I am trying to model 3 interconnected ponds all with composite outlet structures. It seems like I am doing something wrong because PondPack is having a hard time computing the rating curve for the first outlet structure. By a hard time I mean that the model is taking several hours to generate the curve (after 4 hours it did not get past TW elevation of 4.5 ft out of 9 ft). I am able to see the rating curves for the following composite outlet structures in the next 2 ponds when computed separately for verification purposes.
The first composite outlet structure consists of 3 weirs and a box culvert. Basically we have a culvert which discharges to a small 4ft tall weir and then to another 3 ft tall weir in series. The 3rd and last weir represents the roadway. The 4 ft weir is being modeled as an irregular weir and the 3ft one as a suppressed one. The weir representing the roadway is being modeled as an irregular weir approximately 330 ft long. For each pond, I am imputing elevation-area curves and with large catchment areas. The elevation-area curve for the first pond looks like this:
Table above shows SF but area used for PondPack model was acres.
The cross-section for the irregular weir representing the road in the first pond looks like this:
Here are the screenshots for each component of the first composite outlet structure:
Weir one and XS:
Weir 3 (Roadway) and XS:
Does anyone know why this issue may be happening? Any help is much appreciated. Thank you
I see that you created a service request for this as well, with a copy of the model. We will take a look at this and let you know what we find out.
Can you confirm if the size of the ponds is accurate? Pond Bay Shore Dam has an area of nearly 1500 acres, which seems very large given that it is only 6 feet deep (this is 3 times the size of a lake where I am from). Given the volume of water involved, this may be having an impact on the time it is taking.
Answer Verified By: Sergio Carvajal Sanchez
Thank you so much for getting back to me. I believe the size of the ponds are accurate. This area is extremely flat in New Jersey near the Delaware Bay, which is why elevation varies so little. Like you said, I did think the size could have an impact in the run time but when I tried to run the model, the progress stayed at 0.00% for over 3 hours. I am able to get the rating curves for each composite outlet structure in a matter of seconds except for where we have the culvert (Nummytown Dam Outlet Structure). Therefore, I am assuming there is some kind of issue for that specific composite outlet structure.
Thanks again and please let me know if I can provide any additional information.
Set the Downstream ID in each of the components of the composite outlet structure for Nummytown Dam Outlet Structure to "Tailwater". That will take care of the issue.
Thank you so much! This solved the issue. I appreciate your time.
Just to add - convergence problems and slow performance with Composite Outlet Structures can occur when using culverts in series with other outlet components. See more in this article from our Wiki: Convergence problems, very slow calculations or "out of range" message when using culvert in series with another outlet component
Jesse DringoliTechnical Support Manager, Haestad ProductsBentley Communities Site AdministratorBentley Systems, Inc.