29.0 29- I 29.2 29-4 29-5 29.6 29 . 7 20.8 29-9 14 30.0 30. I 30.2 30.3 30-4 30.5 30.6 30.7 30.9 31.0 15 31. 1 31-2 31.3 31.4 31-5 31.6 31-7 31-8. 31-9 32.0 16 32.1 32.2 32.3 32.4 32.5 32.6 32.7 32.8 32.9 33-0 17 33-1 33-2 33.3 33.4 33-5 33 5 33.6 33-7 33-8 33-9 18 34-0 34-1 34.2 34-3 34-4 34-5 34-6 34-7 34-8 34-9 19 35.0 35-0 35- 1 35-2 35-3 35-4 35-5 35-6 35-7 35.8 20 35-9 36.0 36.0 36.1 36.2 36.3 36.4 36.5 36.6 36.7 21 36.8 36.8 36.9 37-0 37-1 37-2 37-3 37-4 37-4 37-5 1 VELOCITY TABLES 615 TABLE LVIII. AVERAGE WEIGHT, IN POUNDS PER CUBIC FOOT, OF VARIOUS SUBSTANCES Substance Clay, earth and mud: Clay Earth, dry and loose Earth, dry and shaken Earth, dry and moderately rammed Earth, slightly moist, loose Earth, more moist, loose Earth more moist, shaken .... Earth, more moist moderately rammed Eaith, as soft flowing mud .... Earth, as soft mud well pressed into a box Mud, dry, close Mud, wet, moderately pressed. Mud, wet, fluid Masonry and its materials: Brick, best pressed Brick, common hard Brick, soft, inferior. . Brickwork, pressed brick, fine joints Brickwork, medium quality. . . Brickwork, coarse, inferior soft bricks Cement, pulverized, loose Cement, pressed Cement, set Concrete, 1:3:6 Gravel, loose Gravel, rammed Masonry of granite or stone of like weight: Well dressed Well-scabbled rubble, 20 per cent mortar Roughly scabbled rubble 25 to 35 per cent mortar Well-scabbled dry rubble Roughly scabbled dry rubble. Masonry of sandstone or stone of like weight weighs about seven-eignths of the above: Weight 122-162 72-80 82-92 90-100 70-76 66-68 75-90 90-100 104-112 no- 1 20 80-110 i 10 130 104-120 150 125 TOO 140 125 IOO 72-105 US 168-187 140 82-125 90-145 165 154 150 138 125 Substance Masonry and its materials Con- tinued. Mortar, hardened Sand, pure quartz, dry, loose. Sand, pure quartz, dry, slightly shaken Sand, pure quartz, dry, rammed Sand, natural, dry, loose Sand, natural, dry, shaken. . . . Sand, wet, voids full of water . . Stone Stone quarried, loosely piled. . Stone, broken, loose Stone, broken, rammed Metals and alloys: Brass (copper and zinc) Broaze (copper and tin) Copper, cast Copper, rolled Iron and steel, cast Iron and steel, average Iron and steel, wrought Iron and steel, average Spelter or zinc Tin, cast Woods, seasoned and dry: Ash Hemlock Hickory Oak, white Oak, red, black, etc Pine, white Pine, yellow, northern Pine, yellow, southern Poplar Spruce Woods weigh one-fifth to one- half more green than dry; and ordinary building tim- ber, tolerably seasoned, weighs about, one-sixth more than dry timber. Weight 90-115 87-106 92-110 100-120 8O-IIO 85-125 II8-I28 135 195 So-llO 77 112 79-121 487-524 524-537 537-548 548-562 438-483 450 475-494 481 425-450 450-470 40-53 25 37-58 37-56 32-45 22-31 30-39 40-50 22-31 25 616 TABLES TABLE LIX. CONVENIENT EQUIVALENTS LENGTH I inch =iV foot =.027778 yard =.000015783 mile =2.54 centimeters. I foot = 12 inches =3 yard =.00018939 mile =.3048 meter. I yard =36 inches =3 feet =.00056818 mile =.9144 meter. I mile =63360 inches =5280 feet =1760 yards = 1.60935 kilometers. I meter = 100 centimeters =.ooi kilometer =39-37 inches =3.2808 feet = 1.0936 yards = .0006213? mile. SURFACE I square inch =.006944 square foot =.0007716 square yard =.0000001594 acre =.000000- 0002491 square mile =6. 45163 square centimeters. I square foot =144 square inches = square yard =.000022957 acre -.00000003587 square mile =.092903 square meters. I square yard =1296 square inches =9 sqiiare feet =.0002066 acre =.0000003228 square mile = .83613 square meter. I acre =6272640 square inches =43560 square feet =4840 square yards =.0015625 square mile =208.71 feet square =.404687 hectare. I square mile =4014489600 square inches =27878400 square feet =3097600 square yards = 640 acres =259 hectares. I square meter = 10000 square centimeters =.0001 hectare =.000001 square kilometer = 1550 square inches = 10.7639 square feet =1.19598 square yards =.0002471 acre =.0000003861 square mile. VOLUME I cubic inch =.004329 U. S. gallon =.0005787 cubic foot = 16.3872 cubic centimeters. I U. S. gallon =231 cubic inches =.13368 cubic foot =.00000307 acre-foot =3.78543 liters. I cubic foot =1728 cubic inches =7.4805 U. S. gallons =.037037 cubic yard =.000022957 acre-foot =28.317 liters. I cubic yard =46656 cubic inches =27 cubic feet =.00061983 acre-foot =.76456 cubic meter. I acre-foot =325851 U. S. gallons =43560 cubic feet = r6i3i cubic yards = 1233.49 cubic meters. I cubic meter, stere or kiloliter = 1000000 cubic centimeters = 1000 liters =61023.4 cubic inches =264.17 U. S. gallons =35.3145 cubic feet = 1.30794 cubic yards =.000810708 acre-foot. HYDRAULICS I U. S. gallon of water weighs 8.34 pounds avoirdupois. i cubic foot of water weighs 62.4 pounds avoirdupois. I second-foot =448.8 U. S. gallons per minute =26929.9 U. S. gallons per hour =.646317 U. S. gallons per day. = 60 cubic feet per minute =3600 cubic feet per houi =86400 cubic feet per day =31536000 cubic feet per year =.000214 cubic mile per year. = .9917 acre-inch per hour = 1.9835 acre-feet per day =723. 9669 acre-feet per year. = 50 miner's inches in Idaho, Kansas, Nebraska, New Mexico, North Dakota, and South Dakota =40 miner's inches in Arizona, California, Montana, and Oregon =38. 4 miner's inches in Colorado. = .028317 cubic meters per second = 1.699 cubic meters per minute =101.941 cubic meters per hour =2446. 58 cubic meters per day. I cubic meter per minute =.5886 second-foot =4.403 U. S. gallons per second =1.1674 acre-feet per day. I million gallons per day = 1.55 second-feet =3.07 acre-feet per day =2. 629 cubic meters per minute. second-foot falling 8.81 feet = i horse-power, second-foot falling 10 feet = 1.135 horse-power, second-foot falling 1 1 feet = i horse-power, 80 per cent efficiency, second-foot for i year will cover i square mile 1.131 feet or 13.572 inches deep, inch deep on I square mile =2323200 cubic feet =.0737 second-foot for I year. CONVENIENT EQUIVALENTS. 617 MISCELLANEOUS I foot per second =.68 mile per hour = 1.097 kilometers per hour. I avoirdupois pound =7000 grains .4536 kilogram. I kilogram =1000 grams =.ooi tonne =15432 grains =2.2046 pounds avoirdupois. {15 pounds per square inch. i ton per square foot. I kilogram per square centimeter. Acceleration of gravity, & =32.16 feet per second. I mil =.ooi inch. i circular mil = (.ooi) 2 or .0000007854 square inch. 4 i square inch =1273240 circular mils. No. 10 Birmingham gage wire has a diameter of 134 mils and a cross-sectional area of 17956 circular mils. i horse-power =5694120 foot-gallons per day =550 foot-pounds per second =33,000 foot- pounds per minute = 108,000 foot-pounds per hour =2545 B.T.U. per hour =76 kilo- grammeters per second = 1.27 kilogrammeters per minute =746 watts. i horse-power boiler rating, requires the evaporation of 343 pounds per hour of water at 212 F. to dry steam at the same temperature; or the expenditure of 33,317 B. T. U.; and in practice is developed by burning 3! to 4$ pounds per hour of coal under 10 to 12 square feet of heating surface. I B.T.U. =778 foot-pounds. i pound of bituminous coal contains about 14,100 B.T.U. or 11,000,000 foot-pounds of energy. INDEX "A" frame dams described, 384 Abandoned irrigated lands, 185 Acoustic current meter, 156 Acre-foot, definition of, 165 table of equivalents, 616 Acre-inch, definition of, 165 Advantages of irrigation, 5 Agricultural Department experiments on duty of water, 143-145 Agua Fria, underground waters, 47 Air in running water, 293 Air-lift pumping, 92 Alcohol pumping engines, 85, 86 Aldershot, sewage irrigation at, 126 Alexander, W. H., book by, 63 Alfalfa as a nurse crop, 105, 106 as preventive of alkali, 13 Algeria, area irrigated in, 4 Alinement of canals, 212-215 Alkali, concrete lining protection, 238 in canals, prevention of, 521 or injurious salts, 8-15 rise of, brief discussion, 190, 191 resistance to, table, 11,12 tests of cement pipe, 199, 200 Alkaline salts, discussion of, 8-15 soils, effect on