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In Darwin Calibrator why is my "original demand" on the solutions tab not matching with the demand entered in the demand control center?

Applies To 
Product(s): WaterGEMS, WaterCAD
Version(s): 10.00.xx.xx, 08.11.xx.xx
Area:  Modeling
Original Author: Mark Pachlhofer, Bentley Technical Support Group


In Darwin Calibrator why is my "original demand" on the solutions tab not matching with the demand entered in the demand control center?


First, make sure the scenario that you're looking at in your model is the representative scenario listed on Darwin Calibrator's Field Data Snapshot tab.


The original demand is not actually the original baseline demand for a given node that is listed in the demand control center, but rather the original demand from the demand control center multiplied by all the pattern factors (hourly, daily, & monthly) that are associated with that demand. The hourly, daily, and monthly multipliers from the pattern are determined by the last field data set that was simulated. Using the screen shot above as an example, the last field data snapshot is "Flow Test 3" and  the original demand would be equal to <whatever the demand is in the demand control center for a particular node>  *  <the pattern multiplier for 10:20 am>  *  <the pattern multiplier for Friday, which is the day of the week 1/18/2002 fell on>  *  <the pattern multiplier for January because that's the month the field data snap shot was taken>. Another example of this using some data would look like this: Take a field data snapshot for Hydrant A, which will be the last snapshot in the field data set. We'll use junction 1 as the particular junction we'd like to find the original demand for. The base demand for junction 1 is 5.25 gpm and the pattern assigned to it is titled "Diurnal".

From the Diurnal pattern we see the hourly pattern factor would be 0.6 because the time this field data snapshot was taken was at 2:20 PM. The monthly multiplier should be 1.2 because the snapshot was taken in the month of June.

The daily pattern is 1, so we can omit that from the calculation. So 5.25 * .6 * 1.2 = 3.78 gpm, which is what you should see listed for the Original Demand.

You might also notice that the adjusted demand value is equal to the original demand value. This is because the demand adjustment factor is set to 1.00 (see blue boxes in screen shot above). If the demand adjustment factor was set to 0.5 then the adjusted demand reported in the solution would be 1.89 gpm, but the original demand would still be shown as 3.78 gpm. For a manual calibration run you enter these demand adjustment factors, but for an optimized calibration run Darwin Calibrator chooses this value from the allowable range of choices you provide it. These demand adjustments are entered on the demand tab in the demand multiplier column (see screen shot below).

If your original demand is not calculating out correctly you should also check to see if you have a demand multiplier set for the field data snapshots in the location shown below. Adjusting this demand multiplier will adjust the original demand value.

With that stated what's important with the reported demand adjustment group results is not really the original demand value, but rather the multiplier applied to the original value. The reason for this is because we could define the original demand value in a few different ways if we wanted. The original demand value could be an average of all the field data sets that you have or it could be simply be the baseline demand or it could be based on just the first field data set demand. At the time this module was written it was determined that we'd use the last reported field data snapshot. 

*Note: This only applies to demands, since they can vary per field data set, whereas roughness and status have unambiguous original values that apply for all field data sets.

See Also

Using Darwin Calibrator

How do I match the results I am getting from Darwin Calibrator in my model?


  • Created by
  • When: Tue, Jun 23 2015 5:58 PM
  • Last revision by Bentley Colleague
  • When: Wed, Apr 12 2017 11:27 AM
  • Revisions: 9
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