Which slice for hydraulic head BC ? (Multilayer model)

Hi everybody,

I've some questions and I would be very grateful for some explanations !

I’m modeling a multilayer fully confined model (for each layer, different porosity, conductivity, etc) and I need to input the hydraulic-head boundary conditions (also different for each layer).
So my question is simple: on which slice should I implement the hydraulic-head boundary conditions : Top of the layer, bottom of the layer, both ? And for the final slice, should I put boundary conditions to ?

I think that’s a begginner's question but (unfortunatly ?) I was a ModFlow user before so for the moment I can not figure out the slice’s phylosophy of FeFlow !

Thanks a lot  ;)

Ps : I'm using FeFlow 7.0

Indeed the way of thinking is a bit different in between MODFLOW and FEFLOW... There's no unique answer to your question, but in a general system of aquifers and aquitards I'd put the aquifer head bcs to both top and bottom of the aquifer. If there's no clear separation, but rather a system of layers of slightly differing hydraulic conductivities, I'd typically tend to use the condition of the higher conductive layer a slice belongs to. And - yes - I'd also put a BC to the bottom layer.
In all cases you should keep in mind where your BC data come from to judge where to best put them. In an ideal world, vertical discretization would be fine enough to render the influence of the slices separating the geological units negligible - but the world (or the model) is never ideal as we all know.

[quote author=Peter Schätzl link=topic=21856.msg28804#msg28804 date=1582122270]
Indeed the way of thinking is a bit different in between MODFLOW and FEFLOW... There's no unique answer to your question, but in a general system of aquifers and aquitards I'd put the aquifer head bcs to both top and bottom of the aquifer. If there's no clear separation, but rather a system of layers of slightly differing hydraulic conductivities, I'd typically tend to use the condition of the higher conductive layer a slice belongs to. And - yes - I'd also put a BC to the bottom layer.
In all cases you should keep in mind where your BC data come from to judge where to best put them. In an ideal world, vertical discretization would be fine enough to render the influence of the slices separating the geological units negligible - but the world (or the model) is never ideal as we all know.
[/quote]

Okay I understand better now, and yes always keep in mind where the data come from...
Thank you very much for this clear and quick answer, it is very useful to me !