Monique Ammidown
This paper describes tools and methods to display results of the MODFLOW groundwater model developed by the USGS. Various methods of display are presented including animated 3D visualization of the groundwater structure; cell by cell quantification of flow in the model; mass balance comparisons of different categories of flow into and out of each model cell; and methods of quantifying flow between rows, columns, or layers by individual cells, areas, or the entire model. The use of ArcView and the ArcView Spatial Analyst and ArcView 3D Analyst extensions described as well as exporting finished simulations to animated presentations such as .avi files and PowerPoint.
The ArcView GIS software package, including the 3D analyst extension, from Esri is a versatile method to display and analyze groundwater modeling results. This documentation presents several methods to import, view and analyze model results from the GMS/MODFLOW software package in both 2D and 3D displays using ArcView.
Once the modeler is satisfied with the configuration and extent of the model cells developed in GMS, they have the option of exporting the model cells to an AutoCAD dxf export format. As part of RGDSS, an extension to ArcView was developed that will automatically translate the AutoCAD output form GMS into an ArcView shapefile with the required row and column attributes. At this point the bottom elevations for each cell as computed by GMS must be appended to the shapefile for use in 3D displays.
After the ground elevations and elevations for each layer are part of the attribute table of the model shapefile, the aquifer can be modeled in 3D using ArcView 3D analyst. A copy of the model shapefile is loaded for each layer and is displayed in a 3D Scene. First the 3D Analyst extension is loaded into ArcView and a new 3D scene is created. To display the shapefile with the elevations from the model, the Theme -> 3D Properties menu is displayed. To display Layer1 of the model, the base height is set to Layer1, the extrusion value (vertical dimension) is set to Ground and the Extrude by parameter is set to "Using as Absolute". This will display the model shapefile as 3D columns with the bottom of each column set at the bottom of Layer 1 and the top of each column set at the ground elevation.
Each layer of the model can be loaded and displayed in a similar fashion to allow the user to view the entire modeled aquifer. Individual colors have been adjusted for each layer and the background has been changed to white. These techniques are fully described in the users documentation included with ArcView 3D Analyst. Once the ground elevations and elevations for each layer are part of the attribute table of the model shapefile, the aquifer can be viewed as if flying over the model in 3D. This is accomplished using several scripts and an extension to ArcView. The first step in this process is to copy the extension, movie.avx, to the users ArcView extension directory. This script is available from the ArcScripts web site. The first step in displaying the flyby animation is to associate the view with the 3D scene. The next step is to create the animation properties. A dialog box is displayed allowing several parameters to be set by the user.
By pressing the Scene Preview button, the ArcView 3D display will show the aquifer in 3D perspective, moving along the model and showing successive slices of the aquifer. To save the animation as JPEG images for later import into a PowerPoint presentation, the user should select the Make Movies button, select the JPEG option under Exported Image Format, and uncheck the Delete Exported Files box.
In order to display MODFLOW results in ArcView, datafiles from the model simulation must be converted from MODFLOW output format to a tabular format with one record for each cell and one field for each time step in the model. Two computer programs have been developed for this purpose. The first program, decode_GMS.exe, converts the binary head or drawdown output file from GMS into a comma delimited text file for use by ArcView. The second program, cellbycell.exe, converts the individual cell flux terms from GMS output into comma delimited text files for use by ArcView. These programs were specifically developed for the output files generated by GMS, since it uses a slightly different output format than the USGS MODFLOW program. The decode and cellbycell programs can be easily modified for use by other MODFLOW packages.
It is important to note that these two programs will translate every stress period and time step included in the GMS output files. Close coordination with the modeler is required to achieve the exact display results desired. GMS and MODFLOW allow precise control of the specific stress periods and time steps to be saved from the simulation, and these saved time steps will be converted into tables
ArcView can be easily used to display model results in 2D (plan view) without the need for the 3D Analyst. The model shapefile previously is joined with the table results created from the model and can then be displayed and queried by any of the available tools in ArcView.
The first step in displaying model results is to load the model shapefile into a View in ArcView and open the attribute table. The next step is to load the model results. This is accomplished by selecting the table icon from the project window and selecting the Add button. The user selects the delimited text file created from the GMS output. Finally the results table is joined to the model attribute table and the entire model run is loaded into the model attribute table. This allows the shapefile to be color-coded by value for any time step in the simulation. The user can also zoom to any cell in the model and use the identify tool in ArcView to show the model results at any selected cell for each time step.
An ArcView project was created for an animated display of every drawdown in a transient model simulation. A script was created to allow the user to automatically step through each time step in the model and display the drawdown values for each cell. The corresponding month is shown in the display. Finally, a JPEG image of the view is created for each step in the model for later use in a PowerPoint presentation. The user simply selects the layer desired for display and clicks the animation icon. Five copies of the model shapefile (one for each layer) were loaded into the view and joined with the appropriate result table to allow viewing of all of the model layers in turn.
To display results from a different model run, the user will simply open the attribute table of each layer, remove the joined result table, and rejoin with the appropriate model result. The animation can then repeated to display the new results.
Many of the animations described in this document can take a large amount of computer time to process due to the complexity of the models and 3D GIS data utilized. To allow simple display of the animations at a later time, the images are saved as JPEG images for later use. By utilizing the PowerPoint display program, each image must be loaded sequentially. In order to load these images into PowerPoint in the correct order and exactly aligned on top of each other, two macros were written in Visual Basic.
To animate the images for a display, select Custom Animations from the Slide Show menu. Under the timing tab, highlight each picture frame in the "Slide objects without animation" box and then select the animate button. The user can then choose to animate automatically after a specified number of seconds, or on a mouse click. Finally, the Effects tab should be set to Appear so the overall effect is a continuous movie image.
Bruce Rindahl, Project Manager Brown and Caldwell 1697 Cole Blvd. Suite 200 Golden, CO 80401 Tel: (303) 239-5400 Fax: (303) 239-5454 brindahl@brwncald.com Monique Ammidown, Project Engineer Brown and Caldwell 1697 Cole Blvd. Suite 200 Golden, CO 80401 Tel: (303) 239-5400 Fax: (303) 239-5454 mammidown@brwncald.com