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SAN CARLOS IRRIGATION PROJECT.

DEPARTMENT OF THE INTERIOR,
UNITED STATES INDIAN SERVICE (IRRIGATION),

Los Angeles, Calif., November 1, 1915. COMMISSIONER OF INDIAN AFFAIRS,

Washington, D. C. (Through Mr. W. M. Reed, chief engineer.) SIR: The following report on the status of the available water supply, and the estimated cost of the proposed San Carlos irrigation project on the Gila River, Ariz., is respectfully submitted.

This investigation was undertaken in accordance with an authority from the Secretary of the Interior, No. 120603, dated November 8, 1913, and was continued in compliance with an item in the Indian appropriation act approved August 1, 1914, providing for investigations in connection with the San Carlos irrigation project. The initial authority provided as follows:

For all purposes necessary for proper conduct of surveys, observations, and examinations to determine the extent of water rights in and to the normal and flood flow of the Gila River, Ariz., in connection with the old Indian ditches on the Gila River reservation and others, remaining available for appropriation and use under the legal theory of prior appropriations and use and for preparation of maps, plans, drawings, specifications, and such other records as may be necessary to determine said water rights and the feasibility of any new irrigation project for Indian lands.

The item of the Indian appropriation act, above referred to, provided for an investigation recommended by the Board of Engineer officers of the United States Army. That part of the act relating to this matter reads as follows:

For investigations recommendsd by the Board of Engineer officers of the United States Army as set forth in paragraph two hundred and seventeen of their report to the Secretary of War on February fourteenth, nineteen hundred and fourteen, House Document number seven hundred and ninety-one, sixty-third Congress, second session, and report as to the supply of the legally available water, acreage available for irrigation, and titles thereto, the maximum and minimum estimated cost of the San Carlos irrigation project, including dam and necessary canals, ditches, and laterals, with recommendation and reasons therefor, and the probable cost of adjudication of water rights along the Gila River necessary thereto, and to take the steps necessary to prevent the vesting of any water rights in addition to those, if any, now existing until further action by Congress, $50,000.

In compliance with this act the investigations were continued under authority No. 80303, dated September 8, 1914, issued by the Secretary of the Interior, which provided :

For all purposes necessary for continuing the conduct of surveys, observations, examinations, and investigations to determine the extent of water

rights in and to the normal and flood flow of the Gila River, in Arizona, in connection with the old Indian ditches on the Gila River reservation, and others remaining available for appropriation and use under the legal theory of prior appropriation and use, and for the preparation of maps, drawings, specifications, and such other records as may be necessary to determine said water rights, and the feasibility of the San Carlos project.

SCOPE OF INVESTIGATION.

This investigation, as directed in the above act, was undertaken primarily for the purpose of securing data relative to the existing water rights along the Gila River to assist in the determination of the quantity of water legally available for the proposed San Carlos irrigation project. The report also includes an estimate of the maximum and minimum cost of the project, as called for in the act.

EARLIER INVESTIGATIONS,

The investigation of the water resources of the Gila watershed, with a view of increasing, through storage, the amount of water available for irrigation, was first considered by the United States in 1896, in consequence of the diminishing supply of water available to the Pima Indians on the Gila River Indian Reservation. Since that date several additional investigations have been made by the United States Geological Survey, the United States Reclamation Service, and the United States Indian Service, all under the direction of the Interior Department.

The need of an additional water supply in the vicinity of Florence and Casa Grande has been the means of interesting in the matter several irrigation companies and private persons, and as a result investigations have been conducted and reports prepared by several eminent irrigation engineers, among them Mr. J. H. Quinton and Mr. James D. Schuyler.

Finally, under section 2 of the act approved August 24, 1912, by which appropriations were made for the current and contingent expenses of the Bureau of Indian Affairs, Congress directed that a board of United States Army Engineers investigate and report on the question. The findings of this board were submitted under date of February 14, 1914, in a report entitled “Report to the Secretary of War of a board of Engineer officers, United States Army, under Indian appropriation act of August 24, 1912, on the San Carlos irrigation project, Arizona.”

The results of the investigation by the Army board are summarized in their findings and conclusions, which are contained in pages 62 to 65 of their report, and from which the following paragraphs are quoted:

PRACTICABILITY AND ADVISABILITY OF PROJECT.

202. The board finds that the San Carlos irrigation project is entirely feasible from physical considerations.

203. The advisability of the project, as before stated, will depend on its cost as compared with the benefits to result from it.

204. The cost of the project per acre will depend upon the number of acres that can be taken under the project, and tbis upon the quantity of water physically and legally available.

205. The board has pointed out that the following uncertainties exist as to the water supply legally available:

(a) It is not known whether the run-off at San Carlos as determined by the board will continue to be available or whether additional diversions above that point will be made.

(b) It is not known whether all of the water that can be taken into the main canal will be available for lands under the project or whether a part of it will have to be delivered free to lands not entered under the project.

