COASTAL GROUNDWATER DISCHARGE SIMULATIONS/MODELS FOR MOBILE BAY

Terrestrial groundwater discharges to coastal drainage networks as baseflow and to coastal waters as fresh submarine groundwater discharge. If groundwater discharge comprises a large portion of inflow or has a highly different chemical composition than the receiving waters, these groundwater fluxes can strongly influence the water chemistry of coastal waters. However, the spatial distribution of such fluxes makes quantifying the net effect of groundwater discharge difficult with field data. Furthermore, future climate conditions may change how groundwater interacts with surface water through changes in precipitation, evapotranspiration, and sea level. The U.S. Geological Survey (USGS), in cooperation with the Gulf Coast Ecosystem Restoration Council and the U.S. Environmental Protection Agency, is investigating surface water/groundwater interactions surrounding Mobile Bay. Here, we are developing and calibrating MODFLOW-based groundwater flow models using scripted workflows within the Python programming language and the FloPy library to investigate three questions: 1) How much groundwater discharge flows into Mobile Bay, 2) where does the groundwater discharge that flows into Mobile Bay occur, and 3) how do environmental variations associated with climate change affect the location and volume of groundwater discharge to Mobile Bay. By answering these three questions, we will provide valuable knowledge regarding variations in the magnitude and location of coastal groundwater discharge due to possible environmental changes.