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Central Valley Project
Its construction authorized by the Rivers and Harbors Act of 1937, the massive Central Valley Project (CVP) encompasses 20 reservoirs with a combined storage capacity of 11 million acre-feet, eight power plants, two pumping-generating plants and some 500 miles of major canals and aqueducts. In a normal year, the CVP delivers 7 million acre-feet of water to about 3 million acres of farmland in the Central Valley. Urban areas also get water from the CVP; the Contra Costa Canal provides water to cities in Contra Costa County while the Santa Clara Valley Water District provides CVP water to several million urban customers.
The CVP's main facilities include Shasta Dam and reservoir on the Sacramento River, Trinity Dam and Trinity Lake on the Trinity River, Folsom Dam and reservoir on the American River, New Melones Dam and reservoir on the Stanislaus River, Friant Dam and reservoir on the San Joaquin River; the Tracy Pumping Plant; Delta-Mendota Canal; and the joint-use (federal and state) San Luis Reservoir. The project is operated by the U.S. Bureau of Reclamation.
State Water Project
In 1960, California voters approved financing for construction of the initial features of the State Water Project (SWP). The project includes some 22 dams and reservoirs, a Delta pumping plant, a 444-mile-long aqueduct that carries water from the Delta through the San Joaquin Valley to southern California. The project begins at Oroville Dam on the Feather River and ends at Lake Perris near Riverside. At the Tehachapi Mountains, giant pumps lift the water from the California Aqueduct some 2,000 feet over the mountains and into southern California.
The SWP provides irrigation water to farms in the San Joaquin Valley, and is a major source of supply for cities in Los Angeles, Riverside, San Bernardino, San Diego, and other parts of southern California. In addition, the SWP serves cities in Napa and Solano counties through the North Bay Aqueduct, Santa Barbara and San Luis Obispo counties through the Coastal Aqueduct and communities in Alameda and Santa Clara counties through the South Bay Aqueduct. The project is operated by the California Department of Water Resources.
Other Major Water Systems
A number of large population centers in California have developed their own extensive water projects. The Hetch Hetchy Project transports Tuolumne River water 156 miles from the Central Sierra to San Francisco and peninsula cities.
The East Bay Municipal Utility District supplies cities on the east side of San Francisco Bay with Mokelumne River water.
Aqueducts built by the City of Los Angeles draw water from the Owens River, Mono Lake Basin and reservoirs on the east slopes of the southern Sierra. In Los Angeles, a 223-mile aqueduct completed in 1913 has served as a major water supply source, conveying water from the Owens River in the eastern Sierra. A second aqueduct, completed in 1970, added another 50 percent capacity to the water system. The two aqueducts deliver an average of 430 million gallons a day to the city.
About 30 percent of California's total annual water supply comes from groundwater in normal years, and up to 60 percent in drought years. Local communities' usage may be different; many areas rely exclusively on groundwater while others use only surface water supplies. Contrary to popular opinion, groundwater does not exist in underground lakes. Groundwater fills pores (spaces) between sand, gravel, silt and clay in water-bearing formations known as aquifers.
Local Streams and Reservoirs
Many cities rely on local water projects for all or a portion of their supplies. These projects typically were built and are operated by local public water districts, county water departments, city water departments or other special districts. Nearly 600 special purpose local agencies in California provide water to their areas through local development projects and imported supplies. A number of local agencies may also operate flood control and wastewater treatment facilities in addition to providing drinking water. Local water agencies usually are formed by a vote of the community, operate as public organizations, are governed by elected directors and fund their projects through bond issues.
In some communities, water is provided by private companies. Approximately 6 million Californians are served by these investor-owned utilities, which are regulated by the California Public Utilities Commission. The PUC monitors operations and service, sets water rates, and enforces water quality standards set by state and federal regulators.