Evaluation and influence of coal mining on groundwater resources in arid region: A case study of Dananhu No.7 colliery, Xinjiang, Western China

The conflict between mineral extraction and water protection, especially in arid and semi-arid regions, remains a critical concern. Assessing the impact degree of coal mining on groundwater is essential for water-preserved mining practices. This study evaluates and predicts the effects of coal mining at Dananhu No.7 colliery on groundwater. We propose a ratio parameter measuring the depth of mining-induced fractures in the aquifer relative to aquifer thickness. Along with permeability coefficient, unit water inflow, and geological structure fractal, these factors assess the impact of 6# and 7# coal mining on the lower and upper sections of the Xishanyao Formation (LSXF and USXF) aquifers. Using the entropy-TOPSIS method, we assign weights to four evaluation indexes. Subsequently, we combine four thematic maps in ArcGIS to create the zoning map of damaged groundwater. The impact levels of coal mining on groundwater are classified into four levels (I-Ⅳ), from basically unaffected to serious impact. The results show that the impact levels of LSXF groundwater mainly consist of the basically unaffected, slight impact, and moderate impact levels for 6# coal mining, while the impact degree of 7# coal mining on LSXF groundwater is concentrated in the slight impact and moderate impact levels. The USXF groundwater in the coal recoverable area is dominated by the basically unaffected and the slight impact zones, without the serious impact zones. Based on these impact levels, recommendations for backfill mining, reducing mining height, and underground reservoir systems construction measures are applied to achieve water-preserved mining. The research can serve as a valuable reference for groundwater protection in water-scarce, high-intensity mining areas.