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Is there a way to "reset" water age, our surrogate for water quality, at a chlorine booster station?

Because there is no simple method to truly develop a Water Quality model – jar tests, wall decay, variability of temperature, demand and season make this arduous. We use water age as a surrogate for water quality.  This has worked well.


However, we recently installed a PAX-RCS system which allows us to “refresh” the chloramine levels and in effect reset the water quality. In the model, we are not able to “refresh” the water age by including some type change at our tank.  This would be a nice feature.


My alternative may be to create a generic constituent model, where I could reset the water quality.


If there is another method – please let me know.

  • Darrin,

    The way to adjust the chloramine levels at a node element can be done using the 4 different constituent source types. The definitions for those are described in the following wiki. Based on how the system works one of the source type options should work for you.



  • An age analysis only "resets" age tracking at reservoir nodes, so the only way I can think to do it, whilst keeping the model calculating age is a bit goofy. It would involve, for every tank that requires a reset, running the hydraulics, then taking (copying) the HGL results for the tank, and applying them to a reservoir (via a reservoir pattern) at the same location, and then re-running the model (with reservoir connected in lieu of the tank), so that the WQ analysis treats the tank as a fresh water source and thus resets age at that location.

    There are obvious caveats to the above though.
    1. Requires manually creating a reservoir pattern for each tank, based on the hydraulic results for the tank.
    2. Requires running the model twice (each time the results are liable to change).
    3. Could be tricky to capture HGL changes at intermediate time steps (affects the HGL pattern).
    4. Gets more involved if tanks have control conditions on them.

    I guess it would depend on how often you need to run the model, how many tanks etc, but I cannot imagine the above being tractable in most practical situations.

    I guess that is the long way of saying that there is not really another method than switching to a constituent analysis, which as Mark indicates, includes different options for controlling constituent levels at source nodes.

    Answer Verified By: Sushma Choure 

  • Thanks for the reply. I thought there might be a way to use a reservoir but had not yet thought it through. 


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