California Aqueduct

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California Aqueduct
Kluft-Photo-Aerial-I205-California-Aqueduct-Img 0038.jpg
The Delta–Mendota Canal (left) and the California Aqueduct (right) near Tracy, California
Coordinates 37°49′47″N121°33′25″W / 37.8297°N 121.557°W / 37.8297; -121.557
Begins Clifton Court Forebay, Contra Costa County
37°49′47″N121°33′25″W / 37.82972°N 121.55694°W / 37.82972; -121.55694
EndsWest Branch
Castaic Lake, Los Angeles County
34°35′15″N118°39′25″W / 34.587379°N 118.656893°W / 34.587379; -118.656893
East Branch
Silverwood Lake, San Bernardino County
34°18′12″N117°19′12″W / 34.303457°N 117.319908°W / 34.303457; -117.319908
Coastal Branch
Lake Cachuma, Santa Barbara County
34°35′12″N119°58′52″W / 34.586656°N 119.980975°W / 34.586656; -119.980975
Official nameGovernor Edmund G. Brown California Aqueduct
Maintained by California Department of Water Resources
Total lengthTotal: 444 mi (715 km)
Main: 304 mi (489 km)
East Branch: 140 mi (230 km)
Width110 ft (34 m) max.
Height40 ft (12 m) max.
Capacity13,100 cu ft/s (370 m3/s) max
Construction start1963
OpenedCoastal Branch 1997
California Aqueduct

The Governor Edmund G. Brown California Aqueduct is a system of canals, tunnels, and pipelines that conveys water collected from the Sierra Nevada Mountains and valleys of Northern and Central California to Southern California. [2] Named after California Governor Edmund Gerald "Pat" Brown Sr., the over 400-mile (640 km) aqueduct is the principal feature of the California State Water Project.


The aqueduct begins at the Clifton Court Forebay at the southwestern corner of the Sacramento–San Joaquin River Delta. The aqueduct then heads south, eventually splitting into three branches: the Coastal Branch, ending at Lake Cachuma in Santa Barbara County; the West Branch, conveying water to Castaic Lake in Los Angeles County; and the East Branch, connecting Silverwood Lake in San Bernardino County.

The Department of Water Resources (DWR) operates and maintains the California Aqueduct, including one pumped-storage hydroelectric plant, Gianelli Power Plant. Gianelli is located at the base of San Luis Dam, which forms San Luis Reservoir, the largest offstream reservoir in the United States.

The Castaic Power Plant, while similar and which is owned and operated by the Los Angeles Department of Water and Power, is located on the northern end of Castaic Lake, while Castaic Dam is located at the southern end.

The aqueduct system

San Luis Reservoir in July 2021 Banks of San Luis Reservoir in July 2021 redux.JPG
San Luis Reservoir in July 2021

The aqueduct serves 35 million people and 5.7 million acres of farmland, [3] and begins at the San Joaquin-Sacramento River Delta at the Banks Pumping Plant, which pumps from the Clifton Court Forebay. Water is pumped by the Banks Pumping Plant to the Bethany Reservoir. The reservoir serves as a forebay for the South Bay Aqueduct via the South Bay Pumping Plant. From the Bethany Reservoir, the aqueduct flows by gravity approximately 60 mi (97 km) to the O'Neill Forebay at the San Luis Reservoir. From the O'Neill Forebay, it flows approximately 16 mi (26 km) to the Dos Amigos Pumping Plant. After Dos Amigos, the aqueduct flows about 95 mi (153 km) to where the Coastal Branch splits from the "main line". The split is approximately 16 mi (26 km) south-southeast of Kettleman City. After the coastal branch, the line continues by gravity another 66 mi (106 km) to the Buena Vista Pumping Plant. From the Buena Vista, it flows approximately 27 mi (43 km) to the Teerink Pumping Plant. After Teerink it flows about 2.5 mi (4.0 km) to the Chrisman Pumping Plant. Chrisman is the last pumping plant before Edmonston Pumping Plant, which is 13 mi (21 km) from Chrisman. South of the plant the west branch splits off in a southwesterly direction to serve the Los Angeles Basin. At Edmonston Pumping Plant it is pumped 1,926 ft (587 m) over the Tehachapi Mountains. [4]

