SWPA_alvbsn is a vector dataset of alluvial-fill basin statistics for the Southwest United States. Statistics for each basin include physical details such as area, landcover, elevation, slope and precipitation. Anthropogenic data for basin include landuse, population, and wateruse.

This is a 100-meter cell resolution raster dataset consisting of 1:750,000-scale surficial geology for California and 1:500,000-scale for Nevada, and parts of Utah, Colorado, New Mexico, and Arizona. This data set was aggregated from a compilation of geologic maps of the Southwest Regional GAP Analysis Project (ReGAP) along with California geology and the very southern portion of Oregon and Idaho geology.

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

The U.S. Geological Survey in cooperation with the Upper Arkansas Water Conservancy District, created a numerical groundwater-flow model for the Wet Mountain Valley alluvial aquifer using the finite-difference MODFLOW code with the Newton formulation solver. This numerical groundwater-flow model simulates water-budget components, groundwater and surface-water interactions, and evaluates the potential effects of aquifer storage and recovery through an added recharge simulation. The numerical model was spatially discretized into two layers with 261 rows and 133 columns of square cells at 250 meters on each side, for a total of 20,007 active cells. The model was rotated by 36 degrees to the northwest to align with the orientation of the valley and the assumed groundwater-flow directions. The numerical model was temporally discretized into 241 stress periods. The first stress period simulates a mean steady-state period, and the subsequent 240 stress periods were transient and simulate each month from 2000 to 2019. This U.S. Geological Survey data release includes all of the necessary files to simulate the Wet Mountain Valley alluvial aquifer and potential flow paths within it as described in the associated Scientific Investigations Report (https://doi.org/10.3133/sir20245105).

This data set represents the extent of the Basin and Range aquifers in the states of California, Utah, Arizona, and Nevada.

Data release containing geospatial data and metadata for select hydrogeologic characteristics of the alluvium in the Lower Arkansas River Valley, Southeast Colorado, 2002, 2008, and 2015. This data release accompanies U.S. Geological Survey Scientific Investigations Map 3378 (https://doi.org/10.3133/sim3378). Geospatial datasets and metadata include: - Rasters showing estimated thickness of the alluvium; fall-to-fall and spring-to-spring water-table altitude change, 2002 to 2008, 2008 to 2015, and 2002 - 2015; and estimated saturated thickness in the alluvium, fall and spring 2002, 2008, and 2015. - Shapefiles showing bedrock contours underlying the alluvium; the outline of the study area and John Martin Reservoir in Bent County, Colorado; well locations and measured water-level altitude in those wells in the fall and spring of 2002, 2008, and 2015. For the purposes of this data release, "fall" is defined as June 1 through November 30, and "spring" is defined as January 1 through May 31 and December 1 through 31 of the same year.

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 represents the extent of the Rio Grande aquifer system in the states of Colorado, New Mexico, and Texas.