Attribution of streamflow changes during 1961–2019 in the Upper Yangtze and the Upper Yellow River basins

Climate change has remarkable global impacts on hydrological systems, prompting the need to attribute past changes for better future risk estimation and adaptation planning. This study evaluates the differences in simulated discharge from hydrological models when driven by a set of factual and counterfactual climate data, obtained using the Inter-Sectoral Impact Model Intercomparison Project's recommended data and detrending method, for quantification of climate change impact attribution. The results reveal that climate change has substantially amplified streamflow trends in the Upper Yangtze and Upper Yellow basins from 1961 to 2019, aligning with precipitation patterns. Notably, decreasing trends of river flows under counterfactual climate have been reversed, resulting in significant increases. Climate change contributes to 13%, 15% and 8% increases of long-term mean annual discharge, Q10, and Q90 in the Upper Yangtze at Pingshan, and 11%, 10%, 10% in the Upper Yellow at Tangnaihai. The impact are more pronounced at headwater stations, particularly in the Upper Yangtze, where they are twice as high as at the Pingshan outlet. Climate change has a greater impact on Q10 than on Q90 in the Upper Yangtze, while the difference is smaller in the Upper Yellow. The impact of climate change on these flows has accelerated in the recent 30 years compared to the previous 29 years. The attribution of detected differences to climate change is more obvious for the Upper Yangtze than for the Upper Yellow.