After creating a forecast run, you need to link the model alternatives so each model can receive the necessary input data - either from the Extract List or from other models within the forecast.

For example, a forecast run might include HEC-MetVue, HEC-HMS, and HEC-ResSim model alternatives:

  • HEC-MetVue requires gridded data extracted from a source, such as your local database or Cumulus (for USACE modelers).
  • HEC-HMS uses output from the HEC-MetVue model alternative.
  • HEC-ResSim depends on output from HEC-HMS and observed time series data extracted from a database.

Model Linking Editor

You can establish these data connections using the Model Linking Editor.

You can open the Model Linking Editor from two locations:

  • Setup tab - Use this to edit model linking for the Base Forecast Run.
  • Modeling tab - Use this to edit model linking for the Active Forecast's Model Alternatives. 
The title bar of the editor indicates which mode you're in: If it shows <Base Data>, you're in the Setup tab. If it shows a forecast name (e.g., 2025.05.09-1600 GMT), you're in the Modeling tab.

Selecting a Forecast Run

At the top of the Model Linking Editor, use the drop-down list to select the forecast run you want to edit. Once selected, the Model Requiring Input list shows the model alternatives included in that forecast run. To complete linking, step through each model alternative listed.

Understanding the Model Linking Table

The lower portion of the editor contains a table that defines the inputs required by the selected model alternative and their sources.

This table has four columns: 

  • Location - Name of the input required. For example, this could be:
    • The precipitation grid name or discharge gage name specified in the HEC-HMS model alternative.
    • The local flow name specified in the HEC-ResSim model alternative.
    • The river station and node name specified in the HEC-RAS model alternative.
  • Parameter - Type of data needed (e.g., flow, stage, precipitation).
  • Input From - Source of the input. Options include:
    • Other model alternatives from the selected forecast run.
    • The Extract List, which pulls data from external sources (e.g., CWMS database, HEC-DSS files, Cumulus, CDA).
  • Location/Parameter - Specifies the actual data source.
    • If Input From is a model alternative, this column lists that model’s results.
    • If Input From is Extract List, this column displays an HEC-DSS pathname from the forecast.dss file.

Get Linkages From

Use the Get Linkages from... button to import model linkages from existing model linkages or an existing forecast run. 

Select Input Model Alternative

Use the Select Input Model Alternative tool to set a single input source for all rows not currently linked to the desired input. 

Select Source Data Location

Select a row from the table and click the Browse button to open the Select Source Data Location dialog. This dialog lets you view all locations and parameters available from the source - in the example shown below the HEC-HMS model alternative named HMS-Summer is the source.

Model I/O

Click the Model I/O button to view model inputs and outputs for each alternative in the forecast run.

Save Linkages to Model

Clicking the Save Linkages to Model button saves the model linkages to model-specific linking files (e.g., a .dsv file in the HEC-HMS project directory). In contrast, clicking Apply or OK in the Model Linking Editor saves the linkages to an HEC-RTS specific file located in the cavi/modelLinking folder within the watershed directory.

Additional Resources

Refer to this guide for step-by-step instructions on configuring model linking within HEC-RTS.