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.

Accurate delineations of irrigated acreage are critical in the development of water-use estimates and in determining an accurate water budget for the hydrographic basins of the BARCAS study area. Currently, irrigated acreage is estimated routinely for only a few basins in the study area and these acreages are calculated and reported by township range section, quarter, and quarter-quarter. Satellite imagery from the Landsat Thematic Mapper (TM) platform was used to delineate irrigated acreage for the BARCAS study area on a field by field basis. Six hundred and forty-three fields were delineated by interpreting satellite data. The water source, irrigation system, crop type, and field activity were identified and verified through field reconnaissance. These data were integrated into the geodatabase and analyzed to develop reasonably accurate estimates of irrigated acreage for the 2000, 2002, and 2005 growing seasons by hydrographic area and sub-area. Estimated average annual potential evapotranspiration and average annual precipitation were incorporated into the geodatabase as ancillary data. Irrigated acreage in 2005 totaled nearly 32,000 acres ranging from less than 200 acres in Butte, Cave, Jakes, Long, and Tippett Valleys to 9,200 acres in Snake Valley. Cave, Irrigated acreage increased about 20 percent from 2000 to 2005, with Snake and White River Valleys experiencing the greatest increases. The source for about 80 percent of irrigation water applied during drier years is ground water pumped from wells. About 80 percent of irrigation water applied in 2005 was through sprinkler systems, and about 20 percent was through flood systems. Fields planted in alfalfa accounted for about 88 percent of the irrigated acreage.

Accurate delineations of irrigated acreage are critical in the development of water-use estimates and in determining an accurate water budget for the hydrographic basins of the BARCAS study area. Currently, irrigated acreage is estimated routinely for only a few basins in the study area and these acreages are calculated and reported by township range section, quarter, and quarter-quarter. Satellite imagery from the Landsat Thematic Mapper (TM) platform was used to delineate irrigated acreage for the BARCAS study area on a field by field basis. Six hundred and forty-three fields were delineated by interpreting satellite data. The water source, irrigation system, crop type, and field activity were identified and verified through field reconnaissance. These data were integrated into the geodatabase and analyzed to develop reasonably accurate estimates of irrigated acreage for the 2000, 2002, and 2005 growing seasons by hydrographic area and sub-area. Estimated average annual potential evapotranspiration and average annual precipitation were incorporated into the geodatabase as ancillary data. Irrigated acreage in 2005 totaled nearly 32,000 acres ranging from less than 200 acres in Butte, Cave, Jakes, Long, and Tippett Valleys to 9,200 acres in Snake Valley. Cave, Irrigated acreage increased about 20 percent from 2000 to 2005, with Snake and White River Valleys experiencing the greatest increases. The source for about 80 percent of irrigation water applied during drier years is ground water pumped from wells. About 80 percent of irrigation water applied in 2005 was through sprinkler systems, and about 20 percent was through flood systems. Fields planted in alfalfa accounted for about 88 percent of the irrigated acreage.

Accurate delineations of irrigated acreage are needed for the development of water-use estimates and in determining water-budget calculations for the Basin and Range carbonate-rock aquifer system (BARCAS) study. ISatellite imagery from the Landsat Thematic Mapper and Enhanced Thematic Mapper platforms were used to delineate irrigated acreage on a field-by-field basis for the entire study area. Six hundred and forty-three fields were delineated. The water source, irrigation system, crop type, and field activity for 2005 were identified and verified through field reconnaissance.

Accurate delineations of irrigated acreage are needed for the development of water-use estimates and in determining water-budget calculations for the Basin and Range carbonate-rock aquifer system (BARCAS) study. ISatellite imagery from the Landsat Thematic Mapper and Enhanced Thematic Mapper platforms were used to delineate irrigated acreage on a field-by-field basis for the entire study area. Six hundred and forty-three fields were delineated. The water source, irrigation system, crop type, and field activity for 2005 were identified and verified through field reconnaissance.

Accurate delineations of irrigated acreage are needed for the development of water-use estimates and in determining water-budget calculations for the Basin and Range carbonate-rock aquifer system (BARCAS) study. ISatellite imagery from the Landsat Thematic Mapper and Enhanced Thematic Mapper platforms were used to delineate irrigated acreage on a field-by-field basis for the entire study area. Six hundred and forty-three fields were delineated. The water source, irrigation system, crop type, and field activity for 2005 were identified and verified through field reconnaissance.

These data represent potential areas of ground-water discharge for selected hydrographic areas in eastern Nevada and western Utah. The data are based on phreatophyte boundaries published by the U.S. Geological Survey (USGS) and on unpublished boundaries mapped by the Southern Nevada Water Authority (SNWA). Selected basins also were mapped by the USGS during an aerial field reconnaissance. The largest phreatophyte extent from all the sources was typically selected as the final boundary where a basin was covered by multiple boundaries. Selected basins were field verified and modified to reflect the ground condition during the summer of 2005. This data set also includes subbasin boundaries identified by Sweetkind and others (2007) (See Source_Information). The table below lists the boundary sources for each valley and whether the data were ground verified. > Valley Sources Field > verified ------------------------------------------------------------------------------------------ >Little Smoky Nichols, 2000; Harrill, 1988 Yes >Newark Nichols, 2000; Harrill, 1988 Yes >Long Nichols, 2000; Harrill, 1988; SNWA Yes >Jakes Nichols, 2000; SNWA Yes >Butte Nichols, 2000; Harrill, 1988; SNWA Yes >Steptoe Nichols, 2000; Harrill, 1988; SNWA No >Tippett Nichols, 2000 No >Spring Nichols, 2000; Harrill, 1988; SNWA Yes >Snake Harrill, 1988; SNWA; Aerial No >Lake Harrill, 1988; SNWA; Aerial Yes >Cave SNWA; Aerial No >White River Harrill, 1988; SNWA; Aerial Yes

