REESE LIBRARY OF THE UNIVERSITY OF CALIFORNIA. I ! Class i i I r-w-T--iJ-Tl-iJ-T.-v-ir-if-tr-MrTi-u--ii-u-T^-u-ii-- PKACTICAL IRRIGATION ITS VALUE AND COST WITH TABLES OF COMPARATIVE COST, RELATIVE SOIL PRODUCTION, RESERVOIR DIMENSIONS AND CAPACITIES, AND OTHER DATA OF VALUE TO THE PRAC- TICAL FARMER BY AUG. J. BOWIE, JR. A. B., HARVARD ; S. B. MECHANICAL ENGINEERING, MASS. INST. OF TECHNOLOGY ; S. B. ELECTRICAL ENGINEERING, MASS. INST. OF TECHNOLOGY NEW YORK McGRAW PUBLISHING COMPANY 1908 *>& QHTED, 190* COPYRI BY THE McGKAW PUBLISHING COMPANY, NEW YORK Stanhope Jpress F. H. GILSON COMPANY BOSTON. U.S.A. PREFACE THE prospect of converting desert land into a flourishing coun- try lends to irrigation an attractive aspect. Some people, carried away with the possibilities of irrigation, lose sight of the all-impor- tant financial end of the question, and make extensive investment in apparatus which is unnecessary or unsuited to the work to be done. Others, from ill-advised ideas of economy, endeavor to irri- gate their land without properly laying out their plant, and spend for labor alone many times the cost of a suitable installation. To speak intelligently about irrigation, we must know the cost and the value, not only of the plant as a whole, but of the individual parts thereof. These are subjects of primary importance. The actual cash outlay necessary for operation is often considered as the cost of irrigation, without making any allowance for interest or depreciation on the investment in the irrigation plant. Thus we find the popular conception that water obtained from an artesian well is supplied at no expense, while pumped water, owing to the expense of a pumping plant, is by no means so desirable. The first cost of the well is entirely lost sight of. Although it is highly desirable to avoid the expense for fuel or attendance, still the fixed charges on a deep artesian well, when the flow is small, may easily make artesian water more expensive than water pumped under low lift. Where the cost of obtaining water is high, expensive means of preventing seepage may be justified. Where fuel is high, and the plant is operating under a high lift, an efficient high-grade plant should be installed. Where fuel is cheap, and cheap low-grade labor is available, it may be folly to install a high-grade plant with its added expense and complication. How shall we know how far to go and what kind of apparatus to install ? Obviously we can give no intelligent answer unless we know the cost and mini' of the plant as a whole, as well as of its individual parts. It is the endeavor of the writer to furnish data for determining 171.148 iv PREFACE. the cost and value of irrigation, and of the apparatus and machin- ery which may be used therein. In a country rich in natural resources, little attention is usually given to the economic utilization of its wealth. It is difficult for ideas of economy to receive serious consideration, and reckless waste is likely to exist until the development reaches such a stage that the scarcity of material makes itself keenly felt. This is particularly true in the case of the use of water for irrigation. In arid America the available water supply is sufficient for the irriga- tion of only a very small percentage of the land susceptible of irri- gation. Without storage, much of this water will run to waste. Economic considerations require the ultimate construction of large reservoir systems for the storage of this water. Present development is governed by the present cost; but future development will be governed by the value of the water in increased production, rather than by the present cost of obtaining it. The problem of the economic use of water is becoming of con- stantly increasing importance. In many places the entire supply available is consumed by present methods of irrigation. Although apparently the irrigation limit has been reached, the storage of water, the prevention of seepage losses, and the use of proper scientific methods of applying the water so as to prevent to a large extent losses by evaporation will usually increase greatly the area which may be irrigated. For instance, the losses of water by evap- oration from the soil which may be avoided by proper irrigation are often astonishingly great. This is well brought out by the important investigations conducted by Professor Fortier, Chief of Irrigation Investigations of the United States Department of Agriculture. . The subject of earth reservoirs has been treated at some length as it is felt that they have a large field of usefulness. The figures given for large reservoirs are intended rather to indicate the con- siderations which should be used in their design, and also to sug- gest their practicability or impracticability, as the case may be, than to be of use in individual cases where the topography of the ground must always be considered. Part of the data presented in this book is the result of investi- gations by the author while acting as expert for the U. S. Depart- ment of Agriculture, and is summarized from the following bulletins published by the Office of Experiment Stations : " Irrigation in PREFACE. v Southern Texas," published as separate No. 6 of Bulletin No. 158, and " Irrigation in the North Atlantic States," published as Bulle- tin No. 167. The author is indebted to Mr. A. M. Hunt and to Mr. Frank Adams for many valuable suggestions in connection with the prep- aration of this book. AUG. J. BOWIE, JR. SAN FKANCISCO, Jan. 2, 1908. CONTENTS CHAPTER PAGE I. WHAT IRRIGATION HAS ACCOMPLISHED 1 II. UNITS IN USE 11 III. METHODS OF IRRIGATION IN USE 20 IV. EVAPORATION 23 V. ACTUAL RESULTS OF IRRIGATION 34 ^ VI. DIFFERENT SOURCES OF WATER SUPPLY 42 The Natural Flow of Streams Reservoirs Natural Reser- voirs Cost of Stored Water Value of Location Artificial Reservoirs Canals as Storage Basins Underground Supply. VII. METHODS AND APPLIANCES FOR OBTAINING WATER 55 Conduction and Distribution of Water Calculation of the Flow of Water in Ditches Measurement of Flow of Water Natu- ral Reservoirs Wells. VIII. WELLS 85 Law of Flow of Wells Methods and Cost of Boring Wells. IX. PUMPS AND PUMPING MACHINERY 103 X. IRRIGATION NEAR BAKERSFIELD 128 ^ XI. METHODS OF CHARGING FOR WATER IRRIGATION . 141 XII. ECONOMIC LIMIT OF IRRIGATION 147 - XIII. EARTH TANKS 153 XIV. LARGE ARTIFICIAL RESERVOIRS 166 vii viii CONTENTS CHAPTKK PAGE XV. LARGE RESERVOIRS FOR THE STORAGE OF ARTESIAN WATER 187 XVI. ECONOMIC USES OF RESERVOIRS AND TANKS .... 199 APPENDIX A 203 APPENDIX CIRCULAR EMBANKMENTS 219 Economic Design of Large Reservoirs on Level Ground on Sloping Ground on Sloping Ground, for Fixed Belt of Rip- rap-lined Reservoirs Constructed on Sloping Ground, with Fixed "Width of Riprap of Large Lined Reservoirs of a Given Capacity of Reservoirs on Level Ground for the Stor- age of Artesian "Well Water Cox's Formula. INDEX 229 PRACTICAL IRRIGATION. CHAPTER I. WHAT IRRIGATION HAS ACCOMPLISHED. OF all the varied industries and means of producing wealth, there is none which ever has or probably ever will compare in importance with agriculture. The value of our farm products is far in excess of the value of those from any other source, and is of inestimably greater benefit to the world. The principal elements affecting the growth of plant life consist of the soil, climate, cultivation, and the amount of moisture in the ground ; and the best results are obtained only from a proper combina- tion of the same. In much of the country the soil and climate are suitable for the growth of crops of various kinds, and cultivation is entirely under the control of the farmer, but the amount of moisture in the ground is such as to preclude successful farming, in areas of enormous extent, owing to either too large or too small a water supply. The proper amount of moisture may be artificially retained in the soil by supplying it by irrigation or removing it by drainage. The United States may be divided into three zones, according to the annual rainfall : The humid zone, where the rainfall is over 30 inches per year; the semi-arid zone, where the rainfall varies between 20 and 30 inches per year; and the arid zone, where the rainfall is less than 20 inches per year. The arid zone is situated mainly in the western half of the country, while the humid zone lies to the east; and intermediate between them is the semi-arid or semi-humid zone, as it is some- times called, the line of demarcation between which and the other zones is not sharp. This zone includes in general North and South Dakota, western Nebraska, western Kansas, Okla- homa and the Pan Handle, and part of central Texas. 1 2 PRACTICAL IRRIGATION. Fig. 1 is a map of the three zones of the United States, as given in " Irrigation in the United States " by F. H. Newell. It is popularly supposed that the designation " arid " implies that the land is largely of a desert character. Such, however, is not the case, aridity simply implying that the land receives a comparatively limited supply of moisture, and does not have any reference to the nature of the soil. In fact, only 7 per cent of the arid region is composed of desert land. The area of the arid zone consists of two-fifths of the total area of the country, and on much of this land, farming, without irrigation, is impracticable, and the land is almost worthless; while with irrigation it can be B humid %Zsemi arid f"l a TV a? Fig. 1. U. S. Map. Zones of Rainfall. made highly productive and of great value. All the other elements of successful farming are present except moisture, and it needs but the application of water to the land to transform the country from a wilderness to a prosperous and productive property. The growth in value due to irrigation is by no means confined to the land alone, but results in general benefit to the country in the establishment of prosperous communities and the construction of railroads, which open up the land and carry its products to market. The growth in land value due to irrigation is remarkable, showing, however, that the real value of the land is absolutely dependent on the application of water thereto. For example, irrigable land in Northern Colo- rado along the Cache Poudre River, sells readily, with the water right attached, for from $100 to $200 per acre, while adja- cent land, similar in every respect, except for the absence of water rights, is worth only a few dollars per acre. The same is true in many sections in the west where the value of irriga- WHAT IRRIGATION HAS ACCOMPLISHED. 3 tion is appreciated. In some localities notably in Southern California water rights are much more valuable. As arid land is usually valuable only when water is applied thereto, it has been held by some of the leading authorities on irrigation that where the water was limited, the water right should be inseparably attached to the land. This is the law in some states, and in general results in material benefit, serving to prevent speculation in water rights, with its consequent ills. Irrigation consists in supplying artificially to the soil the moisture needed for the growth of plants. All soils are composed of minute grains or particles between which are void spaces. These voids will in general range from 30 per cent to 50 per cent of the total volume, depending on the relative sizes of grains, and on their arrangement. For example, crushed rock will have a certain percentage of voids, but if gravel be mixed with the rock, so as not to increase its volume, it will partially fill the spaces between the rock, and the mixture will have a much smaller void space than the rock alone. If this mixture be shaken, the rock and gravel will readjust themselves, settling, and leaving a still smaller void space. If the entire void space in a soil is filled with water, the soil is said to be saturated. The growth of plants requires a certain amount of moisture in the soil to feed the nutriment therefrom to the roots of the plants. Either too much or too little moisture is detrimental to plant growth, and efficient irrigation consists in supplying the requisite amount of moisture to the soil. However, a fairly wide range of percentage of moisture in the soil will in general give satisfactory results. When the soil contains about 20 per cent of saturation water, it is dry to all appearances, and is not suitable for plant growth. According to Professor Fortier, about 60 per cent of the volume of clay soils and 40 per cent of the volume of sandy soils are open space, while the loams range between. The moisture in soils may be regarded as composed of two parts the hygroscopic moisture which clings to the grains and requires a considerable amount of heat to drive it off, and the free moisture which fur- nishes nourishment to the roots of plants. About one pound of free moisture per ten pounds of soil is required for a good plant growth. This is an approximation varying of course somewhat with the nature of the soil and crop, and can be tested in the 4 PRACTICAL IRRIGATION. following manner: Take an average sample of the soil between the highest and lowest levels of the roots, weigh the same, and then spread it out in a pan in a thin layer and dry it for a day in the sun, weighing again. The difference is the free water. The sample taken where the plants are growing well will show the proper amount of moisture. The moisture required for plant growth will vary with the condition of the crop. For example, crops such as onions, strawberries, etc., require moisture, especially during the time the bulbs and the berries are maturing. Climatic conditions largely affect the irrigation requirements. It is not sufficient that the total rainfall be up to a certain quantity, but the dis- tribution thereof should also be such as to insure the proper moisture in the ground during the growing season. In many arid countries almost the total supply of moisture must be provided by irrigation, while in humid countries irrigation is simply a protection against the effect of a drought. The depths of the roots of the plants have a very important effect on the sensitiveness of the plants to dry spells. The moisture in the soil, except just after a rainfall or irrigation, will, within limits, at first increase with the depth, the surface layers drying off first. Deep-rooted plants are not so sensitive to short droughts as plants whose roots are nearer the surface. The moisture applied to the soil is disposed of in three manners. A large part is evaporated from the surface of the soil, another part drains through the soil and runs to waste, while the third part is useful in nourishing vegetation, in the formation of the crop, and in providing for the transpiration losses thereof. The leaves of plants are provided with hundreds of minute openings per square inch. It is through these openings that the plant receives from the atmosphere the carbon necessary for the growth of the plant, which unites with the sap from the effect of the light rays. These openings into the central portion of the leaf furnish passages for the evaporation of water from the leaf. This is known as the transpiration loss, the moisture being carried off by the air. The openings into the leaves close up automatically when it is dark, thus checking the loss of moisture which would otherwise occur. So nature has provided plants with means for conserving to the utmost the supply of moisture so necessary for their growth. WHAT IRRIGATION HAS ACCOMPLISHED. 5 Tests by Professor King have shown the remarkable fact that transpiration losses occur only when it is light, and that when it is dark they practically cease. Also, unlike losses by evapora- tion, they remain practically independent of the amount of moisture in the air, but are about equal on wet or dry days. The wind, however, will increase considerably losses of this nature. In climates where the air is moist, the soil evaporation is greatly reduced ; while, if the climate is dry and subject to winds, the evaporation will be greatly increased. The nature of the soil plays an important part in the effect of irrigation. It is important in many soils where evaporation losses may be high, to take precaution to reduce the same. Particularly is this true of a soil which tends to crack open when drying after an irrigation. A fine protective mulch of earth forms the greatest protection against evaporation losses; and where it is possible to do so, cultivation as soon as is practicable after irrigation will be highly beneficial in preventing evapora- tion. It should be remembered that irrigation cannot take the place of cultivation. Experiments have shown that when the surface is kept moist for four days after water is turned on, from 1 to 3 inches in depth will be lost by evaporation. If the soil is saturated this loss will approximate the higher figure, but, if only moist, it will be nearer the lower figure. Deep soils will allow the storage of considerable quantities of water, but this is of value to plant growth mainly where the roots of the plants are also deep. If the subsoil be gravelly, care should be taken not to apply water in such quantities that a large amount may be lost by seepage through the same. On the other hand, a clay subsoil, near the surface, may hold the water so high that evaporation losses may be large. The depth to which water will penetrate will depend on the nature and condition of the soil with respect to dryness. In general, from 4 to 9 inches of water will be required to moisten the soil to a depth of 4 feet. The effect of the application of water to land will be to raise the level of the ground water, carrying with it the various salts dissolved from the soil. This is brought to the surface of the ground by capillary action, where it leaves the salts when it evaporates. Should these salts be in quantity and of a detrimen- tal character, they will accumulate until they destroy plant life. 6 PRACTICAL IRRIGATION. The various compositions known as alkali and also sodium chloride form the main sources of trouble. In land where the drainage is not naturally good, and where trouble of this nature is likely to be encountered, it may be obviated by installing artificial drainage. This, however, is usually quite expensive, and hence undesirable if it can be avoided. Economy in the use of water and frequent cultivation will be of great assist- ance in preventing damage from injurious salts in the soil, in addition to effecting excellent results in checking evapora- tion. In addition to possible damage from the salts in the soil, the rise of the ground water may cause serious damage to plant growth, by excessive moisture near the roots of the plants. The proper drainage of land is essential where extensive irrigation is to be employed, and in many places large tracts of land have been injured by receiving the drainage from adjacent irrigated land, the ground water rising sufficiently high to drown out the plant growth and in some cases to make a bog out of the country. Before endeavoring to make extensive irrigation development, it is very essential to see that the land is so situated that it has the advantages of natural drainage, since otherwise it may be necessary to install an artificial drainage system, adding greatly to the expense. In all cases, however, economy in the use of water is doubly beneficial because it decreases the cost of irri- gation and also the dangers arising from poor drainage. So drainage is as important for plant growth as is irrigation, either an excess or deficiency of water resulting injuriously. Drainage prevents the stagnation of the ground water, and allows the plant roots to draw from the air in the soil the oxygen neces- sary for plant growth. Where injurious salts are present in the ground, it also prevents them, after they are dissolved, from rising and killing vegetation. Excessive moisture renders the ground so soft that it is impossible to work it, so drainage may be of a threefold benefit. The value of irrigation depends largely on the nature of the crop as well as on the yield of unirrigated crops. The general subject of values and costs is a matter on which there is liable to be considerable difference of opinion, even in the same case. It is endeavored in this book to give as far as possible a uniform WHAT IRRIGATION HAS ACCOMPLISHED. 7 standard of determining costs. The actual cost will be made up of three parts: 1. Actual cash running expenses. 2. Interest and taxes. 3. Depreciation. Too frequently is the actual cash outlay regarded as the cost, no charge being made for the other sources of expense, though they may be often in excess of the assumed cost. The value of irrigation will be the difference between the increased value of the crop per acre due to irrigation, and the cost of irrigation, included in which will be the cost of any additional farming operations made necessary by irrigation. As has been pointed out, the value of irrigation is by no means confined to the actual direct value, but in many cases has greater indirect results in the upbuilding of the country, and of the industries to which it gives rise. In arid countries the whole crop may be due to irrigation, without which nothing can be raised. In semi-arid countries, irrigation, while not a necessity, may become a commercial necessity from the greatly increased values of the crops. In humid climates, where the rainfall is usually well distributed, irrigation is of value only when the distribution is uneven. Where conditions are favorable and the irrigation development very cheap, it will undoubtedly pay to irrigate field crops, though expensive development would preclude such a thing. In the case of garden truck where the values of crops are very large, irrigation, even though very expensive, will pay for itself many times over. Crops of this nature are more sensitive to moisture requirements than more deep-rooted crops, and frequently a drought of a few weeks may result in the total failure of the crop. The increased yield of irrigated crops and the finer product often pay for themselves even in good years. Irrigation will also make the crop mature earlier when better prices may be obtained, and will frequently allow the growth of one crop per season more than can be grown on unirrigated land. However, the actual area irrigated . in humid climates is exceedingly small as compared with arid and semi-arid climates, and is confined to truck and also to meadow irrigation where 8 PRACTICAL IRRIGATION. the water from small brooks is turned loose over the land for raising meadow grass. In general it may be stated that valuable crops can hardly afford to be without irrigation in most climates, while crops of small value can be successfully irrigated only where water is cheap or where the climate is arid. Certain crops are particularly sensitive to the 'needs of irri- gation, such as strawberries, which require moisture especially during the three weeks while the fruit is maturing. As an illustration of the value of irrigation, the following figures are taken from comparative tests on irrigated and unirrigated land at Beeville, Texas, in the semi -arid zone, and were made by Mr. J. K. Robertson, Superintendent of the State Experiment Station : Red Bermuda onions planted 4.5 inches apart in rows 15 inches between centers. COST OF FARMING 1 ACRE OF NON-IRRIGATED LAND. Plowing and harrowing $2 .00 Laying off furrows, labor in irrigation before planting, etc. 2 .00 Transplanting onions 9 .00 Restirring with five-tooth cultivator 2 .00 Water for irrigation before planting 40,000 gals 1 .60 Eight cultivations 3 .60 Hand weeding 5 .00 Pulling onions 33.3 hours, at 7.5 cents 2.50 Trimming, sacking and weighing, 100 hours at 7.5 cents . 7 .50 Total $35.20 NOTE. The land received one irrigation before planting. COST OF FARMING 1 ACRE OF IRRIGATED LAND. Plowing and harrowing . . $2 .00 Laying off furrows and labor in irrigation before planting . . 2 .00 Restirring 2.00 Transplanting 9.00 Water for irrigation before planting 1 .60 Eight cultivations 3 .60 Laying off rows for irrigation after planting 1 .50 Four irrigations water 6.70 Four irrigations labor 4.80 Pulling, trimming, sacking and weighing 190 hours, at 7.5 cents . 14 .25 Total . $47.45 WHAT IRRIGATION HAS ACCOMPLISHED. 9 Yield of non-irrigated land 1 9,075 lb., at 2 cents $381.50 Profit 346.30 Yield of irrigated land 38,056 lb., at 2 cents $761.12 Profit $713.67 NET GAIN BY IRRIGATION $367 .37 In the calculations above, no allowance was made for the fixed charges of the irrigation pumping plant, which it would be, of course, impossible to figure for an experiment station. From corresponding stations, this would be, say, about $17, leaving a total net profit of $350 per acre, due to irrigation. On the same farm irrigated cabbage yielded 17,632 pounds against 6144 pounds on unirrigated land. The cost of farming irrigated land was $16.88 per acre against $9.08 per acre for unirrigated land. At 2 cents per pound this gives a net profit of $222 per acre for irrigated over unirrigated crops, and approx- imating fixed expenses this will still allow $205 net gain due to irrigation. The greatest part of the irrigated land is devoted to raising field crops, such as alfalfa, wheat, corn, etc., and crops like rice. Rice irrigation is, however, in a class by itself, requiring, as usually practiced, the complete submergence of the land. The values of these crops will usually lie between $20 and $80 per acre per year. On pages 37 to 40 are given further data of the cost and value of irrigation in various parts of the country. Irrigation should effect a uniform distribution of water over the land, to give the best results. However, this result is only approximated by the various methods in use. The cost of irrigation may in general be regarded as composed of two parts: (1) Cost of bringing the water to the land to be irrigated. (2) Cost of applying the water to the land. If the supply of water is not limited, the most efficient irri- gation would be the application of such a quantity of water that, for a given area, the net returns (that is, the difference between the value of the crop and the cost of irrigation plus the cost of farming) give the greatest interest on the investment. The size of the crop will in general increase with increasing quantities of water, rapidly at first, and then more gradually, until finally a maximum is reached, after which increased amounts of water will be a detriment. It will not pay to irri- 10 PRACTICAL IRRIGATION. gate up to the point where the greatest crop is obtained, but irrigation should stop where the cost of additional irrigation exceeds the increased value of the crop resulting therefrom. The periods between the application of irrigations (the irri- gation frequency) will have an important effect on both the cost and results. The advisable frequency of irrigation depends on the soil, climate, nature of the crop, and method of irrigation. A deep soil, retentive of moisture with deep-rooted plants, will require less frequent irrigation than a shallow soil where the roots of the crop are nearer the surface. Frequent irrigation has the effect of keeping the soil more nearly with the desired amount of moisture. However, on the other hand, the expense of frequent applications of water is greater than the expense of applying the same total quantity not so often. Also the application of small quantities of water is apt to be very inefficient, since a larger percentage will be lost by evaporation from the moist surface of the soil than would be the case were a greater depth applied. In a climate liable to sudden and heavy rains during the irrigation season it is advisable not to apply the water in too great amounts, since a rain following a heavy irrigation might do considerable damage from excessive moisture. Hence it is evident that the advisable amount of water to apply in irrigation and the advisable frequency of irrigation depend largely on the cost of irrigation and the value of the crop as well as on many other considera- tions, and that in general it will not pay to irrigate sufficiently to obtain the maximum crop. It is obvious, therefore, that irri- gation is far from an exact science, and that it is natural to expect great variations in both the quantities of water applied and the frequency of application. CHAPTER II. UNITS IN USE. THE following units of measurement are in use in irrigation practice. The quantity of water applied per unit of land is usually expressed as the depth in feet or inches to which the land would be covered were the water evenly spread over it. This is referred to as the depth of irrigation. Volumes of water are expressed in cubic feet, gallons, acre-feet and acre-inches, the acre-foot being the quantity of water con- tained in an acre 1 foot deep. The flow of water is expressed in cubic feet per second (cu. ft. per sec.) and in gallons per minute (gal. per min.). Capacities are often conveniently expressed in terms of the flow required to deliver the capacity in 24 hours. As approxi- mations the following may be easily remembered: One cu. ft. per sec. = 450 gal. per min., and this flow will cover an acre 2 feet deep in 24 hours. Three acre-feet = 1,000,000 gallons. Another unit commonly used is the miner's inch, the flow of water from a 1-inch square orifice under 4-inch water pressure above the center of the hole. This is, however, defined differently in different, parts of the country in terms of an actual flow vary- ing from about 10 to 13 gal. per min. It is now legally defined in California as a rate of flow of 1.5 cu. ft. per min., or 11.25 gal. per min. The term "duty of water" is used in two different senses as the number of acres a given flow in cu. ft. per sec. will irrigate, and as the annual depth of water applied by rain and irrigation to the land. Neither of these terms by themselves gives any information about the length of the irrigation season, or frequency of irrigation. The annual depth of water (rain and irrigation) applied to the land cannot necessarily be used by itself as a criterion of the needs of irrigation. Unequal distribution of rainfall may lead 11 12 PRACTICAL IRRIGATION. to erroneous conclusions if we admit such an assumption, par- ticularly if the crop requires water at a time when there is no rain. In arid countries, where irrigation water is far in excess of rainfall, this may be a matter of small importance, but in a country of considerable rain it might become a matter of some moment. The annual depth of irrigation tells nothing about the length of the irrigation season, and hence of itself furnishes no measure, except in a general way, of the proportions of the plant and ditches which must be provided. The frequency of irrigation and the rate of supply of the water required per irrigation, on the contrary, furnish definite information as to these points. A much more suitable basis upon which to make irrigation calculations is the following: Irrigation plants should in gen- eral be figured on a basis of supplying water at a rate sufficient to irrigate continuously all the desired land, provided there is no rainfall. This means that a certain continuous flow of water is required per acre, which may be conveniently reckoned in gal. per min. per acre. In order to obtain this figure, the fre- quency of irrigation and the depth per irrigation must be known. Dividing the gallons per acre by the time in minutes between irrigations, gives the required flow in gallons per minute. This is the quantity which can best serve as the basis for irrigation calculations and for the design of the proper size of plant. Multiplying the acreage by the required gal. per min. per acre gives the required gal. per min. of the plant, should it be operated continuously 24 hours a day. To find the proper capacity plant for shorter hours of operation, divide the required capacity given above by the percentage of the day it is desired to operate. To find the total quantity of water which must be applied per year, multiply the depth per irrigation by the number of irriga- tions per crop if the weather be dry. This gives the total depth of irrigation. Subtracting from this the rainfall during the irrigation season gives the approximate depth of water to be furnished by irrigation per crop. If the maximum flow which must be furnished ran continuously through the year, it would cover the land to a certain depth. However, the water for irrigation will run only a comparatively small percentage of the time, and will cover the land to a much less depth. The ratio of the depth to which the land is irri- UMTS IN USE. 13 gated to the depth of irrigation, were the actual flow to be con- tinuous for a year, is known as the irrigation factor. The irrigation factor, which corresponds to the annual load-factor in power plants, is the percentage of the year the plant runs at full load. The nearer the actual flow approaches to the required flow, the higher the irrigation factor, provided the former is greater than the latter. The method of calculation outlined applies in particular to places where water can be obtained, when required in a quantity sufficient for the irrigation of land. There are, however, many places where the water is limited in quantity, and where, when there is no storage, the available supply runs far short of the needs of the land during the irrigation season. In these cases it is impossible to attempt to use as a basis of calculation for the needs of the land for water, and irrigation is of necessity a compromise measure between what is most desirable and what can be obtained. Where the soil is deep and will allow the storage of water therein, it is not uncommon to apply heavy irrigations, when the water supply is available, to tide over the dry weather which may follow. There is, however, such a large percentage of cases where suitable water supply is continuously available, that the plan of calculation outlined is of material assistance in the proper design of plants. Tables I and II will greatly facilitate the calculation of irri- gation plants. In Table I, column 1 is the duty of water in acres per cu. ft. per sec. which indicates the number of acres which a flow of 1 cu. ft. per sec. will irrigate; column 2, the required flow of water in gallons per minute per acre, represents the requirements of the land under existing conditions of water supply; columns 3 to 13 inclusive represent Q, the depth of irrigation to which the land would be covered were the flow provided in the corresponding line of column 2, to be applied for 24 hours per day for the number of days stated in the head of the appropriate column. The remaining columns of the table indicate the annual depth of water for irrigation for various irrigation factors given in the headings of the columns, the figures in the horizontal lines corresponding to the appropriate required flow in gallons per minute per acre. Tables III to VIII are conversion tables for various units of 14 PRACTICAL IRRIGATION. quantity and flow used in irrigation work. In order to abbre- viate as much as possible, these tables have been given for only the nine units represented in the first column. To illustrate the use of the table, suppose that it were desired to ascertain the cubic feet per second flow which would deliver 92 acre-feet per day. Referring to Table III, 9 acre-ft. per day = 4.5374 cu. ft. per sec., hence 90 acre-ft. per day = 45.374 cu. ft. per sec., 2 acre-ft. per day = 1.0083 cu. ft. per sec. for a day. Hence 92 acre-ft. = 46.38 cu. ft. per sec. for a day. To illustrate the use of Tables I and II, consider the problem of determining the size of plant to irrigate 200 acres to a depth of 2.55 inches every 12 days,the number of irrigations per year being 10. By Table II this requires a flow of 4.0 gal. per min. per acre, or 800 gal. per min., and will cover the land to a depth of 2.1 ft. per year, the irrigation factor being 33 per cent. If the plant be run only half the day,the required flow is 1600 gal. per min. and the irrigation factor 16 per cent. Should there be any unusual losses in seepage in bringing the water to the land, the flow should be correspondingly increased. The calculations and figures as given above, apply to one kind of crop, or at least to a crop requiring irrigation at one certain time of year at a certain rate. Provided it is desired to irrigate different kinds of crops which require water in different seasons of the year, the quantity of water to be supplied may be arrived at in one of two ways: either by making assumption of average values of the needs of the crops, or else by figuring each one out inde- pendently. The irrigation capacity which should be furnished will, of course, depend upon the manner in which the respective demands for water overlap. For example, if one crop requires water in the summer and fall, and another in the spring and summer, the capacity should, of course, be proportioned to the maximum demand, which would be in the summer. UNITS IN USE. 15 0,8 gj " m 2- C5 CO Oi t^ -^ CO i ( Oi 00 t> CO lO O TJH Tt< Tti CO CO C^ C 00 t^ iO O rf CO CO "3 ^ ^ CO CO (N ; CO CO *O Tj< -* TJ< CO CO CO (N (N iM CO CD O 1O - - CO CO (N COiO TJH T-J OO >O CO (N O O5 O5 GO I> l> O O rtj -^ TJI CO Tt< t^ CO ^ ^ c^>^ p o> cS oo t> . r^ i i Oi OO CD *O TJH (N OS 00 l> l> UNITS IN USE. TABLE II. 17 6 Duty of water. Acres per 449 224 150 112 90 75 64 56 50 u. ft. per sec. Required flow gal . per I 2 3 4 5 6 7 8 9 min. per acre days 7 0.37 0.74 1 .11 1.48 1 .86 2.23 2.60 2.97 3.34 8 0.42 0.85 1.27 1.70 2.12 2.55 2.97 3.39 3.82 Q 9 0.480.96 1.43 1.91 2.39 2.87 3.34 3.82 4.30 10 .53 1 .06 1.59 2.12 2.65 3.18 3.71 4.24 4.78 Depth of irriga- 12 .64 1 .27 1.91 2.55 3.18 3.82 4.46 5.09 5.73 tion in inches if 15 0.801.59 2.38 3.18 3.98 4.78 5.58 6.37 7.17 applied for 24 20 1.06 2.12 3.18 4.24 .5 .30 6.37 7.43 8.49 9.56 hrs. every 30 1.59 3.19 4.78 6.37 7.96 9.5511.14 12.72 14.32 40 2.12 4.25 6.38 8.49 10.01 12.73 14 .85 16.97 19.10 50 2.65 5.31 7.96 10.60 13 .26 15 .92 18 .56 21.21 23.87 60 3.18 6.37 9.56 12.72 15.91 19.10 22.28 25.47 28.64 1 00 1.61 3.23 4.84 6.46 8.07 9.69 11.30 12.91 14.53 .90 1.45 2 .90 4 .35 5.81 7.26 8.72 10.1711.61 13.07 .80 1.29 2 .58 3 .87 5.16 6.45 7.74 9.04 10.3211 .61 .70 1.13 2 .26 3 .38 4.52 5.64 6.77 7.90 9 .04 10.17 M .60 .97 .94 2 .90 3.87 4.84 5.80 6.77 7.74 8.72 .50 .81 .6l!2.42 3.23 4.03 4.84 5.64 6.45 7.26 Annual depth of .45 .73 .45 2 .18 2.90 3.63 4.35 5.08 5.82 6.54 water in feet .40 .65 .2911 .94 2.58 3.23 3.87 4.52 5.16 5.81 for irrigation .35 .56 .13 1 .69 2.26 2.82 3.39 3.95 4.52 5.09 factors. .30 .48 .97 1.45 1.94 2.42 2.90 3.38 3.87 4.35 .25 .40 .81 1.21 1.61 2.02 2.42 2.82 3.23 3.63 .20 .32 .65 .97 1.29 1.61 1.94 2.26 2.58 2.90 .15 .24 .48 .72 .97 1.21 1.45 1 .69 1.94 2.18 .10 .16 .32 .48 .65 .81 .97 1.13 1.29 1.45 TABLE III. ACRE-FEET CONVERSION TABLE. Acre-ft. Acre-in. Cu. ft. Gals. Cu. ft. per sec. for a day Gals, per min. for a day 1 12 43,560 325,880 .50416 226.29 2 24 87,120 651,760 1.0083 452.6 3 36 130,680 977,640 1 .5125 678.9 4 48 174,240 1,303,520 2 .0166 905.2 5 60 217,800 1,629,400 2.5208 1,131 .5 6 72 261,360 1,955,280 3 0250 1,357.7 7 84 304,920 2,281 ,160 3.5292 1,584.0 8 96 348,480 2,607,040 4 .0332 1,810.3 9 108 392,040 2,932,920 4.5374 2,036 .6 18 PRACTICAL IRRIGATION. TABLE IV. ACRE-INCH CONVERSION TABLE. Acre-in. Acre-ft. Cu. ft. Gals. Cu. ft. per sec. for a day Gals, per min. for a day 1 .08333 3,630 27,157 .04201 18 .858 2 .16667 7,260 54,314 .08403 37.72 3 .25000 10,890 81,470 .12604 56.58 4 .33333 14,520 108,627 .16805 75.43 5 .41667 18,150 135,784 .21007 94.29 6 .50000 21,780 162,940 .25208 113.15 7 .58333 25,410 190,099 .29409 132 .01 8 .66667 29,040 217,254 .33611 150 .86 9 .75000 32,670 244,410 .37812 169 .72 10 .83333 36,300 271,567 .42013 188 .58 11 .91667 39,930 298,724 .46215 207 .44 12 1 .00000 43,560 325,880 .50416 226 .29 TABLE V. CUBIC-FEET CONVERSION TABLE. Cu. ft. Gals. Cu. ft. Gals. per sec. for per min. for Acre-ft. Acre-in. a day a day 10,000 74,805 .11574 51 .948 .22956 2 .7548 20,000 149,610 .23148 103 .90 .4591 5.510 30,000 224,415 .34722 155 .85 .6887 8.265 40,000 299,220 .46296 207 .79 .9182 11 .019 50,000 374,025 .57870 259 .74 1 .1478 13 .774 60,000 448,830 .69444 311 .69 1 .3774 16 .529 70,000 523,635 .81018 363 .64 1 .6070 19 .284 80,000 598,440 .92592 415 .58 1 .8365 22 .038 90,000 673,245 1 .4066 467 .53 2.066 24 .793 TABLE VI. GALLONS CONVERSION TABLE. Cu. ft. Gals. Gals. Cu. ft. Acre-ft. Acre-in. per sec. for per min. for a day a day 100,000 13,368 .30689 3 .6827 .15468 69 .444 200,000 26,736 .6138 7.365 .3094 138 .89 300,000 40,104 .9207 11 .048 .4640 208 .33 400,000 53,472 1 .2276 14 .731 .6187 277 .78 500,000 66,840 1 .5345 18.414 .7734 347 .22 600,000 80,208 1 .8413 22.096 .9279 416 .66 700,000 93,576 2.1482 25 .779 1 .0826 486 .11 800,000 106,944 2 .4551 29 .462 1 .2374 555 .55 900,000 120,312 2 .7620 33 .144 1 .3921 624 .99 UNITS IN USE. 19 TABLE VII. CUBIC FEET PER SECOND FOR A DAY, CONVERSION TABLE. Cu. ft. Gals. per sec. per inin. for Acre- ft. Acre-in. Cu. ft. Gals. for a day a day 1 448.83 1.9834 23.80 86,400 646,315 2 897.7 3.967 47.60 172,800 1,292,630 3 1,346.5 5.950 71.40 259,200 1,938,945 4 1,795 .3 7.934 95.20 345,600 2,585,260 5 2,244 .2 9.917 119.00 432,000 3,231,575 6 2,693 .0 11 .900 142.80 518,400 3,877,890 7 3,141 .8 13.884 166.60 604,800 4,524,205 8 3,590 .6 15 .867 190.40 691,200 5,170,520 9 4,039 .5 17.850 214 .20 777,600 5,816,835 TABLE VIII. GALLONS PER MINUTE FOR A DAY, CONVERSION TABLE. Gals. Cu. ft. per min. per sec. for Acre-ft. Acre-in. Cu. ft. Gals. for a day a day 100 .2228 .4419 5.303 19,250 144,000 200 .4456 .8838 10.606 38,500 288,000 300 .6684 1 .3257 15.909 57,750 432,000 400 .9812 1 .7676 21 .212 77,000 576,000 500 1 .1140 2 .2095 26 .515 96,250 720,000 600 1 .3368 2 .6514 31 .818 115,500 864,000 700 1 .5596 3 .0933 37.121 134,750 1,008,000 800 1 .7824 3 .5352 42 .424 154,000 1,152,000 900 2.0052 3 .9771 47.727 173,250 1,296.000 CHAPTER III. METHODS OF IRRIGATION IN USE. BRIEFLY stated, the following are the methods of irrigation employed : 1. Flooding (the entire surface of the ground being wet), (a) Land is divided into checks by contour lines from 3 inches to 10 inches vertical distance apart, and a small levee thrown up all around each check into which the water is admitted till the check is flooded. (6) Bed system, where the land is divided by small levees into long rectangles, and water is admitted at the upper end at several places, passing over the land in a sheet. (c) Contour ditch and tablet irrigation, where the water is admitted from cuts in the ditch bank and spread over the land. This requires considerable attention to make a uniform distribution. (d) Wild flooding. Water is spread over large areas of land from a few outlets. This results in very unequal distri- bution. 