This geodatabase includes spatial datasets that represent the High Plains aquifer in the States of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. Included are: (1) polygon extents; datasets that represent the aquifer system extent, (2) raster datasets for the altitude of the top and bottom surfaces of the High Plains aquifer, (3) altitude contours of the top surface and of the bottom surface used to generate the surface rasters. The altitude contours are supplied for reference.

The extent of the High Plains aquifer is from the digital dataset U.S. Geological Survey Data Series 543 (USGS DS 543), and as a references, the digital version of the aquifer extent presented in the Groundwater Atlas of the United States (the U.S. Geological Survey Hydrologic Atlas 730-D, -E, and -C, (USGS HA 730-D, -E, -C).

The altitude contours for the top surface of the High Plains aquifer are from digital datasets of U.S. Geological Survey Open-File Report 99-263 (USGS OFR 99-263), using the 1980 water-level data. The altitude contours for the bottom surface of the High Plains aquifer are from the U.S. Geological Survey Open-File Report 98-393 (USGS OFR 98-393). The altitude of the bottom surface, or base, was originally from the High Plains Regional Aquifer-System Analysis study.

The resultant top and bottom altitude values were interpolated into surface rasters within a GIS using tools that create hydrologically correct surfaces from contour data, derive the altitude from the thickness (depth from the land surface), and merge the subareas into a single surface. The primary tool was an enhanced version of "Topo to Raster" used in ArcGIS, ArcMap, Esri 2014. The raster surfaces were corrected for the areas where the altitude of an underlying layer of the aquifer exceeded the altitude of an overlying layer.