Water flows through the aqueduct in a series of abrupt rises and gradual falls. The water flows down a long segment, built at a slight grade, and arrives at a pumping station powered by Path 66 or Path 15. The pumping station raises the water, where it again gradually flows downhill to the next station. However, where there are substantial drops, the water's potential energy is recaptured by hydroelectric plants. The initial pumping station fed by the Sacramento River Delta raises the water 240 ft (73 m), while a series of pumps culminating at the Edmonston Pumping Plant raises the water 1,926 ft (587 m) over the Tehachapi Mountains. The Edmonston Pumping station requires so much power that several power lines off of Path 15 and Path 26 are needed to ensure proper operation of the pumps. Installing solar panels on the canal (as done in India) could reduce evaporation by 27–51 thousand per kilometre of canal, and contribute electricity to the pumps. [5]

A typical section has a concrete-lined channel 40 feet (12 m) at the base and an average water depth of about 30 ft (9.1 m). The widest section of the aqueduct is 110 feet (34 m) and the deepest is 32 feet (9.8 m). Channel capacity is 13,100 cubic feet per second (370 m3/s) and the largest pumping plant capacity at Dos Amigos is 15,450 cubic feet per second (437 m3/s).


From its beginning until its first branch, the aqueduct passes through parts of Contra Costa, Alameda, San Joaquin, Stanislaus, Merced, Fresno, and Kings counties. The aqueduct then divides into three branches: the Coastal Branch in the Central Valley, and the East and West Branches after passing over the Tehachapi Mountains.

Aqueduct and surrounding farms in Kern County Kern-County-farms-and-california-aqueduct-Aerial-from-west-August-2014.jpg
Aqueduct and surrounding farms in Kern County

Coastal Branch

The Coastal Branch splits from the main line 11.3 mi (18.2 km) south-southeast of Kettleman City transiting Kings County, Kern County, San Luis Obispo County, and Santa Barbara County to deliver water to the coastal cities of San Luis Obispo, Santa Maria, and Santa Barbara. [6] Coastal Branch is 116 mi (187 km) and five pump stations. Phase I, an above ground aqueduct totals 15 mi (24 km) from where it branches from the California Aqueduct, was completed in 1968. With construction beginning in 1994, Phase II consists of 101 mi (163 km) of a 42–57-inch (1.07–1.45 m) diameter buried pipeline extending from the Devils Den Pump Plant, and terminates at Tank 5 on Vandenberg Air Force Base in Santa Barbara County. The Central Coast Water Authority (CCWA) extension, completed in 1997, is a (30–39 in) (76–99 cm) diameter pipeline that travels 42 mi (68 km) from Vandenberg through Vandenberg Village, Lompoc, Buellton, and Solvang where it terminates at Lake Cachuma in Los Padres National Forest. [7]

Coastal Branch facilities include: [8]

East Branch

The California Aqueduct East Branch, flowing east after crossing under state route 138 California Aqueduct east of route 138.jpg
The California Aqueduct East Branch, flowing east after crossing under state route 138

The aqueduct splits off into the East Branch and West Branch in extreme southern Kern County, north of the Los Angeles County line. The East Branch supplies Lake Palmdale and terminates at Lake Perris, in the area of the San Gorgonio Pass. It passes through parts of Kern, Los Angeles, San Bernardino, and Riverside counties.

East Branch facilities include: [8]

West Branch

The West Branch continues to head towards its terminus at Pyramid Lake and Castaic Lake in the Angeles National Forest to supply the western Los Angeles basin. It passes through parts of Kern and Los Angeles counties.

West Branch facilities include [8]


When it was open, the California Aqueduct Bikeway was the longest of the paved paths in the Los Angeles area, at 107 miles (172 km) long from Quail Lake near Gorman in the Sierra Pelona Mountains through the desert to Silverwood Lake in the San Bernardino Mountains. This path was closed in 1988 due to bicyclist safety and liability issues. It is expected to remain closed indefinitely due to the continued liability issues and an increased focus on security, especially after the September 11, 2001 attacks.

