Simulation of ground-water flow in the Mississippi River Valley alluvial aquifer in eastern Arkansas

The U.S Geological Survey has developed and calibrated a digital model of the flow system in the alluvial aquifer as part of a multiagency Eastern Arkansas Region Comprehensive Study being conducted by the U. S. Army Corps of Engineers. Other cooperating agencies include the U.S. Soil Conservation Service, the Arkansas Soil and Water Conservation Commission, and the University of Arkansas. The study was prompted by the growing concern about significant water level declines in the Mississippi River Valley alluvial aquifer north of the Arkansas River in eastern Arkansas. The declines are a result of large groundwater withdrawals, mainly for irrigation. After calibration, the flow model was used to simulate the effects of projected groundwater pumpage through the year 2050, based on estimates made by the U.S. Soil Conservation Service for pumpage scenarios with and without water conservation measures. Simulations of projected pumpage indicated that by the year 2050 water level declines would reduce the saturated thickness of the aquifer to less than 20 ft in large areas of eastern Arkansas. More than 26% of the active cells in the scenario without conservation had saturated thicknesses of 20 ft or less and mroe than 16% in the scenario with conservation. The principal areas where the saturated thickness is expected to reach these critical levels are in the Grand Prairie region and in two areas on the east and west sides of Crowleys Ridge. (USGS)