The State Water Project

Posted by: Aqua Blog Maven on August 19, 2008 at 4:16 pm

The California Department of Water Resources operates the State Water Project. It is the largest state-built water and power project in the United States. Beginning at Lake Davis in Northern California, spanning 600 miles south to Southern California, it includes 34 storage facilities, 20 pumping plants, four pumping-generating plants, 5 hydroelectric power plants, and about 700 miles of canals, tunnels and pipelines. The State Water Project provides drinking water for 23 million people and irrigation water for 750,000 acres of farmland.

State Water Project water was first delivered to East Bay counties in the early 1960’s. Napa and Solano counties began receiving water in 1968, but it wasn’t until 1972 that the State Water Project water arrived in Southern California. The Coastal Branch Aqueduct, supplying Santa Barbara and San Luis Obispo counties, was completed in 1997.

The Oroville Dam, located 70 miles north of Sacramento, is the tallest dam in the United States, standing 770 feet tall. The reservoir behind it is capable of storing 3.5 million acre-feet. It was completed in 1973. Besides providing water storage, the dam also provides flood control protection and recreational facilities.

Stored water is released from Lake Oroville, flows down the Feather River and enters the Sacramento River. One-third of the water released is used for irrigation between Oroville and the Delta. The North Bay Aqueduct branches off at Barker Slough and delivers water to Napa and Solano counties. The rest of the water continues moving south through the Delta towards the Harvey O. Banks Pumping Plant, where 11 pumps lift the water 244 feet up into the California Aqueduct.

South of the pumping plant, water is diverted into the South Bay Aqueduct to be transported to Alameda and Santa Clara counties in the east and south Bay Area. Water continues down the California Aqueduct, where some of it might be stored in the San Luis Reservoir, south of Los Banos. Water then continues its southward journey where about 30% will provide irrigation and drinking water to Central Valley farms and communities.

At the foot of the Tehachapi Mountains, fourteen pumps lift the water up and over the mountains, where it is split into the East and West Branch Aqueducts. The West Branch continues on to Pyramid Lake and Castaic Lake, while the East Branch Aqueduct continues south through the Antelope Valley to Silverwood Lake and Lake Perris for use in the Inland Empire.

The State Water Project takes advantage of falling water to generate hydroelectric power, which enables the project to generate about two-thirds of the power needed to run it’s facilities. Nonetheless, the State Water Project is the state’s largest electrical consumer, with about 40% of the electricity used to lift the water over the Tehachapi Mountains.

The 29 water agencies that buy SWP water have contracted for long-term deliveries of nearly 4 million acre-feet of water. About 70% of water delivered by the State Water Project is for urban use; the remaining 30% is for agricultural use. The Metropolitan Water District’s entitlement is for 2,011,500 million acre-feet, or about 47% of the total water delivered by the SWP. The Kern County Water Agency’s entitlement is for 1,153,400 million acre-feet, or about 27% of the total. The remaining 26% of the water is split between the remaining 27 water agencies.

Although contractors hold entitlements to 4.2 million acre-feet of water, rarely is the water project able to deliver that much. Contractors generally receive between 50 and 90 percent of their contracted amount. On average, the State Water Project delivers between 2.5 million & 3.5 million acre-feet of water. The lowest amount of water ever delivered was 0.55 million acre-feet during the drought of 1991.

The State Water Project was planned to be much larger, but only the first phase has been completed. It remains an open question as to whether it will ever be built out to the original specifications. Any expansion would be subject to laws and regulations not in place when the project was first designed, and any future expansion would be subject to extensive public review.

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