Subject:  SWMM 5 Engine Updates between v13 and v22 by Category

The complete list of engine and GUI changes can be found in this text file on the EPA Site http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/epaswmm5_updates.txt

This note  categorizes the engine changes by aggregating dynamic wave solution changes, surface ponding changes, RDII and Hydrology for example.  The number preceding each change is the change number per engine update – the version of the engine update is shown at the end of each change paragraph.  The Categories are General Changes, Dynamic Wave Changes, RDII Changes, Infiltration and Surface Runoff Changes, Climate Data Changes, Rainfall  Changes, LID Changes and Water Quality Changes.

General Changes

6.  The maximum trials used when evaluating the flow and head equations at

    a given time period for dynamic wave routing was increased from 4 to 8.

    See dynwave.c.   Build 5.0.019 (07/30/10)

28. For models that only compute runoff and have a reporting time step

    less than the wet time step, the latter is internally set equal to

    the former. See swmm5.c.  Build 5.0.019 (07/30/10)

1.  Reporting of the total infiltration + evaporation loss for each

    Storage Unit (as a percent of total inflow to the unit) was added

    to the Storage Volume Summary table in the Status Report. See

    objects.h, node.c, stats.c, and statsrpt.c.   Build 5.0.018 (11/18/09)

2.  Double counting the final stored volume when finding the nodes with

    the highest mass balance errors has been eliminated. See stats.c.

    Build 5.0.018 (11/18/09)

4.  Hot Start interface files now contain the final state of each

    subcatchment’s groundwater zone in addition to the node and

    link information they have always had. See routing.c.  Build 5.0.018 (11/18/09)

5.  To avoid confusion, the actual conduit slope is now listed in the

    Link Summary table of the Status Report rather than the adjusted

    slope that results from any conduit lengthening. See link.c and

    dynwave.c. Build 5.0.018 (11/18/09)

6.  The Status Report now displays only those summary tables for

    which results have been obtained (e.g., if the Flow Routing

    option is turned off, then no node or link tables are displayed).

    See massbal.c and statsrpt.c. Build 5.0.018 (11/18/09)

7.  Some code re-factoring was done to place rain gage validation

    and initialization in separate functions. See project.c, gage.c,

    and funcs.h. Build 5.0.018 (11/18/09)

8.  The engine version number was updated to 50018 (this update had

    been overlooked since release 5.0.010). See consts.h. Build 5.0.018 (11/18/09)

2.  Error 112 (a conduit’s elevation drop exceeds its length)

    is now treated as a Warning condition and not a fatal error.

    In this case the conduit’s slope is computed as in earlier

    versions of SWMM (elevation drop / length) instead of using

    the more rigorous right-triangle method of HEC-RAS. See

    link.c and text.h. Build 5.0.017 (10/7/09)

3.  Inflow interface files no longer have to contain data for

    all of the same pollutants defined in the current project

    (e.g., they can contain just flows or some subset of the

    pollutants). See iface.c. Build 5.0.017 (10/7/09)

5.  The 2 GB binary output file size limit for runs made under the GUI

    that was inadvertently added into release 5.0.014 was removed

    (see output.c).   Build 5.0.015 (4/10/09)

Binary Output File (output.c)

41.  The Report Start Time written to the binary results is now

     adjusted to be be one reporting period prior to when the first

     result is reported so that the GUI uses the correct date when it

     displays results.   Build 5.0.014 (1/21/09)

Simulation Options

37.  A user can now choose to ignore any combination of the following

     process models when running a simulation: Rainfall/Runoff, Snowmelt,

     Groundwater, Flow Routing and Water Quality (swmm5.c, project.c,

     runoff.c, subcatch.c, routing.c, keywords.c, keywords.h, text.h,

     and globals.h). Build 5.0.014 (1/21/09)

Status Report (statsrpt.c)

38.  The heading for the maximum flow column in the Link Flow Summary table

     was changed to “|Flow|” to show that the flows listed are absolute

     values. Build 5.0.014 (1/21/09)

39.  The labels “Mgal” and “Mltrs” were replaced with “10^6 gal” and

     “10^6 ltr”, respectively. Build 5.0.014 (1/21/09)

40.  The widths for the various types of flow volume fields (e.g., runoff

     volume, node inflow volume, etc.) were increased in size. Build 5.0.014 (1/21/09)

Output Report (command line version) (report.c)

42.  Time series tables for reported subcatchments now report Snow Depth,

     Groundwater Elevation, and Groundwater Flow (provided that snowmelt

     and groundwater processes are included in the simulation). Build 5.0.014 (1/21/09)

RDII Changes

4.  Instead of using the rain gage’s recording interval as the

    time step for processing a set of RDII unit hydrographs, the

    smaller of the wet runoff time step and the time to peak of

    the shortest unit hydrograph in the set is now used. As a

    result, it is now permissible to use hydrographs whose time

    to peak is shorter than the rain gage recording interval.

