The study is one of a series of geohydrologic reconnaissance studies being made in the Lake Mead National Recreation Area and covers about 200 square miles (520 square kilometers) from Temple Bar to the Grand Wash Cliffs. Streamflow in the drainages tributary to Lake Mead is meager and extremely variable. Ground water is derived from two principal sources: (1) infiltration into permeable rocks near Lake Mead and (2) ground-water underflow in the basins that drain to the lake.
The volume of ground water derived from Lake Mead is much greater than that derived from the basins. In terms of potential groundwater development the rocks saturated by lake water probably extend less than 1 mile (1.6 kilometers) from the lake, whereas the basins that contribute underflow to the lake are of much larger areal extent. The most favorable sites for ground-water development are Grapevine Mesa, Sandy Point, Hualapai Wash, and the area near and south of Temple Bar; the permeable rocks include the conglomerate facies of the Muddy Creek Formation, the older alluvium, and the Chemehuevi Formation. The least favorable areas for ground-water development are those underlain by the mudstone facies of the Muddy Creek Formation. Seven sites are recommended for future ground-water development. Five sites are within 1 mile (1.6 kilometers) of Lake Mead and two sites are between 3 and 5 miles (5 and 8 kilometers) from the lake.
The ground water contains less than 1, 500 milligrams per liter of dissolved solids in most of the area. Ground water on Grapevine Mesa contains less than 500 milligrams per liter of dissolved solids, and that from springs in the metamorphic and plutonic rocks contains more than 1, 500 milligrams per liter of dissolved solids.
