The Mokelumne Aqueduct is a water conveyance system in central

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, United States. The aqueduct is supplied by the

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 C ...

and provides water to 35 municipalities in the

East Bay The East Bay is the eastern region of the San Francisco Bay Area and includes cities along the eastern shores of San Francisco Bay and San Pablo Bay. The region has grown to include inland communities in Alameda and Contra Costa counties. Wi ...

in the

San Francisco Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...

. The aqueduct and the associated dams, pipelines, treatment plants and hydroelectric system are owned and operated by the East Bay Municipal Utility District (EBMUD) and provide over 90 percent of the water used by the agency. The aqueduct is the sole water supply for about 1.4 million people in the East Bay. Under present water rights agreements, EBMUD can withdraw up to 325 million gallons (1,230,000 m³) per day, or per year, from the Mokelumne River. In addition, up to 98 million gallons (371,000 m³) per day or per year can be supplied via a branch from the

Sacramento River The Sacramento River () 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–San Joaquin River D ...

. However, this supply is expected only to be used in the driest 35% of years.

History

In the early 20th century, due to a lack of reliable local water, Bay Area cities began to look to rivers in the

Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...

, about east, as a potential new source. Although the city of

San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

was already extending an aqueduct to the Tuolumne River, East Bay communities wanted to build an independent water system, fearing future "

hegemony Hegemony (, , ) is the political, economic, and military predominance of one State (polity), state over other states, either regional or global. In Ancient Greece (ca. 8th BC – AD 6th c.), hegemony denoted the politico-military dominance of ...

" of the water system by San Francisco. In 1923, the EBMUD was organized and in 1924 acquired water rights to the Mokelumne River, a major tributary in the

San Joaquin River The San Joaquin River ( ; ) 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 Suisun Bay, San Francis ...

system. On November 4, 1924, residents approved $39 million (equivalent to $ million in ) in bonds to finance the project. Construction began in 1926 and by 1929, the high, concrete arch Pardee Dam and the First Mokelumne Aqueduct, consisting of a single pipeline, were completed. The first deliveries to the Bay Area were made on June 23, 1929. At the time of completion, Pardee Dam was the tallest in the world (this record was surpassed one year later by Diablo Dam in Washington State). In 1949, a second pipeline was built and in 1963 the third pipeline was constructed, bringing the aqueduct to its present capacity. In 1964, the second major dam of the project, Camanche Dam, was completed below Pardee. In 1970, EBMUD signed a contract with the U.S. Bureau of Reclamation (USBR) for supplemental water from the Folsom South Canal, which draws water from the

American River The American River is a List of rivers of California, river in California that runs from the Sierra Nevada (U.S.), Sierra Nevada mountain range to its confluence with the Sacramento River in downtown Sacramento. Via the Sacramento River, it ...

near

Sacramento Sacramento ( or ; ; ) is the capital city of the U.S. state of California and the seat of Sacramento County. Located at the confluence of the Sacramento and American Rivers in Northern California's Sacramento Valley, Sacramento's 2020 p ...

. The USBR supply was delayed for nearly 40 years in part due to minimum flow requirements in the American River to protect

salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...

and

steelhead Steelhead, or occasionally steelhead trout, is the Fish migration#Classification, anadromous form of the coastal rainbow trout or Columbia River redband trout (''O. m. gairdneri'', also called redband steelhead). Steelhead are native to cold-wa ...

populations. The Folsom South Canal Connection (FSCC), which links the two waterways, was finally completed in 2009.

Specifications

The aqueduct begins at Pardee Reservoir, which is formed by Pardee Dam on the Mokelumne River. The reservoir has a capacity of , or about a 10-month supply. Camanche Reservoir, located directly below Pardee, has a storage capacity of – twice the size of Pardee – but is not directly linked to the aqueduct. However, Camanche allows for greater diversions into the aqueduct by storing winter floodwaters spilled from Pardee. During the dry season, water is released from Camanche in order to satisfy local water-rights holders, eliminating the need to draw water from Pardee. The aqueduct travels southwest for through the western foothills of the

and then west across the Central Valley along the Calaveras River before crossing the

Sacramento–San Joaquin River Delta The Sacramento–San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in Central California and Northern California Northern California (commonly shortened to NorCal) is a geocultural region that ...

. Near Lodi, the aqueduct is joined by an extension of the Folsom South Canal, which supplements the Mokelumne River supply. Once the water reaches the

Berkeley Hills The Berkeley Hills are a range of the Pacific Coast Ranges, and overlook the northeast side of the valley that encompasses San Francisco Bay. They were previously called the "Contra Costa Range/Hills" (from the original Spanish ''Sierra de la Co ...

above the East Bay, it is channeled into a complex distribution system consisting of six terminal reservoirs ( Briones, Chabot, Lafayette, San Pablo and Upper San Leandro) with a combined storage capacity of . The water is treated at the San Pablo, Sobrante and Upper San Leandro Treatment Plants before passing through the Claremont Tunnel, which emerges on the western side of the range between Berkeley and

Oakland Oakland is a city in the East Bay region of the San Francisco Bay Area in the U.S. state of California. It is the county seat and most populous city in Alameda County, with a population of 440,646 in 2020. A major West Coast port, Oakland is ...

. Water not immediately put into the municipal system is stored in the reservoirs for use in times of low delivery or drought. Most of the aqueduct consists of three separate buried steel pipelines, although there are also some aboveground segments. The pipelines, also known as Aqueducts No. 1, 2 and 3, have diameters of , and , respectively. Aside from the main facilities, the distribution system includes of pipes, 125 pump plants, and 168 local reservoirs/storage tanks.

Issues

The aqueduct is located in a seismically active zone and is considered vulnerable to earthquakes, especially the stretch where it crosses the Sacramento–San Joaquin Delta, where an earthquake or storm-induced

levee A levee ( or ), dike (American English), dyke (British English; see American and British English spelling differences#Miscellaneous spelling differences, spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural ...

failure could damage the pipelines or any of three major river crossings here. A large earthquake (100 year return period or more) could put the aqueduct out of service from 18 months to three years, depending on the extent of the damage. Levee failures in 1980 and 2004 (not caused by earthquakes) on Jones Tract have threatened the aqueduct. An aqueduct joint at the crossing of the Middle River also failed in 1992, nearly causing a washout of the levee. The aqueduct was shut down in time before an actual levee breach could occur. Because Pardee Reservoir is relatively small among California reservoirs, EBMUD has pursued to raise Pardee Dam to a height of . This would expand the reservoir surface by . The enlarged reservoir would cover , an increase of 62 percent, and the capacity would be about , a roughly 50 percent increase. It would allow for more water to be provided during the dry season that would otherwise have been spilled over the dam during the winter. This project would have flooded between of the Mokelumne River. Due to environmental concerns, the project was shelved in 2011.

References

{{reflist

External links

The Mokelumne Aqueduct
– Maven's Notebook Aqueducts in California East Bay Municipal Utility District Interbasin transfer Mokelumne River San Joaquin Valley Infrastructure completed in 1929 1929 establishments in California Buildings and structures in Amador County, California Buildings and structures in Calaveras County, California Transportation in Amador County, California Transportation in Calaveras County, California Transportation buildings and structures in Contra Costa County, California Transportation buildings and structures in San Joaquin County, California Transportation buildings and structures in Alameda County, California

History

Specifications

Issues

See also

References

External links