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through the dam the water required for the full possible power development. In the beginning, however, only such amount of power would be developed as would be needed for maneuvering the gates and for other uses in the neighborhood of the dam. Regarding extensive power development, it appears to the board that there will be such variation in the quantity of water which can be taken through the wheels, and such range in the level of the reservoir, and therefore in the head on the wheels, that the amount of power which can be counted on continuously will be very small. There will be occasions when the reservoir is empty or when though there is water in the reservoir none will be passing through the dam, as, for example, when the San Pedro is in flood. It is not, therefore, proposed to develop power for sale to consumers, as is done under the Roosevelt project. Experience after the dam is built may show, however, that this would be feasible. With nonpropelled dredges, power developed at the dam could be transmitted and used, in conjunction with a steam electric power plant built on or near the railroad, and some reduction in the cost of desilting might thus be effected. The fall in the river between the impounding dam and the diversion dam is about 700 feet, and it is likely that sites can be found in the canyon at which power dams could advantageously be built or reaches in which the regulated stream could be diverted and carried in ditches, flumes, or pipes to points where drops of sufficient height would afford cheap electric power. Such power could be sold or used in desilting. This is mentioned merely as a possibility. The board has no information on which to base anything more definite. The most promising field for the use of electric power is in pumping ground water in the irrigated area to supplement, especially in dry years, the supply of stored water. The most promising power dam site known to the board is at "Needle's Eye," a gorge about 7 miles below the San Carlos Dam site. For description and views, see Appendix B and plates 14 to 18.

LOSS BETWEEN THE IMPOUNDING AND DIVERSION DAMS AND SUPPLY CONTRIBUTED BY THE SAN PEDRO.

(Appendix J.)

134. In the present unregulated condition of the river the run-off at the Buttes exceeds by about 11 per cent the run-off at San Carlos, the increase representing the contributions of the San Pedro and smaller tributaries. It is probable that with a regulated flow from the reservoir the yearly quantity of water that could be diverted at the main heading would also exceed the quantity released from the reservoir. However, the losses from seepage and evaporation would probably be greater in the latter case than in the former, and in high floods from the San Pedro a part of the flow would pass over the diversion dam.

135. On these accounts the board makes the assumption that to furnish a yearly supply of any given quantity to the main canal will require the release of the same quantity from the reservoir. This is equivalent to assuming that the water used from the San Pedro and thus saved to the reservoir compensates for any loss to the regulated flow that occurs from evaporation and seepage between the two dams.

DIVERSION DAM.

136. At the several sites for a diversion dam ledge rock is found at one or both abutments, but investigation has shown that toward the center of the river rock is not within practicable reach. However, for the lift desired, not to exceed 10 feet, a dam of the Indian type will answer.

137. Through the courtesy of Mr. G. S. Binckley, member American Society of Civil Engineers, the board has been able to consult the design for a diversion dam for this place prepared by the late Mr. J. D. Schuyler in 1911, and a later design prepared by Messrs. Schuyler and Binckley.

138. From a consideration of these designs and the quantities of materials required for a dam following the second design, the board is able to state that the cost of the diversion dam, including head gate and silt sluice, need not exceed $150,000.

DUTY OF WATER.

139. In an arid country where land is plentiful and water scarce the quantity of water allotted to an acre of land should be made small, so as to enforce economy in its distribution and use.

140. Accordingly, under the San Carlos project, it is believed that 2 acre-feet per acre of the land would be the proper quantity to allot. While a little more than enough for one grain crop, and enough for cotton, olives, and some fruits, 2 acre-feet is less than enough for alfalfa and most fruits. It is true that in the beginning a farmer raising crops of the latter kinds would not be able to cultivate his entire acreage. An acre of land with a water right of 2 acre-feet per acre would be considered less valuable than one with a water right of more than 2 acre-feet, for the smaller the allowance of water the more thorough and laborious the methods of cultivation required. Experience shows, however, that the best crops are produced by thorough cultivation with sparing use of water, and that overirrigation results in "waterlogged" and "alkalied" lands. If the proposed allotment of water to these lands makes them less attractive to the speculator this may be regarded as an advantage.

141. There are other advantages. The benefits of the project. will be extended to a greater number of people, and the greater quantity of land with a water right of 2 acre-feet per acre will be better security to the Government for the cost of the project than would a smaller acreage with correspondingly larger water rights.

The amount of water which is required for the successful production of crops is dependent upon the climate, soil, and kind and number of crops grown. As a rule, where water is plentiful, too much is applied to the land, specially by unskilled irrigators. The most skillful irrigator obtains the best results with the smallest amount of water. Thorough cultivation rather than excessive use of water is the secret of success, and the man who attempts to save labor in cultivation by putting on additional water will usually reduce the crop production and endanger his own and possibly also his neighbor's land.

