How Do the TimeOpen and TimeClose Controls Work in #SWMM 5.1.012

This is part of the #Inside_#SWMM5 series of blogs and is intended as a visual aid and code developer for the Storm Water Management Model Reference Manuals on https://www.epa.gov/water-research/storm-water-management-model-swmm  I always think images (and some words) are best at explaining the internal working of code.  I do encourage you to read the wonderfully written Storm Water Management Model Reference Manuals.

The controls we are examining are the TIMEOPEN and TIMECLOSED commands in #SWMM5.  These commands are defined in the SWMM5 help file as

TIMEOPEN is the duration a link has been in an OPEN or ON state or have its SETTING be greater than zero; TIMECLOSED is the duration it has remained in a CLOSED or OFF state or have its SETTING be zero.

Here is an example rule,

RULE COUNT1

IF SIMULATION TIME > 0.0

THEN PUMP PUMP1@82309e-15009e SETTING = 1.0

PRIORITY 1

RULE COUNT2

IF PUMP PUMP1@82309e-15009e TIMEOPEN >= 2

THEN PUMP PUMP1@82309e-15009e SETTING = 0.0

PRIORITY 5

Here are the control actions taken during the simulation

Here is how the Timer for TIMEOPEN and TIMECLOSES are reset based on the Setting, Target Setting and Rules.  Notice the time is reset every 2 hours.

Here is how the Setting and Flow are used during the Simulation – every 2 hours TimeOpen is reset.

My History with Various Versions of SWMM: SWMM3, SWMM4, SWMM5, XP-SWMM and InfoSWMM

Subject:   My History with Various Versions of SWMM: SWMM3, SWMM4, SWMM5, XP-SWMM and InfoSWMM

I first learned about SWMM in a brochure from the University of Florida when I was just a 17 year old senior in High School.  Water resources and the description of SWMM seemed to be worthy career goals at the time and I have been extremely lucky to have the opportunity to work and develop many SWMM related products in my working life.   I am especially proud that SWMM 3, SWMM 4 and SWMM 5 are both public domain and open source software.  You can open up and look at the code and add features and internal tests on your own.   You can customize the input and output of SWMM 5 if you want to but most importantly you have direct access to the source code so you can verify the computational algorithms.

InfoSWMM is an Arc GIS extension that works in Arc Map but we at Innovyze are proud that we have superb import and export features to SWMM 5 from Arc Map and use the SWMM 5 engine as our engine solution.   You can look at the internal workings of the InfoSWMM engine by downloading the current SWMM 5 C code from the EPA website http://www.epa.gov/nrmrl/wswrd/wq/models/swmm/   InfoSWMM also has all of the Arc GIS programming tools, Python programming,  editing and drawing features and Table of Contents attribute features to make a better model but that model will still use the open source SWMM 5 engine inside of InfoSWMM.    When you use InfoSWMM you are using the SWMM 5 engine  but with many extra input and output features to help prepare the data for the current SWMM 5 engine and analyze the SWMM 5 engine output  in maps, tables and graphs.

The following was edited to reflect the passage of time:
PS in 2013/2016. I am now at my 45th anniversary of 1st hearing about SWMM, my 41th anniversary of seeing Wayne Huber or Jim Heaney mention SWMM in an Introduction to Environmental Engineering Course at UF, my 39th anniversary of 1st seeing the SWMM 2 punch cards for a mainframe computer, my 37th aniversary of meeting Bill James of UG and the Future CHI and Larry Roesner of CDM and now with CSU, my 36rd anniversary of being a coauthor and coprogrammer of SWMM 3, my 28th anniversary of being a coauthor of SWMM4, my 24st anniversary of being a XP-SWMM developer, my 18th year anniversery of being a Visual SWMM developer at CAiCE, 18 years since I first heard of Paul Boulos and MWH Soft, 17 years since I first meet Lew Rossman, 16 years since I first started working on SWMM 5 while at CDM with all of my great CDM colleagues (Jim Smullen, Ted Burgess, Carl Chan, Khalid Khan etc) and Lew Rossman and Trent Schade at the EPA and now 9+ years at Innovyze with our worldwide network and dedicated engineers and developers.   I have also learned very much from our really good customers and their important/interesting models.

