Simulation of water-management scenarios for the Mississippi Delta

To compare the effectiveness of proposed alternative water-supply scenarios on future water availability in the Mississippi Delta, the U.S. Geological Survey and the Mississippi Department of Environmental Quality are collaborating on the update and enhancement of an existing regional groundwater-flow model of the area. Through this collaboration, the model has been updated to include boundary conditions through March 2014 with the most recent water-use data, precipitation and recharge data, and streamflow and water-level observation data. The updated model has been used to evaluate selected alternative water-supply scenarios to determine relative effects on the Mississippi River Valley alluvial aquifer. Alternative water-supply options evaluated in this report include: (1) irrigation efficiency, (2) on-farm storage and tailwater recovery, (3) instream weirs to increase surface-water availability, (4) intrabasin transfer of surface water, and (5) groundwater transfer and injection. A relative comparison approach was used to calculate the simulated water-level response caused by each scenario. Water-level response is the difference between water levels simulated by the alternative water-supply scenario and those simulated by a base or “no action” scenario. Water-level response in the alluvial aquifer varied for each scenario based on the location, magnitude, and (or) adoption rates of the simulated alternative water-supply option. The groundwater transfer and injection scenario showed the largest water-level response.