Version 4.1 (April 2026) of the Reservoir System Simulation program (HEC-ResSim) is now available. This version supersedes Version 4.0 which was released to the general public in October 2025.
Some enhancements to existing features have been added to the software in Version 4.1. The new features to look for are listed in the Version 4.1 Release Notes.
Please refer to the HEC-ResSim User’s Manual for details regarding the new features, enhancements, and improvements.
We strongly recommend that
before you start using
HEC-ResSim 4.1 you
make backup copies of your existing watersheds (and consider using separate modeling locations (folders) for your v4.1 and v4.0 watersheds).