Twitchell Dam is a U.S. Bureau of Reclamation facility that is part of the Santa Maria Project in the coastal region of central California. Twitchell Dam and Reservoir are located on the Cuyama River, which along with the Sisquoc River, forms the Santa Maria River approximately 8 miles downstream from the dam. Twitchell Dam is a multiple-purpose structure for water conservation and flood control. Water conservation is achieved by storing inflows in the reservoir below the flood control pool and making subsequent releases for percolation into the Santa Maria River aquifer.
Twitchell Dam was authorized by the Flood Control Act of 1954 (Public Law 83-774, 3 September 1954). Construction of Twitchell Dam began in 1956 and was conpleted in 1958. Along with the construction of Twitchell Dam, the Corps of Engineers was authorized to plan and construct flood control improvements along the Santa Maria River downstream from the dam. The authorization was contained in Public Law 83-780, 3 September 1954. The flood control improvements consisted of a series of levees, constructed between 1959 and 1961. Both Twitchell Dam and the Santa Maria River levees were recommended in House Document No. 400, 83rd Congress, 2nd Secssion, dated May 24, 1954.
The curent approved water control manual (WCM) for Twitchell Dam and Reservoir is dated August 1960. The WCM is scheduled for revision in 2005.