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 dataset was created in support of a study focusing on ground-water 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 ground-water 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 ground water 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 ground-water availability. These data are derived from the Basin Characterization Model (BCM). The BCM is a distributed-parameter, water-balance accounting model that is run on a monthly time step. The BCM incorporates spatially distributed parameters (monthly precipitation, monthly minimum and maximum air temperature, monthly potential evapotranspiration, soil-water storage capacity, and saturated hydraulic conductivity of bedrock and alluvium) to determine where excess water is available in a basin and whether the excess water is stored in the soil or infiltrates downward into underlying bedrock. This dataset is composed of three raster layers. Two of the layers are outputs of the BCM model, one is an input. The layers are as follows: 1. Estimated average in-place recharge for the years 1940 to 2006 in the GBCAAS study area. In-place recharge is output from the BCM and is calculated as the annual mean amount of water that can drain from the soil zone directly into consolidated bedrock or unconsolidated deposits. 2. Estimated average runoff for the years 1940 to 2006 in the GBCAAS study area. Estimated runoff is output from the BCM and is calculated as the annual mean amount of water that runs off the mountain front or becomes streamflow. 3. Estimated saturated hydraulic conductivity (K) of bedrock and unconsolidated basin fill in the GBCAAS study area. The data are input to the BCM model as one of two temporally invariable inputs: storage capacity of soil and saturated hydraulic conductivity (Flint and Flint, 2007). The dataset was developed by applying assumed K values to geologic formations derived from 1:500,000-scale and 1:750,000-scale digital State geologic maps covering the study area. Hydraulic conductivity estimates of bedrock are uncertain because of the unknown hydraulic properties and spatial distributions of fractures, faults, fault gouge, and shallow infilling materials associated with different bedrock types and evaporative demand. These data are output from a model and should be used with caution. Refer to the larger work citation for details about the data and adjustments made to estimated recharge and runoff in water balance calculations made for the GBCAAS study. References cited: Flint, A.L., and Flint, L.E., 2007, Application of the Basin Characterization Model to estimate in-place recharge and runoff potential in the Basin and Range carbonate-rock aquifer system, White Pine County, Nevada and adjacent areas in Nevada and Utah: U.S. Geological Survey Scientific Investigations Report 2007-5099, 30p.

This dataset was created in support of a study focusing on ground-water 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 ground-water 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 ground water 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 ground-water availability. These data are derived from the Basin Characterization Model (BCM). The BCM is a distributed-parameter, water-balance accounting model that is run on a monthly time step. The BCM incorporates spatially distributed parameters (monthly precipitation, monthly minimum and maximum air temperature, monthly potential evapotranspiration, soil-water storage capacity, and saturated hydraulic conductivity of bedrock and alluvium) to determine where excess water is available in a basin and whether the excess water is stored in the soil or infiltrates downward into underlying bedrock. This dataset is composed of three raster layers. Two of the layers are outputs of the BCM model, one is an input. The layers are as follows: 1. Estimated average in-place recharge for the years 1940 to 2006 in the GBCAAS study area. In-place recharge is output from the BCM and is calculated as the annual mean amount of water that can drain from the soil zone directly into consolidated bedrock or unconsolidated deposits. 2. Estimated average runoff for the years 1940 to 2006 in the GBCAAS study area. Estimated runoff is output from the BCM and is calculated as the annual mean amount of water that runs off the mountain front or becomes streamflow. 3. Estimated saturated hydraulic conductivity (K) of bedrock and unconsolidated basin fill in the GBCAAS study area. The data are input to the BCM model as one of two temporally invariable inputs: storage capacity of soil and saturated hydraulic conductivity (Flint and Flint, 2007). The dataset was developed by applying assumed K values to geologic formations derived from 1:500,000-scale and 1:750,000-scale digital State geologic maps covering the study area. Hydraulic conductivity estimates of bedrock are uncertain because of the unknown hydraulic properties and spatial distributions of fractures, faults, fault gouge, and shallow infilling materials associated with different bedrock types and evaporative demand. These data are output from a model and should be used with caution. Refer to the larger work citation for details about the data and adjustments made to estimated recharge and runoff in water balance calculations made for the GBCAAS study. References cited: Flint, A.L., and Flint, L.E., 2007, Application of the Basin Characterization Model to estimate in-place recharge and runoff potential in the Basin and Range carbonate-rock aquifer system, White Pine County, Nevada and adjacent areas in Nevada and Utah: U.S. Geological Survey Scientific Investigations Report 2007-5099, 30p.

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 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 USGS Water Resources program as part of the National Water Census Initiative to evaluate the Nation's groundwater availability. This dataset consists of potentiometric contours, control points used to guide the creation of the contours, and a grid of 2 square-mile cells used to average the water-level value of selected control points. Control points are based on water-level measurements at well and spring locations from the USGS National Water Information System (NWIS, Mathey, 1998). Additional control points were derived from estimates of water-level altitudes in perennial mountain streams based on National Hydrography Dataset (NHD, 1999) stream reaches. References cited: Mathey, Sharon B., ed., 1998, National Water Information System (NWIS): U.S. Geological Survey Fact Sheet 027-98, 2 p., Accessed January 14, 2009 at U.S. Geological Survey, 1999, National Hydrography Dataset: U.S. Geological Survey Fact Sheet 106-99, accessed March 2007 at http://erg.usgs.gov/isb/pubs/factsheets/fs10699.html

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 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 dataset contains the amalgamation of the 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). This dataset does not contain the HA boundaries or geologic details included in the source dataset. For that information, please see the metadata for the source dataset at https://water.usgs.gov/GIS/metadata/usgswrd/XML/sir2010_5193_ha1000.xml The study area boundary dataset is used by the Office of Groundwater, U.S. Geological Survey, in its hyrogeological framework website.

This dataset contains the amalgamation of the 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). This dataset does not contain the HA boundaries or geologic details included in the source dataset. For that information, please see the metadata for the source dataset at https://water.usgs.gov/GIS/metadata/usgswrd/XML/sir2010_5193_ha1000.xml The study area boundary dataset is used by the Office of Groundwater, U.S. Geological Survey, in its hyrogeological framework website.

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. These data represent areas within the GBCAAS study area where groundwater discharge may occur as a result of evapotranspiration. The data were compiled from previously published groundwater discharge areas in the Great Basin.

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. These data represent areas within the GBCAAS study area where groundwater discharge may occur as a result of evapotranspiration. The data were compiled from previously published groundwater discharge areas in the Great Basin.