These data represent potential areas of ground-water discharge for selected hydrographic areas in eastern Nevada and western Utah. The data are based on phreatophyte boundaries published by the U.S. Geological Survey (USGS) and on unpublished boundaries mapped by the Southern Nevada Water Authority (SNWA). Selected basins also were mapped by the USGS during an aerial field reconnaissance. The largest phreatophyte extent from all the sources was typically selected as the final boundary where a basin was covered by multiple boundaries. Selected basins were field verified and modified to reflect the ground condition during the summer of 2005. This data set also includes subbasin boundaries identified by Sweetkind and others (2007) (See Source_Information). The table below lists the boundary sources for each valley and whether the data were ground verified. > Valley Sources Field > verified ------------------------------------------------------------------------------------------ >Little Smoky Nichols, 2000; Harrill, 1988 Yes >Newark Nichols, 2000; Harrill, 1988 Yes >Long Nichols, 2000; Harrill, 1988; SNWA Yes >Jakes Nichols, 2000; SNWA Yes >Butte Nichols, 2000; Harrill, 1988; SNWA Yes >Steptoe Nichols, 2000; Harrill, 1988; SNWA No >Tippett Nichols, 2000 No >Spring Nichols, 2000; Harrill, 1988; SNWA Yes >Snake Harrill, 1988; SNWA; Aerial No >Lake Harrill, 1988; SNWA; Aerial Yes >Cave SNWA; Aerial No >White River Harrill, 1988; SNWA; Aerial Yes

This digital dataset contains the locations of, and links to USGS gages on the surface-water network for the Central Valley Hydrologic Model (CVHM). The Central Valley encompasses an approximate 50,000 square-kilometer region of California. The complex hydrologic system of the Central Valley is simulated using the USGS numerical modeling code MODFLOW-FMP (Schmidt and others, 2006b). This simulation is referred to here as the CVHM (Faunt, 2009). Utilizing MODFLOW-FMP, the CVHM simulates groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis from 1961-2003. The total active modeled area is 20,334 square-miles. The CVHM includes complex surface-water management processes. The hydrology of the present-day Central Valley and the CVHM model are driven by surface-water deliveries and associated groundwater pumpage. The Streamflow Routing Package (SFR1) is linked to MODFLOW-FMP to facilitate the simulated conveyance of surface-water deliveries. If surface-water deliveries do not meet the farm-delivery requirement, the FMP invokes simulated groundwater pumping to meet the demand. The surface-water network represents a subset of the entire stream network in the valley. Even so, it covers about 3,000 kilometers of surface-water and is simulated using 208 stream segments that represent 2244 stream reaches, with 43 inflows and 66 diversion locations providing 64 routed and 41 non-routed deliveries. Most of these inflows are regulated by dams and most of the deliveries are conveyed through an extensive canal network. The routed deliveries are conveyed through the simulated surface-water network, while the non-routed delivery conveyance typically occurs through small canals or diversion ditches and are not directly simulated. Much of the surface-water diversion and delivery information was compiled by the California Department of Water Resources (DWR) for 21 water-balance subregions (WBSs) covering the valley floor (C. Brush, California Department of Water Resources, written commun., February 21, 2007). The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).

This digital dataset contains the locations of, and links to USGS gages on the surface-water network for the Central Valley Hydrologic Model (CVHM). The Central Valley encompasses an approximate 50,000 square-kilometer region of California. The complex hydrologic system of the Central Valley is simulated using the USGS numerical modeling code MODFLOW-FMP (Schmidt and others, 2006b). This simulation is referred to here as the CVHM (Faunt, 2009). Utilizing MODFLOW-FMP, the CVHM simulates groundwater and surface-water flow, irrigated agriculture, land subsidence, and other key processes in the Central Valley on a monthly basis from 1961-2003. The total active modeled area is 20,334 square-miles. The CVHM includes complex surface-water management processes. The hydrology of the present-day Central Valley and the CVHM model are driven by surface-water deliveries and associated groundwater pumpage. The Streamflow Routing Package (SFR1) is linked to MODFLOW-FMP to facilitate the simulated conveyance of surface-water deliveries. If surface-water deliveries do not meet the farm-delivery requirement, the FMP invokes simulated groundwater pumping to meet the demand. The surface-water network represents a subset of the entire stream network in the valley. Even so, it covers about 3,000 kilometers of surface-water and is simulated using 208 stream segments that represent 2244 stream reaches, with 43 inflows and 66 diversion locations providing 64 routed and 41 non-routed deliveries. Most of these inflows are regulated by dams and most of the deliveries are conveyed through an extensive canal network. The routed deliveries are conveyed through the simulated surface-water network, while the non-routed delivery conveyance typically occurs through small canals or diversion ditches and are not directly simulated. Much of the surface-water diversion and delivery information was compiled by the California Department of Water Resources (DWR) for 21 water-balance subregions (WBSs) covering the valley floor (C. Brush, California Department of Water Resources, written commun., February 21, 2007). The CVHM is the most recent regional-scale model of the Central Valley developed by the U.S. Geological Survey (USGS). The CVHM was developed as part of the USGS Groundwater Resources Program (see "Foreword", Chapter A, page iii, for details).