Geohydrologic reconnaissance of the Imperial Valley, California

The Imperial Valley occupies a broad lowland in the southern, wider part of the Salton Trough section of the Basin and Range physiographic province. The trough is a landward extension of the depression filled by the Gulf of California, from which it is separated by the broad, fan-shaped subaerial delta of the Colorado River. Much of the land surface is below sea level, and the valley drains northwestward to the Salton Sea, which was 232 feet below mean sea level in 1968. The Imperial Valley is bordered by the Chocolate Mountains on the northeast, the Peninsular Range of Baja California and southern California on the southwest, and the Salton Sea on the northwest; it is contiguous with the Mexicali Valley in Mexico on the southeast.