California Aqueduct

California Aqueduct

The Delta–Mendota Canal (left) and the California Aqueduct (right) near Tracy, California
Official name Governor Edmund G. Brown California Aqueduct
Begins Clifton Court Forebay, Contra Costa County
37°49′48″N 121°33′25″W / 37.829927°N 121.556894°W / 37.829927; -121.556894
Ends West Branch
Castaic Lake, Los Angeles County
34°35′15″N 118°39′25″W / 34.587379°N 118.656893°W / 34.587379; -118.656893
East Branch
Silverwood Lake, San Bernardino County
34°18′12″N 117°19′12″W / 34.303457°N 117.319908°W / 34.303457; -117.319908
Coastal Branch
Lake Cachuma, Santa Barbara County
34°35′12″N 119°58′52″W / 34.586656°N 119.980975°W / 34.586656; -119.980975
Maintained by California Department of Water Resources
Length 701.5 mi (1,129.0 km)
Conduit height 33 m (108 ft) max.
Conduit width 10 m (33 ft) max.
Capacity 370 m3/s (13,000 cu ft/s)
Construction began 1963
Opening date Coastal Branch 1997
References: [1]

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] The over 400-mile (640 km) aqueduct is the principal feature of the California State Water Project.

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.

Geological context

The Central Valley of California is surrounded by high mountains that are eroding into the valley itself. The valley is somewhat rebounding from recent ice age interglacial glaciations. The region is prone to significant earthquakes due to the many faults and fault lines that pass through the region.

The flatness of the valley bottom contrasts with the rugged hills or gentle mountains that are typical of most of California's terrain. The valley is thought to have originated below sea level as an offshore area depressed by subduction of the Farallon Plate into a trench further offshore. The San Joaquin Fault is a notable seismic feature of the Central Valley.

An example of the extreme differences between the geology of the valley floor and that of the rugged hills of the Coast Ranges (Between Tracy and Patterson, CA:Interstate 5)

The valley was later enclosed by the uplift of the Coast Ranges, with its original outlet into Monterey Bay. Faulting moved the Coast Ranges, and a new outlet developed near what is now San Francisco Bay.

Over the millennia, the valley was filled by the sediments of these same ranges, as well as the rising Sierra Nevada to the east; that filling eventually created an extraordinary flatness just barely above sea level; before California's massive flood control and aqueduct system was built, the annual snow melt turned much of the valley into an inland sea.

The aqueduct system

The aqueduct 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.[3]

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.

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).

Branches

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.[4] 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.[5]

East Branch

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.

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.

Bikeway

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 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.

Pumping stations

Phase I, Canal
Phase II, Pipeline and Tunnel

Hydrography

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).[6] 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.[7]

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.[8]

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.[9]

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.[10]

A documentary about the decline of the United States' infrastructure, The Crumbling of America,[11] 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.

See also

References

  1. ↑ U.S. Geological Survey (19 January 1981). "Feature Detail Report: Governor Edmund G Brown California Aqueduct". Geographic Names Information System (GNIS). U.S. Department of the Interior. Retrieved 2009-03-19.
  2. ↑ DWR Public Affairs Office (2005). "State Water Project Today". Department of Water Resources, State of California. Retrieved 2009-03-19.
  3. ↑ "Edmonston Pumping Plant". Center for Land Use Interpretation. 2009. Retrieved 2009-03-19.
  4. ↑ Carle, David (2004). Introduction to Water in California. Berkeley: University of California Press. pp. 97–99. ISBN 0-520-23580-0.
  5. ↑ "State Water Project in Santa Barbara County". Central Coast Water Authority. 10 March 2003. Retrieved 2009-03-22.
  6. ↑ "Sacramento River Basin National Water Quality Assessment Program: Study Unit Description". United States Geological Survey. ca.water.usgs.gov. Retrieved 2009-07-26.
  7. ↑ "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. www.nrdc.org. 17 September 2007. Retrieved 2009-07-26.
  8. ↑ Gorelick, Ellen. "Tulare Lake". Tulare Historical Museum. www.tularehistoricalmueseum.org. Archived from the original on 2010-02-19. Retrieved 2009-07-26.
  9. ↑ "Delta Subsidence in California: The sinking heart of the State" (PDF). United States Geological Survey. ca.water.usgs.gov. Retrieved 2009-07-26.
  10. ↑ "Sacramento-San Joaquin River System, California". American Rivers. America's Most Endangered Rivers Report: 2009 Edition. Retrieved 2009-07-26.
  11. ↑ "The Crumbling of America (2:49 introductory clip)". Retrieved 2013-09-11.
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