New Melones Dam
New Melones Dam is an earth and rock filled embankment dam on the Stanislaus River, about west of Jamestown, California, United States, on the border of Calaveras County and Tuolumne County. The water impounded by the 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 began in 1978, and the dam's hydroelectric station produced its first power in mid-1979.
New Melones was the focus of a long environmental battle during the 1970s and early 1980s; 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 nearly breached the dam's emergency spillway. The fight over New Melones galvanized the river conservation movement in California and influenced major water policy changes on the state and federal levels; since its completion, no other dams of its size or importance have been built in the United States.
The New Melones project has continued to generate controversy, due to the water yield from the project being lower than expected, and the use of New Melones water to meet federal environmental standards at the expense of farming. The reservoir is considered "over-allocated"; in an average year, it is unable to meet all the demands placed on it. The debate over water rights continues today, with environmentalists seeking to further increase fishery flows, and the Stanislaus irrigation districts asserting their senior rights to the river.
Specifications
New Melones Dam and its reservoir comprise the independent New Melones Unit of the Central Valley Project. The dam's primary purpose is to control the runoff from, or about 92 percent, of the watershed of the Stanislaus River, a major tributary of the San Joaquin River. At high from the foundations and long, and containing of material, New Melones is the second tallest earthfill dam in the United States, after Oroville Dam, and the sixth tallest dam overall. With a crest elevation of, the dam rises for above the streambed. Flood waters are released through an unlined spillway about a mile northwest of the dam, with a capacity of. The dam also has an outlet works which can release up to.Image:New_Melones_Dam_and_Reservoir_.jpg|thumb|left|New Melones Dam and Lake, looking north
The impounded water behind the dam forms New Melones Lake, which at full pool of above sea level encompasses of surface water and a volume of. About, 19 percent of the reservoir's capacity, is reserved for flood control. During flooding events, the dam is operated to keep flows on the Stanislaus River below, although this figure may be lowered depending on flow conditions in the San Joaquin River. Between 1978 and 2010 the dam prevented a total of $505 million in flooding damages, including $231 million during the New Year's flood of 1997 alone. However, the Manteca Bulletin noted that the dam was operated carelessly during the 1997 flood – almost of farmland was flooded near the confluence of the Stanislaus and San Joaquin Rivers – and a further $80 million of damage could have been prevented had the reservoir been kept at a safe level.
The dam's hydroelectric power plant is located at its base on the north side of the river, and has a rated hydraulic head of. The plant houses two 150.0 MW Francis turbines for a total capacity of 300 MW. Daily releases are made on a peaking basis; seasonal totals are dictated by irrigation and flood control requirements below the dam. The release from New Melones is re-regulated by the smaller downstream reservoir of Tulloch Dam, ensuring a stable flow in the Stanislaus River. For the period 2001 to 2015, the plant produced an average of 418 million kilowatt hours annually. This ranged from a high of 910 million KWh in fiscal year 2006, to a low of 130 million KWh in 2015. The plant replaced the old 22 MW power station at the original Melones Dam; on average it generates about four times as much electricity as the original did.
By controlling the flows of the Stanislaus River, the dam and reservoir make available of additional water each year. About of land along the Stanislaus River are irrigated using water from New Melones. According to the Bureau of Reclamation, the increase in water supply from New Melones Dam has "translated into prosperity for the region, allowing the growth of cities including Tracy and Manteca, and irrigating high-value crops including almonds, walnuts and grapes." In addition, New Melones Lake is one of the major tourist draws of the region, providing activities such as boating, fishing and shoreline camping. An estimated 800,000 people visit the lake each year; however, droughts can cause the closure of lake facilities due to low water levels.
History
Background
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 high concrete arch dam with a storage capacity of. 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 arch dam with a capacity of. As a primary flood control structure, it would protect 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 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, tall with a capacity of, or approximately one year's worth of Stanislaus River runoff.
Image:Stanislausmap1.png|thumb|left|Map of the Stanislaus River watershed, showing today's major dams and reservoirs.
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 twofold, as part of the Central Valley Project. The Bureau cited numerous benefits to a larger reservoir, which it estimated would capture 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. 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 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 waste of federal Central Valley Project funds. There was also concern that water from New Melones II might be exported outside the Stanislaus River basin and sold elsewhere; therefore, a rider attached to the 1962 act "reserved water for use within the basin with export of excess water only". Two years later, the Christmas flood of 1964 caused considerable damage along the Stanislaus River that a large dam could have prevented; Congressman John J. McFall "seized the political leverage that only could provide, and urged the drenched farmers to support New Melones Dam." With opposition having largely turned to support, Congress approved funding in 1965, with construction starting the following year.