Accurate estimates of ground-water discharge are crucial in the development of a water budget for the Basin and Range Carbonate-rock Aquifer System (BARCAS) study area. One common method used throughout the southwest United States is to estimate ground-water discharge from evapotranspiration (ET). ET is a process by which water from the Earth's surface is transferred to the atmosphere. The volume of water lost to the atmosphere by ET can be computed as the product of the ET rate and the acreage of vegetation, open water, and moist soil through which ET occurs. The procedure used in the study, groups areas of similar vegetation, water, and soil conditions into different ET units and assigns an average annual ET rate to each unit. The data sets and the procedures used to delineate the ET-unit map are described in this metadata.

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 The data are based on phreatophyte boundaries published by the U.S. Geological Survey (USGS) and on unpublished boundaries mapped by the Southern Nevada Water Authority (SNWA).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

These data were created as part of a hydrologic study to characterize groundwater budgets and water quality in the Diamond Valley Flow System (DVFS), central Nevada. This dataset represents evapotranspiration (ET) units derived from the mean Enhanced Vegetation Index (EVI) calculated from two Landsat 5 Thematic Mapper scenes from the summer of 2010. ET units were defined within the DVFS groundwater discharge area (GDA) to group areas characterized by similar phreatophytic vegetation type and cover and to extrapolate site-scale groundwater ET estimates across the study area. This dataset represents three ET units: shrubland, grassland, and playa. The shrubland unit is composed of low to high density phreatophytic shrubs and bare soil while the grassland ET unit is composed of grassland, meadow, and marshland vegetation assemblages. The ET units were developed using a combination of EVI and site scale discharge measurements. The data were used to evaluate and estimate groundwater discharge by evapotranspiration in the study area. ET unit delineations reflect general spatial changes on the landscape and are not intended to be exact delineations of plant communities or soil conditions.

These data were created as part of a hydrologic study to characterize groundwater budgets and water quality in the Diamond Valley Flow System (DVFS), central Nevada. This dataset represents evapotranspiration (ET) units derived from the mean Enhanced Vegetation Index (EVI) calculated from two Landsat 5 Thematic Mapper scenes from the summer of 2010. ET units were defined within the DVFS groundwater discharge area (GDA) to group areas characterized by similar phreatophytic vegetation type and cover and to extrapolate site-scale groundwater ET estimates across the study area. This dataset represents three ET units: shrubland, grassland, and playa. The shrubland unit is composed of low to high density phreatophytic shrubs and bare soil while the grassland ET unit is composed of grassland, meadow, and marshland vegetation assemblages. The ET units were developed using a combination of EVI and site scale discharge measurements. The data were used to evaluate and estimate groundwater discharge by evapotranspiration in the study area. ET unit delineations reflect general spatial changes on the landscape and are not intended to be exact delineations of plant communities or soil conditions.

With increasing population growth and land-use change, urban communities in the desert southwest are progressively looking to remote basins to supplement existing water supplies. Recent applications for groundwater appropriations from Dixie Valley, Nevada, a primarily undeveloped basin neighboring the Carson Desert to the east, have prompted a reevaluation of the quantity of naturally discharging groundwater. The objective of this study was to develop a new, independent estimate of groundwater discharge by evapotranspiration (ET) from Dixie Valley using a combination of eddy-covariance evapotranspiration measurements and multispectral satellite imagery. Mean annual groundwater ET (ETg) was estimated during October 2009-2011 at four eddy covariance sites. Two sites were located in phreatophytic shrubland dominated by greasewood and two were located on a playa. Estimates were scaled to the basin level by combining remotely sensed imagery with field reconnaissance and site-scale ETg estimates. Vegetation index and brightness temperature data were used to partition Dixie Valley into five discharging ET units, and scale actual and potential ETg to the basin level. ET units are spatially constrained by a groundwater discharge area which represents the area where discharge from evaporation by open water or bare soil and transpiration from phreatophytic plants exceeds the volume of water contributed by precipitation. Each ET unit represents a generalized grouping of vegetation and soil conditions that were used as the basis of estimation of total ETg. ET units were partitioned as: playa lake, playa, sparse shrubland, moderate-to-dense shrubland, and grassland.

With increasing population growth and land-use change, urban communities in the desert southwest are progressively looking to remote basins to supplement existing water supplies. Recent applications for groundwater appropriations from Dixie Valley, Nevada, a primarily undeveloped basin neighboring the Carson Desert to the east, have prompted a reevaluation of the quantity of naturally discharging groundwater. The objective of this study was to develop a new, independent estimate of groundwater discharge by evapotranspiration (ET) from Dixie Valley using a combination of eddy-covariance evapotranspiration measurements and multispectral satellite imagery. Mean annual groundwater ET (ETg) was estimated during October 2009-2011 at four eddy covariance sites. Two sites were located in phreatophytic shrubland dominated by greasewood and two were located on a playa. Estimates were scaled to the basin level by combining remotely sensed imagery with field reconnaissance and site-scale ETg estimates. Vegetation index and brightness temperature data were used to partition Dixie Valley into five discharging ET units, and scale actual and potential ETg to the basin level. ET units are spatially constrained by a groundwater discharge area which represents the area where discharge from evaporation by open water or bare soil and transpiration from phreatophytic plants exceeds the volume of water contributed by precipitation. Each ET unit represents a generalized grouping of vegetation and soil conditions that were used as the basis of estimation of total ETg. ET units were partitioned as: playa lake, playa, sparse shrubland, moderate-to-dense shrubland, and grassland.

This data set contains polygons representing evapotranspiration (ET) units for the upper Humboldt River Basin, northeastern Nevada.

This data set contains polygons representing evapotranspiration (ET) units for the upper Humboldt River Basin, northeastern Nevada.

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.