The Influence of Structural Features on Regional Groundwater Flow in
Trans-Pecos, Texas
This research project deals with regional-scale flow delineation in the Trans-Pecos Region of West Texas. One of the key elements is the influence of structural features (e.g., faults, folds, dissolution features) on regional groundwater flow patterns. The specific area of focus is a fault/syncline feature, called the Stocks Fault/Rounsaville Syncline, which runs from the northern boundary of Wild Horse Flat (in the southern Salt Basin) along the northern escarpment of
the Apache Mountains into the southern Toyah Basin. Historical data on groundwater heads and groundwater chemistry are used to identify hydrochemical facies in the groundwater and delineate flow paths in the aquifer. Strontium isotopes (87Sr/86Sr) are used to delineate regional flow paths in the study area. Preliminary results of strontium analysis of the groundwaters have indicated that high 87Sr/86Sr ratios derived from the Precambrian outcrops near the upgradient end of the flow system may act as a natural tracer that will identify the primary regional flow paths. Oxygen and hydrogen isotopes (
d18O and dD) are used to identify recharge areas and to help determine climatic conditions during recharge. Aerial photos and field investigations are used to determine fracture orientations and fracture densities. Information on flow paths and geochemical and isotopic facies will be correlated with information about the occurrence and orientation of structural features in the area, so that relationships between structures and groundwater flow paths can be demonstrated.This project is a collaboration with Profs. Jack Sharp, UT-Austin, and Matthew Uliana, Texas State University.