WATER RESOURCES OF THE SALINAS VALLEY,

CALIFORNIA.

By HOMER HAMLIN.

INTRODUCTION.

This report is based on investigations made by the United States Geological Survey, cooperating with the board of supervisors of Monterey County and the California Water and Forest Association, in Monterey County, Cal., during 1900, 1901, and 1902. The work was done under the supervision of Mr. J. B. Lippincott, resident hydrographer of the United States Geological Survey.

The report relates particularly to that portion of the Salinas Valley that lies within the boundaries of Monterey County, and describes the topography, hydrography, and economic geology of a portion of the region. It also discusses the extent of the underground water, the methods of irrigation, the irrigation systems, and the possibility of extending irrigation by the utilization of surface streams and by impounding flood waters.

The first investigation made in this region was a reconnaissance conducted under the direction of Prof. Charles D. Marx in the summer of 1900. During this reconnaissance, which was made for the purpose of locating and examining the reservoir sites in the drainage basin of Salinas River, Professor Marx's party explored the drainage basins of the Arroyo Seco, of San Antonio and Nacimiento rivers, and a portion of the drainage basin of San Lorenzo Creek. Six reservoir sites were discovered, and preliminary surveys and estimates were made to determine the capacity of each and the cost of storing water. Five of these reservoir sites are in the drainage basin of the Arroyo Seco, viz, the Pettitt, Leigh, Currier, Foster, and The Pools sites. One reservoir site, the Pinkerton, was discovered on the San Antonio, and one, the Mathews, on San Lorenzo Creek

In October, 1900, Mr. W. W. Cockins, jr., was put in charge of the study of underground waters in the vicinity of Salinas, and during the winter of 1900-1901 was also in charge of stream measurements on Salinas River and its tributaries. In December, 1900, he established

a gaging station on San Antonio Creek near Jolon, one on San Lorenzo Creek at the Hollenbeck ranch, and one on Arroyo Seco at Pettitt's ranch. A gaging station had been established on Salinas River prior to 1900.

In March, 1901, the writer was detailed to study the hydrography and geology of a portion of this region. The field work extended over a period of six months.

In the Salinas Valley, as in many parts of California, pumping water for irrigation is expensive on account of the high price of fuel. The object of the geologic investigation was to discover, if possible, cheap fuel in the form of coal or oil. A reconnaissance was made of the region and detailed examinations were made of certain localities. The result was disappointing, as no territory that will yield oil in commercial quantities was found, and the one coal field is of small extent and almost inaccessible.

In presenting the report on the economic geology of the region the writer wishes to disclaim any idea of its being more than a preliminary description of the conditions observed during the reconnaissance. At no place were the investigations exhaustive, and facts relating to the oil-producing rocks, coal beds, and water supply only were noted. Much yet remains to be done in the study of the general geology of the region and the correlation of the various formations with equivalent strata in other regions.

In October, 1901, Mr. H. E. Green was detailed to make topographic surveys of the Mathews reservoir and dam site. He also designed the dam and made estimates of the cost of construction and of the capacity of the reservoir. In August and September, 1902, the writer made a topographic survey of the Currier and Foster reservoir and dam sites, and later designed the dams and made estimates of the cost of construction and of the capacity of the reservoirs.

General acknowledgment is due a large number of persons who have rendered assistance. Thanks are particularly due Dr. William H. Dall for the identification of fossils; to the United States Department of Agriculture for well records and maps of a portion of the Salinas Valley; to the Spreckels Sugar Company for statistics on irrigation; to Mr. Lou G. Hare, county surveyor, for use of county maps, and to Messrs. T. T. Tidball, J. W. Leigh, A. J. Meyers, A. Hubbard, J. M. Krenkel, C. H. Royse, and Mrs. M. Griffin, who have furnished rainfall records.

GEOGRAPHY.

The total area of the Salinas Valley is 4,780 square miles. Its length is 150 miles and its maximum width about 45 miles. (See Pl. I.) It extends from the high mountain region in southeastern San Luis Obispo County to the Bay of Monterey, 80 miles south of San Francisco. The Salinas Valley, in common with the other Coast Range