This data set consists of hydrogeology for the State of Nevada. Consolidated rocks and unconsolidated sediments are the two major hydrogeologic units. Consolidated rocks are subdivided into 8 hydrogeologic units: (1) carbonate rocks, Quaternary to Tertiary-age; (2) basaltic, (3) rhyolitic, and (4) andesitic volcanic flows; (5) volcanic breccias, tuffs, and volcanic rocks older than Tertiary-age; (6) intrusive and metamorphic rocks; (7) consolidated and semi-consolidated tuffaceous rocks and sediments; and (8) clastic rocks consisting of sandstone and siltstone. Unconsolidated sediments are subdivided into 4 hydrogeologic units: 1) alluvial slopes, (2) valley floors, (3) fluvial deposits, and (4) playas. In addition, soil permeability is provided and grouped into five descriptive categories ranging from very high to very low, which generally correspond to mapped geomorphic features such as playas and alluvial slopes. The geologic map of Nevada (Stewart and Carlson, 1978), published at a scale of 1:500,000, is the primary source of lithology used to delineate hydrogeologic units, enhanced with elevation and hydrologic data, and supplemented with Landsat Thematic Mapper imagery (Maurer and others, 2004). Cited References Maurer, D.K., Lopes, T.J., Medina, R.L., and Smith, J.L., 2004, Hydrogeology and hydrologic landscape regions of Nevada, U.S. Geological Survey Scientific Investigations Report 2004-5131, 35 p. Stewart, J.H., and Carlson, J.E., 1978, Geologic map of Nevada: U.S. Geological Survey, prepared in cooperation with the Nevada Bureau of Mines and Geology, 1:500,000 scale, 2 sheets.