California Aqueduct
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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 Central California is generally thought of as the middle third of the state, north of Southern California, which includes Los Angeles, and south of Northern California, which includes San Francisco. It includes the northern portion of the S ...
to
Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...
. Named after California Governor Edmund Gerald "Pat" Brown Sr., the over aqueduct is the principal feature of the
California State Water Project 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 wate ...
. The aqueduct begins at the Clifton Court Forebay at the southwestern corner of the
Sacramento–San Joaquin River Delta The Sacramento–San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in Northern California. The Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San ...
. The aqueduct then heads south, eventually splitting into three branches: the Coastal Branch, ending at
Lake Cachuma Cachuma Lake is a reservoir in the Santa Ynez Valley of central Santa Barbara County, California on the Santa Ynez River adjoining the north side of California State Route 154. The artificial lake was created by the construction of Bradbury Dam, ...
in
Santa Barbara County Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barba ...
; the West Branch, conveying water to
Castaic Lake Castaic Lake (Chumash: ''Kaštiq'') 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 California Office of Enviro ...
in
Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is the ...
; and the East Branch, connecting
Silverwood Lake Silverwood Lake is a large reservoir in San Bernardino County, California, United States, located on the West Fork Mojave River, a tributary of the Mojave River in the San Bernardino Mountains. It was created in 1971 as part of the State Water Pr ...
in
San Bernardino County San Bernardino County (), officially the County of San Bernardino, is a county located in the southern portion of the U.S. state of California, and is located within the Inland Empire area. As of the 2020 U.S. Census, the population was 2,181, ...
. The Department of Water Resources (DWR) operates and maintains the California Aqueduct, including one
pumped-storage hydroelectric Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...
plant,
Gianelli Power Plant The Gianelli Power Plant, also known as the San Luis Power Plant, is a pumped-storage hydroelectric plant that is at the base of the San Luis Dam in California. During the wet season, turbines pump water from the O'Neill Forebay into the reservoir ...
. Gianelli is located at the base of
San Luis Dam 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 ab ...
, which forms
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 west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its north ...
, the largest offstream
reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...
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 The Los Angeles Department of Water and Power (LADWP) is the largest municipal utility in the United States with 8,100 megawatts of electric generating capacity (2021-2022) and delivering an average of 435 million gallons of water per day to more ...
, is located on the northern end of
Castaic Lake Castaic Lake (Chumash: ''Kaštiq'') 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 California Office of Enviro ...
, while
Castaic Dam 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. T ...
is located at the southern end.
Land subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
has occurred along the aqueduct and has had a steady increase since its relatively stable state post construction of the aqueduct.


