To add mass injection sites for a reach, reservoir, or junction in an ResSim watershed:

  1. From the ResSim main window, navigate to the Water Quality module. The data panel in the module will allow you to select and view specific created water quality datasets on the map schematic.

  2. In the Toolbar, select the Mass Injection tool . When selected, the mouse pointer will change to a different icon in the map window.

  3. In the map window schematic, at the location where you want to add the mass injection site, hold the Ctrl key and left-click to place the mass injection site. This will open the Name New Mass Injection Site dialog box (Name New Mass Injection Site Dialog Box).

  4. In the Name New Mass Injection Site dialog box, enter a name for the mass injection site in the Name field. Optionally, enter a description in the Description field, though it is recommended for clarity.

  5. Click OK to close the dialog and add the new mass injection site (HEC-ResSim Main Window – Water Quality Module – Mass Injection Sites).



Name New Mass Injection Site Dialog Box


HEC-ResSim Main Window – Water Quality Module – Mass Injection Sites

The Name New Mass Injection Site dialog also ensures that the mass injection site name is unique. If the name already exists when the OK button is clicked, a Duplicate Name message will appear, informing the user that the name must be unique. To resolve this:

  1. In the Duplicate Name message dialog, click OK.
  2. In the Name New Mass Injection Site dialog, enter a unique name in the Name field and click OK. The dialog will close, and the newly created mass injection site will be added to the map window schematic (HEC-ResSim Main Window – Water Quality Module – Mass Injection Sites).

When the Mass Injection tool is used to place a mass injection site on a reach or reservoir, the site will snap to the closest stream alignment. However, if there are multiple stream alignment components at the selected location, the Name New Mass Injection Site dialog will prompt the user to choose the appropriate location from a dropdown list titled Select the placement of the Mass Injection Site (Name New Mass Injection Site – Select placement of Mass Injection Site). To proceed:

  1. From the dropdown list, select the correct location for the mass injection site.
  2. Click OK to finalize the selection and place the mass injection site.



Name New Mass Injection Site – Select placement of Mass Injection Site

The available shortcut menu commands vary depending on two factors: (1) whether a Mass Injection Dataset is open in the map window schematic, and (2) whether the selected site is active in the chosen Mass Injection Set (e.g., MassI_MendocinoOUT in HEC-ResSim Main Window – Mass Injection Shortcut Menu Commands).

For example, in the provided scenario, the MIS_1 mass injection site is active within the Mass Injection Dataset, while MassI_MendocinoOUT remains inactive.

The following list outlines all possible shortcut commands:

Rename Mass Injection Site

This option enables users to rename the selected mass injection site.

Delete Mass Injection Site

This option enables the users to delete the selected mass injection site.

Add {Mass Injection Site Name} to {Mass Injection Dataset}

This option allows the user to add a mass injection site, which is not currently active in the selected mass injection dataset, to the open mass injection dataset. 

Edit Mass Injection Site

This option opens the selected mass injection site within the mass injection dataset in the Mass Injection Set Editor, allowing for further modifications or review. 



HEC-ResSim Main Window – Mass Injection Shortcut Menu Commands

Users can move a mass injection site within the map schematic. To do this, select the Mass Injection tool and double-click on the site. The icon will turn yellow, and four black dots will appear around it, indicating that the site is in the "Move" state. To reposition the site, click and hold the mouse button while dragging the icon to the desired location on the screen (Moving a Mass Injection Site).
Moving a Mass Injection Site