Developing Customized Downscaled Climate Projections for the Long-Term Management of the Edwards Aquifer System under a Warming Climate

The Edwards Aquifer, located in semi-arid south-central Texas, is a prolific karst aquifer that serves as a primary drinking water source for nearly 2 million people and provides environmental flow, sustaining habitats for several threatened and endangered species. The Edwards Aquifer has limited storage and the sustainability of the aquifer is reliant on balancing anthropogenic withdrawals, springflow, and recharge. Periods of drought can have significant impacts on water availability for the region’s inhabitants and the aquatic species at the major springs. Effective, long-term adaptive management of the Edwards Aquifer requires an assessment of the potential impacts of climate change on the groundwater, streamflow, springflow, and recharge in the region. Global climate model (GCM) projections indicate a high probability of increased temperatures across the South Central United States while future precipitation changes are less certain. However, GCM projections are on a scale that is not representative of the processes affecting the Edwards Aquifer. There are several pre-existing publicly available datasets of downscaled climate projections, but these pre-existing datasets were designed for other regions of the United States rather than the semi-arid region of south-central Texas. To provide guidance for the long-term management of the Edwards Aquifer, the South Central Climate Adaptation Science Center worked with the Edwards Aquifer Authority (EAA) to produce customized, high-resolution (1 km) downscaled climate projections specifically tailored to the Edwards Aquifer Region. This presentation will briefly walk through the process of producing these downscaled projections using GCMs from the Coupled Model Intercomparison Project Phases 5 and 6 (CMIP5 and CMIP6) and their use in additional modeling efforts with teams from the EAA, the University of Texas at San Antonio, and Oklahoma State University. This includes the evaluation and selection of GCMs used for downscaling, the downscaling procedure and the evaluation of the output projections, and the use of the downscaled climate projections in groundwater, streamflow, and springflow modeling for the Edwards Aquifer. The subsequent modeling, which includes the use of explainable artificial intelligence models and the Soil and Water Assessment Tool (SWAT), will provide a comprehensive model set for the Edwards Aquifer that can assess variations in future recharge and probabilities of groundwater drought. This talk will conclude with a discussion of the lessons learned and recommendations for creating downscaled projections in other regions for assessing the impacts of climate change on hydrology and the potential projected changes in temperature and precipitation in the Edwards Aquifer region.