Characteristics and Driving Factors of Runoff Variation in the Han River from 1960 to 2020

Understanding the evolution of runoff and precipitation and their relationship is essential for interpreting hydrological processes and managing water resources. Based on observed precipitation and runoff data from 1960 to 2020 in the Han River Basin, this study applied trend analysis, persistence analysis, abrupt change detection, and wavelet analysis to characterize the temporal variations of precipitation and runoff. It used the double mass curve method to quantify the contributions of precipitation and human activities to runoff changes. The results show that both precipitation and runoff fluctuated over time. Precipitation exhibited no significant trend over the 61 years, whereas runoff showed a significant decreasing trend, and persistence analysis indicates that this declining tendency will continue in the future. Runoff displays clear periodic characteristics, with a dominant cycle of 36–38 years and a secondary cycle of 13–14 years. No abrupt change in precipitation was detected, whereas runoff showed an abrupt change in 1990. Attribution results reveal that the reduction in runoff during 1990 to 2020 was mainly driven by human activities, with contribution rates of 85.1–90.1%, whereas precipitation contributed 9.6–14.9%. This study provides scientific support for water resources regulation in the Han River Basin.