MS-VMS is a comprehensive MODFLOW-based ground-water flow and contaminant transport modeling system. The USGS modular ground-water flow model, MODFLOW, is the most widely-used ground-water flow model in the world. But in its original form, MODFLOW has certain limitations and cannot be used to simulate some complex problems encountered regularly by modelers, hydrogeologists, and engineers in the field. First, its complex data structure makes input/output an extremely cumbersome process, especially when several simulations are involved for calibration, sensitivity analysis, and current investigations. Second, MODFLOW has limited capabilities in simulating several commonly occurring situations that need investigation. MS-VMS overcomes these difficulties by providing a seamless modeling environment for rapid visual data preparation and interpretation using Groundwater Vistas for MODFLOW-SURFACT; two- and three-dimensional presentation graphics and animations of model data and results using a Tecplot Interface (TIF) for Tecplot, and additional modules to MODFLOW to enhance its physical and numerical modeling capabilities provided by MODFLOW-SURFACT.
MODFLOW-SURFACT forms the nucleus of MS-VMS. MODFLOW-SURFACT, through its new computational modules based on robust, efficient, and mass conservative algorithms, overcomes the limitations and eliminates several restrictions of MODFLOW and its current transport counterparts. A few of the aforementioned limitations concern rewetting of drained cells, handling of pumping wells, handling of unconfined recharge, MODFLOW's convergence and efficiency problems, solute mass balance problems, numerical dispersion and oscillations, and the implicit assumption of negligible impact of transient flow storage effects on transport. New enhancements further provided in MODFLOW-SURFACT 99 include rigorous saturated-unsaturated moisture movement, rigorous air flow calculations including air relative permeability and storage, and multiphase transport capabilities from an immobile, multicomponent NAPL source. MODFLOW-SURFACT is fully compatible with MODFLOW. This feature allows the user to import any previously created MODFLOW files with a few minor changes. Additional physical capabilities are also rapidly modeled by MODFLOW users due to the full compatibility with MODFLOW's I/O structures.
MS-VMS FEATURES AND PRODUCT HIGHLIGHTS
- Fully integrated graphical modeling environment for seamless pre- and post-processing of model data.
- Sophisticated, comprehensive subsurface flow and contaminant transport model, MODFLOW-SURFACT provides efficient simulations of complex subsurface conditions.
- Groundwater Vistas for MODFLOW-SURFACT (GVMS) provides plan and cross-sectional views for grid construction, problem definition, and post-processing of water levels, drawdowns, velocity vectors and contaminant concentrations.
- GVMS provides several tools for grid refinement, cutout (zoom) model construction, calibration statistics, model sensitivities, model restart, and graphical model manipulation along with display of calibration and results statistics, hydrographs and breakthrough curves.
- Tecplot provides high quality, three-dimensional visualization of model parameters and output including animated views, or animations of water level fluctuations, or contaminant movement.
- Import/Export capabilities in several formats for easy access to/from other databases or coverage.
Water Saturation (yellow indicates seepage face)
- Problems involving water withdrawal management from wells or wellfields.
- Problems involving rapid and large fluctuations of the water table.
- Problems involving unconfined recharge and seepage face conditions.
- Problems involving active or abandoned wells connecting multiple aquifers.
- Problems involving evaluation of pumping and tracer test data to determine hydraulic and transport properties of formations.
- Problems involving near field and far field simulations of ground-water flow and radionuclide transport.
- Problems involving soil and ground-water contamination and remediation including pump and treat, soil vapor extraction, air sparging, bioremediation, and natural attenuation.
- Fully and variably-saturated flow modeling
- Parent and transformation product transport modeling
- Migration pathline and capture zone delineation
- Interactive input preparation and grid construction
- Visualization of modeling results in two and three dimensions
INTERACTIVE INPUT PREPARATION AND GRID CONSTRUCTION
MS-VMS simplifies the cumbersome process of grid generation and preparation of data files through an interactive, easy-to-use graphical interface, Groundwater Vistas. The comprehensive mesh generator in Groundwater Vistas rapidly provides 2-D and 3-D finite-difference grids, thereby completely eliminating the tedium of model input preparation. The interface includes additional features such as importing AutoCAD DXF image files to facilitate the determination of the model boundaries. It also provides graphical input of pumping and observation well data.
