Abstract: Understanding the influencing factors of runoff changes and quantifying their contributions are important for regional planning and rational utilization of water resources. In this paper, a linear regression method, a five-year moving average method, and rescaled range (R/S) analysis method were used to illustrate the variation patterns of hydrological elements in the Ju River basin. The Mann-Kendall mutation test and an ordered clustering method were used to determine the years when sudden changes occurred in the runoff series at the Huangling Station. Then, the runoff series is analysed by using a complementary relationship method based on Budyko's hypothesis, combined with the Slope Change Ratio of Accumulative Quantity (SCRAQ) method. The results show that over the period of 1967-2019, the mean annual precipitation in this basin was on the rise, the annual potential evapotranspiration and annual runoff depth were on the decline, and the annual amount runoff changed abruptly in 1985. The contribution of climate change to runoff change in the Ju River basin was 24.04% and 11.71% by the two methods, respectively, and the contribution of human activities was 75.96% and 88.29%, respectively. Intense human activities such as water conservation measures and coal mining were the main drive of runoff reduction in the basin.

Key words: Ju River basin, climate change, human activities, attribution analysis, runoff change, Budyko hypothesis, SCRAQ method