New Don Pedro Dam, often known simply as Don Pedro Dam, is an earthen embankment dam across the Tuolumne River, about northeast of La Grange, in Tuolumne County, California. The dam was completed in 1971, after four years of construction, to replace the 1924 concrete-arch Don Pedro Dam. The dam serves mainly for irrigation water storage, flood control and hydroelectricity production, and impounds Don Pedro Reservoir in the foothills of the Sierra Nevada. The New Don Pedro Dam is owned and operated by the Modesto Irrigation District (MID) and Turlock Irrigation District (TID). At tall, the dam is the tenth highest in the U.S. and its reservoir is the sixth largest artificial lake in California. The original dam was named for the old mining town of Don Pedros Bar on the Tuolumne River, which in turn takes its name from prospector Pierre "Don Pedro" Sainsevain. Background Shortly after their formation in 1887, the MID and TID acquired water rights to the Tuolumne River to secure a water supply for their combined service area in the San Joaquin Valley. After selling revenue bonds totaling $4.1 million, the two irrigation districts began construction of the Don Pedro Dam (now known as Old Don Pedro Dam) in 1921, about upriver of the present location of New Don Pedro Dam. Upon its completion in 1923, this concrete gravity arch dam was the highest dam in the world, forming a reservoir with a surface area of . The dam's 15 megawatt (MW) hydroelectric plant, later expanded to 37.5 MW, delivered its first power in October 1923. Expanding Don Pedro or constructing a new dam altogether was first seriously considered in the 1940s because the existing dam could only store a year's supply of water for valley farmers, with no guarantee that a multiyear drought could be weathered. An enlarged Don Pedro would provide a "bank" of water storage for prolonged droughts, capture more spring runoff, and provide increased flood control. Another proponent of a high dam was the city of San Francisco, which also sought a share of the Tuolumne's water and decided to cooperate with the irrigation districts to construct the new dam. The U.S. Bureau of Reclamation made tentative studies for a high dam on the Tuolumne River as part of its Central Valley Project, though it later dropped the plans in favor of other sites. Construction In 1961, an overwhelming majority of