San Luis Dam is a major earth-filled dam in
Merced County
Merced County ( ), is a county located in the northern San Joaquin Valley section of the Central Valley, in the U.S. state of California.
As of the 2020 census, the population was 281,202. The county seat is Merced. The county is named after ...
,
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
, 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 nort ...
, the largest
off-stream reservoir
{{Unreferenced, date=December 2009
An off-stream reservoir is a reservoir that is not located on a streambed, and is supplied by a pipeline, aqueduct or an adjacent stream. San Luis Reservoir is the largest off-stream reservoir in the United S ...
in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
. The dam and reservoir are located in the
Diablo Range
The Diablo Range is a mountain range in the California Coast Ranges subdivision of the Pacific Coast Ranges in northern California, United States. It stretches from the eastern San Francisco Bay area at its northern end to the Salinas Valley ...
to the east of
Pacheco Pass
Pacheco Pass, elevation , is a low mountain pass located in the Diablo Range in southeastern Santa Clara County, California. It is the main route through the hills separating the Santa Clara Valley and the Central Valley.
As with most passes in ...
and about west of
Los Banos. San Luis Dam, a jointly-owned state and federal facility, stores more than 2 million acre feet (2.5 km
3) of water for 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 ...
and the federal
Central Valley Project
The Central Valley Project (CVP) is a federal power and water management project in the U.S. state of California under the supervision of the United States Bureau of Reclamation (USBR). It was devised in 1933 in order to provide irrigation an ...
. 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.
San Luis provides water mainly for
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...
in the
San Joaquin Valley
The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven ...
, where it augments the supply for more than 1 million acres (400,000 ha) of agricultural land, although some water is also used for urban and environmental uses. The dam was built between 1963 and 1968, and filled for the first time in 1969. It provides flexibility to the state water system by capturing, via pumps and canals, the wet season (November–April) runoff that would otherwise flow from 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 Sa ...
into 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 conti ...
. It also generates
hydroelectricity
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 an ...
by releasing the water when it is needed. However, it has indirectly impacted the environment by enabling increased water diversion from sensitive estuary regions. In recent years, a combination of drought and pumping restrictions enacted to protect endangered fish have contributed to low water levels at the San Luis Reservoir.
The dam and reservoir are visible from the Romero Overlook Visitors Center, which is located along Highway 152.
Overview
San Luis Reservoir is designed to capture excess runoff flowing out 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 Sa ...
, the largest watershed of California, during the winter and spring rainy season so it can be used during the dry season. This water includes both natural river flows, and water that is evacuated from
Shasta Lake
Shasta Lake, also popularly known as Lake Shasta, is a reservoir in Shasta County, California, United States. It began to store water in 1944 due to the impounding of the Sacramento River by Shasta Dam, the ninth tallest dam in the United State ...
,
Lake Oroville
Lake Oroville is a reservoir formed by the Oroville Dam impounding the Feather River, located in Butte County, northern California. The lake is situated northeast of the city of Oroville, within the Lake Oroville State Recreation Area, in th ...
,
Folsom Lake
Folsom Lake is a reservoir on the American River in the Sierra Nevada foothills of California, United States.
It is located within Placer, El Dorado, and Sacramento Counties. It is about northeast of Sacramento. The lake surface area is , it ...
and other reservoirs for flood control purposes. This is accomplished via a system of canals and pumping stations which divert water from the Delta and deliver it south to water users.
The San Luis Dam, a zoned compacted earthfill structure, is one of the largest embankment dams in the United States, with a structural height of , a length of and a structural volume of .
When full, San Luis Reservoir is more than deep, covers , and contains of water. The storage capacity of San Luis Reservoir is divided with 55 percent belonging to the state and 45 percent to the federal government.
