The area of the watershed tributary to the Iron Canyon, Puta Creek, Cache Creek, Stony Creek, Big Meadows, Indian Valley, Butte, and Grizzly Valley reservoir sites is 48 per cent of the valley of the Sacramento basin. The flood flow from this area would be greatly reduced by the construction of these reservoirs while there would be no interference with the complete utilization of these storage reservoirs for irrigation purposes.

From a study of the available stream-flow data it is believed that Cache Creek, Guenoc, Big Valley, Big Meadows, Butte, Grizzly, and Indian Valley reservoir sites have sufficient capacity to completely hold back the flow from 21 per cent of the watershed of the Sacramento basin during storms.

The statements given above show the intimate relation between reclamation by irrigation and reclamation from overflow. The two problems are in fact one and inseparable. It is believed that it will be difficult to reclaim the Lower Sacramento Valley except by building storage reservoirs, to be operated in connection with levees, and in such way as to offer the greatest protection to the latter. The safety of the reclaimed areas can be further insured by protecting and extending the forested area near the headwaters of the streams.

The investigations previously made on the Lower Sacramento Valley, having for their purpose the reclaiming of the flood basins, have been confined to the problems of channel enlargement and levee protection, the great object being to pass the flood flow to tide water without utilization.

EXPENDITURES.

The expenditures for this work are summarized in the following table:

Expenditures, according to purpose and nature, on proposed Sacramento Valley project to June 30, 1906.

PROPOSED OWENS VALLEY PROJECT.

No further work has been done in Owens Valley, except the continuance of the stream gauging. In the early part of the fiscal year some explorations were made to determine the depth to bed rock at various dam sites, but no detailed surveys or investigations have been made.

A summary of the total expenditures is given in the following

table:

Expenditures, according to purpose and nature, on proposed Owens Valley project to June

30, 1906.

PROPOSED SAN JOAQUIN PROJECT.

In the early part of the fiscal year the field investigations of the underground water conditions in the San Joaquin Valley were brought to a close. This work included a general examination of 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.

A summary of the expenditures is given in the following table: Expenditures, according to purpose and nature, on proposed San Joaquin project to June

30, 1906.

CALIFORNIA-ARIZONA.

YUMA PROJECT.

GENERAL STATEMENT.

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

Summary of principal data relating to Yuma project.

Counties: Yuma County, Ariz.; San Diego County, Cal.

Latitude: 32° 30'.

Longitude: 114° 30'.

Townships: 3-13 south, 9-17; ranges 21-23 west, 16-23 east.

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: 92,150 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: 731⁄2 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.

At the Yuma project (Pl. XII) the waters of Colorado River will 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 in 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 for 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.

Suitable quarters and offices for the employees of the Service and warehouses and corrals have been erected at Yuma (Pl. XIII). Preparations for the installation of an electric lighting plant have been