Attribution of sediment load variations to climate and human activities across multiple timescales in the source region of the Yangtze River, China

Study region The source region of the Yangtze River (SRYZ) Study focus Differing from traditional research that typically conducts attribution analyses on an annual scale, this study quantified the relative contributions of climatic and anthropogenic influences at both seasonal and interannual scales in the SRYZ, using the Mann–Kendall (MK) test and the Slope Change Ratio of Cumulative Quantity (SCRAQ) method. New hydrological insights for the region Our results indicated increasing trends in annual sediment load (3.77 ×10⁴ t/a), precipitation (1.06 mm/a, p < 0.01), and evapotranspiration (0.65 mm/a, p < 0.001) in the SRYZ. These upward trends were also evident at the seasonal scale, with the most significant change occurring in spring. Attribution analysis indicated that sediment load variation in spring was co-driven by precipitation, evapotranspiration, and human activities, with contribution rates of 67.29%, −80.28%, and 112.94%, respectively—greater than their influences at the annual scale (37.77%, −29.03%, 91.26%). These findings further highlight the intensified hydrological processes in alpine regions in spring. However, human activities were the predominant driver in summer and autumn, with contribution rates of exceeding 85%. Overall, human activities and precipitation promoted sediment load increase, whereas evapotranspiration counteracted this effect. The combined influence of these three factors ultimately determined the overall trend in sediment load dynamics.