2. Furrow system, where the water is admitted to furrows usually from 12 inches to 4 feet apart and flows through them, sinking into the ground and not wetting the entire surface. 3. Basin system, where the water is admitted to small basins or checks around trees. This system is used mainly for young trees. 4. Sprinkling by revolving water witches or sprinklers, which are usually allowed to run in one place for from 1 to 2 hours. 5. Hand sprinkling from a hose. In estimating the cost of applying water, there are two bases on which it can be figured: 1. Cost of applying 1 acre-foot. 2. Cost of irrigating 1 acre. Provided the quantity of water it is desirable to apply is not exceeded, the first method gives preferable results in comparing 20 METHODS OF IRRIGATION IN USE. 21 costs of application. Hence in this event the flow which one man can handle determines the efficiency of application. Flooding by contour checks usually allows the handling of much larger streams per man than any other system if the ground slope is suitable. However, it usually necessitates the application of a greater depth of water than the other systems. A small flow of water cannot be used to advantage, since it results in a very wasteful and inefficient distribution. The furrow system has a very important advantage over flooding or sprinkling systems of irrigation, in that the entire surface of the ground is not wet, resulting in less evaporation loss, in applying the water nearer the roots of the plants and in promoting deep rooting of plants, the roots reaching farther down where they are protected from the surface heat and can draw on the moisture deeper in the soil. If the soil bakes when wet, the furrow system should be used instead of flooding, and the furrows cultivated as soon as sufficiently dry, thus preventing baking, and keeping a fine protective mulch of earth over the moist earth, preventing rapid loss by evaporation. However, the furrow system will not allow handling of as great quantities of water per man as flooding by contour checks, and will generally cost more for labor per unit quantity of water applied and per irrigation. Sprinkling systems are employed mainly in the East, where the irrigated farms are very small. They are much used for truck. The cost of sprinkling by revolving water-witches is independ- ent of the depth, and is dependent only on the cost per irriga- tion for moving the apparatus. Hand sprinkling is directly dependent on the quantity of water applied, and is very expensive. The stream handled by a man is small. Hence irrigation by this means is very light, in many cases not exceeding 0.25 inch. Such irrigation is very inefficient since a large percentage of water is lost by evaporation. It is better to apply one 1-inch, than four 0.25-inch irrigations. Hand sprinkling, however, has the advantage of allowing a light irrigation to be quickly given to a large area. From investigations by the author in Southern Texas and in the Eastern States the following information has been compiled as to irrigation practice along the lines laid down. This informa- 22 PRACTICAL IRRIGATION. tion was obtained from a large number of plants, many of which, as might be expected, were radically different. In irrigation by checks, the sizes of checks vary from 0.25 to 200 acres. The latter is many times too large, and is not to be recommended. It was used in the irrigation of rice. For other crops, checks usually vary from 0.25 to 10 acres, the proper size depending on the soil slope and flow of water available. In bed irrigation the length of bed will vary between 100 and 700 feet, being usually from 100 to 250 feet long. The width varies from 10 to 50 feet, usually lying between 10 and 20 feet. The flow per bed varies from 200 to 1000 gal. per min., requir- ing between 3 and 20 minutes to pass over the bed. 3. Tablets vary from 300 to 1200 feet in length, and from 25 to 65 feet in width. 4. Furrows vary in length from 40 to 600 feet, and are run from 1 foot to 4 feet apart. It is usually good practice to run furrows from 100 to 300 feet long. If too long, the distribution of water is very uneven; and if too short, the labor of changing the water is too great. If the ground absorbs water rapidly, the furrows should be comparatively short; but if water sinks in slowly, they should be longer. The time to run through the furrows varies between 5 and 500 minutes, usually varying between 15 and 150 minutes. Values of flow per furrow vary from 5 to 300 gal. per min. The best practice usually lies between 10 and 30 gal. per min. Too low a value of flow tends to effect an unequal distribution, and too great a value of flow will tear away the furrow. In orchard irrigation the water sometimes runs continuously in the fur- rows for two to three days. This information gives an approx- imate idea of the limits of irrigation practice for various methods of irrigation. CHAPTER IV. EVAPORATION. THE efficiency of irrigation water may be measured by the actual useful work performed by a given quantity of water. To increase the efficiency, requires a careful investigation of the reasons for the loss of water. Evaporation is responsible for many of the greatest losses of water, both from reservoirs, and from the land itself. Evaporation consists in the absorption of water in the form of vapor by the air. It should not however be confused with the transpiration losses of plants, which while they may be included under the same general heading, have, as has been pointed out, important points of difference in the laws they follow. The air is capable of containing in suspension a certain amount of moisture in the form of an invisible vapor. This quantity de- pends on the temperature, and increases rapidly with increase of temperature, as is shown in the following table. WEIGHTS OF DRY AIR, AND OF THE MOISTURE OF SATURA- TION, PER CUBIC FOOT, AT PRESSURE OF 29.92 INCHES OF MERCURY. Temperature. Degrees Fahr. Weight of 1 cu. ft. of dry uir. pound Weight of vapor in 1 cu. ft. of saturated mixture, pound 0.0864 0.000079 32 0.0807 0.000304 52 0.0776 0.000627 62 0.0761 0.000881 72 0.0747 0.001221 82 0.0733 0.001667 92 0.0720 0.002250 102 0.0707 0.002997 112 0.0694 0.003946 122 0.0682 0.005142 132 0.0671 0.006639 23 24 PRACTICAL IRRIGATION. When air contains its maximum amount of vapor, it is said to be saturated, and any diminution of temperature will result in a deposition of moisture from the air. From the table it appears that one cubic foot of air at 132 F. can hold 84 times as much moisture as at F. When air which is not saturated is in con- tact with a moist surface, it will tend to absorb moisture there- from. The actual rate of absorption or evaporation will depend not only on the percentage of saturation of the air, but also on the temperature of both the air, and of the surface, and in par- ticular on their temperature just where they are in contact. The higher the temperature of either, other conditions remaining constant, the more rapid the evaporation. The important rela- tion between the absorptive power of the air, and its tempera- ture as given in the preceding table, is worthy of particular note, owing to the high evaporation losses in irrigation. Wind will greatly increase the evaporation due to the more intimate con- tact of the air and the moist surface, be it a water surface, or the surface of the ground. Thus, for example, different experimenters state that wind will increase the evaporation at percentages per mile of wind per day, varying between 0.5 per cent and 2 per cent. It is doubtful whether any such simple relation may be obtained between these two quantities, particularly in view of the wide divergence of the results. So many elements enter into the problem in practice that without ascertaining the effect of each one, it is difficult to reach satisfactory conclusions. The rapidity of evaporation is largely dependent on the dryness of the air. The condition of the air with reference to moisture is usually expressed as the per cent of humidity, i.e., the per cent of satura- tion moisture the air contains. Thus it is evident that the evap- oration is dependent on the six following conditions: 1. Area of the surface in contact with the air. 2. Temperature of the surface. 3. Temperature of the air. 4. Wind velocity. 5. Per cent humidity of the air. 6. Atmospheric pressure. The temperature of the body is dependent on the amount of heat which it will receive, the amount of heat which it will trans- mit elsewhere, and on its ability to absorb heat. Excluding chemical changes and electrical manifestations, there are three EVAPORATION. 25 methods of the usual exchange, or transference of heat: con- duction, convection, and radiation. Heat of conduction is heat which is transmitted through a body itself, or from one body to another. Heat of convection is heat which is carried away by transference to another body which is then transported; as for example, heat carried away by air currents. Heat of radiation is heat which is transmitted through the ether as radiant energy; such as the heat of the sun. If equal quantities of heat be applied to equal weights of differ- ent bodies, then the rise in temperature will depend on the nature of the substance. Water has many times the heat storage capacity of most other substances, and hence will not rise nearly as much in temperature as other materials, under the similar conditions just outlined. The radiant energy which a body can receive, or transmit, depends on the color, and the nature of the surface. Polished and light colored surfaces will reflect radiant energy, and will not absorb as much heat as dark surfaces. It is well known that light surfaces will not become as warm as dark surfaces when exposed to the sun. Hence the surface of the soil, when exposed to the sun, will become far hotter than a w r ater surface under similar conditions, and if the soil surface be saturated with water, the loss by evaporation will be far greater than from the water surface. The reasons for this are fourfold : 1. The water will reflect a large amount of radiant energy which the soil will absorb. 2. The transmission of heat by conduction is greater in water than in the soil. The earth being a poor conductor of heat, the temperature effects due to the daily variation are confined to the surface layers, and are thus intensified at the surface. 3. The specific heat of water being greater than that of earth, the temperature rise of the earth will be greater than that of the water. 4. The irregular surface of the ground will allow a greater sur- face area in contact with the air, than is the case with water. That these facts are true, is amply borne out by the results of experiments. Thus Professor Fortier in some experiments on evaporation found that under the conditions of the tests, the evaporation from a saturated soil was 2.5 times the rate of evap- oration from water surfaces. The rate of evaporation from the 26 PRACTICAL IRRIGATION. soil will of course vary greatly with the moisture in the top layer, decreasing rapidly as the soil becomes dryer. There are so many different elements entering into the rate of evaporation, that we must be careful not to apply experimental or other data to cases to which they do not belong. The results of both experiment and theory show that the rate of evaporation is directly depend- ent on the amount of moisture in the upper layer of soil, the tem- perature, the percentage humidity of the air, and the wind velocity. It will be natural to expect a greater increase of temperature, and hence higher evaporation in the case of dark soils than in the case of light soils, due to the greater amounts of heat absorbed. This will undoubtedly be true provided the only physical differ- ence between the light and dark soils consists in the color. There are, however, other elements which enter into the problem. Thus a soil which tends to crack open will facilitate evaporation. Some soils possess greater capillary power than others, and will tend to draw water to the surface. The top layer being kept moist will of necessity cause greater evaporation. This is notably true of alkali soils. The dryer the top layer of soil, the less will be the evaporation loss. The moisture from below the surface, before evaporating, must first pass through the top layers, to which it is drawn by capillary action. Whatever circulation of air exists in the ground will also have some effect in assisting evaporation. Heat will have the effect of increasing considerably this action. Hence the best way to conserve the moisture in the ground is to protect it both from heat, and from contact with the air, and not . to wet the surface. Dry sand, or earth in a finely subdivided state is an excellent nonconductor of heat, owing in large part to the great multitude of air spaces between the particles. The air being practically confined has little opportunity to circulate, and to transmit heat by convection. A good mulch of dry earth will be very effective in preventing evaporation losses. Extensive experiments which have been made along these lines, have shown the great value of cultivation, not only for irrigated lands, but also to conserve the supply of moisture so necessary for dry farming. The ground should be cultivated as soon as possible after irri- gation, and in irrigating as little surface as possible should be EVAPORATIOX. 27 wet. This suggests that sub-irrigation by buried pipes would be the most efficient. This has been tried in a few instances, but as yet has proven rather impractical owing to the high first cost, and to the difficulty of effecting an equal distribution of water. The roots of the plants which are naturally lured to moisture, in time will clog up the openings in the pipes, and the pipes them- selves. In some cases if the subsoil be deep and gravelly, much water may run to waste; also the distribution of water is apt to be uneven since water will percolate vertically more rapidly than horizontally. From the standpoint of economy the deep furrow, i.e., from 6 to 12 inches deep, will in many cases give the best results. There are, however, objections to deep furrows for some classes of work, owing to the increased cost of furrowing and culti- vation, and because deep furrows may injure shallow-rooted trees. On the other hand, deep furrowing promotes deep root- ing of trees, which will thus have a greater supply of both moisture and fertilizer from which to draw. In bulletin No. 177 of the Office of Experiment Stations, United States Department of Agriculture, Professor Fortier gives the results of many interesting experiments to determine the loss of water by evaporation from the soil, which show in particular the importance of deep cultivation in conserving the supply of moisture in the ground. The roots of trees and plants will natur- ally spread where they can obtain moisture from the soil. In a wet season when the ground is kept moist by frequent rains, shallow rooting is encouraged, and when the upper layers of the soil become dry in the dry season, these roots are of no value, and will wither. Deep cultivation prevents the formation of roots in the surface soil, and makes them go further downwards, where they will be of use during dry seasons. Thorough and deep cultivation, through lessening evaporation, will prevent both the rise of injurious salts, and also the rise of those salts which are beneficial for vegetation, and the removal of the latter from the zone of the roots. The following figures give a brief summary of some of professor Fortier's experiments. The experiments on the evaporation from soils w r ere conducted in tanks of two sizes, 23.5 inches in diameter and 47 inches deep, and 17 inches in diameter and 30 inches deep respectively, which were filled with earth and set 28 PRACTICAL IRRIGATION. flush with the ground so as to imitate, as far as possible, the con- ditions of the rest of the soil. They were set inside other tanks provided with a water jacket to facilitate their removal for weighing. The results of the experiments are the averages of a number of observations. Most of the experiments were conducted in Southern California during the summer and fall. During the tests at Riverside the daily average temperatures reached a maximum of 93 F. at 1 P.M., and a minimum of 56 at 11 P.M. and 5 A.M. a difference of 37. The average difference between the 12-hour periods of day and night was 24. At the depth in the ground of one foot, the daily temperature variations practically disappear. All temperatures hereafter will be given in Fahrenheit. While the temperatures of the air and soil approach each other during the early morning hours before the sun gets high, the soil in the sun at 1 P.M. had a temperature of 117, while the air in the sun had a temperature of 82 at the same hour a difference of 35 in the case of these experiments. From another series of experiments of nine weeks duration the following temperatures were obtained : AVERAGE WEEKLY TEMPERATURES DURING THE DAY. Max. Min. Average Soil in the sun 117 101 106 Air in the sun 90 76 84 Dry soil in the shade 88 77 83 Water in tank .... 82 78 79 Humid soil would not rise as high as dry soil, due to the greater specific heat, and to the greater power of conduction, as well as to the cooling effect due to evaporation. Still the increase of temperature over that of a water surface is ample to account for the effects of the greatly increased evaporation, as is shown in the following table. The soil was a sandy loam, and the tempera- tures were a mean of the morning, noon, and evening tempera- tures. EVAPORATION. 29 EVAPORATION FROM MOIST SOILS AND FROM WATER SURFACES. Temperature, Degrees Fahr. Weekly Evapora- tion Per cent Air in Soil in Soil in Moist Water Soil Water free water shade shade sun soil surface inches inches Saturated 71 76 95 83 77 4.75 1.88 17.5 76 78 106 80 1.33 1.94 11.9 76 78 106 80 1.13 1.94 8.9 76 78 108 80 .88 1.94 4.8 76 78 108 80 .25 1.94 The evaporation from water surfaces is dependent on the tem- perature, wind and humidity, as appears from the following figures for two stations, Calexico and Chico. Calexico besides being hotter than Chico, is also much dryer. EVAPORATION FROM WATER SURFACES. Chico Calexico Min. monthly water evaporation in inches Max monthly water evaporation in inches Annual water evaporation in inches 0.1 10.0 53 2.7 14.5 89 Max. temperature (monthlv) 81 93 Min temperature (monthlv) 45 52 The following results were obtained by heating and cooling water in tanks in the field, and represent the average of four stations. EFFECT OF WATER TEMPERATURE ON EVAPORATION FROM WATER SURFACES. Average water sur- face, temperature Average daily evap- oration, inches Average water sur- face, temperature Average daily evap- oration, inches 53.4 61.3 73.5 0.09 0.19 0.36 80.4 88.7 0.48 0.60 With average wind velocities of from 2.4 to 4 miles per hour, and average water temperatures of 70, the increased evaporation rate due to wind was about 0.5 per cent per mile of wind per day. 30 PRACTICAL IRRIGATION. Experiments on soils conducted during several months in the dry season, where about two inches per month are applied to the ground, show that nearly all the water will evaporate, and that poor cultivation is of little value, and in many cases is positively detrimental. In a very sandy soil, where the water will drain through readily, poor cultivation is of some advantage, but in a soil which tends to retain the water nearer the surface, poor cul- tivation may cause greater evaporation losses than no cultiva- tion. Experiments lasting three months, which were conducted to show the relation between the quantity of water applied and the evaporation loss, show that the following equation holds true. Evaporation = a + b X (the depth applied), where a, and &, are constants. In the case of one test the initial free moisture was 7.7 per cent and was equivalent to 3 inches of water. Irrigation water was applied every two weeks, and the constants, a and &, at the end of three months were a = 1.3, b = .66. The total depth applied varied from 3.3 inches to 9.8 inches. The effect of cultivation is shown in the following tables. Water was applied in 4-inch furrows, the duration of application being two days. The average temperature during the day was 81. EFFECT OF CULTIVATION ON EVAPORATION. Evapora- tion inches Water applied inches Initial Moisture, per cent Loss in inches in first 5 days un- cultivated Loss in inches in next 6 days un- cultivated 1.76 1.39 11.9 Top 12 inches dry 6 per cent in balance Loss in corresponding period (6 days) cultivated 0.64 of soil Loss in inches in first 3 days un- cultivated 0.84 8.0 Loss in inches in next 3 days un- cultivated Loss in corresponding period (3 days) cultivated 0.29, 0.10 Top 4 inches dry 3 per cent in balance of soil EVAPORATION. 31 The following table shows the effect of mulches in preventing evaporation, and is most instructive. 3.2 inches of water were applied, and after the water had sunk in, mulches of various depths were added. Average temperature during the day was 90 F. EFFECT OF MULCHES ON EVAPORATION. Evaporation in inches First 3 days Next 4 days Next 4 days Next 3 days Total for 14 days No mulch 0.43 0.13 0.04 0.01 0.19 0.03 0.01 0.00 0.08 0.03 0.02 0.01 0.02 0.02 0.01 0.00 0.72 0.21 0.08 0.02 4-in. mulch 8-in mulch 10-in. mulch ... The following table shows the effect of deep furrows in con- serving the moisture in the ground. The ground contained 4.5 per cent of free moisture at the start, and 5.1 inches of water were added in two days, and on the third day the ground was cultivated. EFFECT OF DEPTH OF FURROW ON EVAPORATION. Average Temperature in the Shade, 82 F. Losses in inches Days, land 2 3 4 5 and 6 7 8 and 9 10 Total Surface 0.73 0.25 0.10 0.11 0.01 0.03 0.00 1.23 3-in. furrow . . . 0.63 0.18 0.13 0.03 0.02 0.08 0.02 1.09 6-in. furrow . . . 0.52 0.16 0.10 0.03 0.01 0.04 0.02 0.88 9-in. furrow . . . 0.44 0.13 0.10 0.02 0.05 0.07 0.00 0.81 12-in. furrow . . . 0.34 0.10 0.10 0.04 0.03 0.02 0.00 0.63 In another case where 2.1 inches of water wore applied the loss in 34 days was 1.81 inches when using 3-inch furrows, and .49 inch when using 12-inch furrows. In these experiments the ground was cultivated as soon as it was dry. To show the effect of sub-irrigation, water was applied to tanks at various depths. The free moisture in the ground at the start was equivalent to a depth of 4.4 inches, and a 2-inch mulch was 32 PRACTICAL IRRIGATION. placed on top. 5.3 inches of water were applied. The evapo- ration losses in ten days were as follows, the average temper- ature during the day being 89 F. in the shade. EVAPORATION FROM SUB-IRRIGATED SOILS. Depth of application in inches Loss in inches 3 1.34 6 0.96 9 0.55 12 0.32 Contrary to what might be expected, at the end of the ten days the moisture content near the surface was greater, the deeper the irrigation. The following table shows the comparative evaporation losses for sub-irrigation at two feet depth, and for surface irrigation. 7.0 inches of water were added in four applications, a week apart. SUB-IRRIGATION AND SURFACE-IRRIGATION EVAPORATION. Kind of soil Sub-irrigated Surface irrigated Sandy loam .... 74 4 22 Sandy soil 62 3 64 Dark loam 1 96 5 63 Average 1 11 4 49 Alkali soil . 2.81 4.35 Loss in inches in 26 days Thus in the case of sub-irrigation, only one-fourth of the water lost in surface evaporation was lost. The alkali soil was not in- cluded in the average, since alkali tends to keep the surface moist. From the standpoint of economy of water, the best time to irrigate is at night, or in the evening. In many cases there are objections to night irrigation, since it is far more difficult to see properly than in the day time, and also since in the majority of cases, water must be used continuously where there is no reser- voir for storing it. EVAPORATION. 33 The results of these experiments furnish important data on the quantitative values of evaporation losses, and show to what extent they may be avoided. They bring out with particular force the actual value of deep furrows, and of thorough cultiva- tion. In practice the evaporation losses will be less than in the experiments, due to the effect of the crop in shading the soil. On the other hand, there will be a loss of water by seepage through the subsoil, which loss does not appear in the case of tests in tanks. It is a difficult matter to ascertain the actual evaporation losses in practice, and to segregate the transpiration and evaporation losses proper. The total losses from transpiration and evapora- tion may be easily arrived at by growing crops in the tanks. For further description of the work the reader is referred to Professor Fortier's bulletin. In the Engineering News of Sept. 19, 1907, Professor Fortier gives the results of experiments made under his direction by Mr. Frank Adams to determine the influence of altitude on evaporation. The experiments were made on the Eastern slope of Mt. Whitney, California, in evaporation tanks. They show a steady decrease in evaporation, with increasing elevation. All the points when plotted, lie on a regular curve, with the excep- tion of the results at the summit, where the much greater expo- sure resulted in higher losses. The fact that the losses decreased with increase of altitude is, without doubt, due to the lower temperatures, at higher elevations, which more than compen- sated for the increased evaporation which would result from lower atmospheric pressures. The following table gives a sum- mary of the tests. EVAPORATION FROM WATER SURFACES, ON MT. WHITNEY. Station Elevation Weekly Evap- oration Soldiers Camp Feet 4,515 Inches 2 68 Junction South Fork and Lone Pine Creeks . Hunters Camp 7,125 8 370 2.04 1 75 Lone Pine Lake 10,000 1 63 Mexican Camp . . 12,000 1 60 Summit Mt Whitney 14 502 1 67 CHAPTER V. ACTUAL RESULTS OF IRRIGATION. ACCORDING to Professor King,* the following are the average irrigation requirements of land in various parts of the world. The results were given in acres irrigated per cubic foot per second, but have been calculated also in gallons per minute per acre. TABLE IX. IRRIGATION PRACTICE IN VARIOUS PARTS OF THE WORLD. Location Acres per cu. ft. per sec. Gal. per min. Av. gal. per min. North India 60 150 65 70 80 120 60 120 80 100 70 90 60 80 60 80 100 150 100 150 150 300 7 .5 to 3 .0 7 .0 to 6 .5 5 .6 to 3 .7 7 .5 to 3 .7 5 .6 to 4 .5 6 .4 to 5 .0 7 .5 to 5 .6 7 .5 to 5 .6 5 .6 to 3 .0 5 .6 to 3 .0 3 .0 to 1 .5 5.2 6.2 4.6 5.6 5.0 5.7 6.6 6.6 4.3 4.3 2.3 Italy Colorado Utah Montana Wyoming Idaho New Mexico . . Southern Arizona San Joaquin Valley Southern California Rice Irrigation .... 25 66 18.0 to 6.1 12.0 Professor King states that the amount of water required per irrigation to wet the land to a depth of 4 to 5 feet is from 2.5 inches to 4.5 inches for land fairly moist, and from 3.75 inches to 11 inches for land very dry. From 2 to 7 irrigations are required for wheat crops, the average usually being between 3 and 5. From experiments on earth tanks the following quanti- ties of water must be applied to produce crops of one ton, the water so applied making up the evaporation and the transpira- tion losses of the crops: * "Irrigation and Drainage," by F. H. King. 34 ACTUAL RESULTS OF IRRIGATION. 35 Crop. Acre-in. per ton Clover 5.1 Oats 4 .4 Karlry 4.1 Maize 2.4 The weight of one acre-inch of water is 113 tons. As these tests were conducted in inclosures, sheltered from wind, this may be regarded as the minimum quantity of water to grow the crops without allowing for either probable surface loss or under-drainage, and, in general, considerably greater amounts must be applied to raise a crop. According to Professor King's figures it takes from about 300 to 500 pounds of water to raise 1 pound of dry material and provide for the transpiration and evaporation losses. According to Newell, the average irrigation requirements are from 4 inches to 6 inches per month. This corresponds to a flow of from 2.5 to 3.8 gal. per min. per acre. In Southern California 1 cu. ft. per sec. will irrigate from 250 to 500 acres, a required flow of 1.8 to 0.9 gal. per min. per acre. Great variations will be found in the depth of water applied per irrigation in different places. Very shallow irrigations are generally undesirable, on account of the cost of application and the inefficiency of the same, due to the high percentage of evap- oration losses. On the other hand, too heavy irrigation results either in loss due to seepage of the water through the ground, or else in rendering the ground too wet, and hence unfit for the growth of plants. The suitable depth of irrigation will lie between these two extremes, and will depend, among other things, on the depth of soil, the pore space, and on the amount of moisture existing in the soil previous to irrigation. The frequency of irrigation should be governed by the fact that moisture in the belt of soil which the roots penetrate, should not fall to a point where the crop would begin to show signs of failure, but should be kept in quantity sufficient for plant growth. Many plants, when the crop is maturing, require more moisture than at other stages in their growth. While it is impossible to lay down hard and fast rules for irri- gation practice, owing to the diverse conditions encountered, the figures which follow give a summary of investigations con- ducted by the author and show the irrigation practice in 36 PRACTICAL IRRIGATION. various parts of the country. It is to be noted that the quantity " required flow " is not the actual rate of flow provided for, which is much greater, but is the rate which would be required were the required full water supply to run continuously during an irrigation season without rain. In many places the plants are far too large for the land they must irrigate, and in other cases the plants operate only during the daytime. Hence the required flow is much less than that actually provided in many places. In the figures to follow, two methods of obtaining averages are used: (1) Straight average, found by dividing the sum of the averages for the several farms by the number of farms; and (2) the weighted average, found by dividing the total results of all farms by the total size of the farms. These averages will be materially different, and the former will represent the average result of the individual farmer, while the latter represents the average result for the whole country. Irrigation water is usually applied in depths varying from 0.25 inch to 8 inches per irrigation. The former is usually inefficient, due to large percentage evaporation; and the latter, unless the ground has a deep subsoil, is apt to prove injurious from over-saturation. TABLE X. IRRIGATION PRACTICE IN SOUTHERN TEXAS. Crop Frequency of irrigation, days Irrigations per season Depth of water per irrigation, inches Depth of water per season, feet Required flow, Gal. per min. per acre Irrigation- factor, Per cent Alfalfa .... Cane . 38 13 9 5 5.1 3 6 5.72 2 50 2.5 5 2 93 18 Corn . 16 3 4 4 1 53 5 2 13 Cotton . . . Johnson grass Onions . . . Rice . . . Sorghum . . Truck 21 37 11 13 12 3 7 11 '4' 6 5.5 6.1 2.4 3^5 2.8 1.60 3.51 2.40 5.12 1 .86 1 .30 5.0 3.1 4.1 5.6 4.4 17 71 33 25 14 20 Average . . . 4.2 2.67 In general, it appears that efficient depths of irrigation per irrigation vary from 1 inch to 6 inches; the best depth depending ACTUAL RESULTS OF IRRIGATION. 37 on the soil, crop, climate, and cost of water, as well as the cost of applying it. In dry weather, truck is usually irrigated to a depth of from 1 to 2 inches, applied every 7 to 14 days. Table X is taken in part from investigations by the writer in Texas, and allows for ditch losses. It is based on straight averages. Owing to the widely varying conditions and practice of the different farms making up these tables, and to the method of obtaining averages, these results will not check exactly, and close results must not be expected. However, it may in general be stated as results that the average required flow per acre for grass or alfalfa is 2.8 gal. per min., and for rice is 12.3 gal. per min., while for other crops it is 4.9 gal. per min. These figures allow for loss in seepage in the distributing ditches. The actual required flow will vary with the nature of soil, climate, crop, and ditch loss. Considerable latitude in either direction must be allowed in applying these results to the various conditions in practice. TABLE XI. AVERAGE RETURNS FROM IRRIGATED CROPS IN SOUTHERN TEXAS. Crops Unit Crop Yields Assumed value per unit Value of crop per acre Alfalfa Ton 5.9 $15.00 $88.50 Corn Cotton Johnson grass Onions Bushel Bale Ton Pound 41 .0 .8 3.0 18612.0 .50 50.00 12.00 .02 20.50 40.00 36.00 372.24 Rice Pound 2140 .02 42.80 Sorghum Ton 4.0 TABLE XII. AVERAGE COSTS OF APPLYING IRRIGATION WATER IN SOUTHERN TEXAS. Cost of labor per day $0 .59 Labor per irrigation per acre, in days .42 Cost per irrigation per acre $0 .31 Labor of irrigation per acre for a year, in days 3 .07 Cost of irrigation per acre for a year $1 .96 To the cost of applying water must be added the cost of supply- ing water. 38 PRACTICAL IRRIGATION. The results from pumping plants are shown in Table XIII, giving total costs of pumping water per acre, using weighted averages. TABLE XIII. TOTAL COST PER ACRE OF PUMPING WATER IN SOUTHERN TEXAS. Fuel wood Rice irrigation $3 .34 Other crops 12 .04 Average . . . . 4 .73 Coal-burning Plants 11 .38 Average for Steam Plants 5 .91 Gasoline Plants 17 .46 Summary Rice irrigation 4 .87 Other crops 12.21 Total average 6 .13 Rice irrigation plants usually operate under low lift, and are of large size. These costs are greater than is usually expected, since the fixed expenses form from one-half to two-thirds of their total value. The results from the small truck farms in the humid East show that on an average the value of irrigation is over $200 an acre a year over the total cost thereof. The conditions encountered in humid countries are quite different from those in arid countries. Usually the only crops irrigated to any extent are truck, where the values of the crop are exceedingly high. Irrigation is of very great value, however, but owing to the small sizes of the farms and the methods of irrigation used, the cost is exceedingly high per unit quantity of water. The water is often distributed by piping at very high first costs and high cost of application. With pumping plants the loss in this piping involves pumping against a much higher head than would be necessary otherwise. Often city water is used. Tables XIV, XV, and XVI give average data on irrigation in the humid East, taken from several farms, where the conditions differed greatly. ACTUAL RESULTS OF IRRIGATION. 39 TABLE XIV. COST PER ACRE OF IRRIGATION IN THE EAST. System First cost Annual rust of fuel and operation or of water Fixed charges Total Annual depth inches City water .... $44 916 $9 $25 4 Pump plants . . . 74 9 1.5 24 8 COST OF WATER PER ACRE-FOOT. City water $48. Pump water (fuel and labor charges only) $13. TABLE XV. COST OF APPLICATION OF WATER BASED ON LABOR AT $1.50 PER DAY IN THE EAST. System Gal. per min. per unit stream Cost per acre-foot Cost per acre per irrigation Depth per irrigation, inches Furrow 24 $7.10 $0.75 1 .3 Hose 44 34.80 1 .80 .6 Single sprinkler Multiple sprinkler .... 4 4 34.40 16.10 1 .12 2.40 .3 1.8 The cost of application per acre-foot is proportional to the size stream handled per man. Single and multiple sprinklers require only a part of the time of one or more men, while hose requires their entire time, costing far higher per unit quantity of water applied. As indicating the possible field for irrigation of other crops in humid climates, Table XVI gives the average difference between crops in a good year, which irrigation would insure, and average crops in the East. The results of investigations in the East show for truck a required flow per acre of 3.3 gal. per min. and give the following averages: Frequency, 6 days. Irrigations per crop per season, 5. Depth per crop, 5.6 inches. The frequency given would be required without rainfall. The required flow is to be contrasted 40 PRACTICAL IRRIGATION. with 4.9 gal. per min. in Texas. The actual average flow provided in the East is 6.1 gal. per min. per acre, and as the plants are not usually operated at night, they are near the limit of irrigation. TABLE XVI. AVERAGE DIFFERENCE BETWEEN CROPS IN GOOD AND AVERAGE YEAR PER ACRE IN THE EAST. Crop Unit Av. yield per acre Yield in wet year Assumed price Increased . value in good year Corn bushel 48 64 $0.60 $14 .40 Wheat Rve u 20 20 28 25 .83 6.64 Oats (t 40 52 .37 4.44 Tobacco .... Timothy .... Clover .... pounds tons ti 1330 1 .6 1 .6 1700 2.1 2.1 .08 13.00 11 .00 29.60 6.50 5.50 In the East most of the distribution was by piping, resulting in no loss of water in the ditches ; also the climate was not so warm as in Texas. Taking these facts into consideration, the results show a fairly close agreement. As has been shown, efficient irrigation consists in obtaining the maximum benefit from a given expenditure; and in the selection of the system of irrigation, the various component parts of the cost, and the actual effect of the same, should be considered as a whole as well as separately, before coming to a decision. The relative costs of labor, fuel, and machinery have an impor- tant bearing on the system to be selected. No one element of cost should predominate to the detriment of the others. The length of irrigation season has a most important effect on the proper design. For a short season, with, say, an irrigation factor of from 10 to 20 per cent, generally the fixed charges will be greater than labor and operating charges. Where labor is high, it will not pay in general to adopt a system requir- ing excessive labor in the application of water to the land. The low irrigation factors, which are quite common, suggest strongly in many cases the advisability of minimizing the first cost. In many instances this may be effected by the use of a reservoir or earth tank of small capacity, say sufficient to hold ACTUAL ItlM-LTS OF IRRIGATION. 41 12 to 24 hours ' supply. The advantages of reservoirs for this purpose will be treated more fully farther on. Where labor is high it is very undesirable to incur a large expense for application of water. The irrigator should have, if possible, as large a stream as he can handle to advantage, and not waste his time distributing small quantities of water. It is usually very wasteful to attempt to distribute from a pump, a small stream of water direct to the land. Not only is the seepage loss very high, but also the expense for labor for applying the water is far higher than should be the case were a reservoir to be used. Note particularly the cost of application of water in the East. Only the exceedingly high profits of irrigation allow such extravagant methods, where the cost of irrigation is often higher than the total value of irrigated crops in the West. Truck irrigation in the East frequently saves an entire crop and may be worth as high as $1500 an acre a year. It often enables an additional crop to be grown in a season. From a number of plants in the East the average net return per acre per year from irrigated farms was $1030, $330 of which was due to irrigation, the total cost per acre of which lay between $30 and $100 per season. CHAPTER VI. DIFFERENT SOURCES OF WATER SUPPLY. THE primary consideration in an irrigation plant is the source of water supply : First, with reference to obtaining the right to use it; second, whether the supply is sufficient for the needs of the land, when water is required; and third, the method and cost of development. The prior rights of other parties and the available supply of water should be carefully considered before going to the expense of actual construction. If the water be purchased from a water company, the nature of the contract should be carefully examined, to determine whether the applicant is likely to receive the necessary water supply, and the probability of the possible failure of the same. Before diverting water from a stream the proper state officials should be seen. The state engineer, or board of irrigation, usually has control of such matters in the West. The Natural Flow of Streams. The most common and most important source of irrigation water-supply consists in utilizing the natural flow of streams, by diverting water therefrom. Where the diversion of water can be made cheaply by the use of short canals, this is generally the cheapest and best source of supply, provided there is sufficient water in the streams when required for irrigation. The flow of the rivers and streams, however, occurs at such periods that without storage much of the water will go to waste, and can- not be used on the land. Where the development has exceeded the water supply, the water in the streams will often fail to furnish an adequate supply when most needed for irrigation. In these cases the land must get along as best it can without water. Where the rights are determined by priority, the last comer is the first to suffer. Where the rights are vested in a canal com- e* 42 DIFFERENT SOURCES OF WATER SUPPLY. 