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Niklas Jannok

SFR2 not working with MODFLOW 2005

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Hello,

I have inherited a MODFLOW-model, with a complex stream network defined with the SFR2 package. The model checker reports that many of the stream segments have the error "ELEVUP or ELEVDN is below a cell bottom elevation...". The original MODFLOW model uses MODFLOW 2000, which reported the error, but would run regardless. However, when the version is changed to MODFLOW 2005, the model terminates with error due to "reach altitude error" (as written in the .out file). It is important that the model can run with MODFLOW 2005.

Is there a way I can force MODFLOW 2005 to run the model despite the reach altitude errors, (like MODFLOW 2000 apparently can), or do I need to change the stream elevations?

Any insight would be greatly appreciated.

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Hello Niklas Jannok,

I do not know how many errors do you get when you run the Model checker, but if the number is not very large, you can manually  modify the bottom elevation of the cells that cause the errors. 
But it is recommended not to change the stream elevations.

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Hi Khaled, thanks for input,

Altering the cell bottoms is unfeasible due to the number and size of the errors; It would compromise the geology of the model too much.

I am still wondering if there is a way to force MF2K5 to "ignore" the errors like MF2K apparently can.

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Hi Niklas,

I have encountered similar problem with MODFLOW-NWT. After an update MF-NWT started to report head below cell bottom error and a model that run ok with previous version was terminated due to this. I solved it by increasing the head slightly as it was only a very small difference. My point is that MF developers added a check module that was not in the old version and you are probably strugling with something similar. MF2K5 being smarter in finding the errors then MF2K (or the SFR2 module). As the best option of fixing the errors is not feasible, you could try looking into MF2K5 change log and maybe try to use older version of MF2K5 that may not contain the check. Or you could disable the check module in the SFR2 source code and recompile MF2K5 yourself. It is a matter of compiling MF2K5 with ICHKSTRBOT_MODULE located in gwf2sfr7.f modified accordingly. Just be aware that you may get incorrect solution as the check has its purpose.

Edited by Michal

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