The applicability of HYDRUS-1D to infiltration of water-repellent soil at different depths

HYDRUS-1D has been extensively applied to the simulation of wettable soil infiltration, but very few studies have explored its applicability to the infiltration of water-repellent soil (WRS) at different depths. To this end, HYDRUS-1D was used to simulate water movement of layered soil with a surface repellent thickness of 10 cm. The parameters of the van Genuchten model were calibrated and validated using cumulative infiltration (CI), distance of the wetting front (Z(f)) and volumetric water content (theta(v)) through five respective treatments. Another 10 tilled scenarios were selected to simulate water movement of tilled WRS. RRMSE (relative root mean square error) and CRM (coefficient of residual mass) were adopted to evaluate simulation accuracy. For the calibration and validation, the RRMSE values ranged from 0.04 to 0.251 and 0.042 to 0.101, respectively, indicating that HYDRUS-1D could effectively simulate water movement of WRS. Furthermore, for layered treatments, the simulation accuracy of theta(v), CI and Z(f) decreased with the increase of the degree of repellency and thickness. The treatments with the repellent thickness of 10 cm had higher simulation accuracy than that with repellent thickness of 5 cm when the top layer had the same WRS. The results revealed HYDRUS-1D was effective in the simulation of water movement in repellent clay loam with different degrees of repellency and depths. Highlights The applicability of HYDRUS-1D to the infiltration of water-repellent soil (WRS) at different depths was explored. The simulation of different degrees of repellency and depths was first conducted. Simulation accuracy decreased with the increase of degree of repellency and thickness. HYDRUS-1D was effective in simulating water movement of repellent soil.