A Newsletter about California Water, Land, and People


California's Major Water Systems

Most of the state's major coastal cities (San Diego, Los Angeles, San Francisco, and the East Bay area) all obtained water from geographically distant watersheds. Los Angeles has the most dramatically far-flung systems. The Los Angeles region imports water from Owens River and Mono Lake areas of the Sierra Nevada's eastern slope, as well as from the Colorado River (which rises in the western Rocky Mountains), and via the California State Water Project, the Feather River (which rises in the Sierra Nevada north of Lake Tahoe). The stories of how Los Angeles obtained water from the Owens River and Mono Lake are dramatic tales in themselves. Los Angeles was perceived by Owens Valley residents (and many others) as having stolen their water. Los Angeles completed this aqueduct in 1914, and added Mono Lake water to it in 1941.

Grant Lake, a Los Angeles Department
of Water and Power reservoir in the Eastern Sierra.
Photo by Samuel Huber, courtesy of
the Water Resources Center Archives,
University of California at Berkeley.

In the early 1900s, San Francisco acquired water rights to the Tuolomne River in Yosemite National Park in which it built Hetch Hetchy Reservoir from which it extended an aqueduct to supply the San Francisco Peninsula. San Francisco's plan to build O'Shaughnessy Dam in the Hetch Hetchy Valley was bitterly opposed by the famous environmentalist John Muir and the Sierra Club, since Hetch Hetchy Valley's grandeur and geologic marvels rivalled the more famous Yosemite Valley just to the south. However, Muir lost this battle, and San Francisco went on to complete the aqueduct in the early 1920s.

Oakland, Berkeley, and Richmond formed the East Bay Municipal Utilities District, and acquired water from the Mokelumne River (east of Stockton) to deliver to these and other East Bay cities, also in the 1920s.

In the Central Valley, rimmed by the Coast Range and the Sierra Nevada, every major river or creek has been dammed for supplying water to farmers or for the cities of southern California. Two vast water projects organize these diversions: the federal government's Central Valley Project (CVP), and the California State Water Project (SWP).

CVP's Delta-Mendota Canal (left),
SWP's California Aqueduct, and U.S. Interstate 5 in the San Joaquin Valley.
Photo courtesy of the California Department of Water Resources.

The CVP dams three major Central Valley rivers - the Sacramento, the San Joaquin, and the American rivers - to store water later released into aqueducts that deliver water to farmers in the San Joaquin Valley. The CVP also dams the Trinity River in northwest California's Trinity Alps and transfers Trinity water into the Sacramento River watershed for eventual export to San Joaquin Valley agriculture.

The State Water Project dams the Feather River at Oroville and delivers the water through the 444- mile-long California Aqueduct to San Joaquin Valley farmers, then over the Tehachapi Mountains south of Bakersfield to metropolitan Los Angeles. The SWP also delivers water via the North Bay Aqueduct to Napa and Solano counties; via the South Bay Aqueduct to Silicon Valley (Santa Clara County); and the Coastal Branch of the California Aqueduct to San Luis Obispo and Santa Barbara counties.

In the course of its development, San Jose exploited the groundwater naturally available under the fertile soils of the once-agricultural Santa Clara Valley. However, the spread of high technology industry (later dubbed "Silicon Valley" in the 1970s) and the sprawl of urban subdivisions contributed to heavy demands on both San Francisco's water system in the north (to the north of San Jose) and the overdrafting of the groundwater to the south in the Santa Clara Valley. Ground levels sank, damaging land and infrastructure. To deal with the problems, Valley leaders created the Santa Clara Valley Water District to coordinate and manage Silicon Valley's water supplies. Today, Santa Clara County, home to nearly 2 million people, has a system of reservoirs storing water in its Coast Range hills, and is connected to both the State Water Project and the Central Valley Project.


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