Hydraulic head BCs

Hello,

For a coastal aquifer, you put for each slice of the coastal boundary value for hydraulic head BCs?
Or just on slice near the top??
For example my model is like a square with 2 coastal boundary and 16 slices, one no flux boundary and a fluid flux BCs. In a first time, i put hydraulic head BCs = 0 only on the first three slice (from the top).  Then i put hydraulic head BCs = 0 for the 16 slices.
I am trying different way for these limits but i don't find the solution yet.

Regards,

Terry

By applying the same head along the border of all slices, you stipulate that there is no vertical gradients between your layers. In a lot of cases it is not the case, e.g. when aquitard and aquicludes separate different conductive formations.

Ok but there is a gradient just because of the salt, isn't it ?
Whitout salt you have the same head on a vertical.
Is your answer explain the fact that for confined aquifer whith lot of pression you may have bigger head than an unconfined aquifer above? like an "nappe artésienne" in french.