Quantitative attribution analysis of water and sediment changes in the Lower Yellow River (1950–2022) under the influence of climate change and human activities

Hydrological processes in regional river basins are significantly affected by both global climate change and human activities. This research focuses on analyzing changes in water and sediment dynamics in the lower Yellow River (LYR) while pinpointing the primary factors driving these transformations. The study aims to evaluate the respective contributions of climate change and human interventions to water–sediment interactions, providing insights for optimal water resource and watershed management. Methods such as the Mann–Kendall test and double cumulative curves were employed to explore long-term trends and sudden changes in runoff and sediment transport. The IHA-RVA method was used to conduct a detailed quantitative assessment of water–sediment variability, while Copula functions were employed to model the probability of simultaneous abundance or scarcity of water and sediment. To conduct the attribution analysis, we employed the Budyko framework along with fractal theory to quantify the respective contributions of climate change and human activities to water–sediment variations from 1950 to 2022. The results indicate substantial reductions in annual runoff and sediment transport within the LYR during this time, with overall decreases of 53.03% in runoff and 62.81% in sediment transport. The frequency of synchronous water–sediment events ranged from 56.54% to 67.29%, while asynchronous occurrences varied from 32.71% to 43.46%. Quantitative analysis revealed that human activities accounted for 74.11%–77.02% of the observed changes in runoff and a striking 91.48%–93.63% of sediment transport reductions in the lower Yellow River. These changes were predominantly driven by large-scale initiatives such as the Green for Grain program and the construction of major hydraulic infrastructure, emphasizing the dominant role of anthropogenic interventions over climatic factors in influencing hydrological dynamics. These findings provide important theoretical insights and practical guidance for enhancing soil and water conservation measures and improving regional management strategies in the LYR.