Water transport process and simulation of layered soils with different configurations in an arid region

The mining area in northwest China is located in the arid and semi-arid zone, in which the surface water resource is sparse and the ecological environment is fragile. Coupled with the exploitation of mineral resources, the land has been degraded seriously. How to realize the efficient reclamation of soil and the effective utilization of soil water is an urgent scientific and technical problem. In this study, the layered soil with different configurations is set up for water transport and infiltration test to monitor the moisture changes in the soil profile. Hydrus-1D is used to simulate the rainfall infiltration process and reveal the water transport characteristics of layered soil from three aspects: soil moisture, water potential and water flux. The scenario simulation is conducted based on the optimized model to explore the effect of interlayer characteristics on shallow soil water. The results show that the interlayer significantly changes the distribution and transport of soil water, and the soil water potential is continuously distributed at the interlayer interface, while the soil water abruptly changes at the interlayer interface. Although loess interlayer and weathered sandstone interlayer both block the infiltration of soil water, the principle and the source of water increase are different. The former is the retention of soil water above the interlayer due to

the poor permeability of loess, while the latter is the retention of water above the interlayer due to the small matrix potential of the coarser interlayer. According to the results of the model, it is suggested that setting loess interlayer of 20 cm thick at the depth of 40 cm of aeolian sand is conducive to increase soil moisture above the interlayer for vegetation utilization. Summarily, the results can provide a theoretical basis for understanding and mastering the layered soil hydrological process in arid regions and optimizing the soil reconstruction mode in the process of land reclamation and ecological restoration.