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Having issues with a storage basin drain down simulation

Posted by Ian Griffin on August 19, 2014 at 2:10pm in SWMM5

Hi,

I'm having issues with an  attenuation feature. I've simulated the rainfall event (24 hours) and now I'm looking to see how long it will take to drain down using outlets with Head/flow relationships (simulated vortex controls e.g hydrobrake). Problem is that the storage unit doesn't want to drain down after 24 hours - even though in the map view I can see flows out of the feature in the subsequent days. Its stuck at the same level and volume.

Any ideas?

Ian

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Replies

  • Ian Griffin August 21, 2014 at 2:34pm

    Hi Robert,

    no it's not that - its more peculiar. It varies with simulation runs. I can press the button again and get a different result. Sometimes it goes to 72 hours as expected (then stops) and then on other runs it only gets to 24 hours before it levels off. The lowest it has drained is to 0.5m in 72 hours. I can see outflow at the nodes during the periods its not emptying but the storage isn't going down. I might just delete and replace the storage node and see if that fixes it. Could this be a time-step issue?

    Thanks

  • Robert Dickinson August 19, 2014 at 10:09pm

    It looks like your tank has no outflow  when the depth is less than 0.65  feet  - what is the offset depths for the links coming out of the pond?

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