Abstract: Due to the combined impact of global climate change and human activities, extreme hydrological events in the Panjiakou Basin have become more frequent, leading to a continuous reduction in inflow, which poses a significant threat to water security in downstream regions. To explore the contributions of global climate change and human activities to extreme runoff variations, the Mann-Kendall mutation test was used to analyze the mutation years of runoff data from 1960 to 2017, thereby dividing the baseline and change periods. The SWAT model, Budyko hypothesis, and elasticity coefficient method were applied to quantitatively separate the effects of climate change and human activities on runoff. The results indicated that from 1960 to 2017, there was a downward trend in precipitation, potential evapotranspiration, and runoff depth in the Panjiakou watershed. A significant change point in the runoff series occurred in 1980. The average annual runoff depths during the baseline period（1960—1979）and the post-change period（1980—2017）were 68.40 mm and 46.79 mm, respectively. In years with abundant water, the contributions of climate change and human activities—assessed using the SWAT model, Budyko hypothesis, and elasticity coefficient methods—were 42.76% and 57.24%, 39.68% and 60.32%, 35.14% and 64.86%, respectively. In years with drought, the contributions of climate change and human activities were 30.37% and 69.63%, 37.45% and 62.55%, 35.64% and 64.36%, based on the same three methods. All three methods indicate that human activities are the dominant factor in the evolution of extreme runoff. These findings are of significant reference value for selecting appropriate methods for analyzing extreme runoff impacts, and for optimizing water resource scheduling and sustainable development in the Panjiakou Basin.

Key words: climate change, human activity, SWAT model, Budyko hypothesis, elasticity coefficient method