Modflow-Surfact

Modflow-Surfact is the most comprehensive and versatile Modflow-Based
flow and transport model available

Modflow-Surfact is a comprehensive three-dimensional finite-difference flow and contaminant transport modeling code based on the USGS modular groundwater flow code, MODFLOW. Using new computational modules based on robust, efficient, and mass-conserving algorithms, Modflow-Surfact overcomes limitations and eliminates restrictions associated with Modflow and its current transport counterparts. Examples include rewetting of drained cells, handling of pumping wells, solute mass balance problems, numerical dispersion and oscillations, and the implicit assumption of the negligible impact of transient flow storage effects on transport. Modflow-Surfact is fully compatible with MODFLOW. This feature allows the user to import any previously created MODFLOW files with minimal effort, and take advantage of MODFLOW Graphical User Interface (GUI) tools such as GroundWater Vistas and Visual MODFLOW.

Modflow-Surfact offers the following advanced capabilities:

• Fully and variably saturated flow modeling
• Multi-species parent and transformation product transport modeling with first-order biochemical degradation
• Linear or nonlinear retardation for each species
• Vadose zone water flow and solute transport modeling
• Vapor-phase flow and transport for SVE and air sparging simulations
• Multiphase, multicomponent contaminant transport
• Fractured porous media simulation with dual porosity
• Treatment of prescribed-ponding recharge and seepage face conditions, as well as delayed yield
• Recharge package enhanced to overcome unphysical predictions for unconfined systems (e.g., the water table reaches or is above land surface)
• Fracture well package which automatically determines contributions from various nodal layers to the well pumping rate based on aquifer conditions; also includes wellbore storage effects
• Adaptive time stepping provides robustness and efficiency to promote stability and convergence for both flow and transport simulations
• Total Variation Diminishing (TVD) schemes for physically correct solutions with adaptive temporal weighting (between Crank-Nicholson and fully implicit) for maximum accuracy
• Robust and efficient Newton-Raphson solver for nonlinear problems
• Compatible with PEST and UCODE parameter estimation tools

Visualization & Animation
Modflow-Surfact is compatible with most available MODFLOW-based GUI, including GroundWater Vistas, Visual MODFLOW, GMS, PMWIN, ModIME, Tecplot, and Argus ONE for 2-D and 3-D visualization and animation capabilities. Two-dimensional visualization is utilized in both plan and cross-sectional views for contour plots, pathlines, and velocity vectors.

Three-dimensional animation is the most effective way to observe the changes in parameters such as head and contaminant concentrations in a transient simulation. Three dimensional visualization and animations have been used to depict but are not limited to: piezometric surfaces, pathlines, velocity vectors, and isosurfaces of contaminant