43 pany, the water is usually pro-rated to the various users. The flow of the streams and the probable variation of the same with the period of year, as well as the difference between different years, should be given careful consideration, with reference to the period of the irrigation season. Where the watershed is rugged and steep, the run-off of the rain water is usually very rapid. On the other hand, where the reverse conditions are found, the run-off will be much slower, much of the water finding its way gradually through the soil into the river bed, appearing in the form of springs, which tend to equalize the flow. The melting snows, from which many of the rivers are fed, serve as a valuable source of water storage, preventing the rapid run-off which would otherwise occur. Of necessity a very large part of the supply of rivers used for irrigation will run to waste, unless the water be stored. This has led to the construction of many large reservoirs, and the important government work undertaken by the Reclamation Service will vastly increase the available irrigable area. It is the intention of the government to deliver these dams and irrigating systems to the settlers, who are to pay for the work within ten years, after which they will be owned and controlled by themselves as a company. The construction of large reser- voirs involving great sums of money usually calls for too heavy an expenditure to be undertaken by private individuals. Per- haps the most useful feature of the use of reservoirs in irrigation work is the fact that they render available water which could not otherwise be obtained; and indeed they are not governed by the previous cost of water, but rather ultimately by the actual value of the water. This will be discussed more fully farther on. Reservoirs. Reservoirs may be divided into two classes, natural and artificial. In the first class are included reservoirs where the greater part of the retaining banks are formed by nature; while, on the other hand, artificial reservoirs are those in which prac- tically all the banks are constructed artificially. 44 PRACTICAL IRRIGATION. Natural Reservoirs. Natural Reservoirs are used for the storage of river or rain water, not only for its various economic uses, but also in some cases to equalize the flow of rivers and to minimize the danger of floods. Preliminary considerations: 1. Before undertaking the construction of a reservoir a careful consideration should be given to the source and extent of water supply, drainage area, rainfall and distribution, the nature of the ground with reference to seepage and the annual and monthly evaporation. Among other considerations the nature of the soil with reference to salt and alkali should be taken into account, in order that the stored water may not be contaminated by dissolving the salts in the soil. A considera- tion of the losses by evaporation shows the importance of considerable average depth of water in the reservoir, as well as the poor policy of shallow construction. Efficiency, which is the ratio of the amount of water taken out to that which is put into the reservoir, should be determined beforehand as closely as possible. The efficiencies of reservoirs vary widely, depending largely on the climate, rainfall, and mean depth. In a good reservoir seepage losses should be small, the principal loss being from evaporation. The seepage losses in a reservoir will, in gene- ral, increase with increasing depths of water. Annual evapora- tion losses usually lie between 3 and 7 feet, in the arid West. Evaporation tests are usually conducted by immersing a vessel filled with water in the center of a tank or reservoir. In order to protect against waves, the immersed vessel is surrounded by a bulkhead. Shielding the pan from the wind which is necessary, however will introduce an error in the results, as it is a well- known fact that evaporation is considerably higher on windy than on still days, owing to the more intimate contact between water and air. The surface area and the mean depth of a reservoir, as well as protection of the same from winds, have an important bearing on reservoir efficiency. Elements of depreciation: Reservoirs which are located in the bed of a water course are liable to damage from floods of special violence, and they are also subject to depreciation by the filling of the reservoir with DIFFERENT SOURCES OF WATER SUPPLY. 45 sediment carried down by the streams. Possible damage, owing to this, depends largely on the average annual amount of solid matter carried by the streams. A reservoir of small capacity with reference to the annual flow of the stream, if in the bed of the stream, will be damaged by the deposit of sediment to a larger relative extent than a larger reservoir under similar conditions. In many reservoirs arrangements nave been made for flushing out the sediment, through scour- ing galleries. Cost of Stored Water. In estimating the value of water delivered by a reservoir, due attention should be given to the condition of the case, par- ticularly to the element of depreciation. Let L = cost of land for reservoir, i = per cent interest and taxes, R = cost of reservoir construction, P = per cent fixed charges of reservoir, A = annual cost of attendance, W = cost of water supplied to reservoir, Y = acre-feet of water supplied to reservoir. E = reservoir efficiency. Cost of stored water W + Li + RP + A = X. X Cost of stored water per acre-foot = -r Value of Location. Usually the location of a natural reservoir is not a matter of choice, as it is dependent mainly upon the lay of the land. However, if it is possible to choose locations, the three following cases should be considered: 1. Reservoir in bed of stream. Advantages: (a) It is not necessary to use a canal, or to construct means of diversion of river water. (6) The entire supply of the river flows into the reservoir. Disadvantages: (a) The reservoir being located in the bed of the stream, ample spillway must be provided. (6) Unless the dam is made of masonry or other material 46 PRACTICAL IRRIGATION. capable of serving as a spillway, it must be constructed to a sufficient height above the spillway to provide necessary safety. (c) Possible damage by flood water. (d) Sedimentation of reservoir. (e) Owing to conditions encountered, it may be necessary to build expensive masonry dams. 2. Reservoirs near the source of supply not located directly in the river channel. Advantages: (a) Reservoirs not subject to damage from ex- cessive floods. Water supplied may be more easily controlled. (6) Owing to this they allow of cheaper construction than reservoirs of the first class, since banks need not be built to such excessive height, and a smaller spillway will suffice. (c) Sand traps may be provided in the supply ditch, thus keeping part of the sediment from entering the reservoir. Disadvantages: (a) Diverting works and a canal must be built. (b) In the event of a considerable rise in the stream from which the water supply is derived, water which in the first case could be stored were the reservoir not full, might in the second case be lost, owing to inability of the canal to carry the same. 3. Reservoirs located near the point of use of water. Reservoirs of this description would have the advantage over reservoirs of the last-mentioned type, that a smaller capacity would serve the purpose, since it would be unnecessary to provide reservoir capacity to supply seepage loss of ditches necessary for class No. 2. On the other hand, they would necessitate the construction of larger ditches for conveying the water than would be necessary in case 2, since, aside from other considera- tions, the ditches in this case must carry sufficient water to allow for reservoir seepage and evaporation, and it would be advisable to provide ditches of sufficient size to carry water, much of which might otherwise be lost. In many parts of the country no natural reservoir sites are available. In this event, to store water requires the construction of an artificial storage reservoir. Except for very small capacities, the only practical form of reservoir consists of an earth tank or reservoir, usually con- structed by throwing up banks to surround the same. Artificial reservoirs perform a most useful service in many cases, and DIFFERENT SOURCES OF WATER SUPPLY. 47 investigations show that they may be extended in many places to the storage of large quantities of water on a commercially profitable basis, indeed at an average cost less than the average cost of natural reservoirs. Artificial Reservoirs. Artificial reservoirs may be divided into two classes: (1) Those of small capacity, and (2) those of large capacity. A reservoir of small capacity is one that will store the discharge of a well pump or small stream for from half a day to a week, whereas reservoirs of large capacity will serve to store water for a considerable period. Small-capacity reservoirs are used par- ticularly as a storage for pumped water or artesian-well water, and will serve the following purposes: (1) They will permit a continuous 24-hour operation of pumping plants or flow of wells without night irrigation, storing water during the night and irrigating with it during the day. (2) They will allow the use of irrigation heads larger than the rate of the supply to the reservoir, thus reducing the percentage of seepage losses in the distributing ditches. (3) The quantity of water which one man is capable of handling may be more easily supplied in this manner, thus reducing the cost of labor for irrigation. (4) They allow the operation of a pumping plant under full capacity and hence under conditions of highest efficiency at all times. Therefore, they may be a source of considerable saving in both fuel and labor charges. For example, if it is desired to irrigate a certain field, and only one-half the flow of the pump can be used to advantage, this water can be supplied either from what is stored in the reservoir without starting up the pump, or else the pump can be operated at its full capacity, delivering the water that is required to irrigate the field, and storing the remainder in the reservoir. (5) A small plant with reservoir may be installed to operate continuously in place of the installation of a larger plant operating only a portion of the time, thus cutting down the first cost of the plant, but increasing the cost of labor, in case it should be necessary to have an attendant always on hand. Small gasoline plants require very little attendance, and would benefit particularly in this event. This decrease in the capacity of the pump may have a very 48 PRACTICAL IRRIGATION. important bearing on the fuel consumption in case the supply is derived from a well, due to the decreased head against which the water must be elevated. This head may be expressed by the formula H = A + BQ + CQ 2 (see page 86). Take, for instance, a case which came within the observation of the writer, where water was pumped from a well, the water level being 2 feet below the level of the ground. The water was hardly throttled at all in the ground itself, practically all the head against which the pump had to operate being caused by friction in the well casing. As the plant was run the pump had to operate against a head of 50 feet. The pump station was run only during the day. Providing the station had been operated all the day, delivering one-half the previous quantity of water, it would have required practically a head one-fourth of that which it did require, thus necessitating a power plant only one-eighth of the size, and reducing very materially both the first cost of the plant and the running expenses, although the cost of labor would have been increased. The saving in fuel, however, would have far more than compensated for the additional labor, not to mention the saving in fixed expenses. Considerations which can be urged against reservoir construc- tion are: (1) First cost. (2) The land occupied. (3) Addi- tional height to which water must be raised in order to fill the reservoir. (4) Seepage and evaporation. If the material for the construction of the reservoir is at all suitable, proper con- struction should largely eliminate seepage. With small reser- voirs, seepage and evaporation should be of little importance. While all stages of reservoirs of intermediate capacity may be built, yet in general the most useful sizes would be reservoirs holding from 12 hours to a week's pump or well capacity, or else reservoirs of large size retaining the water for long periods except where the supply is pumped by windmills, and hence has to depend on an uncertain source of power. Canals as Storage Basins. It is frequently necessary to supply from pumping plants a flow of water considerably less than the normal supply of the pumps. In cases of this nature the storage of water pumped is a very useful feature. In some cases canals have been made D1F1-'KIIK\'T SOrnCES OF WATER SUPPLY. 49 sufficiently large to answer this purpose. However, generally speaking, the use of a canal for a storage basin is not to be looked on with favor, for the following reasons: (1) In proportion to the volume stored it presents a large surface for seepage. (2) In com- parison with a reservoir proper, the bank is much longer than the corresponding reservoir bank, and usually not so strongly built. A break in the canal bank where a large amount of water is stored is liable to do considerable damage to adjoining land. (3) In comparison with reservoirs of equal storage capacity, the cost of the canal banks would be excessive as compared with cost of reservoir bank. (4) To avoid unnecessary waste of water and loss of time in reaching the lands to be irrigated, it is desirable that canals should not have too large capacity. In places where canals are used as storage basins, the construc- tion is usually of such a nature that in order to raise^the water to sufficient height to irrigate certain sections of the field the canal must be filled completely. Where storage basins are desired it would be decidedly preferable to construct reservoirs for such purpose, and to build the canals of sufficient capacity to convey the water to the land without velocity sufficiently great to erode the banks. They should, however, be built with banks sufficiently strong, which should be at a safe elevation above high- water mark in the canal. Any amount of trouble and annoyance in irrigation is caused by flimsily constructed canal banks when the water is run dangerously close to the top and is constantly breaking through. Underground Supply. Perhaps the greatest number of irrigation plants derive their water from the underground water supply by means of wells. The underground supply has the very important advantage that it can be tapped usually at the point of use, thus doing away with the necessity of long conduits with their inevitable losses and high cost. The earth is composed of various strata which usually form planes more or less continuous over large areas. These strata may be classified with reference to the resistance they offer to the passage of water, some of them transmitting water readily, while others are quite impervious. The underground waters 50- PRACTICAL IRRIGATION. flow through certain strata or channels. It is the exception, however, when they flow in open subterranean channels, by far the greatest part of the flow being through porous strata of sand, sandstone, or gravel. The resistance to flow through the water strata is so great that the movement is usually very gradual, and the flow, instead of being confined in a small channel, often fills the entire stratum. The formation of the earth is such that the ground is divided into water strata which are more or less independent of each other, depending on the imperviousness of the intervening strata. Each water stratum receives the seepage into the catchment area of the stratum, or from direct connection with or leakage from other strata. Fig. 2 illustrates the general principle of water distribution into various strata, the figure representing a profile and section of the land; the Figs. 2 and 3. Water Distribution in Strata. various water strata, a, 6, and c, being fed respectively from the surface seepage from A, B, and C alone, provided the inter- vening strata are impervious. If the flow of water in a water- bearing stratum is sufficiently great just to saturate the entire stratum at any point, then if this stratum be tapped by a well the water will rise in the well to the level of the top of the stratum. Should the flow increase, water will be under pres- sure in the stratum, and will rise in the well to a higher level. Should the pressure be sufficiently great to raise the water above the ground level, the well, if an opening be made in its casing at the ground, will give forth an artesian flow. It is, of course, not necessary to have a flow through the ground strata for the water level to be raised to a sufficient height to be under pressure, as is seen in Fig. 3. The water-bearing strata of the earth form natural reservoirs of vast extent. Sandy soils will contain from 25 to 40 per cent of their total volume in storage capacity, and in consideration of their enormous extent it is evident that the underground storage reservoirs are of far greater extent than all the surface DIFFERENT SOURCES OF WATER SUPPLY. 51 rosorvoirs which will ever be constructed. The underground water comes directly from seepage through the surface of the soil. The rainfall and seepage from rivers and canals and from irrigated land are the main sources of its supply. Unlike the surface storage reservoirs, the greater part of the underground water is in continual motion, but the retarding effect of the soil is so great that it forms a strong tendency to equalize the flow. The seepage through the soil forms an important source of supply of most rivers, reappearing in the form of springs, and in some places coming out under the ocean. The rate of movement of underground waters varies directly with the head or pressure causing the flow in a given distance. The nature of the soil has also a most important effect on the flow. The more open the soil, the greater the flow; while the finer the grains of the soil, the less the flow. Gravel transmits water readily, coarse sand fairly well, fine sand slowly, while sand with clay in it offers a great resistance to the flow of water. In limestone formations the water is often found in caverns in the rock, frequently flowing as a subterranean river. In general, the more free the nature of the water-bearing strata, the greater is the likelihood of obtaining large supplies therefrom, while from poor strata the supply is likely to be much restricted. The source and extent of the water which goes to make up the underground supply should be carefully considered before attempting extensive development. The seepage into a stratum is dependent on the catchment area of that stratum, the rainfall, evaporation and surface run-off of the land. Return seepage from irrigated lands may form an important addition to the underground supply, as is evidenced by the return seepage to the North Platte River from the irrigated lands near by. This is described at length in bulletin No. 157 of the Office of Experi- ment Stations of the United States Department of Agriculture. The subject of the flow of underground water is treated at length by Professor Slichter in investigations of the United States Geological Survey. The resistance of a porous medium to the flow of water is dependent on the size of grains and on their arrangement. The larger the grains, the less the resistance. If, however, large and small grains be mixed together, the small grains will fill the spaces between the large grains, causing the resistance to increase much beyond that of sand having grains 52 PRACTICAL IRRIGATION. Si l-o b , OQ > iCOCOiOCNtOiOtNcOQO CC'-H i rH CM :88 CMcotOtOOOOtOOO T^O5OOr-lOOOl>COOCOOOOQia*OOOO O O O O ~i IO *O >O lO CO -66i-Hl>-OCOpO i-HCO COO I ^ 5 i 1 L~ "u ? ~ -"' * * ^ ^ ^ ^ ?1 ^T O OO C5 i-H CO S GO 2 M S 5 N H S S8 iU5p'OO l Op^OpOOjOOiCOOOOO -H <* r 2TH-H 2 , T gl ~R ~~ 2TS * gl *' WELLS. 97 If H is small with reference to T, we may write approximately, r H r Iog 10 - == - TT Iog 10 . If there is no flow in the ground, then, obviously, the depres- sion of the well will gradually increase in time, the rate of increase rapidly decreasing with the time. With no inflow whatever, the well will derive its supply from the storage in the ground, and as, generally, this storage is of very large extent, it may be a matter of quite a period before the depression is felt over any distance. The well supply will come from the volume included between the original ground- water plane, and the plane of depression of the ground water. All the water of saturation cannot be obtained, but assuming even 20 per cent of this volume mentioned is available, it shows that the storage capacity of the soil is of very great importance. Slichter rates wells at what he calls their specific capacity; i.e.j the flow per foot the well water is lowered, assuming that the rate of discharge bears a constant ratio to the lowering of the water. This is true where the lost head is lost mainly in porous media, but will not hold where the loss of head in the pipe and casing is considerable, since in the latter case the lost head varies with the square of the velocity. Slichter accord- ingly gives a formula based on the proportionality of head and discharge for determining the flow, from the time the well takes to fill up when pumping ceases. The formula considers the well flowing only into the net volume of the casing, deduct- ing plunger rods, etc. A = area in sq. ft. of well casing, minus the area of rods and pump casing, etc. q = Specific capacity or flow in gal. per min. per ft. water is lowered. H = Total head well is lowered by pump. h = Instantaneous depression in feet. t = Time in minutes since pump stopped. Thus at any instant the flow = qh and the quantity discharged in time dt = qh dt = 7.5 Adh. 98 PRACTICAL IRRIGATION. Hence, integrating between h H and h = h, 17.25 A fh Hence, q - - Iog 10 - Measuring i and h, and H and A being known, q is deter- mined. This is an ingenious method of arriving at the flow, but it requires to be accurate, that 1. Practically all lost head must be in the porous medium. 2. The water must not be lowered in well beyond the top of the water stratum, from which it is derived. 3. There must be no other place for the returning water to flow, except into the well. In some cases it is possible that there might be some quantity of water flowing into a space where it would displace or compress air, due to the rise in pressure. 4. The well must not affect neighboring wells, or be affected thereby, should they discharge at the same time. Methods and Cost of Boring Wells. Unlike the case of machinery for pumping, it is impossible to give even an approximate figure on the cost of boring or sink- ing wells, unless the nature of the strata encountered be known. The best known form of well is the dug well, where the sides, if necessary, are curbed with wood or masonry, to prevent caving of the earth. These wells are usually comparatively shallow. The drive well consists of pipe, on the end section of which is a strainer. The extreme end of the pipe is covered by a taper point which facilitates driving the pipe into the ground. These wells are usually not deep, on account of the difficulty of driving the pipe. The form of well most extensively used in irrigation is the bored 'well. A circular hole is bored in the ground, by various means, and, if the strata encountered are liable to cave, it is cased off by iron casing. Bored wells render practical the matter of sinking to great depths. }VKLLS. 99 The sizes of bored wells vary usually from 4 inches to 14 inches in diameter. It is the usual practice in boring wells not to case the hole till necessary. The following methods of boring are in use: 1. Hand boring, by means of a long-stem auger, the debris being removed by a sand pump. This is difficult if rock strata or boulders are encountered. 2. Drop drill. The material in the hole is smashed up by a machine-driven drop drill, and then removed by a sand pump. 3. Hydraulic sinking. (a) The bitt, which revolves, is run by a hollow pipestem provided with a swivel joint on the top, through which water is forced down the well, coming up outside the pipe carrying the debris with it. This method is quite rapid in a soft soil, frequently one shift making 40 feet of 6-inch hole in a day. When passing through strata that might cave, heavy clay water is used to wall up the strata temporarily. In sinking 6-inch wells in Southern Texas the pumps supply- ing water for this purpose give a flow of 60 gal. per min. under 35 to 40 pounds pressure, and about 1500 gal. per day were required to compensate for the seepage losses. (6) The well casing is revolved and the water which is forced down it carries the debris up outside of it. This is suit- able only for very soft soils, since the water does the cutting. (c) Similar to (6), except that the casing is provided on the bottom edge with a revolving cutter which makes the hole. This is capable of working in quite hard formations. If it is necessary to case the well, the bottom of the casing may be left open or provided with a strainer. If left open (open-bottom well), it should stop at the top of the water stratum and should not project into it. Well boring is usually done at a price of so much a foot for boring, plus the cost of the casing. The price per foot depends on the size of the hole, and it is usually constant up to an even number of hundred feet between 200 and 500. After that depth is passed, the cost usually increases at a given increase per foot for the next hundred feet, twice the increase for the following hundred, and so on. For example, if the cost is SI .00 per foot up to 400 feet, it will be, say, $1.10 from 400 to 500, and $1.20 100 PRACTICAL IRRIGATION. from 500 to 600, etc. Where well boring is an established busi- ness, 6-inch wells can usually be sunk for from 50 cents to $1.00 per foot, for the first 200 feet, if the ground is at all favorable. With cheap labor, hydraulic rigs and a soft ground, wells 1000 feet deep can be bored at a cost between $1.00 and 50 cents for a 6-inch well, while 12-inch wells in fairly hard strata from 800 to 1000 feet deep will cost from $6.00 to $12.00 a foot for boring, the cost depending on the nature of the strata. In California 12-inch wells are commonly sunk in soft material for 50 cents per foot for the first hundred feet, and 75 cents per foot for the second hundred, $1.00 per foot for the third hundred feet, and so on, the price being for labor only. Stovepipe casing is commonly used in 24-inch or 30-inch joints. In shallow wells single galvanized casing is used and is put on one joint at a time and riveted up when set in place. For deep wells, however, double casing is used, with inner and outer joints, lapping, and the casing often instead of being riveted is simply dented in with a pick at the joints. This casing is much cheaper than screw-joint casing and, unless the latter is made with flush joints, presents less resistance in forcing it into the ground. It will not stand as much driving, however, as screw casing, and usually is forced down by hydraulic jacks or weighted levers. Many wells are ruined by improper casing. The artesian water is limited in quantity, and where the wells are put down without casing or are improperly cased, strata of unequal hydrostatic pressure may be thrown together, resulting in a loss of water from the higher pressure stratum, which may be seriously injurious to other wells in the same field. It is a matter of public policy to pass laws governing the sinking of wells, and the proper casing thereof, to prevent injury to neighboring wells and to endeavor to conserve the artesian supply as far as possible. Wells should be throttled when not in use, but many wells are so poorly cased that the mere addi- tional pressure caused by throttling will open up a new passage for the water on the outside of the casing and, in some instances, the water will appear at the ground, outside the casing, and in other instances it will force its way into other strata, enlarging the leakage path, so that when the well is again turned on the yield is diminished. WKLLS. 101 In testing wells, especially where there is a deep- well pump in the well, it is frequently very difficult to measure the distance to water in the well. A method devised by the author which has given excellent results is to insert a small pipe down the well to water. By blowing down the upper end of the pipe it is possible to tell by the percussion of the bubbles exactly when the pipe enters the water. In the case of an artesian well delivering water without pumping at the ground level, the flow is fixed. With a pumped well the flow may be varied by increasing or decreasing the depth from which the water is drawn. Wells may be conveniently rated at the first cost in gallons per minute output. All wells will be subject to a certain annual expense, which will represent the cost of the total amount of water furnished by them. In calculations, this will be taken at 12 per cent of the first cost of all wells, composed of 7 per cent interest and taxes, and 5 per cent depreciation and repairs, the latter to include all possible costs in connection with the wells, such as sand pumping, etc., as well as depreciation due to deterioration of casing and falling off of supply, owing to increas- ing number of neighboring wells. The annual cost of a well is independent of the amount of water obtained from it. The following figures were obtained from results of a large number of wells in Texas, the straight average representing the mean value per plant, and the weighted average taking the mean value of all the plants considered as a unit : COSTS OF WELLS AND OF WELL WATER IN SOUTHERN TEXAS. Artesian well Pumped well First Cost : Average cost per gal. per min. (straight average) . $21 .62 $6.13 Average cost per gal. per min. (weighted average) . 8.30 2.75 Average cost per acre irrigated (straight average) . 71 .00 15.25 Average cost per acre irrigated (weighted average) . Annual cost per acre irrigated (straight average) . . 57.77 8.63 14.79 *Average cost per acre-foot output (straight average) 2.86 ... * This is the cost of water actually used in irrigation. The irrigation factor was 20 per cent. The wide difference between the straight and weighted average is due to the high cost of some of the small wells. Pumped 102 PRACTICAL IRRIGATION. wells, in general, are much more shallow than artesian wells, and hence cost far less. It is a common belief that artesian well water costs nothing. This is, of course, erroneous, since even if the repairs, renewals and possible falling off of water supply be disregarded, the interest on the investment still runs on. Of course, it is highly desirable to obtain water without the operating expense of a pumping plant. Still the first cost may be so high that a pump- ing plant operating under low head may easily be a better investment than a deep artesian well. Table L and curves in Fig. 51 show the relation between the irrigation factor, the cost per gallon per minute of artesian wells, and the cost of water per acre-foot, based on 12 per cent annual expense. One gallon per minute will deliver 1.612 acre-feet per year, and, at a cost of $10 per gal. per min. and 100 per cent irrigation factor, will cost 75 cents per acre-foot. CHAPTER IX. PUMPS AND PUMPING MACHINERY. THK power required in pumping water is usually reckoned in horsepower. One horsepower will lift 3960 gals. 1 ft. per min., or 8.33 cu. ft. 1 ft. per sec. Hence, to find the actual horse- power for a given lift, multiply the feet vertical lift by the flow in gallons per minute, and divide by 3960, or else multiply the feet lift by the flow in cubic feet per second and divide by 8.83. The result is the net horsepower required for actual and useful work. In order to force water through suction and discharge piping, and around bends, etc., requires the expenditure of additional energy which must be furnished by the pump. The energy so required is equivalent to that consumed in raising the water to an additional height, which added height would be required to over- come all pipe losses. This added height is known as the head lost in the piping, and may be calculated when the sizes of piping, etc., are known. Hence, to find the power which the pump must furnish, the lost head in feet must be added to the vertical lift to find the total head against which the pump must operate. Multiplying this head by the flow, and dividing by the appro- priate constant, as given above, gives the power which must be furnished by the pump, known as the pump output. The engine must deliver to the pump sufficient power to supply this output, and also to supply losses of power in the pump. Hence, to obtain the required power of engine, the pump output should be divided by the pump efficiency. The latter will range, as a rule, from 30 per cent to 80 per cent, depending on the size and type of pump and on the conditions of operation. Fifty per cent is usually a safe figure. On this basis multiply head in feet by the gallons per minute flow, and divide by 2000, to get the horsepower required to drive the pump. Table XXVI will facilitate calcu- lations of this sort. 103 104 PRACTICAL IRRIGATION. _ 00 O O O T-I OOOOOiOOi-iC^O) F=H f ^^.,._,___^. O i^C^COTt^^OOT^CO^I>'pC^TfO^T^OC ; lI>COOC)^O &_, '.5 2 * t * H ow^T^icoico^TH^oi^^cooooo^c^ooooooooot^-t^t^-r^-t^-t^t^ o IT UPS AND PUMPING MACHINERY. 105 Column 1 gives ft. lift X cu. ft. per sec. Column 2 gives ft. lift X gal. per min. Column 3 gives water horsepower at 100 per cent efficiency. Columns 4 to 16 give engine horsepower at various efficiencies. To lift 1 acre-foot of water 1 foot requires the expenditure of 1.37 water horsepo\ver-hours. This may be conveniently used in calculation of total quantities of energy required in the irrigation of land. To illustrate the use of Table IX, what horsepower engine must be provided to lift 700 gaL per min. a height of 70 feet, the friction and other losses in piping being 20 feet, with a pump of 60 per cent efficiency. The total head is 90 ft., and 90 X 700 = 63,000. Looking under the second column, 6330 gal. per min. X ft. require at 60 per cent efficiency 2.67 horsepower. Hence, required power of the engine = 26.6 horse- power. In consideration of the lift of the pump there is often some confusion with regard to the exact mean- ing of this term. Distinction must be made between the lift of the pump and the Fig. 25. Diagram of Pump Lift. total head against which the pump must operate. The head is equal to the lift, plus all the losses in friction, entrance to pipes, curves, and discharge from the outlet of the piping. The ratio of the lift to the head we shall call the efficiency of the piping. To illustrate this, in Fig. 25, let S = suction lift P = pressure lift L = total lift = 8 + P + G H 8 = suction head H p = pressure head H = total head 106 PRACTICAL IRRIGATION. F 8 = sum of the losses of head occurring in suction pipe and in entrance to the same. F p = loss of head in discharge pipe, due to friction, etc. G s = gauge reading of suction pipe, the suction head being considered positive. G p = reading of pressure gauge. C = vertical distance from suction-gauge tap to center of pressure gauge. V 8 = velocity of flow in feet per second in suction pipe at the point of suction-gauge tap. V p = velocity in feet per second in pipe at pressure- gauge tap. V = velocity in feet per second at discharge end of pipe. (V Y Then, H a = S + F 8 + ~^- = G 8 , U 1 ^ 1 * 7) 1 ^-v 73 i v - / ^^ x-^ 2^ 2^ H 8 + H p - - = 11 = All pressures are in feet of water. The efficiency of piping TT = -=- In the case shown, which represents pumping from a L well or from a sump, the meaning of the term " lift " is perfectly obvious, representing a total difference of elevation between the level of water in the sump of well and the level of the dis- charge water. However, in the event of pumping from a well when the suction pipe is directly attached to the well casing, the term " lift " is indefinite, though the total head may be defined as before, as well as the suction and discharge heads. In selecting a pump, the head against which it must operate, and not the lift, is of course to be considered. If the pipes where the pressure and suction gauges respectively are tapped PUMPS AM) Pl'MPINO MACHINERY. 107 are of the same diameter, V, =-- V p , hence the total head is equal to the sum of the gauge readings + C. In making efficiency tests of a pump care should be taken not to charge losses in suction or discharge pipes or in the velocity of discharge, against the pump itself. These losses belong directly to the piping and have no connection whatever with the pump efficiency. If the total lift, L, be known, the pipe efficiency may be calculated from the data, or else may be measured by the aid of gauges, as shown in the figure. It should be noted that, assuming a negative pressure in the suction pipe, no water will stand in the pipe leading to the suction gauge, hence the gauge reading refers to the level of the suction pipe where tapped. With reference to the pressure-pipe gauge tap, however, such is not the case, the pressure-gauge pipe being filled with water. If the pressure pipe should be of any appreciable length, care should be taken to see that water fills the pipe up to the gauge, in order that air trapped in the pipe may not leave the actual level of water in the gauge pipe in doubt. Should there be a positive pressure in the suction pipe, similar pre- cautions should be taken for the suction-gauge piping. In this event, C would represent the vertical difference between gauge centers instead of the difference of level between center of pressure gauge and the point of suction tap. Pressure or suction gauges should be located on a straight section of the pipe, as near the pump as possible, but where the water is moving at a uniform velocity. In case the head against which the pump operates is low, particular attention should be given to the details already mentioned, since, if disregarded, the same might lead to very large errors in the results. In making accurate tests of low-head pumps, some form of liquid gauge would usually be preferable to commercial gauges commonly used. In reckon- ing the losses in the pipe, the friction losses, loss of head at entrance to the suction pipes, and the velocity head of the discharge pipe, as well as losses due to sudden bends of pipe, or sudden change in the section thereof, must be computed, in event of the lift alone being known. To facilitate computation of this kind, Table XXVII shows the losses in friction, as well as the velocity heads for various sized pipes delivering water at different rates. The velocity head in feet is equal to the square of the veloc- ity at the point in question divided by 2 g, g equaling 32.2. The 108 PRACTICAL IRRIGATION. loss of head at the entrance to a pipe projecting into a body of water is equal to one-half the velocity head at that point and the loss at the end of the pipe, where the same discharges, equals the velocity head at that point. TABLE XXVII. VELOCITY AND FRICTION HEAD TABLES IN NEW CAST IRON PIPES. (Based on Cox's Formula, see page 228, Appendix.) Vplm* Velocity 2-inch pipe 3-inch pipe 4-inch pipe V ClOC- ity head Friction Friction Friction Flow loss per Flow loss per Flow loss per 1,000 ft. 1,000ft. 1,000 ft. Ft. per sec. Ft. Gal. per min. Ft. Gal. per min. Ft. Gal. per mm. Ft. 1 .02 10 2.9 22 1.9 39 1 .5 2 .06 20 10.0 44 6.7 78 5.0 3 .14 29 20.4 66 13.6 117 10.2 4 .25 39 34.1 88 22.8 157 17.1 5 .39 49 51.3 110 34.1 196 25.6 6 .56 59 71.8 132 47.8 235 35.8 7 .76 69 95.5 154 63.6 274 47.7 8 .99 78 122 176 81 .6 313 61.2 9 1 .26 88 153 198 102 352 76.5 10 1 .55 98 187 221 124 392 93.5 11 1.88 108 224 243 149 431 112 12 2.24 117 264 265 176 470 132 13 2.63 127 308 287 205 509 154 14 3.05 137 355 309 236 549 177 15 3.50 147 405 331 270 588 202 16 3.97 156 460 353 306 627 230 17 4.50 166 517 375 344 666 258 5-inch pipe 6-inch pipe 7-inch pipe 1 .02 61 1.2 88 1.0 120 0.84 2 .06 122 4.0 176 3.3 240 2.9 3 .14 183 8.2 265 6.8 360 5.8 4 .25 245 13.7 353 11 .4 480 9.8 5 .39 306 20.5 441 17.1 600 14.6 6 .56 367 28.7 530 23.9 720 20.5 7 .76 429 38.1 628 31.7 840 27.2 8 .99 489 49.0 706 40.8 960 35.0 9 1.26 551 61.1 794 51 .0 1 080 43.7 10 1.55 612 74.8 883 62.2 1 200 53 .3 11 1 .88 673 89.5 970 75.7 1320 64.0 12 2.24 734 106 1,059 88.2 1440 75.6 13 2.63 795 123 1,146 103 1560 88.0 14 3.05 857 142 1,235 118 1680 102 15 3 .50 918 162 1,322 135 1800 116 16 3.97 979 184 1,411 153 1 920 131 17 4 50 1,040 206 1,500 172 2040 148 * A XI) PUMPING MACHINERY. 109 TABLE XXVII Continued. IfAlxVrtffw 8-inch pipe 9-inch pipe 10-inch pipe Veloc- ity V eiocitv head Friction Friction Friction Flow loss per Flow loss per Flow loss per 1,000 ft. 1,000 ft. 1,000 ft. I-'-. I..T sec. Ft. Gal. per miu. Ft. Gal. per lain. Ft. Gal. per min. Ft. 1 .02 157 .73 198 0.65 245 0.58 2 .06 313 2.5 397 2.2 490 2.00 3 .14 470 5.1 595 4.5 735 4.17 4 .25 628 8.6 794 7.6 980 6.8 5 .39 784 12.8 993 11.4 1,225 10.2 6 .56 941 17.9 1,190 15.9 1,470 14.6 7 .76 ,095 23.8 1,389 21.2 1,715 19.1 8 .99 ,252 30.6 1,587 27.2 1,960 24.5 9 1.26 ,409 38.3 1,786 34.0 2,205 30.6 10 1.55 ,567 46.7 1,984 41.5 2,450 37.3 11 1 .88 ,724 56.0 2,182 49.7 2,695 44.8 12 2.24 ,881 66.1 2,380 58.7 2,940 52.8 13 2.63 2,037 77.0 2,579 68.4 3,185 61.6 14 3.05 2,195 88.8 2,777 78.9 3,430 71.0 15 3.50 2,350 101 2,976 90.2 3,675 81.1 16 3.97 2,507 115 3,175 102 3,920 91.8 17 4.50 2,664 129 3,373 115 4,165 103 11-inch pipe 12-inch pipe 13-in. pipe 1 .02 296 0.53 353 0.49 414 0.45 2 .06 592 1.82 707 1.67 828 1.54 3 .14 889 3.71 1,160 3.40 1,221 3.14 4 .25 1,185 6.2 1,413 5.7 1,655 5.27 5 .39 1,482 9.3 1,766 8.5 2,068 7.9 6 .56 1,777 13.0 2,120 11.9 2,482 11.0 7 .76 2,075 17.3 2,472 15.9 2,896 14.7 8 .99 2,350 22.2 2,816 20.4 3,310 18.8 9 1.26 2,665 27.8 3,180 25.5 3,720 23.5 10 1.55 2,964 33.9 3,530 31.1 4,140 28.7 11 1 .88 3,260 40.7 3,870 37.2 4,550 34.4 12 2.24 3,560 48.0 4,240 44.0 4,970 40.6 13 2.63 3,850 56.0 4,590 51 .3 5,380 47.3 14 3.05 4,150 64.6 4,950 59.1 5,800 54.6 15 3.50 4,450 73.7 5,300 67.6 6,210 62.3 16 3.97 4,740 83.5 5,650 76.5 6,630 70.6 17 4.50 5,040 94.0 6,000 86.2 7,040 79.5 110 PRACTICAL IRRIGATION. TABLE XXVII Continued. 