A GROUNDWATER AVAILABILITY STUDY OF THE EDWARDS-TRINITY AQUIFER IN THE PECOS COUNTY REGION, TEXAS

Future groundwater availability is a concern in the Trans-Pecos region of west Texas, where the Edwards-Trinity aquifer is an important resource for agricultural, industrial, and municipal uses. A conceptual model of the Edwards-Trinity aquifer in the Pecos County region was developed as the second phase of a three-phase study. The initial phase developed a geodatabase, compiling hydrogeologic data from more than 8,200 locations. The final phase will develop a numerical groundwater-flow model. The conceptual model integrates the understanding of the hydrogeologic framework, geochemistry, and groundwater flow of the aquifer. The hydrogeologic framework consists of the hydrostratigraphy, structures, and hydraulic properties of the groundwater system. Geophysical and geologic data were used to determine hydrostratigraphic contacts, unit thicknesses, and delineate fault zones. Hydraulic properties were assessed where data were available. Geochemical and groundwater-level data were used in context with the hydrogeologic framework to assess groundwater flow, recharge, mixing of water from different sources, and discharge. Results indicate that the aquifer is dominated by mineralized, regional flow that likely recharged during cooler climatic conditions. Generally, groundwater flows from southwest to northeast and discharges to other aquifer units, from springs, or to the Pecos River. Mountains, troughs, and faults play substantial roles in the distribution of recharge, groundwater flow, spring discharge, and aquifer interaction. Results of this study, done in cooperation with the Middle Pecos Groundwater Conservation District, Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control and Improvement District No. 1, will be used for future aquifer management strategies.