Lake Casitas is a reservoir in Ventura County, California, built by the United States Bureau of Reclamation and completed in 1959.

The system was designed for water from the Ventura River to be diverted into a canal under specific conditions since the impounded watershed is not sufficient to fill the lake.

[9] The Thomas Fire at the end of 2017 had a significant impact on operations since the wildfire burned a large area within the watershed of the Ventura River.

[10] Rainstorms brought a lot of ash, sandy silt, gravel, and debris into the Robles diversion facility that had collected over several years since the fire resulting in some temporary shutdowns of water from the Ventura River.

[15] The Robles Diversion Dam was constructed on the Ventura River in 1958 to divert up to 107,800 acre-feet (133,000,000 cubic meters) of water per year through a 4.5-mile (7.2 km) canal to the reservoir.

The study reported, "The capabilities of the current water filtration system to handle the additional burden of body contact were called into question.