In the course of membrane usage for the filtration, the amount of water contained in its pore should have effect at least on morphology, functionality and modification...
I didnt understand your question? what do you mean by water content of the membrane? is it about membrane porosity?
Gravimetric analysis is the most conventional method for measuring membrane porosity. you can determine the weight of the water adsorbed by a volume of the membrane. you just need to determine membrane thickness, area, wet and dry weight.