New Melones Dam

New Melones Dam is an earth and rock filled embankment dam on the Stanislaus River, about 5 mi (8.0 km) west of Jamestown, California in the United States. The water impounded by the 625-foot (191 m)-tall dam forms New Melones Lake, California's fourth largest reservoir, in the foothills of the Sierra Nevada east of the San Joaquin Valley. The dam serves mainly for irrigation water supply, and also provides hydropower generation, flood control and recreation benefits.

New Melones was authorized in 1944 as a unit of the Central Valley Project, a system designed to provide irrigation water to the fertile agricultural region of the Central Valley. The dam would be built by the U.S. Army Corps of Engineers (USACE), and transferred to the U.S. Bureau of Reclamation (USBR) upon completion. In 1966, work began to clear the foundations for a high dam that would replace an earlier structure built by two irrigation districts. Construction of the main embankment began in 1976, and was topped out in late 1978. Water storage in New Melones Lake commenced in 1978, and the dam's hydroelectric station produced its first power in mid-1979.

The dam was the focus of a long environmental controversy and was one of the last large dams built in California. Critics protested the flooding of a long scenic stretch of the Stanislaus River, which flowed over whitewater rapids through the deepest limestone canyon in the western United States. The protestors employed a variety of methods, some extreme, to prevent the filling of New Melones Lake until 1983, when record-setting floods filled the reservoir and overflowed the dam's emergency spillway. Because of the controversy in addition to lower-than-expected water yields from the new dam, the USBR has called it "a case study of all that can go wrong with a project."