14-inch pipe " 15-inch pipe 16-inch pipe Veloc- Velocity ity head. Friction Friction Friction Flow loss per Flow loss per Flow loss per 1,000 ft. 1,000 ft. 1,000 ft. Ft. per Ft. Gal. per Ft. Gal. per Ft. Gal. per Ft. sec. min. min. min. 1 .02 480 0.42 552 0.39 628 0.36 2 .06 960 1 .43 1,103 1 .33 1,255 1.25 3 .14 1,440 2.92 1,655 2.72 1,882 2.55 4 .25 1,920 4.88 2,207 4.56 2,510 4.27 5 .39 2,400 7.3 2,760 6.8 3,140 6.4 6 .56 2,880 10.2 3,130 9.6 3,760 9.0 7 .76 3,360 13.6 3,310 12.7 4,390 11.9 8 .99 3,840 17.5 3,860 16.3 5,020 15.3 9 1 .26 4,320 21.8 4,410 20.4 5,650 19.1 10 1.55 4,800 26.6 5,520 24.9 6,280 23.3 11 1.88 5,280 31.9 6,170 29.8 6,900 28.0 12 2.24 5,760 37.7 6,620 35.2 7,530 33.0 13 2.63 6,240 44.0 7,180 41 .0 8,160 38.4 14 3.05 6,720 50.7 7,730 47.3 8,790 44.3 15 3.50 7,200 57.9 8,280 54.1 9,420 50.7 16 3.97 7,680 65.6 8,840 61.1 10,030 57.3 17 4.50 8,170 73.9 9,390 68.9 10,680 64.7 18-inch pipe 20-inch pipe 22-inch pipe 1 .02 794 0.32 980 0.29 1,187 0.26 2 .06 1,588 1 .11 1,960 1.00 2,375 0.91 3 .14 2,381 2.27 2,940 2.04 3,560 1.85 4 .25 3,170 3.80 3,920 3.42 4,750 3.11 5 .39 3,970 5.7 4,900 5.1 5,940 4.64 6 .56 4,760 8.0 5,880 7.2 7,120 6.5 7 .76 5,550 .10.6 6,860 9.5 8,310 8.7 8 .99 6,350 13.6 7,840 12.2 9,500 11 .1 9 1 .26 7,150 17.0 8,820 15.3 10,680 13.9 10 1 .55 7,940 20.7 9,800 18.7 11,870 17.0 11 1.88 8,730 24.8 10,780 22.4 13,060 20.3 12 2.24 9,530 29.4 11,760 26.4 14,240 24.0 13 2.63 10,310 34.2 12,740 30.7 15,420 28.0 14 3.05 11,100 39.4 13,720 35.5 16,610 32.3 15 3.50 11,900 45.0 14,700 40.5 17,700 36.8 16 3.97 12,700 51.0 15,680 45.9 18,990 41.7 17 4.50 13,490 57.5 16,660 51.7 20,180 47.0 PUMPS AND PUMPING MACHINERY. Ill TABLE XXVII Continued. 24-inch pipe *26-inch pipe 28-inch pipe Ifcjr head Friction Friction Friction Flow Flow loss per Flow loss per 1,000 ft. 1,000 ft. 1,000 ft. Ft. per Ft. Gal. per Ft. Gal. per Ft. Gal. per Ft. sec. min. mm. miu. 1 .02 1,413 0.24 1,657 0.22 1,921 0.21 2 .06 2,827 0.83 3,310 0.77 3,840 0.72 3 .14 4,240 1.70 4,970 1.57 5,770 1 .46 4 .25 5,650 2.85 6,630 2.63 7,690 2.44 5 .39 7,070 4.26 8,290 3.94 9,610 3.65 6 .56 8,480 6.0 9,950 5.5 11,520 5.1 7 .76 9,900 8.0 11,600 7.3 13,440 6.8 8 .99 11,300 10.2 13,250 9.3 15,360 8.7 9 1 .26 12,710 12.7 14,910 11.8 17,280 10.9 10 1 .55 14,130 15.5 16,570 14.4 19,210 13.3 11 1.88 15,550 18.6 18,230 17.2 21,150 16.0 12 2.24 16,960 22.0 19,880 20.3 23,050 18.9 13 2.63 18,380 25.6 21,550 23.7 24,970 22.0 14 3.05 19,790 29.5 23,200 27.3 26,900 25.3 15 3.50 21,200 33.8 24,870 31.2 28,820 28.9 16 3.97 22,620 38.2 26,530 35.3 31,700 32.7 17 4.50 24,030 43.0 28,180 39.3 32,700 36.9 30-inch pipe 36-inch pipe 42-inch pipe 1 .02 2,204 0.19 3,180 0.16 4,310 0.14 2 .06 4,410 0.67 6,360 0.56 8,630 0.48 3 .14 6,620 1.36 9,540 1.13 12,94p 0.97 4 .25 8,830 2.28 12,700 1 .90 17,280 1.63 5 .39 11,020 3.41 15,870 2.84 21,580 2.43 6 .56 13,230 4.78 19,050 3.98 25,900 3.41 7 .76 15,430 6.4 22,230 5.3 30,200 4.54 8 .99 17,650 8.2 25,400 6.8 34,500 5.8 9 1.26 19,850 10.2 28,600 8.5 38,900 7.3 10 1.55 22,040 12.4 31,800 10.4 43,100 8.9 11 1.88 24,260 14.9 35,000 12.4 47,500 10.6 12 2.24 26,470 17.6 38,100 14.7 51,800 12.6 13 2.63 28,670 20.5 41,300 17.1 56,100 14.7 14 3.05 30,900 23.7 44,500 19.7 60,500 16.9 15 3.50 33,100 27.0 47,700 22.5 64,800 19.3 16 3.97 35,300 30.5 50,800 25.5 69,100 21.8 17 4.50 37,500 34.4 54,000 28.7 73,400 24.6 112 PRACTICAL IRRIGATION. TABLE XXVII Concluded. 48-inch pipe 60-inch pipe "Vcloc- Velocity ity head Friction Friction Flow loss per Flow loss per 1 1,000ft. 1,000 ft. Ft. per sec. Ft. Gal. per min. Ft. Gal. per min. Ft. 1 .02 5,640 0.12 8,830 0.10 2 .06 11,290 0.42 17,650 0.33 3 .14 161,940 0.85 26,480 0.68 4 .25 22,600 1.43 35,300 1.14 5 .39 28,230 2.13 44,100 1 .70 6 .56 33,900 2.98 53,000 2.39 7 .76 39,500 3.98 62,800 3.18 8 .99 45,200 5.1 70,600 4.08 9 1 .26 50,800 6.4 79,400 5.1 10 1 .55 56,400 7.8 88,300 6.2 11 1.88 62,100 9.3 97,000 7.5 12 2.24 67,800 11.0 105,900 8.8 13 2.63 73,400 12.8 114,600 10.3 14 3.05 79,100 14.8 123,500 11 .8 15 3.50 84,700 16.9 132,200 13.5 16 3.97 90,400 19.1 141,100 15.3 17 4.50 96,000 21.5 150,000 17.2 With low-head plants the possible losses in both the entrance to the suction piping and in the velocity head lost in the dis- charge should be carefully considered, as they may easily add very materially to the power required for pumping. These losses can be obviated with such simple and cheap means that there seems little reason for their existence. The head lost in entrance to the suction pipe can be easily avoided by belling the pipe at the entrance. A bell-shaped entrance is preferable to a cone-shaped, though the latter will often be a decided improvement over the straight pipe. With reference to the discharge pipe, a taper joint with gradually enlarging section will overcome almost entirely the loss of head at the discharge. Since the loss of discharge head varies with the fourth power of the diameter, by increasing the diameter 42 per cent, the discharge loss can be reduced to one- fourth of its previous value, and by doubling the diameter, can be reduced to one-sixteenth of its previous value. It is no uncommon sight to find discharge pipes in irrigation plants throwing the water into the air several feet above the PUMPS AND PUMPING MACHINERY. 113 level of the discharged water, owing to the high velocity heads. It is obvious to even a casual observer that this represents a considerable loss of power. Of course it is unnecessary in many cases to go to the trouble of endeavoring to avoid these losses, provided they are not of sufficient importance to warrant so doing. From Table XXVII, one can judge whether it would pay to take the precautions necessary to obviate entrance and discharge losses. Of recent years there has been a decided increase in the use of irrigation pumping stations. This has been brought about mainly owing to three reasons: 1. Decreased cost of energy. 2. Improvements in pumps. 3. Settlement of lands where irrigation is a commercial necessity. Much land now arid can be successfully irrigated by pump water, but the results of an undertaking of this nature are dependent on so many circumstances that a proper selec- tion of apparatus and understanding of conditions will often tip the balance from failure to success. One important element of success hi many cases is the reduc- tion of the labor required for the operation of the stations. Labor often forms a large proportion of the cost of pumping, and any means by which it can be reduced is of importance. Skilled labor should be used only where necessary, as much of the work of operation may be performed by unskilled workmen provided there be a proper organization and superintendence. Having determined the desired capacity of pump station as previously outlined, the next consideration is the available amount of water, and the depth from which it must be raised, as well as the possible variations in the same, due to dry years, change of season, and the other plants in the vicinity. If the irrigation water is derived from wells, most of this information can be obtained only by experiment, though often an approxi- mate idea can be obtained from wells near by. Before going to the expense of installing a well pumping station, wells should first be tested for capacity. The motive power to be adopted depends on the location and capacity of the plant, the required hours of operation, the cost of labor and fuel. If a number of plants are to be operated in the same vicinity, it may often pay to put in a central electric 114 PRACTICAL IRRIGATION. station, and to distribute energy therefrom to the various plants, rather than to have each station provided with its own source of energy. The distance to which energy may be economically transmitted by electricity, even in small quantities, is surpris- ingly large.* As an illustration, estimates on various plans for the operation of 120-stock water pump stations with a maximum probable demand of 90 horsepower showed that, although the first cost was higher, still electrical operation of the plant figured out cheaper than any other plan. It involved the use of 120 miles of pole line and of a complete telephone system. Each station was to contain a motor, small centrifugal pump, telephone, auto- matic float, operating a switch for starting and stopping the motor, earth reservoir, and float valves for letting water into the watering troughs. The plans also involved a brick power house for generating electricity. The estimated cost of com- plete installation was $60,000, or about $500 per station. While not the cheapest system to install, yet, in this instance, the operation was far cheaper than by any other system. It would have been cheaper to have installed gasoline engines, but the operating expense, mainly of attendance, would have been too high to have justified such an installation. For small individual pumping plants, requiring a few horse- power, a gasoline engine is frequently the best form of motive power. The oil cups on the engine and pump should be made of ample size, so that the apparatus can run for hours without attendance, without danger of accident. For fuel, some of the better grades of distillate can be used instead of gasoline, thus making a decided saving in cost. Distillate is made from crude oil, and consists of the more volatile parts of the oil, which are driven off by heat and then condensed. Local conditions, of course, largely govern the kind of fuel to be used, but the cheapest fuel is not necessarily the most economical. The expense of firing and of handling the fuel may cut a large figure in the actual cost of power, and it may be found that oil, even if more expensive than other kinds of fuel, may reduce the operating expenses of the plant sufficiently to justify its adop- tion. This, of course, applies to stations of some size, as with * See paper by the author, Transactions Pacific Coast Transmission Association, 1902. PUMPS AND PUMPING MACHINERY. 115 smaller stations, which can be easily operated by one man, there is no saving in the matter of attendance. There is such a wide difference between the values of different grades of coal that the price per ton should by no means deter- mine the kind to be used. Some of the poor grades of coal have not one-third of the steaming value of the better grades, and they reduce considerably the power available from the boilers, as well as increasing largely the work of the firemen. A good coal will contain as high as 14,000 British thermal units per pound, while some grades of poor coal have less than 5000 British thermal units per pound. Among the various kinds of pumps and methods of pumping in most common use in irrigation pumping, may be mentioned the following: 1. Deep well pumps. 2. Power plunger pumps. 3. Pumping engines. 4. Direct-acting steam pumps. 5. Pulsometer. 6. Air lift. 7. Centrifugal pump. 8. Hydraulic ram. 1. In pumping from wells where the lift is high, the distance to ground water considerable, the flow of water is small, and the water is free from grit or sand, the deep- well pump is usually to be preferred. It has the advantage that it may be conven- iently located inside a well, thus dispensing with digging a pit. 2. Power plunger pumps may be used to advantage where the lift is high, and the pump may be located so that it is not in danger of being submerged, and there is no danger of water going below the suction limit. 3. Pumping engines may be used to advantage where the quantity of water is large and the lift high. They are capable of giving excellent results for economy, but their field is usually for city water works, rather than for irrigation plants. 4. Direct-acting steam pumps, while possessing the element of simplicity, still consume a large amount of steam, and are quite inefficient in fuel consumption. Their low first cost is usually offset by increased boiler capacity. Compounding 116 PRACTICAL IRRIGATION. these pumps results in a considerable saving in steam, but is an additional expense. 5. The pulsometer, while simple in construction, is subject to the same objections as direct-acting pumps, being a heavy steam consumer. 6. The air lift, while not an efficient method of pumping, has still many advantages for certain kinds of deep-well pump- ing. It enables water to be drawn from a considerable depth, and is capable of handling a large quantity of water to better advantage than can be done by a deep-well pump. It has all its working parts above the well, easily accessible, and is not troubled by sand and grit in the well getting into the valves. If several wells in the same vicinity were to be pumped by com- pressed air, it might pay to install a central air station and to pipe the air to the different wells. To get any sort of efficiency out of an air lift requires a submergence of the air pipe at least equal to the lift, and preferably twice as great. 7. For pumping plants of any size, the centrifugal pump is generally the most desirable pump to install. It has the com- bination of cheapness, simplicity, and a minimum of working parts. It has no valves to give trouble, and can handle water with grit without getting out of order, though, of course, the wear is increased in that case. The improvements in the centrifugal pump have contributed largely to the increase in irrigation pumping. Good results as regards efficiency may be obtained by the proper use of these pumps as now constructed by the leading manufacturers. Unfortunately, the laws of centrifugal pumps are little understood by many who should be better informed on this subject, and the result has been that many of them, as installed, are not working at anything like their highest efficiency. The proper speed at which to run a centrifugal pump varies with the square root of the head, the latter including both friction and other losses of head and the actual lift. The efficient capacity of a centrifugal pump, when operating at its efficient speed, for a given lift, varies directly with the speed, and is not constant. Most centrifugal pump manufacturers make the serious mistake of rating their pumps at a fixed capacity. A centrifugal pump can be rated efficiently at a given capacity only when the head, and hence the speed too, is fixed. PUMPS AND PUMPING MACHINERY. 117 8. In the hydraulic ram the energy of a considerable quantity of water falling a moderate distance is made to force part of the water to an elevation. The ram requires very little attention, and in some instances is quite economical. It is usually used in small installations. Cost of Engines, Motors, and Pumps. The cost of pumping machinery will vary with the grade of machinery and with the location of the plant, owing to freight charges. It is often desirable to figure the approximate cost of machinery without going too much into detail, and the fol- lowing figures will give approximate prices. TABLE XXVIII. COST OF GASOLINE ENGINES. Brake horsepower Cost Cost per horsepower 1 $125 $125 2 225 112 3 300 100 4 370 92 5 420 82 10 640 64 20 1000 50 50 2200 44 100 3500 35 Actual prices may vary from 10 to 20 per cent from these costs. Steam engines are usually rated by indicated horsepower; i.e., the power developed in the engine cylinder. To get the actual available horsepower output (brake horsepower) , the mechanical losses of friction and windage must be deducted from the indicated horsepower. The mechanical efficiency of engines will usually lie between 85 and 92 per cent. Simple engines will cost from $8 to $15 per indicated horsepower, and compound engines from $12 to $25. Horizontal tubular boilers will cost from $6 to $13 per boiler horsepower, and water tube boilers from $14 to $18 per boiler horsepower. The setting for boilers will cost from $3 to $6 per boiler horse- power exclusive of foundations. Pumps and heaters will cost per 118 PRACTICAL IRRIGATION. boiler horsepower from $2 for noncondensing up to $5 for con- densing plants. To these costs must be added the cost of stock, foundations, pumps and building, as well as the cost of installing the plant. As a rule, irrigation pumping plants of small or moderate size employ cheap engines and boilers, and hence the cost of the plants will be nearer the lower than the higher limits given below. In general, the use of compound engines and of condensers will considerably increase the cost of plant, though allowing smaller boilers and more economical use of fuel. The following figures will give an approximate idea of the cost of steam plants per indicated horsepower, the higher limits representing high-grade machinery not usually employed. TABLE XXVIIIa. COST OF STEAM PLANTS. Size plant indicated horsepower 5. 10. 25. 50. 100. 200. 500. Total cost of steam plant per indicated horsepower From $95 75 55 60 50 47 42 To 180 160 108 120 100 90 80 To these costs must be added the cost of hydraulic develop- ment and the cost of irrigation pumps. In general, irrigation pumping stations will cost from $60 to $150 per brake horsepower for plants of 15 horsepower and over, depending on the size of plant, type of machinery, and cost of water development (i.e., wells, pipe line, or reservoir cost). The approximate cost of polyphase induction motors for motors of 500 volts and under, is given in the following table. The actual prices may vary from 10 to 20 per cent from these figures. The price of a motor will depend on the speed, and will increase rapidly with decrease of speed. Centrifugal pumps of the same nominal size, as built by different makers, have different capacities. It has been pointed out that it is wrong to rate centrifugal pumps at a constant output independent of speed, and that the proper output varies directly as the speed suitable for the head. Of course pumps if run at a sufficient speed will deliver flows dependent on the heads against which they operate, but then their rating should be only at or near their highest efficiency. PUMPS AND PUMPING MACHINERY. 119 TABLE XXVIII 6. COST OF POLYPHASE 6o-CYCLE MOTORS FOR VOLTAGES FROM 100 TO 500. Horsepower Cost Cost per hp. Speed r.p.m. 1 $55 $55.00 1800 2 80 40.00 1800 5 100 20.00 1800 10 240 24.00 1200 20 375 18.75 1200 30 425 14.17 1200 50 600 12.00 900 75 900 12.00 720 100 1080 10.80 720 150 1500 10.00 580 200 1830 9.15 580 300 2650 8.83 580 TABLE XXIX. THE APPROXIMATE COSTS AND CAPACITIES UNDER 40 FOOT HEAD OF CENTRIFUGAL PUMPS. No. Pump Gal. per min. Cost 4 . 450 196 6 900 150 8 1600 220 10 2500 300 12 4000 380 The cost of pumping water may be regarded as composed of three different parts: 1. Expense for fuel or energy. This cost is generally directly proportional to the quantity of water pumped. 2. Labor expense for operation of the plant. This cost is generally proportional to the hours of operation. However, it is in reality proportional to the length of irrigation season, since generally labor for operation of pumps cannot be engaged by the day for the mere time when the pumps are in operation, but must be paid for the entire irrigation season. In some farms, however, the engineer will do other work around the farm when the pumps are shut down for any reason. LIBP t I K.1 . _ 120 PRACTICAL IRRIGATION. 3. The remaining expenses, while not strictly of such a nature, may be conveniently regarded under the head of fixed expense bearing annually a certain proportion to the total cost of the plant. The fixed expense may be segregated under the following heads : (a) Interest and taxes. (6) Depreciation. (c) Repairs and renewals. (d) Supplies for operation. (a) Interest and taxes are independent of time or hours of operation. Seven per cent of first cost may be taken as a fair value for the same. (&) Depreciation. The value of depreciation is in part dependent on the time of operation. Without care machinery will depreciate as fast from disuse due to rusting, as it will from wear. The annual depreciation of most irrigation plants is largely due to lack of care and insufficient housing of machinery, which is often left exposed to the elements. Depreciation will vary from about 2 per cent to 30 per cent per year, depending on the use or abuse of machinery; but 8 to 10 per cent should cover depreciation in most cases, if reasonable attention be given to it. (c) Repairs and renewals will vary from 2 per cent to 20 per cent, and 2 per cent should cover supplies for operation. With moderate care the following figures should give fair values of fixed expenses. Per cent Interest and taxes 7 Depreciation 8 Repairs and renewals 3 Supplies 2 20 If conditions are exceptionally favorable, this figure may be as low as 14 per cent. These figures apply to the pumping plant proper. The total fixed expenses for pipe lines, wells, and artificial reservoirs is much less and approximately may be taken at 12 per cent. PUMPS AND PUMPING MACHINERY. 121 Hence it is evident that the cost of pumping a unit quantity of water is composed of the following three parts: 1. Fuel expense, directly proportional to the quantities pumped. 2. Labor expense, directly proportional to length of irri- gation season, depending in part on the quantity pumped. 3. Fixed expense, independent of the output of the plant. The proper design of an irrigation pumping plant in general consists in providing a plant which will deliver most cheaply a given quantity of water in a given time. To design a plant intelligently requires a knowledge of the three component expenses as well as the manner in which they may be varied by altering the details of design. In general, means should be taken to cut down any com- ponent of expense which is likely to become unduly large. To illustrate, if the fuel expense is too high, a more efficient engine should be used, such as a compound instead of a simple, and a condensing instead of noncondensing. Should the labor cost be unduly high, it may pay to install a larger plant and run it for shorter hours, or to put in a plant which is simpler and does not require a high degree of skill to operate it. TABLE XXX. FIRST COST OF PLANTS IN SOUTHERN TEXAS, PER WATER HORSEPOWER. Gasoline plants Steam plants Water horsepower Pump plant. Total Water horsepower Pump plant Total 0.15 $2300 $2900 1 $900 $1100 0.3 1700 2160 2 675 810 0.4 1300 1800 3 525 680 0.5 1100 1530 4 425 525 0.75 800 1070 5 355 450 1 .00 650 870 7.5 240 320 1.5 530 730 10.0 160 220 2.0 450 605 15.0 128 155 3.0 350 500 20.0 110 132 4.0 310 420 25.0 99 117 5.0 275 370 35.0 85 99 10.0 205 265 50.0 75 85 15.0 150 190 65.0 72 80 122 PRACTICAL IRRIGATION. TABLE XXXI. FUEL CONSUMPTION PER WATER HORSEPOWER PER HOUR. Steam plants Gasoline plants Water horsepower Wood, 0.001 cord Lb. Coal, 10,000 British thermal units Water horsepower Gal. Cost at 16 cents per gal. 1 42 31 .2 1 .3 20.8 2 33 30 .3 1 .0 16.0 3 26 29 .4 .84 13.4 4 21 29 .5 .71 11 .3 5 18 28 .75 .55 8.8 7.5 13 27 1 .0 .43 6.9 10 HJ 25 1 .5 .34 5.4 15 11 22 2.0 .33 5.3 20 10J 20 3.0 .33 5.3 25 10 17 5.0 .32 5.1 35 9* 14 . . 50 8^ 12 . . . 75 7 11 . . . ... . 100 5 10 . . . . . . 150 4 . . . The average total cost for gasoline plants, of gasoline, labor, and fixed ex- penses was 22 cents per water horsepower. TABLE XXXII. COST OF OPERATION OF STEAM PLANTS PER WATER HORSEPOWER-HOUR. Water horsepower Fuel cost, Cents Labor cost, Cents Fixed charges, Cents Total cost, Cents Corresponding irrigation factors 1 5.7 5.0 2 4.7 3.2 191 27.0 9 3 4.0 2.4 13.6 20.0 10 4 3.5 1.8 9.7 15.0 11 5 3.1 1.4 8.0 12.5 12 7.5 2.60 .97 7.0 10.6 9 10 2.30 .75 6.1 9.2 7 15 1 .92 .54 4.3 6.6 8 20 1.67 .44 2.9 5.0 10 25 1.46 .42 2.0 3.9 13 35 1 .18 .42 1.1 2.6 19 50 .96 .42 1 .1 2.5 17 75 .81 .41 1.2 2.4 15 100 .76 .40 1.3 2.4 150 .74 .38 1 .3 2.4 PUMPS AND PUMPING MACHINERY. 123 If the fixed expenses are too high, a cheaper type of plant should be installed, or else a smaller plant can be put in and run for longer hours. The three sources of expense are interdependent, and no system will in general be laid out properly which does not allow and consider their quantitative effect. It should be remembered that high-grade machinery requires in general a more expensive man to operate it than a simpler and less expensive type. To illustrate the actual results in practical work, tables XXX, XXXI, and XXXII have been compiled from irrigation pump- ing plants in Southern Texas: The results are the averages of curves plotted by data from over 100 plants, and represent, it is true, results of various types of plants. An efficient pumping plant should better the results obtained. All results are based on the actual water horsepower output of the pump, taking thus no direct account of pump efficiency other than as it affects the cost of plant. The following are the existing conditions: Fuel. Coal is generally of poor quality, varying from 4800 to 10,300 British thermal units per pound, averaging perhaps 8000. Good coal goes up to 14,000. Cost of coal from SI to $2. 25, averaging about $1.58 per ton. Wood, usually mesquit, about 3200 pounds per cord. 4500 British thermal units per pound. Cost, 60 cents to $2.50 per cord; average, $1.46. Gasoline, 16 cents per gallon. Labor, mostly Mexican, very ordinary class. Wages, 38 cents to $2.50 per day. Average, about 65 cents for engineers. Fixed expenses for pump plant proper engines, boilers, house and pump are taken at 20 per cent per year; and for the rest of plant, such as pipes, reservoirs, wells, etc., at 12 per cent. The unit-water liorsepower-hour is dependent on what the plant is actually doing, and not on what it might do. Engines, except for the largest plants, are simple, noncondensing. It is to be noted that fuel costs are low, labor is very low, but the fixed expenses are unduly high. This is due to having too low an irrigation factor. In other words, the plants are too large for the areas watered, and it would pay to take means to 124 PRACTICAL IRRIGATION. avoid making so large a first investment with its consequent fixed charges. With gasoline plants of small capacity no attendance is needed. In spite of the high cost of gasoline, small plants of this nature are more economical to run than steam plants, owing partly to the fact that they do not require constant watching. The effect of the irrigation factor on the cost per unit quantity of water may be seen in the following case : Supposing a plant delivers 2 cu. ft. per sec. at a total cost per 24-hour day of $8 for labor and fuel, that the fixed expenses are H $ cost per acre-fl ft ti c \ \ s ^ K N Ss 20 6O 6C perc ent irrigation factor Fig. 26. $2 per day, Table XXXIII and curve in Fig. 26 show the cost of delivering water per acre-foot for various irrigation factors. Cost of water per acre-foot = $2.02 for fuel and labor. TABLE XXXIII. Irrigation factor Fixed expense per acre-ft. Total cost per acre-ft. 5 $10 .10 $12 .12 10 5.05 7.07 15 3.37 5.59 20 2.53 4.55 25 2.02 4.04 30 1.64 3.71 40 1.27 3.29 50 1.01 3.03 75 .67 2.69 100 .50 2.52 Figs. 27 and 28 show tests of two of the New Orleans drainage pumps, for handling the city rain water. The units are of the PUMPS AND PUMPING MACHINERY. 125 direct-connected vertical type, and consist of a centrifugal pump, driven by a synchronous motor. The curves are all plotted with rate of discharge in cubic feet per second as abscissae. JO JOO Tn cu.ff'Joer' sec. Fig. 27. Performance of New Orleans Drainage Pumping Plants a.t Constant Speed. The discharge curve shows relation between flow and lift. The kilowatt-input curve shows the relation between the flow and the kilowatts-input to the motor. The kilowatt-output curve shows /80 disch'arye in tu.f _ Fig. 28. Performance of New Orleans Drainage Pumping Plants at Constant Speed. the relation between the actual effective kilowatts output of the plant in lifting water, and the flow. The efficiency curve shows the relation between the ratio of power output of water and power input to motor, and the flow. In other words, it shows the total efficiency of the plant. To illustrate the method of calculation of irrigation pumping plants, assume the following data for a plant for 300 acres: 126 PRACTICAL IRRIGATION. 1. Depth per irrigation at the land, 3 inches. 2. Frequency of irrigation, once every 10 days. 3. Irrigations per year (no rain), 9. 4. Rainfall during irrigation season, 3 inches. 5. Pumping plant to operate 12 hours per day. 6. Loss in ditches, 20 per cent of supply. 7. Water raised by pumping, 30 feet. 8. 12-inch suction and discharge. 9. 200 feet 12-inch pipe in both. 10. Centrifugal pump, 60 per cent efficiency. Required (a) Capacity pump gallons per minute. (6) Depth of water per season. (c) Depth of irrigation water to be pumped per season. (d) Irrigation factor. (e) Total head. (/) Horsepower to drive pump. (g) Horsepower hours per acre per year. (a) Capacity of pump. By Table II, required flow = 5.7 gal. per min. Since the pump operates 12 hours per day, pump 300 X 5.7 X 2 capacity = - - = 4280 gal. per mm. O.o (b) Depth of water per season 3 X 9 = 27 inches. Subtracting 3 inches rainfall leaves 24 inches irrigation to be applied per year. (c) Depth of irrigation water to be pumped per season. 24 The pump supply = = 30 inches, allowing for ditch loss. 0.8 80 (d) Irrigation factor = ^ = 11 per cent. obo X 2 (e) Flow of 4280 gal. per min. by Table XXVII. Makes loss of 200 X 45 *- 1000 = 9.0 feet in pipe. Loss at entrance 1.2 " Loss at discharge 2.3 " Total 1275 " Static head -. . . . 30.0 " Total head . 42.5 " PUMPS AND PUMPING MACHINERY. 127 (/) Power to drive the pump. 42.5 X 4280 gal. per min. = 181,900. Hence at 60 per cent efficiency by Table XXVI the power required = 77 horsepower. (g) Horsepower-hours output of engine per acre per year = T!|- X 1.37 X^-X 42.5 = 242. 12 6 If a steam plant be installed with simple noncondensing engine it will cost approximately $4800. Figuring 7 per cent interest and taxes, 11 per cent depreciation, repairs, and renewals, 2 per cent operating expense, 20 per cent fixed expenses = $960 per year, or $3.20 per acre. If one man operates the plant for the season of 90 days, receiving $3 per day, the operating expense is $270, or 90 cents per acre per year. If the fuel be coal of 12,000 British thermal units per pound, say the plant will require 4 pounds per horsepower-hour. If this costs $6.00 per short ton, the cost per horsepower-hour = 1.2 cents, or $2.90 per acre per year. Summarizing: Fuel cost .... $2.90 per acre per year. Labor cost 90 per acre per year. Fixed expenses. . . 3 . 20 per acre per year. Total 7.00 per acre per year. CHAPTER X. IRRIGATION NEAR BAKERSFIELD. To illustrate the actual results of a large irrigation pumping system, the following account is given, of irrigation near Bakers- field. One of the largest irrigated districts of California is in the vicinity of the city of Bakersfield, which is situated about forty miles north of the southern end of the San Joaquin Valley, where the Coast Range and Sierra Nevada mountains unite. The rainfall in the surrounding country is perhaps lower than in any other habitable portion of the state, being on an average about 4 inches. The rain nearly all falls in the winter and early spring, the remainder of the year being dry. Owing to the lack of moisture, much of the surrounding country for the greater portion of the time is barren of vegetation, with the exception of sage brush. The Kern River, which emerges from the mountains about sixteen miles from Bakersfield, is the only watercourse of importance in the country for many miles. After the river leaves the mountains it flows for several miles through the foothills, finally entering the valley about four miles above Bakersfield (see Fig. 29). The river follows the main slope of the country, which is to the west, and somewhat to the north, into Buena Vista Lake, an artificial reservoir which has been constructed at the west side of the valley by building several miles of levee to retain the waters. The natural dis- charge of this lake is towards the north, to Tulare Lake. The bed of the river, like most of the surrounding country, is of a sandy nature. The flow of the river is usually greatest in May and June, when it frequently reaches 4000 cubic feet per second part of the time, and it has been known to discharge 11,000 cubic feet per second at the time of a high flood. The water is diverted by several large canals, the largest of which is the Calloway, which is about 35 miles long, and has a capacity of about 900 cubic feet per second. 128 IRRIGATION NEAR BAKERSFIELD. 129 This canal is 80 feet wide on the base, 120 feet on top, and 5 feet deep. The water which is not utilized in irrigation is stored in Buena Vista Lake, which is about six miles square, with a storage depth of 10 feet. The cost of the reservoir was $150,000 (Schuyler), and the capacity 170,000 acre-feet or 88 cents per acre-foot, an exceedingly cheap cost for reservoir con- struction. From the reservoir large areas of land are irrigated. In good years there is an abundance of water in the reservoir, but in times of protracted drought it is entirely without water, and the bottom is absolutely dry. The Kern County Land Company, and Miller & Lux, practically control the entire water supply, as well as the land, in this part of the country. These two companies are primarily engaged in the cattle business, and one of the main objects of the agricultural development is to furnish food for the cattle. Although other branches of agri- culture have been developed, the greatest part of the irrigated land is planted in alfalfa. The various canals owned or controlled by the Kern County Land Company are all separate canal companies, each of which has its own organization; but they are all under a common management, The Kern River Canal Company, which controls the division of water between the different canals, as well as the distribution to the various owners. When water is scarce, instead of each canal receiving its proportion of water, it is all turned into a few canals at a time, and pro-rated according to the water rights on those canals. When the farmers on these canals have finished irrigating, the water is turned into other canals, and in this manner the central management effects as fair a distribution of water as is possible, and avoids undue seepage losses by having the water in as small a length of canal as possible. In dry seasons the river water is exceedingly low, and con- sequently it was desirable, if possible, to install an auxiliary system to obtain water when the river supply ran low. The only available supply was the underground water. There were excellent indications of the possibility of obtaining a large supply of water from pumped wells. The ground water level over much of the country near Bakersfield stood from 3 to 25 feet below the surface of the ground, the distance depending 130 PRACTICAL IRRIGATION. on the location and the season. Cheap electric energy was available for the operation of pumps, as the Power Develop- ment Company had its lines already in Bakersfield. This company obtained its energy from a hydro-electric plant situated at the place where the Kern River emerges from the mountains. A fall of 220 feet in the river is obtained by conducting the water through a tunnel 1.75 miles long. Three-phase electric energy is transmitted 17 miles to Bakersfield, under 10,000 volts pressure. The first pumping station which was installed consisted of a horizontal centrifugal pump belted to an induction motor. The pump was connected to several wells, and was set some distance below the ground in order to be as near the water level as pos- sible. Owing to the variation in the level of the ground water, there were objections to this method of operation, since, if the pump were set too low, the ground water in some seasons might rise until it covered the pulley. This- would necessitate pump- ing out the pit in which the pump was placed, by another pump, in order to lower the water sufficiently to put the belt on. After the pump once started, it would, of course, keep the pit dry, and then there would be no danger unless it should stop while the attendant was absent. If the pump were set up high enough to be out of danger from the rising ground water, it would be so high that it would exhaust the wells, and suck air when the ground water went down in dry seasons. This was due to the fact that it was desirable to obtain as much water as possible from the stations, and hence to exhaust the wells for several feet in depth. In order to overcome the difficulty of exhausting the wells beyond the suction limit, and sucking air, which would make the pump lose its vacuum and stop pumping, a vertical pump was installed. The pump was set at the bottom of a vertical frame, and was driven from a horizontal motor by a quarter-turn belt. Finally, to avoid the belt losses, a vertical motor was used, direct-connected to the pump. The following is a description of the method of installation, and the apparatus used in the latest stations. The frame is 20 feet high, and consists of four angle irons thoroughly braced by lighter angles and united at the top to a cast-iron ring on which the motor is fastened. The top ring is provided with adjusting screws for lining up the motor. The pump, which is a IRRIGATION NEAR BAKERSFIEL1). 131 No. 8 centrifugal, has two inlet openings diametrically opposite, and on the upper side of the runner. The pump shaft after pass- ing through a stuffing box and an upper bearing, which is bolted to the pump casting, is connected by a coupling to the inter- mediate shaft, which in turn is connected to the motor shaft by a similar coupling, which allows of a longitudinal adjustment of the pump shaft for the purpose of balancing. There is about 1.5 inches end play in the pump runner, which may be made use of in balancing the end thrust of the pump, which is largely dependent on the position of the runner in the shell. This end thrust may be very large in some pumps, and it is highly desir- able that it be properly balanced, as otherwise it is likely to cause serious trouble. The intermediate shaft runs in one or two adjustable bearings (the number depending on the length of the shaft). These bearings are fastened to the angle iron frame. Below each motor bearing, and fastened to the shaft, is a cylindrical brass receptacle, which catches the oil which drips from the bearings. A stationary bent tube inserted in this receptacle catches the oil clue to its high speed, and forces it up the tube, returning it to the top of the bearing. Thus the oil is kept in constant circulation. This oiling device was not satisfactory, as it threw oil all over the motor from the fine spray which formed. It was finally much improved by a change of design which did away with all trouble, and in addition passed the oil through a filter before entering the bearings. The entire weight of the rotor, and of the pump runner, at the start was taken in the top motor bearing, and the bottom bearing of the motor limited the play due to up thrust of the pump in case it. was sufficient to raise the rotor and runner both. The upper bearing of the motor was unable to stand running with the weight of the motor armature alone, as it would have burnt up under these conditions, so it was necessary to rely on the end thrust from the pump relieving, in part at least, this pressure. The result in practice was satisfactory, however, and gave little trouble. The suction entrance on top of the runner served to exert a strong upward force, and by proper adjustment the pump could be made to balance perfectly and to lift exactly the weight of the revolving parts. Still, it would in general be desirable to have bearings better able to stand a greater end thrust without danger. 132 PRACTICAL IRRIGATION. The usual method adopted before establishing a station, was first to bore a 6-inch well to determine the nature of the strata, and to see whether there was a probability of getting a good well. If the indications were poor, the site was abandoned. Twenty feet of good water-bearing sand, or sand and gravel, were considered a good indication for a well. If the indications were good, a 13-inch well was next put down and tested by pumping it with a centrifugal pump driven by a steam engine. If the well delivered a flow of 1.5 to 2 cubic feet per second, while the water was drawn down 20 to 25 feet in the well, the test was considered good, and three addi- tional 13-inch wells were put down. These wells were all in a line, and about 8 to 12 feet apart. Riveted, galvanized iron well- casing was used. The joints opposite the water strata were perforated before being put down, by narrow slits about an inch long, as a better job could be made than by perforating in place. A steel shoe was fastened to the end of the casing, which was forced down by a weighted lever, while the material was removed from the inside by a sand pump. It was desirable not to perforate the casing too high up, as the surface water, carrying considerable air and falling into the well water when the well was exhausted to a considerable depth, was liable to drag air into the suction pipe and make the pump lose its vacuum. In order to serve as an adjunct to the strainer, and to keep sand from flowing too freely into the well, a pipe was driven into the ground next to the well casing as it was being put down, and the top of this pipe kept covered with gravel, which followed the well casing down and formed a layer over the outside of it. When for any reason it was impossible to land the casing in clay or rock, the bottom of the well was filled with loose rock to keep the sand from coming up the well. The wells varied in depth from 60 to 110 feet. After the wells were completed, a pit was dug around them to a maximum depth of about 20 feet. In the latest stations the pits were sunk a few feet below the existing ground water level, at the time they were put in. A portable, direct-connected 30-horsepower motor and a No. 8 centrifugal pump were used to keep the water out of the pits during the installation of the IRRIGATION NEAR BAKERSFIELD. 