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Thread: Interties and InfoWater

  1. #1

    Question Interties and InfoWater

    An Intertie for a Water Utility can be used to obtain water from a neighboring water utility or send water to a neighboring water utility. In InfoWater this would mean that an Intertie can be a Reservoir or a Demand.

    I have some ideas on how to represent an Intertie in InfoWater.

    How do you represent an Intertie in InfoWater?
    Tim Hayes
    GIS Manager
    City of San Jose Municipal Water System
    San Jose-Santa Clara Regional Wastewater Facility

  2. #2
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    Tim,

    It really does come down to modeler preference. But as I did 16 years of consulting in the past, here are some of the reasons I think many seem to prefer the Reservoir Approach over negative demands.

    The EPANET engine used by InfoWater and InfoWater Pro and H20NET, when there is a negative demand will identify the head needed to push that flow into the network. As long as all the negative Demand (i.e. supply) has a place to go, this generally works reasonably. Negative demands have disadvantages in that they cannot be easily turned of by looking at system conditions and can cause oddities if excess supply has no where to go (very high pressures). The one other downside to a negative demand is that it is not always obvious in a model where they are located. There is nothing in them to make it clear what they are and this may cause less experienced users to overlook them initially. To me this is the major challenges with negative demands if the supply is not continuous or if you need to do a very long EPS run and may have an imbalance in supply and demand. They certainly can be very useful, but are not as obvious or flexible that I tend to prefer not to use them if possible (at least personally).

    The easiest way to model an intertie (or what I like to call a purchased Water Connection (turnout) or Emergency Supply) is as a Reservoir followed by a Valve that controls supply based on how water is provided. The valve if keeping a constant downstream head (and thus the pressure) could use a Pressure Reducing Valve or PRV, or if supply is regulated at a specific flow, then perhaps a Flow Control Valve (FCV) might be more appropriate. If you have either of these types of connections then the actual Reservoir Head only needs to be high enough to ensure the maximum flow expected in the model and may not be critical to match to the real system. If this is the case setting 100 ft or more of additional head in the reservoir higher than the actual discharge head may be fine to accomplish just that. It really comes down to modeler preference. If the location turns supply on or off based on specific system conditions then the valve can have controls added to it so that the supply location is controlled similar to the actual system does. Keeping any storage tank from going empty or going 100% full when there is either not enough or too much supply can easily be done with simple controls on the valve. Just make sure when a valve is closed to turn it on again to use the "Setting = "X" format for the control as status = OPEN makes the valve act like an open pipe. This method generally has very little downside and is almost always 100% clear to any modeler what it is representing.

    If the connection is an emergency connection the valve and reservoir method can make this very clear and the valve can only run in scenarios where the emergency connection needed and it is easy for a novice user to tell where the connection is located. In addition is it is a constant connection, the valve and reservoir method also make it obvious where supply comes from using this method regardless of the experience of the user.

    If the connection is a "two way" emergency connection you may want to have two directional valves and reservoirs one for supply and one for receiving water, just so that it is clear where water is going and that the head values are set up for taking or receiving water. You don't always seem to do a lot of modeling of these locations in many systems, that this could allow the best flexibility, but this is not the only way to do this.

    Again, it really comes down to modeler preference, but making a model "user friendly" seems to be a touch easier with the valve/reservoir method as well as having the easy ability to control the supply that to me that I have always favored it over negative demands. But there is no hard and fast rule of which way is the best and both can work if used properly.



    Great question by the way.

    Patrick Moore

    Quote Originally Posted by sewermapguy View Post
    An Intertie for a Water Utility can be used to obtain water from a neighboring water utility or send water to a neighboring water utility. In InfoWater this would mean that an Intertie can be a Reservoir or a Demand.

    I have some ideas on how to represent an Intertie in InfoWater.

    How do you represent an Intertie in InfoWater?

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