Abstract: Indirect subsurface drip irrigation is a new drip irrigation method, which can effectively reduce surface evaporation and improve water transport efficiency in soil. Although numerical modeling of soil water movement has become an important tool for optimizing irrigation, the predictions are often not sufficiently accurate due to the uncertainty of soil hydraulic property values. In this study, based on the laboratory data from the experiments on indirect subsurface drip irrigation, it was attempted to infer the soil hydraulic parameters by using HYDRUS-2D software. Also, the difference in soil water content distribution was numerically explored for drip irrigation devices with different specifications (diameter and height). The results showed that the HYDRUS-2D software could effectively infer the soil hydraulic parameters. The simulated soil water content and wetting distance using the inferred soil hydraulic parameters agreed well with the measured values. The differences in simulated results based on the 3 and 4 inferred parameters were not significantly different. The calculated Nash-Sutcliff model performance coefficient was 0.716 and 0.714, respectively. The irrigation device with the same permeable boundary height but different diameter had little effect on soil water content distribution around the water guide device, while the device with the same diameter but different permeable boundary height had a bigger effect on water content distribution. The results obtained in this study could provide a scientific basis for the selection of water guide device specifications and the precision management of agricultural water for indirect subsurface irrigation.

Key words: indirect subsurface drip irrigation, soil water content distribution, identification of hydraulic parameters, agricultural water management