[madgeogr]

Hi,
I have recently started reading about porous media, and particularly single and double porosity models. I have seen that these models use either a transport equation for water content (θ) or pressure head (h). In case the pressure head (h) is calculated, I found several empirical expressions, obtained from the retention curve, which can be used to calculate the water content. These expressions are non-linear expressions, thus it makes me wonder: how do you calculate the water content in case we know the pressure head. Do we use the same expressions? And if yes, are we solving inversely these non-linear expressions?
Thanks for your time