Odd, I thought I had a lot of experience before I joined Innovyze in 2008 but dealing with the synergy of support, development, sales and training for multiple software products around the world brings it with another level of understanding and insight into modeling and model development.  Thanks very much to all my Innovyze customers, Innovyze Management, Innovyze CSM's, Innovyze Developers, Innovyze Support Engineer and Innovyze in general. My special thanks to Paul Boulos, Roger Ro, Fayu Lai and Chun-Hou Orr for their support, brilliance and creativity.  I could also thank hundreds or customers but Stewart and MJ stand out in my mind as being the best and most creative and I wish them both well in their future.  Keith Hodsden and Paul Hsiung are also standout CSM's at Innovyze and I owe them a lot as does the engineering community in general.

I would be amiss if I did not mention my wife and three children/offspring who have had to live with the world SWMM for her whole married life or literally their whole lives in the case of my children.  I could not have done it without my wife's organizational skills, hard work and patience.  We have learned from our children their whole lives - they are also hard working, brilliant engineers and writers/developers who have always impressed me as being smarter their parents, which made them easy to raise.  Here is a short video about how they helped me with SWMM: A Short Film: What Is The Meaning of Life? http://www.youtube.com/watch?v=lRQAIRBDVxw&feature=youtu.be … [inspired by @RDickinson & shot with @googleglass & edited w/ @givit] Thanks @boonsri

Best Regards,
Robert Dickinson

SWMM5 Normal Flow

Option "Define Supercritical Flow By" does inside the SWMM 5 engine. The options are called Slope, Froude and Bothin the GUI and in the engine of SWMM 5. A few other variable definitions you need to know to understand this explanation are: (1) Y1 for the upstream link depth, (2) Y2 for the downstream link depth, (3) Q for the flow in the link, (4)Qfull for the full Manning's equation flow or normal flow for the link based on the bed slope, (5) Froude1 and Froude2 for the Froude Number respectively of the upstream and downstream ends of the link, (6) n for Manning's roughness, (7) Yfull for the maximum depth of the link and (8) Qnormal for the Normal Flow equation flow based on the upstream area of the link (A1) and the upstream hydraulic radius (R1).

In the SWMM 5 engine these options are used after the dynamic wave equation flow is estimated using the St. Venant equation. The option that you choose is only active for those links that have a flow greater than 0, links with negative flow use the dynamic wave equation flow exclusively. It the flow is positive and the link is an open channel and full then the minimum of the dynamic wave flow or Qfull is used as the new flow in the link. If the flow is positive and the depth at the upstream end of the link or Y1 is less than Yfull then the engine will compare Qnormal to Q using the routines in Check Normal Flow.


If the link gets to the Check Normal Flow routines then it uses the following logic:

• If the Slope or Both option is used or either the upstream node or the downstream node of the link is an outfall AND Y1 is less than Y2 then the minimum of Q from the dynamic wave equation or Q from the Normal Flow equation is used as the current iteration flow in link, or


• If the Froude or Both option AND either the upstream Froude Number or the downstream Froude number is greater than 1 then the minimum of Q from the dynamic wave equation or Q from the Normal Flow equation is used as the current iteration flow in link. This condition is never used if either of the connecting nodes of the link are outfalls.

How does this work in the actual flow that SWMM 5 estimates for a link? Consider this example in which the link flow in blue is plotted with the Qnormal flow in red and the Q dynamic wave equation flow in purple:



Qnormal is







Qnormal is only calculated when the link is not full so in the plot a Qnormal of 0 means that the pipe was full. At other times the flow in the link was equal to Qnormal as the minimum of the dynamic equation flow or the Qnormal flow is used at each iteration in the solution process. The flow is normally bounded by the Qnormal flow in SWMM 5.0.013. Your choice of the options Slope, Froude andBoth really only impact the conditions under which this comparison is true. If you use Froude or Both then Supercritical flow at either end of the link will trigger this comparison will be the dynamic wave equation flow and the Froude number at each end of the link.