Follow-up on SWAT+ gwflow setup, calibration approach, and executable behavior
MR. BONTHA SAI KIRAN
Dear Dr Bailey and Nancy,
Thank you again for sharing the updated executable and the modified gwflow.input file.
I wanted to update you on the results after implementing the changes.
I used:
The updated gwflow.input file (with the write flag modification),
The new executable (SWAT+.exe),
The gwflow_obs_head file has the observation cell_ids properly defined.
The groundwater head outputs are now being generated correctly (including gwflow_obs_head). However, I observed a significant issue with streamflow simulation.
After running the model with the new executable, the simulated discharge values (flo_out in channel_sd_mon.csv) at the reaches corresponding to the observed gauge stations do not even closely match the observed discharge values, and I am getting minimal response in the form of streamflow, i.e., streamflow values at all time steps are nearly zero.
In contrast, when I use the older executable (SWAT+gwflow_60.5.3.exe):
The model does not generate gwflow_obs_head with observation cell_ids,
But the simulated discharge values match the observed discharge reasonably well.
For reference, I have attached comparison plots:
Pictures 1, 2, and 3 – Simulated vs Observed discharge using the old executable
Pictures 4, 5, and 6 – Simulated vs Observed discharge using the new executable
As shown in the plots, the new executable yields very poor NSE values (negative at all three stations), whereas the old executable produces reasonably acceptable agreement.
Could this discrepancy be related to:
Differences in how gwflow is coupled internally in the new executable?
A required additional input setting when enabling gwflow_obs_head?
Are there any changes to default parameter handling between executables?
I would greatly appreciate your insight on this behaviour. I want to ensure I am using the correct configuration before proceeding with multi-objective calibration
Thank you very much for your time and guidance.
Best regards,
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