New Melones Dam

New Melones Dam

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New Melones Dam is an earth and rock filled dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 across the Stanislaus River
Stanislaus River
The Stanislaus River in California is one of the largest tributaries of the San Joaquin River. The river is long and has north, middle and south forks...

 creating New Melones Lake
New Melones Lake
New Melones Lake is an artificial lake in the central Sierra Nevada foothills of Calaveras- and Tuolumne County, California near Jamestown. This reservoir created by the construction of the New Melones Dam across the Stanislaus River has a capacity with a surface area of...

. Situated between Calaveras
Calaveras County, California
Calaveras County is a county located in the Gold Country of the U.S. state of California. Calaveras is the Spanish word for skulls; the county was reportedly named for the remains of Native Americans discovered by the Spanish explorer Captain Gabriel Moraga. As of the 2010 census, the county had a...

 and Tuolumne County, California
Tuolumne County, California
Tuolumne County is a county in the Sierra Nevada of the U.S. state of California. The northern half of Yosemite National Park is located in the eastern part of the county. As of the 2010 census, the population was 55,365, up from 54,501 at the 2000 census...

 in the Sierra Nevada foothills near Jamestown
Jamestown, California
Jamestown is a census-designated place in Tuolumne County, California, United States. The population was 3,433 at the 2010 census, up from 3,017 at the 2000 census.A scene from the movie Hidalgo was filmed in Jamestown...

, the dam was completed in 1979 replacing the old Melones Dam.


The dam was constructed to replace the 183 ft (56 m) tall Melones Dam, an arch dam
Arch dam
An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 which was constructed in 1926 by the Oakdale and South San Joaquin Irrigation Districts. The new dam was authorized by the Flood Control Act of 1944
Flood Control Act of 1944
The Pick-Sloan Flood Control Act of 1944 , enacted in the 2nd session of the 78th Congress, is U.S. legislation that authorized the construction of numerous dams and modifications to previously existing dams, as well as levees across the United States...

 and reauthorized by the Flood Control Act of 1966 with an increase in height from a 355 ft (108 m) arch dam to 625 ft (191 m) tall embankment dam. Construction on the New Melones Dam began in July 1966 and the diversion tunnel was complete by 1973. On March 6, 1974, construction on the dam began and it was completed on October 28, 1978. By the end of 1978, the power plant was complete and it was commissioned in 1979. The filling of the reservoir began in 1983.

The United States Bureau of Reclamation
United States Bureau of Reclamation
The United States Bureau of Reclamation , and formerly the United States Reclamation Service , is an agency under the U.S...

 operates the dam. New Melones Dam's primary purpose is to provide water for irrigation. It is a 625 ft (190.5 m) high earth and rock-filled structure creating a 2400000 acre.ft reservoir.

The dam has a hydroelectric plant with a capacity of 300 MW. It has three vertical Francis turbines
Francis turbine
The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....

 and a head of 460 ft (140.2 m). The plant has a low capacity factor and operates as a peaking facility, which means that it operates mostly during times of peak electricity demand.


The dam was one of the last built in California, as the environmental movement
Environmental movement
The environmental movement, a term that includes the conservation and green politics, is a diverse scientific, social, and political movement for addressing environmental issues....

 gained support, and as such was fiercely opposed by groups such as the Sierra Club
Sierra Club
The Sierra Club is the oldest, largest, and most influential grassroots environmental organization in the United States. It was founded on May 28, 1892, in San Francisco, California, by the conservationist and preservationist John Muir, who became its first president...

, as well as many individuals who saw the canyon of the Stanislaus River
Stanislaus River
The Stanislaus River in California is one of the largest tributaries of the San Joaquin River. The river is long and has north, middle and south forks...

 as having value far beyond a reservoir. On May 20, 1979, Mark Dubois hiked into the dam site and chained himself to a boulder in the dam's floodpath, intending to block the U.S. Army Corps of Engineers from filling New Melones Lake. His protest action succeeded in temporarily securing a reprieve for the Class III whitewater rapids above the Parrott's Ferry Bridge. However, in 1983 due to a severe El Niño event and subsequent flood, the reservoir was finally allowed to reach full design capacity.

Several cave-dwelling species that were threatened by the construction were transplanted to an abandoned mine, among them Banksula melones
Banksula melones
Banksula melones is a species of harvestman in family Phalangodidae. It is endemic to caves along the Stanislaus River of California, USA....

, the Melones cave harvestman.

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