Roughly stated, the amount of water required for successful irrigation varies from 1 to 3 acre-feet per acre per annum, or an amount sufficient to cover the land from 1 to 3 feet in depth. In some sections of extreme aridity, where climatic conditions are such that crops grow during practically the entire year, this latter amount may be exceeded.

Under drought conditions, excellent crops have been raised and orchards caused to produce heavily with water carefully applied at the rate of only 1 or 1 acre-feet per acre per annum. (Principles of Irrigation Engineering, Newell and Murphy, p. 34.)

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On the projects of the United States Reclamation Service the amount of water required for a season's irrigation varies according to the best data available from 1.5 to 3.5 acre-feet per acre, the average being about 2 acre-feet per acre. (Ibid, p. 158.)

SAN CARLOS IRRIGATION PROJECT, ARIZONA.

Again, all the farmers will be interested in increasing their security against drought by supplementing the stored water with water pumped from the underground supply; in lining ditches to reduce evaporation and seepage; and finally in entering upon desilting as soon as that becomes necessary-since any diminution in the supply of 2 acre-feet would be more acutely felt than would the same percentage of reduction in the case of a greater allowance per acre.

142. It should not be overlooked, however, that in average and wet years the quantity of stored water available under the project will exceed 2 acre-feet per year, and that rainfall in the FlorenceCasa Grande district averages 10 inches annually.

AREA OF "INDIAN, PRIVATE, AND PUBLIC LANDS" TO BE TAKEN INTO PROJECT-CANAL SYSTEM.

143. Public lands.-As above stated (par. 24), there is almost no public land left within the limits of that area to which water can readily be distributed under the San Carlos project.

144. Indian lands.-It is a matter of undisputed history that from a time prior to the coming of the white man the Indians have appropriated water continuously from the Gila River for the irrigation of lands in what is now the Gila River Indian Reservation. The Little Gila, which branches from the main river near the eastern end of the reservation, is generally believed to be an ancient irrigation canal, enlarged by floods. It still serves as a main canal for lands on the south side of the river. Headgates have recently been placed at its source, and 30,000 acres of land irrigable under it are being allotted in 10-acre tracts to individual Indians. On the north side of the river 10,000 acres more are similarly being allotted under the New Santan ditch, which leaves the river about 11 miles below the head of the Little Gila. Water pumped from wells is also furnished to this land.

145. It appears above (par. 21) that the total area of the reservation is approximately 360,000 acres, of which, according to Mr. Olberg, over 100,000 acres are susceptible of irrigation. The total area cultivated by the Pimas, some at one time and some at another, is variously estimated at from 30,000 to 52,000 acres. Mr. Thackery, superintendent of the Sacaton School, states that the area under cultivation in October, 1913, was about 14,795 acres, but that, due especially to the putting in of the Little Gila headgates, preparations are being made to cultivate a larger area next year.

146. Messrs. Thackery and Olberg express the opinion that water from the San Carlos project should be furnished for 50,000 acres of land on the Indian reservation, being 10 acres per capita on the basis of a prospective population of 5,000, the population in 1912 being 3,996.

147. The board has assumed, however, that water is to be furnished to 40,000 acres of Indian lands, being 10 acres per capita on the basis of the present population; that of these 40,000 acres, 10,000 will be on the north side and 30,000 on the south side of the river; and that, as the land on the north side is already provided with pumped water, these 10,000 acres will be furnished only 1 acre-foot per acre yearly of stored water, while the 30,000 acres will be furnished 2 acre-feet.

148. Private lands.-Irrigation near Florence began about 40 years ago. In the later eighties the upper portion of the Florence Čanal was constructed, followed by an extension to Picacho Reservoir, the construction of the reservoir, and a further extension of the canal to the vicinity of Casa Grande, where a few thousand acres were irrigated. The capacity of the canal near its head was about 100 cubic feet per second, which was fairly well maintained for several years, until, through various reverses and lack of funds, it was allowed to deteriorate perhaps 80 per cent. One cause of its decline is said to have been the increase in the irrigated area near Safford, which reduced the water supply for the Florence people in the same manner as the Florence Canal had previously depleted the supply of the Pima Indians. Following the decline of the Florence Canal, several smaller ditches have been built, of perhaps 30 cubic feet per second aggregate capacity, to serve lands near the river; and lately the old Florence Canal has been somewhat improved.

