APPROACHES TO ASSESSING POTENTIAL IMPACTS OF CLIMATE CHANGE ON A KARSTIC AQUIFER IN A SEMI-ARID CLIMATE

The San Antonio segment of the Edwards Aquifer in south-central Texas is a prolific karst aquifer system serving the needs of nearly 2 million people and supporting several threatened and endangered species. Like many confined karst aquifers, the Edwards Aquifer has limited storage, and the sustainability of the aquifer is reliant on a reasonable balance of anthropogenic withdrawals, springflow, and recharge. Periods of drought can have a significant effect on the availability of water for consumptive use by the region’s inhabitants and environmental flow to the aquatic species at the springs.

Effective management of this important water resource for the next generation of users requires an assessment of the impacts of climate change. Global circulation model (GCM) projections indicate a high probability of increased temperatures for the south-central plains of the USA, but future changes in precipitation patterns for the region are less certain. However, GCM results may not be representative on a spatial scale required to effectively model recharge and groundwater flow in the Edwards Aquifer.

We have taken a multipronged approach to evaluate the potential impacts of climate change on the aquifer. These efforts include measurements of relevant climate data over the past decade or more coupled with assembly of meteorological data resources to characterize climatic trends in our region. We have partnered with researchers at the South Central Climate Adaptation Science Center to develop customized downscaled GCM output at spatial scales relevant to processes associated with groundwater and surface water modeling in our region. The temporal sequences in the GCMs capture potential changes in sequences of events provided to modeling efforts. With our partners at the University of Texas at San Antonio, the downscaled climatic data are used with explainable artificial intelligence (XAI) modeling to develop models for characterization of both meteorological and groundwater droughts and projections of aquifer water levels and springflow under various climate scenarios. While more work is needed to produce a comprehensive model set for the aquifer, the applied efforts provide examples of assessments of future climate suitable for use by other regional agencies.