Water Resources of California

Abstract

In speaking of the waters of the state as a resource, we thinkof them as a tangible asset, something definite existing in the mountains that can be used for domestic and irrigation supply, manufacturing, generation of power or other useful purposes. As engineers we have been accustomed in the past to discuss the waters in our streams largely on the basis of their summer flow. Interest has centered around the amount of water that can be diverted continuously throughout the season. The huge flood volumes that fill the channels immediately following storms have not, in the past, been included as a part of our water resources. Rather, they have been regarded largely as a menace to property and an expense to put under control. The summer flow of our streams, however, is but the drain water in the wake of the season's floods, slowly working its way back to the ocean after the drenching of our mountainous areas by the winter's rains. These tardy waters have particular value in that they appear in the streams during the long dry summer season when water is most needed. Their total amount, however, is small, for three-fourths of the water flowing in California's streams, reaches the ocean within forty-five days after its precipitation upon the earth's surface. Following precipitation so closely, the bulk of the state's waters appears in the stream channels in fluctuating flows, having a striking similarity, in their varying magnitude, to the periodic occurrence of precipitation. The stage to which the development of our state has arrived now forces the inclusion of these widely fluctuating and erratic flows in a statement of our water resources. With less than four million people in the state and only one-fourth of the lands that need water under irrigation, the entire summer flow of all accessible streams has been put to use. There are no additional waters that may be brought into service except these winter flows. Therefore, unless they are