Groundwater Vistas offers one of the most comprehensive suites of calibration tools of any ground-water modeling system. These tools include calibration of residuals and residual statistics for head, drawdown, concentration, and flux targets; running individual sensitivity simulations; and an automated sensitivity analysis.
MS-VMS provides complete 2-D and 3-D visualization capabilities. Its Graphical User Interface, Groundwater Vistas, offers 2-D input and output visualization both in plan and cross-sectional views including contour plots, pathlines, and velocity vectors. Through Tecplot, MS-VMS offers state-of-the-art 3-D visualization and animation. Tecplot vividly depicts piezometric surfaces, pathlines and velocity vectors, and isosurfaces of contaminant plumes. The Tecplot interface (TIF) module facilitates the use of Tecplot by seamlessly integrating the model information with the visualization process.
Three-dimensional animation is the most effective way to observe the changes in parameters such as head and contaminant concentrations in a transient simulation. Tecplot generates 2-D and 3-D animation sequences depicting changes in head, drawdown, and contaminant concentration with time. Tecplot also provides animated tours through three-dimensional information to visually depict complex systems.
MODFLOW-SURFACT forms the nucleus of MS-VMS. Recognizing that few contaminant transport codes compatible with MODFLOW are available, new transport modules were developed and integrated into MODFLOW-SURFACT.
MODFLOW-SURFACT FEATURES AND PRODUCT HIGHLIGHTS
- Extends physical modeling capabilities of MODFLOW for subsurface flow calculations.
- Enhances robustness and efficiency of MODFLOW even for its existing capabilities.
- Seamlessly integrates state-of-the-art, mass conservative, multicomponent contaminant transport capabilities into MODFLOW simulations.
- Dynamic memory allocation permits unlimited problem dimensions.
- Modular structure allows further development of additional simulation capabilities to provide a comprehensive, general purpose simulator within the MODFLOW framework.
- MODFLOW users require negligible training to implement the physics provided by the enhanced modules due to the use of MODFLOW's input/output structures. Modifications to existing MODFLOW pre- and post- processors to include the enhanced capabilities are, therefore, also minimal.
EXTENDED PHYSICAL MODELING CAPABILITIES OF MODFLOW FOR GROUNDWATER FLOW SIMULATIONS Version 1
- New flow package, BCF4, handles complete drying and rewetting of grid blocks including vertical flow components throughout the domain and delayed yield. Also provides axi-symmetric simulation option for quick pump-test type analyses.
MODFLOW sometimes encounters difficulties or fails to converge in drying/re-wetting situations. Furthermore, MODFLOW is incapable of handling complex fully three-dimensional unconfined situations with several dry model layers separating a water table from perched water conditions on overlying low conductivity units.
- New fracture well package, FWL4, provides automatic and physically consistent approportioning of a total well flow rate to the respective nodes of a well open to multiple layers. Also accounts for over-stressed systems and wellbore storage.
MODFLOW only provides a source/sink option at a grid-block to simulate wells causing several restrictions (numerical difficulties and/or nonphysical solutions) in multi-layer or unconfined systems which may be highly stressed or may have large temporal fluctuations.
- New recharge/seepage face package, RSF4, provides capability for non-ponding or prescribed ponding conditions. Also handles seepage-face boundary conditions.
MODFLOW recharge package provides unphysical predictions for unconfined systems if the water table reaches or is above land surface.
ENHANCED ROBUSTNESS AND EFFICIENCY FOR MODFLOW SIMULATIONS Version 1
Solvers available in MODFLOW are efficient for small or easy problems but become inefficient or fail altogether for large, complex problems.
- New adaptive time stepping and output control package, ATO4, provides great robustness and efficiency in all flow simulations cutting the timestep size when the simulation becomes difficult and increasing it when the difficulty passes. Also provides improved organization and control of simulation output.
MODFLOW's time stepping increases the step size in geometric progression indefinitely, sacrificing robustness, efficiency, and efficient control of simulation output.
- New conjugate gradient solution package, PCG4, provides a robust alternative to the available solvers in MODFLOW.
CONTAMINANT TRANSPORT SIMULATION FEATURES OF MODFLOW-SURFACT
- Accurate, robust, and efficient mass-conservative transport solution schemes.
- Numerical schemes, data input/output, grid considerations, and simulation control fully compatible with all MODFLOW and MODFLOW-SURFACT flow options.
