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GMS Software Models

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¡Ü MODFLOW 2000- GMS includes a comprehensive graphical interface to MODFLOW 2000. MODFLOW is a 3D, cell-centered, finite difference, saturated groundwater flow model developed by the USGS

¡Ü MODPATH- A particle tracking code that is used in conjunction with MODFLOW. Particles are tracked through time assuming they are transported by advection.

¡Ü MT3DMS- Simulation of multi-species transport by advection, dispersion, and chemical reactions of dissolved constituents in groundwater systems.

¡Ü RT3D- An advanced multi-species reactive transport model developed by the Battelle Pacific Northwest National Laboratory.

¡Ü SEAM3D- A reactive transport model used to simulate complex biodegradation problems involving multiple substrates and multiple electron acceptors.

¡Ü ART3D- A three-dimensional analytic reactive transport model developed by Dr. T. Prabhakar Clement.

¡Ü MODAEM- Analytic element model for simple flow and transport computations

¡Ü FEMWATER- A fully 3D finite-element model used to simulate density-driven coupled flow and contaminant transport in saturated and unsaturated zones.

¡Ü SEEP2D- A 2D finite-element groundwater model designed to be used on profile models such as cross-sections of earth dams or levees.

¡Ü UTCHEM- A multi-phase flow and transport model developed by the Center for Petroleum and Geosystems Engineering at the University of Texas at Austin. UTCHEM is ideally suited for pump and treat simulations.

¡Ü PEST- A model-independent, non-linear parameter estimator. The purpose of PEST is to assist in data interpretation, model calibration, and predictive analysis.

¡Ü UCODE- Developed by the USGS, UCODE is a universal inverse modeling code to solve parameter estimation problems.

¡Ü UTEXAS - UTEXAS quickly analyzes dams, levees and other slopes for the critical failure surface and factor of safety.

¡Ü T-PROGS- Used to perform transition probability geostatistics on borehole data.

MODFLOW

GMS includes a comprehensive graphical interface to the groundwater model MODFLOW 2000. MODFLOW is a 3D, cell-centered, finite difference, saturated flow model developed by the United States Geological Survey (McDonald & Harbaugh, 1988). MODFLOW can perform both steady state and transient analyses and has a wide variety of boundary conditions and input options. GMS supports the Observation (OBS), Sensitivity (SEN), and Parameter Estimation (PES) processes in addition to the new Layer Property Flow (LPF), Hydrogeologic Unit Flow (HUF), and Direct Solver packages. All other popular packages are supported, such as the HFB and Stream packages. GMS reads and writes native MODFLOW files so you will always have a transferable model!  

A special version of MODFLOW is distributed with GMS. Both the source code and executable are included. This version of MODFLOW is the same as the version distributed by the USGS except for a few minor changes primarily related to file input. These changes are clearly marked in the code.

MODPATH

MODPATH is a particle tracking code that is used in conjunction with MODFLOW. After running a MODFLOW simulation, the user can designate the location of a set of particles. The particles are then tracked through time assuming they are transported by advection using the flow field computed by MODFLOW. Particles can be tracked either forward in time or backward in time. Because of the user-friendly interface in GMS, an intimate knowledge of MODPATH is not required to effectively do particle tracking in GMS. Particle tracking analyses are particularly useful for delineating capture zones or areas of influence for wells.

MODPATH was developed by the U.S. Geological Survey. Version 4.2 of MODPATH is supported in GMS. The version of MODPATH distributed with GMS is the original public domain version distributed by the USGS, with minor modifications to accommodate GMS.

MT3DMS

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 MT3DMS uses a modular structure similar to the structure utilized by MODFLOW. MT3DMS is used in conjunction with MODFLOW in a two step flow and transport simulation. Heads and cell-by-cell flux terms are computed by MODFLOW during the flow simulation and are written to a specially formatted file. This file is then read by MT3DMS and utilized as the flow field for the transport portion of the simulation.

MT3DMS is a newer version of the MT3D model distributed with earlier versions of GMS. MT3DMS differs from MT3D in that it allows for multi-species transport, supports additional solvers, and allows for cell-by-cell input of all model parameters.

RT3D

RT3D is a multi-species reactive transport model developed by the Battelle Pacific Northwest National Laboratory. RT3D is a modified version of MT3DMS that utilizes alternate Chemical Reaction packages. Numerous pre-defined reactions are available and an option is provided for creating user-defined reactions. RT3D is well-suited for simulating natural attenuation and bioremediation.

SEAM3D

SEAM3D is a reactive transport model used to simulate complex biodegradation problems involving multiple substrates and multiple electron acceptors. It is based on the MT3DMS code. In addition to the regular MT3DMS modules, SEAM3D includes a Biodegradation package and NAPL Dissolution package. SEAM3D was developed by Mark Widdowson at Virginia Tech University.

