This data set represents the extent of the Edwards-Trinity aquifer system in the states of Texas, Oklahoma, and Arkansas.

This data set represents the extent of the Mississippi embayment aquifer system in the states of Louisiana, Arkansas, Mississippi, Alabama, Tennessee, and Kentucky.

This data set represents the extent of the Central Oklahoma aquifer in Oklahoma.

A hydrogeologic framework of the Ozark Plateaus aquifer system was constructed as the base for a groundwater flow model developed as part of the U.S. Geological Survey Water Availability and Use Science Program to aid in the understanding of groundwater availability in select aquifer systems of the United States. The Ozark Plateaus aquifer system study area (hereinafter referred to as the “Ozark system”) is nearly 70,000 square miles and includes parts of Arkansas, Kansas, Missouri, and Oklahoma. A hydrogeologic framework was constructed to represent the altitudes and thicknesses of nine hydrogeologic units within the Ozark Plateaus aquifer system - . the Western Interior Plains confining system, Springfield Plateau aquifer, the Ozark confining unit, Ozark aquifer (divided into the upper, middle, and lower Ozark aquifers to better capture the spatial variation in the hydrologic properties), the St. Francois confining unit, the St. Francois aquifer, and the Basement confining unit. The formations that make up the hydrogeologic units of the Ozark system range from Pennsylvanian to Cambrian age. The scope of effort included the compilation and interpretation of hydrogeologic altitudes from geophysical, lithologic driller description, and well cutting logs. The final compiled dataset included more than 23,000 individual altitude points (excluding synthetic points) representing the nine hydrogeologic units. Shorthand names were used to identify points, extents, and raster surfaces corresponding to each hydrogeologic unit. WIPCS = Western Interior Plains confining system SPA = Springfield Plateau aquifer OCU = Ozark confining unit UOA = upper Ozark aquifer MOA = middle Ozark aquifer LOA = lower Ozark aquifer SFCU = St. Francois confining unit SFA = St. Francois aquifer BCU = basement confining unit

This data set represents the extent of the Texas coastal uplands aquifer system in Texas.

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 data set represents the extent of the Arbuckle-Simpson aquifer in Oklahoma.

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.