By default, the entire geographic extent of the created water quality geometry is contained within a single region, known as the Default Region (as shown in the Geometry Editor – Regions Tab). This default region can be modified using the Water Quality Extent and Regions tool in the ResSim main window. It's important to note that all elements within the geometry's extent must be assigned to a region. If an element is not assigned to a user-created region, it will be included in the "Default Region."

To modify the number of regions and assign elements to specific regions within the geometry dataset:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar.
  2. Use the tool to modify regions by clicking and holding the left mouse button, then dragging a polygon around the network elements you wish to include in a new region. Release the mouse to select the elements within the polygon. The selected elements will be highlighted in yellow.
  3. If additional elements were missed by the polygon, hold the Shift key and left-click on the elements in the map window to add them to the selection.

To create a new region for the selected geometry elements, right-click on the selected elements. A shortcut menu will appear. From the menu, select Create under the Region option (refer to HEC-ResSim Main Window – Regions Shortcut Menu Options). This process will allow users to create new regions for the geometry and assign elements to specific regions, enhancing the flexibility and accuracy of water quality modeling.



HEC-ResSim Main Window – Regions Shortcut Menu Options

If the selected elements do not belong to a user-created region, the Create New Region dialog box will open (see Edit Regions – Create New Region Dialog Box). However, if a selected network element is already part of an existing region, the Network Elements in Existing Region message dialog will appear (see Network Elements in Existing Region Message Dialog). This situation does not apply to elements in the Default Region—it only occurs when an element is part of a user-created region.

In the Network Elements in Existing Region message dialog, you have the following options:

  • Click Yes to move the identified elements to the new region. The Network Elements in Existing Region dialog will close, and the Create New Region dialog box will open.
  • Click No to create the new region without including the listed elements. The Network Elements in Existing Region dialog will close, and the Create New Region dialog box will open.
  • Click Cancel to close the Network Elements in Existing Region dialog without creating the new region.

This process ensures that users can manage and assign elements to appropriate regions effectively, while maintaining control over their geometry dataset structure.


Edit Regions – Create New Region Dialog Box


Network Elements in Existing Region Message Dialog

In the Create New Region dialog box, follow these steps to define a new region: Enter a unique name for the region in the Name field. Optionally, enter a description for the region in the Description field. While this is optional, it is recommended for better organization and clarity. The elements selected in the map window schematic are automatically added to the Selected Elements box.

To modify the selected elements for the new region:

  • To add more elements to the region, select the desired elements from the Available Elements box and click Add. The selected elements will be moved to the Selected Elements box.
  • To remove elements from the region, select the element(s) in the Selected Elements box and click Remove. The elements will be removed from both the Selected Elements box and the new region.

Once all elements have been assigned and the region is properly defined, click OK to confirm. The Create New Region dialog box will close, and the new region will be displayed in the map window schematic with a distinct color scheme. By default, a specific color scheme is assigned to new regions, but the user can modify these colors via the Water Quality Draw Properties dialog to better distinguish between regions as needed.


Example – HEC-ResSim Main Window – Regions Color-Scheme

If the name entered in the Name field already exists, a Warning message dialog will appear, indicating that the region name is not unique. To resolve this:

  1. Click OK to close the Warning message dialog.
  2. Enter a unique name for the region in the Create New Region dialog (Warning Message Dialog – Enter Unique Region Name).

Once a unique name is entered, proceed with the steps to define and create the new water quality region.


 Warning Message Dialog – Enter Unique Region Name

Proceed by creating additional regions, reviewing the report for an existing region, renaming a region, adding or removing network elements from a region, or deleting a region as necessary.

View the Region Report


To view the reports for existing regions:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar. When the tool is active, the mouse pointer will change accordingly.

  2. In the map schematic, right-click on a created region. This will open the WQ Extent/Regions tool's shortcut menu. From the menu, under the Region option, click View Report.

  3. The Geometry Editor will open to the Regions tab (Geometry Editor – Regions Tab – Example – View the Region Report). The number of columns in the Regions tab will correspond to the number of created regions. Each region will list the network elements contained within it, displayed in hydrologic order. A tooltip will show the count of elements within the selected region (e.g., the Default Region contains 15 elements, as displayed).

  4. Click OK to close the Geometry Editor and return to the ResSim main window.


Geometry Editor – Regions Tab – Example – View the Region Report

Rename a Region

To rename an existing region:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar. With the tool active, the mouse pointer will change accordingly.

  2. In the map schematic, right-click on a created region. The WQ Extent/Regions tool's shortcut menu will open. From the menu, under Region, click Rename.

  3. The Rename Region dialog box (Rename Region) will open. From the Old Region Name dropdown list, select the region you wish to rename (e.g., Region1).

  4. Enter a new name for the selected region in the New Region Name field. Optionally, provide a description in the Description box (this is recommended, but not required).

  5. Click OK to close the Rename Region dialog and apply the new name to the selected region.

If the name entered in the New Region Name field already exists, a Warning message dialog will appear. Click OK to close the warning message, then enter a unique name in the Rename Region dialog. Finally, click OK again to rename the region.



Rename Region

To rename additional regions, repeat the above steps:

Add a Network Element to a Region

To add network elements that are currently in the Default Region to a user-defined region, follow these steps:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar.

