SWMM 5.1 Update History
Engine Updates, more information and code shown on the EPA Website:
1. A new feature that provides monthly adjustments for
temperature, evaporation rate, and rainfall was added.
2. Support for reading the new GHCN-Daily climate data
files available from NCDC’s Climate Data Online service
3. In addition to lateral groundwater flow, a custom
equation can now also be used for seepage flow to
a deeper groundwater aquifer.
4. The [GW_FLOW] section of the project file was renamed
to [GWF] and its format was changed to accommodate
both lateral and deep groundwater flow equations.
5. A new Weir parameter was added that specifies if the
weir can surcharge using an orifice equation or not.
Surcharging was the only option in SWMM 5.0 but was
switched to no surcharging in earlier 5.1 releases.
This new parameter accommodates both closed top weirs
that can surcharge and open channel weirs that cannot.
6. The formula used to recover infiltration capacity during
dry periods for the Modified Horton method was revised.
7. The initial cumulative infiltration into the upper soil
zone for Green-Ampt infiltration had been incorrectly
set to the maximum value instead of zero.
8. All of the Green-Ampt infiltration functions were
re-factored to make the code easier to follow.
9. The calculation of infiltration out of the bottom of a
Bio-Retention Cell or Permeable Pavement LID unit with a
zero-depth storage layer was corrected.
10. Most of the LID simulation routines were modified to
provide more accurate results under flooded conditions.
11. Results written to the detailed LID results report now
always correspond to a full reporting time step.
12. The name of the variable used to represent the height of
the receiving channel bottom in a user-defined groundwater
flow equation was corrected to match the name displayed
in the GUI’s Groundwater Editor dialog (Hcb).
13. A problem with the program crashing when a climate file
was used to provide evaporation rates for open channels
and storage nodes when runoff was not computed (as when
there were no subcatchments in the project) was fixed.
14. Flow and pollutant routing mass balance accounting was
modified to correctly handle negative external inflows.
15. The procedure for computing the area available for seepage
out of a storage node that has a tabular storage curve was
16. Seepage from storage units can now be modeled using Green-
Ampt infiltration, which makes the seepage rate a function
of storage level. The constant seepage rate option can
still be used by setting the G-A initial moisture deficit
17. The function that finds depth as a function of volume from
a storage curve was corrected for the case where the depth
falls within a portion of the curve where area is constant
with depth (i.e., vertical side walls).
1. The Object Toolbar was restored.
2. A new page was added to the Climatology Editor to edit
values for monthly adjustments for temperature, evaporation,
3. A field for the new weir surcharge option was added to the
Weir Property editor.
4. A problem with the current project being closed without
asking if it should be saved first whenever a new style
theme was selected from the Program Preferences dialog
has been fixed.
5. The default seepage rate from an LID storage layer was changed.
6. The Infiltration Editor was restored for editing Green-Ampt
parameters for storage unit seepage loss.
7. The Groundwater Flow Equation Editor was extended to accept
equations for deep groundwater flow.
History of EPA SWMM versions (from Wikipedia)