This data set consists of digital base of aquifer elevation contours for the High Plains aquifer in the central United States. The High Plains aquifer extends from south of 32 degrees to almost 44 degrees north latitude and from 96 degrees 30 minutes to almost 104 degrees west longitude. The outcrop area covers 174,000 square miles and is present in Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. This digital data set was created by digitizing the base of aquifer elevation contours from a 1:1,000,000 base map created by the U.S. Geological Survey High Plains RASA project (Gutentag, E.D., Heimes, F.J., Krothe, N.C., Luckey, R.R., and Weeks, J.B., 1984, Geohydrology of the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Professional Paper 1400-B, 63 p.) The data should not be used at scales larger than 1:1,000,000.

The U.S. Geological Survey and its partners have collaborated to complete airborne geophysical surveys for areas of the North and South Platte River valleys and Lodgepole Creek in western Nebraska. The objective of the surveys was to map the aquifers and bedrock topography of selected areas to help improve the understanding of groundwater- surface-water relationships to be used in water management decisions. Frequency-domain (2008 and 2009) and time-domain (2010) helicopter electromagnetic surveys were completed, using a unique survey flight line design, to collect resistivity data that can be related to lithologic information for refinement of groundwater model inputs. To make the geophysical data useful for multidimensional groundwater models, numerical inversion is necessary to convert the measured data into a depth-dependent subsurface resistivity model. This inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation, is used to characterize hydrogeologic features. The two- and three- dimensional interpretation provides the groundwater modeler with a high-resolution hydrogeologic framework and a quantitative estimate of framework uncertainty. This method of creating hydrogeologic frameworks improved the understanding of the actual flow path orientation by redefining the location of the paleochannels and associated bedrock highs. The improved models represent the hydrogeology at a level of accuracy not achievable using previous data sets.

The U.S. Geological Survey and its partners have collaborated to complete airborne geophysical surveys for areas of the North and South Platte River valleys and Lodgepole Creek in western Nebraska. The objective of the surveys was to map the aquifers and bedrock topography of selected areas to help improve the understanding of groundwater-surface-water relationships to be used in water management decisions. Frequency-domain (2008 and 2009) and time-domain (2010) helicopter electromagnetic surveys were completed, using a unique survey flight line design, to collect resistivity data that can be related to lithologic information for refinement of groundwater model inputs. To make the geophysical data useful for multidimensional groundwater models, numerical inversion is necessary to convert the measured data into a depth-dependent subsurface resistivity model. This inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation, is used to characterize hydrogeologic features. The two- and three- dimensional interpretation provides the groundwater modeler with a high-resolution hydrogeologic framework and a quantitative estimate of framework uncertainty. This method of creating hydrogeologic frameworks improved the understanding of the actual flow path orientation by redefining the location of the paleochannels and associated bedrock highs. The improved models represent the hydrogeology at a level of accuracy not achievable using previous data sets.

The U.S. Geological Survey and its partners have collaborated to complete airborne geophysical surveys for areas of the North and South Platte River valleys and Lodgepole Creek in western Nebraska. The objective of the surveys was to map the aquifers and bedrock topography of selected areas to help improve the understanding of groundwater-surface-water relationships to be used in water management decisions. Frequency-domain (2008 and 2009) and time-domain (2010) helicopter electromagnetic surveys were completed, using a unique survey flight line design, to collect resistivity data that can be related to lithologic information for refinement of groundwater model inputs. To make the geophysical data useful for multidimensional groundwater models, numerical inversion is necessary to convert the measured data into a depth-dependent subsurface resistivity model. This inversion model, in conjunction with sensitivity analysis, geological ground truth (boreholes), and geological interpretation, is used to characterize hydrogeologic features. The two- and three- dimensional interpretation provides the groundwater modeler with a high-resolution hydrogeologic framework and a quantitative estimate of framework uncertainty. This method of creating hydrogeologic frameworks improved the understanding of the actual flow path orientation by redefining the location of the paleochannels and associated bedrock highs. The improved models represent the hydrogeology at a level of accuracy not achievable using previous data sets.

