How does large-scale underground mining affect the water cycle? - Comprehensive analysis based on isotopes, water...

Large-scale underground coal mining alters regional water cycles, yet the mechanisms governing interactions among water bodies in deep mining areas are poorly understood. For this purpose, by integrating hydrogen and oxygen isotopes, water levels, hydrogeological conditions, and end-member mixing analysis (EMMA), this study systematically analyzed and quantified the circulation and transformation mechanisms among different water bodies influenced by coal mining. Key findings reveal: (1) Mining-induced fractures disrupt the aquitard above the coal seam, establishing a direct hydraulic link between Zhiluo Formation confined groundwater and mine water, with the former contributing 87.8 % to mine water recharge. (2) Shallow water systems (phreatic groundwater and surface water) remain unaffected due to a stable aquitard in the Anding Formation, with their dynamics controlled by precipitation and evaporation. Phreatic groundwater recharge depends on vadose zone conditions prior to rainfall, while its interaction with surface water is bidirectional but dominated by lateral groundwater discharge. This study significantly enhances the understanding of water cycle processes in mining area basins, and provides crucial scientific basis for water resources management, eco-environmental management and protection, as well as sustainable development of regional aquifers.