Proceedings of the 2023 Mississippi Water Resources Conference

Year: 2023 Authors: Ouyang Y., Wei J.

Groundwater depletion due to the increasing water demand for agricultural, domestic, and industrial usages under a changing climate is a critical concern worldwide. Many regions of the world are now experiencing a certain degree of groundwater resource depletion. Mississippi Embayment (ME), encompassing parts of Missouri, Illinois, Kentucky, Arkansas, Tennessee, Mississippi, Alabama, and Louisiana, is an intensive crop production region in midsouth US and is one of the fastest groundwater resource depletion regions in the world. An understanding of the long-term stream and aquifer water exchange is crucial to groundwater resource planning, allocation, and management in the ME. Using the US Geological Survey's MERAS (Mississippi Embayment Regional Aquifer Study) groundwater model, we estimated the stream and aquifer water exchange in the ME over a 115-year simulation period from 1900 to 2014 under the following six different scenarios: (1) a base case scenario represents the current agricultural practices, groundwater pumping, and natural conditions existing in the ME; (2) an extreme wet scenario that is the same as the base case scenario except that the precipitation rate is increased by 20%; (3) an extreme dry scenario that is the same as the base case scenario except that the precipitation rate is decreased by 20%; (4) a no-pumping scenario that is the same as the base case scenario except without groundwater pumping; (5) a scenario without pumping with 20% increase in precipitation, which is the same as the extreme wet scenario except for without groundwater pumping; and (6) a scenario without pumping with 20% decrease in precipitation, which is the same as the extreme dry scenario except for without groundwater pumping. Simulations showed that more waters leaked from the aquifers to the streams than from the streams flowed into the aquifers over the past 115 years. There was about 3 times more aquifer water leaked to the streams without pumping than with pumping. Our study suggested that the groundwater pumping rather than the extreme precipitation played a vital role in stream and aquifer water exchange of the ME.