California Aqueduct fishing spot near Pearblossom.jpg
Fishing spot and closed bikeway near Pearblossom, panoramic view

Pumping stations

Phase I, canal
Phase II, pipeline and tunnel


Sacramento River basin map.png
Sacramento River watershed
San Joaquin River watershed.png
San Joaquin River watershed and Tulare Basin

Two major river systems drain and define the two parts of the Central Valley. Their impact on the California Aqueduct is both direct and indirect. The Sacramento River, along with its tributaries the Feather River and American River, flows southwards through the Sacramento Valley for about 447 miles (719 km). [10] In the San Joaquin Valley, the San Joaquin River flows roughly northwest for 365 miles (587 km), picking up tributaries such as the Merced River, Tuolumne River, Stanislaus River and Mokelumne River. [11]

In the south part of the San Joaquin Valley, the alluvial fan of the Kings River and another one from Coast Ranges streams have created a divide and resultantly the currently dry Tulare basin of the Central Valley, into which flow four major Sierra Nevada rivers, the Kings, Kaweah, Tule and Kern. This basin, usually endorheic, formerly filled during heavy snowmelt and spilled out into the San Joaquin River. Called Tulare Lake, it is usually dry nowadays because the rivers feeding it have been diverted for agricultural purposes. [12]

The rivers of the Central Valley converge in the Sacramento-San Joaquin Delta, a complex network of marshy channels, distributaries and sloughs that wind around islands mainly used for agriculture. Here the freshwater of the rivers merges with tidewater, and eventually reach the Pacific Ocean after passing through Suisun Bay, San Pablo Bay, upper San Francisco Bay and finally the Golden Gate. Many of the islands now lie below sea level because of intensive agriculture, and have a high risk of flooding, which would cause salt water to rush back into the delta, especially when there is too little fresh water flowing in from the Valley. [13]

The Sacramento River carries far more water than the San Joaquin, with an estimated 22 million acre-feet (27 km3) of virgin annual runoff, as compared to the San Joaquin's approximately 6 million acre-feet (7.4 km3). Intensive agricultural and municipal water consumption has reduced the present rate of outflow to about 17 million acre-feet (21 km3) for the Sacramento and 3 million acre-feet (3.7 km3) for the San Joaquin; however, these figures still vary widely from year to year. Over 25 million people, living both in the valley and in other regions of the state, rely on the water carried by these rivers. [14]

A documentary about the decline of the United States' infrastructure, The Crumbling of America, [15] was commissioned by the U.S. A&E network in the late 2000s. The documentary is typically shown on the History television channel in the United States, although other educational broadcasters globally have shown it. It features the Clifton Court Forebay (a primary intake point for California Aqueduct) as a "strategic piece of California freshwater infrastructure" subject to shutdown for up to two years if struck by an earthquake of magnitude 7.5 or greater.

The aqueduct is featured in an episode of California's Gold with Huell Howser. [16]

See also

Related Research Articles

Central Valley (California) Flat valley that dominates central California

The Central Valley is a broad, elongated, flat valley that dominates the interior of California. It is 40–60 mi (60–100 km) wide and runs approximately 450 mi (720 km) from north-northwest to south-southeast, inland from and parallel to the Pacific coast of the state. It covers approximately 18,000 sq mi (47,000 km2), about 11% of California's land area. The valley is bounded by the Coast Ranges to the west and the Sierra Nevada to the east.

Pyramid Lake (Los Angeles County, California)

Pyramid Lake is a reservoir formed by Pyramid Dam on Piru Creek in the eastern San Emigdio Mountains, near Castaic, Southern California. It is a part of the West Branch California Aqueduct, which is a part of the California State Water Project. Its water is fed by the system after being pumped up from the San Joaquin Valley and through the Tehachapi Mountains.

Metropolitan Water District of Southern California Regional wholesaler of water in Southern California

The Metropolitan Water District of Southern California is a regional wholesaler and the largest supplier of treated water in the United States. The name is usually shortened to "Met," "Metropolitan," or "MWD." It is a cooperative of fourteen cities, eleven municipal water districts, and one county water authority, that provides water to 19 million people in a 5,200-square-mile (13,000 km2) service area. It was created by an act of the California Legislature in 1928, primarily to build and operate the Colorado River Aqueduct. Metropolitan became the first contractor to the State Water Project in 1960.

History of California 1900–present Overview of the history of California from 1900 to today

This article continues the history of California in the years 1900 and later. For events through 1899, see History of California before 1900.

The South Bay Aqueduct is an aqueduct located in the eastern part of the San Francisco Bay Area. It conveys water from the Sacramento-San Joaquin Delta through over forty miles of pipelines and canals. It begins in north-eastern Alameda County on the California Aqueduct's Bethany Reservoir serving as the forebay. The aqueduct flows along the eastern and southern edges of the Livermore Valley. Then it flows through a series of tunnels to an end in the foothills of eastern San Jose, 5 miles (8 km) from downtown San Jose, California.

