Quantifying the magnitude of the impact of climate change and human activity on runoff decline in Mian River Basin, China

摘要

Runoff in North China has been dramatically declining in recent decades. Although climatenchange and human activity have been recognized as the primary driving factors, the magnitude ofnimpact of each of the above factors on runoff decline is still not entirely clear. In this study, MiannRiver Basin (a watershed that is heavily influenced by human activity) was used as a proxy tonquantify the contributions of human and climate to runoff decline in North China. SWAT (Soil andnWater Assessment Tool) model was used to isolate the possible impacts of man and climate.nSWAT simulations suggest that while climate change accounts for only 23.89% of total decline innmean annual runoff, human activity accounts for the larger 76.11% in the basin. The gap betweennthe simulated and measured runoff has been widening since 1978, which can only be explainednin terms of increasing human activity in the region. Furthermore, comparisons of similar annualnprecipitation in 3 dry-years and 3 wet-years representing hydrological processes in the 1970s,n1980s, and 1990s were used to isolate the magnitude of runoff decline under similar annualnprecipitations. The results clearly show that human activity, rather than climate, is the mainndriving factor of runoff decline in the basin.