Latest Guidance on ResSim 4.0 for CWMS Users

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Since ResSim 4.0 is markedly different than ResSim 3.5, ResSim 4.0 is not compatible with versions of RTS that use ResSim 3.5 and earlier (e.g., RTS 3.5).

RTS 3.6 will be the first version of CWMS that is compatible with ResSim 4.0.  For CWMS users who would like to try ResSim 4.0, our recommendations are:

  • Use the ResSim 4.0 as a standalone product, especially for testing out Water Quality.  Do not attempt to drop it into RTS 3.5.
  • Request to get on the waitlist to be a RTS 3.6 Beta tester, which will allow you to test with ResSim 4.0,


Many HEC-ResSim users work with ResSim through their real time modeling using the Corps Water Management System (CWMS) or on planning studies through the Watershed Analysis Tool (HEC-WAT). 

The ResSim Variants information will be of particular interest to you. 

For CWMS users, also see:

  • General Best practices related to CWMS: Best Practices
  • CWMS Release Notes can be found here CWMS Release
    • CWMS v3.6 will be the first official CWMS that integrates ResSim 4.0 and later ResSim versions. Earlier versions of CWMS will not work with ResSim 4.0. 
  • The CWMS user documentation in general: CWMS/HEC-RTS Documentation.

HEC-WAT documentation can be found here: HEC-WAT Documentation.