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How to include a closed water reservoir (For eg. clear water sump from treatment plant, Ground level service reservoir, Mass balancing reservoirs - partially below GL) in the model. Can it be a reservoir element or only tank element in the model?

Tamil Amudhu
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We have  to revalidate the design of the network system consisting of Transmission main(s), feeder main(s) and distribution network system of a city using Watergems. The system consists of Transmission main(s), feeder main(s) with Intake sump, WTP clear water sumps, Booster station, mass balancing reservoirs, Ground level service reservoirs  and over head tanks supplied by both gravity and pumping. Whether these closed Intake sump, WTP clear water sumps, Booster station, mass balancing reservoirs and Ground level service reservoirs be a reservoir element in the model or only tank element?. I feel that unless the supply is from a dam these elements should be designed with a tank element only.

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    Tamil,

    Based on your description it seems like you want to model a submersible pump or pump ground water well. We have a wiki that explains how to do that which you can find here:

    communities.bentley.com/.../16108.modeling-a-submersible-pump

    There is also a help topic that comes with the software titled "modeling a pumped ground water well " that explains what you need to do in a little bit more detail how to model this.

    As you stated in your question, you could use a reservoir, which has a fixed hydraulic grade line, even through an EPS simulation, and is an infinite source of water. If your source is not infinite you should use tank. It also has a fixed hydraulic grade line if you're only running a steady state analysis, but will draw down or fill over the course of an EPS simulation.

    Regards,
    Mark

    Mark

  • 0 Offline in reply to MPachlhofer
    Just to expand on what Mark says, if you are doing only steady runs, it doesn't matter whether you use a tank or reservoir element.

    Most users, set the WTP clearwell (clear water sump) as a reservoir in the EPS runs. If you set it as a tank, then it will drain unless you specify an inflow to the clearwell that matches the outflow. Since you don't know the plant outflow a priori, trying to match inflow and outflow at the clearwell can get tricky. What you usually do know is that the level doesn't change by much over a day, so a reservoir makes sense.
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    Hi! Mark and Tom, Your replies are helpful. Exactly the modelling for the city has some basic requirements and limitations. Requirements are: 1) The MBRs and clear water sumps of WTP are existing and to be revalidated for 24 x 7 water supply. 2) The present inflow is known for every MBR / WTP sump and to be checked for total demand. 3) Better if EPS is done to fulfill peak flow and minimum pressure requirements. 4) The model to be checked for minimum water level of the MBR / sump under 24 x 7 supply. Limitations are 1)Source(s) are limited and are not infinite 2) MBR / clear water sump are all closed; have inlet at top of the tank and outflow from bottom. 2) Pumping is only 22 hrs 3)Pumps are of both HSC and VT and all are running. As suggested under steady state the MBR / sump shall be better as tank element; and for EPS model the MBR / sump shall be as reservoir element. What is the better option to revalidate for the above requirements and limitations?
  • 0 Offline in reply to Tamil Amudhu
    Hi Tamil Amudhu,

    Based on the description, I understand that you are referring to a project in India. Typically for steady state analysis you can use a Tank to model the Mass Balancing Reservoirs, etc. Using tank as an element in EPS essentially depends on the knowledge of the demands or the consumption rate. You need to calculate the Mass Balance Curve for each of the tanks and check the surplus or deficit for every tank; (This has to be done very easily in MS Excel and you would also like to check that the tank doesn't overflow or becomes empty.)

    So to state simply, you can use tanks in EPS when you have the mass balance curve calculated (knowledge of vol. of water in the tanks, capacity of the tank, max./min. levels, demand consumption pattern, peak factor, etc is required) and you can use Reservoir (essentially, an unlimited source of water at a given elevation) when the tank info is not available.

    Tanay
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