Projection of climate change impacts on hydropower in the source region of the Yangtze River based on CMIP6

The source region of the Yangtze River located on the Qinghai-Tibet Plateau is very sensitive to climate change. The impact of climate change on the source region of the Yangtze River has been detected from multi-aspect, but limited research has been conducted on the hydropower impact of important water system, especially for the Yalong River, which is the longest tributary in the upper reaches of the Yangtze River and rich in hydropower reserves with a value of approximately 33.72 million kilowatts. In this study, we performed statistical down scaling of 10 Coupled Model Intercomparison Project Phase 6 (CMIP6) models and used the Bayesian weighted ensemble method to analyze the Yalong River basin. The interdecadal climate characteristics of the region were analyzed and drive the variable infiltration capacity (VIC) hydrological model coupled with reservoir operation module to obtain the spatiotemporal changes in water-energy resources in the future. The results showed the precipitation in the Yalong River basin showed an increasing trend (12.38 mm/10a, 25.65 mm/10a) under the shared socioeconomic pathways 2-4.5(SSP2-4.5) and socioeconomic pathways 5-8.5 (SSP5-8.5) scenarios. Coupled with reservoir operation rules, the excess water during the wet season could be transferred to the dry season. Even so, it was estimated the overall power generation of the basin would be reduced by 4% to 6% compared to the baseline period. This change will largely affect the energy of Chongqing and Sichuan Provinces, which rely heavily on the Yalong River for hydropower generation. Our framework and research results are expected to provide useful information for other river systems in the Qinghai-Tibet Plateau and can be used to reexamine the research results of related river basins.