metal, 308-314 Allegheny River, flow and area, 592 Allier River, France, flood, 595 All Saints Church, pressure on founda- tion, 447 Alluvial soils, definition of, 7 Alvord, J. W., book on floods, 63 Ambursen type dam, mention, 487. See Hollow Dams. American River, flood and area, 593 flow of, 42 Folsom dam, 385 American Society of Agricultural Engi- neers, data, 148 Analysis of soils, table, 9 Shoshone Dam, illustrated, 474 Ancient irrigation works, mention, 2 Androscoggin River, flood and area, 592 Anticlinal valley as reservoir site, 345 Application of water to land, 111-136 Appropriation, water, doctrine of, 496- 500 Appurtenance to land, water rights, 500, 501 Aquatic plants, growth of, 521-524 Aqueduct, Ganges Canal, India, 301 Nadrai, India, 313 Strawberry Valley, illustrated, 336 Arabs, irrigation by, in Sahara, 62 Arch Bridge pressures, 447 dam, definition of, 443 dams, design of, 469-474 spillway, East Park, 485 Ardeche River flood, France, 355, 595, 596 Areas irrigated in countries, table, 4 reservoirs, table, 598 -- river drainage basins, 592-596 Argentina, area irrigated, 4 Arizona Canal, data about, 230 Arkansas River, flow of, 42 Arrowhead Dam, height and length, 599 Reservoir, evaporation, 71 Arrowrock coffer dam, illustrated, 402 Dam, and gunnite, 452 balanced valve, 365 data, 600 plans and section, 458-460 pressure, 447 specifications, 535-546 Reservoir, area, cost, etc., 598 619 620 INDEX Arroyo Seco, flood and area, 594 Artesian areas, 50, 51 wells, 48-59 books on, 63, 64 Ash Fork Dam, Arizona, 487-490 data, 600 Ashti Dam, India, data, 599 Asse River, France, flood, 595 Assiout Dam, Egypt, data, 600 Assuan Dam, data, 600 silt removal at, 376, 377 steel canal below. 241, 242 Assyria, records of irrigation in, 2 Auckland Dam, data, 600 Aupa River, Germany, flood, 596 Ausable River, flood and area, 593 Australia, area irrigated in, 4 Goulburn Weir, 397 Rainfall records, 356 regulator gates in, 254 Australian salt-bush and alkali, 13 water meter, 177 Austrian Soc. E. and Arch., pressure data, 447 Automatic recording gage, 160, 161 shutters and gates, 392 spillways, 275-277 - Tieton, 280-282 Avalon Dam failure explained, 422 Reservoir, area and capacity, 598 Azischos Dam, data, 600 Azusa hydrant meter, 173 B Babylonia, records of irrigation in, 2 Backfilling over drain tiles, 197 specification clause, 559 Bacteria, sewage irrigation and, 128 Badana Dam, data, 600 Baker, I. O., pressure data, 447 Baker, M. N., book on sewage, 64 "Baffle piers" at dams, 477, 478 Balanced valves, 360, 365 illustrated, 364-369 Balmorhea Dam, data, 599 Ban Dam, France, data, 600 Barage du Nil, mention of, 387 Bargaglino Cr., Italy, flood, 596 Bark, Don H., address by, 26 article by, 15 book by, 152 bulletin by, 183 seepage data, 234 Barker Dam, data, 600 Barossa Dam, data, 6co pressure, 447 Barrin Juick Dam, data, 600 Basic Creek, flood and area, 594 Bassano Dam, design mention, 477, 478 Baum Co., F. G., constant angle dam, 472 Bazin formula, pipe, 326 Beacon Brook, N. Y., flood, 595 Bear River, flood and area, 594 flow of, 44 canal drop, 285 crib dam, illustrated, 401 Bear Grass Creek, flood and area, 594 Bear Valley Dam, plan and section, 473 pressure on, 447 Bear Valley Dams, Big and Little, 600, 601 Beaumont rice pumping plant, 98 Beavers, first dam makers, 382 Beetaloo Dam, data, 600 "Before and After" irrigation views, IOO-IOI Belle Fourche Dam, paving, illustrated, 418 material used, 423 gravel blanket on, 436 outlet works of, 358 section of, 406 Reservoir data, 598 tunnel data, 334 Bench marks, specification, clause, 553 Beneficial uses of water, law of, 497, 499 Berlin, deep well near, 51 Betwa Dam, India, data, 600 weir flashboards, illustrated, 393 * Bezwara Weir, India, section, 391 Bhatgur Dam, India, data, 600 Big Bear Valley Dam, data, 600 Bigelow, F. H., paper on evaporation, 71 Billings, Mont., analysis soils, 9 INDEX 621 Bjorling's formulas for water wheels, 80, 82 "Black Alkali," definition of, 8 Black Lick River, flood and area, 594 Bleone River, France, flood, 595 Bligh, W. G., book by, 495 pressure data, 447 Blue Nile, irrigation waters of, 25 Boat gaging station, illustrated, 162 Bober Dam, Germany, data, 600 River, Silesia, flood, 595 Boise canal dam and gates, illustrated, 255 chute and stilling basin, 291 pipe manufacture, illustrated, 328, 329 project, cost of canal lining on, 243. See also Arrowrock Dam. River, flow of, 43 hydrograph of, 34 Valley, analysis soils, 9 ground water charts, 186-189 steel flume in, 307 Bond, specification clause, 548 Boonton Dam, N. J., data, 600 Border methods of irrigation, 112-117, 124 Borings, dam foundations, 493, 494 Borrow pits, specification clause, 558 Bowman Dam, data and section, 437, 599 Bow River, flow of, 44 Box turnout, U. S. R. S.,' plans, 267 Boyds Corner Dam, data, 600 Brasimone Dam, data, 600 Brazil rainfall records, 356 Breaks in canals discussed, 271 Breast-wheels, description of, 81 Bridge Pont-y-Prydd, pressure on, 447 Bridgeport Dam, data, 600 Bridges over canals, 335-337 steel, specifications, 579-584 Briggs, L. J., book by, 25 investigations of, 20, 21 Broad River, flood and area, 593 Brodie data on masonry pressure, 447 Brooklyn Bridge, pressure on, 447 Brown, Hanbury, books by, 152, 527 Buck scraper, description of, 229 Buckley, R B., book on irrigation by, 71 Budlong Creek, N. Y., flood and area, 595 Buech River, France, flood and area, 595 Bumping Lake Dam data, 598 section, 433 Burdick, C. B., book on floods, 63 Bureau of Soils, analyses by, 9 Bureau of Standards alkali tests, 199, 200 Burkholder, J. L., article by, 201 Chart of Rio Grande, 187, 1 88 Burns Creek, superpassage, illustrated, 3i6 Burrin Juick Dam, pressure, 447 "Burro" Dam described, 382 Burrowing animals, 525, 526 Butterfly valves, illustrated, 362, 366, 367 By-pass, Umatilla Canal, 288 Cabbage Tree Dam, data, 600 Cable station, stream gaging, 161 Cache La Poudre, flow of, 42 seepage to, 245 Cain, Wm., book by, 495 Cairo, Barage du Nil near, 387 Calaveras Dam, data, 599 failure of, 429, 430 River, flood and area, 594 Calcium carbonate and alkali, 14 California, irrigation in, book on, 63 rainfall records, 356 State Board of Health, 5 stovepipe well drilling, 57 Galloway Canal, Cal., silt in, 25 weir at, 388-390 Camp, specification clause, 537 Canada, area irrigated in, 4 Canada Creek, W., N. Y. flood, 594 Canal cross sections, illustrated, 204 lining, 236-245 losses and prevention, 233, 234 riders, duties of, 503 specifications, 557-559 structures, chapter on, 247-369 622 INDEX Canal superintendent, duties of, 502, 503 zone, rainfall records, 357 Canals, list of U. S. R. S., 230-232 and laterals, chapter on, 202-246 Cane Creek, flood and area, 594 Canvas Dam used in irrigation, 112, 113 Canyon Creek Dam, Utah, data, 599 Capillarity of soils, table of, 18 Capillary movement in soil, 16, 17, 1 8 Carbon dioxide in tunnel, 335 Carbonate of sodium, 8, n Carey Act, mention of, 3 Carlsbad canals, lining and costs, 242 Carpenter, L. G., book on duty of water, 152 bulletins by, 182, 246 experiments, return seepage by, 245 Carson River, East, flow of, 43 regulator, 251-257 Carver's data on hydraulic rams, 92 Casey, Col. T. L., masonry pressure, 447 Casselman River, flood and area, 593 Cast-iron specifications, 563 gates, lateral illustrated, 269 Castlewood Dam, section, 438 Cataract Dam, data, 600 Catawba River, flood and area, 592, 593 Catskill Creek, flood and area, 594 Cattaraugus Creek, flood and area, 593 Cavour Canal, Italy, views, 298 Cedar River, flood and area, 594 flow of, 44 Cement drains, use of, 198-200 gun work, Arrowrock Dam, 452 lining canals, coefficient. 