Influence of mining activities on hydrological processes in Pingshuo mining district, Loess Plateau: Insights from spatio-temporal variations of δD and δ18O

Under the influence of mining activities, investigating hydrological processes is an important cornerstone of water resources and eco-environment protection. In this study, the stables isotopic compositions (δD and δ 18 O) of surface water and groundwater in five periods were analyzed to identify the formation and evolution of surface water and groundwater in mining district. The δD and δ 18 O indicate that the water bodies in the study area is mainly recharged by local precipitation and undergo evaporation. There is a close hydraulic connection between surface water, mine water and groundwater, the deep confined water is affected by the surface water and phreatic water due to the developing water-conducting fractures. The recharge of deep groundwater to the overlying aquifer may increase resulting in gradually obvious “oxygen drift” with the continuous development of fractures, which will decrease the degree of “oxygen drift” as the fractures reclogged. The δ 18 O of phreatic water in each period is depleted in southeast and enriched in northwest of the study area. The δ 18 O of confined water has an obvious spatial variation in the wet season due to the combined effects of the opencast working and underground mining, and a uniform spatial variation in the dry season. The difference in spatial variation of δ 18 O between phreatic and confined water may attribute to the regeneration rate, and the stable isotopic compositions in phreatic water is easier to recover than that of confined water after mining disturbance. This finding provides important information about hydrological characteristics of Pingshuo mining district.