Water age results in a pipe are different from the age in the downstream junction

 Applies To Product(s): WaterGEMS, WaterCAD Version(s): 08.11.xx.xx, 10.XX.XX.XX Area: Output and Reporting Original Author: Scott Kampa, Bentley Technical Support Group

Problem Description

After computing the water age for a system and looking at the results, the calculated water age in a pipe is significantly different from the calculated water age in the junction directly downstream of the pipe.

Reason

The water age in the pipe is calculated at three points. The property field "Age (Calculated)" is the water age at the midpoint in the pipe. The property fields "Age (Start)" and "Age (Stop)" display the water age at the beginning and the end of the pipe, respectively. If you look at the results for "Age (Stop)", you should see that the calculated water age for "Age (Stop)" correspondes with the calculated water age at the downstream junction.

You will generally see some difference in water age between the start and stop nodes, but if the pipe is short or if the velocity is high, the difference will generally be small. However, if you are seeing that the water age in the pipe varies greatly between the start and stop of the pipe, the likely cause is that the velocity in the pipe is relatively low, or that the pipe is relatively long. You can look at results for velocity and travel time in the pipe, which will likely show that it takes time for water to get from one end to the other. The water will age in the pipe, so the water will be older by the time it reaches the end node.