235 Cement, specification clause, 536, 537, 559, 565, 566 Centrifugal pumps, 86-90 Certified check, specification clause, 547 Chagres River, flood and area, 593 Chamberlain, T. C. report on wells, 63 Chandler, A. E., book by, 501 Changes, specification clause, 550, 551 Chapter House, Elgin, pressure on, 447 Charges for water, basis, 514, 515 U. S. R. S. table, 146 Chartrain Dam, data, 600 Chattahoochee River, flood and area, 592, 593 Chaustiere Dam, data, 600 Cheat River, flood and area, 593 Check and farm turnout, illustrated, 264 Check system of irrigation, Salt River, illustrated, 122 Checks, drops and chutes, 282-290 used in irrigation, illustrated, 116 Chemical properties, metal, 578 Chemung River, flood and area, 592 Cherry Creek, Colo., water supply, 59 Cherryvale Creek, Kansas, flood, 595 Chezy formula, 163 China, mention of irrigation in, 2, 4 rainfall at Hongkong, 356 Chinamen, market gardening of, 58 Church, Irving P., book on fluids, 182 Chute or inclined drop, 212 Chutes, checks and drops, 282-290 Chuviscar Dam, Mexico, data, 600 "Cienegas," term for swamps, 194 Cippoletti weir, book on, 182 definition of, 166, 167 formula for, 167 Clarion River, flood and area, 593 Clarke, Sir Andrew, masonry data, 447 Classification, masonry dams, 443 Clay in hydraulic fill dams, 428 Clay, used in earth dams, 423 Cleaning canals of silt, 520, 521 Cleaning up, specification clause, 553 Clear Lake Reservoir, data, 598 Clearing of irrigable lands, 104 Clentangy River, flood and area, 593 Climatic conditions, specifications, 552 Climatology of U. S., book on, 63 Closed drains, definition of, 191 Coast Range and rainfall, 28 Coefficient of roughness, 602, 603 Coefficients of friction, table, 448 Coffer dam, Arrowrock Dam, 402 specification clause, 544 Coghlan, silt data, 371 Cohoes Iron Weir, section, 486, 489 Cold Spring Earn, building, illustrated, 427 INDEX 623 Cold Springs Dam, flood at, 355 Reservoir data, 598 Colorado River, bulletin on, 63 flow of, 42 headgates, 251, 253, 256 value of silt of, 25 Columbia River flow of, 43 maximum flow of, 592 Compressed air used in pumping, 92 Compression, on masonry, 447 Concentrated crest spillway, illustrated, 274 Conconully Dam, flumes used, illus- trated, 431 outlet works, 359, 360 section of, 435 Reservoir, water records, 40 tunnel data, 334 Concrete, canal lining, 237-245 gravel, pressure on, 447 pipe specifications, 574-576 specifications, 540-543* 559~56i turnout, lateral, illustrated, 270 Cone, V. M., bulletin by, 183 flume invented by, 179 "Constant angle" dams, 472, 473 Dam, book on, 495 Construction, earth dams, 424-426 Continuous stave pipe, 324 Contract specifications, text of, 547-554 Contracted orifice, definition of, 169 Contraction joints, concrete lining, 237 in dams, 453 Contractor, specification clause, 548 Contractor's bond, specification clause, 548 Coolgardie Dam, data, 600 Cooperation with water users, 504 Coosawattee River, flood and area, 593 Corbett Dam, cross section, 248, 249 - Tunnel, data, 334 Core wall, concrete, Kachess Dam, 414 concrete, Minidoka Dam, 436 earth, Bumping Lake, 433 gravel in dam, 423 puddle, Conconully Dam, 435 steel, Otay Dam, 438 Core walls, earth dams, discussed, 422 Corrugation system of irrigation, 119, 120 Cost, clearing lands, 104-106 drainage ditches, article on, 201 drains, U. S. R. S., 200, 201 earth dams, table, 599 estimates of, projects, 531-533 leveling land, 1 10 lined canals, U. S. R. S., 242, 243 masonry dams, table, 600, 601 puddling, canal lining, 243 pumped irrigation water, 511 Reservoirs of U. S. R. S., 598 silting porous canals, 244, 245 tunnels, built by U. S. R. S., 334 water, Reclamation Service projects, 146 well drilling, 57 Cosumnes River, flood and area, 593 Cottonwood Creek, flood and area, 594 Coulon River, France, flood and area, 595 Court decision, Salt River, 149 Covell Creek Dam, Australia, data, 601 Cowgill's diagram of flood irrigation, 117 Creager, W. P., book by, 495 Creager's compressive tests, 446 Crib dams, illustrated, 401, 402 Crib work, underground, 59, 60 Cronholm, F. N., article by, 201 Crops and duty of water, 139-142 Crossings, drainage, 293-299 , highway, 335-337 Cross River Dam, data, 600 Cross-section and subgrade, 210-212 Croton Dam, cross-section, 464 , N. Y., data, 601 , Old, section, 479 Croton Falls Dam, data, 600 Croton watershed, paper on, 380 Crowley Creek Dam, data, 600 Cuba, rainfall records, 3^7 Cubic foot per second, definition, 165 Cultivation and duty of water, 140, 141 Cultivation under irrigation, 515, 516 Culverts, irrigation canals, 314-323 Current meter measurements, 171. 172 Current meters, description of, 155-163 624 INDEX Current wheel on Salmon River, 89 "Cusec" definition of, 165 Cuyamaca Dam, data, 599 Cylinder drop, Franklin Canal, 289 D D'Arcy pipe formula, 326 Dalles, flow Columbia at, 592 Dabrowka Creek, Austria, flood, 596 Damages, specification clause, 552 Dams, canvas and steel, for irrigation, 113 chapters on, 381-495 list of books on, 495 submerged, 61 tables, height, cost, etc., 599-601 underground water, 61 Darton, N. H., report on deep borings, 63 , underground water, 47 Davis, A. P., books by, 98, 201, 380 Dean and Follansbee, bulletin by, 63 Deer Flat Embankment, cross section, 416 Deer Flat Embankment, gravel face, illustrated, 418 Deerfield River flood and area, 593 Deerflat Reservoir, area, cost, etc. ; 598 leakage, 347~349 Defective work, specifications, 553 Dehree Weir, India, illustrated, 391 Del Rio, Texas, pumping plant, 95-97 Delaware River, flow and area, 592 Delays, specification clauses, 549, 550 Derwent Dam, Eng., data, 600 Deschutes River, book on, 63 flow of, 43 outlet, Tumalo, 347 Desert Land Act, mention of, 3, 497 Design, Masonry Dams, 455, 475 Dethridge meter for measuring water, 175-176 Devil's Creek, flood and area, 594 Devil's River, flow of, 44 DeVries, analysis of soils by, 9, 10 Dew Point, definition of, 27 Diamond drilling dam foundations, 494 Direct explosion pumps, 95-97 Discharge measurements of streams, 154-157 Discharge records of streams, 42-44 Ditch riders, duties of, 503 Ditcher, "V" illustration of, 107 Ditching, irrigable lands, no Ditching machine, view of, 228 Diversion dams or weirs, 382-404 , overfall, 475-490 Dixville Dam, data, 599 Domodossola Dam, Italy, data, 599 Drag line excavator, view of, 192 Drainage area, effect of, 40 of rivers, 592-596 Drainage, books on, list, 201 , chapter on, 184-201 crossings, 293-299 , irrigation and health, 5, 6 systems, design of, 193-198 Drains, classification of, 191-193 Drake, E. F., report by, 183 Drilling dam foundations, 493-495 Drilling wells, methods, 53-57 Drop and turnout, canal, 268 , canal, pump at, 90 Drops, checks and chutes, 282-290 "Dry lakes," formation of, 345 DuBois, A. Jay, book translated by, 183 Durance River, France, flood, 595 Valley, value silt in, 25 Duryea, Edwin, paper on evaporation, 7i Duty of sewage water for irrigation, 130 water, books on, list, 15, 152 , chapter on, 137-152 Dyer, C. W. D., paper on weirs, 182 Eads Bridge, pressure on piers, 447 Earth, evaporation from, 69, 70 Earthen dams, discussion of, 405 Earthquakes, rock-fill dams and, 441 Earthwork, specification clauses, 556- 559 East Carson River, flow of, 43 East Park Dam, data, 600 spillway, 482, 485, 486 Diversion Dam, view, 482 INDEX 625 East Park Reservoir, area, cost, etc., 598 Economy of water, 504-511 Eder River, Germany, flood, 595 Edinburg, sewage irrigation at, 126 Egin Bench subirrigation, 133 Egypt, abandoned irrigation lands in, 185 area irrigated in, 4 book on irrigation in, 71 records of irrigation in, 2 reference to irrigation works, v steel lined canals in, 241, 242 Einsidedel Dam, data, 600 Electric power, specification clause. 