  2. In the map schematic, right-click on the network element you want to add to a region. If you want to select multiple elements, hold down the Shift key while left-clicking to select additional elements, then right-click.

  3. The WQ Extent/Regions tool's shortcut menu will appear. From the menu, under Region, click Add to.

  4. The Add To Region dialog box (Add To Region Dialog Box – Selected Elements in Default Region) will open, displaying the selected elements in the Selected Elements list (e.g., Healdsburg Gage to Dry Creek Conf). These elements are listed as part of the Default Region.

  5. From the Selected Region dropdown list, choose the user-defined region to which you want to add the selected elements.

  6. Click OK to confirm the addition. The selected network elements will now be part of the chosen user-defined region.

This process ensures that the network elements, which were originally part of the Default Region, are now properly added to the desired region.



Add To Region Dialog Box – Selected Elements in Default Region

Click OK to close the Add To Region dialog, and the selected network element will be added to the chosen region. To add any additional elements from the Default Region to a user-created region, repeat the above steps as needed.

To add one or more network elements that belong to an existing user-created region to another user-created region, follow these steps:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar.

  2. In the map schematic, right-click on the network element(s) you want to move. If you wish to select multiple elements, hold down the Shift key while left-clicking to select additional elements, then right-click to open the WQ Extent/Regions tool's shortcut menu.

  3. From the shortcut menu, under Region, click Add to.

  4. Since the selected element(s) are already part of a user-created region, the Network Elements in Existing Region message dialog will appear.

    • Click Yes to move the identified elements to a different user-created region. This will close the Network Elements in Existing Region message dialog and open the Add To Region dialog box.
    • In the Add To Region dialog, the Selected Elements (e.g., Healdsburg Gage to Dry Creek Conf ) list will contain only the elements selected in the map schematic. From the Selected Region dropdown list, select the region to which you want to move the elements.
    • Click OK to confirm the change. The selected network elements will be moved to the new user-created region.

  5. Alternatively, if you do not wish to move the elements, click No. This will keep the elements in the original user-created region. The Network Elements in Existing Region message dialog will close, and the Add To Region dialog box will open. The Available Elements (e.g., Healdsburg Gage to Dry Creek Conf) list will display only the elements you initially selected. Click OK, and the elements will remain in their original region.

  6. If you want to cancel the operation, click Cancel to close the Network Elements in Existing Region message dialog without making any changes.

To add additional elements to user-created regions, repeat the above steps as necessary.

Note: The Add to option in the WQ Extent/Regions tool's shortcut menu allows users to move elements either from the Default Region or from a user-created region to another user-created region. To add an element from a user-created region to the Default Region, the Remove from option in the shortcut menu must be used (see the next section for further instructions).

Remove a Network Element from a Region

To remove network elements from a user-created region and move them to the default region:

  1. From the ResSim main window, select the Water Quality Extent and Regions (WQ Extent/Regions) tool from the Toolbar.
  2. In the map schematic, right-click on the element you want to remove (or left-click to select multiple elements while holding the Shift key, then right-click), and the WQ Extent/Regions tool's shortcut menu will appear.
  3. From the shortcut menu, under Region, click Remove from.

The Remove From Region dialog box (Remove From Region Dialog Box – Selected Elements in Region2) will open. The network elements you selected in the map window will automatically populate the Selected Elements list (e.g., Healdsburg Gage to Dry Creek Conf). Any network elements in the Selected Elements list will be removed from the selected user-created region (e.g., Region2). The Available Elements box will display the list of elements in the selected region.



Remove From Region Dialog Box – Selected Elements in Region2

To remove additional elements from a user-created region and move them to the default region:

  1. In the Remove From Region dialog box, from the Available Elements box, select the elements you want to remove. You can select them individually or select multiple elements by holding down the Ctrl key while clicking on them.

  2. After selecting the desired elements, click the Add button to add them to the Selected Elements list.

  3. Once all the desired network elements have been added to the Selected Elements list, click OK. The Remove From Region dialog box will close, and the selected elements will be moved back to the default region.

  4. To remove additional elements from user-created regions, repeat these steps as needed.

Delete an Existing Region

To delete a user-created region and move all network elements in the region to the default region:

  1. From the ResSim main window, in the Toolbar, select the Water Quality Extent and Regions (WQ Extent/Regions) tool.

  2. In the map schematic, right-click on an element that belongs to the user-created region you wish to delete. This will open the WQ Extent/Regions tool's shortcut menu.

  3. From the shortcut menu, under Region, click Delete.

  4. The Delete Region dialog box (Delete Region Dialog Box) will appear, confirming that the selected region will be deleted and all its network elements will be moved to the default region.


Delete Region Dialog Box

To delete a user-created region and move its network elements to the default region:

  1. From the Delete Region dialog box, in the Select Region to Delete dropdown, select the user-created region you wish to delete.

  2. After selecting the region, click OK.

  3. The Delete Region dialog box will close, and all network elements from the deleted region will be moved to the default region.

  4. If any of the selected elements are part of the region, you will be prompted with a Delete Region dialog, allowing you to choose which region to delete.

The process will complete when the selected region is deleted, and its elements will now reside in the default region.