Data is exchanged between models in an HEC-RTS forecast using a DSS file and with pathnames that contain an F-part that identify the model and scenario (alternative). Each individual model or model input/output is called an Alternative. An alternative may be different reservoir operations, or a different forecast for precipitation, or different loss or routing parameters. For example, typically in an HEC-RTS study, there might be at least three (future) precipitation alternatives - No Future Precipitation, QPF, User Specified.
Each model alternative is assigned an alpha-numeric character, or "key", that identifies the alternative. Different models may use the same character (e.g., B for base HMS and B for a ResSim alternative.) The model alternative keys are concatenated together to form a "Run Key", which is used in the F-part of a DSS pathname to identify the dataset.
For example, for a QPF alternative for MFP, which combines observed precipitation and future precipitation, the MFP alternative would be assigned the letter "Q". The HEC-HMS model needs the precipitation from the MFP alternative to generate flows, both observed and forecasted. So, HEC-HMS would look for pathnames with an F-part of "Q". The HEC-HMS model was calibrated for wet conditions, so the HEC-HMS alternative might be assigned the letter "W". The HEC-ResSim needs the HEC-HMS flows, so HEC-ResSim would be looking for pathnames with an F-part of "QW". The HEC-ResSim model is a standard operation model which means the assignment might be the key "S". HEC-RAS model needs the flows out of the reservoir, so HEC-RAS would be looking for pathnames with an F-part of "QWS". HEC-RAS then compute stages and writes those stages out to pathnames with an F-part of "QWSB" (the HEC-RAS model having a key of "B"). In turn, the HEC-FIA model would need the stages from the HEC-RAS model and would be looking for pathnames with an F-part of "QWSB".
Reports, output, log files, etc. all use this convention to identify the complete dataset that they represent. In short, if a "%" represents a model, then log files and the F-parts of the DSS pathnames used will be:

  • %- output from MFP
  • %%- output from HEC-HMS
  • %%%- output from HEC-ResSim
  • %%%%- output from HEC-RAS
  • %%%%%- output from HEC-FIA

The user can use these percent signs in the model interface module to identify datasets, especially in time series icons to identify what DSS datasets to use. Currently, a "trial" number

  1. is internally appended to each ID key and will appear in the F-part. Trials in HEC-RTS will not be addressed at this time.