Quantifying the relative contributions of climate change and human activities to runoff and sediment load variations: a case study of the Yellow River Basin in Gansu Province, China

The variation laws of runoff and sediment load under different climate, vegetation, and human activity scenarios are significantly different. Exploring the impacts of climate change and human activities on runoff and sediment load dynamics can provide a profound understanding of the mechanism of runoff and sediment load variability in basins, which is crucial for the sustainable development of regional ecosystems. This study investigates the Tao River Basin (TRB) on the Tibetan Plateau, as well as the Zuli River Basin (ZRB) and Jing River Basin (JRB) on the Loess Plateau, to differentiate the impacts of climate change and human activities on runoff and sediment load dynamics. The runoff and sediment load of the three watersheds have shown a decreasing trend over the past 40 years, and combined with the DMC (Dual mass curve) method, it was found that the slope of the runoff sediment gradually tends to flatten out. After the time period was divided, the CA (Cumulative anomaly) method was used for verification, which revealed good correspondence between the two before 2000 and then gradual deviations. The power function best represents the relationship between runoff and sediment load. During the initial period, climate had a significant impact on runoff variation in the TRB and JRB, with contribution rates of -54.93% and -63.02%, respectively. In the later period, human activities became the dominant influence, contributing more than -60% of the runoff variation. In the ZRB, human activities consistently dominated runoff variation, with contribution rates of -72.72% and -55.66% during both periods. In the early stages of research, the impact of climate change on sediment load was more severe in the TRB and JRB, and human activities played a significant role in the later stages. However, in the ZRB, human activities have always been the main contributor. Based on the actual local situation, runoff and sediment load in the TRB are influenced primarily by engineering measures, and vegetation and check dams exert greater impacts on the ZRB and JRB. This study explores the attribution of water and sediment load changes in different ecological geographic regions from a comparative perspective, providing a valuable theoretical basis and reference for understanding global runoff and sediment transport changes in similar areas.