PROPOSED LITTLE COLORADO PROJECT.

No work has been done on this project during the last fiscal year, except that necessary for measuring the flow of Little Colorado River. A summary of the total expenditures is given in the following table:

Expenditures, according to purpose and nature, on proposed Little Colorado project to June 30, 1906.

CALIFORNIA."

SACRAMENTO VALLEY INVESTIGATIONS.

Investigations in Sacramento Valley include a general study of the water supply and the location and survey of available reservoir sites.

DESCRIPTION OF SACRAMENTO VALLEY.

The

The total area of the Sacramento basin is 26,187 square miles. Sacramento Valley proper contains 4,196 square miles, or, excluding the area of surfaces of perennial streams, about 2,660,000 acres. elevation of the valley at Red Bluff is about 300 feet. From this point the fall toward the south for 60 miles averages less than 3 feet to the mile. The slope in this direction gradually decreases until it is less than 0.3 of a foot per mile near Sacramento. From the base of the foothills on the east and west, the slope is uniform toward the trough of the valley. Below the mouth of Stony Creek the Sacramento Valley is a typical flood plain, the river banks being from 5 to 20 feet higher than the trough of the valley on either side of the channel. The capacity of the Sacramento River channel below the mouth of Stony Creek to Knights Ferry is less than above Stony Creek. At some points its capacity is said to be less than one-third of that required to pass the flood reaching the valley. The basins on either side of the river are connected with it by sloughs or crevasses, and during ordinary and high stages receive water through them.

The most northerly depression on the west side of the river is the Colusa basin. It is nearly 50 miles long and from 2 to 7 miles wide, and has a storage capacity of approximately 690,000 acre-feet at ordinary stages.

The depression on the west side of the river below Colusa basin and separated from it by the Knights Ferry ridge is called the Yolo basin. It is the largest flood basin, and has a length of 40 miles and an average width of 7 miles. At times of flood it contains about 1,150,000 acrefeet of water. The waters of Cache and Puta creeks are discharged into this basin.

The depressions on the east side of the river, named from north to south, are Butte, Sutter, and American basins. During times of great flood they have a water surface of 400 square miles and hold approximately 1,900,000 acre-feet of water.

The total approximate storage capacity of all the flood basins is 3,800,000 acre-feet, not including the main Sacramento basin. This last basin has been reclaimed by levees for a number of years, though it was flooded in 1904 by a break in the levee. The flood of 1904 was unusually large, though a study of the rainfall record indicates that larger floods have occurred. Portions of the flood basins are never free from water, but a large percentage of the area is used for pastur

a Additional information relating to operations in California is given on pages 100-105 and 255-264.

age. There are localities in the Sacramento Valley where the soil is poor, but taken as a whole the soil may be said to be fertile. The portions of the delta islands and flood basins that have been reclaimed are of unsurpassed fertility. The greater part of the Sacramento Valley has been utilized since it was first settled for the production of wheat and barley. Some portions have been used for this purpose since 1850. Formerly large crops were grown. The amount produced per acre and the quality of the grain has decreased until wheat growing is no longer profitable. Rotation of crops is necessary in order to restore the productiveness of the soil in the wheat-growing districts and to make farming in this valley a certain and substantial industry. This, however, is impossible without irrigation.

WORK ACCOMPLISHED.

The surveys and investigations are not sufficiently advanced to determine definitely what percentage of the 2,660,000 acres of land in the Sacramento Valley is adapted to irrigation, but it is known that the area is large, and that it probably exceeds 2,000,000 acres.

During the years of mean rainfall, sufficient water is discharged from the drainage basin to cover the valley to a depth of about 9 feet. The greater part of this water is discharged during the winter or early spring, when it is not needed for irrigation. A study of the stream-flow data indicates the necessity of storing a portion of the winter flow. The proposed storage reservoirs will serve the double purpose of supplying water for irrigation during the irrigation season, when the natural flow of the stream is at its minimum, and decreasing the size of the distributive flood waves in winter and spring.

The following reservoir sites have been surveyed: Guenoc and Monticello, on Puta Creek; Clear Lake and Little Indian Valley, on Cache Creek; Briscoe, East Park, and Mill site, on Stony Creek; Iron Canyon, on Sacramento River; Jess Valley and West Valley, on South Fork Pit River; Warm Spring Valley and Big Valley, on Pit River; Round Valley, on Ash Creek; Big Meadows, on North Fork of Feather River; Indian Valley, on Indian Creek; Upper Mohawk, on Middle Fork of Feather River; and Grizzly Valley, on Grizzly Creek. Topographic maps of the following reservoir sites have been obtained from Mr. William Watson, C. E., and the city engineer of San Francisco: American Valley, Spanish Ranch Valley, Bucks Valley, Oregon House Valley, and Greenwood.

