Bentley Product:: SewerGEMs V8i (Selectseries 5) Version 08.11.05.58 64 Bit
Project Notes: Analyzing Node DB-Detention Pond
Model A: Includes 8 detention systems to control runoff before it enters detention pond DB.
Model B:Includes 4 detention systems to control runoff before it enters detention pond DB.
The flowrate into node DB does not change with additional detention storage under 10-Year Storm ModelThe flowrate out of node DB increases with additional detention storage (model A) under 10-Year Storm Model.
Upstream detention nodes include orifice and weirs to control watershed runoff.
SewerGEMs - NEWR.zip
Thanks for the files Suraj Kumar.
I'll take a look and reply through the email link on the SR and post my results here also.
"Model A" is set to use a 1-year storm while "Model B" is set to use a 10-year storm. This means runoff will be higher from catchments in the Model B scenario.
I see that the "detention systems" that you added in the "Model A" are 4 additional ponds upstream, in series with the other ponds that ultimately discharge into the "DB" pond. It seems that this model distributes catchment runoff to these four additional ponds, to help prevent PO-6 from overflowing. If I change Model A to use the 10-year storm (to match Model B), I can observe this impact - PO-6 does not overflow and the overall volume of flow is the same (just attenuated from the ponds)
This does not necessarily decrease the peak flow into the "DB" pond though, because of a few factors:
Additionally, I noticed that you're using quite an old version, which will no longer be supported soon. See this article for more about our Support Policy and this article about upgrading. We have introduced many improvements to the numerical solver in newer versions, which may impact the results for your model.
Jesse DringoliTechnical Support Manager, OpenFlows ProductsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Suraj Kumar
Thank you so much for your assistance. This has helped me understand the model some more and the continuity error has dropped since adding pond outlet structure at POS-19 as you suggested.
Is there a way to model the overflow per factor 1? In other words, when the upstream detention structures fill up, does the overflow make its way to detention pond DB?
The goal of the the upstream structures is to control the downstream runoff and pond elevation, so I wanted to confirm if the overflow doesn't get get lost or neglected because the ponds fill up.
When a pond's water surface elevation reaches the top, overflow occurs which is lost to the system. It does not get routed anywhere and it accounted for in the "overflow volume" in the mass balance seen in the Calculation Summary window.
If you need to direct the overflow somewhere else, you will need to use a separate pond outlet node and direct the discharge using a conduit connected to an outfall, connected to the downstream element. See this article for more.
Sorry about the late response - I just wanted to confirm our model was set to go. Adding an orifice to the pond outlet structure and confirming the overflow has helped with the model's accuracy. Thanks so much for your help.