133 station. The pump, which had its suction pipe down one of the wells, was kept running continuously during the construction of the pit. The four wells for each station were all in line, and were arranged so that the vertical pump was in the center, with two wells on either side. The pit is lined with redwood, the lower boarding being 2 by 12, and the upper boarding, 1 by 12. The flooring, which consists of a double layer of 1 by 12, is laid on mud sills, and arranged so as to break joints. The joints on the sides of the pit are covered with 1 by 4 battens to make them tight and to keep the sand from flowing into the pit. Inside the pit, 4 by 6 vertical stringers are set 3 feet apart, braced by 4 by 6 horizontal timbers every 6 feet. The pits are made 6 feet wide, except in the center, where they are 8 feet wide, to allow for the pump and frame. The timber lining of the pit was carried up about two feet above the ground, and the pit was covered by a roofing of shakes. In the center of the building where the motor stands, a house is built about 12 feet in height above the ground, provided with a ventilator in the roof and also in the side. The flooring of this house is level with the top of the pit, and the top of the frame on which the motor stands is slightly above the floor level. Thus the motor is in a position where, even should the pit fill with water, it will not be damaged. Entrance to the pit is provided by a door in the roof, and to the motor house by a side door. A layer of hay is thrown in next to the boarding of the pit when backfilling the outside of the pit, in order to prevent the sand from flowing in through the cracks in the boards. The casing of the wells is cut off just above the pit floor level, and is ham- mered down so as to make a flush joint with the floor. The piping is all composed of galvanized iron riveted and soldered. Vertical 6-inch pipes about 40 feet long are inserted in each well, and are provided with flanged couplings to connect to horizontal suction pipes, which run to the pump. The discharge pipe is 10 to 12 inches in diameter and runs into a wooden box 3 feet wide, at the end of which is an uncontracted weir. These weirs are provided with glass gauge tubes connected by pipe fittings to the water on the inside. A wooden strip is nailed on the outside of the weir at the level of the crest, which 134 PRACTICAL IRRIGATION. is composed of a strip of galvanized iron. The head on the weir is measured by a foot rule, the end of which is placed on this strip, the head being told by the level in the gauge glass. In the enlarged pit, where the pump frame stands, are fastened square frames of 6 X 6 timber surrounding the pump frame. These are placed 6 feet apart, and are used to steady the pump frame by the use of bolts between the timber frame and the corner angle irons of the pump frame. About 60 feet from the pump house is a transformer house where the transformer, motor starter, switches and fuses are located. These houses have been separated, so that, in event of a fire, the plant would not be a total loss. Energy is fur- nished to the transformer houses at 10,000 volts, 3 phase. The lines enter the transformer house passing through a 10,000-volt fused-pole switch, operated by a lever inside the transformer house. Three lightning arresters are connected to the 10,000- volt wires, which then run to two 10,000-, to 550-volt trans- formers. Two types of transformers are used 15-kilowatt air-cooled being in some stations, and 25-kilowatt oil-cooled in others. The three 550-volt wires pass first through asbestos-covered fuses, the fuse blocks being mounted with asbestos behind them so as to minimize danger from fire, and then through a knife switch, and the auto starter for the motor, from which they run to the motor. The wire joining the two transformers on the 550-volt side is connected to a static arrester, the other side of which is grounded. The lighting circuit is taken from a 30-volt tap on the trans- former secondary, the tap being next to the wire connected to the arrester to minimize danger from shock. Thirty- and 40-horse- power, 3-phase, 550-volt motors are used for the pumps, which are No. 8, and run at 900 revolutions per minute, delivering between 3 and 5 cubic feet per second, depending on the lift, the usual head being 40 feet. As the stations were to be operated with little attendance, it was necessary to make everything about them as safe as possible from the effect of possible accident. With this in view, each station was provided with an automatic cut-out, to cut out the motor in case the power went off. For this purpose a heavy weight, sliding in ways, was hooked to the switch handle. IRRIGATION NEAR BAKERSFIELD. 135 This weight was released by a trigger, and thus required very little power to make it open the switch. Several devices were used to operate the trigger, the particular form depending on the conditions of the case. In a transmission system there is always the liability of a momentary short circuit, caused by a discharge of the lightning arresters, or by some other cause, making the voltage drop for only a few instants. In such an event it is not desirable for the cut-out device to operate, and it must be designed with that in view. The form most commonly used consisted of a vertical tank in which was a float provided with a vertical stem engaging the trigger. This tank received its pressure from a point near the pump discharge, the water standing at a level above the crest of the weir equal to the head on the w r eir plus the friction head in the pipe. If the pump stopped, the float would gradually sink until it tripped the weight, but a temporary slowing down would not affect it. Another device consisted of a curved vane in the discharge pipe, supported by pins, one of which extended through a stuffing box and operated the trip lever through a bell-crank lever. When water was flowing it kept the vane along the pipe where it offered little additional fractional resistance, but when it ceased to flow, the weight of the vane tripped the switch- opening weight. Time element electric devices have also been used. These consisted of a laminated electromagnet, the armature of which was kept closed by 30- volt alternating current. In one form of device there was a glycerine dashpot connected to the arma- ture, there being a small hole in the piston to allow of slow motion. If the power went off and came on again before the piston sank too far, the armature would be reattracted before the switch had opened. In another form the retarding element consisted of a small fan blade connected to the armature by clockwork. In general, the first two forms are more desirable, where they can be used, since if for any reason the pump loses its priming, they will rut out the motors. With regard to piping leading to the float boxes, for the first form, it is advisable to use in general galvanized pipe, and not to use too small a pipe, on account of danger of the pipe rusting 136 PRACTICAL IRRIGATION.' up and stopping. This is important, particularly where the water is alkaline. As there was in some cases a considerable volume of piping to prime before starting the pump, priming by hand was too slow, so air pumps were installed in the pits, belt-driven from the motor shaft. When the pump was primed the belt was taken off. This saved considerable time in starting the stations, and pumps which took half an hour to prime by hand could be primed in a few minutes in this manner. Check valves and sometimes gate valves were placed just above the discharge outlet of the pump, to close the pipe for priming. In some stations when they had not been run for considerable time, the water carried a large amount of entrained air, which, if the pump were run with the discharge open, would be liable to make the pump lose its priming. For these stations the gate valves were a decided aid in operation, as they could be used to throttle the discharge, as long as there was any trouble of this nature. Fig. 29 is a map of the pump stations of the Kern County Land Company. There are, altogether, 27 well-pumping stations scattered over a considerable area denoted by small squares and numbers along the lines of the Power Development Company. This was divided into three sections, and one pump man assigned to each section. These three pump men attended, alone, to the operation of all the plants, visiting each station in operation twice a day. Each pump man was provided with a horse and cart. In addition the operation of the plants required part of the time of an inspector, who had charge of all repairs and installation work, and the services of his assist- ants. The pump men, who were not skilled mechanics, were expected to attend to merely the operation of the stations and to report any repairs needed. When in operation the stations ran continuously day and night, and were shut down only a very small proportion of the time. Thus it will appear that the cost of operation was reduced to a minimum quite a striking contrast to the method of operation adopted in some pump stations, where three men working 8-hour shifts are employed every day to watch one 30-horse power motor and pump operate. It may occasion doubt in the minds of many whether such a method of operating is wise, and whether it is not taking undue IRRIGATION NEAR BAKERSFIELD. 137 chances of loss from accident from no attendant being at hand. The experience of the writer is quite to the contrary. In fact, the total loss from accidents which could have been avoided by constant attention, would not exceed a few hundred dollars during the writer's connection of two years with the company. 138 PRACTICAL IRRIGATION. No serious accident occurred during that time, the only damage being the burning out of an occasional bearing. The secret of success in such a matter consists in keeping the plant always in the best order, occasional overhauling, and constant watch- fulness. The pumps discharged into the same canals used by the gravity system, and consequently there is no direct means of obtaining a record of the value of the irrigation. Further, as they were used only to supplement the river water, the duration of their operation during the year was a variable. Had they been used as the sole source of water supply, they would have run nearly continuously throughout the year, in a climate like that of Bakersfield with its very small rainfall. Of the river water, one-third of the total water supply is lost in the canals. It takes, on an average, 1 acre-foot of water supplied to the canals, for the irrigation of 1 acre of land per irrigation. The pumped water has far shorter distances to travel than river water. Allowing for the effect of a decreased quantity, and greater relative seepage losses, it will be conservative to say that it takes 1 acre-foot of pumped water to irrigate an acre of land. Land is irrigated once per cutting for alfalfa, and yields an average crop of one ton per acre. Hence 1 acre-foot of pumped water is needed per ton of hay, and 4 acre-feet per acre are required, per year, as four crops are grown in a year. The average output of the pump stations was 3.3 cubic feet per second. This average was cut down to this value by some poor stations where the wells were weak. The average motor horsepower per station was 33. Energy was bought accord- ing to the horsepower of the motor installed, and with no reference to the load, the price paid being five-eighths cent per horsepower-hour. Hence the cost of energy per 10 horsepower- day was X 7 = $1.50, which was the cost per second foot of o 10U water per day. Hence the cost per acre-foot was 75.7 cents for energy alone, or double the cost charged for gravity water by the canals. The remaining expenses, including wages, repairs, and all fixed expenses, were practically constant, and were independent of the hours of operation of the plant. In estimating the fixed expenses, 7 per cent is assumed for interest and taxes, 6 per cent for depreciation. The total cost of the IRRIGATION NEAR BAKERSFIELD. 139 27 stations, including the cost of abandoned stations, was $92,000, nearly 4 per cent of which was for abandoned stations. The total annual expenses were as follows: Fixed expenses, 13 per cent of $92,000 . 811,960 per year. Cost of attendance 2,477 " " Cost of maintenance 3,035 " " Cost of repairs and renewals ... . 3,419 " " Total annual expenses $20,891 " " The actual expense for attendance was for the 27 plants, $:M77 per year, or $91.75 per station, or 25 cents per station per day. This included wages and board of the attendants, feed for their horses, and repairs on their wagons. This is an excep- tionally low figure, and it is very doubtful if any stations of equal capacity ever came anywhere within several hundred per cent of these figures. The charges for maintenance included the time of the pump inspector and his two helpers in ordinary overhauling of the stations, and also all supplies for operation, such as oil waste, etc. The charge for repairs included a $1700 charge for the recon- struction of one of the first experimental stations installed. The peculiar conditions encountered made this reconstruction a very expensive piece of work, and one which was little likely to recur. However, work of reconstruction as well as the danger of accident must always be considered in fixing costs. Included under repairs and renewals were certain improvements which more properly belonged under installation. Taking this into consideration, the charge of 6 per cent for depreciation is a liberal value, as the repairs and renewals are nearly 4 per cent. A very large part of the charges for maintenance and repairs consisted in team hire, and time lost in getting around the country, owing to the widely scattered stations. The total charge of $8931 per year which actually had to be paid out, was only 91 cents per day per plant. If the plants ran continuously they would have raised 177 acre-feet per day, or 177 X 365 = 64,500 acre-feet per year, at a cost of 33.2 cents per acre-foot for fixed charges; or a total cost of 75.7 + 33.2 = $1.09 per acre-foot. During the last part of the year in question, the pumps ran only 34 per cent of the total time, making the expense of all charges but power, per acre-foot, 98 cents, and the 140 PRACTICAL IRRIGATION. total cost SI. 74 per acre-foot, and hence per ton of hay. This was an exceptionally low irrigation factor, and was due to the fact that owing to accidents the Power Development Company had been unable to furnish energy for the operation of the pumps. During the first six months of the year when energy was obtainable, the pumps ran about 90 per cent of the time, though no record was kept of the same, as at that time energy was paid for on a flat rate of $30 per horsepower-year for the first 100 horsepower, $25 per horsepower-year for the second, and $20 per year for all additional horsepower. Under those con- ditions the annual cost of energy for 33 X 27 = 991 horsepower was $19,320, which is 29.9 cents per acre-foot, assuming 100 per cent irrigation factor, or 33.2 cents, assuming 90 per cent irri- gation factor. Adding to this latter figure the corresponding rate of 37 cents for fixed and operating charges, gives a total cost per acre-foot of 70 cents. Hence, owing to change of rates and conditions in the same year, the cost of water went from 70 cents to $1.74 per acre-foot. With 90 per cent irrigation factor and five-eighths cent per horse- power-hour, the cost would be $1.13 per acre-foot. The value of a ton of hay in the field is fully $4. Under the system of charging by the rated motor horsepower, a far more economi- cal showing could be made by installing much smaller motors in the stations where the wells were weak. As the pumps gave an efficiency of 60 per cent, they were capable of lifting on an average lift of 40 feet, 4.4 cubic feet per second; the 30-horse- power motors, 4 cubic feet per second, and the 40-horsepower motors, 5.3 cubic feet per second. The actual output of plants went from 1.6 to 5.7 cubic feet per second, and the lifts from 30 to 50 feet. The efficiency of a pump in practice, when operating under a high vacuum, will usually be less when pumping from a well than when pumping from a pond, due to the entrained air. Mr. L. A. Hicks was the first engineer in charge of the installation of the pumping plants, and was succeeded later by the author. CHAPTER XI. METHODS OF CHARGING FOR IRRIGATION WATER. THERE are, in general, three systems of charging for irrigation \vuter, at present in use: 1. Where no particular limitation is placed on the water, contracts simply stating that the farmer will be provided with sufficient water to irrigate his land; 2. where he will be pro- vided with a stated flow for a stated length of time, distributed at stated periods at a stated annual rate; 3. where the charge for water is directly proportional to the amount of water used. None of these systems is in general altogether equitable, since it does not proportion the expense for \vater to the cost of delivering the same. The best system of charges should fulfill three conditions: 1. It should proportion the charges to the expense of delivery. 2. It should induce economy on the part of irrigators. 3. It should be simple. Consideration of No. 1 requires an analysis of the elements of the cost of furnishing water. Take, for example, the case of an irrigation company furnishing pumped water to its custom- ers. For the company to be in position to supply water for irrigation, it must first provide a pumping station, ditches, gates, etc., all of which are in proportion to the sum of the maximum rates of demand of the water supplied to customers. Before starting to deliver water to consumers the plant must be operated to a sufficient point to supply losses in the canals. Up to that point of operation the individual guaranteed rate of supply is a measure according to which the expenses should be divided. Additional expense of operation of the plant beyond this point will consist mainly of fuel and labor, and will be proportional to the actual quantity of water used ; hence all expenses beyond this point of operation should be divided in proportion to the actual quantity of water consumed. In other words, an equitable policy, to fulfill condition No. 1, would consist of charging each consumer of water a fixed rate with a guaranty to supply him 141 142 PRACTICAL IRRIGATION. with such a flow for a given length of time every so many days, and in addition should charge a rate directly proportional to the actual amount of water used. Such a system would tend to promote economy in the use of water, as it is directly to the financial advantage of the irrigators to practice it. Moreover, it is a fair basis of division of the charges, and it is only right that the farmer who is economical should not pay for the extravagance of his neighbor. In some places, usually where no limitation is placed on the irrigation water, the payment for the same consists of a certain percentage of the crop. This method of charging has the advantage of attracting people with small capital. However, it sometimes occasions disputes, and is liable to give rise to a suspicion that the farmer has not reported the full amount of his crop. Of course the manager of an irri- gation company has to consider, in addition to charging for furnishing water on an equitable basis, the idea of presenting an attractive prospect in order to settle the country and to obtain customers. This may be used as an argument in favor of the percentage of the crop basis of charging, on the ground that this system would attract those who would not otherwise enter into the undertaking. A careful consideration of the actual cost to an irrigation company for the delivery of water indicates that the charges for same should be divided among customers in accord- ance with a method embracing the three following principles: 1. Expense which should be borne equally by the consumers. 2. Charges pro-rated according to the maximum required flow. 3. Charges proportional to the volume of water actually used. Charges of the first nature may be considered to include general expenses of the company as well as the expense of zanjeros* Under the second heading may be classed the charges which are independent of the water actually delivered; in other words, charges of this nature should be for the cost to the ditch com- pany of being in a position to deliver water at a certain rate. Charges of the third kind are dependent upon the cost to the company of actually delivering a given quantity of water. In a pumping plant, for example, the capacity of the station would have to be proportioned to the maximum rate of demand for water; hence all expenses for operating the plant to a sufficient point to supply the seepage losses in ditches and for interest and * Zanjero is the Mexican name for ditch tender. CHARGING FOR IRRIGATION WATER. 143 depreciation on the plant, should be pro-rated according to the maximum rates of demand of the various customers. The annual value of the water right, if the same has any value, should also be pro-rated in the same manner, as well as the interest on and cost of maintenance of ditches, gates, etc. The additional cost of delivery of water over what would be necessary to keep the ditches full and in repair, should be borne by the customers in direct proportion to the quantities of water actually used. This would mean, in other words, that a customer of the com- pany would pay the company a certain fixed sum for the privilege of obtaining water, and in addition thereto a sum varying directly with the rate of use of water which the company guaran- tees to furnish. In event of any shortage of water, this latter rate would not be the same, but the water would be delivered among the various customers in proportion to the rates of delivery for which they pay. Besides these two charges, the customer would pay a rate proportional to the actual volume of water delivered to him. In fixing the rate of charge at a given rated delivery, a reasonable amount of time should be taken. For example, provided the consumer uses a flow of 3 cubic feet per second for one day a week, the flow for which he should be charged would be three-sevenths of 1 cubic foot per second. In other words, the flow should be reduced to the basis of a maximum continuous flow, and should not be considered as a maximum absolute flow. A contract for water would then state that the consumer was entitled to a certain specified flow delivered for a specified number of hours once every so many days, for which he would pay a specified rate per month, whether or not use was made of this quantity of water; and in addition would pay a fixed rate per acre-foot of water delivered. This would make it to the advantage of the consumer to apply for as small a flow as possible and to use the water as economi- cally as possible, both of which are desirable features in the practice of irrigation. If during the course of the year the con- sumer found he would need more water than the flow for which he had contracted, if this water were available he could obtain it by paying for it at the fixed rate per acre-foot. This method of charging for water might lead to a tendency to reduce the flow applied for to a quantity too small for the needs of the land, in order to reduce the charges under the 144 PRACTICAL IRRIGATION. second head, consumers relying upon being able to obtain surplus water at the price charged per acre-foot. However, by so doing they would render themselves liable to suffering from possible shortage in supply, and steps could easily be taken by the company to prevent this becoming an abuse. In considering the proportions of the constituent parts of these three charges, three distinct cases may be taken up: 1. Gravity distribution without storage. 2. Storage system of distribution. 3. Pumping distribution. In the gravity system the largest charge would be for the guaranteed flow of water, the total amount of water used making little difference in the cost to the company. In case No. 2, assuming an expensive reservoir system from which the water is mainly supplied by storage, the charge for the quantity of water actually used becomes comparatively great, since the interest on the investment in the reservoir, repairs, and depreciation of the same are chargeable to the value of an acre-foot of water. In case No. 3, the additional cost of fuel and labor contributes largely to charge No. 3. Let : A = Annual interest, depreciation, repairs and taxes on reservoir. B = Total annual value of water right. C = Annual value of water lost in distributing canals. D = Labor and interest on, and repairs, and depreciation of main and distributing canals. E = Annual cost of zanjeros. F = General expenses. G = Interest and depreciation on power house, head works, labor, operating expenses, and cost of fuel sufficient to supply seepage losses of canals. H = Additional annual expenses of power house required for operation of plant at capacity demanded. N = Number of customers. P = Maximum rate of consumption of water. p = Individual rate of consumption. Q = Acre-feet stored less evaporation and seepage from reservoir = total acre-feet of reservoir output, or = output of pump station. CHARGING FOR IRRIGATION WATER. 145 q = Acre-feet sold to individuals. X = Acre-feet lost in distributing canals. Assuming case No. 2, where practically all the water is stored and must be taken from a reservoir, the following three charges should be made: E 4- F should be charged alike to each applicant for water, as charge No. 1. AX //? -4- C 1 -\- D\ I- - -\p = charge No. 2, where C = An = charge No. 3. () -X Suppose the water for irrigation is supplied direct to the land from a pumping station, then charge No. 1 would be the same as in the last case. p = charge No. 2, charge C being included in G. charge No. 3. -- A These cases will serve to illustrate the general method sug- gested, which is similar to a method of charging for electric energy, proposed by Mr. A. M. Hunt, and form a basis from which equitable charges for water may be made. In proportioning the charge for the water itself, the assumption has been made that the value of the water per se lay in the broader right to utilize a given flow of water, and not in the intrinsic value of the water itself. This is true on the assumption that water not so util- ized would have no market value. If, on the other hand, how- ever, such water has a market value per se, then the real value of the water becomes of two kinds: (1) the value of the water right itself, and (2) the intrinsic value of the water. In this event the latter value should be added to the charge for water. Take the condition of a gravity plant without storage which 146 PRACTICAL IRRIGATION. has sold water rights up to the limit of its capacity, providing at certain periods of the year its full capacity will not be required, due to wet weather or other causes, no material saving will result to the company from this cause, nor can the water not so used be disposed of. In that event it is not just that any- thing but a small charge should be made for the same. Broadly speaking, in a gravity system the equitable system of charging would tend more toward a flat-rate system than toward a meter system. The system proposed, however, is one which com- bines the principles of both these systems. In countries where water is scarce and the supply not equal to the demand for irrigation, water may justly be assumed to have a high intrinsic value in addition to the value of the right to use a certain flow. This matter should be taken into con- sideration in fixing a rate per cubic foot per second. For a rate to be fair to a company investing capital in an irrigation plant, an income should be assured to the company in wet years as well as in dry years, and any increased expense for actual amount of water delivered in addition to the expense necessary to be in position to deliver a given flow should also be charged to the consumer as charge No. 3. CHAPTER XII. ECONOMIC LIMIT OF IRRIGATION. THE greater part of the present water supply of irrigation plants consists of the water diverted by gravity from flowing streams, conveyed by ditches to the land. Though in some cases the development cost of gravity water so obtained is high, still in the majority of instances the cost per unit volume of water diverted is small, and the cost of irrigation of this type is particularly low in comparison with the greatly increased productivity of the land. In the arid region, much of the land is of little or no value without water, while the soil and climate are such that irrigation is capable of producing plentiful crops and proving of value far greater than the cost of irrigation, where the development is not expensive. According to Elwood Mead: " If every drop of water which falls on the mountain summits could be utilized, it is not likely that 10 per cent of the total area of the arid West could be irri- gated, and it is certain because of physical obstacles that it will never be possible to get water on even this small percentage." The available proportion of the rainfall is greatly limited, the water being disposed of in four manners: Evaporation from the surface of the ground, transpiration losses, underground waters, and surface run-off. Much of the water is lost by evaporation before it has an opportunity to seep into the ground. The preservation of the forests helps greatly to diminish this loss, protecting the land from the rays of the sun, and allow- ing the water time to sink into the ground, to join' the under- ground waters, which flow through the subterranean drainage system of the country. The underground supply, which is the source of supply of all springs and wells, both pumped and artesian, is hence by no means unlimited in quantity. It will often be found in regions where there has been very extensive well-development, that the static level of the water in the wells has greatly lowered ; wells which formerly gave a strong artesian 147 148 PRACTICAL IRRIGATION. flow have weakened in flow or have ceased to flow, and must be pumped, while from pumped wells the water must be lifted from greater depths. It is evident that the actual water supply which can be made available for irrigation in the arid region is far less than the needs of the land which is capable of being irrigated. As much of this land is valueless without irrigation, there will ultimately be use for all the available water supply, provided the cost of development is not too great, and it is this cost alone which will limit the use of water. Evidently the present cost of irrigation water will by no means determine the ultimate irrigation development. Where the cost of irrigation is but a small percentage of the benefits derived therefrom, far higher prices can be profitably paid therefor. . Water, per se, has an intrinsic value, where the demand exceeds the supply, quite apart from the cost of develop- ment, and the land to which the water right attaches will on that account increase in value up to the point where the net value of irrigation will yield a fair profit on the increased invest- ment. Hence it is evident that irrigation development will tend to increase until the costs of irrigation will allow only a reasonable profit from its use. This will not in general be before, at least in many places, the entire low- water supply is utilized, and much of the water which now runs to waste is stored in reservoirs. After the natural flow of the streams is all utilized during low water, further development must come either from storing the surplus water thereof, at periods when it would otherwise run to waste, or by developing the under- ground supply, usually by the use of wells. The development of water supply by these two methods is quite extensive, and although most wells must be pumped, still improvements in pumping machinery and the increased use of electric trans- mission circuits covering the country with a network of lines are reducing greatly the cost of pumping water. A study of present costs and values of irrigation brings out very forcibly the fact that a very extended use may be expected of reservoirs in the United States, and that in many cases water may be stored at costs well within the present actual profitable costs of irrigation water. Economic considerations require that in the arid region, with ECONOMIC LIMIT OF IRRIGATION. 149 its limited rainfall, irrigation development shall not be finally governed by present cost, but rather by the value of irrigation, and that this alone will ultimately determine the extent of reservoir construction. The question arises, What is the probable field for storage reservoirs, and how much water must they be called upon to store? To answer this question fully requires a knowledge of the time, value, and duration of flow of the water supply, and of the demands for irrigation water. Also we must know the losses from the reservoir, and the periods of such losses. Reser- voir losses consist of evaporation and seepage. The evaporation losses will in general vary from 3 to 7 feet per year in arid regions, and quite extensive data in this respect are available for various places throughout the country, giving the monthly and annual evaporation. Seepage losses are difficult to determine. If the bottom of the reservoir is of water-tight material, losses of this nature will be small; but if the bottom is of a pervious nature, it will be unsuitable for reservoir purposes, and can be made to hold water only by lining the reservoir with impervious material. According to Elwood Mead, to utilize the entire supply, 40 per cent of the flow of Western rivers would need to be stored for irrigation, while the remainder could be used directly on the land during its irrigation period of June, July, August, and September. In many places irrigation is practically impossible on any scaje, without the use of reservoirs, since the rainfall may be so uncertain, and the drainage area so rugged and un- protected, that there will be no water available at times when it is most needed for irrigation. In that event practically all irrigation water must be stored. Artesian wells used for irrigation in Southern Texas, are usually provided with storage reservoirs of sufficient capacity to store a few days' supply of water. The irrigation factor there, which is the percentage of the year during which the output of the well is actually used, averaged only 20 per cent. In other words, four-fifths of the supply was not used, and in the majority of cases went to waste. This makes the expense of water, which consists of the interest on the cost of, and of the depreciation of the wells, five times as great per unit quantity of water, as if the entire supply had been used. If there had been a storage reservoir of sufficient capacity to have held the 150 PRACTICAL IRRIGATION. supply of water delivered throughout the year, then if 20 per cent of the yearly output were lost in evaporation and seepage, the well would have furnished four times as much available water, and would have irrigated four times the area. If the fixed charges on the reservoir were the same as on the well, then if the reservoir cost three times as much as the well, the cost per unit of water would be the same. If the reservoir were more expensive, then it would pay better to put down more wells, provided each well gave the same quantity of water. This, however, will not be the case, as in general the wells will interfere with each other more or less, and in some cases may give but little total increase over the flow from only one well. The fact of being able to multiply fourfold the available irrigable area is no small argument for reservoir construction. There is still a large field for the construction of reservoirs of small capacity say of a capacity sufficient to hold from twelve hours' to a week's supply. Many pumping plants operate for only 12 hours per day, as night irrigation is not generally desirable. This results in having to install plants far larger than would otherwise be necessary. In Southern Texas the irrigation factor of the pumping plants was only 14 per cent. In other words, on the average the plants ran only one-seventh of the time. The total fixed expenses of the plants, consisting of interest and depreciation, were about equal to the sum of the labor and fuel expenses, while in the average case the fixed expenses were about three times the sum of the average labor and fuel expenses. The labor expense was a compara- tively small item. Many of the plants operated only 12 hours a day, thus necessitating a greatly increased first cost of plant over what would be necessary with the use of a reservoir and a smaller plant, for as labor is so cheap, the cost of pumping would be much reduced, and the initial investment also, by operating the plant continuously night and day, storing the water pumped at night, in a reservoir. The advantages of small reservoirs are numerous and have already been discussed (see p. 48). Suffice it to say, that many very small pumping plants, realizing the advantage to be derived, have constructed reservoirs to aid in the operation of the plants. To give some idea of the present cost of irrigation water, the ECONOMIC LIMIT OF IRRIGATION. 