QUANTIFYING GROUNDWATER AND SURFACE WATER INTERACTIONS IN THE FOUR MILE CREEK BURIED VALLEY AQUIFER

The Southwest Ohio region contains an abundance of alluvial aquifers, full of highly permeable glacial deposits and river sediment. These types of aquifers, especially when connected to surface streams, can yield large amounts of fresh drinking water that requires little treatment. Unfortunately, surface water being mixed in with groundwater presents risks of contamination, due to vulnerability of surface bodies to biological and chemical contaminants. The US Environmental Protection Agency (USEPA) classifies these systems as Groundwater Under the Direct Influence of Surface Water (GWUDISW) and treats them with the same purification standards as surface water. The purpose of this project is to determine the proportions of groundwater and surface water being pumped by municipal wells in Oxford, Ohio and to develop a flow model for the Four Mile Creek Buried Valley Aquifer during pumping conditions. The degree of groundwater – surface water interaction will be determined by sampling ¹⁸O concentration and general geochemistry of water in Four Mile Creek, at pumping wells, and at observation wells. These samples will also be analyzed for presence of E. coli to see if bacteria in the stream are making their way into the groundwater. Water level and hydraulic gradient will then be compared to the existing steady-state model, and developed into a pumping-state model for use by Miami University’s Geology department, and potentially the City of Oxford for well protection. Additionally, if the new hydrologic model differs from the current model, there could be implications regarding the maximum discharge of water that can be sustainably drawn from the aquifer without significant impact to groundwater recharge or stream ecology. The results would then be applicable to other alluvial aquifers that are hydraulically connected to surface water bodies, such as the Great Miami Buried Valley Aquifer, which supplies water to much of Southwest Ohio.