Trinity Dam was the main storage feature of the Central Valley Project (CVP) proposal to divert water from the Trinity River in northwestern California to augment water supplies in the CVP service area. In 1948, the U.S. Bureau of Reclamation, which was responsible for the construction and operations of most CVP facilities, devised a plan of four dams and two tunnels to capture and store some of the flow of the Trinity River and transport it to the Sacramento River, generating a net surplus of hydroelectric power along the way. Trinity Dam was the main storage feature of the division, providing a stable flow to the Lewiston Dam, the diversion point for Trinity River waters into the Central Valley via the Trinity Tunnel. Trinity Lake was completely filled with water from the Trinity River by 1963, becoming the third largest lake in California, with of shoreline.