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Visual MODFLOW Flex and Classic

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This document describes how to pass models from Visual MODFLOW Flex to the Visual MODFLOW Classic Interface and how to load the results from a Classic run back into the Flex environment.

When do you need to switch to VMOD Classic Interface?

All new projects should begin within the Flex interface; however, if you need to use the following features, then you will need to migrate to the Classic interface to complete that portion of your project:

Flow Engines (MODFLOW-96)

Flow Packages (ETS1, STR, MNW)

Transport Engines (MT3D99, PHT3D)



Visual MODFLOW Flex

All new projects should begin within the Flex interface.

Create Your Conceptual Model

The first step is to create your conceptual model using the Visual MODFLOW Flex interface.  Starting with a conceptual model can save you a significant amount of your total project time, because the material properties and hydrological boundaries are done independent of the grid design and numerical engine selection.  This enables rapid adaptation of grid requirements to match property and boundary definitions, thus reducing modeling instability and convergence problems.  

Here are a few places to get started:

Conceptual Modeling Tutorial

Conceptual Modeling workflow – in more details

Some sample images from the conceptual model demo project are below:


Figure 1: Property Zones in the Conceptual Model


Figure 2: Boundary Conditions in the conceptual model: (constant heads on the east and west boundaries (colored red); a river through the middle of the model (colored blue), and 4 extraction wells)


When you transfer your flow model to Visual MODFLOW Classic, the names for the boundary conditions and wells are not preserved. If this is important, define only the geological model in Visual MODFLOW Flex, then add the boundary conditions in Classic.

Generate MODFLOW Grids

Once the conceptual model is designed, you must generate one or more MODFLOW grids.  This process is described in Conceptual Modeling Tutorial and further explained in the help section: “Creating MODFLOW Grids

Visual MODFLOW Flex allows you to generate various numerical representations of your conceptual model; this means you can experiment with various grid sizes, horizontal and vertical discretizations, etc.   This includes grids with Local Grid Refinement (LGR).


After a grid is generated, you may see something similar to the image shown below (in a 2D plan view)

Figure 3: Numerical Grid with Conceptual Boundary Condition Objects


Convert Conceptual Model to Numerical Model

After the grid is designed, you must populate the numerical model. Run the Conceptual to Numerical Conversion wizard as shown below:


This will generate a numerical model with grid layers, property cell representations, and set of cells corresponding to the boundary conditions you created in the conceptual model.  This process is also described in the help section: “Converting Conceptual to Numerical Models

VMOD Flex allows you to generate various numerical models from your conceptual model. You can calculate the difference in heads or drawdown between several model runs.
For more details, see “Compare Heads and Drawdown


Once the numerical model is created, you will see something similar to the examples below:

Figure 4: Property Zones in the Numerical Workflow

Figure 5: Property Zones in a stand-alone 3D Viewer


Figure 6: Boundary Condition (cell representations) in the Numerical Workflow


Translate to MODFLOW Packages

After reviewing the numerical model, you are ready to generate MODFLOW packages that will serve as inputs for the MODFLOW 2000/2005 Run. At the Translation step in the numerical workflow, click on the Translate button.


Make a note of the Output Folder (circled above) for your project. This is where VMOD Flex will generate the MODFLOW files on your hard drive.  These are the files you will need to select when you import into Visual MODFLOW Classic as explained below.


If you are running a flow model, at this point you could proceed to the Run Engines step in VMOD Flex.  For more details, see “Run Numerical Engines

VMOD Classic

Change over to the VMOD Classic interface in order to add and complete the following portions of your project:

Flow Engines: MODFLOW-96

Flow Packages: ETS1, MNW, and/or STR

Transport Engines: MT3D99, PHT3D



Import MODFLOW Files (from VMOD Flex)

VMOD Flex translates the numerical models into standard MODFLOW package files. To migrate your model from VMOD Flex to the VMOD Classic interface, you must import these translated files  into VMOD Classic as described below:

1.Start Visual MODFLOW Classic

2.Select File / Import MODFLOW.

3.Browse to the folder that contains the Translated MODFLOW files from VMOD Flex (the Output Folder circled above)

4.Choose the project_name.MODFLOW.IN file that was generated by VMOD Flex.

