GEOLOGICAL FACTORS INFLUENCING THE VIABILITY OF AQUIFER STORAGE AND RECOVERY

Aquifer storage and recovery (ASR) is a cost-effective engineered method for storing water during low demand periods and recovering it during high demand periods. ASR utilization is under development in densely populated areas along the Balcones Fault Zone of Texas, such as the city of New Braunfels, that are experiencing long periods of drought and high population growth. For drinking water New Braunfels relies entirely on the Edwards aquifer, which is seeing increasing stress because of high demand. As demand has increased, high TDS water of “the bad water zone” has intruded into the freshwater zone of the aquifer. This study characterizes the mineralogy and chemistry of the aquifer’s carbonate matrix, its original and diagenetic fabrics and textures, and how these features may contribute to water quality issues during ASR operations. Data on the mineralogy and bulk geochemistry correlate with groundwater geochemistry and provide insight into potential trace element mobilization to values above drinking water standards. Additionally, representation and evolution of hydrogeochemical facies informs the extent to which injection of fresh water during ASR operations may push back the intruding “bad water” zone.