Attribution of runoff and sediment changes in the Wuding River Basin based on the Budyko-Kaya framework

Attribution analysis of runoff and sediment evolution, driven by the combined effects of climate change and human activities, remains a critical and complex challenge in contemporary hydrological research. This study integrated the Budyko elasticity method and the Kaya identity to quantify the contributions of climatic factors and underlying surface conditions to runoff and sediment changes, and to examine their spatial sensitivities and attribution differences. The results revealed significant declining trends in both runoff and sediment, with abrupt regime shifts identified in 1996 for runoff and in 2002 for sediment. The reduction in runoff was notably more pronounced. Runoff exhibited dominant periodicities of 41, 24, 12, and 5 a, while sediment displayed cycles of 47, 21, and 5 a. During the runoff change period, spatial heterogeneity in dominant driving factors was evident: underlying surface changes played a leading role in the upstream and central regions, whereas precipitation was the primary driver in the downstream areas. Across the entire basin, the contributions of m, P, and E₀ to runoff changes were 65 %, 27.9 %, and 7.1 %, respectively. During the sediment change period, C (45.9 %) and m (32.8 %) were the dominant factors, while the influences of P (18.2 %) and E₀ (3.1 %) were relatively minor. Following the regime shifts, increases in P, E₀, and m significantly influenced the evolution of runoff-sediment synchronicity. Enhanced precipitation led to asynchronous responses between runoff and sediment. Underlying surface factors affected the coupling relationship by modulating runoff generation and erosion, while potential evapotranspiration exerted contrasting effects on synchronicity across different periods. The study further revealed that precipitation was the dominant climatic driver of runoff and sediment dynamics, while the underlying surface modulated its influence pathways. Oceanic factors influenced periodic fluctuations in runoff and sediment by altering atmospheric circulation patterns. Regional soil and water conservation measures have effectively reduced runoff and sediment intensity, while evolving land use patterns have enhanced the basin’s regulatory capacity.