537 Elephant Butte Dam, data, 600 , cross section, 454 construction, 455, 462 design against uplift, 453 pressure, 447 Reservoir, table data, 598 silt in discussed, 377-380 Elkhorn Cr., flood and area, 594 Elliott, C. G., Bulletin by, 201 Elevating grader, view of, 228 Embankments, rules for, 405. See also Deer Flat. Engineer, specification clause, 543 Engines for pumping, 84-86 Ensign, balanced valve, 360, 365 Eolian soils, definition of, 7 type of land, 219 Erosion and canal design, 214 prevention of, in canals, 519, 520 protection against, 290-295 Escondido Dam, data, 599 Esopus Cr., flood and area, 594 Estacado Dam, paper on grouting, 495 pressure on, 447 Estanzuela River, Mexico, flood, 595 Estimates and reports, specifications, 536 of cost of project, 531-533 Etcheverry, B. A. books by, 15, 26, 98, 136, 246 , lined canal experiments by, 242 , silt data by, 373 Eucalyptus globulus, effect of, 6 Evaporating pan, illustration of, 67 Evaporation and rainfall, 41 , books on, list of, 71 , chapter on, 65-72 table, cities of U. S., 69 , table on, by months, 72 Evaporometer, observations, 68 Excavating machinery, views of, 192 Excavation, specification clauses, 538- 540 Expansion joints, concrete lining, 237 - in dams, 453, 457-461 Experience, specification clause, 551 Explosion, pumps, direct, 95-97 Extra work, specification clause, 550 Eyach River, Germany, flood, 596 Failure, masonry dams discussed, 444, 447, 449 Famine in India, 185 Fanning, J. T., book by, 182 , pressure data, 447 discharge formula, 596 Farm laterals, construction of, no Farm turnout and check, illustration, 264 Fay Lake outlet works, illustration, 360, 361 Feather River, flood and area, 592 , flow of, 42 " Federal vs. Private irrigation," 6 Fernow, B. E., evaporation data by, 70 Fertility and soil surveys, 101-103 Fertilizing effect of sediments, 25 Fertilizing effects of sewage, 1 28, 1 29 Filtration, intermittent method, 126, 127 Financial obligations, specification clause, 551 Fippin and Lyon, book by, 26 , analysis of soils by, 9 Fish Cr. N. Y., flood and area, 594 Fish screens, Umatilla project, 483 Fishkill Cr., flood and area, 59^ Fitzgerald, Desmond, evaporation ex- periments, 66 Flashboard, automatic, dams, 392, 393 626 INDEX Flashboard weirs, 388-390 , Laguna gates, illustrated, 253 use of, 257 Flathead project, sink holes, 224-226 Fleming, \V. B. book on pumps, 98 Flinn, A. D., paper on weirs, 182 book by, 380 Flint River, flood and area, 593 Float, for leveling, illustrated, no Floats, stream measurement, 155 Flood discharges, table of, 592-596 flows of rivers, examples, 355-358 prevention, reference to, 380 Floods and spillways, 354-358 , books on, 63, 64 Flooding method of irrigation, in. 112 Florida, subirrigation in, 135, 136 Flow of water, books on, 182, 183 , tables, 604-610 Fluctuations of ground water, 186-189 Flume, Bear River Canal, 295 concrete, standard plans, 296 steel, Uncompahgre Valley, illus- trated, 322 tables, hydraulic data, 613 Flumes, chapter on, 299-308 metal, specifications, 576-579 Flynn, P. J., book on irrigation canals, 182 Follensbee and Dean, bulletin by, 63 Follett, W. W., article by, 380 book on silt by, 26 ' Rio Grande silt, 379-380 silt data of, 371 Folsom canal gates, illustrated, 262 and weir, illustrated, 383, 385 Dam, data, 600 Food for plants, chapter on, 22-26 Foote measuring weir, 173-175 Forbes, R. H., bulletin by, 26 Foreign countries, area irrigated, 4 Forms, concrete, specifications, 561 pipe, Boise project, illustrated, 329 Formula, arch dams, 469 canal design, 202 erosion and canal design, 214 flood discharge, 596, 597 flow in pipe, 326, 330 Formula, flow in turnout, 268, 269-271 Kutter's, 602, 603 lateral capacity, 221 loss of head siphon, 318 orifices, 1 70 seepage losses, 235 siphon spillway, 275 stream measurement, 163-170 thickness of dam, 456 velocity head, 614 weirs, 167, 168 Fort Shaw canal spillway, illustrated, 277 Fortier, Sam'l, books by, 6, 26, 136-152 bulletins by, 71, 246 on duty of water, 148 percolation of water by, 48 Foundation, earth dams, 405-409 Foundations, masonry dams, 490-493 pressures on, 447 Fox Cr. Crossing, L. Yellowstone, illus- trated, 320 France, area irrigated in, 4 , examples of silt in, 25 , flood flows in, 355 Francis formula for weirs, 167 Franklin Canal, cylinder drop, 289 Free board of canal banks, 210 French open weirs, illustrated, 394, 396 Fresno scraper, view of, 109 Friction, coefficients, table of, 448 Friez recording stream gage, 160 Frozen streams, measurements of, 162, 163 Furens Dam, France, data, 600 - River, France, flood, 596 Furrow Irrigation, bulletin on, 15 in Idaho, illustrated, 125 methods, 117-119 system irrigation, Cal., illustrated G Gaging streams, 153-157 Galvanized sheets, advantages of, 309 Ganges Canal aqueduct, 301 super passage, 311 weirs, sections, 391 INDEX 627 Ganguillet and Kutter formula, 164 Garden City windmill and reservoir, 88 Garland Canal, dimensions, 232 turnout, 268 Gas engines for pumping, 84. 85 Gas tar, waterproofing dam with, 453 Gasoline pumping engines, 85, 86 Gate, cast iron, lateral illustrated, 269 Gate House, Conconully Dam, 360 Gates, canal wood and metal, 250-254 , reservoir, illustrated, 361-369 Gatun Dam, design mentioned, 407-477 data on, 411, 412 volume of, 599 Gem Lake Dam, data, 600 Geologic structure and rainfall, 41 Geological Survey current meters, 156 stream flow records, 39 Geology, reservoir sites, 344-346 German patent roller dams, 394 Gila River report of, 380 - stream flow records, 42 Gillepe Dam, Belgium, data, 600 Glacial soils, definition of, 7 Glatzer Neisse River, Germany, flood, 595 Godivery Weir, India, section, 391 Goldbach River, Germany, flood, 596 Goodwin Dam, Cal., data, 600 Goodyear Cr., flood and area, 595 Gorzente Dam, data, 600 Goss, Arthur, soil book by, 26 Goulburn Canal gates, Australia, 254 Weir, Australia, illustrated, 397 Grade of lands for irrigation, 100 Grader, elevating, view of, 228 Grand River, flow of, 42 Dam, illustrated, 396-400 Grand Valley canals lining, 243, 244 lands subsidence, 225 tunnels, data, 334 Grande Ronde River, flow of, 44 Granite ashlar, pressure on, 447 Granite Reef Dam, plan and section, 476 in flood, 481 Granite Springs Dam, data, 600 Grant-Mitchell meter, 177 Gravel core, view Sherburne Dam, 434 Gravel protection, Deer Flat Reservoir, 4i5-4i7 Grease wood, presence of, 102, 104 Great Forks, analysis soils at, 9 Great Salt Lake, origin irrigation, 2 Greaves, Chas., evaporation experi- ments, 66 Green, J. S., report by, 182 Green River, flow of, 44 hydrography, 35 water wheels on, 80 Gregory, W. B., book on pumps, 98 pump data, 87 Grinnell well in Paris, 50 Ground water fluctuation, 186-189 required depth to, 195 supply for pumping, 74 Grouting dam foundations, 492, 493 foundations, sp cifications, 542, 543 Grover, N. C. & J. C. Hoyt, book by Messrs., 63, 182 Gunnison tunnel, data, 334, 335 "Gunnite" on face /Yrrowrock Dam, 452 Gurley recording stream gage, 160 Gypsum and alkali, 14, 15 formation, reservoirs in, 345, 349, 350 leakage of canals in, 227 H Habra Dam, Algiers, data, 600 Haehl, H. L., evaporation report, 71 Hale's Bar Dam, data, 600 Hall, W. H., book on irrigation in Cali- fornia, 63 Hamlin, Homer, book on Salinas Valley, 64 underflow tests, 63 Hamlin's chart of California rainfall, 33 Hanna, F. W., article by, 246 hand book by, 183 recording meter, 1 73 Happy canyon steel flume, illustrated, 322 Harding, S. T. O. and M., book by, 527 Harrison, C. L., paper by, 495 Hart, R. A., bulletin by, 201 Haskell current meter, 155, 156 Hatfield Dam, data, 600 628 INDEX Hauser Dam, New, Mon., data, 601 Hawaii, area irrigated in, 4 Hawaiian Islands, article on, 98 pumping plant, 86 Hay, Prof. Robt., well reports, 63 Hazen, Allen, formula, 46, 47 Head, loss of, formula, 318 Head gates, canal 248-262 Headworks, canal, 247-262 Health and irrigation discussed, 5, 6 sewage irrigation, 129, 130 Height of Dams, table of, 599-601 Hellreigel's data on plant water, 23 Hemet Dam, valve plug, illustrated, 362 Hemlock Dam, data, 600 Henne Dam, Germany, data, 600 Henny, D. C., article by, 6 flume invented by, 1 78 Henry, A. J., book by, 63 precipitation charts by, 36, 37 Henshaw, Lewis, bulletin by, 63 Herndon, Cal., stream flow at, 33 Highway crossings, 335-337 Hilgard, E. W., book by, 15 bulletin by, 26 soil experiments by, 14, 15, 21 Hill, Louis C., meter invented by, 176 Hill, Prof. Robt. T., book by, 63 meter for measuring water, 176 Himalaya Mts., rainfall in, 357 Hindia Barrage, data, 600 History of irrigation, 2-4 Hiwassee River, flood and area, 593 Hollister, G. B., bulletin by, 183 Hollow