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.[4] 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

The aqueduct serves 35 million people and 5.7 million acres of farmland,[5] 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.[6]

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.[7]

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

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.[8] 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.[9]

Coastal Branch facilities include:[10]

  • Las Perillas Pumping Plant
  • Badger Hill Pumping Plant
  • Devil's Den Pumping Plant
  • Bluestone Pumping Plant
  • Polonia Pass Pumping Plant
  • Polonio Pass Water Treatment Plant
  • Cuesta Tunnel[11]
  • Santa Ynez Pumping Facility[11]

East Branch

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:[10]

  • Pearblossom Pumping Plant
  • Alamo Power Plant
  • Mojave Siphon Power Plant
  • San Bernardino Tunnel
  • Devil Canyon Power Plant
  • Greenspot Pump Station
  • Crafton Hills Reservoir
  • Crafton Hills Pump Station
  • Cherry Valley Pump Station

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[10]

  • Oso Pumping Plant
  • Peace Valley Pipeline
  • Warne Powerplant
  • Angeles Tunnel
  • Castaic Power Plant


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.

Fishing spot and closed bikeway near Pearblossom, panoramic view

Pumping stations

Phase I, canal
Phase II, pipeline and tunnel


Sacramento River watershed
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).[12] 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.[13]

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.[14]

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.[15]

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.[16]

In popular culture

A documentary about the decline of the United States' infrastructure, The Crumbling of America,[17] 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.[18]

See also


  1. ^ East Branch Aqueduct
  2. ^ California Aqueduct
  3. ^ U.S. Geological Survey – GNIS (19 January 1981). "Feature Detail Report: Governor Edmund G Brown California Aqueduct". U.S. Department of the Interior. Retrieved 2009-03-19.
  4. ^ 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.
  5. ^ Simon, Matt (19 March 2021). "Why Covering Canals With Solar Panels Is a Power Move". Wired. Archived from the original on 4 May 2021.
  6. ^ "Edmonston Pumping Plant". Center for Land Use Interpretation. 2009. Archived from the original on 2008-07-24. Retrieved 2009-03-19.
  7. ^ 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. 4 (7): 609–617. doi:10.1038/s41893-021-00693-8. S2CID 232273487.
  8. ^ Carle, David (2004). Introduction to Water in California. Berkeley: University of California Press. pp. 97–99. ISBN 0-520-23580-0.
  9. ^ "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.
  10. ^ a b c "Facilities". California Department of Water Resources. April 7, 2019.
  11. ^ a b "Coastal Branch Brochure" (PDF). California Department of Water Resources.
  12. ^ "Sacramento River Basin National Water Quality Assessment Program: Study Unit Description". United States Geological Survey. Retrieved 2009-07-26.
  13. ^ "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.
  14. ^ Gorelick, Ellen. "Tulare Lake". Tulare Historical Museum. Archived from the original on 2010-02-19. Retrieved 2009-07-26.
  15. ^ "Delta Subsidence in California: The sinking heart of the State" (PDF). United States Geological Survey. Retrieved 2009-07-26.
  16. ^ "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.
  17. ^ "The Crumbling of America (2:49 introductory clip)". YouTube. Retrieved 2013-09-11.
  18. ^ "California Aqueduct Special – California's Gold (001) – Huell Howser Archives at Chapman University".

External links