|Location||Ventura County, California|
|Primary inflows||Coyote Creek|
|Primary outflows||Coyote Creek|
|Catchment area||39 sq mi (100 km2)|
|Basin countries||United States|
|Managing agency||Casitas Municipal Water District|
|Max. length||3.3 mi (5.3 km)|
|Max. width||1.9 mi (3 km)|
|Surface area||1,100 acres (450 ha)|
|Max. depth||240 feet (73 m)|
|Water volume||254,000 acre⋅ft (313,000,000 m3)|
|Shore length1||32.4 miles (52.1 km)|
|Surface elevation||338 ft (103 m)|
|Settlements||Oak View, Ojai|
|References||U.S. Geological Survey Geographic Names Information System: Lake Casitas|
|1 Shore length is not a well-defined measure.|
Lake Casitas is a reservoir in Ventura County, California, built by the United States Bureau of Reclamation and completed in 1959. The project provides drinking water and water for irrigation. A secondary benefit is flood control.
Casitas Dam was constructed on Coyote Creek, two miles (3 km) before it joins the Ventura River. Santa Ana Creek and North Fork Coyote Creek also flow into the lake. 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. The dam is 279 ft (85 m) creating a lake capacity of 254,000 acre⋅ft (313,000,000 m3). The dam was built as part of the Ventura River Project. In the center of Lake Casitas is 2 km Main Island, whose peak rises more than 500 feet (150 m) from the lake surface.
The lake filled and overflowed for the first time around the 1970s.
The Casitas Municipal Water District provides drinking water to the Ojai Valley, parts of Ventura, and the Rincon coast north of Ventura.
The Robles Diversion Dam was constructed on the Ventura River in 1958 to divert up to 107,800-acre-foot of water (133,000,000-cubic-metre) per year through a four-and-a-half mile canal (7.2 kilometres) to the reservoir. About 40% of the total water in Lake Casitas is supplied from high winter flows in the Ventura River.
Human contact with the water is prohibited by the Board of Directors at the Casitas Municipal Water District. The board states that since the Lake is used for drinking water, body contact with water is not allowed, but fishing, boating, rowing and camping are permitted.
The "no body contact with water" lake policy was established by The Casitas Municipal Water District in the 1950s and 1960s because the lake did not have a filtration system in place. In the 1990s a multimillion-dollar filtration system upgrade was made to the Lake Casitas facility. The US Department of the Interior conducted a 10-year study on the lake where allowing body contact with water was explored. The study reported, "The capabilities of the current water filtration system to handle the additional burden of body contact were called into question. The system was shown to exceed current regulatory standards, and would “probably” be sufficient to mitigate body contact pollution as well." The Casitas Municipal Water District has not significantly changed the "no body contact with water" regulations in response to the facilities upgrade.
- List of dams and reservoirs in California
- List of lakes in California
- List of largest reservoirs of California
- Carlson, Cheri (April 4, 2016). "Drought uncovers family history buried under Lake Casitas". Ventura County Star. Archived from the original on March 30, 2019. Retrieved April 5, 2016.
- Boyd-Barrett, Claudia (September 8, 2014). "Ventura leans on lake for water for eastern half of city". Ventura County Star.
- Staff (April 17, 2015). "Lake Casitas just 50 percent full". Ventura County Star.
- Carlson, Cheri (March 12, 2019). "Lake Casitas gets OK to divert more water just as it passes the mark to do so". Ventura County Star. Archived from the original on March 29, 2019. Retrieved March 16, 2019.
- Carlson, Cheri (April 18, 2016). "No rain could mean Lake Casitas runs dry in four years". Ventura County Star. Retrieved 22 August 2016.
- Carlson, Cheri (November 10, 2017). "As Lake Casitas shrinks, a search is on for untapped water supplies". Ventura County Star. Archived from the original on March 30, 2019. Retrieved November 11, 2017.
- Apr 19; Story, 2017 | Cover; Coates, Crawford; Feature; Stolz, Kit; Ojai; Ventura | 0 | (2017-04-20). "ALL THAT THE RAIN PROMISES | Questions remain as western Ventura moves toward a state water connection". VC Reporter | Southland Publishing. Retrieved 2019-05-24.
- 1984 Summer Olympics official report. Archived 2010-11-02 at the Wayback Machine Volume 1. Part 1. pp. 108–12.
- Carlson, Cheri (March 28, 2019). "Thomas Fire fallout blamed for second 'critical shutdown' at Lake Casitas facility". Ventura County Star. Retrieved 29 March 2019.
- Carlson, Cheri (August 29, 2018). "Drought-stricken western Ventura County may need more than planned $45M pipeline as a fix". Ventura County Star. Archived from the original on March 30, 2019. Retrieved August 30, 2018.
- "Robles Dam". U.S. Department of Interior Bureau of Reclamation. June 4, 2009. Retrieved March 16, 2013.
- Bureau of Reclamation (February 2010) "Lake Casitas Resource Management Plan/Environmental Impact Statement" United States Department of the Interior
- Bureau of Reclamation (2009). "Ventura River Project". U.S. Department of the Interior. Archived from the original on 2015-07-19. Retrieved 2009-09-29.
- Department of Water Resources (2009). "Station Meta Data: Lake Casitas (CSI)". California Data Exchange Center. State of California. Retrieved 2009-10-11.
- U.S. Geological Survey (13 June 2000). "Feature Detail Report: Main Island". Geographic Names Information System (GNIS). U.S. Department of the Interior. Retrieved 2009-10-12.
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