    See rdii.c.  Build 5.0.017 (10/7/09)

8.  A bug created in release 5.0.015 that caused incorrect RDII inflows

    to be computed when the rain gage recording interval was less than

    the runoff wet time step has been fixed. (See rdii.c).  Build 5.0.016 (6/22/09)

9.  A new error check was added to detect if the time base of an RDII

    unit hydrograph is less than its rain gage recording interval.

    (See rdii.c).   Build 5.0.016 (6/22/09)

2.  Different sets of Initial Abstraction parameters (maximum depth,

    initial depth, and recovery rate) can now be specified for each

    of the three unit hydrographs (short term, medium term, and long

    term) that comprise an RDII Unit Hydrograph group (see keywords.h,

    keywords.c, objects.h, rdii.c, and text.h).  Build 5.0.015 (4/10/09)

35.  A problem with no RDII being produced when two or more RDII unit

     hydrographs utilized the same rain gage was fixed. Build 5.0.014 (1/21/09)

Time Series (table.c, error.c, error.h, objects.h)

36.  Time Series data can now be imported from an external file instead

     of having to be listed in the project’s input file. See the Users

     Manual or the Help file for details.  Build 5.0.014 (1/21/09)

Dynamic Wave Solution Changes

9.  A divide by zero error no longer occurs when computing the

    hydraulic radius of an empty Filled Circular pipe whose filled

    depth is zero. A similar error for the hydraulic radius of an

    empty trapezoidal channel whose bottom width was zero was also

    eliminated. See xsect.c.  Build 5.0.022 (04/21/11)

10. The critical or normal depth adjustment made for a conduit is

    no longer allowed to set the depth to zero — some small depth

    level is always maintained. See dynwave.c. Build 5.0.022 (04/21/11))

11. The Pump Summary Report was expanded to include number of start-

    ups, minimum flow, and time off both the low and high ends of

    the pump curve. See objects.h, link.c, stats.c, and statsrpt.c. Build 5.0.022 (04/21/11)

12. When the setting of an orifice or weir was changed to 0 (to

    completely block flow) the flow depth in the element wasn’t

    being set to 0. This was only a reporting error and had no

    effect on the flow routing calculations. See link.c.  Build 5.0.022 (04/21/11)

13. The Node Surcharge Summary in the Status Report did not report

    a ponded node as being surcharged. This was only a reporting

    error and had no effect on the flow routing calculations. See

    stats.c.   Build 5.0.022 (04/21/11)

5.  The check to see if flow in a link should not exceed the normal flow

    now uses just the upstream Froude number rather than both up and

    downstream numbers. See dynwave.c.  Build 5.0.019 (07/30/10)

6.  The maximum trials used when evaluating the flow and head equations at

    a given time period for dynamic wave routing was increased from 4 to 8.

    See dynwave.c.   Build 5.0.019 (07/30/10)

7.  The Ponding calculation for dynamic wave flow routing was changed once

    again to obtain better continuity results. The depth in a surcharged

    node that can pond is not allowed to rise higher than just beyond full

    depth in any single time step. After that, its change in depth is

    determined by the node’s ponded area. Similarly, the depth of a ponded

    node is not allowed to drop more than just below full depth in any

    single time step. See dynwave.c and node.c.  Build 5.0.019 (07/30/10)

8.  For Kinematic Wave and Steady Flow routing, a node’s ponded area is

    no longer used to infer a ponded depth when a node floods with Ponding

    turned on. Instead, the water depth is simply set to the node’s maximum

    depth and the ponded area parameter is simply used as a indicator as

    to whether the node can pond or not. (This differs from dynamic wave

    routing where the ponded area directly influences ponded depth through

    the solution of the momentum and flow conservation equations.) See

    flowrout.c.  Build 5.0.019 (07/30/10)

9.  As a consequence of the preceeding update, the Node Flooding Summary

    table in the Status Report no longer displays the maximum ponded volume

    in acre-inches (or hectare-mm). Instead it displays the maximum ponded

    depth (ft or m) for Dynamic Wave flow routing or the maximum ponded

    volume (1000 ft3 or 1000 m3) for other forms of routing. See stats.c

    and statsrpt.c.  Build 5.0.019 (07/30/10)

