Just below the dam, Piru Creek returns to its natural state as it winds down through the Topatopa Mountains to feed into the Lake Piru reservoir and later the Santa Clara River. Pumps carry water from Pyramid Lake to Castaic Lake, which is the terminus of the west branch of the aqueduct. Pyramid and Castaic act as the upper and lower reservoirs for a 1,495-megawatt pumped storage hydroelectric plant.