Santa Ana River
Prado Reservoir is a reservoir in northwestern Riverside County and southwestern San Bernardino County, a couple of miles west of the city of Corona, in the U.S. state of California. The reservoir has a capacity of and is formed by Prado Dam on the Santa Ana River. The dam is composed of rock-fill and has a height of 106 feet (32 m) above the original streambed. It was built on the upper end of the Lower Santa Ana River Canyon, where there is a natural constriction in the river. It is below 2,255 square miles (5,840 km²) of the Santa Ana River watershed. The dam was built by the United States Army Corps of Engineers and was completed in 1941.