You can measure the hydraulic conductivity in a laboratory. By definition, hydraulic conductivity relates to fresh water (permeability normilized for the unit weight of fresh water). For the permeability of saline water, you'd have to adjust for density.
Choice 2: Just do a pumping test or a slug test and take a direct field measurement. Figure that in the fresh water environment you'd measure the water flow through porus media for fresh water and in the saline environment - for saline water. I'd bet you're talking of some slight variation. The bigger factor in this whole equation is stratification from the varying densities. I bet if you did a perm test in the laboratory using fresh water and then using saline water (standard normailzed ocean water - SNOW) you wouldn't see a great difference. That said, you know that the density effects with respect to layering are a different matter.
Just some initial thoughts. . . .
f-d
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