GMS:MODFLOW 6 MDT Package Workflow

To use the Matrix Diffusion Transport (MDT) package in an existing MODFLOW 6 project, use the following processes:

1. Begin with an existing MODFLOW 6 project.
The existing MODFLOW 6 model can be created using the conceptual model or grid based approach.

2. Add a GWT model to the simulation.

The MDT Package is only available as part of a GWT model in MODFLOW 6. If necessary, follow these steps to add a GWT model to the MODFLOW 6 simulation: 1. Begin with an existing MODFLOW 6 project. 2. Create the transport model. Right-click on the MODFLOW 6 simulation and select New Package | GWT. In the New Groundwater Transport (GWT) Model dialog, select the UGrid to use and any optional packages. 3. Modify package inputs for each desired package. Right-click on the package in the Project Explorer and select the Open command. Modify the inputs in the package dialog. 4. Set up the GWF-GWT exchange. Right-click on the MODFLOW 6 simulation and select New package | GWF-GWT. Right-click on the MODFLOW 6 simulation and select Open to open the Simulation Options dialog. In the EXCHANGES section, click the boxes under the columns EXGMNAMEA and EXGMNAMEB to specify which models the exchange is connecting. 5. Set up the IMS solver package for the transport model. Often, an additional IMS solver package is desirable for the GWT model. To create it: 1. Create the IMS solver package. Right-click on the MODFLOW 6 simulation and select the New Package | IMS command. If needed, give it a new name to differentiate it from any other IMS solver packages. 2. Define the settings of the IMS solver package. Right-click on the package in the Project Explorer and select the Open command. Modify the inputs in the package dialog. These inputs include: COMPLEXITY Options under the NONLINEAR section. Options under the LINEAR section. 3. Specify which model the IMS solver package corresponds to. Double-click on the MODFLOW 6 simulation to open the Simulation Options dialog. In the SOLUTIONGROUPS section, click the boxes under the SLNMNAMES section to select which model corresponds to each IMS solver package.

3. Add the MDT package to the simulation.
Right-click on the GWT model and select New Package, then select the desired package from the list.

4. Modify MDT package inputs.
Right-click on the package in the Project Explorer and select the Open command. Modify the inputs in the package dialog.