A Refined Hydrogeologic Framework Model for Gaines, Terry, and Yoakum Counties, Texas

Abstract

Declining groundwater levels in Gaines, Yoakum, and Terry counties in the Southern High Plains have raised concerns about the amount of available groundwater and the potential for water-quality changes resulting from dewatering and increased vertical groundwater movement between adjacent water-bearing hydrogeologic units. More than 11,500 well records containing pertinent data were compiled, including data delineating the vertical extents of wells penetrating one or more of the units. Additional geophysical data were collected to improve the spatial coverage of available data across the study area and to reduce uncertainty regarding hydrogeologic unit extents. Across the study area, the average altitude of the base of the Ogallala Aquifer was approximately 1.7 feet lower compared to previous assessments of the altitude of the base of the aquifer, resulting in an increase in the saturated thickness by the same amount. Some of the largest increases in the altitude of the base of the Ogallala Aquifer were observed in central and east-central Gaines County where the units that compose the Edwards-Trinity Aquifer thin at approximately 136 feet and the largest decreases in altitudes are in Yoakum County at around 185 feet. Both the thickest and thinnest part of the Ogallala Aquifer is in Gaines County at just over 300 feet in west Gaines County and around 20 feet in northeast Gaines County. Citation: Thomas JV, Teeple AP, Payne JD, Ikard SJ. 2019. A refined hydrogeologic framework model for Gaines, Terry, and Yoakum counties, Texas. Texas Water Journal. 10(1):1-21. Available from: https://doi.org/10.21423/twj.v10i1.7082.