Dynamic Simulation of Soil Salt Transport in Arid Irrigation Areas under the HYDRUS-2D-Based Rotation Irrigation Mode

Abstract

This research aims to explore the dynamic transport of water and salt in soil under different irrigation modes and disclose the desalting effect of different irrigation factors in inland arid irrigation areas. Jingdian Irrigation District in Gansu Province, which is located in the arid region of Northwest China, is selected as a typical experimental area. Soil water and salt dynamic migration model is constructed based on HYDRUS-2D software, and field irrigation experiments are designed according to actual irrigation conditions in crop growth period. The model is used to simulate the salt transport process between saturated soil and unsaturated soil as well as the effects of different irrigation quotas, irrigation rounds and quota allocations on soil desalting. Through simulation, the vertical movement pattern of water and salt in the soil of the test area is analyzed, and the optimal design of the soil desalting irrigation plan is carried out. The results demonstrate that: after two-round irrigation, the average soil salinity of the tillage layer at each test points decreases significantly under evapotranspiration; the infiltration of irrigation water has an obvious impact on soil desalting; the deviation between the simulated and the measured value is less than 0.5%, which proves the model fitting result reliable; with fixed irrigation cycle and times, the soil desalting efficiency is higher when the irrigation quota falls in the range of 4000 ~ 6000 m3/hm2; when the first round of irrigation water only saturates the moisture content and gradually increases the irrigation quota in the subsequent rounds, it is more conducive to the dissolution and discharge of soil salinity. In summary, the results of this study can provide technical support for the protection of water and soil resources, as well as the improvement of saline-alkali land in inland arid irrigation areas.