Effects of soil-water characteristic curve and relative permeability equations on estimation of unsaturated permeability function

Unsaturated permeability function can be estimated by theoretical models from soil-water characteristic curve (SWCC). To date, there are numerous estimation models that can be used to obtain the unsaturated permeability function from SWCC. However, each model results in a different estimation curve. The reason for this difference is not well understood. In this study, the available SWCC equations and the available relative permeability (k_r) equations were combined to form a matrix of unsaturated permeability estimation models. The matrix of unsaturated permeability estimation models was used to study the effect of SWCC equations and relative permeability (k_r) equations as controlling factors in the estimation of unsaturated permeability function. The study was conducted using twenty sets of published experimentally measured SWCC and unsaturated permeability data (k_w). The effects of the SWCC equations and k_r equations on a variation of estimated unsaturated permeability functions are presented in this paper. It was found that the SWCC equation has a more significant effect on the estimation of unsaturated permeability function than that of the k_r equation.