GMS:MODFLOW LAK Package Workflow

To use the Lake (LAK) package in an existing MODFLOW project, use the following processes:

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

2. Activate the Lake packages.
Select MODFLOW | Global Options. In the MODFLOW Global/Basic Package dialog, select the Packages button. In the MODFLOW Packages/Processes dialog, select the LAK3 – Lake option.

3. Create the Lake coverage.

1. Create a new coverage with the Lake 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 polygon defining the lake area. 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.

4. Set up a Lake TIN.

An elevation will need to be assigned to the lake polygon using a TIN. If a TIN is not already available, use the following: 1. Create a TIN. Select the Feature Objects | Map → TIN menu command. Set TIN parameters in the Properties dialog. 2. Interpolate elevations to TIN. 1. Set interpolation options Select the Interpolation | Interpolation Options menu command. In the 2D Interpolation Options dialog select the interpolation method and options. 2D interpolation methods include the following: Linear Inverse distance weighted Clough-Tocher Natural neighbor Kriging 2. Interpolate to a TIN. Select the target TIN in the Project Explorer to make it active. Select the Interplation | Interpolate→Active TIN menu command. Set the dataset name and review interpolation options in the Interpolate→Object dialog.

5. Assign Lake polygon properties.
Double-click on the lake polygon using the Select Polygon tool. Assign polygon properties in the Attribute Table dialog.

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

7. Assign Lake package properties.
Select the MODFLOW | Optional Packaged | LAK – Lake Package menu command. Assign package properties in the MODFLOW Lake Package dialog.

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