The aqueduct system

The aqueduct serves 35 million people and 5.7 million acres of farmland, 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 to the
O'Neill Forebay O'Neill Forebay is a forebay to the San Luis Reservoir created by the construction of O'Neill Dam across San Luis Creek approximately west of Los Banos, California, United States, on the eastern slopes of the Pacific Coast Ranges of Merced Co ...
at the
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 west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its north ...
. From the O'Neill Forebay, it flows approximately to the
Dos Amigos Pumping Plant The Dos Amigos Pumping Plant is a water pumping plant, constructed between 1963 and 1966 as part of the California State Water Project. It is able to withhold and transport water between Northern and Southern California through an approximately ...
. After Dos Amigos, the aqueduct flows about to where the
Coastal Branch 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. Named after Califo ...
splits from the "main line". The split is approximately south-southeast of
Kettleman City Kettleman City is a census-designated place (CDP) in Kings County, California, United States. Kettleman City is located southwest of Hanford, 54 miles (88 km) south of Fresno, at an elevation of , and sits only about 1/2 mile north of the 36th p ...
. After the coastal branch, the line continues by gravity another to the Buena Vista Pumping Plant. From the Buena Vista, it flows approximately to the Teerink Pumping Plant. After Teerink it flows about to the Chrisman Pumping Plant. Chrisman is the last pumping plant before
Edmonston Pumping Plant Edmonston Pumping Plant is a pumping station near the south end of the California Aqueduct, which is the principal feature of the California State Water Project. It lifts water 1,926 feet (600 m) to cross the Tehachapi Mountains where it split ...
, which is from Chrisman. South of the plant the west branch splits off in a southwesterly direction to serve the
Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east-west trending chains of mountai ...
. At Edmonston Pumping Plant it is pumped over the
Tehachapi Mountains The Tehachapi Mountains (; Kawaiisu: ''Tihachipia'', meaning "hard climb") are a mountain range in the Transverse Ranges system of California in the Western United States. The range extends for approximately in southern Kern County and northwest ...
. 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 California Oregon Intertie (COI), identified as Path 66 by Western Electricity Coordinating Council (WECC), is a corridor of three roughly parallel 500 kV alternating current power lines connecting the electric grids of Oregon and California. Th ...
or
Path 15 Path 15 is an portion of the north–south power transmission corridor in California, U.S. It forms a part of the Pacific AC Intertie and the California-Oregon Transmission Project. Path 15 is part of The Western Electricity Coordinating Cou ...
. 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 In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potentia ...
is recaptured by
hydroelectric Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...
plants. The initial pumping station fed by the Sacramento River Delta raises the water , while a series of pumps culminating at the Edmonston Pumping Plant raises the water over the Tehachapi Mountains. The Edmonston Pumping station requires so much power that several
power lines Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines that facilitate this movement form a ''transmission network''. This is d ...
off of Path 15 and
Path 26 Path 26 is a set of three Southern California Edison (SCE) 500 kV power lines, located primarily in Los Angeles County, and extending into Kern and Ventura counties, all in California. Path 26 is part of the Western Electricity Coordinating Coun ...
are needed to ensure proper operation of the pumps. A typical section has a
concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
-lined channel at the base and an average water depth of about . The widest section of the aqueduct is and the deepest is . Channel capacity is and the largest pumping plant capacity at Dos Amigos is . A 2021 study published in ''
Nature Sustainability ''Nature Sustainability'' is a monthly peer-reviewed scientific journal published by Nature Portfolio. It was established in 2018. The editor-in-chief is Monica Contestabile. Abstracting and indexing The journal is abstracted and indexed in: ...
'' estimated that the installation of
solar panels A solar cell panel, solar electric panel, photo-voltaic (PV) module, PV panel or solar panel is an assembly of photovoltaic solar cells mounted in a (usually rectangular) frame, and a neatly organised collection of PV panels is called a phot ...
over the canal could potentially reduce annual water
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
by of canal. While electricity generated by the solar panels could be used by the aqueduct's pumping systems, the study also considered the possibility of supplying power to irrigation systems in the Central Valley to reduce reliance on diesel-powered irrigation pumps. Similar canal-spanning solar installations have been demonstrated in India, including a steel truss design in
Gujarat Gujarat (, ) is a state along the western coast of India. Its coastline of about is the longest in the country, most of which lies on the Kathiawar peninsula. Gujarat is the fifth-largest Indian state by area, covering some ; and the ninth ...
and a suspension cable design
Punjab Punjab (; Punjabi: پنجاب ; ਪੰਜਾਬ ; ; also romanised as ''Panjāb'' or ''Panj-Āb'') is a geopolitical, cultural, and historical region in South Asia, specifically in the northern part of the Indian subcontinent, comprising ...
.


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 The Tehachapi Mountains (; Kawaiisu: ''Tihachipia'', meaning "hard climb") are a mountain range in the Transverse Ranges system of California in the Western United States. The range extends for approximately in southern Kern County and northwest ...
.


