The O’Neill Forebay is a small pumped storage operation that is part of the San Luis Complex, which consists of two reservoirs and two pump/generator plants, located on the west side of the Central Valley. The forebay is a shallow reservoir that exists primarily to supply water to the William R. Gianelli Pumping-Generating Plant, which lifts water 300 feet up into the San Luis Reservoir. The forebay is fed by two canals, one state, and one federal. The state canal is the California Aqueduct, which brings water from the Delta in northern California, to central and southern California. The California Aqueduct enters the forebay from the north, and leaves from the south, with gates that regulate its flow in and out. The Federal canal feeding the forebay is the Bureau of Reclamation’s Delta-Mendota Canal, which brings water from the Delta in Northern California to the farms throughout the Central Valley. The forebay has a small pumping-generating plant that lifts water 50 feet up out of the Delta-Mendota Canal, and generates 25 megawatts when it lets water back into it, though it is only occasionally used for this.