Evolution of Water-Sediment Situation and Attribution Analysis in the Upper Yangtze River, China

River water and sand conditions are important factors affecting river morphology, biogeochemical processes and ecosystems. However, climate change and long-term human activities have changed the water-sediment conditions of rivers. This study combines the ecohydrological indicator range of the variation approach (IHA-RVA) and the genetic planning approach in order to dissect the water-sediment situation and its ecological response relationship in the upper Yangtze River. The synergistic effects of climate change and human activities on sediment-runoff were quantified based on the Budyko hypothesis and the sediment attribution decomposition method. The results showed that the interannual trend in sand transport decreased significantly compared to the runoff at each station in the upper Yangtze River, and that it began to change abruptly in 1985 and 1993, respectively (mean values of 56.8% and 70%, respectively); there were also different degrees of decreases in fish species diversity attributed to the combined effects of reduced rainfall and reservoir construction. The factors driving changes in watershed runoff were dominated by human activities (approximately 60%), while changes in sand transport were mainly driven by the sand production capacity in the watershed, both of which contributed more than 95%. The research process and results contribute to an in-depth understanding of the characteristics and driving mechanisms of river water and sand evolution under changing environments, and provide a scientific basis for watershed water resource management and ecological restoration.