High Quality Content by WIKIPEDIA articles! 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.