Fig. 1. Plots of Russo's model of effective saturation vs. pressure head for Mualem's parameter m = 0.5 in Eq. [13] (left), and the shift in the matric flux potential caused by a non-zero background effective saturation (right). The cross is for a soil in which effective saturation before infiltration is S_e0 = 0.75; The corresponding shift relative to the analytic expression of in Eq. [11] is ₀ = 0.11K_S/ (for m = 0.5).