Abstract
The Fayer and Durner models, which modified the water retention curve of the van Genuchten (VG) model, combined with the statistical pore-size distribution model of Mualem were used to predict unsaturated hydraulic conductivity functions of Tottori dune sand and aggregated Kumamoto Andisol. Parameters of the Fayer and Durner models, as well as the VG model, were inversely estimated with the evaporation method. The Fayer model well described unsaturated hydraulic conductivity for the dune sand reflecting pore water retention for higher water contents and absorbed water retention on the surface of soil particles for lower water contents. The Durner model was suitable to the Andisol whose hydraulic properties were strongly affected with the distinct the aggregated structure. The Mualem model can predict unsaturated hydraulic conductivity for a wide range of soil water pressure when an appropriate model is used for the water retention curve and the pore-connectivity coefficient, I is estimated. Furthermore, it was also suggested that we need to use an appropriate soil water retention function to predict unsaturated hydraulic conductivity for much smaller pressure heads than the minimum pressure head observed during the evaporation experiment.
