It is a remnant of Lake Bonneville, an ancient postglacial inland sea that covered much of the western United States during the Ice Ages.

The runoff from these mountain regions create only intermittent surface flow to the lake, but does reach it via groundwater seepage.

The outflow mostly consists of evaporation, and a very small amount seeps through the sandspit that impounds it from the main Great Salt Lake valley.

During the ice ages, Rush Valley was merely one of many arms of Lake Bonneville.

These include, in order of abundance, Utah chub, carp, green sunfish, bluegill, largemouth bass, channel catfish, yellow perch, black crappie, and black bullhead.