5.Enter a name for the Visual MODFLOW project.

6.Follow the Import MODFLOW Wizard; if you need assistance, refer to the Import MODFLOW Files section in the VMOD Classic web help.

After the model is imported, you can review the model inputs in the VMOD Classic Interface.

Figure 7: Property Zone Database in VMOD Classic


Figure 8: Boundary Conditions in VMOD Classic

Add Transport Inputs or Pathlines

Use Visual MODFLOW Classic to add inputs for Transport (or Particles for Pathlines), then translate and run the model.  For more information on these options, refer to the Visual MODFLOW Demo Tutorial or the help documentation.


Web help:

View Results

After running the model in VMOD Classic, with MT3DMS or MODPATH, the results will appear something similar to below:

Figure 9: Pathlines in VMOD Classic


Figure 10: Concentration Contours in VMOD Classic

Export Results

The VMOD Classic interface supports several different export file formats.  Model results from the VMOD Classic interface that are exported as shapefiles or 3D gridded data objects can be easily imported into the VMOD Flex interface for superb 3D display and comparison with initial project conceptualizations and raw data objects.


Once the models are completed in VMOD Classic, you can export the results in several ways.

Concentration contours can be exported as contour lines (File / Export GIS, and choose Contours Shapefile). This must be done on a per layer basis, and for each desired output time.

Pathlines can be exported to .SHP file. (File / Export GIS, and choose Contours Shapefile.)

These files will be imported as Polyline Data Objects in VMOD Flex, as explained in the next section.

3D Gridded Data Objects - Tecplot (.DAT)

Concentration results can also be exported to a TecPLOT .DAT file, which contains concentration values for all cells in all layers.  The benefit of this format is that you can create cross-sections of concentration profiles and also isosurfaces (3D Plumes) in VMOD Flex.

Select File / Export / Data and choose TecPLOT .DAT file format. This must be done for each desired output time.

This file will then be imported as a 3D Gridded Data object in VMOD Flex, as explained below.


Import Results from VMOD Classic

Polylines (Shapefiles)

In VMOD Flex, select File / Import and choose Polyline as the data type. Select the desired pathline or concentration contour polyline shapefiles.  The polylines will not have any elevation attribute. If you wish to position these in a 3D Viewer, you need to define an elevation.  A simple way to do this is through data operations.  Select the desired polyline and load the Settings / Data Operations. Select a desired Z (Elevation) value or select to have the Z value calculated from a surface.  Execute the Data operation and click OK to update the data object. For more details, see “Data Operations” in the web help.

The following figures illustrate the pathlines and contour lines visualized in 3D viewer, after assigning an elevation attribute to each polyline data object.

Figure 11: Pathlines in 3D in VMOD Flex with Pumping Wells and Horizons visible


Figure 12: Concentration Contours as Polylines in VMOD Flex, with Boundary Condition cells and Lower Aquifer Property Zone visible


Polyline data objects may also be added on the Layer view of the Numerical model, as shown below.


Figure 13: Concentration contours shown in Layer 1


Concentrations as 3D Gridded Data Object (TecPlot .DAT)

The Concentration results from VMOD Classic can also be imported as a 3D Gridded Data objects; this format provides a richer set of visualization options, such as 3D Isosurface, colormap along specific row, column, or layer, or arbitrary cross-section line.  In order to use this option, you must export your concentration results to a TecPot .DAT file as explained above.

Select File / Import and choose 3D Gridded Data as the object type.  Select the .DAT file that was generated from VMOD Classic and proceed through the default import settings.  After the file is imported, visualize in a 3D Viewer.  Refer to “Style Settings – 3D Gridded Data” in the webhelp for assistance in setting up color maps or isosurfaces.


Figure 14: Concentrations as 3D Grid, rendered as an Isosurface; Fence Diagrams represent the conductivity zones



Figure 15: Concentrations imported as 3D Gridded Data, Rendered as a Colormap with Isolines along Row 39

For More Information

If you require assistance during importing of models into VMOD Classic, or the results back into VMOD Flex, please contact our Tech Support team:


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