MODFLOW-USG Regional to Local Workflow

To create a local refined area in a regional MODFLOW-USG model, use the following steps:

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

2. Create a UGrid.

1. Create a new UGrid. 1. Create a new 3D UGrid. Right-click in the Project Explorer and select New | UGrid 3D.... In the New UGrid dialog, enter the information for the X-, Y-, and Z-Dimension of the grid. 2. Create a new 2D UGrid. Right-click in the Project Explorer and select New | UGrid 2D.... In the New UGrid dialog, enter the information for the X- and Y-Dimension of the grid. 3. Create a UGrid using a grid frame. Right-click in the Project Explorer and select the New | Grid Frame... command. Using the Select Grid Frame tool, right-click on the grid and select the Fit to Active Coverage command. Select the Feature Objects | Map → UGrid... menu command. In the Map → UGrid dialog, enter parameters for the UGrid. This includes complex stratigraphy such as: Quadtree UGrids Voronoi UGrids VTK Unstructured Grids 2. Convert an object into a UGrid. 1. Convert a 3D grid to a 3D UGrid. Right-click in the 3D grid item in the Project Explorer and select Convert To | UGrid.... 2. Convert a shapefile to a UGrid. Right-click in the shapefile item in the Project Explorer and select Convert To | UGrid.... To convert the new 2D UGrid into a 3D UGrid: Right-click on the 2D UGrid item and select the Extrude Down to 3D UGrid command. Enter 3D parameters in the Thickness dialog. 3. Convert map layers to a UGrid. Right-click in the Project Explorer and select the New | Grid Frame... command. Using the Select Grid Frame tool, right-click on the grid and select the Fit to Active Coverage command. Select the Feature Objects | Map → UGrid... menu command. In the Map → UGrid dialog, enter parameters for the UGrid. 4. Convert horizon to a UGrid. Select the TINs | Horizons → UGrid... menu command. Use the Horizons to UGrid wizard to generate the UGrid.

3. Define a refined area.

1. Create or edit an coverage with the Refinement option turned on. 1. Create new coverage from scratch. Use the New Coverage right-click command. Use the Coverage Setup dialog to create a new coverage by selecting the desired coverage properties and naming the coverage. 2. Create new coverage from an existing coverage. Use the Duplicate command on an existing coverage. This will copy any feature objects on the coverage. Use the Rename command to give the coverage a new name. Change the coverage setup. 2. Create a polygon around the local site. 1. Create enclosed arcs for polygon areas. 1. Create feature points, arcs, nodes and vertices. In the map module, create feature objects in the active coverage. Use the Create Arc tool to create arcs in the map coverage. Begin creating a new arc by clicking in the graphics window at either arc end. If clicking on an existing feature node, vertex or arc, the new arc will snap to that object. Double-click or press the Enter key to terminate the arc. Use the Create Point tool to create additional nodes alone or to split arcs. 2. Modify arcs. Feature arcs, whether digitized or incorporated from a boundary condition or a material coverage, often need to be edited after initial creation. 1. Create additional vertices on arcs. Use the Create Vertex tool to add vertices along arcs. 2. Refine the arc shape. Use the Select Vertices tool and the Select Points\Nodes tool to move/edit existing arcs and refine the shape by dragging the nodes/vertices. Use the Select Arcs tool to move entire arcs . 3. Split arcs. An existing arc can be split by: 1. Converting a vertex to a node. Use the Select Vertices tool. Select the Feature Objects | Vertices → Nodes command to split the arc into two arcs. 2. Add a node to the arc. Use the Create Point tool to add a node on an arc in order to split it into two arcs. 3. Connect the end of an existing arc to the middle of the arc. Use the Select Points\Nodes tool to drag the node of an existing arc to anywhere in the middle of another arc. This will split the second arc into two arcs. 4. Add a new connecting arc. Use the Create Arc tool to start or end a new arc on an existing arc to split the existing arc into two arcs. 5. Split overlapping arcs using the Clean Options dialog. Select overlapping arcs using the Select Arcs tool. Use the Feature Objects | Clean command to bring up the Clean Options dialog. Select the Intersect selected arcs option (for selected arcs) or Intersect arcs option (for all overlapping arcs) to split the arcs. 4. Merge arcs. Two arcs that share an end node can be merged together. Select the shared node using the Select Points\Nodes tool. Click on the Feature Objects | Nodes → Vertices menu command to merge the arcs. If desired, the Select Vertices tool can be used to select and delete the new vertex. 5. Transform arcs. Select the arc using the Select Arcs tool. Use the Edit | Transform command. Use the Transform dialog to scale, translate or rotate the arc. 2. Build polygons in enclosed areas. Polygons are not created automatically when arcs are enclosed. To create polygons: Use the Feature Objects | Build Polygons command. 3. Define refinement attributes for the polygon. Using the Select Polygon tool, double-click on the refinement polygon. Assign refinement properties in the Attributes Table dialog. 4. Create a 3D refined UGrid. Right-click on the grid frame item in the Project Explorer and select Map to | UGrid command. Enter parameters for the refined grid into the Map→UGrid dialog.

4. Convert layer data to a scatter point set.
Convert layer data from the existing MODFLOW model to a scatter set. Select the Grid | MODFLOW Layers → 2D Scatter Points… command. Use the MODFLOW Layers → Scatter Points dialog.

5. Create a MODFLOW-USG model.
Right-click on the UGrid item in the Project Explorer and select the New MODFLOW command. Set options in the MODFLOW Global/Basic Package dialog.

6. Interpolate layer elevations.
In the Project Explorer, right-click on the scatter point set and select Interpolate To | MODFLOW Layers. Set interpolation options in the Interpolate to MODFLOW Layers dialog.

7. Map to MODFLOW.
Select the conceptual model . Select Feature Objects | Map → MODFLOW . Select the appropriate options in the Map → Model dialog.

8. Run MODFLOW.
Save the project. Run MODFLOW .