Surface drainage from the Las Vegas Valley flows to Lake Mead through several narrow streams called "washes." Gypsum Wash is located near the shores of Lake Mead, west of Callville Bay.

Severe thunderstorms in September 1998 resulted in a peak discharge at Gypsum Wash of 17,000 cubic feet per second. Damage along Northshore Road and parts of Lake Mead National Recreation amounted to about one million dollars. (USGS Fact Sheet 079-00, July 2000).