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WaterGEMS Constituent Analysis

I attempting to create zone of influence diagrams for our distribution systems.  The way I am going about it is to utilize the constituent calculation option.  From what I understand, if I have a system that has three water treatment plants I must creat three different scenarios and run an analysis for each one.  Fore each scenario I setup up the constituent alternative for an individual plant by applying a concentration at the plant reservoir.

When seting the alternatives I input following generalizations to get me started:

I use the default constituent setup such as first order wall reaction.

Concentration (Base) = 100 (mg/L) , Concentration (Initial) = 100 (mg/L) , Mass Rate (Base) = 100 (mg/s)

Then I use the time browser animation to review the dispersion of the concentration.  Once the concentration has reached it extents then I know my zone of influence for each plant.

My question is, by using the numbers I listed above, when I run each scenario and add the calcuated concentration at a node in the system from each scenario at the same time from start,  shouldn't it equal 100?   Should I be able to see exactly how much constituent is contributed from each supply to a node in the system?

Respectfully,

Aqueduct

  • You're timing is very good. In our latest release, WaterGEMS SELECTseries 3, we have just added a new type of analysis called "Water Quality Batch Run" which does essentially what you are asking for without the need to set up a bunch of scenarios. Download the latest version from SELECT server and read the help. I think you'll like it. There are some nice visualization tools that come with this.

    With regard to all of the concentrations or source percentage adding up to 100, remember that there is water in pipes and tanks at the start of the run and this water needs to be used up before things add up to 100. The sum should asymptotically add up to 100 as the duration of the run increses.

    With regard to the overall problem you are solving, if you have pumps that cycle, you'll find that the zone of influence of each source can vary pretty widely depending on time of day. Users are often surprised by the variation in these zones over the course of a day.

    Tom

  • Tom:

    Thanks for the quick reply. I will download the latest release and check out the Water Quality Batch Run right away.

    One other question.  I have a rather large system that I setup for a constituent analysis.  The parent scenario is an average day standard EPS scenario and it runs beautifully.  However, when I set up a child scenario for a constituent analysis and change only the calculation option from EPS to Constituent I get a network unbalanced error.  Is this common with the constituent option?

    Respectfully,

    Aqueduct

  • Changing from EPS to constituent should not normally cause problems with the base hydraulic results. I would suggest checking the two calculation options sets (the one for the EPS and the one for the constituent runs) and compare some of the other options, like the hydraulic accuracy, engine version, etc. It's possible those were changed.


    Regards,

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

  • That shouldn't happen. If this issue persists, contact tech support.

  • Jesse:

    You are the man!!  I did compare the two calculation options and it appears that the enginer version for the EPS option is different from the Constituent option.

    I was sure I did not change it because I am so leary to tweak that area of the model.  So I did a little looking around at my other models and it seems that most of the pre-existing calcuation options already setup in the model contain an older engine version.  However, if I create a new calcuation option a later engine version shows up. I am glad I asked the questions because I would have never figured that out!

    Respectfully,

    Aqueduct