Abstract:In order to research the migration mechanism of the surface ponding infiltration, the HYDRUS software was used to simulate and verify the process of surface ponding infiltration based on Darcy law and mass conservation principle. The relationship between the ratio of horizontal wetting front to vertical wetting front and soil hydraulic parameters (air-entry suction, shape coefficient and saturated water conductivity) was analyzed, and a horizontal wetting front migration model was established by using soil saturated diffusion rate. The results showed that the shape of wetting pattern of fine soil was approximately an ellipsoid with the center at ponding center, and the vertical and horizontal wetting fronts were the long and short semi-axes, respectively. However, the center of the coarse soil wetting pattern was located below the ponding center, thus the short semi-axis was larger than the horizontal wetting front, and the long semi-axis was smaller than the vertical wetting front. Wetting front ratios of fine soil was changed little with time and can be assumed as a constant. There was no significant functional relationship between wetting front ratio and shape coefficient or saturated water conductivity, but it was linearly increased with the increase of air-entry suction with R2=0.999. The power function of infiltration time can be used to describe the wetting front migration and the coefficient and index in power function can be estimated by the first and second polynomials of soil saturated diffusivity. It was verified that wetting front model had a good effect within the allowable error range. The research result can provide a more rational tool for the analyzing of surface ponding water migration. Meanwhile, it also provided a scientific theory for design of drip irrigation system in arid and semi-arid regions in northern China and improving the agricultural irrigation water use efficiency.