Coastal Branch

The Coastal Branch splits from the main line south-southeast of
Kettleman City Kettleman City is a census-designated place (CDP) in Kings County, California, United States. Kettleman City is located southwest of Hanford, 54 miles (88 km) south of Fresno, at an elevation of , and sits only about 1/2 mile north of the 36th p ...
transiting Kings County,
Kern County Kern County is a county located in the U.S. state of California. As of the 2020 census, the population was 909,235. Its county seat is Bakersfield. Kern County comprises the Bakersfield, California, Metropolitan statistical area. The county sp ...
,
San Luis Obispo County San Luis Obispo County (), officially the County of San Luis Obispo, is a county on the Central Coast of California. As of the 2020 census, the population was 282,424. The county seat is San Luis Obispo. Junípero Serra founded the Miss ...
, and
Santa Barbara County Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barba ...
to deliver water to the coastal cities of
San Luis Obispo San Luis Obispo (; Spanish for " St. Louis the Bishop", ; Chumash: ''tiłhini'') is a city and county seat of San Luis Obispo County, in the U.S. state of California. Located on the Central Coast of California, San Luis Obispo is roughly hal ...
, Santa Maria, and Santa Barbara. The Coastal Branch is and has five pump stations. Phase I, an above-ground aqueduct totaling from where it branches from the California Aqueduct, was completed in 1968. With construction beginning in 1994, Phase II consists of of a diameter buried pipeline extending from the Devils Den Pump Plant, and terminates at Tank 5 on
Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USS General Harry Taylor (AP-145), USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in K ...
in
Santa Barbara County Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barba ...
. The Central Coast Water Authority (CCWA) extension, completed in 1997, is a (30–39 in) (76–99 cm) diameter pipeline that travels from Vandenberg through
Vandenberg Village Vandenberg Village is a census-designated place (CDP) in the unincorporated area of Santa Barbara County, California, United States. The population was 6,497 at the 2010 census, up from 5,802 at the 2000 census. It is a community situated in the ...
,
Lompoc Lompoc ( ; Chumash: ''Lum Poc'') is a city in Santa Barbara County, California. Located on the Central Coast, Lompoc has a population of 43,834 as of July 2021. Lompoc has been inhabited for thousands of years by the Chumash people, who called ...
, Buellton, and Solvang where it terminates at
Lake Cachuma Cachuma Lake is a reservoir in the Santa Ynez Valley of central Santa Barbara County, California on the Santa Ynez River adjoining the north side of California State Route 154. The artificial lake was created by the construction of Bradbury Dam, ...
in
Los Padres National Forest Los Padres National Forest is a United States national forest in Southern California, southern and central California. Administered by the United States Forest Service, Los Padres includes most of the mountainous land along the California coast ...
. Coastal Branch facilities include: * Las Perillas Pumping Plant * Badger Hill Pumping Plant * Devil's Den Pumping Plant * Bluestone Pumping Plant * Polonio Pass Pumping Plant * Polonio Pass Water Treatment Plant * Cuesta Tunnel * Santa Ynez Pumping Facility


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 Lake Palmdale is an artificial lake completed in 1924 along with the nearby Little Rock Reservoir created by Little Rock Dam. Its source of water is the California State Water Project and it is fed by the California Aqueduct. It is located in t ...
and terminates at
Lake Perris Lake Perris is an artificial lake completed in 1973. It is the southern terminus of the California State Water Project, situated in a mountain-rimmed valley between Moreno Valley and Perris, in what is now the Lake Perris State Recreation Area. ...
, in the area of the
San Gorgonio Pass The San Gorgonio Pass, or Banning Pass, is a elevation gap on the rim of the Great Basin between the San Bernardino Mountains to the north and the San Jacinto Mountains to the south. The pass was formed by the San Andreas Fault, a major trans ...
. It passes through parts of Kern, Los Angeles, San Bernardino, and Riverside counties. East Branch facilities include: * Tehachapi East Afterbay * Alamo Power Plant * Pearblossom Pumping Plant * Mojave Siphon * Mojave Siphon Power Plant * Cedar Springs Dam * Silverwood Lake * San Bernardino Intake Structure * San Bernardino Tunnel * Devil Canyon Power Plant * Devil Canyon Afterbay 1 and Afterbay 2 * Greenspot Pump Station (Backup) * Citrus Reservoir * Citrus Pump Station * Crafton Hills Reservoir * Crafton Hills Pump Station * Cherry Valley Pump Station * Perris Lake and Dam


West Branch

The West Branch continues to head towards its terminus at Pyramid Lake and
Castaic Lake Castaic Lake (Chumash: ''Kaštiq'') 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 California Office of Enviro ...
in the
Angeles National Forest The Angeles National Forest (ANF) of the United States Forest Service, U.S. Forest Service is located in the San Gabriel Mountains and Sierra Pelona Mountains, primarily within Los Angeles County, California, Los Angeles County in southern Calif ...
to supply the western Los Angeles basin. It passes through parts of Kern and Los Angeles counties. West Branch facilities include * Oso Pumping Plant * Peace Valley Pipeline * Warne Powerplant * Angeles Tunnel * Castaic Power Plant


