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PondMaker Error_SewerGEMS

I am designing a pond, and When I run the design Scenario Configuration in the pondmaker in the SewerGEMS for scenario " 50 Years 24 hours scenario", I am getting unexpected failure during the calculation. 

What cause that and how can that figure out? the model shared for review (Run Only 50 years scenario).

Regards,

Mohamad Azzam

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  • Hello Mohamad,

    As mentioned in the PondMaker wiki, PondMaker is typically used to help in designing a pond for use in the post-development case based on pre-development input. In your model, you have set the target scenario and the design scenario to the same selection, which may be part of the issue. You would need to set the target scenario is pre-development scenario while the design scenario will be the post-development scenario.

    If all you are doing is trying to find a pond that will work well with your modeling case and you don't actually have a pre- and post-development case, it will be better to simply enter data for your pond and pond outlet structure, then adjust this input as needed until you are happy with the results.

    Regards,

    Scott

  • Thank you Scott,

    You mean I can not get the benefit from pond maker " in this case" to design the pond and the outlet structure, and I have to do trial and error to find the suitable size for pond, orifice and raiser?

    is there a workaround to use the pond maker in this case? you have seen the model has many scenarios and so big, our target to run the 50 years scenario to size the pond and the outlet pipe and find how many days to empty the pond. Please advise.

    I uploaded the simplified model for the pond where I used the hydrograph from the original model as input at manhole before the pond and I created pond level, however; the pond graph does not present the depth and the output in the profile and graph as expected, also the outlet structure does not show the flow discharge in spit the pipe to evacuate the pond is 1400 mm. your feedback and advice are appreciated. 

    Thank you,

    Mohamad

  • Hello Mohamad,

    Regarding PondMaker, unless you target and design scenarios are different, it doesn't make sense to use PondMaker. The way it works is to try to design a pond where the outflow from the pond matches closely with the runoff from a pre-development scenario. This means that the tool is expecting the post-developement runoff to be higher than the pre-development runoff. The pond would be used to store the excess runoff, while the pond outlet structure would limit the flow such that the outflow is close to the pre-development runoff.

    If the target and design scenarios are the same, as it is in your model, the tool would basically tell you that no pond is needed. The target and design outflow would be identical, thus no pond would be required to store the runoff. That is why PondMaker would not really be a benefit to you in this case.

    You would likely want to size the pond and outlet structures for whatever case you decide is the biggest benefit. Making sure that the pond can handle larger storm events makes sense, but that will ultimately be up to your engineering judgment and knowledge of the system.

    Regarding the sample model you provided, there is no discharge from the pond because of the pond dimensions. The elevation-area curve has areas on the order of 150000 hectares (about 1500 square kilometers). Because of that, the pond never really fills enough for the outlet structures to work. If you adjust the area of the pond, you will likely see outflow.

    Regards,

    Scott

    Answer Verified By: Mohamad Azzam 

  • Hello Scott,

    Regarding the sample, even the area of the pond is big, the pond should discharge the flow and the outfall should present a graph, I did the sample on other program and I got results at the outfall. in sewergems the orifice located at the bottom of the pond, means I have to get flows out of the pond. as said earlier that works in other program using the same pond area graph, I guess should work in sewergems as well. 

    Thank you,

    Mohamad

  • Mohamad, your pond is set up to be 1200 square kilometers, and the lowest outlet is slightly above the bottom of the pond (35.7 m vs. 35.5 m). Because of this enormous area, the depth never increases and so there is zero headwater at the outlet structure, so there is no outflow. Are you sure the area of 1200 km^2 is correct? What does this represent?

    As Scott mentioned, PondMaker works under the assumption that you are trying to attenuate the pond peak outflow in the postdevelopment conditions to be less than our equal to the peak flow in the predevelopment conditions. If you do have a target peak flow in mind, select "user defined" for the "target flow/volume source" in step 1 of PondMaker, then enter your target peak flow in the table at the bottom. 

    However, the pond and outlet need to first be configured as flow in=flow out if you would like to use PondMaker. For example set the pond outlet node's "has control structure?" to "no", using the largest available pipe size for the pipe between the outlet and the outfall, and set the pond initial size to be relatively small. For example 1200 square meters instead of the current 1200 square kilometers.

    If your pond design goal does not match PondMaker's assumptions, then you would use the main user interface as Scott mentioned to design your pond, but you'll need to use a more reasonable pond size in order to generate outflow.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Mohamad Azzam 

  • Hello Jesse,

    I have a mistake in the area units, it is not ha, the numbers should be in sqr.m.

    I will follow your advice and find out.

    Regards .... Mohamad

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