Buffer layers?

Hi Users,
My model contains 4 aquifers and 3 aquitards. Vertical order of these layers can be illustrated as Aquifer 1(Aq)-Aquitard 1(At)-Aq2-At2-Aq3-At3-Aq4. Aquitards are assumed to be represented in the model by a single layer between two aquifers. The thickness of these aquitards ranges from 3-20m. I am wondering that these aquitarts need to be created a buffer layer? Is it mandatory to create buffer layer and among these aquitard layers which aquitard layer shoul be created buffer layers?

I am looking forwards to receiving your ideas. Thanks in advance,
Lamm

You should use buffer layers if you are planning to either simulate solute transport, or undertake particle tracking analysis.  At each interface between an aquifer and aquitard, you should insert a thin layer with aquitard properties.  In your example, aquitards could potentially require 3 layers (thin, thick, thin).

If you aren't planning solute transport or particle tracking, buffer layers are not needed.

Thanks Blair so much,
I have a plan to simulate salt intrusion. I suppose that salt could be considered to be on kind of solute (dissolve). Thus, perhaps I must create thin buffer layer within aquitard layers according to your advice.