Abstract:Soil hydraulic parameters are critical to the numerical simulation of land surface processes such as soil moisture and pollutant transport. This study aimed to explore the spatial variation characteristics and influencing factors of soil hydraulic parameters, and then simulated these parameters through indirect method in classic cultivated area. A total of 124 sampling sites were set up in the Guanzhong Plain area, and undisturbed and disturbed soil samples at the depth of 0-20 cm were collected separately at each sampling site. Soil retention curve was estimated by the van Genuchten (VG) model and the hydraulic parameters (i.e. θr, residual water content; θs, saturated water content; α and n, shape coefficients) of the VG model were calculated. Classical statistics, geostatistical and structural equation methods were used to determine the spatial variation characteristics and influencing factors of θr, θs, α and n, and the prediction model of hydraulic parameter pedo-transfer functions was established. The results showed that the variability of n and θs was weak and moderate, respectively; while θr and α had strong variability. Semi-variance functions of θr, θs, α and n could be best fitted by the spherical model, the exponential model, the exponential model and the spherical model, respectively. θs and n exhibited strong spatial dependence, with the range of 32.7 and 54.3 km, respectively. θr and α exhibited moderate spatial dependence, with the range of 52.8 and 52.8 km, respectively. Soil texture, bulk density, pH, organic matter and elevation were the main direct factors affecting soil hydraulic parameters. The pedo-transfer functions model of hydraulic parameters based on soil physical and chemical properties and elevation had good simulation effect, and could be used to simulate and predict soil hydraulic parameters of large-scale farmland ecosystem in the Guanzhong area.