The
SWMM 5 data input files are not backwards compatible with previous versions of SWMM - you cannot open a file created in v13 with a v11 GUI without getting messages about Options or features present in v13 but not present in v11. Not everyone looks at the C code but the new options are listed in the file enums.h with a version notation:
SKIP_STEADY_STATE, TEMPDIR, IGNORE_RAINFALL, //(5.0.010 - LR)
FORCE_MAIN_EQN, LINK_OFFSETS, //(5.0.012 - LR)
The good feature about this message is that it tells you what MAY be different between the two SWMM versions. For example, if you used Link Offsets in v13 then you will not have a valid model in SWMM 5.0.011. However, if you are not using a new option in SWMM 5.0.013 then you will have a valid backwards compatible SWMM 5.0.011 input data set.
This version is a QA/QC version of SWMM 5 that was used to more closely compare the SWMM 4 to SWMM 5 results using extra data variables.
It should not be used for modeling. You should use the EPA SWMM Web site to download the latest EPA SWMM version:
http://www.epa.gov/ednnrmrl/models/swmm/index.htm