The
Delta-Mendota Canal, originally built in 1951, carries irrigation water for the federal Central Valley Project (CVP) operated by the
U.S. Bureau of Reclamation to supply
San Joaquin Valley
The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven ...
farms. The
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. Named after Califo ...
was built in 1968 as part of the State Water Project (SWP), to deliver water to
Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
and other cities and farmlands in Southern California. Both canals begin at the
Clifton Court Forebay near
Tracy, California
Tracy is the second most populated city in San Joaquin County, California, United States. The population was 93,000 at the 2020 census. Tracy is located inside a geographic triangle formed by Interstate 205 on the north side of the city, Inters ...
where the
Jones
Jones may refer to:
People
*Jones (surname), a common Welsh and English surname
*List of people with surname Jones
* Jones (singer), a British singer-songwriter
Arts and entertainment
* Jones (''Animal Farm''), a human character in George Orwell ...
and
Banks Pumping Plants draw water from the Delta in order to deliver it south. The canals are linked to
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 ...
, a small reservoir located directly in front of San Luis Dam where the water is temporarily stored for distribution. Most CVP project water is dedicated to irrigation while the SWP water supply is split, with 30 percent going to agriculture and 70 percent to urban areas.
The San Luis Pumping-Generating Plant (also known as the William R. Gianelli Power Plant) is situated between O'Neill and San Luis Reservoirs and can pump water uphill for storage in San Luis during period of low demand, and release it during periods of high demand. The plant has eight reversible
Francis turbine units which can generate up to 424
megawatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
s when releasing water. The power consumption while pumping is 376 megawatts. The maximum water flow while generating is , and maximum pumping is .
The sale of
peaking power
Peaking power plants, also known as peaker plants, and occasionally just "peakers", are power plants that generally run only when there is a high demand, known as peak demand, for electricity. Because they supply power only occasionally, the powe ...
lowers the overall cost of operating the State Water Project, particularly the giant electric pumps along the California Aqueduct. A short 230
kV power line
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...
heads eastward to deliver this electricity to
Northern California's electricity backbone,
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 ...
. However, due to friction losses when pumping water uphill, only about 70 percent of the energy can be recouped when the water is discharged.
History
The valley filled by the San Luis Reservoir was originally inhabited by the
Yokuts
The Yokuts (previously known as MariposasPowell, 1891:90–91.) are an ethnic group of Native Americans native to central California. Before European contact, the Yokuts consisted of up to 60 tribes speaking several related languages. ''Yokuts ...
people; during the early 19th century it was part of
Rancho San Luis Gonzaga
Rancho San Luis Gonzaga was a Mexican land grant in the Diablo Range, in present-day Santa Clara County and Merced County, California given in 1843 by Governor Manuel Micheltorena to Juan Carlos Pacheco and José Maria Mejía. The grant was bo ...
and small-scale agriculture began in the area, supplied by groundwater and canals from 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 ...
. The Central Valley Project was begun in the 1930s to provide an additional water supply to the area and greatly expanded the irrigated acreage. However, the lack of local water storage limited the system's flexibility.
During the dry summer months when surface water was frequently unavailable, farmers pumped vast volumes of groundwater to irrigate their crops, considerably depleting the regional aquifer. The Bureau of Reclamation recognized the need for a large storage reservoir in order to provide a year-round water supply, and began studies for this project in 1955.
During the 1950s the State of California also began building its own water project, whose design also required an off-stream water storage reservoir. The state approached the federal government with an offer to design a joint-use facility; however it took several years for the Bureau of Reclamation to agree to the proposal. On May 16, 1960, the state and the Bureau of Reclamation signed a "coordinated operation" agreement which laid out plans for the construction of joint-use facilities, including the San Luis Dam and Power Plant.
The state government was to cover 55 percent of the cost with the federal government providing the rest. On June 3, 1960, President
Dwight D. Eisenhower
Dwight David "Ike" Eisenhower (born David Dwight Eisenhower; ; October 14, 1890 – March 28, 1969) was an American military officer and statesman who served as the 34th president of the United States from 1953 to 1961. During World War II, ...
signed an act authorizing the San Luis Unit Project.