concrete dams, 478-487 Holyoke Dam, section of, 475 Hondo Reservoir, leakage, 350 Hoosic River, flood and area, 593 Horse-power equivalents, 616, 617 Horseshoe Bend Dam, data, 599 section, hydraulic tables, 612 Horton, R. E., weir tables, 182 Hot air pumping engines, 85, 86 Hotzenplotz River, Germany, flood, 595 Howden Dam, England, data, 600 Hoyt, J. C., article by, on rainfall, 63 and Grover, N. C., book by, 63, 182 Hoyt, J. C., bulletin by, 183 Huacal Dam, Mexico, data, 600 Hudson River, flow and area, 592, 93 Hughes, D. E., report by, 380 silt data, 371, 373 "Human side of irrigation," 6 Humboidt River, flow of, 43 Hume-Bennett Dam, data, 600 Humphrey, direct-explosion pump, 95- 97 Humphrey, H. A., article by, 98 Humus, lack of, 8 Huntley, duty of water at, 147 pumping plant, 90 Hydrant, Azusa, meter, 173 Hydraulic data tables, 611-617 books on, 64, 182, 183 equivalents, table, 616, 617 fill dams, 426-436 formulae, 163-170 jump, Granite-reef Dam, 481 radius in canals, 205 radius tables, 604-613 ram, data, 91, 92 rams, Yakima Valley, 88, 92 Hydro-electric pumping, 92, 95 Hydrographers, duties of, 503, 504 Hydrographic manual, 183 Hydrographs of rivers, 33-35 Hydrology, books on, 63, 495 Hydrometric surveys, reports on, 183 Hydrostatic uplift on dams, 451-453 Hygroscopic water, in soils, 16, 17 I Ice, measuring streams through, 163 pressure in dam design, paper on, 495 pressures on dams, 450, 451 snow and, evaporation of, 68 Imperial Valley silt conditions, 222 India, area irrigated in, 4 book on irrigation in, 6, 71 famine and malaria in, 185 notch drop in, 284 rainfall records of, 356 reference to irrigation works of, v unit of flow, "cusec," 165 INDEX 629 India, wells, irrigation from, 58. See Ganges Canal. Indian Government's investigations, 5 type weirs, illustrated, 390, 391 River Dam, N. Y., data, 600 Ingot iron, effect of alkali on, 309 Injurious salts or alkali, 8-15 Inspection gallery specifications, 54-56 , specification clause, 551 Integration method of stream measure- ment, 7.58 "Intermittent filtration" methods, 126, 127 Internal combustion engines, 84, 85 Interstate Canal flume, 303, 308, 310 gates, illustrated, 251 headworks, 259 lateral gates, 269 lining, view, 239 sections, 204 siphons, illustrated, 317, 318 Investigation of a project, 528-533 lola, Kans., stream flow at, 34 Irawaddy River, India, flood, 596 Iron pipes, subirrigation by, 136 Iron weir, Cohoes, section, 486, 489 Irrigable lands, chapter on, 99-110 Irrigation, books on. See end each chapter. definition of, i " Institutions," book, 501 methods of, 111-136 rotation methods, 512-514 rules, Utah, 150-152 Italians, market gardening by, 58 Italy, area irrigated in, 4 J Jackson, L. D'A., book by, 64 Jackson Lake Dam, view of, 260 Reservoir, area, cost, etc., 598 Jaffa, M. E., soil experiments of, 13 Jamaica rainfall records, 356 James, George Wharton, book by, 6 James River Valley Wells, 51 Japan, area irrigated in, 4 rainfall records, 356 Java, area irrigated in, 4 Jerome Reservoir, leakage, 351 John Day River, flow of, 44 Johnson grass and sheep, 525 Johnston, C. T., book by, 501 Jorgenson, L. R., book by, 495 on arch dams, 469 Jorgenson's arch design, 484 Jump, hydraulic, Granite-reef Dam, 481 Jumper, clearing lands of, 105 K Kachess Dam, cross section and data, 414, 420 Reservoir, data, 598 Keechelus Dam outlet, illustrated, 366 Reservoir data, 598 Kennebec River, flood and area, 592 Keno Canal spillway, illustiated, 274 Kensico Dam, N. Y., data, 600 pressure, 447 Keokuk Dam, Iowa, data, 600 Kern River, flow of, 42 diversion weir, illustrated, 388, 389 Khojok.Pass, tunnel for water, 59 Khrishna River, India, flood, 596 Kinder River Dam, data, 599 King, F. H., book by, 15, 201 King's data on plant water, 23 River, flood and area, 593 , flow of, 42 Kingman, Ariz., dam at, 403, 404 Kiskiminetas River, flood and area, 593 Klamath project, Lost River Dam, 252 project spillway, illustrated, 274 tunnel data, 334 Kneale and Tannatt, bulletin, 201 Kuichling, Emil, paper by, 63 formula discharge, 596 Prof., flood records, 358 Kutter's formula, 164 for pipe, 326 tables, 602-610 La Boquilla Dam, Mexico, data, 601 La Grange Dam, Cal., data, 601 section, 480 630 INDEX La Jalpa Dam, Mexico, data, 601 La Mesa Dam, data, 599 Labrador, evaporation in, 65 Lagastrello Dam, Italy, data, 599 Laguna Dam headgates, illustrated, 251, 253, 256 plan and section, 386, 387 Lahontan Dam outlet, illustrated, 363 plan of, 408 Reservoir, data table, 598 Lake Bonneville, settlement of canal at, 227 Lake Cheesman Dam, data, 601 Lake Conchos, evaporation on, 71 Lake Fife Dam, India, data, 601 Lake McMillan, leakage, 349, 350 Lakes as reservoir sites, 342, 343 Lands, irrigable, chapter on, 99-110 Landslides on canals, 526, 527 values, effect on irrigation, 3 Laramie River, flow of, 44 Dam, data, 599 Reservoir, flood and area, 594 Larue, E. C., bulletin by, 63 Las Vegas Dam, data, 599 Lateral canal systems, 217-224 Laterals, canals and, chapter on, 202-246 , farm, construction of, no Lauchensee Dam, data, 601 Lava, reservoir site in, 345, 351 Law of water, chapter on, 496-501 Lawes and Gilbert's data on water, 23 Lawson, silt data, 371 Leaching of soils, 12-13 Leakage, canal, discussed, 224-227 reservoir, discussed, 346-354 Leasburg Canal gates, illustrated, 250 , sand box, illustrated, 339 diversion weir, section, 478 Leffel turbine, water-wheel, 83 Leipsic, deep well near, 51 Length of season and duty of water, 138 Leveling irrigable lands, 107-110 of land, necessity for, 103 Lewis, John H., book by, 501 Lick Observatory Records of rainfall, 356 Lined canal, Okanogan, illustrated, 321 Lined canal section, 211, 213 Lining canals, 236-241 steel, canal, Egypt, 241, 242 Lippincott, J. B., book by, 380 Lister Dam, Germany, data, 601 Lithgow Dam, pressure, 447 Little Bear Valley. See Bear Valley, 601 Little Tennessee River, flood and area, 593 Local conditions, specification clause, 55i Lock-bar pipe described, 326 Log hoist, specification clause, 546 Loire River, flood of, 355 Los Angeles, sewage irrigation, 130 Losses, canal and prevention, 233, 234 early irrigation, 3 seepage/ 234-236 Lost River and Tule Lake, 352 diversion works, illustrated, 252 Loughridge, R. H., book by, 15, 26 investigations of, n, 12, 20 Louisiana, rice irrigation in, 86, 97, 98 Low-head pumping plants, 86 Lower Otay Dam. See Otay. Lower Yellowstone Canal drop, 287 sluiceway, 278 culverts, illustrated, 315, 316 Dam, section, 387 pipe inlet, 294 sand gate, 340 siphon, illustrated, 320 Lyon, analysis of soils by, 8 Lyon and Fippin, book by, 15, 26 experiments on soil, 18 M McAdie, A. G., book on rainfall, 64 McAlester Dam, data, 599 McCall's Ferry Dam, section, 480 McCausland, bulletin by, 63 McCloud River, flood and area, 593 McDowell, Ariz., stream flow at, 35 MacMillan Dam, data, 599 Lake, data, 598 Reservoir, leakage, 349. 