GMS 2.1 - Groundwater Modeling System

Πρόγραμμα Τελευταίας Τεχνολογίας για Μοντελοποίηση Υπόγειας Ροής

New in GMS 2.1
SEEP2D - Seepage Analysis Model!
RT3D - Bioremediation Simulation Model!

The Department of Defense GMS is the most sophisticated ground-water modeling environment available today. GMS integrates and simplifies the process of ground-water flow and transport modeling by seamlessly integrating all of the tools needed for a successful study.




MODFLOW is the most widely-used 3-D groundwater flow model in the world. MODFLOW can represent the effects of wells, rivers, streams, drains, horizontal flow barriers, evapotranspiration, and recharge on flow systems with heterogeneous aquifer properties and complex boundary conditions to simulate groundwater flow. Using GMS, the user can select a single cell or a series of cells and then quickly define the hydrogeologic characteristics and/or boundary conditions using interactive dialog boxes. In addition, a spreadsheet dialog can be displayed allowing the user to edit the values for each individual hydrogeologic characteristic for the entire model.
Input data may be imported or interpolated from a sparse set of scattered data points. GMS provides a user-friendly graphical interface to the popular MODFLOW model. This interface is used to assign boundary conditions and analysis parameters to the grid to be modeled. Existing MODFLOW input data files can be input directly. The MODFLOW model is also included.


MODPATH is a 3D particle-tracking model that computes the path a particle takes in a steady-state or transient flow field over a given period of time. MODPATH uses the head values and cell-by-cell flow terms computed by MODFLOW in addition to the soil porosity to compute the movement of each particle through the flow field. By specifying individual particle locations, MODPATH will compute the location of each particle at any instance in time. Both forward and backward tracking can be performed by MODPATH making it ideal for well capture zone and wellhead protection studies. The MODPATH Interface Module provides a user-friendly graphical interface to the MODPATH particle-tracking analysis model. This Interface is used to assign boundary conditions and analysis parameters to the grid to be modeled. MODPATH provides a graphical computation of 3D flowpaths using the output from either steady-state or transient groundwater flows computed by MODFLOW. The latest version of the USGS MODPATH is also provided.


MT3D is a 3-D contaminant transport model that can simulate advection, dispersion, sink/source mixing, and chemical reactions of dissolved constituents in groundwater flow systems. MT3D assumes that changes in the contaminant concentration field will not measurably affect the flow field. This enables the flow model to be independently constructed and calibrated. MT3D will retrieve the hydraulic heads and various flow and sink/source terms computed by MODFLOW, automatically incorporating the specified hydrologic boundary conditions.
The chemical reactions modeled by MT3D include equilibrium-controlled linear and non-linear sorption and first-order irreversible decay and biodegradation. The GMS MT3D Interface Module provides a user-friendly graphical interface to the popular MT3D contaminant transport model. This Interface is used to assign boundary conditions and analysis parameters to the grid to be modeled. The MT3D model is also included.


FEMWATER is a 3D flow and contaminant transport finite-element density-driven coupled or uncoupled model used to simulate both saturated and unsaturated conditions. It requires identification of material properties representing the hydrogeologic and transport characteristics of soil contained within the model. Boundary conditions and initial conditions are easily assigned by selecting nodes or element faces. Features such as wells, constant head, and no-flow boundaries are easily defined.
Transient data (such as recharge or well pumping), which is typically available in hydrograph form, can be input and edited graphically. This data can then be interactively assigned to a single element or a series of elements. The FEMWATER Interface Module provides a user-friendly graphical interface to the FEMWATER 3D flow and contaminant transport model. This Interface is used to assign boundary conditions and analysis parameters to the 3D finite-element mesh to be modeled. The FEMWATER model is also included.


SEEP2D is a 2D finite-element flow model designed to compute seepage on profile such as for earthen dam and levee cross sections. SEEP2D can be used to model confined, partially confined, and unconfined flow situations. For partially confined and unconfined flow situations, both the saturated and unsaturated flow is simulated and the phreatic surface determined. SEEP2D can model complicated 2-D seepage problems involving complex model geometries and soils that are nonhomogeneous and anisotropic.
SEEP2D is a steady-state flow model and will compute the flow value at each node of the finite-element mesh. From these values, flow lines and equipotential lines are plotted showing the resulting seepage flow net. The SEEP2D Interface Module provides a user-friendly graphical interface to the SEEP2D 2-D flow model. This Interface is used to assign boundary conditions and analysis parameters to the finite-element mesh to be modeled. The SEEP2D model is also included.