11. Controls based on flow rates now properly account for the direction of

    flow when they are evaluated. This may require users to add an extra

    condition clause to a rule that only applies for flow in the positive

    direction (e.g., AND Link XXX FLOW >= 0.0). See controls.c. Build 5.0.019 (07/30/10)

12. The Villemonte correction for downstream submergence is now also used

    for partly filled orifices (instead of just for weirs). See link.c and

    dynwave.c. Build 5.0.019 (07/30/10)

13. A missing term in the equation used to check for submerged inlet

    control for Culvert conduits was fixed. See culvert.c. Build 5.0.019 (07/30/10)

14. If a non-conduit link is connected to a storage node then its

    contribution to the node’s surface area is now ignored. See

    dynwave.c. Build 5.0.019 (07/30/10)

15. The automatic adjustment of the maximum depth of a link’s end nodes

    to be at least as high as the link’s crown no longer applies when

    the link is a bottom orifice. See link.c. Build 5.0.019 (07/30/10)

16. A fatal error message is now generated if a conduit’s entrance,

    exit, or average loss coefficient value is negative. See link.c.

    Build 5.0.019 (07/30/10)

1.  The Ponding routine for dynamic wave flow routing was once

    again modified, this time to account for the special case

    where a node transitions between surcharged and ponded

    conditions within a single time step. This should correct

    the large continuity errors experienced with ponding under

    release 5.0.016. See dynwave.c.   Build 5.0.017 (10/7/09)

2.  When the Ponding option is turned on, nodes that can pond are no

    longer always treated like storage nodes that never surcharge.

    Now they are only treated this way after ponding occurs. Otherwise

    they behave like a normal node. (See dynwave.c).  Build 5.0.016 (6/22/09)  

3.  The small tolerance used to decide when a storage node was full or

    not has been removed since for very small time steps it could cause

    a currently full storage unit to remain full even if there was some

    small net outflow from it. (See node.c). Build 5.0.016 (6/22/09)

4.  Spurious warnings for negative elevation offsets no longer appear

    when the “*” entry is used for the offset value or when the offset

    elevation value is within a small tolerance of the node invert

    elevation. (See link.c). Build 5.0.016 (6/22/09)

5.  When the water level at a storage node exceeds the highest level

    supplied in its Storage Curve, an extrapolated surface area from

    the curve is now used only if the curve is sloping outward (i.e.,

    surface area is increasing with depth at the top of the curve). If

    instead it slopes inward then the last surface area entry in the

    curve is used. (See table.c).   Build 5.0.016 (6/22/09)

3.  A Meander Modifier was added to a Transect’s parameters. It is the

    ratio of the length of a meandering main channel to the length of

    the overbank area that surrounds it. This modifier is applied to

    all conduits that use this particular transect for their cross

    section. It assumes that the length supplied for these conduits is

    that of the longer main channel. SWMM will use the shorter overbank

    length in its calculations while internally increasing the main

    channel roughness to account for its longer length. (See dynwave.c,

    flowrout.c, link.c, objects.h, and transect.c).  Build 5.0.015 (4/10/09)

6.  Any backflow that flows into an outfall node due to the head

    condition at the node is now correctly reported as part of the

    node’s Total Inflow result (see node.c).   Build 5.0.015 (4/10/09)

8.  The normal flow limitation for dynamic wave flow routing based on

    the Froude number now requires that the latter be greater or equal

    to 1.0 for both the upstream and downstream flow depths rather just

    for either of these (see dynwave.c).  Build 5.0.015 (4/10/09)

9.  A reporting error for the overflow rate into the ponded volume for

    a node that floods under dynamic wave flow routing was corrected

    (see dynwave.c).   Build 5.0.015 (4/10/09)

10. The practice of not allowing a computed top surface width to be less

    than the width at 4% of the full conduit depth for dynamic wave flow

    routing has been dropped in favor of using the actual width, no matter

    how small (see dynwave.c).   Build 5.0.015 (4/10/09)

Flow Routing (flowrout.c, node.c, inflow.c, link.c, and objects.h)

6.   A new Minimum Slope option has been added. When this option is non-

     zero a computed conduit slope is not allowed to be below this value.

     The default is 0. (Note: the slope of a conduit whose elevation

     difference is below 0.001 ft is first computed using this elevation

     difference and then is compared to the Minimum Slope value.) (The

     following files were also changed for this feature: keywords.c,

     project.c, enums.h,