The San Luis Joint-Use Complex serves the State Water Project and the federal Central Valley Project. It was designed and constructed by the Bureau of Reclamation and is operated and maintained by the Department of Water Resources. San Luis Reservoir, part of the San Luis Complex, is the largest off-stream reservoir in the United States.
The O'Neill Forebay in Merced County marks the start of the San Luis Joint-Use Facilities. The state and federal complex includes O'Neill Forebay, San Luis Reservoir, Sisk Dam, Gianelli Pumping-Generating Plant, Romero Overlook Visitors Center, San Luis Canal, Dos Amigos Pumping Plant, and two smaller detention dams and reservoirs.
B.F. Sisk San Luis Dam & San Luis Reservoir
San Luis Reservoir, impounded by Sisk Dam, lies at the base of the foothills on the west side of the San Joaquin Valley in Merced County, about 2 miles west of O'Neill Forebay. The reservoir provides off-stream storage for excess winter and spring flows diverted from the Sacramento-San Joaquin Delta. It is designed to provide seasonal carryover storage.
San Luis Reservoir can hold 2,027,840 acre-feet, of which 1,062,180 acre-feet is the state's share and 965,660 acre-feet is the federal share for the Central Valley Project. Construction began in 1963 and was completed in 1967. Filled in 1969, the reservoir also provides a variety of recreational activities, as well as fish and wildlife benefits.
Los Banos Detention Dam & Reservoir
Los Banos Detention Dam and reservoir provide flood protection for San Luis Canal, Delta-Mendota Canal, the city of Los Banos, and other downstream developments. Between September and March, 14,000 acre-feet of space is maintained for flood control under specified conditions. The facility is located on the west side of the San Joaquin Valley in Merced County.
O' Neill Forebay and Dam
Along the western side of the San Joaquin Valley in Merced County, the California Aqueduct enters O'Neill Forebay from the north. Water from the Delta-Mendota Canal, part of the federal Central Valley Project, is pumped into the forebay by the O'Neill Pump-Generation Plant. Constructed between 1963 and 1967, O'Neill Forebay offers a variety of recreational activities including camping, boating, windsurfing, and fishing.
Little Panoche Detention Dam & Reservoir
Situated in Fresno County, 20 miles southwest of the city of Los Banos, Little Panoche Detention Dam and Reservoir provide flood protection for San Luis Canal, Delta-Mendota Canal, and other downstream developments. Water is stored behind the dam above dead storage of 315 acre-feet only during the period that inflow from Little Panoche Creek exceeds the capacity of the outlet works. Construction of the facility occurred between 1965 and 1966.
William R. Gianelli Pumping-Generating Plant
Located about 12 miles west of the city of Los Banos adjacent to State Highway 152, the Gianelli Pumping-Generating Plant pumps water from O'Neill Forebay into San Luis Reservoir. Water is released through the plant in generating mode when service area demands are in excess of direct Delta diversions. Construction of the plant began in 1963 and was completed in 1967.
Dos Amigos Pumping Plant
Dos Amigos Pumping Plant is located on the San Luis Canal, about 10 miles south of the city of Los Banos and 18 miles southeast of Sisk Dam in Merced County. It lifts water 113 feet from the aqueduct as it flows south from O'Neill Forebay. The plant's construction began in 1963 and was completed in 1966.
San Luis Canal, a segment of the California Aqueduct, begins on the southeast edge of O'Neill Forebay and extends about 101.5 miles southeasterly to a point near Kettleman City. It substantially parallels Interstate Highway 5 located on the western side of the San Joaquin Valley at the eastern flank of the Coast Ranges.
Water from the canal serves the San Luis federal service area, mostly for agricultural purposes and for some municipal and industrial uses.
SWP water is conveyed through the an Luis Canal to Check 21, where the joint-use facilities and and the California Aqueduct continues. The canal was constructed from 1963 to 1968.