RT3D is a software package for simulating three-dimensional, multi-species, reactive transport in groundwater. The code is based on the 1997 version of MT3D (DOD_1.5), but has several extended reaction capabilities. RT3D can accommodate multiple sorbed and aqueous phase species with any reaction framework that the user wishes to define. With a variety of pre-programmed reaction packages and the flexibility to insert user-specific kinetics, RT3D can simulate a multitude of scenarios. For example, natural attenuation processes can be evaluated or an active remediation can be simulated. Simulations could potentially be applied to scenarios involving contaminants such as heavy metals, explosives, petroleum hydrocarbons, and/or chlorinated solvents. RT3D is highly flexible. The users can enter their own reaction kinetic expressions or choose from a suite of 8 pre-programmed reaction packages. Pre-programmed packages include: (1) Two Species Instantaneous Reaction (Hydrocarbon and Oxygen); (2) Instantaneous Hydrocarbon Biodegradation Using Multiple Electron Acceptors (O2, NO3-, Fe2+, SO42-, CH4); (3) Kinetically Limited Hydrocarbon Biodegradation Using Multiple Electron Acceptors (O2, NO3-, Fe2+, SO42-, CH4); (4) Kinetically Limited Reaction with Bacterial Transport (Hydrocarbon, Oxygen, and Bacteria); (5) Non-Equilibrium Sorption/Desorption (can also be used for Non-Aqueous Phase Liquid Dissolution); (6) Reductive, Anaerobic Biodegradation of PCE/TCE/DCE/VC; and (7) Combination of #3 and #7.


The Map Module allows the user to quickly develop a conceptual model and a corresponding numerical model for the area being studied, i.e., a TIFF image of an aerial photo or scanned-in map, or an AutoCAD or MicroStation DXF drawing of the site can be displayed as a background image allowing the user to define points, polylines, and polygons to represent spatially, associated modeling data. Boundary conditions and parameter values can be directly assigned to these graphical entities, i.e., points can define well-pumping data or point sources for contaminants; polylines can define rivers, drains, or model boundaries; and polygons can define areal data such as lakes, differing recharge zones or hydraulic conductivities.
Once the conceptual model has been defined, GMS will construct a grid, automatically refined around the wells, with the cells outside the model boundary already inactivated. The defined modeling data is then superimposed onto the grid with the appropriate parameters. For example, conductances assigned to polylines such as drains and rivers are automatically computed according to the length of the polyline segment within each cell. At this point, the model is completely defined and no cell editing is required. If the user decides to change the conceptual model (move a boundary, add additional wells, etc.), these changes can be made quickly. Drawing tools are also provided within the Map Module. These tools allow the user to draw text, lines, polylines, arrows, rectangles, etc., in order to add annotation to the graphical representation of the model. In addition, GIS data can be directly imported from or exported to ARC/INFO, ArcCAD, and ArcView.


The Subsurface Characterization Module is used to construct triangulated irregular networks (TINs) and solid models, and to display borehole data. TINs are formed by connecting a set of x-y-z points (either scattered, gridded, or from boreholes) with edges to form a network of triangles. TINs can be used to represent the surface of a geologic strata and can be displayed in oblique view with hidden surfaces removed. Solid models of stratigraphy can also be constructed allowing cross sections to be cut anywhere on the model.

