MODFLOW 6 GWT ICBUND Equivalent

[mgozdor2]

In MT3DMS we used icbund to block off areas where we didn't want transport calculations to occur. Is there something similar in GWT or do we just set all transport parameters, initial concentrations, and sources to zero outside our area of interest?

[aprovost-usgs]

@mgozdor2 Allowing different models (such as a GWF and a GWT) in the same simulation to have different active domains -- different IDOMAIN arrays -- is on our radar for consideration (#1129; https://github.com/MODFLOW-ORG/modflow6/wiki/MODFLOW-Development-Plans), although there is currently no timetable for adding this feature. In implementing it, we would want to look beyond just GWT and consider the ramifications for GWE and PRT models, as well. A workaround such as the one you suggested might successfully "zero out" the concentration solution outside the region of interest, but I don't think it's likely to save much in terms of run time, since some sort of transport calculations will still occur there.