Lake Cahuilla was a prehistoric lake in California and northern Mexico. Located in the Coachella and Imperial valleys, it covered surface areas of 5,700 km2 (2,200 sq mi) to a height of 12 m (39 ft) above sea level during the Holocene. During earlier stages of the Pleistocene, the lake reached even higher elevations, up to 31–52 m (102–171 ft) above sea level. During the Holocene most of the water came from the Colorado River with little contribution from local runoff; in the Pleistocene local runoff was higher and it is possible that Lake Cahuilla was supported solely from local water sources during the Wisconsin glaciation. The lake overflowed close to Cerro Prieto into the Rio Hardy, eventually draining into the Gulf of California.

The Colorado River is one of the principal rivers in the Southwestern United States and in northern Mexico. The 1,450-mile-long (2,330 km) river, the 5th longest in the United States, drains an expansive, arid watershed that encompasses parts of seven U.S. states and two Mexican states. The name Colorado derives from the Spanish language for "colored reddish" due to its heavy silt load. Starting in the central Rocky Mountains of Colorado, it flows generally southwest across the Colorado Plateau and through the Grand Canyon before reaching Lake Mead on the Arizona–Nevada border, where it turns south toward the international border. After entering Mexico, the Colorado approaches the mostly dry Colorado River Delta at the tip of the Gulf of California between Baja California and Sonora.