Summary

Description

This data set consists of digital polygons of constant recharge rates 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 an east and west half with each half having an assigned recharge that was used as input to a ground-water flow model on the High Plains aquifer, during the calibration of the steady-state model. The east half was assigned a constant recharge value of 0.45 inches per year and the west half 0.225 inches per year. The polygon boundaries and constant recharge rates 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 recharge 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.