Falk,
If setting all slices to 'Phreatic', FEFLOW will consider the storage parameter drain-fillable porosity in ALL these layers, not only in the one the water table is currently in. Therefore this solution is definitely wrong. The reason the setting can be done in this way is that FEFLOW - with some restrictions - also supports setups like this:
- phreatic
- fixed
- phreatic
- fixed
This would respresent a system with two phreatic surfaces in layer 1 and 3, with a fully saturated aquitard in between. Practically, however, in such cases a fully unsaturated solution might be the better choice.
Peter