Borehole Data

The Borehole module is used to manage borehole data for site characterization. A borehole can contain either stratigraphy data or sample data or both. Stratigraphy data are used to represent soil layers that are encountered in a soil boring. The soil layers are represented using contacts and segments . A segment represents a soil layer and a contact is the interface between two segments. Contacts and segments can be used to construct TINs, solids and 3D finite-element meshes. Sample data represent data obtained by continuous sampling along the length of the hole. Cone penetrometer data and down-hole geophysical data are examples of sample data. Sample data are stored in data sets which can be manipulated in a similar fashion as other data sets in GMS. For example, sample data from a cone penetrometer test may include data sets for tip resistance, sleeve resistance, and friction ratio. Sample data can be converted to scatter points which can be interpolated to a 3D grid or mesh from which isosurfaces and color-shaded contours can be generated. Sample data can also be used to infer soil stratigraphy.


TINs are surfaces representing the interface between adjacent stratigraphic units. They are constructed using selected contacts on the boreholes. Once a set of TINs is constructed, the TINs can be used to build solid models.

Solid Modeling

Solid models of stratigraphy can be constructed from TINs using simple extrusion methods coupled with Boolean operators. The resulting solids represent a 3D volumetric model of each soil layer. Cross sections can be cut on the solid models to better illustrate the stratigraphy.


The Geostatistics Module provides a number of different interpolation methods including kriging to transform existing field data into a useful form that can then be viewed and assigned to the model as input. Both 2D and 3D scattered data can be interpolated. To interpolate 3D contaminant point data, a set of x-y-z-c points can be input, where x-y-z represents the point location and c represents a contaminant concentration measured from borehole samples. The Geostatistics Module will then interpolate the concentration values from the measured scattered contaminant point data to a 3D grid. From this grid, an isosurface representing a threshold concentration value for the contaminant can then be generated to obtain a graphical representation of the contaminant plume.

Two-Dimensional Geostatistics

The 2D Scatter Point module is used to interpolate from groups of 2D scattered data to other objects (meshes, grids, TINs). The following interpolation schemes are supported.
  • Linear - Simple linear interpolation based on a triangulation of the scatter points.
  • Inverse Distance Weighted (IDW) - Includes constant, gradient plane, and quadratic nodal functions. Several subset search options.
  • Clough-Tocher - Piece-wise cubic patch approach adapted from finite-element method.
  • Natural Neighbor - Technique based on natural neighbors computed from Thiessen polygons. Works well with clustered data.
  • Kriging - Ordinary and universal kriging routines from the GSLIB software package. Graphical variogram editing.
    Interpolation is useful for setting up input data for analysis codes. For example, interpolation can be used to generate transmissivities for a layer of a 3D grid as input to a MODFLOW simulation. Interpolation is also useful for 2D plume mapping.

    Three-Dimensional Geostatistics

    The 3D Scatter Point module is used to interpolate from groups of 3D scatter points to any of the other data types (meshes, grids, TINs). The following interpolation schemes are supported.
  • Inverse Distance Weighted (IDW) - Includes constant, gradient hyperplane, and quadratic nodal functions. Several subset search options.
  • Natural Neighbor - Technique based on natural neighbors computed from Thiessen polyhedral. Works well with clustered data.
  • Kriging - Ordinary and universal kriging routines from the GSLIB software package. Graphical variogram editing. Anisotropy.
    Three-dimensional interpolation is useful for setting up input data for analysis codes. For example, a set of initial conditions (head and/or concentrations) must be defined for each node in the 3D mesh before a simulation can be performed. Three-dimensional interpolation can be used to generate a data set to be used for initial conditions from a limited set of measured scatter points. Three-dimensional interpolation is also useful for site characterization.


    The interface for GMS is divided into ten separate modules. A module is provided for each of the basic data types supported by GMS. As you switch from one module to another module, the Tool Palette and the menus change. This allows you to focus only on the tools and commands related to the data type the user wishes to use in the modeling process. Switching from one module to another can be done instantaneously to facilitate the simultaneous use of several data types when necessary. The following modules are supported in GMS: Triangulated Irregular Network (TIN) Module, Borehole Module, Solid Module, 2D Mesh Module, 2D Grid Module, 2D Scatter Point Module, 3D Mesh Module, 3D Grid Module, 3D Scatter Point Module, and Map Module.

    Data Sets

    An important feature of GMS is that the interface to each of the modules is designed in a consistent fashion. Once you become familiar with the interface to one of the modules, the other modules can be used with little further training. In order to help provide a consistent interface, the concept of generic data sets is used in GMS. A data set is a set of scalar or vector values associated with an object. Each data set can be either steady state or transient (multiple values representing the data values at different points in time). TINs, meshes, grids, and scatter point sets all have an associated list of scalar data sets and a list of vector data sets. Boreholes have a list of scalar data sets. Each set has a single vector or scalar value for each node, cell, borehole sample point, or scatter point.
    Data sets can be used to represent a variety of types of information. They can represent total heads computed by a groundwater model or starting heads used as initial conditions for input to a transient groundwater model. Data sets can be imported from a file or they can be created by interpolating from a group of scatter points.
    In some cases it is necessary to perform mathematical operations on data sets. This can be accomplished in GMS using the Data Calculator. For example, to compare the difference in the solutions from two separate simulations on a finite-difference grid, the two solutions can be input as data sets and the Data Calculator can be used to compute the absolute value of the difference between the two data sets. The resulting data set can be contoured or used to display isosurfaces.

    3D Viewing and Plotting

    GMS is a three-dimensional modeling environment. As such, it is often necessary to manipulate the viewing angle, viewing depth, and viewport as three-dimensional objects are displayed. A variety of tools are available in GMS for panning, zooming, and rotating 3D objects. Editing and model interaction can take place in any view.

    Output Options

    Once a modeling study is complete, several options are available in GMS for generating graphical output to include in a final report of the modeling study. These options are printing, exporting DXF or TIFF files, and copying images to the clipboard.


    Images can be printed by selecting the Print command in the File menu. On the PC, this prints the image to the currently selected printer. On Unix, a color or black and white postscript file is created which can be sent to a printer.

    Exporting a DXF or TIFF File

    Images can be exported to a DXF file by selecting the Export command in the File menu and selecting the DXF option. The DXF file can then be imported to a CAD package such as AutoCAD or MicroStation for editing or inclusion with other drawings in a final report. An image can be exported to a TIFF file by selecting the Export command in the File menu and selecting the TIFF option. TIFF files are bitmap type image files and can be imported into most graphics programs. On the PC, the simplest way to include a GMS image in a drawing or document in another application is to use the Windows clipboard. Selecting the Copy command in the Edit menu copies the currently displayed image to the clipboard. This image can then be pasted into a document in another application by positioning the cursor where you want the image to be located and selecting the Paste command in the Edit menu of the other application.


    Before printing an image or copying the image into another document, it is often useful to add some annotation to the image in order to provide a title or highlight important features. Annotation can be added with the drawing tools provided in the Map module. The annotation tools can be used to create text, lines, arrows, rectangles, and ovals.

    Visualization and Animation

    GMS has coupled the most advanced flow and transport codes available with the state-of-the-art in scientific visualization. From simple 2D contour plots of head and drawdown to fully 3D-rendered isosurfaces of contaminant plumes, it is second to none in graphics and visualization. A groundwater model can be displayed in plan view or 3D oblique view and rotated interactively. Cross sections and fence diagrams may be cut arbitrarily anywhere in the model. Hidden surface removal and color and light source shading can be used to generate high-quality images. Contours and color fringes can be used to display the variation of input data or computed results. Cross sections and isosurfaces can be interactively generated from 3D meshes, grids and solids, allowing the user to quickly visualize the 3D model. Both steady-state and transient solutions can be displayed in animation using either vector, isosurface, color fringe, or contour animation. For example, animation of a transient solution allows the user to observe how head, drawdown, velocity and contaminant concentration vary with time. In addition, GMS can also sweep an isosurface through the 3D model. The minimum and maximum isosurface values are determined from the model and the program will then linearly interpolate and display multiple isosurfaces in rapid succession. This allows the user to quickly understand the spatial variation of a contaminant plume. Film loops are saved in Microsoft Video for Windows (*.avi) format and can be played back outside of GMS using almost any multimedia player or presentation package such as Microsoft Powerpoint.


    Windows: 486/Pentium running Microsoft Windows 3.1/NT/95 with 16 MB RAM (32 MB recommended) and math coprocessor.
    UNIX X-Windows: AIX, HP-UX, IRIX, OSF, Sun OS, SPARC Solaris.

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