Plans for the dam were completed by 1961 and the groundbreaking ceremony took place on August 18, 1962. In front of a crowd of 15,000 people, President
John F. Kennedy
John Fitzgerald Kennedy (May 29, 1917 – November 22, 1963), often referred to by his initials JFK and the nickname Jack, was an American politician who served as the 35th president of the United States from 1961 until his assassination ...
and California Governor
Pat Brown
Edmund Gerald "Pat" Brown (April 21, 1905 – February 16, 1996) was an American lawyer and politician who served as the 32nd governor of California from 1959 to 1967. His first elected office was as district attorney for San Francisco, and he w ...
gave the signal to detonate the first explosive charges in the San Luis dam site. Work began the same month to reroute Pacheco Pass Highway (today's
SR 152) around the future reservoir basin. The primary contract for the dam itself was awarded to
Morrison-Knudsen,
Utah Construction & Mining Co., and
Brown & Root
KBR, Inc. (formerly Kellogg Brown & Root) is a U.S. based company operating in fields of science, technology and engineering. KBR works in various markets including aerospace, defense, industrial and intelligence. After Halliburton acquired Dres ...
in 1963 for $85.9 million. Alfred M. Petrofsky held the role of chief engineer.
Construction of San Luis Dam lasted from 1963 to early 1968. The dam was constructed in several zones with quarried local earth and rock averaging as much as per day. The 100-ton Caterpillar dump trucks used during construction were, at the time, the largest in the US. The construction of the four water intake towers, each high, involved the first use of
tower crane
A crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It is mainly used for lifting heavy objects and transpor ...
s in the US.
The work force peaked at 2,304 in October 1965 and declined thereafter; in January 1968, with construction almost completed, the first water was delivered through the California Aqueduct to begin filling the giant reservoir. The dam was officially dedicated on April 20, 1968, by Secretary of the Interior
Stewart L. Udall. On May 31, 1969, the San Luis Reservoir filled for the first time.
In 1981, during low water conditions in San Luis Reservoir, a long segment of the upstream face of the dam partially collapsed, causing of material to fall into the reservoir. Since the reservoir was at a low level the dam was in no immediate danger of failure, however it could not be safely refilled until the damage was repaired. By August 1982, the area had been stabilized with of additional fill (known as a "buttressing berm"), at a cost of $6.1 million. In July 1984 another crack appeared in the dam, but it soon stabilized.
Water supply
Most of the water stored behind San Luis Dam is used for irrigation. The CVP share of the water is released down the Delta-Mendota Canal into the San Joaquin River, which provides water for of farmland in the central part of the San Joaquin Valley. Parts of the CVP and SWP water supply the
Westlands Water District of
Fresno
Fresno () is a major city in the San Joaquin Valley of California, United States. It is the county seat of Fresno County and the largest city in the greater Central Valley region. It covers about and had a population of 542,107 in 2020, maki ...
and
Kings Counties, which irrigates up to of land on the west side of the San Joaquin Valley. Prior to the construction of San Luis Dam and the joint use portion of the California Aqueduct (the San Luis Canal) this area depended entirely on groundwater. In 2016 the main crops grown here were almonds, tomatoes, pistachios and wheat. Most of the Westlands district consists of large corporate farms totaling hundreds if not thousands of acres.
The SWP also provides more than of water per year for farmers in Kern County.
San Luis Reservoir stores water for the
Metropolitan Water District of 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 cit ...
(MWD) which is one of the primary providers of water for the
Greater 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 Coun ...
. This water reaches Southern California via the East and West Branches of the California Aqueduct. It also provides water for the Central Coast cities like
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 ...
and
Santa Barbara via the Coastal Branch of the California Aqueduct. Local water agencies and irrigation districts are allowed to "bank" water in San Luis Reservoir for later use, by purchasing it during the rainy season at lower prices when it is not immediately needed. However, regulations only allow such carryover storage when San Luis is not full, since state and federal water takes priority. Once the reservoir fills, any carryover water that has not been used is effectively "lost", i.e. transferred to the CVP and SWP supplies.
In addition to supplying the main CVP and SWP canals, San Luis Reservoir also supplies water to the
Santa Clara Valley
The Santa Clara Valley is a geologic trough in Northern California that extends 90 miles (145 km) south–southeast from San Francisco to Hollister. The longitudinal valley is bordered on the west by the Santa Cruz Mountains and on the east ...
via the Pacheco Tunnel and Hollister Conduit, which travel under the Diablo Range. At the western end of the tunnel, the water is stored behind
San Justo Dam, an earthfill dam completed in 1986. These facilities are all part of the San Felipe Division of the Central Valley Project.