- Axi-symmetric option for quick analyses of slug tests or tracer tests.
- Accommodates up to five contaminant species in a single simulation including first-order chain reactions which may occur due to radioactive decay (species dependent), or biochemical transformation (species and soil/location dependent).
- Provides linear or nonlinear (Freundlich) equilibrium adsorption options.
- Provides two, three, and four component dispersivity options for various anisotropic conditions. Under isotropic conditions, the three and four dispersivity formulations collapse to Scheidegger's two component (longitudinal and transverse) dispersivity equation.
- Consistent transport solution options - upstream, central, or mixed weighting for efficient solution, or Total Variation Diminishing (TVD) schemes for extremely accurate, physically correct solutions.
- Complete consideration of above simulation options in computation speed and memory allocation.
NUMERICAL SCHEMES FOR TRANSPORT
- Finite difference spatial discretization compatible with MODFLOW's schemes.
- Mass conservative solution scheme using primitive form of the transport equation.
- Total Variation Diminishing (TVD) schemes for physically correct solutions, with adaptive temporal weighting (between Crank-Nicholson and fully implicit) for maximum accuracy.
- Options also available for upstream, central or mixed spatial weighting.
- Options also available for fully implicit to fully explicit temporal discretization.
- Adaptive time stepping within transport to promote convergence or for stability requirements for explicit cases.
- No numerical oscillations in space or time, or numerically induced mass appearance or disappearance.
DYNAMIC MEMORY ALLOCATION ADVANTAGES
- Windows systems allocate available memory to all applications open on the computer. Efficient use of memory by MODFLOW- SURFACT maximizes available memory space for other user applications.
- Due to dynamic allocation of memory, simulation problem dimensions are limited only by available computer memory or prohibitively long simulation times for large, complex problems.
MODFLOW-SURFACT 2.2: CURRENT EXTENSION OF MODFLOW-SURFACT
MODFLOW-SURFACT 2.2 is the current extension of MODFLOW-SURFACT to include the following new features:
- Vadose Zone Flow and Transport
- Vapor Flow for SVE and Air Sparging Simulation
- Multiphase, Multicomponent Contaminant Transport with Biodegradation
- Robust and Efficient Newton-Raphson Nonlinear Solver
- Dual domain simulations representing retarding mechanisms for both equilibrium and kinetic adsorption processes
MODFLOW-SURFACT 2.2, the most versatile MODFLOW-based model available, has the capability that exceeds the combined capabilities of MODFLOW, MT3DMS, FEMWATER/LEWASTE, MODFLOWT, MODAIR/P3DAIR, and AIRFLOW/SVE.
MODFLOW-SURFACT 2.2 ATTRIBUTES
- New flow package is extended for rigorous unsaturated zone water flow modeling using Richard's equation for saturated-unsaturated systems (air is treated passively).
- New flow package is extended to simulate rigorous air phase flow including relative permeability functions for air and compressibility effects (water is treated passively).
- New Newton-Raphson package with backtracking, NRB1, provides a robust alternative for highly nonlinear situations when time steps are exorbitantly small or steady-state solutions fail with MODFLOW's Picard-type iteration scheme.
- New Transport Package additionally allows for multiphase transport of volatile contaminants with advection and dispersion in the active phase, and diffusion, storage, and/or decay in the inactive phase.
- New Transport Package is further extended to simulate dissolution and volatilization of an immobile multi-component NAPL contaminant, with subsequent reduction and disappearance of NAPL saturations (or appearance if reactions create contaminants above their combined solubility limit).
- Complete consideration of above simulation options in computation speed and memory allocation.
EXTENSIONS TO MODFLOW-SURFACT 2.2
- Options to perform surface-water modeling, groundwater modeling and integrated surface-water-groundwater modeling.
- Full integration of surface-water features such as overland flow and channel flow with the unsaturated/saturated groundwater flow equations.
- Utilization of simultaneous solution schemes that rigorously couple the surface water and groundwater flow regimes.
- Fractured porous media simulations with dual porosity and discrete fracture representations.
- Density coupling between flow and transport for saltwater intrusion simulations.
- Enhanced biodegradation simulation capabilities taking into account microbial population dynamics and substrate interactions.
MS-VMS Requirements: Pentium CPU with 16 MB RAM and Microsoft Windows 95/98/2000/NT.