ART3D

ART3D is a three-dimensional analytic reactive transport model developed by Dr. T. Prabhakar Clement. As a screening model, it is fairly simple and requires homogeneity and constant transport properties. It allows for complex reaction sequences with first order decay as well as three dimensional dispersion. A single retardation coefficient must be applied to all species. The user can enter any number of observation points and ART3D will exactly calculate the concentration of each specie at these points and compare then to known values (if included). In addition to a simple forward run, ART3D can be run in inverse and stochastic mode.

MODAEM

The MODAEM model is developed by Vic Kelson of Wittman Hydro Planning Associates in Bloomington, Indiana. Unlike finite difference and finite element models, analytic element models do not require a discretization of the problem domain. Rather the model is completely defined by boundary conditions, source/sink terms, and material property zones represented by points, polylines (arcs), and polygons. Since GMS users are already in the habit of building conceptual models in the Map Module using points, arcs, and polygons, analytic element modeling is a natural fit for GMS.

FEMWATER

A fully 3D finite-element model used to simulate densi- ty-driven coupled flow and contaminant transport in saturated and unsaturated zones. FEMWATER allows modeling of salinity intrusion and other density-dependent contaminants. Complex stratigraphy can be developed in GMS and directly represented in the model. Solutions can be displayed using realistic 3D plots and animation sequences.

SEEP2D

The 3D Grid module is used to create 3D Cartesian grids. These grids can be used for interpolation, iso-surface rendering, cross sections, and finite difference modeling.

SEEP2D can be used for either confined or unconfined steady state flow models. For unconfined models, there are two options for determining the phreatic surface. With the first option, the mesh is automatically truncated as the iterative solution process proceeds and when the model converges, the upper boundary of the mesh corresponds to the phreatic surface. With the second option, both saturated and unsaturated flow is simulated and the mesh is not modified. The phreatic surface can be displayed by plotting the contour line at where pressure head equals zero.

A variety of options are provided in GMS for displaying SEEP2D results. Contours of total head (equipotential lines) and flow vectors can be plotted. An option is also available for computing flow potential values at the nodes. These values can be used to plot flow lines. Together with the equipotential lines (lines of constant total head), the flow lines can be used to plot a flow net.

 UTCHEM

GMS includes an interface to the UTCHEM model in the 3D grid module. UTCHEM is a multi-phase flow and transport model developed by the Center for Petroleum and Geosystems Engineering at the University of Texas at Austin. UTCHEM is ideally suited for pump and treat simulations, particularly the simulation of surfactant-enhanced aquifer remediation (SEAR). Future iterations of the GMS/UTCHEM interface will include the simulation of biodegradation.

PEST

A model-independent, non-linear parameter estimator. The nonlinear parameter estimation algorithm used by PEST is uniquely robust and powerful having been developed for use with complex environmental models. The purpose of PEST is to assist in data interpretation, model calibration, and predictive analysis.

PEST is fully integrated into the GMS interface, allow you to perform advcned parameter estimation for MODFLOW models.

UCODE

UCODE is a universal inverse modeling code developed by the USGS to solve parameter estimation problems. In addition to evaluating estimated parameters values, it can be used to evaluate the model representation, diagnose inadequate data and quantify the likely uncertainty of model simulated values.

UTEXAS

UTEXAS quickly analyzes dams, levees and other slopes for the critical failure surface and factor of safety. Use CAD and GIS data to quickly set up a 2D profile model, or sketch it in GMS using the easy and familiar arc and polygon tools. Integrated with SEEP2D for pore pressure data, the combination makes for a full featured 2D profile analysis package.

T-PROGS

The T-PROGS software is used to perform transition probability geostatistics on borehole data. The output of the T-PROGS software is a set of N material sets on a 3D grid. Each of the material sets is conditioned to the borehole data and the materials proportions and transitions between the boreholes follows the trends observed in the borehole data. These material sets can be used for stochastic simulations with MODFLOW. A sample material set generated by the T-PROGS software is shown below. The T-PROGS software can also be used to generate multiple input data sets for the HUF package.

The T-PROGS software utilizes a transition probability-based geostatistical approach to model spatial variability by 3D Markov Chains, set up indicator cokriging equations , and formulate the objective function for simulated annealing. The transition probability approach has several advantages over traditional indicator kriging methods. First, the transition probability approach considers asymmetric juxtapositional tendencies, such as fining-upwards sequences. Second, the transition probability approach has a conceptual framework for incorporating geologic interpretations into the development of cross-correlated spatial variability. Furthermore, the transition probability approach does not exclusively rely on empirical curve fitting to develop the indicator (cross-) variogram model. This is advantageous because geologic data are typically only adequate to develop a model of spatial variability in the vertical direction. The transition probability approach provides a conceptual framework to geologic insight into a simple and compact mathematical model, the Markov chain. This is accomplished by linking fundamental observable attributes - mean lengths, material proportions, anisotropy, and juxtapositioning - with Markov chain model parameters.