The Santa Maria Valley Water Conservation District oversees the maintenance and operations of Twitchell Dam. It helps recharge the groundwater basin and provides some protection from flooding.
About the Twitchell Dam
"Twitchell Reservoir is a reservoir in southern San Luis Obispo County, California. The reservoir has a capacity of 224,300 acre feet and is formed by Twitchell Dam on the Cuyama River about 66 miles from its headwaters in the Chumash Wilderness Area and about 6miles from its confluence with the Sisquoc River, where they form the Santa Maria River. Twitchell dam was built by the United States Bureau of Reclamation between 1956 and 1958. The original names were Vacquero Dam and Vacquero Reservoir, but they were changed to honor T. A. Twitchell of Santa Maria, a proponent of the project.
The dam and reservoir provide flood control and water conservation. The Central Coast of California only receives significant amounts of rainfall during the winter, this area averaging 14inches per year.
The water is stored in the reservoir during big winter storms and released as quickly as possible while still allowing it to percolate into the soil and recharge the groundwater. This means that the reservoir is usually far from full. It is estimated that the project increases reacharge by 20,000 acre feet per year."