Encino Reservoir
The Encino Reservoir, is a controlled lake created by the damming of Encino creek.[1] It is located near the Encino neighborhood in the San Fernando Valley, California. With construction completed in 1924, it is owned by the Los Angeles Department of Water and Power (LADWP).[2]
History
[edit]The reservoir was commissioned in 1924 by the civil engineer William Mulholland to supply drinking water to the population of the San Fernando Valley.[3]
A roll-filled dam construction method, one where earth and rock is moved into place in layers and then compacted to create an embankment, was used.[4][5] After the first filling, there was seepage from the dam.[4] Between 1949 and 1950, rectification of this problem was made in the form of a downstream filter and buttress.[4] Between 1960 and 1962 the up-stream part of the original dam, and its alluvium down to bedrock, was removed and a new 51.2 m (168 feet) earth roll-filled dam was constructed.[4]
Prior to 1971, the Encino reservoir together with the Lower Stone Canyon and Lower Van Norman reservoirs provided 70 percent of the water stored within the jurisdiction of the LADWP. In comparison, 80 percent of water needs of Los Angeles were provided from snowmelt at the eastern slopes of the Sierra Nevada draining into the Owens Valley and from there through the Los Angeles Aqueduct system.[6]
The Encino Reservoir was not damaged in the 1971 San Fernando earthquake. However, afterwards, the reservoir's role in supply of water during emergencies was closely examined.[6] [4]
Geography
[edit]The reservoir is located in the hills of the north face of the Santa Monica Mountains, south of Encino neighborhood. The reservoir lies at 327 m above sea level. The surface area is 0.69 km2 and the drainage basin is 3.63 km2.[7] The reservoir is found on the United States Geological Survey topographic map Canoga Park area.[8]
The reservoir's geology involves poorly consolidated and consolidated conglomerate sandstone and basalt.[9]
Dam construction
[edit]The Encino reservoir is held by an earth roll-filled dam of 564 m width and 51 m height. The hydraulic height is 47.2 m. The maximum volume is 1.23 megaliters.[7]
Management and risk
[edit]The reservoir is inspected yearly. In 2025, its condition is listed as satisfactory while its hazard potential classification is high.[7] The "high" level means "failure or mis-operation will probably cause loss of human life".[1]
1994 Northridge earthquake
[edit]At 4.30 a.m. pacific time, the 1994 Northridge earthquake epicenter formed 7.2 km north of the Encino Reservoir. [4] The ruptured fault plane was 17.7 km (11 miles) from the dam.[4] The peak horizontal ground acceleration was 0.23 g which caused no significant damage to the Encino dam. There was some cracking of the asphalt concrete at the dam top and on a downstream access road.[4]
Uses
[edit]The Encino reservoir no longer provides drinking water. However, it is kept open for other uses.[1]
Emergency uses
[edit]Recreational uses
[edit]References
[edit]- ^ a b c "Encino Dam, California, USA | Info & Map". 2024-07-20. Retrieved 2025-02-10.
- ^ Crosby, Michael (2009). Images of America - Encino. Arcadia Publications. p. 98. ISBN 9780738569918.
- ^ https://www.smithsonianmag.com/history/occasions-i-envy-dead-st-francis-dam-disaster-180954543/
- ^ a b c d e f g h Stewart, J.P., ed. (June 1994). "Encino Reservoir". Preliminary report on the principal geotechnical aspects of the January 17, 1994 Northridge earthquake. Earthquake Engineering Research Center, College of Engineering, University of California, Berkley. p. 176.
- ^ Challa, S.N. (2002). Water resource engineering - principles and practice (2nd revised ed.). New Delhi: New Age International Ltd. p. 232. ISBN 9788122413823.
- ^ a b Federal Disaster Assistance Administration (27 May 1975). Los Angeles Dam and Reservoir Project (Draft ed.). San Francisco: U.S. Department of Housing and Urban Development. pp. I-B-3.
- ^ a b c "Encino in Los Angeles County, CA". The Californian. Retrieved 2025-02-10.
- ^ "Encino Reservoir Topo Map CA, Los Angeles County (Canoga Park Area)". www.topozone.com. Retrieved 2025-02-10.
- ^ Rubey, W.W. (1930). "Geology of eastern part of Santa Monica mountains, California". Lithologic studies of fine-grained upper cretaceous sedimentary rocks of the Black Hills region. U.S. Geological Survey. p. 98.
34°08′42″N 118°30′51″W / 34.14500°N 118.51417°W
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