This dataset was created in support of a study focusing on groundwater resources in the Great Basin carbonate and alluvial aquifer system (GBCAAS). The GBCAAS is a complex aquifer system comprised of both unconsolidated and bedrock formations covering an area of approximately 110,000 square miles. The aquifer system is situated in the eastern portion of the Great Basin Province of the western United States. The eastern Great Basin is experiencing rapid population growth and has some of the highest per capita water use in the Nation. These factors, combined with the arid setting, have levied intensive demand upon current groundwater resources and, thus, predictions of future shortages. Because of the large regional extent of the aquifer system, rapid growth in the region, and the reliance upon groundwater for urban populations, agriculture, and native habitats, the GBCAAS was selected by the U.S. Geological Survey (USGS) Water Resources program as part of the National Water Census Initiative to evaluate the Nation's groundwater availability. The complex stratigraphic and structural framework of the GBCAAS region controls groundwater flow throughout the region. A three-dimensional (3D) hydrogeologic framework was constructed to represent the hydrogeologic units and major structures in the region to aid in the development of both the conceptual and numerical groundwater-flow models of the study area. The 3D hydrogeologic framework was constructed by extracting and combining information from digital elevation models, geologic maps, borehole lithologic logs, geologic cross sections, and digital geophysical models. This dataset is composed of nine raster layers: 1. ubfau_top - Altitude of the top of the upper basin-fill aquifer unit in meters above North American vertical datum of 1988. 2. lbfau_top - Altitude of the top of the lower basin-fill aquifer unit in meters above North American vertical datum of 1988. 3. vu_top - Altitude of the top of the volcanic unit in meters above North American vertical datum of 1988. 4. ucau_top - Altitude of the top of the upper carbonate aquifer unit in meters above North American vertical datum of 1988. 5. uscu_top - Altitude of the top of the upper siliciclastic confining unit in meters above North American vertical datum of 1988. 6. tlcau_top - Altitude of the top of the thrusted lower carbonate aquifer unit in meters above North American vertical datum of 1988. 7. lcau_top - Altitude of the top of the lower carbonate aquifer unit in meters above North American vertical datum of 1988. 8. tnccu_top - Altitude of the top of the thrusted noncarbonate confining unit in meters above North American vertical datum of 1988. 9. nccu_top - Altitude of the top of the noncarbonate confining unit in meters above North American vertical datum of 1988.

This USGS data release contains the regional potentiometric contours representing the regional potentiometric surface for Clark County, Nevada, 2009-2015. Contours represent the groundwater-level altitude with a 250-foot contour interval and were created from groundwater elevations from 58 wells and surface elevations from 5 springs.

Hydrologic landscape regions group areas according to their similarity in landscape and climate characteristics. These characteristics represent variables assumed to affect hydrologic processes in the environment. Hydrologic landscape regions in Nevada were delineated using geographic information system tools and statistical methods including cluster analysis. The data layers of hydrogeology, precipitation, soil permeability, land surface slope and aspect were used to identify the hydrologic landscape regions. Sixteen hydrologic landscape regions were identified through cluster analysis. The hydrologic landscape regions are noncontiguous in nature and can range from small areas which tend to be in the mountain ranges to very large areas in the basins.

This digital geospatial data set consists of geohydrologic unit boundaries shown in the report "Structure, outcrop, and subcrop of the bedrock aquifers along the western margin of the Denver Basin, Colorado" (Robson and others, 1998).

This data set consists of sub delineations of the hydrographic area (HA) boundaries and polygons drawn at 1:1,000,000 scale for the Great Basin supplemented by information from HA drawn at 1:750,000 scale where necessary. See the process steps for more information.

This dataset was created in support of a U.S. Geological Survey (USGS) study focusing on groundwater resources in the Great Basin carbonate and alluvial aquifer system (GBCAAS). The GBCAAS is a complex aquifer system comprised of both unconsolidated and bedrock formations covering an area of approximately 110,000 square miles. The aquifer system is situated in the eastern portion of the Great Basin Province of the western United States. The eastern Great Basin is experiencing rapid population growth and has some of the highest per capita water use in the Nation. These factors, combined with its arid setting, have levied intensive demand upon current groundwater resources and, thus, predictions of future shortages. Because of the large regional extent of the aquifer system, rapid growth in the region, and the reliance upon groundwater for urban populations, agriculture, and native habitats, the GBCAAS was selected by the USGS Water Resources program as part of the National Water Census Initiative to evaluate the nation's groundwater availability. This dataset contains hydrographic area (HA) boundaries and polygons for the GBCAAS study area. The study area consists of 165 HAs based on Great Basin HAs defined by the USGS in 1988 (Harrill and others, 1988; Buto, 2009). The study area is characterized by north-south trending alluvial basins separated by intervening mountain ranges. HA boundaries generally coincide with the topographic highs separating these basins but may also contain arbitrary divisions that have no topographic control. HAs generally consist of thick layers of unconsolidated geologic deposits in the basins and consolidated bedrock in the mountain ranges. The basins are underlain by bedrock at varying depths. Much of the bedrock in the study area consists of permeable carbonate and volcanic rock strata, both of which allow some degree of hydraulic connection between hydrographic areas. The hydrographic area boundaries in this dataset have been assigned a code identifying each boundary as a potential barrier, conduit, or neutral zone to groundwater flow between basins. References cited: Buto, S.G., 2009, Digital representation of 1:1,000,000-scale Hydrographic Areas of the Great Basin: U.S. Geological Survey Digital Data Report 457, 5 p., Harrill, J.R., Gates, J.S., and Thomas, J.M., 1988, Major ground-water flow systems in the Great Basin region of Nevada, Utah, and adjacent states: U.S. Geological Survey Hydrologic Investigations Atlas HA-694-C, 2 sheets, scale 1:1,000,000.

This data set consists of 1:500,000-scale areas of dissolved solids in the Basin and Range Province of Nevada. The sources of this data set are sheets 3 and 4 of a 1984 U.S. Geological Survey Water-Resources Investigation Report (Thompson and Chapell, 1984.) Reference Cited Thompson, T.H., and Chappell, R., 1984, Maps showing distribution of dissolved solids and dominant chemical type in ground water, Basin and Range Province, Nevada: U.S. Geological Survey Water-Resources Investigations Report 84-4119-C, scale 1:500,000, 4 sheets.

This USGS data release represents data from the following publication: Plume, R.W., and Ponce, S.A., 1999, Hydrogeologic framework and ground-water levels, 1982 and 1996, middle Humboldt River basin, north-central Nevada: U.S. Geological Survey Water-Resources Investigations Report 98-4209, 2 plates, https://doi.org/10.3133/wri984209.

This data set represents the extent of the Southern Nevada volcanic-rock aquifers in Nevada.

This data set contains the potentiometric water-level altitude contours representing the 2009 potentiometric surface of the basin fill groundwater system of Dixie Valley, west-central Nevada.