Variation of the hydraulic characteristics of soil profile in water-wind erosion crisscross region

Hydraulic properties of the soil profile are the precondition to accurately predict the soil moisture dynamic distribution. In this study carried out in Liu Daogou watershed in water-wind erosion crisscross region, the undisturbed soil water retention curves of the different layers of two soil profiles located at the middle and upper part of a slope were firstly measured by centrifugal method, and then the soil hydraulic parameters such as saturated water content, residual water content, the inverse of the air-entry value and a pore-size distribution index were obtained by fitting soil water retention curve to the Van Genuchten soil water retention model connected with Mualem hydraulic conductivity model. By comparison among soil hydraulic parameters of the different layers, the changes of soil hydraulic parameters in the profile were analyzed. The result shows that the four parameters change weakly along the soil profile. According to the coefficient variation of four parameters, both of residual water content and the inverse of the air-entry value belong to weak variability, nevertheless the saturated water content and the pore-size distribution index belong to medium variability. However, all of the variations of the four parameters are not significant through variance test, which proves that the soil profile of 160 cm in depth in this region can be treated as the homogenous profile.