Recent Enhancements to MT3DMS for Simulation of Solute Exchange in Hydraulically Connected Stream-Aquifer Systems

MT3DMS is the most widely applied groundwater solute transport code used in concert with the U.S. Geological Survey’s groundwater flow model, MODFLOW.  Due to the increasing number of packages available with MODFLOW, including those that simulate flow in the unsaturated-zone and in surface water networks (lakes, streams, and their corresponding groundwater/surface-water interaction), recent efforts have focused on expanding MT3DMS capabilities to include simulation of solute transport in the unsaturated-zone and surface water networks.  The enhanced MT3DMS model is compared against analytical solutions as well as against results from other published codes, including the U.S. Geological Survey’s OTIS and VS2DT models.  Results demonstrate the accuracy of the surface water and unsaturated zone transport solutions, as well as the ability to simulate stream-aquifer solute exchange.  Because enhancements are applied to the familiar MT3DMS model framework, current users can expand upon existing MODFLOW and MT3DMS model applications by activating the appropriate packages in both codes (e.g., the Unsaturated-Zone Flow (UZF1) and Streamflow Routing (SFR2) packages).  The enhanced version of MT3DMS is an effective tool for helping practitioners, researchers, and managers address increasingly complex solute transport concerns in settings that consider transport processes in the saturated and unsaturated zones, as well as in stream networks in hydraulic-connection to underlying aquifers.