151 average cost of pumped water in Southern Texas in 1904, using straight averages was $12 per acre-foot, and the average cost per acre irrigated was $16 to $20, while the cost of irrigation, using the weighted averages, was from $5 for steam plants under low lifts, to $18 for gasoline plants, per acre, per year, the average being $6 for all plants and $12 for plants not used for rice irrigation. As the average depth for gasoline plants was 1.0 foot, the maximum average cost of water was $18 per acre-foot. The highest price paid for water for irrigation in Southern Texas was $50 per acre-foot. This water was delivered from a pipe line. This cost, it is true, is excessive for anything except truck irri- gation. One thing particularly noticeable about irrigation is that the depth of water used varies inversely with the cost, and that high cost tends to economical use of water. If the same quantity of water were to be used when water is dear, as is used when it is cheap, the irrigation would be impracticable. However, by more careful distribution and use, the farmer finds he can get along with a far smaller quantity of water, and the high cost is no longer prohibitive. The depth of irrigation water varies largely with the crop, soil, climate, and cost, not to mention the irrigator himself. In arid climates the depth usually applied is 2 to 5 feet. Where the water is distributed with care, a depth of 2 feet will often provide sufficient irrigation unless conditions are unfavorable. In semi-arid climates w r here the water is skillfully used, and the soil suitable, frequently not over 1 foot of irriga- tion water is employed per year; and often great benefits are derived from 6 inches, judiciously used. In some sections as much as 10 feet are used per year, but this is excessive. The value of irrigation depends on the crops, the seasons, and the distance to market. For truck, it is not uncommon for irrigation to be worth from $100 to $300 per acre, and in some cases as high as $1500. The total value of field crops will vary from $20 to $80 per acre, and irrigation will be worth, for such purposes, up to as high as $50 per acre. These figures have been given in order to furnish some idea of the values and costs of irrigation, and to have a standpoint, somewhat indefinite it may be said, from which to view the possibilities of storage of water for irrigation. The problem is quite complex from the number of variables which must enter into it. Each case 152 PRACTICAL IRRIGATION. should be figured out for itself, as it is absolutely impossible to lay down figures for general guidance. Great economic advantages may be derived from the use of reservoirs and storage tanks, both large and small; and, as will be shown, they may be made effective, not alone in increasing the available irrigable area, but also by diminishing largely the first cost and operating expenses of lands irrigated by pumping plants and artesian wells, as well as by gravity systems. Inves- tigations show that where the ground is at all suitable, large reservoirs may be constructed entirely in embankment, on level or gently sloping ground, at a less cost than the average cost of construction of natural reservoirs now built. There are many places in the country whefe such reservoirs can be constructed, where no natural site now exists. This is most significant, when it is fully understood. Water may even be pumped to considerable elevation, and stored in reservoirs con- structed in embankment, and supplied therefrom at prices com- parable with present costs of pumping alone, so that places without present irrigation facilities may come under its bene- ficial influence. There are many elements entering into the economic construction of reservoirs of this nature, but if all necessary data are given, the design of the reservoir can be figured mathematically to deliver a given quantity of water at as cheap a cost as possible. Engineers may differ as to the probable values to be assigned to the various costs, but the principles of determination of dimensions remain the same. In any given case it would doubtless be possible, if the reservoir be large, to have a site possessing some natural advantages, even on comparatively level ground. The figures given for large reservoirs, and the method employed, will probably be useful, not so much in an individual case, owing to the variation of conditions encountered, as to direct attention to the feasibility, or lack of feasibility, of such undertakings, and to suggest alternative plans for irrigation and reservoir projects. It is particularly necessary to verify, as far as possible, the assump- tions for any actual case, and to note the effect of changes in the assumptions which might be liable to occur. CHAPTER XIII. EARTH TANKS. THE small earth tank has an important position in many kinds of irrigation on a small scale, where the supply is of limited capacity. It is, however, not uncommon to see tanks constructed at a cost fully twice as great as should be the case. The section of a reservoir to be adopted depends in part on the land which it is desired to allot to it, but it should be remembered that the circle has a larger area for a given perimeter than any other figure, and hence on level ground circular reservoirs will contain considerably less material in the banks for a given capacity. Thus a square tank will have 13 per cent more material in its banks than a circular tank of the same capacity, and hence will cost 13 per cent more. With a rectangular tank the expense will be increased to considerably greater extent. Thus, for example, a rectangular tank twice as long as it is wide, and of the same area as a square tank, will have a perimeter 6 per cent greater than the equivalent square, and 20 per cent greater than the equivalent circle. If the rectangular tank be of three times greater length than its width, it would have a perimeter 15 per cent greater than the equivalent square, and 31 per cent greater than the equivalent circle, though the increased volume of the banks may not be quite as great as these figures would show. In considering the reservoir problem, all reservoirs will be assumed to be of circular section unless specifically stated to the contrary. All linear dimensions will be in feet, and cubical contents of the reservoir banks will be in cubic yards; reservoir capacities will be in acre-feet. The common method in use in figuring reservoir capacity of small earth tanks is to figure the entire capacity from the bottom of the reservoir to the top of the bank. This method is both misleading and erroneous, since without pumping from the 153 154 PRACTICAL IRRIGATION. reservoirs, the water cannot be drawn below the level of the ground, and the reservoir should not be filled level with the top of the banks, but a safe margin must be left to provide for wave action. This margin, which is the vertical distance between the top of the bank and the highest safe water level in the reservoir, we shall call clearance. It should depend largely on the size of the reservoir, and, unless specified to the contrary, J . ^^ *; r ^ -^ ^ *" x < ' . ,/ 1 i X / / / / / 6a se a ia 777 ?fr 7- I? ? / 7t 500 1.000 &00 Fig. 30. Reservoir Clearance. it will be defined by the equation, b = clearance = 0.06 (10 + \/d) feet, up to a clearance of 3 feet, after which it will remain constant for larger diameters. In this equation d = inside base diameter of the reservoir in feet. The relation between clearance and inside base diameter is graphically represented in the curve in Fig. 30. Thus, for example, to find the clearance for a reservoir of 900 feet inside base diameter, -outside 6ase afi'a. Fig. 31. Reservoir Capacity Diagram. follow the vertical line representing 900 feet up to the point where it strikes the curve. The corresponding vertical distance as measured by the vertical height of this line is 2.4 feet. The proper clearance depends on the exposure of the reservoir to winds, and on the probable intensity of the winds. The actual capacity of the reservoir we shall figure as that capacity which is included between the elevation of the lowest original ground level in the reservoir and that of the highest safe water level, defined by allowing for the clearance, as above (see Fig. 31). EARTH TANKS. 155 Stevenson's formula for the relation between the wave height, H ft., due to wind and jthe fetch, F, nautical miles, is as follows: H = 1.5 VF + 2.5^F _or expressing the fetch in feet D. H = .0191 VD + .281 ^D. The formula gives the following results: D = 100 H = 1.08 400 1.64 900 2.11 1600 2.53 2500 2.94 5000 3.71 10000 4.72 20000 6.02 Throughout the remainder of this discussion three general cases will be considered in reservoir construction: Case 1. Where the reservoir banks are built on a slope of 3 horizontal to 1 vertical on the inside, and 2 to 1 on the outside. Case 2. Where the slope of the bank is 2 to 1 on the inside, and 1.5 to 1 on the outside. Case 3. Where the reservoir is lined, inside and outside slopes being 1.5 to 1. The reservoirs will be considered to be constructed on level ground, and no allowance will be made in the capacity of the reservoir for dirt which may be excavated from banks below the level of the ground, the lowest plane to which the water may be drawn in the reservoir being con- sidered as that of the ground level. The following notation will be adopted, linear dimensions being in feet: H = vertical depth of reservoir bank. S = 1 divided by inside slope of reservoir. P = 1 divided by outside slope of reservoir. W = crown of reservoir bank. Y = cubic yards of earth in the reservoir. r = radius of inside base of reservoir. r' = radius of reservoir at the top of the water line. InCasel,S = 3 P = 2. In Case 2, S = 2 P = 1.5. In Case 3, S =- P = 1.5. 156 PRACTICAL IRRIGATION. On page 219 in the Appendix is given the method of calcu- lation of reservoir capacities, and of the volumes of earth in embankments. Capacity of reservoir in Case 1 = (r /3 - r 3 ) X (0.00000801) - acre-feet, and the flow in gallons per minute required to fill the reservoir in 24 hours is (r' 3 - r 3 ) X 0.00181. For Case 2, acre-feet capacity of reservoir equals 0.00001201 (r' 3 r 3 ), and gallons per minute required to fill reservoir in 24 hours = (r' 3 - r 3 ) .002715. In Case 3, acre-feet capacity equals 0.00001602 (r* - r 3 ), and the gallons per minute required to fill the reservoir in 24 hours = ( ri _ r s) 0.00362. As the use of small reservoirs in irrigation work is quite extended, several tables have been prepared to aid in the com- putation of capacities of reservoirs and the volumes of earth in the embankments of the same. Two units of capacity are used the acre-foot of water, and the flow in gallons per minute required to fill the reservoir in 24 hours. Reservoir capacity is often conveniently expressed in the hours or days required for the rate of supply to fill the tank. For instance, say the reservoir is required to hold 5 days' continuous supply of a pump delivering 40 gallons per minute. This is equivalent to 200 gallons per minute for one day. Looking in Table VIII, the required capacity is 0.88 acre-foot. Any diameter of reser- voir may be assumed from which the corresponding depth of water may be calculated for a given capacity. Then allowing for a safe distance between the top of the water and the top of the bank, the volume of bank may be figured. In general it will appear that there will be greatly different volumes of earth in the banks for the different depths of water for reservoirs of the same capacity. It is to avoid figuring these quantities that the tables and curves referred to have been given. Table LXVIII gives capacities of various cone reservoirs for each foot in depth. (See p. 205.) Table LXIX gives data with reference to the circular reser- voirs for Case 1. (See page 209.) Table LXX gives corresponding data with Case 2. (See p. 212.) The capacities in Tables LXIX and LXX are calculated on the assumption that the reservoir is filled to the top of the bank and has no clearance. Column 1 gives inside base diameter EARTH TANKS. 157 (2 r) of the reservoir. Column 2 gives vertical depth of reservoir ( H) . Column 3 gives top inside diameter of reservoir. Column 4 gives capacity of reservoir in acre-feet when filled level with the top. Column 5 gives flow in gallons per minute necessary to fill 250 5C -Mjoatity in acre-ft Fig. 32. Reservoir Capacities for Different Water Depths. Case 1. the reservoir in 24 hours. Columns 6, 7, and 8 give cubic yards of earth in embankment, with crowns of 3, 4, and 5 feet respectively. Column 9 gives outside base diameter of reservoir with 4-foot crown. Column 10 gives length of side of inside 8 20C / / 2 s * ^r ^ f / / yX -x^ ^x 1 x x ^^ / / / >^ > -x^" ^^ / / ^x x^^ x^" ^^^ S2, / .X ~x^ ^x" 1 ' tS-. / j /^v x^ ^ -^ ^ x^ n / * / \ ^J . A^X Q^S >\^X ^^^^ / / - V C^ S^ / / / / S ^ r / r j / ^ ^S^ I / / / s ^x^ x 1 j / / -^x ' / / rxx / / / / / /s 1 / /// f 02 //s W. // ^ ^ /<3 , ^. v ^^ cafxtcifi/ z/? acre -ft. Fig. 33. Reservoir Capacities for Different Water Depths. Cose 1. base of equivalent square reservoir. Column 11 gives length of side of top inside of equivalent square reservoir. Column 12 gives length of base outside of equivalent square reservoir, with 4-foot crown. Figs. 32 and 33 represent graphically the capaci- 158 PRACTICAL IRRIGATION. ties in acre-feet of reservoirs of various base inside diameters and depths of water. Each curve in these figures, which represent part of Table LXIX, Case 1, is drawn for a given depth of water in the reservoir, and represents the relation existing 250 jf 5 V capacity 7/7 acre-fl Fig. 34. Reservoir Capacities for Different Water Depths. Case 2. between the inside base diameter and the capacity of the reservoir in acre-feet. As an example of the use of these curves, suppose that it was desired to build a reservoir with a capacity of 2.5 acre-feet with a depth of 5 feet of water. Looking along * I Wtf ? 200 // M- W z~z /o so capacity in acre-ft' Fig. 35. Reservoir Capacities for Different Water Depths. Case 2. the vertical line representing 2.5 acre-feet in capacity, note the point at which it crosses the curved line representing a reservoir 5 feet in depth. The corresponding inside base diameter of the reservoir is 151 feet. Should it be desired to build this reservoir EARTH TANKS. 159 to the water depth of 4 feet, similarly the inside base diameter of the reservoir would be 175 feet. Figs. 34 and 35 show similar curves for Case 2. Figs. 36 and 37 represent graphically the relation existing eso 00^ ,,3000 . 5000 QOOQ. qr earc/i (n emoanxmefJi Fig. 36. Capacities and Volumes of Embankment. Case 1. between the inside base diameter and the cubic yards of earth in the embankment in the circular reservoir for Case 1, the crown being 4 feet. The straight lines running diagonally across the sheet represent the relation existing between the inside base eoo - egop . i/ooo . /woo . of eart/i in embankment Fig. 37. Capacities and Volumes of Embankment. Case 1. diameter and the cubic yards of earth in the reservoir embank- ment for various depths of embankment. Thus, for example, if it were desired to tell the cubic yards of earth in the em- bankment of a reservoir 500 feet inside base diameter and 5 feet 160 PRACTICAL IRRIGATION. deep, follow the diagonal line representing 5 feet in depth until it crosses the horizontal line marked 500. The horizontal dis- tance of this line from the zero vertical line represents the 00 \TTVI7 O 500 1000 1500 , 2OOQ, ' SfOQ , 3OOQ <3$00 OOO cu,^icf. < s 1 / / ^ ent Fig. 44. Capacities and Volumes of Embankments. Case 2. use to which the reservoir is to be put will largely modify the best proportions of diameter and base for a given capacity, the proper dimensions being arrived at only after thorough con- siderations of all the various features of the case. For example, evaporation from reservoirs will preclude the use of shallow construction, provided the water must be retained in the reser- voir for a considerable period of time. The value of the land also necessitates economy in the area occupied by the reservoir, and calls for deeper reservoirs than would otherwise be advisable. /:.!/,' 777 TAXKS. 165 Where the clearance is 3 feet and is taken as a constant the most economical depth of water in the reservoir is 1.23 feet in Case 1, and 1.3 feet in Case 2. A study of the curves of Figs. 36 to 39, however, indicates that considerable variation may be made in the depth of reservoirs of given capacity without affecting to any great extent the total volume of earth in the embankment. The table of minimum volumes of earth is chiefly useful as a guide in determining the relative cost of reservoirs of given capacity. Table LXXI, page 215, and Fig. 42 indicate the relation existing between the capacity in acre-feet and the depth of water in large circular reservoirs in Case 1. The values in Case 2 are very nearly the same for reservoirs of such large capacity. Fig. 43 represents the relation between diameter volumes of embankment, depth, and capacities of large reservoirs, Case 1 allowing for clearance of 3 feet, and Fig. 44 represents corre- sponding relations for Case 2. CHAPTER XIV. LARGE ARTIFICIAL RESERVOIRS. THERE are many localities in the country where for part of the year large amounts of water go to waste. Where no natural reservoir site is obtainable, often no practical consideration has been devoted to the idea of the construction of large reser- voirs on level ground for the storage of this water for irrigation. A study of the problem of construction of earth reservoirs on level ground brings out the fact that where the ground is suit- able for reservoir construction extensive developments can be made along lines of this nature. It brings out, however, most prominently the importance, from a financial standpoint, of undertaking on a large scale the construction of extensive reservoirs. While it is true that large areas, miles in extent, cannot usually be obtained on level ground, still the cost of construction with a moderate slope is little in excess of the cost on level ground. And the figures of reservoir construction here- with presented indicate that it is well worth considering and investigating thoroughly the problem of the construction of almost the entire reservoir embankment, utilizing at the same time whatever natural advantages may be found in the location of the site. In problems of this nature it is particularly important to figure carefully all the various items affecting reservoir con- struction, probable supply of water, and season thereof, evapo- ration, seepage, and the needs of the land for irrigation. Also cost of construction of embankment and of riprap. Upon mak- ing the necessary assumptions of these quantities, mathematical expressions can be derived from which it is possible to determine the proportions of the reservoir which will give a minimum annual cost for any given number of acre-feet output of reservoir. The following notation will be used for reservoir calculations, all linear dimensions being in feet, and all costs in dollars. 166 1. .\ /:<,!: ARTIFICIAL ///>/; WO/flS. 167 A = acre-feet capacity annually available for irrigation after allowing for seepage and evaporation. B+b + g-k. C=b+g + d-c-k. D = total annual cost = interest on and depreciation and main- tenance of reservoir + cost of water supplied to the same. E = - = cost per acre-foot of water supplied from reservoir. H = Depth of bank. 1 p = slope of outside bank slope of inside bank r (P + S) 2 R = ioo ' W ' = crown of bank. 6 = clearance. c = depth in reservoir of annual evaporation and seepage. d = annual rainfall. g = depth in reservoir of evaporation + seepage loss during the irrigation season, i = annual rate of interest. k = depth of water supplied to the reservoir during irrigation season. I = cost per acre-foot of water delivered to the reservoir, m = cost of riprap per square foot. n = cost of construction of embankment per cubic yard. p = per cent annual interest and depreciation and mainte- nance of the reservoir complete. r = inside radius of reservoir. v = cost of land per acre. q = an assumed constant. Width of belt of riprap = S(H - q), will be assumed in some cases. The annual depth of water output from the reservoir = H -b-n + j c =H-B. 168 PRACTICAL IRRIGATION. Annual depth of water which must be supplied from sources other than rainfall to the reservoir = H b d g + c + k = H -C. It is assumed that there is no rainfall during the irrigation season. In the appendix, page 220, is given in detail a mathe- matical treatment of the method of obtaining the most economical proportions of the reservoir for minimum annual cost per acre- foot output. In the consideration of the problem it may be stated as a general rule that evaporation losses will be greatest during the irrigation season, also during this time there will be, in all probability, periods when a limited amount of water can be supplied to the reservoir from the source of supply, though the amount which can be furnished at such time may be materi- ally less than that which can be supplied during the remainder of the year. To illustrate the results of the application of the methods of reservoir designs cited, the following assumptions will be made: W = 4; b = 3; c = 6; d = 2; g = 4; p = 0.10; i = 0.07; k = 1; q = 5; hence, B = 6; C = 2. These assumptions mean that the annual evaporation and seepage is 6 feet. The evaporation and seepage during the irri- gation season is 4 feet; the annual rainfall 2 feet, and the depth of water supplied to the reservoir from the source of supply during the irrigation season, 1 foot, no rainfall being supposed to furnish water during that period. The following additional assumptions will be made: Cost of earthwork = 10 cents per cu. yd., which will hold for short hauls and where labor is cheap. The cost of riprap = 27 cents per sq. yd., or n = 0.1 ;m = 0.03. Under these assumptions the following four cases will be considered. Case 1-a. I = $0.25 = cost per acre-foot of water furnished to reservoirs; v = $5 = cost per acre of land; S = 3; P = 2; T = 2.5 feet. Case 2-a. The assumptions I = $0.25; v = $5; S = 2; P = 1.5 feet; T = 1.75. Case 1-b. I = $2; v = $30; S = 3; P = 2; T = 2.5. Case 2-b. I = $2; v = $30; S = 2; P = 1.5; T = 2.5. Several other cases of reservoir construction will be calculated, the assumed data being given in Table LXVII, p. 203. LARGE ARTIFICIAL RESERVOIRS. 169 Tables XXXIV, XXXV, XXXIX and XL and curves in Figs. l.~>, -\(\, 47 and 4S show the result of these calculations. There are many places in the country where all expenses for pumping water up to a head as high as 80 feet should be covered by a charge of $2 per acre-foot, provided that stations with an out- put of about 10 cubic feet per second be operated for about half the time. A cost of $30 per acre for land is sufficient to cover most cases to be considered, so the conditions of Case b may be assumed to represent an extreme case covering the cost of pumping water into a reservoir where the supply is abundant about half the year, mainly when not needed for irrigation. \Yliile the results given in the tables, and the curves represent the best proportions of the reservoir, still, should local con- ditions demand for any reason, such as the lay of the land, the relative dimensions of reservoir may be altered quite widely without materially increasing the annual cost of water. The curves shown in Figs. 45 to 48 are of four kinds. Curve No. 1 represents the relation between the inside diameter of the reservoir and the output capacity in acre-feet. Curve No. 2 represents the relation between the inside diameter and the depth of embankment. Curve No. 3 represents the relation between the inside base diameter and the cost of construction of reservoir and riprap per acre-foot output capacity, and curve No. 4 represents the relation between the inside diameter and the annual cost per acre-foot output of reservoir. For example, if it were desired to have a reservoir delivering 1380 acre-feet of water per year, in Case 1-&, follow out the horizontal line marked 1380 acre-feet to a point where it crosses Curve No. 1, the point of intersection will be at a horizontal distance representing 3000 feet. Follow this vertical line to a point where it crosses Curve No. 4. The vertical distance of this point from the zero line shows that the cost of water is $5.25 per acre-foot. This is less than one-third the actual cost in many localities where irrigation has been successfully carried on. To compare this with other costs, the cost of distribution of this water to various farms should be added. In certain localities, where the water supply is lim- ited, the average cost of gasoline alone for pumping is $13 per acre-foot. Water supplied from city pipe lines costs from $48 t<> siO per acre-foot. The amount of water needed for the irri- gation of land depends largely on the method of distribution. tooo 2$0 20<% 20000 so^sooo 000 6OOQ 80QO . _./ inside diet, of reservoir in ft. /WOO Fig. 45. Economic Reservoir Dimensions and Costs. Case la. WOO. , . 6OOQ BOQO . M inside <2ia. i:uneter "1 reservoir, I-'.-, -t. Depth of embankment, Feet. Output capacity, Acre-ft. t^o&t or \\ :iter per acre-ft. output reservoir per acre-ft. output capacity Reservoir efficiency, Per cent 400 9.20 9.25 $22 .85 $177 .00 44 800 10.30 49.70 12.52 81 .70 52 1,200 11.70 136 .80 9.18 52.60 59 1,600 12.15 283.50 7.53 38 .90 61 2,000 12.90 500.00 6.55 30 .90 63 3,000 14 .50 1,380 .00 5.25 20 .60 68 4,000 16.30 2,970 .00 4.56 15.80 72 6,000 19.00 8,410 .00 3.88 11 .00 77 8,000 21.30 17,650 .00 3.41 8.50 80 12,000 25.30 50,200 .00 3.13 6.10 83 16,000 28.50 104,100 .00 2.94 4.90 85 20,000 31 .50 184,500 .00 2.81 4.20 87 TABLE XXXVI. / Case Ic. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 2,000 12.20 303. $6.08 $55 .10 51 4,000 12.80 1,384. 3.14 26.10 55 6,000 13.31 3,450 . 2.17 16.70 57 8,000 13.88 6,785 . 1 .70 12.20 60 12,000 14.87 17,820 . 1.22 7.70 63 16,000 15.80 38,150 . .98 5.60 66 20,000 16.65 62,300 . .85 4.40 68 TABLE XXXVII. Case Id. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 2,000 8.84 205. $4.42 $36.90 42 4,000 9.74 1,075. 2.32 17.10 48 6,000 10,58 2,970 . 1.65 11 .03 53 8,000 11 .41 6,240 . 1.32 8.16 58 12,000 13.00 18,180 . .99 5.49 64 16,000 14.40 38,700 . .84 4.25 68 20,000 16.10 72,900 . .74 4.25 72 176 PRACTICAL IRRIGATION. TABLE XXXVIII. Case le. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR - 25 CENTS. Cost of Cost of Diameter of reservoir, Feet. Depth of embankment, Feet. Output capacity, Acre-ft. water per acre-t't. output reservoir per acre-ft. output capacity Reservoir efficiency, Per cent 2,000 12.25 306. $6.07 $55 .00 52 4,000 12.84 1,395. 3.15 26.17 55 6,000 13 .53 3,580 . 2.17 16.75 58 8,000 14.24 7,200 . 1 .67 11 .99 61 12,000 15.60 19,720 . 1.22 7 .89 66 16,000 17.00 41,400. .98 5.79 69 20,000 18.40 74,600 . .86 4.76 72 TABLE XXXIX. Case 2a. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 400 8.27 6.53 $14 .49 $146 .40 36 800 8.52 29.10 7.78 69.90 39 1,200 8.75 71.90 5.23 44.90 41 1,600 9.00 138 .30 3.96 32.60 43 2,000 9.25 232 .70 3.22 25.50 45 3,000 9.76 610 .00 2.22 16.10 49 4.000 10.26 1,229.00 1 .74 11.70 52 6,000 11 .19 3,365 .00 1 .26 7.50 56 8,000 12.03 6,950 .00 1 .03 5.60 60 12,000 13.52 19,500 .00 .79 3.60 65 16,000 14.85 40,750 .00 .68 2.80 69 20,000 16.02 72,350 .00 .60 2.20 72 TABLE XL. Case 2b. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR $2. 400 10.03 11 .64 $16 .49 $119.90 50 800 11 .15 59.70 9.61 56.60 56 1,200 12.38 166 .00 7.26 36.80 61 1,600 13.45 346 .00 6.10 27.50 65 2,000 14.48 613 .00 5.39 22.00 68 3,000 16.70 1,735.00 4.44 14.90 73 4,000 18 .50 3,632 .00 3.94 14.90 76 6,000 22.20 10,520 .00 3.44 8.20 80 8,000 24.70 21,600.00 3.17 6.30 83 12,000 16.97 61,050.00 2.89 4.60 86 16,000 19.85 127,000 .00 2.76 3.90 88 20,000 22.45 224,500 .00 2.64 3.10 89 LARGE ARTIFICIAL RESERVOIRS. 177 TABLE XLI. Case If. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. Diameter of reservoir, Feet. Depth of embankment, Feet. Output capacity, Acre-ft. Cost of water per acre-ft. output Cost of reservoir per acre-ft. output capacity Reservoir efficiency, Per ceut 400 9.95 11 .4 $51 .49 $423 450 800 10.02 46.4 25.99 222 50 1,200 10.13 107.2 18.31 147 .70 51 1,600 10.17 192 .5 13.09 104.30 51 2,000 10.27 308.0 10.50 82.80 52 3,000 10.52 733.5 7.06 54.20 53 4,000 10.81 1,388 5.34 40.05 55 6,000 11.58 3,564 3.64 26.20 58 8,000 12.24 7,216 2.81 19.50 61 12,000 13.97 20,700 2.01 13.25 67 16,000 15.87 45,500 1.64 10.42 71 20,000 17.85 85,600 1.43 8.92 75 TABLE XLII. Case Ig. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR $2. 400 10.31 12.44 $63 .53 $493 52 800 10.72 54.6 28.21 201 54 1,200 11.14 133.5 17.21 127.20 56 1,600 11.52 254.6 14.99 93.20 58 2,000 11.88 425 12.46 73.10 60 3,000 12.80 1,104 9.15 47.25 63 4,000 13.63 2,204 7.51 35 66 6,000 15.22 5,980 5.88 23.08 70 8,000 16.71 12,370 5.07 17.75 73 12,000 19.72 35,600 4.25 12.67 77 16,000 22.12 74,500 3.85 10.25 80 20,000 24.68 134,800 3.61 8.92 82 TABLE XLIII. Case Ih. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 400 12.64 13.4 $62.49 So 1C) 54 800 12.71 54.4 31 .31 257 54 1,200 12.79 124 20.82 170 55 1,600 12 .86 224 15.73 126.6 55 2,000 12.96 358 12.60 100.6 55 3,000 13.22 848 8.44 66.1 56 4,000 13.55 1,596 6.37 48.8 58 6,000 14.31 4,095 4.08 30.2 61 8,000 15.19 8,288 3.28 23.7 64 12,000 17.27 24,100 2.30 15.9 70 16,000 19.61 53,600 1 .86 12 .4 74 20,000 22.06 101,500 1.62 10.6 78 ITS PRACTICAL IRRIGATION. TABLE XLIV. Case li. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR $2. Cost of Cost of Diameter of reservoir, Feet. Depth of embankment, Feet. Output capacity, Acre-ft. water per acre-ft. output reservoir per acre-ft. . output capacity Reservoir efficiency, Per cent 400 14.9 25.3 $41 .18 $380 69 800 18.0 138 24.20 214 75 1,200 20.5 377 18.35 157 78 1,600 22.8 775 15 .29 127 81 2,000 24.8 1,356 13 .37 108.3 82 3,000 29.2 3,750 10.68 82.4 85 4,000 32.9 7,752 9.24 68.7 87 6,000 39.2 21,600 7.66 53.6 89 8,000 44.6 44,600 6.80 45.4 90 12,000 54.0 124,600 5.79 35.8 92 16,000 61 .9 258,000 5.24 30.6 93 20,000 69.0 455,000 4.87 27.1 94 Case 4a. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 400 8.1 5.9 $20.78 $198.70 34 800 8.3 26.7 8.83 79.90 38 1,200 8.6 66.6 5.89 51.10 39 1,600 8.8 129.8 4.47 37.40 41 2,000 9.0 219 3.65 29.50 43 3,000 9.6 583 2.53 18.00 47 4,000 10.1 1,178 1.99 14.10 51 6,000 11.0 3,260 1.45 9.30 56 8,000 11.9 6,775 1.18 7.00 60 12,000 13.4 19,200 .91 4.70 65 16,000 14.5 39,250 .78 3.70 68 20,000 15.8 70,800 .70 3.10 71 Case laa. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR 25 CENTS. 400 8.6 7.6 $22.70 I $219.30 39 800 8.9 32.2 11.40 106.60 41 1,200 8.9 ' 76.2 7.66 69.50 42 1,600 9.1 143.0 5.77 50.80 44 2,000 9.3 236 4.65 39.90 45 3,000 9.6 590 3.17 25 50 47 4,000 10.0 1,156 2.44 18.50 50 6,000 10.7 3,042 1.73 11.90 53 8,000 11.3 6,128 1.36 8.60 57 12,000 12.4 16,620 1.02 5.70 61 16,000 13.5 34,560 .85 4.20 65 20,000 14.4 60,800 .74 3.30 68 LARGE ARTIFICIAL RESERVOIRS. 179 One other case (No. 4a) of reservoir construction will be con- sidered based on certain data compiled by Professor Fortier, which the following statements will explain. The general assumptions of this case are similar to those in Case la, except that the side slopes and widths of embankment at top are different, as will be explained. As has been pointed out, the proper section of the banks of earth reservoirs depends on the depth of water, exposure to winds, and on the material of which the embankment is com- posed. The inner and outer slopes must not be so steep that they will not stand up under the action of waves or of the ele- ments. The top of the embankment must have sufficient clearance above the water plane not to allow the waves to wash over it. The particular conditions of each case should be given individual consideration. It is well to take into consideration the practice in existing earth reservoirs. In bulletin No. 46 of the Agricultural College Experiment Station at Logan, Utah, Prof. S. Fortier gives some interesting figures on earth embankments for reservoirs. From 75 typical earth reservoirs, the following figures were obtained : The inner slopes varied from 4: 1 to 1: 1, averaging 2.61: 1. The outer slopes averaged 2.1: 1. The following table gives a summary of these results: SLOPE OF RESERVOIR EMBANKMENTS. No. of Reservoirs Outer Slope No. of Reservoirs Inner Slope 2 1: 1 2 1: 1 23 1-i: 1 23 H: 1 2 2 lf:l 41 2: 31 2:1 1 2-i: 1 2-4:1 3 2-i: 1 2-f:l 3 3: 11 3: 1 Average 2.1: 2 4: 1 Average 2.61: 1 From the same reservoirs it is deduced that the thickness in feet of embankment at the high water line is 5 plus the depth of water in the reservoir. In Case 4a the following assumptions are made: S = 2.61, p = 2.1, W = H + 5 - 26T 7 , 6=3. In the practical construction of an earth embankment, Pro- fessor Fortier advocates the use of a core wall. A very effective 180 PRACTICAL IRRIGATION. TABLE XLV. Case 3k. COST PER ACRE-FOOT SUPPLIED TO RESERVOIR $2, Diameter of reservoir, Feet. Depth of em- bankment, Feet. Output capacity, Acre-ft. Cost of water per acre-f t. output 400 800 1,200 1,600 2,000 3,000 4,000 6,000 27.5 37.7 45.4 52.1 58 70.3 80.8 98.5 65 378 1,050 2,175 3,820 10,620 21,880 60,750 $47 .20 29.36 23.10 19.66 17.45 14.20 12.40 10.32 TABLE XLVI. Case 31. LINED RESERVOIRS CONSTRUCTED FOR MINIMUM FIRST COST. Mean diam- eter bank, Feet. Depth of bank, Feet. Acre-ft. capacity Cost per acre-t't. Total cost 40 4.49 .0487 $1,232 $60 80 6.13 .395 551 217 120 7.40 1.23 381 468 160 8.45 2.69 300 808 200 9.42 4.94 252 1,245 300 11 .45 14.48 187 2,730 400 13.13 30.70 156 4,785 TABLE XL VII. Case 3m. 40 5.45 .038 $1,906 $73 80 7.00 .352 698 246 120 8.23 1 .141 453 515 160 9.28 2.54 347 882 200 10.20 4.67 287 1,339 300 12.22 13.9 209 2,900 400 13.90 29.7 169 5,028 method of building the center of the embankment is to keep the central portion during construction lower than the two sides, so as to leave a small ditch in the center. This is kept partially full of water; during the day the water is quite low, not to interfere with working, and at night the water level is raised. The construction of an embankment impervious to water involves in the main, the proper arrangement of various sizes of soil grains, the effective filling of interstices, the consequent LARGE ARTIFICIAL RESERVOIRS. 181 TABLE XLVIII. COST OF RESERVOIR CONSTRUCTION PER ACRE-FOOT- AMERICAN RESERVOIRS. (Taken from Schuyler's " Reservoirs for Irrigation, Water Power and Domestic Water Supply.") No. Name Character of dam Capacity of reservoir, Acre-ft. Cost Cost per acre-ft. 1 2 3 4 6 7 Sweet water dam, Cal. Bear Valley dam, Cal. Hemet dam, Cal. . . Escondido dam, Cal. La Mesa dam, Cal. . Cuyamaca dam, Cal Masonry .... Masonry .... Masonry .... Rock-fill .... Hydraulic-fill . . Earth . . . 22,566 40,000 10,500 3,500 1,300 11,410 $264,500 68,000 150,000 110,059 17,000 54,400 $11.72 1.70 14.29 31.44 13.10 4 76 g Buena Vista Lake, Cal Earth . ... 170,000 150,000 88 10 11 12 13 14 15 16 17 18 English dam, Cal. . Bowman dam, Cal. . San Leandro dam, Cal. Eureka Lake dam, Cal. Fancherie dam, Cal. Lake Avalon, Pecos River, N.M. Lake McMillan, Pecos River, N.M. Tyler, Texas . . . Cache la Poudre Col Rock-fill crib . . Rock-fill crib . . Earth Rock-fill .... Rock-fill .... Rock-fill and earth Rock-fill and earth Hydraulic-fill . . Earth 14,900 21,070 13,270 15,170 1,350 6,300 89,000 1,770 5 654 155,000 151,521 900,000 35,000 8,000 176,000 180,000 1,140 110 266 10.40 7.19 68.00 2.32 5.92 27.94 2.02 .64 19 50 19 Larimer and \Veld, Earth 11 550 89,782 7 77 20 21 Col. Windsor, Col. . . . Monument, Col Earth Earth 23,000 885 75,000 33,121 3.26 38 69 22 23 Apishapa, Col. . . . Hardsc rabble Col Earth Earth 459 102 14 772 9 997 32.18 97 78 ?4 Boss Lake, Col. . . Earth 205 14,654 71 .39 ?f> Saguache, Col. . . . Earth 954 30,000 31.45 26 27 Seligman, Ariz. . . . Ash Fork, Ariz Masonry .... Steel .... 703 110 150,000 45,776 169.50 416 30 28 29 30 31 Williams, Ariz. . . Walnut Canon, Ariz. New Croton, N.Y. . Titicus, N.Y. . . . Masonry .... Masonry .... Masonry and earth Masonry and earth 338 480 98,200 22,000 52,838 55,000 4,150,573 933,065 156.35 114.60 42.27 42.42 32 Sodom NY Masonry and earth 14,980 366,990 24 50 W Bog Brook N Y Earth 12,720 510,430 40.12 34 35 Indian River, N.Y. Wigwam, Conn. . . Masonry and earth Masonry .... 102,548 1,028 83,555 150,000 .81 145.90 Total 730 012 9 296,439 Average 12.71 Mean capacity 22,100 Average capacity exclusive of No. 8, 17,500 acre-feet. Average cost per acre foot exclusive of No. 8, $16.32. 182 PRACTICAL IRRIGATION. TABLE XLIX. DATA CONCERNING AMERICAN RESERVOIRS. Rated Name Surface area, Acres Maxi- mum height, Feet Rated capacity, Acre-ft. Corrected capacity, Acre-ft. Cost per acre-ft. corrected capacity capa- city, divided by surface area, Feet 1 Sweetwater . . . 895 76 22,566 19,881 $13.30 27.0 2 Bear Valley . . . 3,300 80 40,000 30,000 2.20 12.0 3 Hemet 738 150 10,500 8,286 18.05 14.0 4 Escondido . . . 285 110 3,500 2,645 41.70 12.0 5 Lower Otay . . . 1,414 150 42,190 37,948 30.0 6 La Mesa .... 70 140 1,300 1,090 15 '.60 19.0 7 Cuyamaca . . . 8 Buena Vista . . 959 25,000 35 10 11,410 170,000 8,533 95,000 5.50 1 .56 13.0 6.8 12 San Leandro . . 715 170 2,145 13,270 74.20 19.0 expulsion of the air therefrom, and the protection of the banks from extreme drought or saturation. Professor Fortier con- siders that the construction of the embankment as outlined gives most satisfactory results, since there is no method of .^^, 000- 3000 WOO . 5000^ output capa'citj/ in acre-ft Fig. 49. First Costs of Artificial and Natural Reservoirs. arrangement and compacting of the soil grains, which will give results superior to those attained by the use of water. Table XL VIII, which shows the cost of American reservoirs, LAR<;E . i R n FK 7. t /, KESER voutx. 183 makes no allowance, however, for loss by evaporation. In the majority of natural reservoirs the storage capacity per foot of depth increases very rapidly toward the highest water level, the lower part of the reservoir being of comparatively little value as a storage basin. In consideration of the evaporation we would be more nearly correct if we assume the top area as subject to evapo- ration rather than the area obtained by dividing the total capacity stored by the maximum depth. Since the greater part of the s eve slope 2 Fig. 50. First Cost of Artificial and Natural Reservoirs. storage is in the upper part of the reservoir a much greater sur- face will be presented for evaporation during the greater part of the time. In order to correspond as closely as possible with the basis of figures for earth reservoirs, Table XLIX has been calcu- lated, assuming that the actual reservoir capacity for storage is diminished by 3 feet times the surface area of the reservoir. In Table XLIX is also given a column showing the quotient arising from dividing the rated reservoir capacity by the surface area. Figs. 49 and 50 show the relation between the cost of reservoir construction per acre-foot output and the output capacity of the reservoir in acre-feet. The curves are drawn for Cases l,-a-c-d-e-f-g-h. On the diagrams are also plotted points representing the relation between the cost of reservoir 184 PRACTICAL IRRIGATION. construction per acre-foot and the reservoir capacity as given in Schuyler's tables, these points being denoted by black points surrounded by small circles and numbered to correspond to the numbers in the table. In the cases in which surface areas are given (Table XLIX) , points are also given denoting the relation between the reservoir output capacity and the cost per acre- foot output. These points are denoted by small crosses. Several points are not plotted on the diagram, as they are far beyond the range, owing to very high cost of construction. It will be noted that the greater part of the natural reservoirs exceed considerably in cost per acre-foot the cost of construc- tion of earthen reservoirs of corresponding size. On the dia- gram is also given a point marked " average, " which indicates the relation between the average size of reservoirs in Table XL VIII as determined by dividing the gross capacity by the number of reservoirs, and the average cost per acre-foot as determined by dividing the total cost by the total number of acre-feet. This point indicates that in round numbers these reservoirs cost 2.5 times as much as corresponding earthen reservoirs in Cases 1,-a-d, and about 80 per cent more than cor- responding reservoirs in Cases ^,-~ e j an( l about the same as Case I/. It is to be noted particularly that in the cases assumed for earth reservoirs no allowance whatever has been made for taking advantage of the natural lay of the land in aiding in obtaining storage capacity. Where an artificial reservoir several square miles in area is to be built, it will undoubtedly be possible in many cases to obtain very material advantage by the use of natural sites, contributing greatly to the reservoir storage capacity. In fact, should the irrigable land lie in such a way that only part of the reservoir could be used for gravity irrigation, it might easily pay to install a pumping plant for taking water from the low r er part of the reservoir rather than to construct a reservoir of considerably greater depth. A general study of reservoir construction by means of earthen embankments brings out the importance from a construction standpoint of comparatively shallow reservoirs, thus leading to considerable percentage losses by evaporation. In round numbers, in the great majority of cases considered, earthen reservoirs will lose 20 to 60 per cent of the water which flows into them, whereas LARGE ARTIFICIAL RESERVOIRS. 185 the natural reservoirs referred to will lose but 15 to 30 per cent of their water from this same cause. Where the percentage of evaporation losses is considerable, it is important that the reservoir be made of such a size that there will be an ample supply of water to fill it during the season, for obvious reasons. It would appear that the construction of earthen reservoirs, if the attendant conditions have been carefully studied, should prove a most important aid in the development of the country. Many of the natural reservoirs have been constructed with masonry dams at an exceedingly high cost per acre-foot of capacity. The type of construction employed is often largely governed by the conditions of service to which the dam will be subjected, such as excessive floods, necessitating the best kind of construction. Even then it is not uncommon for floods of extraordinary violence to do considerable damage to dams. These points must be taken into consideration in allowing a suitable figure for depreciation. An earthen reservoir, on the contrary, in most cases may be constructed where the danger from floods is practically absent, and where, if conditions are at all favorable, sedimentation of the reservoir may be largely avoided by means of proper sand traps in the supply canal. In some cases, however, earthern reservoirs are so located that it is difficult to afford them complete protection against the danger of floods without incurring great expense. For eco- nomic reasons, earth reservoirs are usually constructed of the material near at hand. The proper dimensions of the banks will depend largely on the nature of their composition, and a suitable design calls for the exercise of good engineering judg- ment. Earth embankments should preferably be constructed with the coarser material near the outer edge, so that whatever water seeps through, the inner side of the embankment will drain away readily, and not saturate the entire embankment, and render it liable to slip. The more impervious material should be arranged in the center, or nearer the inner side. A core wall in the center of an embankment adds a large factor of safety, protecting against gophers, and other burrowing animals, and adding materially to the imperviousness to water, and con- sequent diminution of both the loss by seepage and risk of failure. Puddle is usually used for such a purpose, though often a concrete wall, two or three feet thick, is employed. 