Bikeway

When it was open, the California Aqueduct Bikeway was the longest of the paved paths in the
Los Angeles area Greater Los Angeles is the second-largest metropolitan region in the United States with a population of 18.5 million in 2021, encompassing five counties in Southern California extending from Ventura County in the west to San Bernardino Cou ...
, at long from Quail Lake near Gorman in the
Sierra Pelona Mountains The Sierra Pelona, also known as the Sierra Pelona Ridge or the Sierra Pelona Mountains, is a mountain ridge in the Transverse Ranges in Southern California. Located in northwest Los Angeles County, the ridge is bordered on the north by the San An ...
through the desert to
Silverwood Lake Silverwood Lake is a large reservoir in San Bernardino County, California, United States, located on the West Fork Mojave River, a tributary of the Mojave River in the San Bernardino Mountains. It was created in 1971 as part of the State Water Pr ...
in the
San Bernardino Mountains The San Bernardino Mountains are a high and rugged mountain range in Southern California in the United States. Situated north and northeast of San Bernardino and spanning two California counties, the range tops out at at San Gorgonio Mountain ...
. 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 The September 11 attacks, commonly known as 9/11, were four coordinated suicide terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001. That morning, nineteen terrorists hijacked four commercial ...
.


Pumping stations

; Phase I, canal * Las Perillas Pumping Plant , Kings County * Badger Hill Pumping Plant , Kings County ; Phase II, pipeline and tunnel * Devil's Den Pumping Plant , Kern County * Bluestone Pumping Plant , Kern County * Polonio Pass Pumping Plant , San Luis Obispo County


Hydrography

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 The Sacramento River ( es, Río Sacramento) is the principal river of Northern California in the United States and is the largest river in California. Rising in the Klamath Mountains, the river flows south for before reaching the Sacramento–S ...
, along with its tributaries the
Feather River The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about long. Its length to its most distant headwater tributary is just over . The main stem Feather R ...
and
American River , name_etymology = , image = American River CA.jpg , image_size = 300 , image_caption = The American River at Folsom , map = Americanrivermap.png , map_size = 300 , map_caption ...
, flows southwards through the Sacramento Valley for about . In the San Joaquin Valley, the
San Joaquin River The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching Suis ...
flows roughly northwest for , picking up tributaries such as the
Merced River The Merced River (), in the central part of the U.S. state of California, is a -long tributary of the San Joaquin River flowing from the Sierra Nevada (U.S.), Sierra Nevada into the San Joaquin Valley. It is most well known for its swift and st ...
,
Tuolumne River The Tuolumne River (Yokutsan: ''Tawalimnu'') flows for through Central California, from the high Sierra Nevada to join the San Joaquin River in the Central Valley. Originating at over above sea level in Yosemite National Park, the Tuolumne ...
,
Stanislaus River The Stanislaus River is a tributary of the San Joaquin River in north-central California in the United States. The main stem of the river is long, and measured to its furthest headwaters it is about long. Originating as three forks in the high ...
and
Mokelumne River The Mokelumne River ( or ; ''Mokelumne'', Miwok for "People of the Fish Net") is a -long river in northern California in the United States. The river flows west from a rugged portion of the central Sierra Nevada (U.S.), Sierra Nevada into the Ce ...
. In the south part of the San Joaquin Valley, the
alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...
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 ''Schoenoplectus acutus'' ( syn. ''Scirpus acutus, Schoenoplectus lacustris, Scirpus lacustris'' subsp. ''acutus''), called tule , common tule, hardstem tule, tule rush, hardstem bulrush, or viscid bulrush, is a giant species of sedge in the pl ...
and
Kern KERN (1180 AM broadcasting, AM) is a commercial radio, commercial radio station city of license, licensed to Wasco, California, Wasco-Greenacres, California, and serving the Bakersfield metropolitan area. The station is owned by American General ...
. This basin, usually
endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...
, formerly filled during heavy snowmelt and spilled out into the San Joaquin River. Called
Tulare Lake Tulare Lake () ( Spanish: ''Laguna de Tache'', Yokuts: ''Pah-áh-su'') is a freshwater dry lake with residual wetlands and marshes in the southern San Joaquin Valley, California, United States. After Lake Cahuilla disappeared in the 17th century ...
, it is usually dry nowadays because the rivers feeding it have been diverted for agricultural purposes. 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 The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
after passing through
Suisun Bay Suisun Bay ( ; Wintun for "where the west wind blows") is a shallow tidal estuary (a northeastern extension of the San Francisco Bay) in Northern California. It lies at the confluence of the Sacramento River and San Joaquin River, forming the ent ...
,
San Pablo Bay San Pablo Bay is a tidal estuary that forms the northern extension of San Francisco Bay in the East Bay and North Bay regions of the San Francisco Bay Area in northern California. Most of the Bay is shallow; however, there is a deep water c ...
, upper
San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...
and finally the
Golden Gate The Golden Gate is a strait on the west coast of North America that connects San Francisco Bay to the Pacific Ocean. It is defined by the headlands of the San Francisco Peninsula and the Marin Peninsula, and, since 1937, has been spanned by th ...
. 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. The Sacramento River carries far more water than the San Joaquin, with an estimated of virgin annual runoff, as compared to the San Joaquin's approximately . Intensive agricultural and municipal water consumption has reduced the present rate of outflow to about for the Sacramento and 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.


