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Todd Wood

add SFR observation process in MODFLOW

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The user is interested in this because they would like to plot groundwater gains and losses for arc groups in the map module while using the SFR package. This is currently possible with the STR package, but not the SFR package.

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Adding this to MODFLOW would require creating a package in the MODFLOW code for SFR observations. I am actually surprised that the USGS does not have this package yet.

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On another note, with MODFLOW-USG, we use a PEST utility to do the flow observation calculation. This utility goes straight to the CCF output file so SFR flows can be used with MODFLOW-USG.

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Hi Alan.  Is it currently possible to use PEST to calibrate to river flows calculated via the SFR2 package while running a MODFLOW-USG model within GMS?  Or does your above comment refer to running PEST and MODFLOW-USG outside GMS?  Thanks.

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My comment above means that the utility used to do flow calculations is external to MODFLOW and it has the capability to get SFR flows (to/from aquifer [leakage]). I just tried doing this in GMS with a SFR tutorial file and it looks like we don't allow observed flows to be entered (since the other versions of MODFLOW do not support it).

I can add a feature request to enable entry of observed flows with SFR if you like? They would only work with MODFLOW-USG models.

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Thanks Alan.  Adding that as a feature request would be great.  Calibrating to aquifer leakage (to/from the SFR2 package) or to river flows directly (or preferably to both) would make a big difference reducing non uniqueness.  And within the GUI makes things so much easier.  We can currently view leakage and river flows from the SFR2 package within GMS (via the CCF and CCF2 output files), so presumably it wouldn't take too much effort to add these as calibration data sets.  The STR package currently permits automated calibration (within GMS) to aquifer leakage.

Within MODFLOW-USG would be fine.  Having said that, I'm having problems mapping the SFR2 package to MODFLOW-USG.  I've emailed support, but they have been very busy recently.

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I will add the feature request.

Let me clarify that we have not done anything with flows in the streams themselves (CCF2 outputs). I am not sure what would be involved in doing that, but it would be significantly more work that the flows between the aquifer and the stream.

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