Can I start trace analysis at other time than simulation time?

Product(s): Bentley WaterGEMS, WaterCAD
Version(s): V8i, Connect Edition
Area: Modeling


If we want to simulate the distribution of the contamination in the network using the trace function but we want to set that the time of start to be 06:00 or 08:00 and not at the time of the simulation beginning. Where can we set the time to start the activation of the tracer?


There is not a direct way to start the trace analysis at other time than simulation start time. However, there is a workaround to achieve this using constituent function.

You can use non-reactive constituent here to mimic the trace results to start trace analysis at the time other than simulation start time using constituent pattern.

  • Set the calculation type to Age, Constituent and Trace in calculation options.
  • Create a new non-reactive constituent with default settings.
  • Create a constituent pattern that starts at 0, and then goes to 1 when you want the trace to start.

  • Pick the desired trace element and set it as a constituent source.
    • Type Concentration
    • Base: 100 mg/L
    • Pattern: Assign the constituent pattern defined earlier

  • The element needs to be defined as both trace source and constituent source. Hence change the constituent/trace source as the node/junction of your interest.
  • Set all junctions and tanks to have a Trace Initial % = 0.
  • Compute the model
  • Concentration values in mg/L should match trace values in percent, so constituent values will mimic the trace % results in this workaround, i.e. the constituent analysis behaves like trace.
  • If the pattern starts later than the set time then reduce the calculation time step.

See Also

Getting data and setting up for a Constituent Analysis in WaterGEMS and WaterCAD 

  • Created by Bentley Colleague
  • When: Mon, Jul 19 2021 5:02 AM
  • Revisions: 1
  • Comments: 0