350 Mahan, F. A., book on water wheels, 98 INDEX 631 Maintenance, operation and, chapter, 502-527 work, when to do, 518, 519 Malaria, effects of irrigation, 5, 6 in India, 185 Malheur River, flow of, 43 Malleable castings, specifications, 564 Manholes, drain lines, 197, 198 Manning, Robt., book by, 64 Marklissa Dam, Germany, data, 601 Masonry Dams, chapter on, 442-495 table of data, 600, 601 Material and workmanship specifica- tions, 548-549 Mauer Dam, Germany, data, 601 Mead, D. W., book by, 63, 183 , rainfall tables, 32 , Elwood, book by, 501 bulletins by, 152, 246 Means, Thos. H., water investigations, 62 Measurement of irrigation water, 153- 183 water to the user, 164, 165 Measuring devices, 165-182 vi2w of, detail of, 263 water, books on, 182-183 Medina Dam, Texas, data, 601 Meer Allum Dam, plans of, 472 Merced Dam, Cal., data, 599 River, flood and area, 593 Mercedes Dam, Mexico, data, 601 Mesquite, clearing land of, 104 Metal flumes, specifications, 576-579 work, specification clauses, 545, 546 Meters for measuring water, 155-163 water works not suitable, 172 Meyer, A. F., book by, 495 voids in rock, 491 Miami Valley floods, work of, 354, 355 Mill Brook, N. Y., flood and area, 595 Creek, Pa., flood and area, 594 Mineral food for plants, 23, 24 "Miner's inch," and duty of water, 149 definition of, 165 value of, 616 Minidoka Canal gate, 250 Dam, section of, 436 Minidoka project, lateral system, 218, 219 silting canals, 244, 245 pumping plant, 93-95 Reservoir, area, cost, etc., 598 Minitare Darn outlet, illustrated, 362, 366 Reservoir, table data, 598 Missouri River, flow of, 43 "Modoc Lava Beds," leakage, 352 Moehne Dam, Germany, data, 601 Mohawk River, flood and area, 592 Moisture in soil, 16-21 Monocacy River flood and area, 593 Monongahela River, flow and area, 592 Montrose and Delta Canal headgates, 260 Morena Dam, data, 599 Morin's coefficients of friction, 448 Moritz, E. A., articles by, 183, 246 Morris Dam, Conn., data, 599 Morrison data on pressure, 447 Moselle River, France, flood, 595 Valley, value silt in, 25 Mosquitoes and irrigation, 5, 6 Mountain Dell Dam, Utah, data, 601 Mulching and alkali, 14 evaporation, 66 Mullins. Lieut. -Gen. J., book by, 182 Murphy, D. W., article by, 201 E. C., bulletins by, 98, 183 Murgab Valley, abandoned lands, 185 headgates in, 261 N "N" value, Kutters formula, 164, 602, 603 Nadrai Aqueduct, India, 313 Narora weir, India, illustrated, 391 Narrows Dam, uplift data, 453 Navier's formula, arches 469 Necaxa Dam, Mexico, data, 599 failure, 428, 429 Neches Canal pumping plant, 98 Needle valves, illustrated, 362, 368 Neosho River, flood and area. 592 flow of, 34, 43 632 INDEX Nettleton, E. S., book by, 64 New Croton Dam. See Croton Dam. New Dam, Mexico, data, 601 New Hauser Dam, Mon., data, 601 New River, flood and area, 592 Newell, F. H., artesian well report, 64 article by, 6 books by, 98, 152, 527 report by, 183 Newell and Murphy, book by, 98 Nicaragua, report en hydrography of, 380 of rainfall, 357 silt experiments, 374-376 Night irrigation, 511, 512 Nile, barage on, at Cairo, 387 Valley, silt irrigation in, 25 Nitrates and plant food, 23, 24 Nitrogen and plant food, 24 Norwich Water Co., Dam, section, 477 North Platte. See also Interstate Canal Whalen Dam, 257, 259 River, flow of, 44 Notch drop, India, illustrated, 284 Interstate Canal, 286 Nurse crop of alfalfa and rye, 105, 106 O O'Shaughnessy, M. M., article by, 98 Ocmulgee River flood and area, 592 Oconee River, flood and area, 594 Oder Dam, Germany, data, 601 River, Germany, flood, 595 Ohio River, flow of, 592 Oil lining, canals, coefficient, 235 Okanogan Canal, lining, illustrated, 321 project, chute, 294 irrigation methods, 513 tunnel data, 334 Okhla weir, India, illustrated, 391 Old Croton Dam. See Croton Dam. Olive Bridge Dam, N. Y., data, 601 pressure on foundation, 447 Ontario Colony, Cal., water supply, 59 Open and closed weirs, 386-388 Open drains, definition of, 191 Operation and maintenance, chapter on, 502-527 charges, U. S. R. S., 146 Optimum water supply, 18-20 Orange grove irrigation, illustrated, 122 Oregon, water supply of, book on, 63 Organization, specifications of, 535, 536 Orifices, measuring 168-172 formulae, 170 table, 1 80, 181 Orland project, lined canal, O. & M. costs, 242. See also East Park Dam. Orme, Dr. H. O., investigations of, 5 S. H., sewage irrigation book, 64 Otay Dam, core wall, 438, 440 failure of, 441 lower length, height and volume, 599 views of, 439, 440, 471 Outlet works, reservoir, 358-369 Overfall dams, illustrated, 475, 490 Overhaul, specification clause, 558 Overshot water-wheels, 81, 82 Overturning, failure of dams by, 449 Owl Creek Dam, gravel blanket, 436 material used, 423 outlet works, 359 paving, illustrated, 418 section of, 406. See also Belle Fourche. Owyhee River, flow of, 43 Pacific Slope, rainfall on, 32-34 Pacoima Creek, dam on, 403 Paris, deep well in, 50 Pas Du Riot Dam, France, data, 601 Pasadena, Cal., sewage irrigation, 130 Passaic River, flood and area, 593 Patents, specification clause, 553, 554 Pathfinder Dam, Wyo., data, 601 view of, 470 Reservoir, area, cost, etc., 598 Pecos Irrigation Co., canals, leakage, 227 INDEX 633 Pecos River, flow of, 44 , Lake McMillan, 349 Valley Dams, data, 599 Pelton water wheels, 84 Peguonnock Rivei, flood, 594 Percolation of water in dams, 417-423 in soils, 48 rate of, 46, 47 views of, 123 Periar Dam, India, data, 601 section, 463 Permeability of soils, table, 47 Persia, records of irrigation in, 2 Peru, area irrigated in, 4 Philippines, area irrigated in, 4 rainfall records, 356 Piche evaporometer observations, 68 Pilarcitos Dam, data, 599 Pile weirs described, 384, 387 Piling, specification clause, 544, 545 Pinal Creek, flood and area, 594 Pinon, clearing lands of, 105 Pipe, concrete, specifications, 574-576 formulae discussed, 326, 330 irrigation, sub-irrigation, 134, 135 manufacture, illustrated, 328, 329 steel, specifications, 572-574 turnouts, U. S. R. S., plans, 266 vitrified, specifications, 590, 591 wood stave, specifications, 567-571 Pipes, concrete, metal and wood, 323- 330 flow of water in, paper on, 183 Piscataquis River, flood, 594 Pishkun tunnels, data, 334 Plant food, chapter on, 22-26 growth and water, 22, 23 Platte River, cribwork on, 59, 60 Plowing as remedy for alkali, 13 Po Valley Canal structures, Italy, 298 Pocolet River, flood and area, 594 Pomona, Cal., irrigation at, 98 Pompton River, flood and area, 594 Poncelot water wheels, 81 Potassium and plant food, 23, 24 Potholes in canals, 224, 225 Potomac River, flow and area, 592 Powder River, flow of, 43 Powell, J. W., report on wells, 64 Precipitation charts of U. S., 36 in U. S., maps of, 29-31 Prehistoric irrigation works, 2 Preparation of land for irrigation, 104- no and duty, 140 Preparing land, bulletin on, 136 Pressures on masonry, table, 447 dams, 444-447 Price current meter, 155-157 Price River, flow of, 44 Priming canals, Grand Valley, 243, 244 "Principles of irrigation practice," book, 6 "Private vs. Federal irrigation," 6 Profits of irrigation discussed, 4, 5 Progress of work, specification clause, 536 Project manager, duties of, 502 Proposal, specification clauses, 547 Prosser siphon and bridge, illustrated, 327 Protection of earth dams, 413-417 Protection of work, specification clause, 553 Provo River, flow of, 44 Puddling, cost in lining canals, 243 specification clause, 559 Pumping, books on, 98 for irrigation, 73-98 Pumps, centrifugal, 86-90 Purchase specifications, 555-556 Putah Creek, flood and area, 593, 594 Quantities, specification clause, 552 Queis River, Germany, flood, 595, 596 R Rafter, Geo. W., book on sewage, 64 Rainfall and duty of water, 138, 139 books on, 63, 64 character of, 41 discussion of, 27-37 excessive, records, 356, 357 government projects, 145 of Cal., report on, 64 634 INDEX Rainfall records, tables, 356, 357 runoff and, 40, 41 U. S. maps of, 29-31 Ram. See Hydraulic ram, 91, 92 Ramapo River, flood and area, 594 Rands, H. A., paper by, 495 Raritan River, flood and area, 593 Rating curve for stream measurement, 162 Rawhide crossing, illustrated, 317 "Reclaiming the arid West," book, 6 Reclamation Act, passage of, 3 " Record," article on water, 152 Reclamation Service, canal linings, 238- 244 canals, table of, 230-232 drainage problem, 185 drains, table of, 200, 201 duty of water, 144, 145 O. & M. charges, table, 146 pipe formulae, 330 pumping plant, 90 reservoirs, 598 spillway standards, 272, 273 turnouts, plans, 266-270 Reconnaissance of project, 528 Recording water meters, 172-179 Redwood for pipe discussed, 324 Regulator gates, canal, 250-256 Reinforced concrete dams, 478-487 Reinforcement bars, specifications, 559, 562 Remedies for alkali, 12-15 Remscheid Dam, table of data, 60 1 Reports and estimates, specifications, 536 Reservoirs, built by U. S. R. S., table, 598 storage, chapter on, 342-369 Residual soils, definition of, 7 Return flow measurements of, 245, 246 Returns of irrigation, 4, 5 Rhine River, Switzerland, flood, 595 Rice irrigation, 97, 98 pumping for, 86 production in U. S. by States, 97 Right of way, specification clause, 553 Rio Das