Former model results from 2020 not reproducible

[ako_tde]

Dear all,

a colleague and myself use GMS now and then for small applications. Both of us know GMS only by completing tutorials and self-teaching.

However, we are stuck and can not explain following observations:
- In May 2020, my colleague built and used a small model to forecast depression cones and catchment areas of 3 wells. The results were as expected and reasonable (please see Pic_1_Head_2020).
- Roughly 2 years later in February 2022, we used the exact same model to verify our results from 2020 and to apply different pumping rates.
=> However, we get different results and it seems that one well is not active (please see Pic_2_Head_2022). This inactive well was validated by checking the flow budget.

We didn't change anything in the model, just copied it by copy&paste of the .gpr-File and also with the "Save as" option within GMS.

Of course we double checked all parameters and settings in the model, including disabling the MNW2 package and remapping the wells into the model again. But somehow it seems that the results of 2020 can't be reproduced.

Is there anything that we might have overlooked?

Our recent Version of GMS is 10.5.6 (64-bit), Build Date: Jan  6 2021. We are not sure which version of GMS was used back in May 2020. Could this be the issue? Is there a way to read the former GMS version within the old MODFLOW files?

Thanks in advance for any hints or suggestions.

Kind regards,
Alexander

 

[Sean Czarniecki]

Just seeing this now (haven't checked in for a little while.  Check the MODFLOW version/build being used (look in your output files).  I ran into this one time, where my model converged with a slightly older version, but not with the most recent - the MODFLOW developers made a change that impacted things.  It wasn't that either solution was incorrect, but because one handled dry cells differently than the other, one worked and the other didn't.  This change that I ran into occurred back around 2018.  I had to drop the older version of MODFLOW into a location on my hard drive and change GMS to look for that version of MODFLOW rather than the most current that it defaults to.