Characteristics of Soil Water Distribution and Transport in Reconstructed Dump in Grassland Opencast Coal Mine Areas of China

Soil water is a crucial limiting factor for the growth of vegetation in the grassland region. However, mining activities disrupt the balance of the water cycle in the region, further exacerbating soil and vegetation degradation. Existing studies on soil water in mining areas lack systematic analysis of surface soil evaporation and root water uptake processes. Therefore, this study focused on the Shengli mine dump in northern China and investigates the dynamic soil water transport characteristics and influence mechanism of grassland opencast coal mine through sampling and numerical simulation methods. The soil water content's coefficient of variation decreased with increasing soil depth. The 0 to 20 cm soil layer was considered the water active layer. A hysteresis effect was observed in the change of soil water content from 20 to 40 cm depth. There was a linear positive correlation between the daily root water uptake and the surface soil water content. The precipitation infiltration process was mainly driven by gravitational potential energy, while the evaporation of soil water into the atmosphere was mainly driven by the difference in air saturation barometric pressure. The main driving force of vegetation's root water uptake was the difference in water potential between the soil and the vegetation. In the future, opencast mining areas in grasslands should be reasonably designed to reconstruct soil profiles, select revegetation configurations, and strengthen dynamic data monitoring and management. This study provides a theoretical basis for the ecological environment restoration of the opencast mine in the grassland.