HEC-ResSim 3.5.1 is included with HEC-WAT 1.1.  HEC-ResSim 4.0/4.1 is supported within HEC-WAT by changing out the HEC-ResSim Plugin files used.  Please contact the HEC-WAT or HEC-ResSim team for additional information if this is needed.  The HEC-ResSim 3.5.1 users manual should be consulted for additional information about the HEC-ResSim software.