Annual Report of the Reclamation Service

the underground water conditions throughout the valley with the object of determining the areas in which underground waters are most accessible for purposes of irrigation or domestic supply. The net expenditures on this project to June 30, 1907, were $3,531.20.

PROPOSED COLORADO RIVER PROJECTS.

There are a number of possible irrigation projects along the Lower Colorado River in California and Arizona. No detailed investigation of their feasibilty has yet been made; but as the construction of such projects would necessitate that storage be provided, surveys have been made on several reservoir sites in Colorado. The fourth annual report contains a description of the work done in this connection, and also of the study of methods of conserving the water supply in the Colorado River basin. The field work was brought to a close in 1905, and no work has been done since that time, except that some borings have been made to determine the foundations at suggested dam sites. The net expenditures on this project to June 30, 1907, are $18,082.39.

CALIFORNIA-ARIZONA.

YUMA PROJECT.

GENERAL STATEMENT.

The principal data relating to the Yuma project are summarized below:

Summary of the principal data relating to the Yuma project.

Counties: Yuma County, Ariz.; Imperial County, Cal.

Latitude: 32° 30'.

Longitude: 114° 30'.

Townships: 3-13 south, ranges 21-25 west, G. & S. R. M., and townships 9-17 south, ranges 16-23 east, S. B. M.

Estimated run-off at Yuma: 11,000,000 acre-feet per annum.

Range of temperature: Maximum, 118°; minimum, 22°; mean, 73°.

Average elevation: 100 to 300 feet above sea level.

Principal products: Semitropical fruits; 7 crops alfalfa.

Nearest railroad: Southern Pacific.

Nearest station: Yuma.

Principal markets: Los Angeles and San Francisco.

Irrigable area: 100,000 acres.

Kind of headworks: Diversion dam.

Reservoir area: Settling basin 10 square miles.

Capacity of reservoir: 25,650 acre-feet.

Duty of water: 5.5 feet

Type of dam: India weir.

Height of dam: 19 feet.

Length of dam: 4,780 feet.

Length of canals: Arizona side, 16 miles; California side, 10 miles.
Length of laterals: 138 miles.

Dikes or levees on Colorado and Gila rivers: 73 miles.

Per cent public land: 27, including Indian reservation.

Character of soil: Rich alluvium.

Value of irrigated land: $50 to $150 per acre.

Date of completion: 1909, excepting Yuma Indian Reservation, which will probably be the last completed.

The construction of the Yuma project was authorized May 10, 1904. The waters of Colorado River are to be diverted about 10 miles northeast of Yuma, Ariz., into two canals, one on each side of the river. In Arizona these canals will irrigate all the bottom lands of Colorado and Gila rivers between the Laguna dam and the Mexican boundary, and in California the bottom lands of the Yuma Indian Reservation. The Laguna dam will form a basin in which the velocity of the water will be checked and the greater part of the silt allowed to settle. The water from the canals will be drawn from the surface, where it is comparatively free from silt. The dam will have a total length of 4,780 feet, a maximum width of 257 feet, and a maximum height of 19 feet.

During the year many improvements were made to facilitate the work in the field and office. Laguna dam and all construction camps,

as well as several levee stations, were equipped with telephones connecting with a central exchange at headquarters at Yuma. About 50 miles of telephone line were constructed and maintained by the service. Warehouses and freight sheds were erected, and the increased freight, moving to Laguna dam from Yuma, was carried by wagon and steamer. At the headquarters a sewerage system has been installed and other arrangements made with a view to complete sanitation.

The storeroom and commissary have been enlarged to accommodate the extra stock and equipment necessary for supplying the dam and construction camps.

The following table contains a list of contracts entered into for construction work on the Yuma project. These include all contracts for excavation and embankment; cement has in all cases been furnished by the Government.

No. of contract.

Contracts for building works on Yuma project to June 30, 1907.

Contractor.

LAGUNA DAM a AND GATES.

Work on the Laguna dam by the contractors, J. G. White & Co., of New York, was discontinued on January 24, 1907, when by mutual consent the contract was annulled and the Government assumed charge of completing the work by force account. The total amount of work performed by the contractors was 34 per cent. Of the remaining 66 per cent, the Government had completed on June 30, 1907, 28 per cent, making a total completed at that date of 52 per cent. The efficiency of the plant has been increased and the core walls carried to a point where further construction work can not be done until after the present summer overflow of the river. About 750 men have been employed on the construction work. Good stores and mess-house are managed by the Service, as well as an electric-lighting plant and water system.

The following table shows the work done on the Laguna dam to June 30, 1907:

Work done on Laguna dam, June 30, 1907.

DIKES.

A necessary feature of the Yuma project is the protection of the irrigated lands from the overflow of Colorado and Gila rivers. About 50 per cent of the entire levee work has been accomplished. During the past year the Gila Valley dikes were constructed to a point where the proposed Gila crossing was located, and protected with abattis. The Yuma Valley dike was extended during the winter, making its total length now 17 miles. On March 1 the location of the Reservation levee was approved, and all available teams were at once placed on its construction. When the floods of Colorado River stopped further work 260,000 cubic yards, or 55 per cent, of the levee had been finished. The Gila and Reservation dikes, as well as the Yuma Valley extension, were constructed by force account, and the progress made and cost reports show this to be the most satisfactory method.

IRRIGABLE LANDS.

The area comprised in the Yuma project consists mainly of rich alluvial bottom land that is exceedingly fertile. It is believed that the plant food carried by the silt in solution in the river water will perpetually fertilize the land. This region is well adapted to semitropical fruits and forage products, seven crops of alfalfa being raised in many places. The distribution of the lands under the project is shown by the following table: