Groundwater modelling system (GMS) software - sophisticated groundwater modelling system software

Get a quick look at the models and features of GMS 3.1 including the new True-Layer approach for defining layer data.

This tour provides an overview of the incredible array of modeling tools available in GMS. It describes each of the model interfaces in GMS, the organization and layout of GMS, tools for graphical output, and information on how to learn more about each component of GMS. The quick tour should be completed by anyone who is new to GMS prior to attempting to build a groundwater model.

Layout

The GMS window is organized into the following sections:


	Modules


	GMS is organized into ten modules. Each module is associated with a particular object type. Only one module is active at any given time. As you switch modules, the menus and the tools unique to the active module are displayed.

	TIN. Used for surface modeling with Triangulated Irregular Networks (TINs)
	Borehole. Used to display and edit borehole data.
	Solid. Used to construct 3D models of stratigraphy using solid models.
	2D Mesh. Contains SEEP2D interface.
	2D Grid. Used for contouring and surface plotting.
	2D Scatter Point. Contains 2D geostatistics tools.
	3D Mesh. Contains FEMWATER interface.
	3D Grid. Contains MODFLOW, MODPATH, MT3DMS, RT3D, and SEAM3D interfaces. Also used to generate 3D iso-surface plots.
	3D Scatter Point. Contains 3D geostatistics tools.
	Map. Used to build conceptual models using GIS objects.


	Tools

The action that takes place when you click in the graphics window depends on which tool is active. The tools are organized into two groups. The first set of three icons is for manipulating the display. The second set of icons is a group of module-specific tools that are used for creating and editing objects in the graphics window.

The set of icons shown in this section of the tool palette are a function of the active module. A unique set of tools is provided for each module.


	Mini-Grid Plot


	The mini-grid plot in the tool palette is used to navigate 3D grids. The default viewing mode in the 3D grid module is the "orthogonal" mode. In this mode, you view one row, column or layer of the grid at a time. The mini-grid plot is used to control which row, column, or layer is being viewed.


	Macros


	The macros are a set of icons at the bottom of the tool palette. Macros are shortcuts to frequently used menu commands.


	Edit Strip

The edit strip at the top of the GMS window contains a set of macro buttons for opening, saving, and printing projects. It is also used to edit the coordinates of selected objects (points, nodes, vertices) and a set of combo boxes for selecting the active object or data set.

Help Strip

The help strip at the bottom of the GMS windows is used to display context-sensitive help. As you move the cursor over an item in a dialog, a menu command, or one of tools or buttons in the main window, a help string describing the function of the item is displayed in the help strip. The help strip is also used to display the coordinates and other status information corresponding to the cursor location.

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Background Images

When constructing a model within GMS, the first step is often to import and register a scanned digital image or aerial photo. This makes it possible to perform on-screen digitizing and ensures that objects are created at the proper location.

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Conceptual Models

There are two main methods for building models in GMS, the grid approach and the conceptual modeling approach. With the grid approach, the first step is to create a grid or mesh. The model parameters, source/sink data, and boundary conditions are assigned directly to the cells, nodes, and elements of the grid or mesh. This approach is well-suited for very simple models.

The most efficient approach for building realistic, complex models is the conceptual model approach. With this approach, a conceptual model is created using GIS objects, including points, arcs, and polygons. The conceptual model is constructed independently of a grid or mesh. It is a high-level description of the site including sources/sinks, the boundary of the domain to be modeled, recharge and evapotranspiration zones, and material zones within each of the layers. Once the conceptual model is complete, a grid or mesh is automatically constructed to fit the conceptual model, and the model data are converted from the conceptual model to the cells of the grid.

Feature Objects

Conceptual models are constructed using feature objects. Feature objects are points, arcs, and polygons. Feature objects can be created entirely within GMS or imported from a GIS using shapefiles. Model parameters are assigned to the feature objects.

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Grid Creation

Once the conceptual model is created, a grid or mesh is automatically generated from the conceptual model. The grid is fit to the model boundary and refined around wells or other user-specified refine points.

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Model Conversion

Once the grid is created, the next step is to overlay the conceptual model on the grid and automatically assign boundary conditions, source/sink terms, and material properties. If a change is made to the conceptual model, the grid model can be updated in seconds.

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MODFLOW

GMS includes a comprehensive graphical interface to the groundwater model MODFLOW. 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 MODFLOW as a pre- and post-processor. The input data for MODFLOW are generated by GMS and saved to a set of files. These files are read by MODFLOW when MODFLOW is launched from the GMS menu. The output from MODFLOW is then imported to GMS for post-processing.

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.

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