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Numerical study of pumping induced groundwater flow in vicinity of an alluvial river
Proceedings of the 2020 Mississippi Water Resources Conference
Year: 2020 Authors: Fang J., Jia Y., Rigby J.R.
Water resource shortage increasingly constraints the development and sustainability of agriculture. Over-pumping has resulted in severe depletions of groundwater (GW) in the Mississippi Delta. To mitigate the problem, an USDA experimental study was proposed to reduce groundwater depletion via pumping from a high-level aquifer and injecting to a lower one. The pumping sites are set to be near the Tallahatchie River in Money County, Mississippi, USA, to take the advantage of water supply from the surface water infiltration. A finite element based numerical model, CCHE3D-GW, was developed in this study to study the drawdown process of the GW affected by the heterogeneous aquifer and surface water in the alluvial river. The numerical model was verified with a vertically averaged 2-D analytical solution considering pumping and surface water infiltration. The model were verified with two sets of meshes, in which 4 and 12 layers were applied in z direction, respectively. A 3-day field pumping test was conducted. The area of the field simulation case is 20.3 ✕ 28.6 km2. In this area of the Mississippi Delta, a 40 m thick heterogeneous sandy aquifer is overlaid by a 10 m thick low-permeable aquitard, approximately. Calibrations were conducted using the data of the pumping well and multiple observation wells. The simulation results agree well with the measured pumping data. With the calibrated parameters, a long-term (17 years) pumping was then simulated to better understand the GW balance and distribution in response to the pumping. It is found that the sandy aquifer provides a large portion of the pumped water while the supply from river is limited in the study site.