A global meta-analysis of coal mining studies provides insights into the hydrologic cycle at watershed scale

• Published in: Journal of hydrology (Amsterdam) 2023-02, Vol.617, p.129023, Article 129023
• Main Authors: Yang, Jiahui, Wei, Huaixin, Quan, Zelin, Xu, Rui, Wang, Zhaohui, He, Hailong
• Format: Article
• Language: English
• Subjects: Coal mining; Hydrological cycle processes; Runoff time series; Soil and water conservation; Soil erosion; Watershed
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2022.129023

•A mixed effects meta-analysis of coal mining on soil and water conservation at watershed scale.•Time series of runoff was significantly decreased since the coal mining.•Coal mining increases soil infiltration.•Coal mining resulted erosion may be buffered if appropriate revegetation measures were applied. Coal mining is a critical energy industry that considerably evolves and benefits the modernization and development of our society. However, the side-effects such as degraded air and water quality, fragmented vegetation landscape, and aggravated soil erosion associated with coal mining also raise serious concerns. Previous studies have shown diverse hydrologic cycle responses after coal mining when the watershed is subjected to different magnitudes of local climates, soil properties, mining methods, and watershed area. How these factors combine to affect hydrologic cycle responses to changes in mining remains unclear. A meta-analysis including 717 paired observations collated from 62 studies worldwide was used to evaluate the effects of coal mining on soil and water loss at a watershed scale. The results showed that runoff, runoff depth, and spring flow due to coal mining were significantly decreased by 24.46 %, 32.55 %, and 56.88 %, while calculated soil erosion modulus and soil loss based on empirical equations were significantly increased by 202.44 %, and 199.50 %, respectively. As runoff is the carrying force for soil loss, the decreased runoff would actually reduce the carrying capacity of soil to enter the river system. Therefore, the increased soil loss intensity and decreased runoff may lead to insignificant total soil loss (−68.52 t hm−2). In addition, coal mining decreases groundwater level (−11.02 %) and baseflow (−14.46 %), increases infiltration rate (42.86 %), soil erodibility K value (258.67 %), sediment yield (141.86 %) and soil erosion area (102.06 %). Among them, mean annual precipitation plays a dominant role in driving hydrological cycle processes, while combined use of above-ground and underground mining tends to increase soil erosion. This study is crucial to a better understanding of soil and water conservation under coal mining activities.