The San Luis & Delta-Mendota Water Authority represents the 29 federal water contractors served by the San Luis Unit, consisting of a combined service area in the San Joaquin and Santa Clara Valleys. The Authority operates the Federally owned portion of the San Luis Reservoir and water supply infrastructure.
Environmental issues
Before San Luis Dam was built, most of the pumping from the Delta occurred during the summer when there is high demand for irrigation. The construction of San Luis Dam enabled the additional capture of winter flows that would otherwise be lost to the sea. However, water pumping during certain times of the winter and early spring interfere with fish migration, notably the Sacramento River
chinook salmon
The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Pacific salmon in North America, as well as the largest in the genus '' Oncorhynchus''. Its common name is derived from the Chinookan peoples. Other ...
. The pumping changes the primary direction of water flow in the Delta from east–west to north–south, confusing the fish. As a result, certain environmental restrictions have been in place since the 1990s to limit pumping during the spring chinook run (March–April). This has led to frequent low water levels at San Luis Reservoir; in late summer 2016 it fell to 10 percent of capacity, the lowest since 1991.
These restrictions have been criticized by water agencies as too stringent, especially since California is in a long-term drought. During winter 2016 at least of water was allowed to drain from the Delta into the Pacific instead of being pumped into San Luis Reservoir. In December 2016, Congress passed a bill allowing increased water pumping during times when fish are not at high risk. This will generally allow more water to be stored at San Luis Reservoir. The bill will require daily monitoring of fish to ensure environmental laws are not violated, instead of relying on hard limits which may not match current conditions. California Senator
Dianne Feinstein
Dianne Goldman Berman Feinstein ( ; born Dianne Emiel Goldman; June 22, 1933) is an American politician who serves as the senior United States senator from California, a seat she has held since 1992. A member of the Democratic Party, she wa ...
remarked that "the goal... is to run California's water system based on good science, not intuition."
Proposed expansion
In 2013, the Bureau of Reclamation proposed raising the BF Sisk Dam by to create about of extra storage capacity. An expanded reservoir could store more water in wet years to compensate for less water being pumped in dry years due to environmental restrictions. The project would cost $360 million and would also involve seismic upgrades to protect the dam from earthquakes. The dam expansion is one of several major water projects that could be funded, in part, by a $2.7 billion bond measure approved by California voters in 2014.
See also
*
List of dams and reservoirs in California
*
List of largest reservoirs of California
This is a list of the largest reservoirs, or man-made lakes, in the U.S. state of California. All fifty-three reservoirs that contain over of water at maximum capacity are listed. This includes those formed by raising the level of natural lakes ...
*
List of power stations in California
This is a list of power stations in the U.S. state of California that are used for utility-scale electricity generation. This includes baseload, peaking, and energy storage power stations, but does not include large backup generators. , Calif ...
*
List of United States Bureau of Reclamation dams
*
California Water Fix and Eco Restore
*
Sites Reservoir
The Sites Reservoir is a proposed $5.2 billion offstream reservoir project west of Colusa in the Sacramento Valley of northern California, to be built by the California Department of Water Resources. The project would pump per year of the w ...
*
Water in California
California's interconnected water system serves over 30 million people and irrigates over of farmland. As the world's largest, most productive, and potentially most controversial water system, it manages over of water per year.
Water and wate ...
References
External links
Kennedy's Speech at the Dedication of San Luis Dam, August 18, 1962San Luis Reservoir daily water levels(California Department of Water Resources)
{{Authority control
Dams in California
California State Water Project
Central Valley Project
Hydroelectric power plants in California
Buildings and structures in Merced County, California
Pumped-storage hydroelectric power stations in the United States
Dams in the San Joaquin River basin
Dams completed in 1967
Energy infrastructure completed in 1967
Embankment dams
United States Bureau of Reclamation dams
Diablo Range