Summary of data concerning these reservoir sites is as follows:

Capacity of reservoirs surveyed in Sacramento basin—Continued.

• Big Valley reservoir site is below Jess Valley, West Valley, Warm Spring Valley, and Round Valley reservoir sites.

> This estimate includes discharge from Goose Lake drainage.

The Geological Survey is making a detailed topographic map of the Sacramento Valley. The mapping of the west side of the valley will be completed in 1906. This map will be used in making a study of the division of the project into units.

The investigation has reached a point where it is necessary to consider the division of the project into relatively small units, and to determine the proper sequence of their construction. This study was commenced in March, 1906, by the consideration of the Red Bluff-Orlands unit. There are 352,000 acres of valley land on the west side of the Sacramento Valley between Red Bluff and the line of the Central Irrigation Canal. This area can be irrigated by the construction of the Iron Canyon and Stony Creek reservoirs. To accomplish this it would be necessary to take out the main supply canal from the Iron Canyon reservoir at an elevation of about 330 feet. It is possible to still further divide the unit by the construction of the Stony Creek reservoirs. Between 40,000 and 50,000 acres of land in the vicinity of Orland could be irrigated from this source. The cost per acre for this small unit would be considerably more than for the larger unit.

Without any encouragement from the officers of the Reclamation Service, a water users' association has been formed at Orland and the land owners of 40,000 acres have signed agreements indicating their willingness to comply with the requirements of the reclamation act. The association in May, 1906, petitioned the Secretary of the Interior to construct an irrigation project to irrigate 40,000 to 50,000 acres of land in the vicinity of Orland. This petition was presented by a representative of the Sacramento Development Association, an organization composed of representatives from each of the counties in the Sacramento Valley and supported by the county governments. This association is endeavoring to hasten the development of the Sacramento Valley, through irrigation, immigration, and other means.

RELATION OF THE STORAGE RESERVOIRS TO FLOOD FLOW.

If storage reservoirs were constructed at sites listed in the above summary, the drainage problems of the Lower Sacramento Valley would be greatly simplified. The probable available annual flow from the watersheds tributary to the storage basins is approximately equal to the capacity of the flood basins in the Lower Sacramento Valley. The latter often increase the flood heights on the levees, and are a continued menace to reclamation works, while the storage reservoirs would greatly reduce the flood flow.

The Guenoc reservoir, if constructed, would entirely control the flow from 91 square miles in the watershed of Puta Creek. The rainfall records indicate that the precipitation in this basin is not exceeded by any similar area in California. The maximum discharge at Guenoc dam site in 1904, a year of unusually large rainfall, was 23,325 second-feet.

Monticello reservoir site is located 4 miles above the point where Puta Creek debouches upon the plain. It is believed that if the Guenoc and Monticello reservoirs were built the flood flow of Puta Creek could be so controlled that it would seldom reach dangerous proportions.

The construction of Clear Lake and Little Indian Valley reservoirs would in a measure control the flood flow of Cache Creek if the outlets were regulated with that object in view. Puta and Cache creeks discharge into Yolo basin, and their control would greatly simplify the reclamation of this basin.

The flood wave of Stony Creek could be effectually controlled by the construction of the Mill site reservoir. Ordinary reservoirs are allowed to fill with the first rains. The discharge records on Stony Creek show that the winter flow is many times more than the capacity of this reservoir. The reservoir could have been filled any year since the record began after the 1st of April; by increasing the outlet capacity and keeping the water low this reservoir could be used as a regulator of the flood flow through the rainy season until the 1st of April. The maximum flood flow of this stream exceeds 20,000 second-feet.

If Iron Canyon reservoir should be built with a large outlet capacity, ordinary flood waves could be controlled. If built for irrigation alone, it would still have the effect of retarding the passage of the flood crest on account of the large surface over which the water would be spread and stored before sufficient head was gained on the overflow weir to pass the flood flow.

The Big Valley reservoir on Pit River, if built, could store the entire winter flow from about 4,000 square miles of the watershed tributary to Sacramento River.

The area of the watershed of Feather River, above reservoir sites that have been surveyed in this basin, is 54 per cent of the total drainage area at Oroville, the point where the river leaves the foothills.

The Big Meadows, Butte Valley, Indian Valley, and Grizzly Valley reservoir sites have sufficient capacity to store in years of mean rainfall the entire discharge from 37 per cent of the Feather River watershed. This river is the largest tributary of the Sacramento, and its maximum discharge exceeds 100,000 second-feet. The mean annual rainfall in portions of its watershed exceeds 70 inches.

H. Doc. 204, 59-2-7