Environmental Consequences of Water Resource Development in California

Abstract

California has experienced one of the most extensive and intensive programs of water resource development of any geographic area of comparable size and economy in the world. This program, which has exploited virtually all of the developable surface water of the state, has been driven by a phenomenal growth in the state’s population and economy. To provide the water needed to meet population pressures, especially in the drier southern part of the state, and to supply water for irrigated agriculture in the fertile Central Valley, the state and federal governments have combined to develop one of the largest water transfer schemes in modern history. The federal Central Valley Project (CVP), initiated in the 1940s, supplies water from its Shasta-Trinity complex in water-rich Northern California to the Sacramento and San Joaquin valleys for agricultural development. The State Water Project (SWP), that went online in 1968, delivers water from Oroville Reservoir on the Feather River to agricultural users in the Tulare Valley and municipal users in the Los Angeles Basin.

This extensive development has resulted in a net average water use of about 43 x 10⁹ m³ per year, about 80 percent of which is for agriculture. Most of the state’s water resources, except for the runoff from some Northern California coastal streams, has been developed and is currently under regulation by dams and reservoirs.

Pressures which have necessitated water development have also created a related set of environmental problems. Among these are salinization of irrigated lands and surface water supplies adverse to agriculture, reduced flows and elevated water temperatures affecting the propagation and survival of salmon and other aquatic species, and water transfers in the estuarine environment that create flow and water quality conditions threatening the estuarine aquatic environment. Increased awareness of environmental cones-quences is seen as essential for effective management of limited water resources.