(c) It is not known whether a part of the water that might be taken into the main canal may not have to be left in the river to satisfy rights below the reservation.

206. Until these uncertainties are cleared up, either by an adjudication or by competent legal opinion, as Congress may determine, it would be inadvisable for the United States to proceed with this project. In the following discussion, therefore, it is assumed that all of the above questions are settled in favor of the project, so that the existing run-off at San Carlos is available for use under the project.

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RECOMMENDATIONS.

217. The board recomnfends :

(a) That the San Carlos irrigation project, as described in this report, be adopted and carried out by the United States, provided it shall appear, either as the result of an adjudication or of competent legal opinion, as Congress may elect, that the legally available water supply is sufficiently close to that assumed in this report to make the cost of the project not more than $75 per acre.

(6) That suit for an adjudication of water rights along the Gila River be immediately brought in the United States district court (the United States being a party to the suit) and that every other step be taken which will hasten an early adjudication.

(c) That such executive and legal steps be taken as may be necessary to prevent the vesting of any water rights in addition to those, if any, now existing.

(d) That in case the project is not undertaken until after an adjudication, a diversion dam on the reservation (par. 171) be constructed to improve irrigation condition on the Pima Reservation.

A summary of all prior investigations of the San Carlos project has been aptly set forth on pages 11 to 23, inclusive, of the Army board's report, and it is deemed unnecessary to repeat the information here.

The report of the Army board, while it covers the practicability of the San Carlos project as a whole, confines itself more particularly to the investigations of the feasibility of the construction of the proposed San Carlos Dam and impounding reservoir. Very little or nothing can be added to the natural data assembled in connection with this feature of the investigation. It may be remarked in passing, however, that the observations made in connection with the silt determination seem capable of more than one interpretation, and it is believed that the problem of desilting a reservoir of the magnitude of that proposed at San Carlos has not received its final solution. It is admitted that no better method can be suggested at this time and therefore the figures of the United States Army board have been used in the computation of the annual maintenance costs of the project.

The duty of water assumed by the Army board in determining the amount of land which it would be possible to irrigate by means of the proposed reservoir, and on which depends the reclamation charge per acre, appears to be inadequate in the light of all data assembled in the preparation of this present report.

Neither the time nor the funds available to the board for the preparation of its report were sufficient to warrant an investigation to determine the amount of water physically and legally available.

In the preparation of the data presented herein an effort has been made to determine the amount of water physically available and. to assemble facts which will be of assistance in the determination of the amount of water legally available, and these studies, together with a new estimate of the cost of the project, from the body of the following report. For this reason it may be regarded as supplemental to the report of the United States Army Board, and no effort is made to include data published therein, references simply being made to that document.

NATURE OF PRESENT INVESTIGATION.

The work in connection with the present investigation includes the collection and study of data which may be divided into three separate headings, or subjects, namely (1) The amount of water physically available for the San Carlos project; (2) The amount of water legally available for the San Carlos project; and (3) An estimate of the cost of the San Carlos project.

The first subject, the amount of water physically available for the San Carlos project, involves a consideration of the data bearing upon the actual flow of the Gila River and its tributaries, the influence of seepage, evaporation, and return flows, and in general the hydrography, of the stream.

The second subject, the amount of water legally available, depends upon a determination of all the water rights along the stream. To obtain the requisite information respecting existing water rights, it was necessary to determine the past and present use of water along the Gila River and all of its tributaries, with the exception of the Salt River, the waters of which already have been adjudicated. This necessitated a careful survey of the land now under cultivation, as well as of that which was previously cultivated, and the collection of all data having a bearing on the past and present use of water. The data thus assembled constituted a history of irrigation along the Gila and its tributaries.

The third subject, the estimate of cost of the San Carlos project, involves the designing and estimating of cost of the storage dam and other irrigation works which make up the project, and includes the cost of maintenance, operation, and purchase of the necessary water rights.

References.—The following is a list of the more important reports which have been freely used by this service in assembling the accompanying data:

Water Supply and Irrigation Papers, United States Geological Survey :
No. 2. Irrigation near Phoenix, Ariz., by A. P. Davis.
No. 33. Storage of Water on Gila River, Ariz, by J. B. Lippincott.
No. 73. Water Storage on Salt River, Ariz., by A. P. Davis.
No. 104. The Underground Waters of Gila River Valley, by W. T. Lee.
No. 136. The Underground Waters of Salt River Valley, by W. T. Lee.
Office of Experiment Station, United States Department of Agriculture :
Bulletin No. 126. Concrete Lining as Applied to Irrigation Canals.
Bulletin No. 235. Irrigation in Arizona.

Reports of J. D. Schuyler, on San Carlos Project, 1900, and Water Supply and proposed Irrigation Works of Pinal Mutual Irrigation Co., of Florence.

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