Downstream HGL Puzzle

Dear Swmmers:

Working on a modeling scenario where some upstream pipe changes are made in a proposed file comparing to an existing conditions file.

The files when run with SWMM Version 4.4H result in a tremendously large difference in the water surface elevations in the beginning (downstream) nodes when in fact the only changes are well upstream (3,000 feet away).

Any ideas about the cause of this downstream HGL discrepancy will be appreciated.

Thank you
Dan Saunders
City of St. Petersburg, Fl

Dan - Its hard to suggest anything based on the info you supplied. Suggest you attach your input files so other list members can run them and then offer advice. My offhand guess is that there may be a geometry rule violation somewhere in between, perhaps an open channel exceeding capacity.

Ron Kilmartin

Dan,

Along with Ron's suggestion you might want to check to see if you are using a valid Hot-Restart file. If you are using a new version of SWMM the older hot- restart file may not be valid for SWMM44h. If a bad initial depth or flow is read this may explain the large initial head differences you mention.

Best Regards,
Robert Dickinson
dickinsonre@cdm.com