Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Fang J., Al-Hamdan M.Z., O'Reilly A.M., Ozeren Y., Rigby J.R.

In the Mississippi River Valley alluvial aquifer (MRVAA), declines in groundwater levels caused by agricultural irrigation have been observed and reported for the past several decades, indicating that the current practices for groundwater resources management are not sustainable. To mitigate this problem, the Groundwater Transfer and Injection Pilot (GTIP) project was initiated by the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) at Shellmound, Mississippi, which consists of one extraction well, two injection wells and 17 observation wells. An experimental operation was conducted to test the feasibility of managed aquifer recharge (MAR) technology, which included measurement of groundwater hydraulic heads and groundwater temperatures in the observation wells. In this study, the hydrogeological properties of the study area are obtained through the coupled inverse modelling of groundwater flow and heat transfer. The variably saturated groundwater flow is simulated by CCHE3D-GW developed by NCCHE, The University of Mississippi, and heat transport is simulated using the MT3D-USGS developed by the USGS. A weighted multiple-variate least squares objective function, which is used to minimize the discrepancies between the measured and simulation results, is formulated for the inverse problem. To obtain a unique solution, Tikhonov regularization is applied, in which the high-resolution data derived from an airborne electromagnetic geophysical survey measured by USGS is adopted as prior information. The local scale hydrological processes governing extraction and injection, i.e., the infiltration flow of water from the Tallahatchie River to the MRVAA and the spread of injection water in the aquifer, are then analyzed based on the calibration results, which will provide detailed understanding of the hydrogeological effects of the GTIP Project to complement other regional modeling activities.