Over the past three decades, China’s coal production has undergone a strategic westward shift. Several important coal production bases are now located in ecologically fragile, arid regions. The surface subsidence caused by large-scale coal mining could adversely affect these vulnerable ecosystems. To understand this impact, this study investigates the moisture migration process and evaporation losses of fissure-filled soil moisture in semi-arid mining areas. We collected fissure-filled and undisturbed soil samples from depths of 0-300cm, analyzed their structure and soil moisture content (SMC), and used hydrogen and oxygen stable isotopes ( \(\delta ^2 H\) and \(\delta ^{18} O\) ) to trace soil moisture infiltration and evaporation processes. This study revealed distinct structural differences between fissure-filled soil and undisturbed soil layers. Fissure-filled soil received more precipitation recharge, resulting in higher moisture content in deeper layers. Conversely, the shallow layer of fissure-filled soil experienced stronger evaporation. Consequently, the evaporation loss rate within the fissure-filled soil in the 0-180cm depth range was 10-20% higher than that of the undisturbed soil. The results show that after the tension fissures in the coal mining subsidence area are filled, fissure-filled soil texture changes, the deep soil moisture content increases, and the evaporation in the shallow layers are intensified. This leads to more frequent and severe soil dry-wet cycles within fissure-filled soil. Furthermore, the fissure-filled soil exhibits enhanced water recharge capacity, suggesting its potential as a hotspot for ecological reclamation in arid mining regions.
