Does coal mining exert a greater influence than vegetation restoration on streamflow variation? Evidence from the Loess Plateau, China

The streamflow change within the Loess Plateau is of great importance, given its complex driving mechanisms and diverse human activities. While it is widely recognized that human activities play a crucial role in impacting streamflow in this region, the specific contributions of each sort of human activity remain poorly understood. This is especially true for the coal mining since this process is particularly difficult to quantify, and thus, it remains unknown whether it is more important than another widely studied process—vegetation restoration—in streamflow changes. Here, we further improved our newly-developed model (SIMHYD-PML) by incorporating the groundwater seepage, thereby allowing it to explicitly depict the impacts of coal mining and vegetation restoration on streamflow changes. Using two typical basins in the Loess Plateau as examples, three modeling scenarios—vegetation change and coal mining, vegetation change without coal mining, and a non-impact scenario—were implemented to assess whether coal mining contributes more to streamflow changes than vegetation change. Our results show that increased groundwater seepage due to coal mining and enhanced evapotranspiration due to vegetation restoration are indeed two key factors contributing to the streamflow reduction in both basins. Specifically, from 2000 to 2020, coal mining accounted for 58.6 %–63 % (6.3–12.3 mm yr⁻¹), and vegetation restoration accounted for 37.0 %–41.4 % (4.5–7.2 mm yr⁻¹) of the total streamflow reduction. This suggests that coal mining has a greater impact on streamflow processes than vegetation restoration, making it the primary driver of streamflow changes in both catchments. This study enhances our understanding of the impacts of coal mining on streamflow, offering valuable guidelines for water resource management in regions heavily dependent on coal resources.