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.本地理数据库（geodatabase）包含用于表征阿肯色州、俄克拉荷马州与德克萨斯州境内爱德华兹-特里尼蒂含水层系统（Edwards-Trinity aquifer system）的空间数据集。具体涵盖以下内容： (1) 多边形范围数据集：用于表征含水层系统整体范围、被细分为子区域或亚单元的完整范围，以及各类特殊关注的多边形范围（例如无数据区域、其他含水层下伏区域、异常区域等）； (2) 各含水层子区域/亚单元的海拔栅格数据集； (3) 用于生成表面栅格的海拔等值线及（如适用）厚度等值线； (4) 用于数字化生成海拔或厚度等值线的配图地理参考图像。上述图像与数字化等值线仅作参考用途。 爱德华兹-特里尼蒂含水层系统的范围覆盖全部亚单元，其边界基于美国地质调查局（U.S. Geological Survey, USGS）水文图集730-E（Hydrologic Atlas 730-E，USGS HA 730-E）的爱德华兹-特里尼蒂含水层系统范围线与露头图划定，相关资料可访问http://water.usgs.gov/ogw/NatlAqCode-reflist.html 获取。本数据库包含“无可用数据”范围多边形，对应爱德华兹-特里尼蒂含水层系统底面无海拔数据的区域。此类多边形源自USGS HA-730-E第81幅图、美国地质调查局水资源调查报告85-4116（U.S. Geological Survey Water-Resources Investigations Report 85-4116，USGS WRIR 85-4116）第9幅图板，以及美国地质调查局水资源研究论文91-4071（U.S. Geological Survey Water-Resources Investigations Paper 91-4071，USGS WRIR 91-4071）第1幅图板的数字化成果。爱德华兹-特里尼蒂含水层系统共包含3个含水层亚单元，但本地理数据库仅发布最终的顶面与底面表面栅格。 顶面栅格的海拔数据源自USGS HA-730-E第84、98、114幅图，以及USGS WRIR 85-4116第8幅图板的海拔等值线地理参考图像。在爱德华兹-特里尼蒂顶面下伏佩科斯河冲积含水层（对应USGS HA 730-E中的佩科斯河流域冲积含水层）与高平原含水层（参见USGS HA 730-E中的高平原含水层）的区域，上述两个含水层底面的海拔即等同于爱德华兹-特里尼蒂含水层系统顶面的海拔。底面栅格的海拔数据源自USGS HA-730-E第81幅图、USGS WRIR 85-4116第9幅图板，以及USGS WRIR 91-4071第1幅图板的海拔等值线地理参考图像。 海拔等值线通过地理信息系统（GIS）工具插值生成表面栅格，所用工具可基于等值线数据生成水文一致性表面，必要时可从厚度（距地表深度）推导海拔，并将各子区域合并为单一表面。核心工具为ArcGIS、ArcMap中的“Topo to Raster”工具（Esri 2014）。ArcGIS Desktop: Release 10.2，Redlands, CA：环境系统研究所（Environmental Systems Research Institute）出品。