186 PRACTICAL IRRIGATION. No reservoir is immune from the danger of damage, and unprecedented conditions of rainfall, etc., have in some cases wrought considerable damage to such structures. Failures have occurred in dams and embankments of all descriptions, due either to conditions difficult to foresee, or to faulty con- struction. In properly designed dams, where the attendant conditions have been thoroughly studied, the danger of failure is exceedingly small. It is probable that a properly constructed masonry dam offers less danger of failure than a well built earth embankment. Of course in reservoirs built entirely in embank- ment, the greatly increased length of embankment adds to the chance of failure. Experience with the large number of earth reservoirs indicates that when conditions are at all favorable, when the construction is good, and when precautions are taken to prevent the water exceeding the proper depth, this type of construction is reliable, and is of great economic benefit. CHAPTER XV. LARGE RESERVOIRS FOR THE STORAGE OF ARTESIAN WATER. THE conditions governing the supply of water from an artesian well are different in many respects from those governing the supply of river or rain water, and in consequence reservoir construction to retain part of this supply for irrigation requires special consideration of the various features of the case. In the case of artesian wells, the flow of the water may be considered as practically constant. This does not mean that in one year it may not be somewhat different from its value in another year, due to the possible causes enumerated; but for any con- siderable period, the output of the wells when the water supply is under considerable head may be regarded as uniform, provided that excessive development of wells does not affect the water pressure. The possible effect of this contingency should always be taken into consideration when planning a storage reservoir for artesian wells. In most places where artesian wells occur, there are practi- cally no natural reservoir sites available, and in order to store water the entire reservoir must be constructed artificially. In many districts wells were originally sunk for a supply of stock water, and the flow from them has in some places formed large, shallow pools totally unsuitable for irrigation purposes, due to the elevation being lower than the surrounding land, the shallow depth also presenting an unduly great surface for evaporation. The question to be solved by the irrigator is, What capacity, and what size and dimensions, would it pay to make the reser- voir for the storage of artesian well-water when the supply comes from a well delivering a given flow? As the entire flow of the well may be obtained at no greater cost than part of the supply, the natural suggestion is to build a reservoir of sufficient capacity to retain the output of the well between irrigation seasons. There are many practical limitations to the size of 187 188 PRACTICAL IRRIGATION. reservoirs for wells, since on the one hand evaporation and seepage play a most important part in determining the dimen- sions of the reservoirs, tending to call for a greater depth of water; and on the other hand, if the reservoir is made exceed- ingly deep, the additional depth against which the well has to operate may cut down very materially the discharge. This suggests one important point about artesian wells, namely, that the discharge of the well should be subjected to as little hydrostatic pressure as possible. Artesian pressure will raise the water without flow to a certain height above the ground level, known as the static head. If this static head is large, a few feet additional pressure against the well will not have a great effect on the discharge; but should the static head be com- paratively small, the additional pressure of a few feet of water will materially affect the output. The pipe supplying water to the reservoir should not be taken over the top of the embank- ment to let the water fall into the reservoir. Rather take it into the lower part, in order that the maximum pressure operat- ing against the artesian flow may be as small as possible for as long a time as possible. Also in this same connection, an outlet should be provided from the well on to the ground direct, and a valve inserted to cut off the reservoir from this pipe, so that when it is desired to irrigate, the well water will be delivered under a still lower hydrostatic pressure than if it were necessary to overcome the difference in elevation between the ground and the top of the water in the reservoir. At the same time, the reservoir water can be added to the water from the well, and used in irrigation. In the consideration of the problem of reservoir dimensions for artesian wells, the assumption will be made that during the irrigation period there will be a certain time during which the well supply which will not be used directly on the ground for irrigation, owing to rainfall or other causes, will be stored in the reservoir. In order to simplify the problem, which would otherwise be quite complicated, further assumption will be made that the flow of the well is constant and is not affected by the static pressure due to the water in the reservoir. The problem to be solved, then, is: Under these conditions what size and con- struction of reservoir will give the cheapest total annual cost of all water used for irrigation, including both the output of the STORAGE OF ARTESIAN WATER. 189 reservoir and the water from the well which is used directly on the land? Obviously the construction of a reservoir will depend on many considerations, among which are the flow of the well, the annual cost of the well per gallon per minute, the irrigation factor without the use of the reservoir, the season of the year during which irrigation is desired, seepage and evapora- tion, rainfall, as well as the cost of construction of the reservoir itself. For a consideration of this last item it is first necessary to determine the cost per acre-foot of the well water supplied from the well. The flow of 1 gallon per minute will deliver 1.612 acre- feet ,per year. In estimating the cost of water furnished by an 35 n 1 \& . 6, cost f>er- acre-/c. .6 otfc. 10 Fig. 51. Cost of Well Water per Acre-foot. artesian well, the method to be followed is to figure first the cost of the well per gallon per minute, as already outlined, and then to assume twelve per cent per year on the investment to be the cost of obtaining water from the well. Multiplying the cost of well per gallon per minute by 0.12 gives the annual cost per gallon per minute. Dividing the result by 1.612 gives the cost per acre-foot of water. Without storage, well water is used for only a limited portion of the year. The irrigation factor for the well represents the total percentage of time when the well water is in use. The cost per acre-foot just mentioned, refers to the 100 per cent irrigation factor. To ascertain the cost of the well water for any other irrigation factor, divide this cost by the irrigation factor. Fig. 51 and Table L give a tab- ulation and graphical representation of the result of this method 190 PRACTICAL IRRIGATION. of calculation. The annual cost of most artesian wells in Texas per acre-foot of water is between 25 cents and $2. At a 25 per cent irrigation factor this would make the cost of water used without storage between SI and $8 per acre-foot per year. The use of reservoirs as a storage for water has the additional advantage of utilizing to the utmost the resources of the country and of providing water, even though at a rather high apparent cost, which might otherwise not be supplied. Let U equal the irrigation factor without a reservoir, then the quantity of water supplied annually by the well would be repre- H C sented by a depth in the reservoir of and the quantity of water actually used would be represented by H - B + (H - C) 1-U In the Appendix, page 227, is given the mathematical method of arriving at the best section of the reservoir. It is to be noted that this method does not provide the most economi- cal reservoir to retain a given supply of water, but it does provide TABLE L. THE COST OF WELL WATER. Well, $ Cost per acre-ft. per year for irrigation factor cost per gal. per rain. 10O. 50. 40. 30. 25. 20. 15. 10. 1 .07 .15 .19 .25 .30 .37 .49 .74 2 .15 .30 .37 .50 .60 .74 .99 1.49 3 .22 .45 .56 .74 .89 1.12 1.49 2.23 4 .30 .60 .75 .99 1.19 1.49 1.98 2.98 5 .37 .74 .93 1.24 1.49 1.86 2.48 3.72 6 .45 .89 1 .12 1 .49 1.79 2.24 2.98 4.47 7 .52 1 .04 1 .30 1 .74 2.08 2.61 3.48 5.21 8 .60 1 .19 1 .49 1 .99 2.38 2.98 3.97 5.96 9 .67 1.34 1.68 2.23 2.68 3.35 4.47 6.70 a reservoir of such proportions that the total acre-feet of water (A) furnished by the well direct to the ground and by the out- put of the reservoir shall be furnished at a minimum cost, when the cost per acre-foot of water supplied from the well, and also STORAGE OF ARTESIAN WATER. 191 the corresponding capacity of the well are known. In arriving at a solution of this problem, the cost per acre-foot output of the well is taken as the cost at 100 per cent irrigation factor. Tables LI to LVIII illustrate the results of these determina- tions for reservoirs with clearances of 3 feet, and Tables LIX to wo GOO '<$,*** *8?* lase'Sftt. 1200 Fig. 52. Economic Well Reservoirs. Case E2. LX VI illustrate the same thing for reservoirs with 2-ft. clearance. In all cases the cost of the land is taken as $15 per acre. The cost of water supplied by the well in Cases A, C, E, and G is $2, VOO GOO 800 . '.("XL inside dia. cf &ase in ft. Fig. 53. Economic Well Reservoirs. Case G2. and in Cases B, D, F, and H is 25 cents per acre-foot. Cases A, B, E, and F are for reservoirs with banks riprapped, and Cases C, D, G, and H are for banks without riprap. The results in Cases 192 PRACTICAL IRRIGATION. E2 and G2 are illustrated in curves, Figs. 52 and 53. Curve No. 1 represents the relations existing between the reservoir inside diameter and the total capacity, A, in acre-feet. Curve No. 2 represents the relation between the inside diameter and the depth of the embankment. Curve No. 3 represents the relation between the inside diameter and the cost of the reser- voir construction per acre-foot of water used, and No. 4 repre- sents the relation between the inside diameter of the reservoir and the annual cost per acre-foot of the water used for irrigation. Curve No. 5 represents the relation between the inside diameter of the reservoir and flow in gallons per minute of the well supplying the same. These tables are all based on an irriga- tion factor of 25 per cent, annual seepage and evaporation, 6 feet, rainfall, 2 feet, seepage and evaporation during the irrigation season, 3 feet; water supplied from the wells to the reservoir during the irrigation season, 1 foot in depth. Cases 1 and 2 refer to the slopes of the bank, as already outlined. The reservoir efficiency given in Tables LI to LXVI represents the ratio of the water put into the reservoir to that which is taken out. The well efficiency represents total percentage of well water used for irrigation. Line No. 5 represents the flow in gallons per minute of the well to produce a quantity of water available for irrigation in acre-feet represented by line 6. Line 7 gives the percentage of increase of the well due to storage of the water over the available irrigation water without a reservoir. Line 8 gives the total cost of water for irrigation per acre-foot representing the output of the reservoir and the flow of the well on the ground direct. Line 9 gives the cost of the reservoir per acre-foot of water used for irrigation, as defined. The assumption made of the 25 per cent irrigation factor would correspond to an irrigation season about four months in length, the total flow of the well being supposed to be used three-fourths of that time. For the irrigation of a crop like cotton in Southern Texas, it is probable that the irrigation factor would be considerably larger. The cost of water without a reservoir in the cases considered would be $8 per acre-foot for Cases A and C, and SI for Cases B and D. The method of interpretation of the curves given in these figures is similar to that previously given on page 169, and hence will not be repeated. In Case A-l, as given in Table LI //-; OF Ah'TESIAN WATER. 193 we see that allowing a 3-foot clearance, a well delivering 334 gallons per minute could be used to advantage for supplying 355 acre-feet per year by means of a reservoir costing $23.30 X 355. The total cost of the water for irrigation with the reservoir, per acre-foot, would be $5.51 as against $8 without the reservoir, and the reservoir would increase the quantity of water actually used, and hence the land which could be irrigated would be increased 163 per cent. Before undertaking any reservoir construction based on assumptions which have been made here, care should be taken to verify these assumptions and to see that they apply to the particular case considered. It is, of course, evident that large reservoirs like those described will increase materially the available output of the wells, but the same may be done by the use of pumps assisting the artesian flow. In order to enable one to pass judgment on the relative advantage of reservoirs, or of the use of pumps for increasing the flow of wells, it would be necessary to have, first, an under- standing of the law of the flow of water from wells, which may be arrived at as outlined. Generally speaking, pumps may be applied to increase the flow of the wells very materially when the static head above the ground is small, and likewise the head lost in friction in flowing through the pipes. On the other hand, where the static head is large, and lost friction head in the pipes is also large, the pumps cannot be advantageously employed. ECONOMIC RESERVOIRS FOR ARTESIAN WELLS. TABLE LI. CASE A-l. COST PER ACRE-FOOT WELL OUTPUT $2. Diameter of reservoir, ft. . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. . ; 6 .78 7 .93 8.93 9 .77 10 .58 12 .34 13 .85 Reservoir efficiency, per cent 30 .6 42.3 49.6 54 .4 58 .2 64 .7 68 .9 Well efficiency, per cent . . I 48 .0 56.7 59.7 65.8 68 .7 73 .5 76 .7 Flow of well, gal. per min. . 13.8 66.3 178 334 570 1,520 3,070 Total quantity annually use- ful for irrigation, acre-ft. . 10.7 60.5 171 355 &32 1,802 3,790 Increase over what well 92 127 149 163 175 194 207 would irrigate without res- ervoir, per cent Total cost of water irrigation Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. with reservoir, per acre-ft. 14.66 8.40 6.49 5.51 4.90 4.10 3.68 Cost of reservoir per acre-ft . of water used for irrigation . 102 .10 46 .70 31 .10 23 .30 18 .70 12 .80 9 .70 194 PRACTICAL IRRIGATION. TABLE LIT. CASE A-2. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir, ft. . . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. 7.09 8.49 9.66 10.70 11 .60 13.78 15.57 Reservoir efficiency, per cent 34 .4 46.6 53.8 58.8 62.2 68.7 72.6 Well efficiency, per cent . . 50.8 60.0 65.3 69.1 71.7 76.5 79.4 Flow of well, gal. per min. . 15.6 71 .5 186 369 631 1,715 3,470 Total quantity annually use- ful for irrigation, acre-ft. . 11.8 69.0 196 412 730 2,115 4,450 Increase over what well would irrigate without reservoir, per cent 103 140 162 177 187 206 218 Total cost of water for irriga- tion with reservoir, per Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. acre-ft . . .... 12.68 7.46 5.80 4.95 4.47 3.77 3 .42 Cost of reservoir per acre-ft. of water used for irrigation 84.80 39.50 26.00 19.40 15 .70 10.70 8.30 TABLE LIII. CASE B-l. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft. . . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. 5.76 6.06 6.35 6.66 6.95 7.60 8.20 Reservoir efficiency, per cent 16.0 20.9 25.2 29.3 32.8 39.4 44.5 Well efficiency, per cent . . Flow of well, gal. per min. . 37.0 11 .4 40.7 48.1 43.9 115 47.0 217 49.6 355 54 .6 884 58.3 1,720 Total quantity annually use- ful for irrigation, acre-ft. . 6.8 31.6 81.5 164 284 780 1,613 Increase over what well would irrigate without reservoir, per cent 48 63 76 88 98 118 134 Total cost of water for irriga- tion with reservoir, per Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. acre-ft 13 .03 6 .51 4.4 3 .42 2.78 1 .96 1 .57 Cost of reservoir per acre-ft. of water used for irrigation 119.00 56.1 35.77 26.9 20.1 12.8 9.5 TABLE LIV. CASE B-2. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft. . . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. . 5.81 6.21 6.59 6.92 7.29 8.09 8.80 Reservoir efficiency, ft. . . . Well efficiency, per cent . . 16.8 37.6 23.2 42.4 29.0 46.7 32.4 49.3 36.5 52.4 43.3 57.5 48.7 61 .5 Rate of flow of well, gal. per min 11 .5 49.6 119 226 374 956 1,860 Total quantity annually use- ful for irrigation, acre-ft. . 7.0 34.0 89.7 179.7 316 885 1,845 Increase over what well would irrigate without reservoir, per cent . . ' 50 70 87 97 110 130 146 Total cost of water for irriga- tion with reservoir, per Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. acre-ft 11.14 5.61 3.79 3.09 2.39 1.68 1 .35 Cost of reservoir per acre-ft. of water used for irrigation 100.4 46.6 39.4 23.1 16.7 10.5 7.8 STORAGE OF ARTESIAN WATER. 195 TABLE LV. CASE C-l. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir, ft. . . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. . 7.41 8.73 9.83 10.7611 .62 13.46 15.15 Reservoir efficiency, per cent 37.6 48.3 54.7 59.0 |62.2 67.8 72.8 Well efficiency, per cent . . 53.2 61 .2 66.0 69.2 71.7 75.9 78.8 Flow of well, gal. per min. 15.2 73.5 189 372 633 1,670 3,620 Total quantity annually use- ful for irrigation, acre-ft. . 13.1 72.8 201.6 416 733 2,045 4,250 Increase over what well would irrigate without reservoir, per cent 112 145 164 177 187 203 217 Total cost of water for irriga- tion with reservoir, per Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. acre-ft 9.94 6.32 5.12 4.49 4.11 3.59 3.29 Cost of reservoir per acre-ft. of water used for irrigation 59.5 28.9 19.5 14.9 12.2 8.7 6.8 TABLE LVI. CASE C-2. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir, ft. . . Depth of embankment, ft. . Reservoir efficiency, per cent Well efficiency, per cent . . Flow of well, gal. per min. Total quantity annually use- ful for irrigation, acre-ft. . Increase over what well would irrigate without reservoir, per cent 400 7.84 41.5 56.1 16.3 14.7 124 800 9.55 53.2 64.8 81.5 85.4 160 1200 10.90 59.6 69.7 210 237 179 1600 12.07 63.8 72.7 423 497 191 2000 13.11 66.9 75.1 723 876 201 3000 15.33 72.1 79.0 1,928 2,452 217 4000 16.92 75.0 81.2 3,800 4,972 225 Total cost of water for irriga- tion with reservoir, per acre-ft Dolls. 8 10 Dolls. 5 40 Dolls. 4 47 Dolls. 3 98 Dolls. 3 69 Dolls. 3 27 Dolls. 3 03 Cost of reservoir per acre-ft. of water used for irrigation 43.3 21.7 14.8 11.4 9.4 6.7 5.0 TABLE LVII. CASE D-l. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft. . . Depth of embankment, ft. Reservoir efficiency, per cent Well efficiency, per cent . . Flow of well, gal. per min. Total quantity annually use- ful for irrigation, acre-ft. . Increase over what well would irrigate without reservoir, per cent 400 6.10 21.6 41.2 12.2 8.1 65 800 6.50 27.3 45.4 52.3 38.4 82 1200 6.89 32.2 49.1 126 100 96 1600 7.26 36.1 52.1 238 200 108 2000 7.60 39.4 54.5 393 346 118 3000 8.36 45.7 59.2 988 945 137 4000 9.15 50.9 63.2 1,945 1,980 152 Total cost of water for irriga- tion with reservoir, per acre-ft Dolls. 7.75 Dolls. 4.06 Dolls. 2.33 Dolls. 2 21 I) i 1 .86 Dolls. 1 38 Dolls. 1 13 Cost of reservoir per acre-ft. of water used for irrigation 67.7 31 .9 20.5 14.9 11.8 7.8 5.8 196 PRACTICAL IRRIGATION. TABLE LVIII. CASE D-2. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft. . . 400 800 1200 1600 2000 3000 4000 Depth of embankment, ft. . 6.11 6.70 7.21 7.68 8.12 9.08 9.92 Reservoir efficiency, per cent 21.7 29.8 35.6 40.1 43.8 50.5 55.1 Well efficiency, per cent . . Flow of well, gal. per min. . 41 .3 42.2 47.4 53.5 51.7 121 55.4 255 57.9 425 62.9 1,090 66.3 2,135 Total quantity annually use- ful for irrigation, acre-ft. . 8.1 40.9 101 .3 226.7 396.0 1,105 2,280 Increase over what well would irrigate without reservoir, per cent . 65 89 107 120 131 152 166 Total cost of water for irriga- tion with reservoir, per Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. Dolls. acre-ft 6.08 3.20 2 .20 1 .78 1.49 1.12 .94 Cost of reservoir per acre-ft. of water used for irrigation 51 .0 23.8 15.7 11 .1 8.7 5.7 4.3 TABLE LIX. CASE E-l. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir, ft 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent Well efficiency, per cent Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft . . 5.39 25.8 44 .4 12.8 9.2 6.06 34.0 50.5 32.5 26.4 6.72 40.5 55.4 64.0 57.1 7.21 44.5 58.4 107.5 101 .2 7.72 48.2 61.1 166.0 163.5 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per acre-ft. . . . Cost of reservoir per acre-ft. of water used for irrigation .... 77 Dolls. 12 .56 77.20 102 Dolls. 9.25 40.30 121 Dolls. 7.56 37.30 133 Dolls. 6.63 30.10 145 Dolls. 5.95 25 .10 TABLE LX. CASE E-2. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir ft ... 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency, per cent 5.76 30.6 47.9 6.55 39.0 54.2 7.25 44.8 58.7 7.91 49.4 62.1 8.50 53.0 64.7 Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft . . 13.7 10.6 35.2 30.7 69.2 65.5 117.5 117.5 182.0 190.2 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per ft Cost of reservoir per acre-ft. of water used for irrigation 92 Dolls. 10.96 65 .00 117 Dolls. 8.20 42.80 134 Dolls. 6.79 31 .90 148 Dolls. 5.98 25 .60 159 Dolls. 5.40 21.60 STORAGE OF ARTESIAN WATER. 197 TABLE LXI. CASE F-l. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent . . . 4.16 3.8 27.9 4.36 8.3 31 .2 4.56 12.3 33.5 4.74 15.6 36.7 5.06 20.9 40.7 Flow of well, gal. per min Total quantity annually useful for 9.8 4.44 23.3 11.74 44.3 24.00 71.0 42.10 109.0 71.50 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with 11 Dolls. 10.80 25 Dolls. 7.22 37 Dolls. 5.44 47 Dolls. 4.40 63 Dolls. 3.64 Cost of reservoir per acre-ft. of water used for irrigation 92.20 58.30 42.00 32.70 26.40 TABLE LXII. CASE F-2. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir ft 400 4.31 7.2 30.4 10.3 5.03 22 Dolls. 8.98 75.50 600 4.55 12.1 34.0 24.8 13.35 36 Dolls. 6.07 58.20 800 4.77 16.2 37.1 45.7 27.30 49 Dolls. 4.61 34.90 1000 5.00 20.0 40.0 74.1 47.90 60 Dolls. 3.74 27.20 1200 5.20 23.1 42.3 112.0 76.30 69 Dolls. 3.19 22 .40 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency per cent . ... Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per acre-ft Cost of reservoir per acre-ft. of water used for irrigation TABLE LXIII. CASE G-l. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir ft 400 6.27 36.2 52.2 14.0 12.56 109 Dolls. 8.65 45 .70 600 7.00 42.8 57.2 37.5 34.70 128 Dolls. 6.74 30.40 800 7.68 47.9 61 .0 73.2 72.00 143 Dolls. 5.76 23 .10 1000 8.27 51.7 63.8 123.4 126 .80 155 Dolls. 5.15 18.60 1200 8.82 54.7 66.0 190.0 201 .60 164 Dolls. 4.78 15.10 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency, per cent Flow of well, gal. per min Total quantity annually useful for irrigation acre-ft Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with Cost of reservoir per acre-ft. of water used for irrigation 198 PRACTICAL IRRIGATION. TABLE LXIV. CASE G-2. COST PER ACRE-FOOT OF WELL OUTPUT $2. Diameter of reservoir ft 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency, per cent . . 6.96 42.5 57.0 7.89 49.4 62.0 8.70 54.1 65.5 9.37 57.3 68.0 10.08 60.3 70.3 Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft 16.5 15.24 42.3 42.30 88.0 87.80 150.0 153.0 216.0 245.0 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per acre-ft Cost of reservoir per acre-ft. of water used for irrigation 127 Dolls. 7.67 34.50 148 Dolls. 5.71 23.20 162 Dolls. 4.97 17.80 172 Dolls. 4.52 14.50 181 Dolls. 4.20 12.40 TABLE LXV. CASE H-l. COST PER ACRE-FOOT OF WELL OUTPUT 25 CENTS. Diameter of reservoir, ft 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency, per cent 4.68 14.5 35 9 4.95 19.2 39.4 5.21 23.8 42.9 5.45 26.6 45 .5 5.67 29.5 47.1 Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft 11 .2 6.4 26.5 16.9 49.2 34.0 80.2 58 9 122.0 92.5 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per acre-ft Cost of reservoir per acre-ft. of water used for irrigation 43 Dolls. 6.48 53.1 57 Dolls. 4.40 33.60 71 Dolls. 3.39 24.40 80 Dolls. 2.78 19.00 88 Dolls. 2.39 15.60 TABLE LXVI. CASE H-2. COST PER ACRE-FOOT OF WELL OUTPUT $2. 400 600 800 1000 1200 Depth of embankment, ft Reservoir efficiency, per cent . . . Well efficiency per cent 5.09 21 .4 41 1 5.43 26.4 44 8 5.73 30.2 47 .6 6.01 33.5 50 .1 6.29 36.5 52.3 Flow of well, gal. per min Total quantity annually useful for irrigation, acre-ft ... . . 12.2 8.1 29.1 21 .0 54.8 42.0 89.8 72.5 135.0 113.8 Increase over what well would irri- gate without reservoir, per cent Total cost of water for irrigation with reservoir, per acre-ft .... 64 Dolls. 3 78 79 Dolls. 3 .32 91 Dolls. 2.59 100 Dolls. 2.15 109 Dolls. 1.87 Cost of reservoir per acre-ft. of water used for irrigation 38.00 24 .30 17.80 13 .90 11.50 CHAPTER XVI. ECONOMICS USES OF RESERVOIRS AND TANKS. IN case it is desired to irrigate only during the daytime, and not at night, then provided a reservoir is constructed to hold the night supply of the pump, a far smaller pump plant may be installed to perform the same work required of a plant operated only during the daytime. The cost of a reservoir will generally be much less than the cost of doubling the size of the pump plant. The smaller plant will, in general, require more fuel for the delivery of a given quantity of water, owing to the lower effi- ciency of smaller units, and will also need more labor; but, on the other hand, the fixed expenses of the smaller plant will be much less. In case the plant is used only a comparatively short time during the year, for irrigation, usually the fixed expenses will be far in excess of the operating expenses, and it will pay to put in the smaller plant and reservoir, especially where labor is cheap. To get up steam in plants which run only in the day- time will require an amount of fuel equal to that consumed in from 1 to 2 hours' full-load run. In plants pumping from wells where a great part of the head consists of the distance the water is lowered in the well, a very large fuel saving may be made by operating a small plant a long time rather than a large plant a shorter time. Existing plants, where night irrigation is undesirable, may have their capacity greatly increased by the construction of reservoirs to hold the night supply of the pump. The cost of such reservoirs is usually only a small fraction of the cost of the pumping plants which will supply them. It is frequently desir- able not to irrigate during the heat of the day, in which event a reservoir is a most useful aid in irrigation. To illustrate some of the advantages of reservoirs in diminish- ing the cost of irrigation, some examples in practice will be given where conditions could have been improved. A steam plant, which cost $3,000, was used to pump from a well. The 199 200 PRACTICAL IRRIGATION. plant was operated 10 hours per day. The quantity of water delivered was 2,500 gal. per min. and the head 50 feet. Water stood 2 feet below the ground without flow, and the friction in the well casing and piping was practically the only source of loss of head. If 10 hours' run was sufficient for the needs of the land, then the capacity of the plant could have been reduced to 1040 gal. per min., if run for 24 hours. Under these / 1 \2 conditions the lift would be 48 X ( = 8.3 + 2 = 10.3 feet. Assuming that a reservoir is built to hold 14 hours 7 supply, say that the additional head against which it is necessary to pump is, on an average, 3.7 feet, making a total of 14 feet. Then water horsepower at present = 31.6, and the water horsepower of proposed plant = 3.67. In the first case, the cost of operation is $6. 30 per day for fuel 1 . 00 per day for labor 7.30 per day, allowing for 2 hours' fuel in getting up steam. The cost of fuel for power for the new plant would be $1.46 per day at the same efficiency, but from decreased size of plant would be, say, $3. 00 fuel 2.00 labor 5XJO Daily saving $2.30. To retain 1040 gal. per min. for 14 hours is equivalent to 608 gal. per min. for 24 hours, or to 2.7 acre-feet capacity. As the ground is suitable for reservoir construction, assume that an earth reservoir of 3 acre-feet capacity is built, costing 10 cents per cubic yard. By Fig. 36, Case 1, we can make this 5 feet deep and 208 feet diameter, at a cost of $220, or 6 feet deep and 177 feet in diameter, costing $280; and, of course, at con- siderably less first cost if we adopt the slopes of Case 2. Allowing $300 for reservoir and land, and $1000 for the pump plant, makes a saving of $1700 in the first cost, or $340 a year, figuring 20 per cent fixed expenses and $2.30 a day in operating expenses. In addition to a saving of this nature, there would be many obvious advantages from a reservoir, in the better regulation of the s- or /,'/:>/: AM 'OIRS AND TANKS. 201 quantity of water needed, and in operating the plant at its highest efficiency. The present plant can have its irrigation efficiency materially improved by the addition of a small reser- voir, and can also greatly increase its available limit of irrigation without night irrigation. It could be made to operate more cheaply by running longer hours, and not pumping against such a high head. For example, by operating at about 30 per cent less speed for 40 per cent more time, the same quantity of water could be delivered for about half the total fuel expenditure, provided the efficiency were the same. Practically, the efficiency would diminish, owing to the engine and boiler being operated below capacity, but still considerable fuel saving could be expected over the present method of operation. If it were desired to have the present plant irrigate twice the area of land without night irrigation, what would it cost to construct a reservoir, and what dimensions should it be given? Let cost = 10 cents per cubic yard. To store 2500 gal. per min. for 12 hours, requires 5.5 acre-feet. In Case 1, a 5-acre-foot reservoir, 5 feet deep, 272 feet in diameter, would cost $290; 7 feet deep and 208 feet diameter, $440. A certain pump plant cost $1250 for the pump and power station, and $1400 for a pipe line. The capacity of the pump was 800 gal. per min., and the cost of labor 55 cents per day. The pump operated against a lift of 65 feet plus friction head, and 12 hours per day were sufficient for irrigation. What saving could have been effected if the pump discharged into a reservoir, and operated for 24 hours a day, against the same head? If a plant of half the capacity were installed to operate continuously, the first cost would be materially lessened as indicated below. The present plant operates for 45 days a year, on an average. Present cost of labor per day ....... $0.55 Present cost of fuel per day ....... 5.00 $5.55 Annual fuel expense = 45 X 5.00 . . . . $225 Annual labor expense = 45 X . 55 .... 25 Fixed expense, 20 per cent on $1250 . . . 250 Fixed expense, 12 per cent on $1400 . . . 168 Total annual expense ........ $668 202 PRACTICAL IRRIGATION. If a reservoir be installed to hold 12 hours' supply of a plant of half this capacity, it will need to hold 200 gal. per min. for a day, or 0.88 acre-feet. The soil is unsuitable for reservoir construc- tion without lining. As labor is very cheap, assume the reser- voir lined with puddle, and the cost of labor and materials is two-thirds of the cost assumed in Case 3L Then the reservoir will cost, approximately, $300. Allowing for increased fuel expense, but also for the gain from constant operation, Cost of labor per day $1.10 Cost of fuel per day 5 . 50 $6.60 Cost of power house 700 Cost of pipe line 900 Annual fuel expense 45 X 5.5 . . . . $250 Annual labor expense 45 X 1.10 . . 50 Fixed expense, 20 per cent, $700 for power plant 140 Fixed expense, 12 per cent, $900 for pipe line 72 Fixed expense, 12 per cent, $300 for reservoir 36 Total ~ $548 $668 548 Saving per year $120 APPENDIX A. TABLE LXVII. LIST OF RESERVOIR CASES AND ASSUMED DATA. Cases Quantities B. C. w. b. 9- /. w. p. s. T. la 6.00 2.00 4.00 3.00 4.00 .25 5.00 2.00 3.00 2.50 16 . . 6.0 2.0 4.0 3.0 4 .0 2.0 30.0 2.0 3.0 2.5 lc . . 8.00 4.00 10.00 5.00 4.00 .25 5.00 2.00 3 .00 2 .50 Id . . 6.00 2.00 4 .00 3.00 4.00 .25 5.00 2 .00 3 .00 2 .50 le . . 8.00 4.00 10.00 5.00 4.00 .25 5.00 2.00 3.00 2.50 2a . . 6.00 2.00 4.00 3.00 4.00 .25 5.00 1 .50 2 .00 1 .75 26 . . 6.00 2.00 4.00 3.00 4.00 2.00 30.00 1 .50 2 .00 1 .75 If . . 6.00 2.00 4.00 3 .00 4.00 .25 5.00 2.00 3.00 2.50 10 6.00 2.00 4.00 3 .00 4.00 2.00 30.00 2.00 3.00 2.50 Ih . . 8.00 4.00 10.00 5.00 4 .00 .25 5.00 2.00 3.00 2.50 It . . 6.00 2.00 4.00 3.00 4.00 2.00 30.00 2.00 3.00 2.50 3fc . . 5.00 2.00 4.00 3.00 4.00 2.00 30 .00 1 .50 1 .50 1.50 3Z . . 1.00 1.00 4.00 1 .00 0.00 30 .00 1 .50 1 .50 1.50 3w . . 2.00 2.00 4.00 2.00 0.00 30 .00 1 .50 1.50 1 .50 laa . . 6.00 2.00 4.00 3.00 4.00 .25 5.00 2.00 3.00 2.50 4a . . 6.00 2.00 * 3.00 4.00 .25 5.00 2.10 2.61 2.36 fAl . . 5.0 1 .0 4.0 3.0 3.0 2.0 15.0 2.0 3.0 2.5 A2 . . 5.00 .00 4.00 3.00 3.00 2.00 15.00 1.50 2.00 1.75 Bl . . 5.00 .00 4.00 3.00 3.00 .25 15.00 2.00 3.00 2.50 E B2 . . 5.00 .00 4.00 3.00 3.00 .25 15.00 1 .50 2.00 1.75 5 Cl . . 5.0 .0 4.0 3.0 3.0 2.0 15.0 2.0 3.0 2.5 # C2 . . 5.00 .00 4.00 3.00 3.00 2.00 15.00 1.50 2.00 1.75 Dl . . 5.00 .00 4.00 3 .00 3.00 .25 15.00 2.00 3.00 2.50 D2 . . 5.00 .00 4 .00 3 .00 3.00 .25 15.00 1.50 2.00 1.75 ~v C El . . 4.00 0.00 4 .00 2.00 3.00 2.00 15.00 2.00 3.00 2.50 |F E2 . . 4.00 0.00 4.00 2.00 3.00 2.00 15.00 1.50 2.00 1.75 c .2 Fl . . 4.00 0.00 4.00 2.00 3.00 .25 15.00 2.00 3.00 2.50 S F2 . . 4.00 0.00 4.00 2.00 3.00 .25 15.00 1 .50 2.00 1.75 Gl . . 4.00 0.00 4.00 2.00 3.00 2.00 15.00 2.00 3.00 2.50 < G2 . . 4.00 0.00 4.00 2.00 3.00 2.00 15.00 1.50 2.00 1.75 HI . . 4.00 0.00 4.00 2.00 3.00 .25 15.00 2.00 3.00 2.50 LH2 . . 4.00 0.00 4.00 2.00 3.00 .25 15.00 1 .50 2.00 1.70 *W = H + 5 -2bT= #-9.13. If H = 9.13, the bank would have no crown. This applies strictly to cases of greater values of H. 203 204 PRACTICAL IRRIGATION. TABLE LXVII Concluded. Cases Quantities c. M. n. P' 9w. t. d. i. k. lOOOa la lb Ic Id le 2a 2b I/ 10 Ih li 3k 31 3m laa 4a Al A2 Bl B2 Cl C2 Dl D2 El E2 Fl F2 Gl G2 HI H2 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 5.00 .03 .03 .03 .03 .03 .03 .03 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .25 .25 0.22 0.20 .20 0.15 .10 .10 .10 .10 .10 .10 .10 .12 .12 0.12 0.10 .10 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 1 .00 1.00 1.00 1 .00 1 .00 1.00 1 .00 1.00 1 .00 1 .00 1.00 1.00 5.0 5.0 3.0 5.0 3.0 5.0 5.0 1 1 2 2 2 2 6 '.is 0.90 18 12.00 12.00 12.00 12.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 6.00 .03 .03 .03 .03 .03 .03 .15 .10 .10 .10 .10 .10 .10 .10 .10 !io .10 .10 .10 .10 .10 .10 .10 0.18 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 .07 1.00 1 .00 1 .00 1 .00 1.00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 1 .00 3.0 5.0 3.0 3.0 3.0 3.0 3 '.6 3.0 3.0 3.0 .03 .03 .03 .03 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .10 .... .... B W b + g - k. width of crown of bank. b = clearance. g = depth of evaporation and seep- age losses during irrigation season. I = $ cost per acre-foot of water delivered to reservoir. v = $ cost of land per acre. P I -i- slope of outside bank. S = l-:- slope of inside bank. r-i(p + s). c = depth in reservoir of annual evaporation and seepage. ?7i = $ cost of riprap per sq. ft. n $ cost of embankment construc- tion per cu. yd. p = per cent annual interest, main- tenance and depreciation of reservoir, cost of puddle per sq. yd. Qw t d i = width of riprap. = annual rainfall. = per cent, interest charges. k = depth of water applied to reser- voir during irrigation season. q = constant. a = ground slope. NOTE. In cases A2, B2, E2 and F2, the width of riprap is taken as 3 (H - q) = 3 (H - 3). This applies in Case 2, when H < 12'. If H = 12 the entire bank would be riprapped. A greater value of H would mean a quantity of riprap in excess of the length of bank. APPENDIX A. 205 TABLE LXVIII. CONE RESERVOIRS. Side Slopes 1 ft. vertical to 3 ft. 1 ft. vertical to 2 ft. 1 ft. vertical to 1.5 ft. horizontal horizontal horizontal I Diam- eter Capacity for pre- ceding 1 ft. of Total capacity for cor- respond- Diam- eter Capacity for pre- ceding 1 ft. of Total capacity for cor- respond- Diam- eter Capacity for pre- ceding 1 ft. of Total capacity for cor- respond- depth ing depth depth ing depth depth ing depth Ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. 1 6 .000 .000 4 .000 .000 3 .000 .000 2 12 .002 .002 8 .001 .001 6 .000 .000 3 18 .004 .006 12 .002 .003 9 .001 .001 4 24 .008 .014 16 ..004 .007 12 .002 .003 5 30 .013 .027 20 .006 .013 15 .003 .006 6 36 .020 .047 24 .009 .022 18 .005 .011 7 42 .027 .074 28 .012 .034 21 .007 .018 8 48 .037 .111 32 .016 .050 24 .009 .027 9 54 .047 .158 36 .021 .071 27 .012 .039 10 60 .059 .217 40 .026 .097 30 .015 .054 11 66 .072 .289 44 .032 .129 33 .018 .072 12 72 .086 .375 48 .038 .167 36 .021 .093 13 78 .101 .476 52 .045 .212 39 .025 .118 14 84 .118 .594 56 .052 .264 42 .030 .148 15 90 .136 .730 60 .061 .325 45 .034 .182 16 96 .156 .886 64 .069 .394 48 .039 .221 17 102 .177 1 .063 68 .079 .473 51 .044 .265 18 108 .199 1.262 72 .088 .561 54 .050 .315 19 114 .222 1.484 76 .099 .660 57 .055 .370 20 120 .247 1.731 80 .110 .770 60 .062 .432 21 126 .272 2.003 84 .121 .891 63 .068 .500 22 132 .300 2.303 88 .133 1.024 66 .075 .575 23 138 .328 2.631 92 .146 1.170 69 .082 .657 24 144 .358 2.989 96 .159 1 .329 72 .089 .746 25 150 .389 3 .378 100 .173 1.502 75 .097 .843 26 156 .422 3.800 104 .187 1.689 78 .105 .948 27 162 .455 4.255 108 .202 1.891 81 .114 1.062 28 168 .490 4.745 112 .218 2.109 84 .122 1.184 29 174 .526 5.271 116 .234 2.343 87 .132 1.316 30 180 .564 5.835 120 .251 2.594 90 .141 1.457 31 186 .603 6.438 124 .268 2.862 93 .151 1 .608 32 192 .643 7.081 128 .286 3.148 96 .161 1.769 33 198 .685 7.766 132 .305 3.453 99 .171 1.940 34 204 .728 8.494 136 .323 3.776 102 .182 2.122 35 210 .772 9.266 140 .343 4.119 105 .193 2.315 36 216 .817 10 .083 144 .363 4.482 108 .204 2 .519 37 222 .864 10 .947 148 .384 4.866 111 .216 2.735 38 228 .912 11 .859 152 .405 5.271 114 .228 2.963 39 234 .961 12 .820 156 .427 5.698 117 .240 3.203 40 240 1.011 13.831 160 .450 6.148 120 .253 3.456 41 246 1 .064 14 .895 164 .473 6.621 123 .266 3.722 42 252 1 .116 16.011 168 .496 7.117 126 .279 4.001 206 PRACTICAL IRRIGATION. TABLE LXVIII Continued. Side Slopes 1 ft. vertical to 3 ft. 1 ft. vertical to 2 ft. 1 ft. vertical to 1.5 ft. horizontal horizontal horizontal 1 Capacity Total Capacity Total Capacity Total w Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- depth ing depth depth ing depth depth ing depth Ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. 43 258 1.170 17 .181 172 .521 7.638 129 .293 4.294 44 264 1 .226 18 .407 176 .545 8.183 132 .307 4.601 45 270 1 .283 19 .690 180 .570 8.753 135 .321 4.922 46 276 .342 21 .032 184 .597 9.350 138 .335 5.257 47 282 .400 22 .432 188 .623 9.973 141 .350 5.607 48 288 .462 23 .894 192 .650 10 .623 144 .366 5.973 49 294 .525 25 .419 196 .678 11 .301 147 .381 6.354 50 300 .590 27 .009 200 .707 12 .008 150 .397 6.751 51 306 .655 28 .664 204 .736 12 .744 153 .413 7.164 52 312 .720 30 .384 208 .764 13 .508 156 .430 7.594 53 318 .787 32 .171 212 .794 14 .302 159 .447 8.041 54 324 1.856 34 .027 216 .825 15 .127 162 .463 8.504 55 330 1.925 35 .952 220 .856 15 .983 165 .481 8.985 56 336 1.996 37 .948 224 .887 16 .870 168 .498 9.483 57 342 2.070 40 .018 228 .920 17 .790 171 .517 10 .000 58 348 2.140 42 .150 232 .952 18 .742 174 .536 10 .536 59 354 2 .220 44 .370 236 .986 19 .728 177 .555 11 .091 60 330 2.300 46 .670 240 1 .020 20 .748 180 .573 11 .664 61 366 2.380 49 .050 244 1 .054 21 .802 183 .593 12 .257 62 372 2.450 51 .500 248 1 .089 22 .891 186 .613 12 .870 63 378 2.530 54 .030 252 1.125 24 .016 189 .633 13 .503 64 384 2.610 56 .640 256 1.160 25 .176 192 .652 14 .155 65 390 2.700 59 .340 260 1.198 26 .374 195 .674 14 .829 66 396 2.780 62 .120 264 1 .234 27 .608 198 .695 15 .524 67 402 2.870 64 .990 268 1 .270 28 .878 201 .716 16 .240 68 408 2.950 67 .940 272 1 .313 30 .191 204 .738 16 .978 69 414 3.040 70 .980 276 1.351 31 .542 207 .770 17 .748 70 420 3.130 74 .110 280 1.390 32 .932 210 .783 18 .531 71 426 3.220 77 .330 284 1 .432 34 .364 213 .806 19 .337 72 432 3.310 80 .640 288 1 .473 35 .837 216 .828 20 .165 73 438 3.410 84 .050 292 1 .515 37 .352 219 .852 21 .017 74 444 3.510 87 .560 296 1 .556 38 .908 222 .877 21 .894 75 450 3.600 91 .160 300 1 .600 40 .508 225 .899 22 .793 76 456 3.700 94 .860 304 1.643 42 .151 228 .925 23 .718 77 462 3.800 98 .660 308 1.708 43 .859 231 .949 24 .667 78 468 3.900 102 .560 312 1 .735 45 .594 234 .973 25 .640 79 474 3.990 106 .550 316 1.774 47 .368 237 .998 26 .638 80 480 4.100 110 .650 320 1 .820 49 .188 240 1.024 27 .662 81 486 4.200 114 .850 324 1.867 51 .055 243 1.050 28 .712 82 492 4.310 119 .160 328 1 .912 52 .967 246 1.079 29 .791 83 498 4.410 123 .570 332 1 .960 54 .920 249 1.103 30 .894 84 504 4.520 128 .090 336 2.010 56 .930 252 1.130 32 .024 85 510 4.630 132 .720 340 2.060 58 .990 255 1 .158 33 .182 86 516 4.740 137 .460 344 2.100 61 .090 258 1 .184 34 .366 APPENDIX A. 207 TABLE LXVIII Continued. Side Slopes 1 ft. vertical to 3 ft. 1 ft. vertical to 2 ft. 1 ft. vertical to 1.5 ft. hc>ri/<>nt:il horizontal horizontal *J Capacitj Total Capacity Total Capacity Total *s H Diam- for pre- ffdiii^ capacity for cor- Diam for pre- ceding capacity for cor- Diam- for pre- ceding capacity for cor- eter 1 ft. of ivnd- eter 1ft. of respond- eter 1 ft. of respond- depth iug depth depth ing depth depth ing depth Ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. 