Volumetric Budget and Percent Discrepancy
Joaquin
the model. And the help files about the percent discrepancy.
FROM THE MODEL MUSE CLASS NOTES
The progress of the model will be monitored in ModelMonitor.
ModelMonitor will display any error or warning messages and graph the
percent discrepancy in the budget. If the percent discrepancy is
larger than 1%, there is probably a problem with the model. (However,
smaller percent discrepancies do not guarantee that the model is OK.)
Close ModelMonitor when the model is done running. The listing file
will be opened in Notepad when you close ModelMonitor. You can close
the listing file.
FROM THE HELP:
Each solver has convergence criteria that control when the model
solution is considered adequate. Often the model will look at the
percent discrepancy in the water budget to determine whether the
solver criteria have been set strictly enough. If the percent
discrepancy is less than 1%, this is often considered adequate.
However, the rule can fail; Ahlfeld and Hoque (2008) report a case
where a model with a percent discrepancy in the water budget of 0.012%
was not sufficiently accurate for its intended purpose. Modelers are
advised to investigate how varying the solver parameters affects the
predictions of interest in the model rather than relying solely on the
percent discrepancy in judging the adequacy of the model.
I read the lst file from the example I made, and I cannot find all the
physical meaning of variables in the volumetric budget.
##############################################################
VOLUMETRIC BUDGET FOR ENTIRE MODEL AT END OF TIME STEP X IN STRESS
PERIOD Y
CUMULATIVE VOLUMES L**3 RATES FOR THIS TIME STEP L**3/
T
IN
---
STORAGE= 9140.0693 STORAGE= 2413.9346
CONSTANT HEAD=0.0000 CONSTANT HEAD=0.0000
WELLS= 0.0000 WELLS= 0.0000
TOTAL IN= 9140.0693 TOTAL IN= 2413.9346
OUT OUT
--- ---
STORAGE= 0.0000 STORAGE= 0.0000
CONSTANT HEAD= 0.0000 CONSTANT HEAD= 0.0000
WELLS= 9538.5605 WELLS=2592.0000
TOTAL OUT = 9538.5605 TOTAL OUT = 2592.0000
IN-OUT= -398.4912 IN-OUT= -178.0654
PERCENT DISCREPANCY = -4.27 PERCENT DISCREPANCY = -7.11
##############################################################
The conditions of the model are:
No constante head boundaries
No vertical recharge
No rivers
No lakes
It means, an isolated box. The only boundary is provided by a well at
the center of the grid.
I don't know what's the physical meaning of some variables in the
budget.
The things I understood (are the easiest):
Percent Discrepancy
In-Out-
Total Out - the sum of all outs.
Total In - the sum of all entries.
IN - CONSTANT HEAD - Water volumen that enters from a constant head
boundary.
IN - WELLS - Water volume that enters from injection wells.
IN - STORAGE - ???????? I DON'T KNOW WHAT IS IT.
OUT - CONSTANT HEAD - Water volume that exits through a constant head
boundary.
OUT - WELLS - Water volume that is extracted with wells.
OUT - STORAGE - ???????? I DON'T KNOW WHAT IS IT. Maybe it is the
water volume relased from the Specific storage, for example in a
confined aquifer?
Can someone give a hand to understand these things?
Thank you very much.
Giovanni Firmani
You have a storage in and a storage out component because you are
running a transient simulation. If your were running a steady state
simulation Storage in=Sotrage out= 0.
To understand the meaning of Storage I would suggest you to review the
governing equation for groundwater system.
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An Ho Antonio Taylor
In addition to that, the calculation of storage depends of which package are using, there is a difference among LPF and BCF,in the BCF the term of storage is given, be side of calculation of T, if is convertible (LPF) or Confined, and depends by the initials heads (not the constant boundary heads) puts in your model,