Correct me if I am wrong, but I understand that van Genuchten characteristic curves, while realistic and commonly used, present difficulties in practice. They are highly non-linear, which means that a fine spatial scale is required to achieve convergance and/or good solutions. Vogel & Ippisch (2008) Estimation of a critical spatial discretization limit for solving Richard's Equation at Large Scales. Vadose Zone Journal 7(1) 112-114. So how do people handle this?