State Water Project

The Sacramento River is the principal river of Northern California in the United States, and is the largest river in California. Rising in the Klamath Mountains, the river flows south for 400 miles before reaching the Sacramento–San Joaquin River Delta and San Francisco Bay. The river drains about 26,500 square miles in 19 California counties, mostly within the fertile agricultural region bounded by the Coast Ranges and Sierra Nevada known as the Sacramento Valley, but also extending as far as the volcanic plateaus of Northeastern California.

Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about 73 miles. Its length to its most distant headwater tributary is just over 210 miles. The main stem Feather River begins in Lake Oroville, where its four long tributary forks join together—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley.

The San Joaquin River is the longest river of Central California in the United States. The 366-mile (589 km) long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean. An important source of irrigation water as well as a wildlife corridor, the San Joaquin is among the most heavily dammed and diverted of California's rivers.

The Delta is formed by the Sacramento River flowing south to meet the north-flowing San Joaquin River just south of Sacramento, where the rivers mingle with smaller tributaries and tidal flows. The rivers’ combined fresh water flows roll through the Carquinez Strait, a narrow break in the Coast Range, and into San Francisco Bay’s northern arm, forming the Bay Delta. Suisun Marsh and adjoining bays are the brackish transition between fresh and salt water. But the location of that transition is not fixed.

The California State Water Project (SWP) supplies water to an almost 27 million Californians and 750,000 acres of farmland. It spans from Northern California to Southern California and includes 36 storage facilities, 21 pumping plants, five hydroelectric power plants, four pumping-generating plants, and approximately 705 miles of canals, tunnels, and pipelines.

The Banks Pumping Plant lies in the southern portion of the Sacramento-San Joaquin Delta, almost 20 miles southwest of the city of Stockton. Marking the beginning of the California Aqueduct, the plant provides the initial lift of water 244 feet into the canal. During its construction from 1963 to 1969, seven pumps were installed. In 1986, four more were added to divert and pump more water during the wet months to fill offstream storage reservoirs and groundwater basins south of the Delta to improve water supply reliability.

An in-land plant, Chrisman Pumping Plant is situated on the California Aqueduct, about 1.6 miles downstream from Teerink Pumping Plant. It operates in a series of sequential lifts in southern San Joaquin Valley with Buena Vista, Teerink, and Edmonston Pumping Plants to convey California Aqueduct water to and across the Tehachapi Mountains. Construction took place from 1966 to 1973.

Constructed from 1967 to 1973, Edmonston Pumping Plant provides the largest lift, nearly 2,000 vertical feet, in the SWP system. The plant’s two main discharge lines stair-step 8,400 feet up the mountain side to a 62-foot-high, 50-foot-diameter surge tank. Near the top of the lift, 140 foot diameter valves can close each discharge line in the event of a system rupture and minimize water flowing back into the plant below.

San Luis Reservoir is 12 miles west of the city of Los Banos near the historic Pacheco Pass. San Luis is part of the San Luis Joint-Use Complex that serves both the SWP and the federal Central Valley Project (CVP). The complex comprises the recreational reservoirs O'Neill Forebay, San Luis Reservoir, and Los Banos Reservoir. Completed in 1967, San Luis Reservoir is one of the nation's largest offstream reservoirs, meaning it has no watershed. Instead, San Luis stores water diverted from the Sacramento-San Joaquin Delta for later deliveries to the Silicon Valley, San Joaquin Valley, Central Coast, and Southern California. Los Banos Reservoir is located on Los Banos Creek, about 7 miles southwest of Los Banos. It provides flood protection for San Luis Canal, Delta-Mendota Canal, City of Los Banos, and other downstream developments.

The California Aqueduct is the primary method of transporting water from Northern California to Southern California. The concrete-lined canal winds its way through the Central Valley, moving water from the Clifton Court Forebay in the Sacramento-San Joaquin Delta down to Lake Perris, the SWP’s southernmost reservoir. Water travels by gravity until it is lifted by pumping plants and then continues its journey south by gravity until the next pumping plant. 

At the Tehachapi Mountains, water is lifted 1,926 feet by fourteen 80,000 horsepower pumps at Edmonston Pumping Plant. The Edmonston Pumping Plant is the highest single-lift pumping plant in the world. From the Tehachapi crossing, water flows into Antelope Valley, where the aqueduct divides into the West Branch and East Branch of the Aqueduct.

The California Aqueduct bifurcates in the East Branch (left) and West Branch (right) as it travels into the Southern California region at the border of Kern and Los Angeles Counties.

The East Branch of the SWP carries water through Antelope Valley via Pearblossom Pumping Plant and Alamo and Mojave Siphon Powerplants into Silverwood Lake in the San Bernardino Mountains. From Silverwood Lake, water enters the San Bernardino Tunnel and drops 1,406 feet into Devil Canyon Powerplant. Water then flows to Lake Perris, the SWP’s southernmost reservoir.

Extending east into Riverside County via the East Branch Extension’s Foothill Pipeline, water is pumped at Greenspot Pump Station, then into Crafton Hills Reservoir and into Crafton Hills Pump Station. From Crafton Hills Pump Station, water flows to Cherry Valley Pump Station, where water is delivered to SWP water contractors or into spreading basins for groundwater recharge.

Silverwood Lake is nestled in the San Bernardino Mountains and has a lake elevation of 3,355 feet, which is the highest of the four SWP reservoirs in Southern California. Located about 30 miles north of the city of San Bernardino on the West Fork of Mojave River, the lake and dam were constructed (1968 to 1971) to provide storage, recreation, and assure continuity of discharges through Devil Canyon Powerplant.

From the south end of the lake, water leaves via the 20,064-foot-long San Bernardino Tunnel to the penstocks of the Devil Canyon Powerplant. After power production, some of the water is taken by users directly from the afterbays. The rest enters the East Branch Extension or the Santa Ana Pipeline for delivery to the SWP’s southernmost water contractors.

Devil Canyon Powerplant, constructed between 1969 and 1974, has the highest hydraulic water pressure in the SWP system. A power recovery facility, Devil Canyon Powerplant is situated near the mouth of Devil Canyon at the southern base of the San Bernardino Mountains, about five miles north of San Bernardino. It generates electricity from water traveling through the plant from Silverwood Lake. The water is then discharged into two afterbays from which water is distributed to contracting water users. Water not delivered continues to Lake Perris through the Santa Ana Pipeline.

The Henry J. Mills Treatment Plant is located in the city of Riverside, and sits near the Box Springs foothills at an elevation of 1,650 feet, the highest of Metropolitan's five treatment plants.

The plant supplies State Water Project treated water, via gravity flow, to the Eastern and Western Municipal Water districts of Riverside County.

Mills was completed in 1978 and has been upgraded from a treatment capacity of 150 to 220 million gallons per day. It is Metropolitan's smallest treatment facility.