Development, calibration, and testing of ground-water flow models for the Mississippi River Valley alluvial aquifer in eastern Arkansas using one-square-mile cells

Abstract

Development of digital groundwater flow models of the Mississippi River Valley alluvial aquifer in eastern Arkansas was prompted by the growing concern about large water-level declines in the alluvial aquifer and by the need to better understand the flow system. Several flow models have been developed previously, but at scales that are too large for analyzing the effect of future pumping at a farm or local scale. Models developed and described in this report are at a one-square-mile cell scale that can be used to define local conditions. Because of the size of the study area, two models (a north model and a south model) were developed; the Arkansas River divides the study area and functions as a hydrologic boundary to the models. Both models simulate groundwater flow in one layer with recharge entering the aquifer from surface infiltration through the overlying confining unit and from seepage through riverbeds.

Updated estimates of water budget components for the Mississippi Embayment Region using a soil-water-balance model, 2000–2020

“…Previous groundwater studies in the Mississippi Alluvial Plain area, primarily those using groundwater flow models to study the groundwater system, have suggested groundwater recharge rates for the alluvial plain that range from less than 1 inch per year to no greater than 5 inches per year (see, for example, Ackerman, 1989Ackerman, , 1996Sumner and Wasson, 1990;Mahon and Poynter, 1993;Stanton and Clark, 2003;Clark and others, 2013;Killian and others, 2019;Gratzer and others, 2020;Wacaster, 2020). Pumping in the alluvial aquifer has drawn down the water table extensively, resulting in an induced increase in recharge over predevelopment rates (Ackerman, 1989(Ackerman, , 1996.…”

“…Pumping from this aquifer and underlying aquifers supplies water for the irrigation of crops, aquaculture, drinking water for urban areas, industrial supply, and other uses (Clark and others, 2011;Lovelace and others, 2020). The heavy use of this aquifer has caused substantial groundwater level declines in the alluvial plain of Arkansas and Mississippi, which has motivated a large number of hydrologic studies by the USGS aimed at understanding groundwater movement in the system of aquifers in the area and the potential effect of increasing or reducing pumping on groundwater supply and availability (Boswell and others, 1968;Cushing and others, 1970;Broom and Reed, 1973;Brahana and Mesko, 1988;Ackerman, 1989Ackerman, , 1996Mahon and Ludwig, 1990;Sumner and Wasson, 1990;Arthur and Taylor, 1998;Arthur, 2001;Brahana and Broshears, 2001;Mahon and Poynter, 1993;McKee and Clark, 2003;Reed, 2003;Stanton and Clark, 2003;Kresse and Clark, 2008;Clark and Hart, 2009;others, 2011, 2013).…”