Karst Groundwater Vulnerability Determined by Modeled Age and Residence Time Tracers

Abstract

AbstractKarst aquifers are a vital groundwater resource globally, but features such as rapid recharge and conduit flow make them highly vulnerable to land‐surface contamination. We apply environmental age tracers to the south‐central Texas Edwards aquifer, a karst resource in a rapidly urbanizing and drought‐prone region, to assess vulnerability to land‐surface contamination and risks unique to karst aquifers. We show that vulnerability of Edwards aquifer groundwater follows similar spatial and depth patterns common to porous‐media type aquifers, despite complicated karst hydrogeologic features. Shallow and unconfined parts are more vulnerable to land‐surface contamination than the deeper and confined parts, although even the oldest groundwater is mixed with some recent recharge. When modeled age‐tracer results are coupled with other independent geochemical tracers of water‐rock interaction specific to karst settings, they can yield insight into residence time and associated vulnerability.