This data set consists of digital polygons of constant hydraulic conductivity values for the High Plains aquifer in Oklahoma. This area encompasses the panhandle counties of Cimarron, Texas, and Beaver, and the western counties of Harper, Ellis, Woodward, Dewey, and Roger Mills. The High Plains aquifer underlies approximately 7,000 square miles of Oklahoma and is used extensively for irrigation. The High Plains aquifer is a water-table aquifer and consists predominately of the Tertiary-age Ogallala Formation and overlying Quaternary-age alluvial and terrace deposits. In some areas the aquifer is absent and the underlying Triassic, Jurassic, or Cretaceous-age rocks are exposed at the surface. These rocks are hydraulically connected with the aquifer in some areas. The High Plains aquifer is composed of interbedded sand, siltstone, clay, gravel, thin limestones, and caliche. The proportion of various lithological materials changes rapidly from place to place, but poorly sorted sand and gravel predominate. The rocks are poorly to moderately well cemented by calcium carbonate. The High Plains aquifer was divided into three zones with each zone having an assigned hydraulic conductivity that was used as input to a ground-water flow model on the High Plains aquifer. These values are 8.3 feet per day for the west zone, 16.2 feet per day for the central zone, and 19.3 feet per day for the east zone. The polygon boundaries and constant hydraulic conductivity values were constructed by extracting lines from digital surficial geology data sets based on a scale of 1:125,000 for the panhandle counties and 1:250,000 for the western counties. Some of the lines were digitized from maps in a published water-level elevation map for 1980. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

This digital data set consists of saturated thickness contours for the High Plains aquifer in Central United States, 1996-97. The High Plains aquifer extends from south of 32 degrees to almost 44 degrees north latitude and from 96 degrees 30 minutes to 104 degrees west longitude. The aquifer underlies about 174,000 square miles in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. This data set was based on 10,085 water-level measurements, 49 stream elevations, (March 1997) and 10,036 water-level elevations from wells (1,370 from 1996 and 8,666 from 1997) and the base of aquifer value for each measurement location. The saturated thickness at each measurement location was determined by subtracting the water-level elevation from the base of aquifer at that location.

This USGS data release consists of two geospatial raster datasets and three geospatial vector data sets of water-level data. The data sets include a raster (A1) representing water-level change from predevelopment (about 1950) to 2015; the primary vector dataset (A2) of water-level-change data of static or near-static water levels in wells measured in predevelopment and 2015 (for wells in Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and Texas) and in wells measured in predevelopment and the latest available static or near-static water level from 2011 to 2015 (for wells in New Mexico and Wyoming), a supplemental vector dataset (A3) of water-level data used to manually substantiate the raster of water-level change from predevelopment (about 1950) to 2015, a raster (B1) representing water-level change from 2013 to 2015; and the vector dataset (B2) of water-level-change data for wells measured in 2013 and 2015. The supplemental vector data sets of water-level-change data used to manually substantiate the raster of water-level change from predevelopment (about 1950) to 2015 are composed of (1) water-level-change data from wells measured before June 15, 1978, but not during or before the predevelopment period for the area, and in 2015, (2) for wells not measured in predevelopment or before June 15, 1978 but measured in 1980 and in 2015, calculated water-level-change data derived from the sum of the water-level-change value from 1980 to 2015 and the beginning water-level-change value from the contours of water-level change, predevelopment to 1980 (Luckey and others, 1981; Cederstrand and Becker, 1999), (3) water-level-change data for wells located in Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and Texas and measured in predevelopment and 2014 and not measured in 2015, (4) water-level-change data for wells located in Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and Texas and measured in measured in predevelopment and 2013 and not measured in 2014 or in 2015, (5) the water-level-change data for wells located in Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and Texas and measured in measured in predevelopment and 2012 and not measured in 2013, 2014, or 2015, (6) the water-level-change data for wells located in Colorado, Kansas, Nebraska, Oklahoma, South Dakota, and Texas and measured in measured in predevelopment and 2011 and not measured in 2012, 2013, 2014, or 2015. The raster and vector data support USGS Scientific Investigations Report 2017-5040, Water-Level Changes and Change in Recoverable Water in Storage in the High Plains Aquifer, Predevelopment to 2015 and 2013-15.

This data set represents the extent of the Paleozoic aquifers in the states of South Dakota, Wyoming, and Montana.

This data set consists of digitized water-level elevation contours for the High Plains aquifer in western Oklahoma. This area encompasses the panhandle counties of Cimarron, Texas, and Beaver, and the western counties of Harper, Ellis, Woodward, Dewey, and Roger Mills. The High Plains aquifer underlies approximately 7,000 square miles of Oklahoma and is used extensively for irrigation. The High Plains aquifer is a water-table aquifer and consists predominately of the Tertiary-age Ogallala Formation and overlying Quaternary-age alluvial and terrace deposits. In some areas the aquifer is absent and the underlying Triassic, Jurassic, or Cretaceous-age rocks are exposed at the surface. These rocks are hydraulically connected with the aquifer in some areas. The High Plains aquifer is composed of interbedded sand, siltstone, clay, gravel, thin limestones, and caliche. The proportion of various lithological materials changes rapidly from place to place, but poorly sorted sand and gravel predominate. The rocks are poorly to moderately well cemented by calcium carbonate. The water-level elevations were measured in January, February, and March 1980 and ranged from about 4,650 feet above sea level in Cimarron County to about 2,000 feet above sea level in Woodward County. The water-level elevation contours were digitized from folded paper maps in a published report. The source maps were published at a scale of 1:250,000.