SEAWAT Model of Flow and Chloride Transport in the 1,500-Foot, 2,400-Foot, and 2,800-Foot Sands of the Baton Rouge Area, Louisiana

An updated three-dimensional, groundwater-flow and chloride-transport model (SEAWAT) of the Southern Hills regional aquifer system in southeastern Louisiana and southwestern Mississippi was developed to examine the effects of groundwater withdrawals on the rate and pathways of saltwater migration in the “1,500-foot” sand, “2,400-foot” sand, and “2,800-foot” sand. New interpretations of stratigraphic correlations amongst geophysical well logs were utilized to revise a hydrogeologic-framework that delineates the depth and thickness variations of aquifers and confining units in the Southern Hills regional aquifer system. Regional groundwater flow throughout the Southern Hills regional aquifer system was first simulated with MODFLOW, and flow-model parameters were calibrated to 8,810 water levels observed through 2016 with the parameter-estimation code PEST++. Saltwater transport was subsequently simulated for the “1,500-foot” sand, “2,400-foot” sand, and “2,800-foot” sand with the variable-density code, SEAWAT. Chloride-concentration measurements were used as a proxy for the saltwater to formulate the concentration initial conditions and calibrate the transport-model parameters. Three hypothetical groundwater management scenarios are included in the archive. These scenarios simulate the future water levels and chloride concentrations within the “1,500-foot” sand, “2,400-foot” sand, and “2,800-foot” sand if groundwater withdrawals were to continue at 2016 rates or if one of two proposed modifications to the 2016 withdrawals from the “1,500-foot” sand or “2,800-foot” sand were to be enacted. The model was calibrated to water levels measured in aquifers beneath the “400-foot” sand, and water levels simulated in these aquifers could be used for various purposes, including predicting the effects of changing pumping rates. Water planners and managers need additional knowledge about the effects of groundwater withdrawals on the rate and pathways of saltwater migration and a tool to assess possible management strategies that could control further saltwater encroachment in the Baton Rouge area. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20195102).