 Although the actual source of the water supply is from the Hetch Hetchy Reservoir on the Tuolumne River, the dam at Lake Eleanor provided the electric power needed for construction work at O'Shaughnessy Dam and the Hetch Hetchy Aqueduct, and also for the construction of Cherry Valley Dam 30 years later.The first power at Early Intake Powerhouse was generated on May 6, 1918.Construction on Cherry Valley Dam, which dams the main Cherry Creek to form Cherry Lake, began in August 1953 and was completed in October 1955.