Geodatabase of the available top and bottom surface datasets that represent the Edwards-Trinity aquifer system, Arkansas, Oklahoma, and Texas

This geodatabase contains the spatial datasets that represent the Edwards-Trinity 
aquifer system in the States of Arkansas, Oklahoma, and Texas. Included are: 
			
(1) polygon extents; datasets that represent the aquifer system extent, the entire 
extent subdivided into subareas or subunits, and any polygon extents of special 
interest (no data available, areas underlying other aquifers, anomalies, for example), 
			
(2) raster datasets for the altitude of each aquifer subarea or subunit, 
			
(3) altitude, and/or if applicable, thickness contours used to generate the surface 
rasters, 
			
(4) georeferenced images of the figures that were digitized to create the altitude or 
thickness contours. The images and digitized contours are supplied for reference.
			
The extent of the Edwards-Trinity aquifer system encompasses all subunits. It is 
delineated from the linework of the Edwards-Trinity aquifer system extent and 
outcrop maps of the U.S. Geological Survey Hydrologic Atlas 730-E 
(USGS HA 730-E) , available at http://water.usgs.gov/ogw/NatlAqCode-reflist.html. 
Included are the "no data available" extent polygons where there were no altitude 
data available for the bottom surface of the Edwards-Trinity aquifer system. These 
were digitized from USGS HA-730-E, figure 81, and U.S. Geological Survey 
Water-Resources Investigations Report 85-4116 (USGS WRIR 85-4116), plate 9, 
and U.S. Geological Survey Water-Resources Investigations Paper 91-4071 
(USGS WRIR 91-4071), plate 1. The Edwards-Trinity aquifer system has three 
aquifer subunits, but for the purposes of this geodatabase only the ultimate top 
and bottom surface rasters are published. 
		
The altitudes for the top surface raster are from georeferenced images of altitude 
contours from USGS HA-730-E, figures 84, 98 and 114, and USGS WRIR 85-4116, 
plate 8. In the areas where the Edwards-Trinity top surface underlies the Pecos 
River alluvial aquifer (USGS HA 730-E, Pecos River Basin alluvial aquifer), and the 
High Plains aquifer (see USGS HA 730-E, High Plains aquifer), the altitude of the 
bottom those two aquifers is the top of the Edwards-Trinity aquifer system. The 
altitudes of the bottom surface raster are from georeferenced images of altitude 
contours from USGS HA-730-E figure 81, USGS WRIR 85-4116 plate 9, and 
USGS WRIR 91-4071 plate 1.
			
The altitude contours were interpolated into surface rasters within a GIS using 
tools that create hydrologically correct surfaces from contour data, derives the 
altitude from the thickness (depth from the land surface) if necessary, and 
merges the subareas into a single surface. The primary tool was "Topo to Raster" 
used in ArcGIS, ArcMap, Esri 2014. ArcGIS Desktop: Release 10.2 Redlands, 
CA: Environmental Systems Research Institute.

Tags: aquifer, aquifer-system, arkansas, edwards-aquifer, edwards-trinity-aquifer, edwards-trinity-aquifer-system, extent, groundwater, inlandwaters, oklahoma, texas, trinity-aquifer, united-states, usgs-9d29d5e2-8539-4693-8f0f-085a5b59d03d
Organization: Department of the Interior