General
The New Melones Dam and Powerplant are on the Stanislaus River, about 60 miles upstream from its confluence with the San Joaquin River and 40 miles east of Stockton. The river forms the boundary between Calaveras and Tuolumne counties, and drains an area of about 980 square miles on the western slope of the Sierras in east-central California. The Stanislaus River Basin has three major tributaries, the North, South and Middle forks; and the annual average flow is almost 1,000,000 acre-feet. The climate is semiarid, with hot, dry summers and cool, wet winters.
The primary function of New Melones Dam and Lake is flood control. Of the 2,400,000 acre-feet capacity, 450,000 acre-feet is reserved for flood control purposes.
The remaining capacity is used for a number of purposes including the satisfaction of preexisting water rights, fisheries enhancement, water quality improvement and electrical generation.
The New Melones powerplant provides power for the equivalent of 72,000 households.
History
Development of the Stanislaus River Basin began during the gold rush of the late 1840s. The Stanislaus River Basin and the region served by water from the basin were well developed and settled before construction of New Melones Dam. Development water companies diverted water for use by miners.
In the 1890s, utility companies began generating hydroelectric power on the river, much of which they sent outside the area.
The early 1900s saw development of several irrigation districts to serve local farmers.
In 1926, the Oakdale and South San Joaquin Irrigation Districts built the Melones Dam and Powerplant.
The peak of construction by irrigation districts came in the 1950s with construction of the Tri-Dam Project, which consists of the Donnells and Beardsley Dams on the upper Stanislaus River, Tulloch Dam on the lower Stanislaus River, and the enlargement of Goodwin Dam, also on the lower river.
Construction
Congress authorized the construction of New Melones Dam in 1944 to prevent flood damage caused by rain and snowmelt to the lands and communities downstream on the Stanislaus River. Congress modified the authorization in the 1962 Flood Control Act to include irrigation, power, wildlife and fishery enhancement, recreation and water quality as other reasons for construction of the dam.
The U.S. Army Corps of Engineers began construction of the dam in 1966, but public concerns over damage to cultural resources and the environment delayed completion until 1978. After the spillway and powerhouse were completed in 1979, the Corps transferred New Melones to Reclamation for integrated operation as the New Melones Unit of the East Side Division, Central Valley Project.
The waters of New Melones Lake cover the original Melones Dam, which was built in 1926 by the Oakdale and South San Joaquin Irrigation Districts to provide water for agriculture. New Melones Dam is located about 0.75 miles downstream of the original dam. The old reservoir could store 112,500 acre-feet of water; today, New Melones Lake has a capacity of 2.4 million acre-feet.
The two irrigation districts that built the original Melones Dam own and operate the downstream Goodwin Diversion Dam, which diverts Stanislaus River water into the district’s canal, and Tulloch Dam, Reservoir and Powerplant, located immediately downstream from New Melones Dam. Tulloch Reservoir provides Afterbay storage for reregulating power releases from New Melones Powerplant under a contract between Reclamation and the two districts. The powerplant has a generating capacity of 322,596,000 kWh.
Plan
New Melones Dam is located about 0.75 mile downstream from the original Melones Dam, built by the Oakdale and South San Joaquin Irrigation Districts in 1926. The original dam, a 183-foot concrete arch structure, is now submerged under the reservoir. The new dam, an earth and rockfill structure, stands 625 feet above streambed, has a crest length of 1,560 feet, and has a total embankment volume of 16 million cubic yards of material.
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