Located at the juncture of the north and south forks of the American River, the dam was built by the United States Army Corps of Engineers, and was transferred to the United States Bureau of Reclamation upon its completion. The dam and its reservoir, Folsom Lake, are part of the Central Valley Project, a multipurpose project that provides flood control, hydroelectricity, and irrigation and municipal water supply. In order to increase Sacramento's flood protection to 200 year flood protection (meaning that the area is protected from a flood that has a 0.5% chance of occurring in any given year) the US Army Corps of Engineers recently constructed an auxiliary spillway, which was completed in October 2017 and enables Folsom Dam operators to increase outflows to prevent lake level from reaching or exceeding the height of the main dam gates.