Proceedings of the 2023 Mississippi Water Resources Conference

Year: 2023 Authors: Rossell W., O'Reilly A., Wren D.

In an effort to address the impact on groundwater resources caused by widespread pumping for irrigation in the Mississippi Delta region, the Groundwater Transfer and Injection Pilot (GTIP) project was undertaken by the U.S. Department of Agriculture, Agricultural Research Service, National Sedimentation Laboratory to assess the potential benefits of such a managed aquifer recharge practice. The GTIP project transfers source water obtained by riverbank filtration to an area of declining groundwater levels and recharges the aquifer using two injection wells. The facility has completed two pumping tests, a 3-month duration in 2021 and a 6-month duration in 2022. Throughout both tests, the inactive period between, and the inactive period following the 2022 test, groundwater level and groundwater quality data has been routinely recorded to evaluate the impacts of the project on the local environment. However, complicated circumstances and problematic events have also been encountered beyond those which were originally anticipated. This presentation will introduce some of these issues to the greater community and provide some current working hypotheses of causative factors. In particular, this presentation will briefly present the following topics: sinkhole formation on the GTIP project site, difficulties presented by the high iron concentration in the region's groundwater, the problem of injection well-screen clogging by iron-related bacteria, and unexpected groundwater drawdown during riverbank filtration. While the cause of many of these events is still under investigation and others may have been unavoidable, the benefit of presenting these negative results from the GTIP project is to better focus and expedite future research, leading to improved design criteria and more efficient operation and maintenance activities.