Land subsidence


Background

Land subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
is when the land gradually or suddenly sinks or settles due to movement or removal of natural materials such as water, minerals, oil and natural gases. More often than not, subsidence occurs when groundwater is removed from sediment or rocks in a large quanity. This often occurs due to human interference, but can also happen from natural phenomenons. Subsidence can happen over very large areas or small little sections of land. This has occurred along the California Aqueduct of the State Water Project since construction. Human causes include; pumping, mining and fracking. Natural causes include; earthquakes, erosion, glacial movement, soil compaction and the formation of sinkholes. Groundwater use and pumping in the area was the major water use for farmers and agriculture in the 1920s, and over time, this over-pumping resulted in land subsidence and a decline in groundwater-level resources. In time, this resulted in major land subsidence by the 1970's with local areas having 1 to 28 feet of subsidence. With the creation and use of the California Aqueduct along these regions, surface water being transported put a halt on significant compaction and a recovery in ground water levels now with less ground water pumping. The aqueduct has been increasing in subsidence rates rapidly, even though it was relatively stable for many years after being constructed. The Tulare Basin is subsiding at a rate of about one foot per year, as measured by NASA's GRACE satellite.


Measurement

Measurement of this subsidence is done in a few ways. Originally, subsidence was recorded based on land surveying, repeating the surveying, and along with monitoring compaction by recording the data from extensometers at multiple sites. Since then, Global Positioning Systems (GPS) has been used along with land surveying to record subsidence and compaction. More recently, interferometric synthetic aperture radar (InSAR) has been used to monitor subsidence along with GPS. InSAR is being used to recreate maps to closely watch the progression of the land around the aqueduct.


Consequences

Subsidence can put land, both private and public, at risk of infrastructure damage. Bridges, levees, roads, and groundwater wells are either at risk of damage or have been damaged already. With subsidence progression, underground aquifers could be at risk and water storage from them could be threatened. Damage and sinking of the canal of the aqueduct has already occurred from subsidence which has made the canal less reliable. Capacity has been compromised due to damage to the canals and therefore has caused problems and delays with delivering the water across the state, as well as higher rates and costs for power and operation.


In popular culture

A documentary about the decline of the United States' infrastructure, ''The Crumbling of America'', was commissioned by the U.S.
A&E network A&E is an American basic cable network, the flagship television property of A&E Networks. The network was originally founded in 1984 as the Arts & Entertainment Network, initially focusing on fine arts, documentaries, television drama, dramas, and ...
in the late 2000s. The documentary is typically shown on the
History History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the History of writing#Inventions of writing, invention of writing systems is considered prehistory. "History" is an umbr ...
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 ''California's Gold'' is a public television human interest program that explores the natural, cultural, and historical features of California. The series ran for 24 seasons beginning in 1991, and was produced and hosted by Huell Howser in colla ...
'' with
Huell Howser Huell Burnley Howser (October 18, 1945 – January 7, 2013) was an American television personality, actor, producer, writer, singer, and voice artist, best known for hosting, producing, and writing ''California's Gold'' and his human interest sh ...
.


See also

*
Colorado River Aqueduct The Colorado River Aqueduct, or CRA, is a water conveyance in Southern California in the United States, operated by the Metropolitan Water District of Southern California (MWD). The aqueduct impounds water from the Colorado River at Lake Hav ...
*
Los Angeles Aqueduct The Los Angeles Aqueduct system, comprising the Los Angeles Aqueduct (Owens Valley aqueduct) and the Second Los Angeles Aqueduct, is a water conveyance system, built and operated by the Los Angeles Department of Water and Power. The Owens Valley ...


References


External links


The California Department of Water Resources website

Historic Pump-Storage Operation in WSCC
* USGS
Geographic Names Information System The Geographic Names Information System (GNIS) is a database of name and locative information about more than two million physical and cultural features throughout the United States and its territories, Antarctica, and the associated states of ...
data ** ** ** ** {{State Water Project Aqueducts in California California State Water Project Interbasin transfer Central Valley (California) Southern California Transportation buildings and structures in California Water in California