Assessment of the Vulnerability and Sustainability of Groundwater Resources in the Big Sunflower River Watershed, Mississippi under Changing Climate

Groundwater depletion from anthropogenic activities is of increasing concern worldwide. Changing climates add vulnerability and uncertainty to this concern. Currently, very few efforts have been devoted to projecting the impact of changing climate on groundwater resources for local and small-scale watersheds. In this study, we applied the USGS's MERAS (Mississippi Embayment Regional Aquifer Study) model to assess the impact of climate change on groundwater flow and budget in the Big Sunflower River Watershed (BSRW), an important area of intensive crop production in Mississippi with conditions annually ranging from insufficient to excessive rainfall. The impact of climate change on groundwater resources is likely through its influence on areal groundwater recharge due to changes in rainfall events. The US-EPA's HSPF (Hydrological Simulation Program-FORTRAN) model was employed to approximate the groundwater recharge rates under simulated wet (a 7% increase in rainfall above normal/average) and drought (a 7% decrease in rainfall below normal/average) conditions in the BSRW. These recharge rates were then used as the inputs to the MERAS model (a site-specific MODFLOW model) to simulate groundwater flow, level, and budget. An assessment of the vulnerability and sustainability of groundwater resources in the BSRW was achieved by comparing normal conditions to two simulation scenarios, i.e., the wet and drought conditions. Simulation results showed that a 7% increase (or decrease) in rainfall rate would result in a 1% increase (or decrease) in ground recharge rate. Impacts of climate change on groundwater variations in the BSRW through its impacts on rainfall rate were significant.