Delta–Mendota Canal

The Delta–Mendota Canal is a 117-mile-long (188 km) aqueduct in central California, United States. The canal was designed and completed in 1951 by the U.S. Bureau of Reclamation as part of the Central Valley Project to supply freshwater to users downstream of the San Joaquin River. Freshwater is diverted into the Madera Canal and Friant-Kern Canal at Friant Dam.

Castaic Dam Dam in northwest Los Angeles County, California, United States

Castaic Dam is an embankment dam in northwestern Los Angeles County, California, in the unincorporated area of Castaic. Although located on Castaic Creek, a major tributary of the Santa Clara River, Castaic Creek provides little of its water. The lake is the terminus of the West Branch of the California Aqueduct, part of the State Water Project. The dam was built by the California Department of Water Resources and construction was completed in 1973. The lake has a capacity of 325,000 acre-feet (401,000,000 m3) and stores drinking water for the western portion of the Greater Los Angeles Area.

San Luis Dam Dam in Merced County, California

San Luis Dam is a major earth-filled dam in Merced County, California, which forms San Luis Reservoir, the largest off-stream reservoir in the United States. The dam and reservoir are located in the Diablo Range to the east of Pacheco Pass and about 10 miles (16 km) west of Los Banos. San Luis Dam, a jointly-owned state and federal facility, stores more than 2 million acre feet (2.5 km3) of water for the California State Water Project and the federal Central Valley Project. Although the dam is located in the valley of San Luis Creek, the majority of its water comes from man-made aqueducts which are supplied from other rivers in Northern California.

California Department of Water Resources

The California Department of Water Resources (DWR) is part of the California Natural Resources Agency and is responsible for the management and regulation of the State of California's water usage. The department was created in 1956 by Governor Goodwin Knight following severe flooding across Northern California in 1955, where they combined the Division of Water Resources of the Department of Public Works with the State Engineer's Office, the Water Project Authority, and the State Water Resources Board. It is headquartered in Sacramento.

San Luis Reservoir

The San Luis Reservoir is an artificial lake on San Luis Creek in the eastern slopes of the Diablo Range of Merced County, California, approximately 12 mi (19 km) west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its north shore. It is the fifth largest reservoir in California. The reservoir stores water taken from the San Joaquin-Sacramento River Delta. Water is pumped uphill into the reservoir from the O'Neill Forebay which is fed by the California Aqueduct and is released back into the forebay to continue downstream along the aqueduct as needed for farm irrigation and other uses. Depending on water levels, the reservoir is approximately nine miles long from north to south at its longest point, and five miles (8 km) wide. At the eastern end of the reservoir is the San Luis Dam, or the B.F. Sisk Dam, the fourth largest embankment dam in the United States, which allows for a total capacity of 2,041,000 acre-feet (2,518,000 dam3). Pacheco State Park lies along its western shores.

California State Water Project Flood control, energy production, and water conveyance infrastructure in California

The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 23 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh.

Castaic Creek

Castaic Creek is a 25.0-mile-long (40.2 km) stream in the Sierra Pelona Mountains, in northeastern Los Angeles County, California. It is a tributary of the Santa Clara River.

Castaic Lake Man-made reservoir in California, United States

Castaic Lake is a reservoir formed by Castaic Dam on Castaic Creek, in the Sierra Pelona Mountains of northwestern Los Angeles County, California, United States, near the town of Castaic.

The North Bay Aqueduct (NBA) is part of the California State Water Project. The aqueduct is 27.4 miles (44.1 km) long all in pipelines and serves Napa and Solano counties, California.

The Harvey O. Banks Pumping Plant is located 2.5 miles (4 km) southwest of the Clifton Court Forebay and 12 miles (19 km) northwest of Tracy, CA. The plant is the first pumping plant for the California Aqueduct and the South Bay Aqueduct. It provides the necessary fluid head for the California Aqueduct to flow for approximately 80 miles (130 km) south past the O'Neill Forebay and the San Luis Reservoir to the Dos Amigos Pumping Plant. The Banks Pumping Plant initially flows into the Bethany Reservoir. It is from the Bethany Reservoir that the South Bay Aqueduct begins.

