The flow of the Ventura River and its tributary Coyote Creek have been reduced by the completion of Casitas Dam, which forms Casitas Reservoir. The dam is on Coyote Creek about 2 miles upstream of the junction with the Ventura River. The Robles Diversion Dam was constructed on the Ventura River in 1958 to divert up to 107,800 acre-feet of water per year through a four-and-a-half mile canal to Casitas Reservoir. About 40% of the total water in Lake Casitas is supplied from high winter flows in the Ventura River. Casitas Municipal Water District sells water to both domestic and agricultural customers.