Coal mining impacts on catchment runoff

Coal mining could cause drastic drop of groundwater level, obvious decrease of river base flow and total runoff in dry season. In addition, the subsidence of coal mine goaf, and water-conducting fissures also could cause the loss of surface water. How to quantitatively estimate the impact of coal mining activities on runoff there becomes a major challenge. This study focuses on the Kuye River catchment, a major coal mining region in China, where accumulative anomaly analysis, the ordered clustering and the Pettitt test are carried out. Two abrupt change points are identified in 1979 and 1997. Therefore, three stages are divided: pre-1979 (minimum human activities), 1980-1997 (the soil and water conservation) and 1998-2017 (the joint impacts by soil and water conservation and coal mining). The effects of coal mining on runoff are further estimated using SIMHYD-PML hydrological model that fully considers vegetation dynamics. Its simulation results show that from 1998 to 2017 coal mining reduced the total surface runoff by 29.35% for Wangdaohengta sub-catchment, by 55.41% for Shenmu sub-catchment, and by 49.44% the entire Kuye River catchment. The coal mine driven runoff reduction is generally large in the years and seasons with large runoff. However, the environmental impact process is not uniform. The research ideas and methods reasonably separate the impact of dividing two human activities on the runoff process, which lays a solid foundation for future research.