The Peripheral Canal was a series of proposals starting in the 1940s to divert water from California's Sacramento River, around the periphery of the San Joaquin-Sacramento River Delta, to uses farther south. The canal would have attempted to resolve a problem with the quality of water pumped south. Pumps create such a powerful suction that the boundary between freshwater to saltwater has shifted inland, negatively affecting the environment. The pumps have increased by 5 to 7 million acre-feet the amount of water exported each year to the Central Valley and Southern California. However, the peripheral canal as proposed would have reduced the overall freshwater flow into the Delta and move the freshwater-saltwater interface further inland, causing damage to Delta agriculture and ecosystems.

Castaic Power Plant Dam in Los Angeles County, California

Castaic Power Plant, also known as the Castaic Pumped-Storage Plant, is a seven unit pumped-storage hydroelectric plant, operated by the Los Angeles Department of Water and Power, which provides peak load power from the falling water on the West Branch of the California State Aqueduct. It is a cooperative venture between the LADWP and the Department of Water Resources of the State of California. An agreement between the two organizations was signed on September 2, 1966, for construction of the project.

Elderberry Forebay

Elderberry Forebay is a small reservoir in Los Angeles County, California, which serves as the pumping forebay of the Castaic Power Plant. It located at the upper end of the larger Castaic Lake and is separated from the lake by Elderberry Forebay Dam at its southern edge. Entering the northern end of the forebay is the west branch of the California Aqueduct, which connects the forebay to Pyramid Lake through the Angeles Tunnel.

Angeles Tunnel

The Angeles Tunnel is a 7.2-mile-long (11.6 km), 30-foot-diameter (9.1 m) water tunnel located in the Sierra Pelona Mountains in Los Angeles County, California, about 50 miles (80 km) north of Los Angeles. It was constructed between 1967 and 1970 as part of the California State Water Project and serves as the final leg of the west branch of the California Aqueduct, which carries Northern California water to Southern California residents.

Buena Vista Pumping Plant is a water pumping plant of the California State Water Project, located 22 miles southwest of Bakersfield, within Kern County, in the San Joaquin Valley, central California.


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  2. DWR Public Affairs Office (2005). "State Water Project Today". Department of Water Resources, State of California. Archived from the original on 2007-06-10. Retrieved 2009-03-19.
  3. Simon, Matt (19 March 2021). "Why Covering Canals With Solar Panels Is a Power Move". Wired. Archived from the original on 4 May 2021.
  4. "Edmonston Pumping Plant". Center for Land Use Interpretation. 2009. Archived from the original on 2008-07-24. Retrieved 2009-03-19.
  5. McKuin, Brandi; Zumkehr, Andrew; Ta, Jenny; Bales, Roger; Viers, Joshua H.; Pathak, Tapan; Campbell, J. Elliott (2021-03-18). "Energy and water co-benefits from covering canals with solar panels". Nature Sustainability. doi:10.1038/s41893-021-00693-8. S2CID   232273487.
  6. Carle, David (2004). Introduction to Water in California . Berkeley: University of California Press. pp.  97–99. ISBN   0-520-23580-0.
  7. "State Water Project in Santa Barbara County". Central Coast Water Authority. 10 March 2003. Archived from the original on 11 December 2009. Retrieved 2009-03-22.
  8. 1 2 3 "Facilities". California Department of Water Resources. April 7, 2019.
  9. 1 2 "Coastal Branch Brochure" (PDF). California Department of Water Resources.
  10. "Sacramento River Basin National Water Quality Assessment Program: Study Unit Description". United States Geological Survey . Retrieved 2009-07-26.
  11. "Restoring the San Joaquin River: Following an 18-year legal battle, a great California river once given up for dead is on the verge of a comeback". Natural Resources Defense Council. 17 September 2007. Retrieved 2009-07-26.
  12. Gorelick, Ellen. "Tulare Lake". Tulare Historical Museum. Archived from the original on 2010-02-19. Retrieved 2009-07-26.
  13. "Delta Subsidence in California: The sinking heart of the State" (PDF). United States Geological Survey . Retrieved 2009-07-26.
  14. "Sacramento-San Joaquin River System, California". American Rivers. America's Most Endangered Rivers Report: 2009 Edition. Archived from the original on 2010-01-17. Retrieved 2009-07-26.
  15. "The Crumbling of America (2:49 introductory clip)" . Retrieved 2013-09-11.
  16. "California Aqueduct Special – California's Gold (001) – Huell Howser Archives at Chapman University".