149. At the present time there are two organizations or companies proposing or seeking to come into the San Carlos project, namely, the Pinal Mutual Irrigation Co., and the Casa Grande Valley Water Users' Association. The former owns or controls the old Florence Canal and the Picacho Reservoir. It also claims certain water rights and a diversion dam site; and a small amount of work has been done on its proposed new canal, which was to parallel the old Florence Canal on the upper side, presumably in preference to enlarging the latter. The territory which it proposes to irrigate is not to extend beyond the Picacho Reservoir.

150. The other organization includes much of the same lands, but covers a much larger territory, extending to and beyond Casa Grande. It, too, claims certain water rights and a diversión dam site, and it has excavated a considerable portion of the earth section of a main canal which is located a little above the canal of the Pinal Mutual.

151. The professed intention of these organizations is to build canals, and in time diversion dams, in order to get what water they can pending the execution of the San Carlos storage project. The Indians' rights to water seem not to have been provided for in these plans. In the event of the construction of the San Carlos project by the Government, each company offers to transfer to the Government at cost all its rights and property. But the original cost of the existing works is doubtless in excess of their value to the Government, for the old Florence Canal is faulty in alignment and grade, and to correct and enlarge it would cost more than to make a new canal. The canal under construction by the Casa Grande Valley Water Users' Association, though perhaps not unsatisfactory in location, is too wide to best serve the Government's purpose. It is being made 40 feet wide on the bottom, to afford capacity for carrying in times of flood an excess over the immediate needs of irrigation, to be temporarily stored in small reservoirs, which are intended to be provided. But with the impounding dam at San Carlos storing nearly all the flood water, excepting that from the San Pedro, the excess width in the canal would lose practically all its value. Besides where water is so scarce and valuable as it is in Arizona, canals should be lined to reduce the losses of water, and the lined canal permitting a greater velocity could be made much narrower. However, the narrow, lined canal could occupy one side of the 40-foot excavation, there

perhaps made a little deeper, and the remainder could be refilled to serve as a roadway, all within the present right of way.

152. The two claims to diversion dam sites amount only to applications therefor, neither of which has yet been granted by the Government. The lower site, now claimed by the Pinal Mutual, would, at this time, be chosen by the board in preference to the other, partly for the reason that its use would obviate the costly rock cut required to extend a canal to the upper site. But the relative elevations are such as to permit the use of either diversion site in connection with either canal.

153. A portion of the land in any irrigation district is pasturage, fallow lands, corrals, etc., unirrigated; this portion being estimated by some engineers at as much as 25 per cent. The board believes that in this case it would be proper to increase by 12 per cent the area to which the assumed minimum annual water supply would furnish 2 acre-feet per acre. It is explained below that, assuming the canal and main laterals to be lined, the loss of water between the diversion dam and the land, Indian and private, ought not to exceed 20 per cent. Allowing, therefore, a loss of 20 per cent between the diversion dam and the land, the assumed annual supply of 200,000 acre-feet would provide 160,000 acre-feet at the land, which at 2 acre-feet per acre would irrigate 80,000 acres. Increasing this 80,000 acres by 12 per cent, as explained above, gives a gross area of 90,000 acres. Of these 90,000 acres, 35,000 acres (the equivalent of 35,000 acres) would be Indian lands (par. 147), and 55,000 acres would constitute the private-land district. In the above, the 200,0000 acrefeet at the heading is divided between Indian and private lands in the proportion of 77,778 and 122,222 acre-feet, respectively, which is the same as that existing between the gross acreage in the two cases; or as 35/90 to 55/90. The cost of those items of the project which are common to Indian and private lands (par. 168), should be divided in this proportion (par. 169); which, being based upon relative amounts of water furnished, would be unaffected by the number of acres of land, Indian or private, to which the allotted shares of water might be at any time applied (pars. 213, 214). The irrigation of the private lands will result in a certain quantity of water becoming available either at the surface or in wells on the reservation. is impracticable to estimate the amount of this return flow, though on account of the high duty of water assumed for this project, its percentage will be less than is usually counted on. Nor can it be known in advance whether this water will be of as good quality as the water originally applied. On account of these uncertainties the board does not include any return water in the supply to be furnished by the project to the Indian lands.

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154. The question of the rights of the Indians and whites to water from the Gila is referred to elsewhere in this report.

155. Efficiency and economy require that, with soil everywhere equally adapted to irrigation, the project area should be confined, as far as is practicable, to lands near the river, not only to lessen the losses in transmission, but to make available for use again a greater amount of return water than would result from the irrigation of distant areas; as it is reasonable to suppose that the quantity recovered from near-by lands would be greater than from distant lands. 31679°-H. Doc. 791, 63-2-4

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