page_title: New Melones Dam
section_title: Background
hierarchical_section_title: New Melones Dam / History / Background
caption_attribution_description: English: Map of the Stanislaus River in Central California, USA. Shaded relief from US Geological Survey data.
context_page_description: New Melones Dam is an earth and rock filled embankment dam on the Stanislaus River, about 5 miles west of Jamestown, California, United States, on the border of Calaveras County and Tuolumne County. The water impounded by the 625-foot-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.
  The dam was authorized in 1944 as a unit of the federal Central Valley Project, a system designed to provide irrigation water to the fertile agricultural region of the Central Valley. It would be built by the U.S. Army Corps of Engineers, and transferred to the U.S. Bureau of Reclamation upon completion. In 1966, work began to clear the foundations for a high dam that would replace an earlier, much smaller structure built by two irrigation districts. Construction of the main embankment began in 1976, and was topped out in late 1978. The filling of New Melones Lake commenced in 1978, and the dam's hydroelectric station produced its first power in mid-1979.
context_section_description: The modern development of the Stanislaus River began with the Oakdale and South San Joaquin Irrigation Districts, which were created in 1909 under the Wright Act to serve farmers in the area. Early irrigation along the Stanislaus River was dependent on the natural flow of the river, which was never enough to water crops during the late summer and fall. In 1926 the two irrigation districts jointly completed the original Melones Dam, a 211-foot (64 m) high concrete arch dam with a storage capacity of 112,500 acre feet (138,800,000 m³). This reservoir was still not big enough for all the demands placed on it, especially during the long droughts of the 1930s.
  The storage capacity of these early reservoirs was limited and the irrigation districts sought to increase the size of the Melones Reservoir. The federal Flood Control Act of 1944 authorized the U.S. Army Corps of Engineers to build a 355-foot (108 m) arch dam with a capacity of 450,000 acre⋅ft (560,000 dam³). As a primary flood control structure, it would protect 35,000 acres (14,000 ha) of farmland as well as the towns of Oakdale, Riverbank and Ripon from flooding. It would generate electricity using the original 22 megawatt Melones hydroelectric plant. However, the cost-benefit analysis conducted for the project, then known as "New Melones I", did not justify the construction of the dam for flood control alone. If other benefits such as irrigation, fishery conservation and recreation were included, the cost-benefit ratio became positive. The Corps downplayed these additional benefits, intending to keep it primarily as a flood-control structure, because an irrigation project would then fall under the authority of the U.S. Bureau of Reclamation.
  During the 1950s the irrigation districts built two more dams, Donnells and Beardsley, along the upper Stanislaus River, forming (along with Tulloch Dam below Melones Dam) the Tri-Dam Project. The Corps objected to the Tri-Dam Project because the additional storage provided by these smaller dams further decreased the potential flood control benefit of New Melones. With the Corps unable to provide a sound economic justification, New Melones I was ultimately shelved in 1954. Meanwhile, the Oakdale and South San Joaquin irrigation districts had conducted their own study in the late 1940s and proposed a bigger dam, 460 feet (140 m) tall with a capacity of 1.1 million acre feet (1.4 km³), or approximately one year's worth of Stanislaus River runoff.
  The Bureau of Reclamation first surveyed the Melones dam site in the 1950s, and initially supported the proposed 1.1 million acre foot reservoir but soon increased the size of the project (to be known as "New Melones II") twofold, as part of the Central Valley Project. The Bureau cited numerous benefits to a larger reservoir, which it estimated would capture 335,000 acre feet (0.413 km³) of extra water per year to increase irrigation, supply other units of the Central Valley Project, and maintain a minimum flow in the Stanislaus River to protect fish (before New Melones was built, diversions often dried the river completely in summer). This water would be provided above and beyond fulfilling previously existing water rights to the irrigation districts.
  Although the 1944 version of the project had been abandoned, the Bureau and the Corps continued to argue over who would construct the dam. The Flood Control Act of 1962 authorized the final design of the dam – changing it from an arch to an embankment dam, increasing the size of the projected reservoir to 2,400,000 acre⋅ft (3,000,000 dam³) and requiring the construction of a new power plant. It also settled the interagency dispute by authorizing the Corps to construct the dam and direct flood control operations, and the Bureau to operate the dam for its other intended purposes such as irrigation and hydroelectricity.
  In the early 1960s, there was some local opposition to the project on the grounds that it was too big – with a reservoir more than twice as large as the annual flow of the Stanislaus River, it might never fill and would be a w
caption: Map of the Stanislaus River watershed, showing today's major dams and reservoirs.
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