Lages Dam, data, 601 Rio Grande, bulletin on, 63 flow of, 42-44 silt, book on, 26 , data, 25, 371, 372 deposits, 377-379 , Panama, flood, 595 Valley, duty of water in, 147 seepage, 185 water fluctuation, 187 wells in, 58 Rio Mora, flood and area, 593, 594 Riparian doctrine of water right, 496 River discharge, books on, 63 Riverside, Cal., irrigation illustrated, 115, 122 Rivers, flood discharge table, 592-596 Road crossings, 335-337 Roads and fences, specification clause, 553 on canal banks, 210 specification clause, 537 Rockfill, specification clause, 545 dams, 436-441 table of. 599 Rock sections of canals, 207, 208 Roller dams, illustrated, 394-400 Rolling earth dams, 425, 426 view of, 427 Rondout Creek, flood and area, 594 Rookery Building. Chicago, pressure, 447 Roosevelt Dam, plan and section, 467, 468 table of, data, 601 pressure on, 447 Reservoir, area, capacity, etc., 598 Rotation system of irrigation, 182, 512- 5i4 Run-off, laws of, 40-45 Russell, T., evaporation experiments, 68 Russia, area irrigated in, 4 Russian thistle, pest 0^.524, 525 Rye as a nurse crop, 106 Ryves, Col., discharge formula, 597 St. Louis Bridge, pressure on, 447 St. Louis, deep well in, 51 INDEX 635 St. Mary Lake Dam, mixture, for, 420 St. Paul's, London, pressure on, 447 St. Peter's, Rome, pressure on, 447 Sacaton grass and alkali, 10 Sacramento River, flow and area, 592 flow studied, 42, 354 Safety conditions of dams, 381, 382 Sagebrush indication of fertility, 102, 104 Sahara Desert, waters of, 62 Salinas Valley, Cal., report on, 64 Salmon River, current wheel on, 89 Dam, data, 601 design, 472,473 Salt-bush and alkali, 13 Salt Lake, origin of irrigation at, 2 Salt River, flow and area, 592 hydrograph of, 35, 42 Project, irrigation, 513 Valley, court decision, 149 duty water in, 147 irrigation, illustrated, 122, 124 value of silt of, 25 Salton Sea, evaporation on, 72 Salts, injurious, and alkali, 8-15 San Andres Dam, data, 599 San Carlos Project report, 380 San Diego flume, Cal., 302 San Fernando submerged dam, 403 San Gabriel River, flood and area, 594 flow of, 42 San Joaquin River, flow of, 33, 42 River, flood and area, 593 Valley, windmills in, 75 San Jose Dam, Mexico, data, 601 San Luis Rey, Cal. River, flood, 593 Valley, abandoned lands, 185 sub-irrigation, 133, 134 San Marcial, Rio Grande, silt at, 372 San Mateo Dam, Cal., data, 601 plans and section, 466 San Pablo Dam, data, 599 San River, Austria, flood, 595 Sand, specifications, 560 Sand boxes, illustrated, 338-340 Sand traps, canal, 337-341 and manholes, 197 Sandstone, pressure on, 447 Sandy land in soil surveys, 103 Sandy regions, clearing of, 105-106 Sanitary works, books on, 64 Sanitation, specification clause, 553 Santa Ana Canal lining, 237, 240 sand box, 338 flume, Cal., 302, 304 River, flow of, 42 Santa Catarina River, flood, 593 Santa Ysabel Creek, flood, 594 Saturation of earth dams, 409-411, 419- 423 hydraulic fill-dams, 428 soil discussed, 19 Savannah River, flow and area, 592 Saw, submarine, weeds, 523 Sawmill, specification clause, 537 Schantz, H. L., book by, 25 Scheidenhelm, F. W., paper by, 495 Scheidenhelm's coefficient of friction, 448 Schlichter & Wolf, book by, 98 Schlichter's experiments on soils, 48 Schoharie Creek, flood and area, 593 Scioto River, flood and area, 593 Schuyler, J. D., book by. 380 gates designed by, 360-362 pressure data, 447 Scobey, F. C. ; bulletin by, 183 Scoop wheels, 90, 94, 95 Scraper, Fresno, view of, 109 slip, illustration of, 106 Screw pump, 87 "Seal," water, of tunnel, 331 Season, length, and duty of water, 138 "Second foot," definition of, 165 table of equivalents, 616 Sections of canals, illustrated, 204 Sediment rolled along bottom, 373-376 Sedimentation of Reservoirs, 370-380 tank for sewage, 131 Sediments, fertilizing effect of, 25 Seepage in dams, 417-423 formulae, 235 losses, canal, 202, 234-236 reservoir, discussed, 346-354 Rio Grande Valley, 147 signs of, 185-191 Seine, open weirs on, 387, 394 636 INDEX Seligman Dam, Ariz., data, 601 Seros Project Dams, data, 599 Settlement of lands, Grand Valley, 225 Sevier River, flow of, 44 Dam, data, 599 Sewage disposal, 123-127 farms, laying out of, 130-133 fertilizing, effect of, 128, 129 irrigation, 125, 127, 128 books on, 64 health and, 129, 130 "Sewage purification in America," 63 Sheep used in clearing canals, 525 Shenandoah River, flood and area, 592, 593 Sherburne Lake Dam material, 423 section, 434 Shifting channels and stream measure- ments, 159 Shoshone Dam, Wyo., data, 601 diagram, 474 pressure, 447 Desert before and after, 100, 101 Project, Corbett Dam, 248, 249 Reservoir data, 598 tunnel, data, 334 Shutters, automatic, illustrated, 392, 393 Siam, area irrigated in, 4 Sickness. See Health and Malaria. Side slopes of canals, 209 Sierra Nevada Mts. and rainfall, 33 Signature, specification clause, 547 Silt allowance in canal design, 203 bearing water, effect of, 25 books on, 380 conditions, Imperial Valley, 222 deposits in canals, 520, 521 removal from reservoirs, 376-380 table of weight of, 371 Silting leaky canals, 244, 245 of reservoirs, 370-380 Sink holes, leakage from, 350 in canals, 224-227 Siphon spillways, illustrated, 275-277 Siphons, large canal, 317-320 Six-mile Creek, flood and area, 594 Six-tenths of depth method of measur- ing stream flow, 158 Slichter, C. S., underground waters, 64 Slichter's percolation experiments, 419 Sliding failure of dams, 447-449 Slides of canal banks, 526, 527 Slip scraper, illustration of, 106 Slope of lands for irrigation, 100 Slopes of earth dams, 409-417 Sluiceway, Lower Yellowstone, illus- trated, 340 standard design, 278 Snake River, flow of, 43 Canyon, leakage to, 351 Dam, section of, 436 power plant on, 93-95 Snow and ice, evaporation on, 68 Snowfall, effect on stream flow, 37, 38 Soane Canal sluice gate, illustrated, 395 weir flashboards, illustrated, 392 Sodium carbonate, effects of, 1 1 sulphate and alkali, 14 Sodom Dam, N. Y., data, 601 Soil conditions and rainfall, 41 moisture, chapter on, 16-21 survey of lands, 101-103 Soils and duty of water, 139 books on, 15 chapter on, 7-15 Somerset Dam, data, 599 Sorgues River, waters for irrigation, 25 South America, area irrigated, 4 South Dakota, largest well in, 51 South Platte River, flow of, 42 seepage to, 245 Spanish irrigation systems, 2 Spaulding Dam design, mention, 473 Specifications, chapter on, 534-591 Sperenburg deep well, 51 Spiers Falls, N. Y., Dam, data, 601 Spillway, East Park Dam, 485 provisions, 354-358 Spillways, canal, illustrated, 271-282 Spiral lap seam pipe, 326 Sprague River Dam, view of, 258 Spring Canyon flume, 303, 308, 310 Spring Valley Water Co. well experi ments, 59 INDEX 637 Springs in foundation of dams, 408, 409 Sprinkling earth dams, 425, 426 Spokane River, flow of, 44 Spou, Ernest, book on wells, 64 Stanislaus River, flood and area, 593 Stanley, F. W., book on Florida, irriga- tion, 136 Starch Factory Cr., Conn., flood, 595 Stave pipe specifications, 566-571 Steam-power pumping engines, 86 Steam R.R., specification clause, 537 Steel bars, specifications, 562, 563 bridges, specifications, 579-584 castings, specifications, 564 dam used in irrigation, 113 dams, illustrated, 487-490 flumes, 303-308 lined canal, Egypt, 241, 242 mild, effect of alkali on, 309 pipe, discussed, 325, 326 specifications, 572-574 structural, specifications, 561, 562 Stevens automatic stream gage, 160 Stilling basin and drop, 291 Stony Cr., Cal., flood and area, 593 Stony River Dam, paper on, 495 Storage dams, illustrated, 404-436 reservoirs, chapter on, 342-369 - U. S. R. S., table, 598 water and evaporation, 70, 71 Stove pipe method of well drilling, 57 Strange, W. I., book on India, 380 Strawberry Dam, section of, 410 Reservoir, data, 598 tunnel, data, 334 Valley flume, illustrated, 310 lined canal, illustrated, 336 Stream flow, discussion of, 37-40 records in U. S. tables, 42-44 measurement methods, 153-157 Structures, canal, chapter on, 247 Subgrade of canals, 210-212 Sub-irrigation discussed, 133-136 