That's a very good question and most of the time you will find a very good explanation in Water Quality books. So, I encourage you to go through some of the books to fully understand the nature. Here's what I generally do for reporting Water Quality results. 1) Don't report the Water Age from a dead-end location (with no demand) because it will not truly represent your network water age. Here's a proof from your model. Based on the graph below the water age is 120 hours and that's certainly is not the case. So, avoid dead end water age. 2) We don't want to report water age right at the treatment plant (a water source) either. Here's why. The graph below shows water age immediately downstream of a reservoir. In this case the water age is 0 (zero) which definitely doesn't represent the system water age. 3) Also avoid odd-ball area like the one that you mentioned, pipe P-685. Can you guess why? Let's look at some the image below where I have graphed couple of elements with flow and water age. Notice the Flow in P-54 and the flow in P-685. Compared to P-54, there is very very small flow going through P-685. When the flow is smaller, the water will stay longer (stagnant water) in the pipe (or a network). When water stays longer in the system, you will see high water age. Hence, you are seeing a higher water age. The water age you are seeing in junctions are same as the water age around that node so no surprise here. 4) Not applicable to this specific model but you ALWAYS want to look at the water age in tanks. 5) Before reporting water age, you want to run the hydraulic model for quite some duration, like 30 days or so. Basically once the model ran for longer duration it reaches water age equilibrium. (N/A for this model as it doesn't have any tank and it's the tank that takes long time to reach equilibrium because of higher water volume). Literature will explain this better 6) When reporting Water Age, it's a common practice to look at the last 24 hours worth of result. So, if the model ran for 360 hrs then report result from 336th hour to 360th hour. [Analysis Post Calculation Processor can help to get the last xx hours of data. Use this link for help ]
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