87 522 4.850 142 .310 348 2.150 63 .240 261 1.212 35 .578 88 528 4.960 147 .270 352 2.200 65 .440 264 1.240 36 .818 89 534 5.070 152 .340 356 2.250 67.690 267 1 .269 38 .087 90 540 5.190 157 .530 360 2.310 70.000 270 1 .298 39 .385 91 546 5.300 162 .830 364 2.360 72 .360 273 1.326 40.711 92 552 5.420 168 .250 368 2.410 74 .770 276 1.355 42 .066 93 558 5.550 173 .800 372 2.470 77 .240 279 .388 43.454 94 564 5.670 179 .470 376 2.520 79 .760 282 .417 44 .871 95 570 5.780 185 .250 380 2.570 82 .330 285 .444 46 .315 96 576 5.910 191 .160 384 2.620 84 .950 288 .477 47 .792 97 582 6.020 197 .180 388 2.680 87 .630 291 .504 49 .296 98 588 6.160 203 .340 392 2.740 90.370 294 1.540 50.836 99 594 6.290 209 .630 396 2.800 93 .170 297 1.572 52 .408 100 600 6.420 216 .050 400 2.860 96 .030 300 1 .605 54 .013 101 606 6.550 222 .600 404 2.910 98 .940 303 1 .633 55 .646 102 612 6.680 229 .280 408 2.970 101 .910 306 .670 57 .316 103 618 6.810 236 .090 412 3.030 104.940 309 .701 59 .017 104 624 6.940 243 .030 416 3.080 108 .020 312 .735 60 .752 105 630 7.080 250.110 420 3.140 111 .160 315 .769 62 .521 100 636 7.220 257 .330 424 3.200 114 .360 318 .803 64 .324 107 642 7 .350 264 .680 428 3.270 117 .630 321 .838 66 .162 108 648 7.500 272 .180 432 3.330 120 .960 324 .874 68 .036 109 654 7.630 279 .810 436 3.390 124.350 327 .908 69 .944 110 660 7.780 287 .590 440 3.450 127 .800 330 1 .942 71.886 111 666 7.920 295 .510 444 3.520 131 .320 333 1 .979 73 .865 112 672 8.050 303 .560 448 3 .580 134 .900 336 2.010 75 .875 113 678 8.200 311 .760 452 3.650 138 .550 339 2.050 77 .925 114 684 8.350 320.110 456 3.710 142 .260 342 2.090 80 .015 115 690 8.500 328 .610 460 3.770 146 .030 345 2.120 82 .135 116 696 8 .650 337 .260 464 3.840 149 .870 348 2.160 84 .295 117 702 8.800 346 .060 468 3.910 153 .780 351 2.200 86 .495 118 708 8.950 355 .010 472 3.980 157 .760 354 2.240 88.735 119 714 9.120 564 .130 476 4.050 161 .810 357 2.280 91 .015 120 720 9.270 373 .400 480 4.110 165 .920 360 2.310 93 .325 121 726 9.420 382 .820 484 4.170 170 .090 363 2.350 95 .675 122 732 9.580 392 .400 488 4.250 174 .340 366 2.390 98.065 123 738 9.750 402 .150 492 4.330 178 .670 369 2.430 100 .495 124 744 9.900 412 .050 496 4.390 183.060 372 2.470 102 .965 125 750 10.050 422.100 500 4.470 187 .530 375 2.510 105 .475 126 756 10.210 432 .310 504 4.540 192.070 378 2.550 108 .025 127 762 10 .370 442 .680 508 4.610 196.680 381 2.590 110.615 128 768 10 .5.50 453 .230 512 4.680 201 .360 384 2.640 113.255 129 774 10 .710 463 .940 516 4.760 206 .120 387 2.680 115.935 130 780 10 .870 474 .810 520 4.830 210 .950 390 2.720 118.655 208 PRACTICAL IRRIGATION. TABLE XLVIII Concluded. Side Slopes 1 ft. vertical to 3 ft. 1 ft. vertical to 2 ft. 1 ft. vertical to 1.5 ft. horizontal horizontal horizontal I Capacity Total Capacity Total Capacity Total s W Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- Diam- eter for pre- ceding 1 ft. of capacity for cor- respond- depth ing depth depth ing depth depth ing depth Ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. Ft. Acre-ft. Acre-ft. 131 786 11 .030 485 .840 524 4.910 215 .860 393 2.760 121 .415 132 792 11 .200 497 .040 528 4.990 220 .850 396 2.800 124 .215 133 798 11 .380 508 .420 532 5.060 225 .910 399 2.840 127 .055 134 804 11 .540 519 .960 536 5.130 231 .040 402 2.880 129 .935 135 810 11 .720 531 .680 540 5.210 236 .250 405 2.930 132 .865 136 816 11 .900 543 .580 544 5.290 241 .540 408 2.970 135 .835 137 822 12 .070 555 .650 548 5.370 246 .910 411 3.020 138 .855 138 828 12 .250 567 .900 552 5.450 252 .360 414 3.060 141 .915 139 834 12 .430 580 .330 556 5.530 257 .890 417 3.110 145 .025 140 840 12.610 592 .940 560 5.610 263 .500 420 3.150 148 .175 141 846 12 .790 605 .730 564 5.690 269 .190 423 3.190 151 .365 142 852 12 .980 618 .710 568 5.770 274 .960 426 3.240 154 .605 143 858 13 .160 631 .870 572 5.850 280 .810 429 3.290 157 .895 144 864 13 .360 645 .230 576 5.940 286 .750 432 3.330 161 .225 145 870 13 .540 658 .770 580 6.020 292 .770 435 3.380 164 .605 146 876 13 .730 672 .500 584 6.100 298 .870 438 3.430 168 .035 147 882 13 .910 686 .410 588 6.180 305 .050 441 3.470 171 .505 148 888 14 .100 700 .510 592 6.270 311 .320 444 3.520 175 .025 149 894 14 .270 714 .790 596 6.350 317 .670 447 3.570 178 .595 150 900 14 .490 729 .280 600 6.450 324 .120 450 3.620 182 .215 151 906 14 .670 743 .950 604 6.530 330 .650 453 3.670 185 .885 152 912 14 .870 758 .820 608 6.620 337 .270 456 3.720 189 .605 153 918 15 .070 773 .890 612 6.700 343 .970 459 3.770 193 .375 154 924 15 .270 789 .160 616 6.780 350 .750 462 3.820 197 .195 155 930 15 .460 804 .620 620 6.880 357 .630 465 3.870 201 .065 156 936 15 .670 820 .2CO 624 6.970 364 .600 468 3.920 204 .985 157 942 15 .860 836 .150 628 7.050 371 .650 471 3.970 208 .955 158 948 16 .080 852 .230 632 7.150 378 .800 474 4.010 212 .965 159 954 16 .280 868 .510 636 7.240 386 .040 477 4.070 217 .035 160 960 16 .500 885 .010 640 7.330 393 .370 480 4.120 221 .155 APPENDIX A. 209 TABLE LXIX. CIRCULAR RESERVOIRS. Inside slope 1 to 3. Outside slope 1 to 2. NOTE. The capacity given allows for no clearance . CASE 1. c I * Length of side of -r M Earth in embankment equivalent capacity "i of square reservoir - g, & a If Length of side of 1 1 a as Earth in embankment 1" equivalent capacity of square reservoir ameter bas ,4 ft 0> q 1 i_ o> 1 1 s o t. crown ;. crown ;. crown meter outs 4-tt. cro\ (0 9 3 1 1 hside base ft crown. 5 5 s S IH S 3 '3 a a i i o 4 Ft. Ft. Ft. Acre-ft Gal. per min. Cu. yds. Cu. yds Cu. yds Ft. Ft. Ft. Ft. 90 2 102 .333) 75 .3 196 221 247 118 79.9 91 .9 107 .9 3 108 .531 120.0 400 442 485 128 97.9 117.9 4 114 .754 170.0 693 747 813 138 103.9 127.9 5 120 1.000 226.0 1,081 1,161 1,243 148 109.9 137.9 6 126 1 .270 287.0 1,574 1,681 1,776 158 115.9 147.9 7 132 1 .570 355.0 2,179 2,305 2,438 168 121.9 157.9 8 138 1 .901 430.0 2,912 3,060 3,211 178 127.9 167.9 100 2 112 .405 91.6 214 242 270 128 88.7 100.7 116.7 3 118 .643 145.0 437 483 529 138 106.7 126.7 4 124 .907 205.0 752 818 883 148 112.7 136.7 5 130 1.198 271 .0 1,172 1,257 1,345 158 118.7 146.7 6 136 1 .516 343.0 1,700 1,816 1,916 168 124.7 156.7 7 142 1 .864 422.0 2,347 2,481 2,614 178 130.7 166.7 8 148 2.243 508.0 3,125 3,283 3,447 188 136.7 176.7 125 2 137 .619 140.0 260 390 328 153 110.8 122.8 138.8 3 143 .972 220.0 528 583 638 163 128.8 148.8 4 149 1.356 307.0 904 984 1,058 173 134.8 158.8 5 155 1.770 401.0 1,397 1,496 1,600 183 140.8 168.8 6 161 2.221 502.0 2,014 2,148 2,364 193 146.8 178.8 7 167 2.708 613.0 2,764 2,916 3,070 203 152.8 188.8 8 173 3.230 730.0 3,662 3,843 4,030 213 158.8 198.8 150 2 162 .878 198.0 307 342 386 178 133.0 145.0 161 .0 3 168 1.367 309.0 620 683 747 188 151 .0 171 .0 4 174 1.891 428.0 1,057 1,144 1,231 198 157.0 181 .0 5 180 2.459 556 :0 1,623 1,737 1,855 208 163.0 191 .0 6 186 3.060 692.0 2,328 2,482 2,613 218 169.0 201.0 7 192 3.710 838.0 3,182 3,356 3,530 228 175.0 211 .0 8 198 4.390 993.0 4,200 4,400 4,610 238 181 .0 221 .0 175 2 187 1 .180 267.0 353 395 445 203 155.2 167.2 183.2 3 193 1.830 414.0 712 784 855 213 173.2 193.2 4 199 2.523 571 .0 1,208 1,306 1,405 223 179.2 203.2 5 205 3.260 737.0 1.848 1,977 2,110 233 185 .2 213.2 6 211 4.035 913.0 2,641 2,815 2,962 243 191 .2 223.2 7 217 4.860 1,099.0 3,700 3,795 3,990 253 197.2 233 .2 8 223 5.740 1,297.0 4,732 4,960 5,190 243 203.2 243.2 200 2 212 1.528 346.0 400 451 503 228 177.3 189.3 205.3 3 218 2.360 535.0 803 884 965 238 195.3 215.3 4 224 3.240 732.0 1,358 1,469 1,581 248 201 .3 225.3 5 230 4.170 943.0 2,074 2,216 2,364 258 207.3 235.3 6 236 5.150 1,163 .0 2,957 3,150 3,314 268 213.3 245.3 7 242 6.180 1,397.0 4,017 4,230 4,450 278 219.3 255.3 8 248 7.26 1,640 .0 5,272 5,520 5,780 288 225.3 265.3 250 2 262 2.360 534.0 493 556 620 278 221.8 233.8 249.8 3 268 3.630 820.0 987 1,084 1,184 288 239.8 259.8 4 274 4.950 1,218.0 1,660 1,794 1,930 298 245.8 269.8 5 280 6.250 1,413.0 2,527 2,696 2,873 318 ' 251 .8 279 .8 6 286 7.700 1,739 .0 3,586 3,815 4,012 328 267 .8 ' 289.8 7 292 9.280 2,098 .0 4,850 5,110 5,365 338 273 .8 1 299.8 8 298 10 .840 2,453 .0 6,340 6,640 6,940 348 279 .8 : 509.8 APPENDIX A. 211 TABLE LXIX Continued. 8 I Length of side of 1 * Earth in embankment I equivalent i-:t|..-i.-ity of square reservoir 5 1 1 ~ d If I = 1 1 | o I I I g J4 I I 2 1 1 u V e v "* OJ tJ -3 ~ ^ s 1 3 i S 41 3 5 1 1 I 5 Ft. Ft. Ft. Acre-ft. Gal. per min. Cu. yds. Cu. yds. Cu. yds Ft. Ft. Ft. Ft. 300 2 312 3.370 762.0 586 661 737 328 266.0 278 .01294 .0 3 318 5.170 1,167 .0 1,170 1,285 1,401 338 284.0301 .0 4 324 7.010 1,586.0 1,963 2,111 2,281 348 290.0314.0 5 330 8.940 2,020 .0 2,978 3,176 3,383 358 296 .0 32 1 .0 6 6 10 .940 2,476 .0 4,215 4,480 4,710 368 302 .0 334 .0 7 342 13 .000 2,941 .0 5,690 5,980 6,282 378 308.0344.0 8 348 15 .150 3,428 .0 7,420 7,750 8,110 388 314 .0 354 .0 350 2 362 4.570 1,034 .0 680 765 853 378 310.4 322 .4 338 .0 3 368 6.970 1,574.0 1,353 1,486 1,620 388 32S A 348.4 4 374 9.450 2,137 .0 2,268 2,448 2,629 398 334 .4(358 .4 5 380 12 .010 2,717 .0 3,329 3,657 3,892 418 340 .4 368.4 6 386 14 .650 3,311 .0 4,845 5,150 5,410 428 346.4 378 .4 7 392 17 .380 3,930 .0 "6,520 6,860 7,200 438 352.4 388.4 8 398 20 .200 4,563 .0 8,490 8,870 9,270 448 358.4 398.4 400 2 412 5.940 1,342.0 773 870 970 428 354.6 366.6 382.4 3 418 9.040 2,024 .0 1,538 1,687 1,837 438 372 .6 392.6 4 424 12 .230 2,766 .0 2,568 2,772 2,977 448 378 .6 402 .6 5 430 15 .510 3,507 .0 3,879 4,136 4,400 458 -5X1 6412.6 6 436 18.900 4,270 .0 5,471 5,810 6,110 468 WO .6 422 .6 7 442-22 .370 5,055 .0 7,360 7,730 8,120 478 396 .6 432 .6 8 448 2.5 .930 5,862 .0 9,560 9,990 10,440 488 102 6442.6 450 2 462 7.490 1,692.0 865 1)75 1,085 478 399.0 411 .0427.6 3 468 11.380 2,576 .0 1,720 1,888 2,057 488 117 .0437.0 4 474 15 .390 3,479 .0 2,872 3,098 3,328 498 123 .0417 .0 5 480 19 .470 4,402 .0 4,337 4,615 4,910 508 120 .0 4.57 .0 6 486 23.670 5,353 .0 6,102 6,480 6,810 518 435 .0 467 .0 7 402 28.000 6,332 .0 8,195 8,610 9,030 528 441 .0477.0 8 4<)8 32.380 7,324 .0 10,640 11,100 11,600 538 117 .0 187 .0 500 2 512 9.250 2,084 .0 960 1,079 1,201 528 443.0 1.55.0471 .0 3 518 14 .000 3,165 .0 1,904 2,088 2,273 538 161 .0481 .0 4 524 18 .900 4,267 .0 3,175 3,424 3,677 548 467 .0 491 .0 5 530 23.900 5,404 .0 4,786 5,100 5,420 558 473 .0 501 .0 6 536 29.000 6,556 .0 6.735 7,140 7,500 568 17'.) .0511.0 7 542 34.270 6,751 .0 9,030 9,490 9,950 578 485.0521 .0 8 .548 39.600 8,952 .0 11,710 12,220 12,760 588 491 .0 531 .0 550 2 562 11 .140 2,520 .0 1,050 1,184 1,318 578 487.6 1'.)'.) 6516.6 3 568 16.890 3,821 .0 2,087 2,288 2,491 588 505 .0 525 .6 4 574 22 .770 5,150 .0 3,478 3,750 4,026 598 511.6535.6 5 580 28 .780 6,508 .0 5,234 5,580 5,930 608 517 .6 545 .6 6 586 34.900 7,900 .0 7.360 7,820 8,200 618 523 6 555 .6 7 59041.100 9,300 .0 9,870 10,380 10,860 628 529 .6 565 .6 8 596 47 .500 10,728 .0 12,780 13,330 13,920 638 535 .6 575 .6 600 2 112 13 .230 2,992 .0 1,113 1,289 1,435 628 531.8 543 .8 559 .8 3 ilx_>o.040 4,534 .0 2,270 2,489 2,712 638 549 .8 569 .8 4 62427.000 6,102 .0 3,780 4,080 4,377 648 5.5.5 > :,79 .8 5 63034.100 7,700 .0 5,687 6,050 6,435 658 561 .x.589.8 6 636 41 .300 9,348 .0 7,993 8,480 8,900 668 567 .8 599 .8 7 64248.700 10,994 .0 10,697 11,240 11.7x0 678 573 .8 609 .8 8 64856.100 12,778 .0 13,850 14,4.50 15,110 6S8 579 .8 619 .8 212 PRACTICAL IRRIGATION. TABLE LXX. CIRCULAR RESERVOIRS. Inside slope 1 to 2. Outside slope 1 to NOTE. The capacity given allows for no clearance. CASE 2. . I Length of side of equiv- 2 a ; J3 Earth in embankment 'j| alent capacity of ?! S square reservoir 1 (H "S I neter top ! I 2 crown O b ii & <> 1 "S f l 1 2< s 5 E 3 3 s 5 H tH Ft. Ft. Ft. Acre-ft. Gal. per min. Cu. yd. Cu. yd. Cu. yd. Ft. Ft. Ft. Ft. 40 2 48 .070 15.8 76 89 103 62 35.5 43.5 57.5 3 52 .115 26.0 153 175 198 69 47.5 64.5 4 56 .168 37.9 263 295 328 76 51.5 71.5 5 60 .229 51 .6 410 452 496 83 55.5 78.5 6 64 .298 67.3 586 650 706 90 59.5 85.5 7 68 .376 85.0 827 897 965 97 63.5 92.5 8 72 .465 105.0 1,106 1,188 1,275 104 67.5 99.5 50 2 58 .106 23.8 91 107 123 72 44 .3 52.3 66.3 3 62 .170 38.5 182 207 234 79 56.3 73.3 4 66 .244 55.1 310 346 384 86 60.3 80.3 5 70 .327 74.0 479 526 576 93 64.3 87.3 6 74 .421 95.2 691 751 815 100 68.3 94.3 7 78 .526 119.0 951 1,029 1,107 107 72.3 101.3 8 82 .641 145.0 1,264 1,356 1,453 114 76.3 108.3 60 2 68 .148 33.4 106 124 143 82 53.2 61.2 75.2 3 72 .237 53.4 211 240 270 89 65.2 82.2 4 76 .335 75.8 356 397 440 96 69.2 89.2 5 80 .445 100.3 547 600 656 103 73.2 96.2 6 84 .566 128.0 785 853 923 110 77.2 103.2 7 88 .700 158.0 1,075 1,162 1,248 117 81.2 110.2 8 92 .846 191 .0 1,423 1,524 1,630 124 85.2 117.2 70 2 78 .198 44.7 121 141 163 92 62.1 70.1 84.1 3 82 .313 70.7 240 272 306 99 74.1 91.1 4 86 .440 99.5 .403 449 496 106 78.1 98.1 5 90 .580 131 .0 616 475 736 113 82.1 105.1 6 94 .733 163.0 879 954 1,032 120 86.1 112.1 7 98 .899 203.0 1,200 1,294 1,388 127 90.1 119.1 8 102 1.080 244.0 1,582 1,690 1,807 134 94.1 126.1 80 2 88 .255 57.5 136 159 182 102 71 .0 79.0 93.0 3 92 .400 91 .0 268 304 341 109 83.0 100.0 4 96 .560 126.0 450 500 552 116 87.0 107.0 5 100 .734 166.0 685 749 816 123 91 .0 114.0 6 104 .921 208.0 973 1,055 1,139 130 95.0 121.0 7 108 1 .124 254.0 1,325 1,427 1,527 137 99.0 128.0 8 112 1.341 313.0 1,741 8,158 1,984 144 103.0 135.0 APPENDIX .1. 213 TABLE LXX Continued. . Length of side of equiv- 3 73 Js Earth in embankment 3 a If nt capacity of a 'x C s square reservoir i 1 i 1 d d 1 a ij i 2 a i & i 2 ! 91 a 1 i JB 1 tl i 5 S I i i i 5 I a M |fi Ft. Ft. Ft. Acre-ft. Gal. per min. Cu. yd. Cu. yd. Cu. yd. Ft. Ft. Ft. Ft. 90 2 98 .319 72.0 151 176 202 112 V9.9 87.9 101.9 3 102 .500 113.0 297 336 377 119 91.9 108.9 4 106 .695 157.0 496 551 608 126 95.9 115.9 5 110 .906 204.0 752 824 896 133 99.9 122.9 6 114 1 .131 255.0 1,068 1,156 1,249 140 103.9 129.9 7 118 1.373 310.0 1,530 1,559 1,790 147 107.9 136.9 8 122 1.632 369.0 1,898 2,026 2,161 154 111.9 143.9 100 2 108 .391 88.3 166 194 222 122 88.7 96.7 110.7 3 112 .608 137.0 326 369 413 129 100.7 117.7 4 116 .843 190.0 533 602 664 136 104.7 124.7 5 120 1.094 147.0 821 898 976 143 108.7 131 .7 6 124 1 .362 308.0 1,162 1,258 1,355 150 112.7 138.7 7 128 1 .648 372.0 1,572 691 1,809 157 116.7 145.7 8 132 1 .955 441.0 2,055 2,193 2,337 164 120.7 152.7 125 2 133 .601 136.0 204 237 272 147 110.8 118.8 132.8 3 137 .930 210.0 398 449 503 154 122.8 139.8 4 141 1.278 288.0 659 730 803 161 126.8 146.8 5 145 1 .647 372.0 992 1,082 1,176 168 130.8 153.8 6 149 2.035 460.0 1,397 1,513 1,626 175 134.8 160.8 7 153 2.448 553.0 1,883 2,023 2,161 182 138.8 167.8 8 157 2.880 650.0 2,452 2,613 2,779 189 142.8 174.8 150 2 158 .855 193.0 242 281 321 172 133.0 141.0 155.0 3 162 1 .316 297.0 470 530 592 179 145.0 162.0 4 166 1 .800 412.0 776 858 943 186 149.0 169.0 5 170 2.310 522.0 1,163 1,278 1,370 193 153.0 176.0 6 174 2.845 643.0 1,634 1,766 1,897 200 157.0 183.0 7 178 3.400 769.0 2,194 2,355 2,513 207 161.0 190.0 8 182 3.990 901.0 2,848 3,032 3,223 214 165.0 197.0 175 2 183 1 .157 261.0 280 325 371 197 155.2 163.2 177.2 3 187 1.774 400.0 542 611 682 204 167.2 184.2 4 191 2.417 546.0 893 987 1,083 211 171.2 191 .2 5 195 3.090 698.0 1,334 1,453 1,576 218 175.2 198.2 6 199 3.790 856.0 1,869 2,019 2,167 225 179.2 205.2 7 203 4.510 1,019.0 2,506 2,686 2,863 232 183.2 212.2 8 207 5.270 1,190.0 3,245 3,450 3,670 239 187.2 219.2 200 2 20S 1.500 339.0 317 369 420 222 177.3 185.3 199.3 3 212 2.297 519.0 614 692 771 229 189.3 206.3 4 216 3.120 705.0 1,009 1,114 1,220 236 193.3 213.3 5 220 3.980 900.0 1,505 1,639 1,776 243 197.3 220.3 6 224 4.860 1,098.0 2,105 2,274 2,436 250 201 .3 227.3 7 228 5.800 1,306.0 2,814 3,020 3,215 257 205.3 234.3 8 232 6.750 1,523.0 3,640 3,870 4,110 264 209.3 241.3 250 2 258 2.310 521.0 393 456 519 272 221.8 229.8 243.8 3 262 3.550 802.0 758 854 950 279 233.8 250.8 4 266 4.810 1,085.0 1,241 1,371 1,500 286 237.8 257.8 5 270 6.100 1,375.0 1,847 2,011 2,176 293 241.8 264.8 6 274 7 .430 1,675.0 2,575 2,779 2,980 300 245.8 271.8 7 278 8.820 1,988.0 3,440 3,680 3,920 307 249.8 278.8 8 282 10 .220 2,305 .0 4,430 4,710 4,990 314 253.8 285.8 214 PRACTICAL IRRIGATION. TABLE LXX Concluded . V 0) d Length of side of equiv- *3 j^ Earth in embankment 1 alent capacity of .s 1 >-i S !s square reservoir I ,g "a J 1 'Z _ i $ a is h C "S a P 1 9 g 1 S 3 i o u h O (-1 4 o o e g ! g 3 ^ o ^J jj a 3 a '2 d S S 3 3 S .5 S a M M 3 Ft. Ft. Ft. Acre-ft. Gal. per min. Cu. yd. Cu. yd. Cu. yd. Ft. Ft. Ft. Ft. 300 2 308 3.330 752.0 469 544 618 322 266.0 274.0 288.0 3 312 5.060 1,142.0 903 1,016 1,129 329 278.0 295.0 4 316 6.850 1,543.0 1,474 1,627 1,780 336 282.0 302.0 5 320 8.670 1,955.0 2,190 2,383 2,576 343 286.0 309.0 6 324 10 .540 2,380 .0 3,049 3,290 3,520 350 290.0 316.0 7 328 12 .450 2,812 .0 4,060 4,350 4,620 357 294.0 323.0 8 332 14 .410 3,257 .0 5,220 5,540 5,880 364 298.0 330.0 350 2 358 4.520 1,021 .0 544 631 717 372 310.4 318.4 332.4 3 362 6.860 1,550.0 1,046 1,176 1,308 379 322 .4 339.4 4 366 9.250 2,086 .0 1.707 1,882 2,057 386 326.4 346.4 5 370 11 .700 2,641 .0 2,530 2,751 2,976 393 330.4 353.4 6 374 14.06 3,178 .0 3,520 3,790 4,060 400 334.4 360.4 7 378 16 .730 3,781 .0 4,680 5,010 5,320 407 338.4 367.4 8 382 19 .340 4,368 .0 6,020 6,390 6,770 414 342.4 374.4 400 2 408 5.890 1,330 .0 620 718 816 422 354.6 362.6 376.6 3 412 8.920 2,014 .0 1,190 1,336 1,487 429 366.6 383.6 4 416 12 .000 2,712 .0 1,940 2,140 2,338 436 370.6 390.6 5 420 15 .160 3,424 .0 2,876 3,120 3,376 443 374.6 397.6 6 424 18.37 4,150 .0 3,990 4,300 4,600 450 378.6 404.6 7 428 21 .620 4,888 .0 5,300 5,670 6,020 457 382.6 411 .6 8 432 24 .970 5,648 .0 6,810 7,220 7,650 464 386.6 418.6 450 2 458 7.430 1,678.0 696 805 915 472 399.0 407.0 421 .0 3 462 11 .230 2,537 .0 1,333 1,500 1,666 479 411.0 428.0 4 466 15 .120 3,420 .0 2,170 2,395 2,612 486 415.0 435.0 5 470 19 .080 4,310 .0 2,220 3,490 3,776 493 419.0 442.0 6 474 23 .080 5,216 .0 4,470 4,800 5,140 500 423.0 449.0 7 478 27 .200 6,148 .0 5,930 6,330 6,730 507 427.0 456.0 8 482 31 .300 7,083 .0 7,600 8,060 8,550 514 431.0 463.0 500 2 508 9170 2,067 .0 772 893 1,014 522 443.0 451.0 465.0 3 512 13 .840 3,130 .0 1,478 1,661 1,845 529 455.0 472.0 4 516 18 .600 4 203 .0 2,405 2,652 2,895 536 459.0 479.0 5 520 23 .430 5,300 .0 3,560 3,870 4,176 543 463.0 486.0 6 524 28 .360 6,408 .0 4,930 5,310 5,680 550 467.0 493.0 7 528 33 .400 7,537 .0 6,550 6,990 7,430 557 471 .0 500.0 8 532 38 .400 8,685 .0 8,390 8,900 9,430 564 475.0 507.0 550 2 558 11 .080 2,500 .0 847 981 1,113 572 487.6 495.6 509.6 3 562 16 .730 3,780 .0 1,622 1,822 2,024 579 499.6 516.6 4 566 22 .450 5,075 .0 2,637 2,908 3,174 586 503.6 523.6 5 570 28 .300 6,390 .0 3,900 4,240 4,576 593 507.6 530.6 6 574 34 .200 7,726 .0 5,400 5,820 6,230 600 511 .6 537.6 7 578 40 .200 9,084 .0 7,170 7,660 8,140 607 515.6 544.6 8 582 46 .200 10,428 .0 9,380 9,740 10,320 614 519.6 551 .6 600 2 608 13 .150 2,972 .0 923 1,067 1,212 622 531.8 539 .8 553.8 3 612 19 .850 4,493 .0 1,766 1,983 2 ; 203 629 543.8 560.8 4 616 26 .640 6,020 .0 2,871 3,160 3,450 636 547.8 567.8 5 620 33 .700 7,582 .0 4,240 4,610 4,976 643 551 .8 574.8 6 624 40 .500 9,154.0 5,880 6,330 6,770 650 555.8 581.8 7 628 47 .600 10,730 .0 7,790 8,320 8,840 657 559.8 588.8 8 632 54 .800 12,358 .0 9.980 10,570 11,200 664 563.8 595.8 APPENDIX A. 215 TABLE LXXI. RESERVOIR CAPACITY. CASE I. NOTE. The capacity given allows for no clearance. Diam- eter, Depth, Capacity, Diam- eter, Depth, Capacity, Diam- eter, Depth, Capacity, Ft. Ft. Acre-ft. Ft. Ft. Acre-ft. Ft. Ft. Acre-ft. 800 2 23.4 6 686.0 10 6,550.0 3 35.4 7 802.0 11 7,210 .0 4 47.5 8 920.0 12 7,870 .0 5 59.9 9 1,035.0 7,000 2 1,768 .0 6 72.3 10 1,153.0 3 2,660 .0 7 85.1 11 1,270.0 4 3,544 .0 8 98.0 12 1,392 .0 5 4,434 .0 9 110.9 3,000 2 325.3 6 5,315 .0 10 124.3 3 490.0 7 6,212 .0 11 137.9 4 654.0 8 7,111 .0 12 151.1 5 820.0 9 8,010 .0 1,000 2 36.5 6 985.0 10 8,910 .0 3 55.0 7 1,150.0 11 9,810 .0 4 73.9 8 1,320.0 12 10,700 .0 5 92.8 9 1,484 .0 8,000 2 2,316 .0 6 112.0 10 1,653.0 3 3,470 .0 7 131.5 11 1,820.0 4 4,623 .0 8 151.1 12 1,991 .0 5 5,792 .0 9 171.0 4,000 2 578.0 6 6,950 .0 10 191.1 3 870.0 7 8,122 .0 . 11 212.0 4 1,160.0 8 9,290.0 12 232.0 5 1,453 .0 9 10,440 .0 1,500 2 81.8 6 1,745.0 10 11,610.0 3 123.0 7 2,040 .0 11 12,820 .0 4 164.8 8 2,336 .0 12 13,970 .0 5 207 .0 9 2,628 .0 9,000 2 2,920 .0 6 249.2 10 2,926 .0 3 4,390 .0 7 292.0 11 3,222 .0 4 5,855 .0 8 335.0 12 3,520 .0 5 7,320 .0 9 378.0 5,000 2 903.0 6 8,796 .0 10 417.0 3 1,357 .0 7 10,275 .0 11 465.0 4 1,812.0 8 11,720.0 12 508.0 5 2,266.0 9 13,210 .0 2,000 2 145.0 6 2,720 .0 10 14,680 .0 3 218.3 7 3,177 .0 11 16,160.0 4 292.0 8 3,640 .0 12 17,640 .0 5 366.0 9 4,100 .0 10,000 2 3,603 .0 6 440.0 10 4,550 .0 3 5,415 .0 7 515.0 11 5,025 .0 4 7,230 .0 8 590.5 12 5,475 .0 5 9,050 .0 9 666.0 6,000 2 1,300.0 6 10,860 .0 10 742.0 3 1,951 .0 7 12,660 .0 11 820.0 4 2,607 .0 8 14,490 .0 12 896.0 5 3,260.0 9 16,290 .0 2,500 2 226.5 6 3,920 .0 10 18,120 .0 3 340.6 7 4,580 .0 11 19,960 .0 4 455 .0 8 5,230 .0 12 21,740.0 5 570.0 9 5.900.0 216 PRACTICAL IRRIGATION. TABLE LXXII. TABLE OF COEFFICIENTS TO ASSIST IN CALCULATIONS TO DETERMINE THE CUBIC YARDS OF EARTH IN RESERVOIR EMBANKMENTS WITH 4-FOOT CROWN AND OF VARIOUS DEPTHS. Cubic yards = a + bd . d = inside base diameter. Depth Case 1 a Case 1 b. Case 2 a Case 2 b Case 3 a CaseS ft Ft. 2 32 2.10 19 1.75 16 1 .57 3 81 4.02 46 3.23 39 2.97 4 166 6.52 90 5.12 75 4.66 5 296 9.60 155 7.43 127 6.70 6 483 13.30 246 10.13 200 9.09 7 728 17.50 367 13.24 295 11.82 8 1,047 22.40 518 16.80 429 14.90 9 1,450 27.80 769 20.70 570 18.35 10 1,942 33.80 1,022 25.10 752 22.10 11 2,544 40.40 1,325 29.80 972 26.25 12 3,341 47.50 1,683 35.00 1,230 30.75 13 3,963 55.30 2,095 40.50 1,529 35.60 14 5,023 63.60 2,579 46.50 1,875 40.75 15 6,113 72.50 3,127 52.90 2,270 46.30 16 2,710 52 .15 17 j 3, '21 5 58 '40 18 3 770 65 .00 19 4,385 71 ^90 20 5 070 79 .20 22 24 I 8 500 111 75 26 10^670 130 10 28 13 200 150 .00 30 16^080 171 .00 APPENDIX A. 217 TABLE LXXIII. DIMENSIONS OF CIRCULAR RESERVOIRS OF MOST ECONOMIC SECTION WITH 4-FOOT CROWN. CASE 1. Clearance = + 1Q d feet. Inside base diameter Depth of embank- ment Depth of water Capacity Volume earth n embankment Volume earth per acre-ft. Ft. Ft. Ft. Aore-ft. Cu. yd. Cu. yd. 50 1 .68 .66 .033 103 3,120 100 1 .99 .79 .149 239 1,605 200 2 .42 .97 .718 612 853 300 2 .74 1 .10 1.820 1,103 607 400 3 .02 1 .22 3.540 1,705 482 600 3.47 1 .40 9.210 3,182 345 800 3.85 1.55 18.100 5,042 279 1,000 4.19 1.69 30 .700 7,260 236 1,200 4 .49 1.81 47 .400 9,776 206 1,400 4.77 1.92 68.500 12,642 185 1,600 5.03 2.03 95.200 15,810 166 Clearance = 3 feet. 1,600 4.225 1 .225 56.8 11,650 205.0 2,000 4.225 .225 88.5 14,520 164.0 3000 4.225 .225 199.0 21,680 109.0 4,000 4.225 .225 354.0 29,800 84.3 6,000 4.225 .225 795.0 43,200 54.4 8,000 4.225 .225 1,413 .0 57,400 40.6 10,000 4.225 .225 2,206.0 71,800 32.5 218 PRACTICAL IRRIGATION. TABLE LXXIV. DIMENSIONS OF CIRCULAR RESERVOIRS OF MOST ECONOMIC SECTION WITH FOUR-FOOT CROWN. CASE 2. Clearance = .( Inside base diameter Depth of embank- ment Deptb of water Capacity Volume earth in embankment Volume earth per acre-ft. Ft. Ft. Ft. Acre-ft. Cu. yd. Cu. yd. 50 1.74 .72 .034 86.4 2,540 100 2.05 .85 .153 200.0 1,265 200 2.48 .03 .755 510.0 675 300 2.81 .17 1 .920 912.0 475 400 3.08 .28 3.730 1,394 .0 374 600 3.53 .46 9.560 2,577 .0 270 800 3.93 .63 18 .950 4,071 .0 215 1,000 4 .26 .76 32 .000 5,785 .0 181 1,200 4.57 .89 49 .300 7,784 .0 158 1,400 4.85 2 00 71 .300 10,024 .0 141 1,600 5.11 2.11 97 .900 12,494 .0 128 Clearance = 3 feet. 1,600 4.30 1 .30 60.2 9,380 155.7 2,000 4 .30 1 .30 94.0 11,690 124.4 3,000 4.30 1 .30 212.0 17,450 82.3 4,000 4 .30 1 .30 376.0 23,200 61 .7 6,000 4 .30 1 .30 845.0 34,750 41.1 8,000 4.30 1 .30 1,501 .0 46,300 30.9 10,000 4.30 1.30 2,345 .0 57,800 24.6 APPENDIX B. CIRCULAR EMBANKMENTS. VOLUME of embankment = 2 * (r + HS + ^) H (W + HS) = approximately, 2-r+HS+ w + H When P = S = T, Volume = 2-(r +HT +^\ (W+HT)H. \ ^i / Volume of water = ^ (r t 3 -r 3 ) = (approximately) TT (r+ - - ) /i O A3 \ 2 ' cu. ft. Where h = depth of water = H b. Formulae may be deduced for the economic design of large reservoirs under any predetermined conditions where the land has a given slope. In an individual case, it may be easier to use the cut-and-try method. For example, assume the reservoir diameter. Calculate the corresponding depth for the given capac- ity output, and to this add the seepage and evaporation losses during the irrigation season less the w r ater supplied to the reservoir in that period = g k, and to that add the clearance. Then the depth being determined, calculate the volume and cost of embankment, cost of lining, cost of land, and cost of riprap. Figure the annual cost and the total fixed charges, cost of lost water, and hence the storage charges on the water. Then assume nt'w diameters and repeat calculations until the minimum cost is reached. In the figures to follow, the cost of clearing and grubbing, if necessary, must be included in the cost of land, but in many places where labor is very cheap, sufficient wood may be obtained 219 220 PRACTICAL IRRIGATION. to help pay for costs of this nature. No expense is figured for removing surface soil under embankments, nor for trenching if necessary, for a puddle core. Such cost should add to the term F, to follow a quantity 2 tip Z, where Z = the additional cost of all such work per foot length of embankment. Economic Design of Large Reservoirs on Level Ground. The following figures will apply approximately to large reservoirs : * Cost of embankment = (W + TH) _ Cost of riprap = 2 xrSm(H q). TCTf^V = 43560- The cost of reservoir will be the sum of these three quantities. Annual fixed charges on reservoir (1) Annual cost of water furnished to reservoir Annual water output from reservoir in acre-feet Hence H - .+ B ...... (4) ' Total annual cost = D = Fixed charges + cost of water fur- nished to reservoir = (1) + (2). * These symbols are given on page 204. APPENDIX B. 221 Substituting the value of H found in equation (4), in the expression for D, differentiating the same with respect to r, and equating the result to zero, we derive an equation with A and r as variables, which 'gives the radius of the reservoir constructed according to the principles laid down, i.e., for a minimum annual cost for a given output capacity, A. Omitting mathematical details, the following results are obtained : A = [\/4 FI + G 2 + 4 Mr - G\ j ...... (5) D rF G IA Jr* E = -7 = r- + - - + r g +47-7 + Z = Cost per acre-foot output. A A T o / 2i A /n\ \Yhere F, G, I, and J are constants having the following values: F = ^^ (WB + B 2 T) + Smp (B - q) 2 TT t ' = .2325 B (W H- BT) pn + 6.283 mp (B - q) S: 7 = ^ - 2 pnT = 134,300,000 pnT In equation (6), the first three terms relate to fixed charges on the cost of the reservoir construction; the term containing J relates to the cost of lost water and interest on land invest- ment, and the last term, /, is the cost per acre-foot of the water supplied. Hence the cost of the reservoir construction per acre-foot output ? G I 222 PRACTICAL IRRIGATION. Then the following are values of the constants in four of the cases considered : Case la 2a lb 26. F 3218 2406 3218 2406 G 1879 1329 1879 1329 I . . 3 355 000 2 350 000 3 355 000 2 350 000 J .... 000195 000195 00145 00145 4FI+G 2 . . . . 4IJ 7,850,000 2620 4,030,000 1835 7,850,000 19 560 4,030,000 13 700 Let Then in case la R 2 A = L [V7,850,000 + 262,000 R- 1879]: 0.25. Economic Design of Large Reservoirs on Sloping Ground. Let the slope of the ground = a, Let the mean height of the embankment = H\ Then the cost of the embankment - (W + TH) 27 27 Annual fixed charges on reservoir 43560 ' Similarly the equation corresponding to (5) is iL 21 and (7) (8) r_ G 7A Kr* Jr*_ A O ^.3 *) A ct A ' ." * * * \*^/ APPENDIX B. 223 where F, G, I, J have the same values as in the previous case, and K It is to be noted that the equations found in this case apply strictly, only when the lowest depth of embankment is somewhat in excess of the clearance; also that while the surface for evapo- ration will continually diminish when the higher part of the res- ervoir starts to go dry. Still the fact that part of the water is spread out in a thin sheet and hence subject to more rapid evapo- ration will be assumed to compensate for the diminished surface. Economic Designs of Large Reservoirs on Sloping Ground, for Fixed Belt of Riprap, t Feet in Width. The equation corresponding to (7) is annual fixed charges on the reservoir Equations (8) and (9) still hold where /, J and K have the same values as above, but F = .2325 pn (WB + B 2 T) + 2tmpx, and G = 3228 (W + 2 TB) pn: I = 134,300,000 pnT: K = .349 tfnpT. Lined Reservoirs Constructed on Sloping Ground, with Fixed Width of Riprap. The effect of a lining is to increase the cost of land so much an acre, and all equations given above will still be applicable, with the exception that the term for J becomes J - ^- (ri + (B - C) I + 43560 top), where w = cost of lining per square foot. 224 PRACTICAL IRRIGATION. The arithmetical part of the calculations may be greatly simplified in the following manner. First calculate F, G, I, J, K for any given case. Then let G 2 + 4 FI a = b = 1,000,000 4/J 10,000' 4IK f 100 : G 1000 10,000,000 H 21 100 4 , Then, = V (a + bR + cR 2 - d)e. Make the following form : R a bR.. Sum Square root of Sum d Difference. A R A A^ R 3 AITEXDIX B. 225 10 d 100 fl R I A A 10 6 R 3 X 3 ' R 3 ' KR 3 x 10* ?J R 3 3 A A iL yi s = Sum. JR* X 10 4 9 R 2A A I. Sum = cost per acre-foot output H- 1-386^ # - B Efficiency = = n. L> o Cost per acre-foot capacity* = .... If lined, cost per acre-foot capacity O 4 43560 2 A 43560 wp + m + (B - C) I p It will be easier to start with r and find the corresponding value of A than to endeavor to solve equation (8) for r when A is given, though the former is a cut-and-try method. Economic Design of Large Lined Reservoirs of a Given Capacity not Riprapped, Neglecting the Value of the Water Lost by Evaporation. Here equation (8) still holds, but F = .2325 pnB (W + BT): G = 3228 pn (W + 2TB): I = 134,300,000 pnT: * Unless the bottom is lined. 226 PRACTICAL IRRIGATION. K - rF G IA Jr 2 Kr 3 and *-_ + - + _ + _ + _ + j . . . (e) If the reservoir is to be built for the cheapest cost per acre-foot for a given capacity, then F = .2325 nB (W + BT): G = 3238 n(W + 2 BT): I == 134,300,000 nT: _v + 435GQw f 6930 K = M9a 2 nT: and cost per acre-foot reservoir capacity rF G I A Jr 2 Kr 3 If in the above the actual capacity alone be considered without reference to losses of water, then in place of B use 6. If the reservoir be of small diameter these figures will not hold, but approximate results may be figured by letting r be the radius of the center of the embankment, and figuring the cost per acre-foot and acre-feet capacity. Then obtain a correc- tion factor by taking ratio of real capacity to figured capacity, as follows: (2r -W-T(H+b) ratio = I - V 2i T To obtain the true cost per acre-foot, divide the first cost per acre-foot by this ratio. To obtain true capacity, multiply first capacity by this ratio. To be accurate this correction factor should be applied to all cases of large reservoirs previously considered. The cut-and-try method will usually be simpler and more accurate than this method for any individual case. To apply MTKXDIX K. 227 this, assume various depths of water in reservoir, and from the table or curves figure various diameters. Then, allowing for clearance, figure from tables the volume and cost of embank- ment. Also calculate cost of lining. As the reservoir increases in depth, as a rule the cost of embankment will increase, and the cost of land and lining decrease. When the sum of all three costs is a minimum for a given capacity, the reservoir will be cheapest. If the lining be carried up to the top of the bank on the inside, then Cost of earthwork = -^ n (r + + HTj : Cost of land = -^ n (r + W + 2 TH?: 43,560 Cost of lining = wr. [r< + 2 H (r + v + (H - b) f T(H - 6)T Ca P acit ^ - TSjSn * \- r + T J acre - feet - Economic Design of Reservoirs on Level Ground for the Storage of Artesian Well Water. I ' = Irrigation Factor of well without reservoir. Acre-feet output of well -L) .... (10) 43,560 \1 - U Acre-feet used in Irrigation - A. (11) _ T 43,560 L 1 - U Whence, D = 2 *pr[(W + TH) ^ + Sm (H - q)] By (11). 228 PRACTICAL IRRIGATION. (Wnz z 2 Tn z , \ Hence, D = 2 npr ( + ^-^ + Sm- - qSm) *Zi i X Zi i X^ X I 2 np A ft znT W n t ^ \ _ A 2 2 nnpT "? ~27^~ x \ 27 x 27 GxpnT . J = Then equation (13) becomes Differentiate with respect to r, and equate result to zero GA IA 2 Hence, A =~[V4IF + G 2 +4/Jr-G] .... (15) Fr G 7A Jr 2 and E' = - - + + r-j + . + Z. A r 3r 3 2^1 In the above formulse 13,860 (1 - t/) x Cox's Formula. /47 2 + 57- 2\ L 1200 where H = friction head in feet, d --= diameter of pipe in inches, L = length of pipe in feet, V = velocity of water in feet per second. 1 X 1) E X . Acre feet, 11. Conversion table, 17. Acre inch, 11. Conversion table, 18. Air entrained in water, 137. Lift, 115, 116. Altitude, effect on evaporation, 33. Application, cost of water, 37, 39. Arid zone of the U. S., 1, 2. Artesian wells. Cost, 190. Definition, 86. Reservoirs for, 187 to 198, 227, 228. Flow increase by pumping, 92. Static head of, 188. Artesian well water cost, 189, 190. Automatic cutout for pump, 134, 135. Basin irrigation, 20. Bed irrigation, 20, 22. Boiler pumps, cost of, 118. Boiler setting, cost of, 118. Boilers Steam, cost of, 117. Cabbage irrigated and non-irrigated, 9. Canal, 55, 56. Canal linings, 55, 56. Canals, method of laying out, 56, 61. Canals as reservoirs, 48, 49. Velocity of water in, 56. Capacity of earth reservoirs 205 to 215. Calculation, 156 to 162, 219. Tables, 205 to 215. Centrifugal pumps, 115, 116. Capacity of, 119. Cost of, 119. Charging for irrigation, methods of, 141 to 146. Chezy Formula, 60. Cippoletti Weir, 67, 68, 69. Clearance of reservoirs, 154. Coal tar reservoir lining, 78. Concrete cores for dams, 73. Dam, 71. Lining, cost of, 78. Reinforce pipe, 60. Conduits for watrr. .55, 56, 57. Cone reservoirs capacity, 2(>r> to 208. Contour check irrigation, 21, '22. Contour ditch irrigation, 20. Core for dams, 73. Core wall-puddle, 185. Cost of irrigation, 617. Crib dams, 73. Crop formation, moisture for, 4. Crop returns and values, 37. Crops, value of, 9. Cubic feet conversion table, 18. Cubic feet per sec. per day conversion table, 19. Cultivation, deep, advantages of, 27. Effect on evaporation, 26, 30. Importance of, 5. Uselessness of Poor, 30. Culverts, 59. Current meter, 70. Dams, construction of, 70. Concrete cores for, 53. Curved, 72. Earth, 74. Failure of, 72. Kinds of, 71. Timber crib, 73. Wooden, 73. Rock fill, 73. Deep well pumps, 115. Depth of irrigation, 15, 16, 17, 35, 36, 37. Annual, 11, 12. Depth per irrigation, 12. Design of irrigation plants, 12. Pumping systems, 40. Ditches, construction of, 65. Flow in, 65, 66, 67. Diversion of water, Procedure, 42. Division box, 65. Drainage, importance of, 6. Drops, 56, 57. Droughts, effect on plants, 4. Duty of water, 11, 15, 16, 17, 34, 35, 36, 37, 39, 172. At Bakersfield, 138. Earth dams, 74. Earth embankments for carrying water, 58. Earth reservoirs, f'alrulation, 156. Capacity, 157 to 162. 229 230 INDEX. Earth tanks, construction, 74, 75. Economy in design, 153. Importance of, 153. Section of, 153. Earthwork, cost of, 76. Economy in use of water, 6. Efficiency of reservoirs, 184, 185. Embankments, reservoir, calculation, 156, 219. Construction, 74, 75, 180, 185. Curves of, 159, 160, 163. Minimum volume of, 161, 217, 218. Section of, 179, 180. Volumes of earth in, 209 to 216. Engines, gasoline, cost of, 117. Steam, cost of, 117. Steam, efficiency of, 117. Evaporation, alkali soil, 26. Annual losses, 149. Capillarity effect, 26. Color effect on, 26. Cultivation effect on, 26, 30. Deep furrows effect on, 27, 31. Definition of, 23. Efficiency, effect on, 23. Humidity, effect on, 24. Moist soils vs. water surfaces, 29. Mulches, effect on, 26, 31. Soil, 5, 30. Soil moisture, 4. Sub-irrigation, effect on, 27, 32. Temperature, effect on, 24. Transpiration, effect on, 35. Water and earth surfaces, 25. Water surfaces, altitude effect on, 33. Water surfaces, temperature, effect on, 29. Wind, effect on, 24, 29. Flooding, irrigation by, 20. Flow in ditches, 65, 66, 67. in porous media, 52, 53'. Flumes, 57, 58. Rating, 69. Velocity in, 58. Free moisture in soils, 3. Frequency of irrigation, 12, 35, 36, 37. Friction in pipe-tables, 108 to 112. Fuel consumption, pump plant, 122. Fuel, Texas, in, 123. Furrow, deep, effect on evaporation, 27, 31. Irrigation, 20, 21, 22. Gallons, conversion table, 18. Gallons per min. per day conversion table, 19. Gasoline engines, cost of, 117. Plants, fuel consumption, 122. Pump plants, cost of Texas, 121. Gate, head, 62, 63. Waste, 64. Sluice, 64. Head, Losses in piping entrance and discharge, 107, 112. Velocity, 107. Heat, methods of transference, 25. Heaters, cost of, 118. Hose irrigation, 20. Humid zone of the U. S., 1, 2. Humidity, evaporation, effect on, 24. Hydraulic ram, 115, 117. Hygroscopic, moisture in soils, 3. Inch, miners, 70. Inverted siphon, 57, 59. Irrigation, charges for, 141 to 146. Bakersfield, 128, 129. Cost of, 6, 7, 39, 151. Cost of at Bakersfield, 140. Definition, 3. Depth, 10, 11, 12, 15, 16, 17, 35, 36, 37. Desirable water for, 9. Economic limit of, 147 to 152. Excessive, 10. Expense of, 9. Irrigation factor, Artesian well, 149, 189, 190, 192. At Bakersfield, 140. Definition, 13. Effect on cost, 124. in Texas, 36. Irrigation, Frequency of, 10. Limit of in Arid America, 147. Meadow, 7. Methods, 20. Need of, 2. Plant design, 125, 126, 127. Practice, 34, 35, 36, 37, 39. Truck, 7. Value of, 2, 6, 7, 8, 38, 40, 41. Value of, comparative results, 8, 9. Value of dependent on climate, 7. Kern County Land Co., 129. Kern River Canal Co., 129. Kutter's formula, 66. Lift-pump, 105, 106. Limit of irrigation in Arid America, 147. Linings, Reservoir, 78. Loss of head in entrance and discharge pipes, 107, 112. Masonry dams, 71. Meadow irrigation, 7. Measurements of water, 67, 68, 69, 70. Miners inch, 11, 70. Minimum volumes of embankment, 161. INDEX. 231 Moist soils, evaporation from, 29. Moisture, contents of saturated air, 23. essive, 6. Free, 3. Hygroscopic, 3. To moisten soil, 5. Plant requirements, 3, 4. Sensitiveness of crop to, 7. Soil disposition, 4. Motors, poly-phase, cost of, 119. Mulches, effect on, evaporation, 26, 31. Onions, irrigated and unirrigated, 8. Open bottom wells, 79. Operation, pump plants at Bakersfield, 137. mi Pump Plants, cost of, 122. Pipe for float cut outs, 135. Friction in, tables, 108 to 112. Redwood, cost of, 59. Reinforced concrete, 60. Wooden, cost, 60. Depreciation, 60. Capacity, 60. Pit-pump at Bakersfield, 132, 133. Plants, growth of, 4. Plant growth, moisture for, 3, 4. Porous media, Flow of water in, 52, 53. Power, choice of for pumping, 113, 114. Plunger pumps, 115. for pumping, 103, 104, 105. Pulsometers, 115, 116. Pump efficiency, 103. Frames, vertical, 130. Installation at Bakersfield, 130, 131. Lift, 105, 106. Plant calculation, 125, 126, 127. Plant operation, cost of, 1-2. Pump plants, cost of in Texas, 121. Fuel consumption, 122. Operation of, at Bakersfield, 137. Reservoirs for, 199, 202. Test of, at New Orleans, 124, 125. Pump stations, cost of, 118. _-n of, 113. Performance at Bakersfu-ld, 138, 139, 140. Pump tests, 106, 107. Pump Water, cost of, 38. Pumping Water, cost analysis, 119, 120, 121. Method of charging for, 142, 143, 145. Pumping, cost of at Bakersfield, 138, 139, 140. Engines, 115. for irrigation, increase of, 113. Power for, 113, 114. Pumps, air lift, 115, 116. Boiler, cost of, 118. Centrifugal, 115, 116, 119. Pumps Continued Deep well, 115. Direct acting steam, 115. Hydraulic ram, 115, 117. Power for, 103, 104, 105. Power plunger, 115. Pulsometer, 115, 116. Pumping engines, 115. Puddle, 75. Lining, cost of, 78. Ram Hydraulic, 115, 117. Rate of flow, 11. Rating flume, 69. Reclamation service, 43. Redwood pipe, cost of, 59. Reservoir, clearance, 154. Efficiency, 184, 185. Reservoir embankments, construction, 77,180. Cost of, 76, 77, 78. Section, 179, 180. Composition of, 78. Reservoir location, value of, 45, 46. for pump plant, 199, 202. Water, cost of, 45. Reservoirs, advantages of, 150, 152. American, 181, 182. Artificial, 74. Reservoirs, artificial, advantages of, 47, 48. Artesian well, 187 to 198. Artesian well, assumed cases, 191, 192. Artesian well, design, 191 to 198. Capacity of, 205 to 208, 219. Capacity and volumes of Embank- ment, 209 to 215. Cases assumed, 155, 168, 169, 172, 173, 174, 203, 204. Correction factor for, 226. Design of, 169 to 171; 174 to IT'.i; 220 to 228. Embankment construction, 185. Embankment volumes, 216, 219. Field for, 166. Function of, 46, 47, 48. Economic use of, 199 to 202. Large; capacity of, 162. Lined, 173, 174. Minimum embankment, 217, 218. Notation, 155, 167, 203, 204. Sloping ground, 172. Reservoirs, contrasted, artificial and natural, 183, 184. Natural and artificial, 43. Natural, construction of, 70. Natural, considerations for, 44. Risk of damage to, 185. Small, advantages of, 40, 41. Rock fill dams, 73. 232 INDEX. Salts, rise of in soil, 5, 6. Sand trap, 64. Saturation, moisture of air, 23. Soil, 3. Semi-arid Zone of the U. S., 1, 2. Sluice gate, 64. Soils, deep, storage of water in, 5. Moisture disposition, 4. Saturation, 3. Void space, 3. Specific capacity of wells, 97. Spillway, 70, 71. Sprinkler irrigation, 20, 21. Steam engines, cost, 117. Efficiency, 117. Steam plants, 118. Fuel consumption, 122. Steam pumps, direct acting, 115. Steam pump plants, cost of, 121. Cost of operation, 122. Stevensons formula, 155. Storage in soils, Heavy irrigations, 13. Storage of water, cost of, 45. Stored water, method of charging for, 144, 145. Strainers for wells, 79, 80, 81. Streams, flow of as supply, 42, 43. Subirrigation, effect on evaporation, 27, 32. Surface irrigation evaporation, 32. Suppressed weirs, 67, 68, 69. Tablet irrigation, 20, 22. Tanks, earth, 74, 75, 199 to 202. Temperature air, 28. Evaporation, 24, 29. Soil, 28. Water, 28. Tests, pump, 106, 107. Timber crib dams, 73. Time element automatic cut out, 135. Transformer house, 134. Transpiration loss, light effect on, 4, 5. of crops. 35. Truck irrigation, value of, 41. Underground supply, 49, 50, 51, 129. Water flow, 51. Unsuppressed weir, 67, 68, 69. Value of crops, 37. Irrigation, 6, 7. Velocity canal, 56. Flume, 58. Head, 107. Inverted siphon, 59. Void space, soil, 3. Waste gate, 64. Wave height, 155. Water, application, cost of, 20, 37, 39. Artesian, cost of, 189, 190. Water Continued Conduction and distribution, 55. Duty of, 11, 15, 16, 17, 34, 35, 36, 37, 39, 138, 172. Economy, 6. Measurement, 67, 68, 69. Procedure before diverting, 42. Pumping cost, 38, 119, 120, 121. Rights, 3, 42. Storage in deep soils,5. Supply, flow of streams, 42, 43. Surfaces, evaporation from, 29. Well, cost of, 100, 101, Weirs at Bakersfield, 133. Cippoletti, 67, 68, 69. Suppressed, 67, 68, 69. Unsuppressed, 67, 68, 69. Well water, air entrained, 137. Cost of, 100, 101. Cost of Artesian, 189, 190. Wells, artesian, 86. Cost of in Texas, 190. Flow increase by pumping, 92. Reservoirs for, 187 to 198, 227, 228. Reservoirs with assumed cases, 191, 192. Wells at Bakersfield, 132. Boring, cost of, 99, 100, 101. Casing for, 100. Change of flow, 86, 87. Cleaning, 82. Calculation of flow, 91 to 96. Depression of water in, 85. Draft of water, 82. Elevation of water from, 82. Friction in entrance to, 80. Hydrostatic level, 85, 87, 93. Interference, mutual, 85. Kinds of, 98. Law of flow, 86, 88, 89, 90. Leakage of water in, 87. Legislation advisable, 100. Open bottom, 79. Output of, at Bakersfield, 140. Pumping from, 83. Sinking, 79, 98, 99. Specific capacity of, 97. Strainers, description, 81. Supply, storage of ground, 97. Test of flow, 88, 89, 90. ' Testing, 100. Water level fluctuation, 93, 94, 130. Water strata, 82. Wild flooding, 20. Wind, effect on evaporation, 24, 29. Wooden dams, 73. Zanjero, 142. Zones of the U. S. Arid, 1. Humid, 1. Semi Arid, 1. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. DEC 16 FEB 1 LD 21-100m-7,'33 Y.CI037I8 171