Submarine saw for weeds, 523 Submerged dams, illustrated, 402-404 weir, measuring water, 166 Subsidence, Grand Valley lands, 225 Sub-surface water sources, 45-48 Sugar beets and alkali, 10 Sugar Loaf Dam, data, 599 Sulphur Creek wasteway, 293 Sunland River, flood and area, 595 Sunlight in arid regions, 2 Sunnyside Canal, dimensions, 232 Sun River tunnels, data, 334 Superpassage, Ganges Canal, illustrated, 3n Suppressed orifice, definition, 169 Survey of reservoir sites, 353, 354 stakes, specification clause, 553 Surveys of a project, 528-533 Suspension of contract, specifications, 549 Susquehanna River, flow and area, 592 Swamp reclamation and drainage, 185 Swanzy Dam, Wales, data, 601 Sweetwater Dam, Cal., data, 601 - spillway, 354, 355 Reservoir, seepage into, 246 flood and area, 594 Sweetwater valve plug, illustrated, 362 Swingle, Z. T., bulletin by, 26 Synclinal Valley as reservoir site, 345 Tait, C. E., bulletins by, 98, 136 Talbot, A. N., article by, 63 Talla Dam, Scotland, data, 599 Tannatt and Kneale, bulletin by, 201 Tansa Dam, India, data, 601 River, India, flood and area, 596 Teele, R. F., book on land, 136 report by, 152 Telephone, specification clause, 537 system specifications, 586-590 Tennessee River, flow and area, 592 Little, flow and area, 593 Tension in masonry discussed, 465 Ternay Dam, Fr., data, 601 Terraced hillside irrigation, illustrated, 120, 121 Texas, rice irrigation in, 97, 98 Theresa concrete weir, section, 486 Thompson, S. E., book by, 495 Three-mile Falls Dam, plans and sec- tion, 483 638 INDEX Throttle Dam, data, 599 Tieton Canal flume plans, 297 lined canal, 211, 213 section, illustrated, 241, 281 steel flume, 306 tunnels, data, 334 Tile drains, sizes of, 191-193 used in drainage work, 196, 197 sub-irrigation, 134, 135 Timber, specification clause, 544 dams, 382-384 Titicus Dam, N. Y., data, 601 Titles, water, 496-501 Toccoa River, flood and area, 594 Toncan metal, alkali and, 309 Topography and rainfall, 41 of irrigable lands, 99-101 Trapezoidal channels, table data, 6n Trench excavator for drainage, 192 Trenching machinery, bulletin on, 201 Triunfo Creek Dam, Cal., data, 601 Truckee Canal drop, illustrated, 283 lining, view, 240 waste way, illustrated, 279 River, flow of, 43 Tsar Canal, Turkestan, 261 Tucson, Ariz., sewage irrigation at, 128 Tugaloo River, flood and area, 593 Tule Lake, leakage from, 352 Tumalo Reservoir, leakage, 346, 347 Tumble weeds in canals, 194 Tunneling for water, 59-61 Tunnels, discussion of, 330-335 specification clause, 538 specifications, 584-586 table length and cost, 334 Tuolumne River, flow of, 42 flood and area, 593 Turbine water wheels, 82, 83 Turkestan, abandoned lands in, 185 gates and headgates in, 261 Turlock Canal, cross-section, 207 Turnouts, lateral canal, 263-271 Turtle Creek, flood and area, 594 Twin Falls canals and leakage, 227 reservoir leakage, 351 Tygart River, flood and area, 593 Typhoid fever and sewage irrigation, 1 29 U Ubaya River, France, flood and area, 595 Umatilla by-pass drop, 288 Canal lining, view, 239, 243 section, 208 Project, duty of water on, 147 River, flow of, 43 Uncompahgre tunnels, data, 334 Valley drops, 290 duty of water in, 147 flume, illustrated, 322 Underflow tests, bulletin on, 63 Underground irrigation, 135, 136 waters, 45-48 books on, 63, 98 Undershot water wheels, illustrated, 78- 81, 89 Unit prices, specification clause, 552 United States, area irrigated in, 4 Uplift, hydrostatic on dams, 451-453 Upper Deer Flat Embankment section, 416 Urft Dam, Germany, data, 601 Urnasch River, Switzerland, flood, 596 Use of water, doctrine of, 496, 499 Use of Water in Irrigation," book, 6 Utah experiments on duty of water, 141- 143 rules for irrigation, 150-152 V "V" ditcher, illustration of, 107 Valve plugs, cast iron, dams, 362 Valves, butterfly and needle. 362-369 Van Buren's stability of dams, 451 Vapor engines for pumping, 84, 85 Vegetation and rainfall, 41. 42 in canals, clearing. 521-524 Velocity head tables, 614 in canals, discussion of, 215-217 of approach to weirs, 168 tables, flow of water, 602-610 Ventilation of tunnels, 333 Venturi flume, 178, 179 water meter, 177, 178 formula, 1 78 INDEX 639 Verdun River, France, flood, 595 Victor turbine water wheel, 83 Villar Dam, Spain, data, 601 Vistula River, Galicia, flood, 595 Vitrified pipe, specifications, 590, 591 Vogesen Mts., rainfall in, 32 Voids in stone, 491, 492 Volume of Dams, table of, 599-601 Vyrnwy Dam, Wales, data, 601 pressure on foundation, 447 W Waco, Tex., artesian area, 51 Wachu setts Dam, data, 60 1 Reservoir, permeability, 47 Waldeck Dam, Ger., data, 601 Walnut Canyon Reservoir leakage, 350, 35i Walnut Grove Dam, failure of, 441 Wanague River, flood and area, 594 War Department report, San Carlos, 380 "Wash borings," dam foundations, 494 Washington Monument, pressure on, 447 Waste water, discussed, 511,512 Waste ways, discussion of, 277, 278 Water and plant growth, 22, 23 application of, to land, 111-136 character of, 61-63 concrete specification clause, 560 consumed by crops, table, 23 economy discussed, 504-5 1 1 . See Duty of Water. Law, books on, 501 logged lands, 184, 185 San Louis Valley, 133, 134 measurement, chapter on, 153-183 proofing dams, by gunnite, 453 rights, claapter on, 496-501 supply and plant life, 18-20 chapter on, 27-64 investigation of, 528-529 table, effect of rise of, 10, n rise of, 184, 185 users, cooperation with, 504 waste discussed, 511, 512 wheels, pumping, books on, 98 pumping with, 78-84 Water works meters not suitable, 172 Wave action on gravel slope, 417 Weather Bureau, evaporation table, 72 Weber River, flow of, 44 Weeds, clearing canals of, 521-524 Weep holes, concrete canal lining, 237 Wegmann, Edward, book by, 495 Weight, various substances, table, 615 Weights and measures equivalents, 616, 617 Weir formulae, 167, 168 Weirs and coefficients, books on, 182, 183 measuring water by, 166-168 or diversion dams, 382-404 various kinds described, 384-391 Weisbach, P. J., book by, 183 pipe formula discussed, 326 Weiser River, flow of, 43 Wells, artesian, 48-59 books on, 63, 64 deep, examples of, 50, 51 in dams, drainage, 454 ' in drainage ditches, 194 irrigation from in India, 58 Werre River, Germany, flood and area, 595 West Gallatin River, flow of, 43 Whalen Dam, views of, 257-259 Wheel scraper, view of, 425 Wheels^ water, for pumping, 78-84 Whippany River, flood and area, 594 White Nile, irrigation water of, 25 Widtsoe, John A., book of, 6, 25, 26, 152 bulletin on evaporation, 71 O. & M. conclusions, 511 plant water, data on, 23 Wigwam Dam, Conn., data, 601 Willamette River, flow of, 43 Willcocks, Sir William's visit, V Williams Dam, Ariz.", data, 601 Willow Cr., Ore., flood and area, 594 Wilson, H. M., books of, 6, 26, 152 bulletin by. 98 first edition by, V Wilting coefficient, definition of, 20 Wind and evaporation, 68 erosion of canal banks. 524, 525 640 INDEX Windmills, books on, 98 capacity table, 77, 79 for irrigation, 75-78 Wind pressures, tables of, 76, 77 Winter operation of canals, 516-518 Wire reinforcement, pipe, illustrated, 328 wound wooden pipe, 324 Wofelsbrund Dam, Ger., data, 601 Wolff, A. R., book on windmill, 77 Wollny, data by, on plant water, 23 Wood stave pipe siphon, illustrated, 312 specifications, 566-571 Wooden drains, use of, 198 Workmen, specification clause, 552 Workmanship, specification clause, 548, 549 Wupper River, Germany, flood, 595 Yadkin Narrows Dam, data, 601 River, narrows dam at, 453 Yakima County, water appropriation, 498 River, flow of, 44 tunnels, data, 334 Valley, analysis soils of, 9 furrow, irrigation, 118 hydraulic rams, 92 siphon, illustrated, 327 Yarnell, D. L., bulletin by, 201 Yellowstone Dam, lower, 387 River, flow of, 43 Youghiogheny River, flood and area, 593 Yuba River, flood and area, 593, 594 Yuma, Ariz., furrow irrigation, illus- trated, 119 Canal headgates, illustrated, 251, 253, 256] siphon spillway, 276 Zola Dam, Spain, data, 601 Zuni Dam failure, 352 $*?. UNIVERSITY OF CALIFORNIA LIBRARY