Projected impacts of climate change on major dams in the Upper Yangtze River Basin

Dams and reservoirs are essential infrastructures for water resources development and management. However, the performance and safety of dams depend on the hydrologic regime that is altering in a changing climate. This study assessed the impacts of climate change on water availability, regulation function, hydropower generation and flood hazards for major dams in the Upper Yangtze River Basin (UYRB), under the Shared Socioeconomic Pathways (SSPs) scenarios during the twenty-first century. First, the outputs of 14 global climate models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6) for the medium (SSP245) and high (SSP585) emission scenarios were used to drive a coupled hydrological, dam and hydroelectric model. Then, changes in metrics covering dam inflow and service performance in the future relative to the historical period were quantified. Finally, climate change-induced flood hazards were investigated by extreme value analysis. Our results show that dam inflow in the basin will exhibit an overall increase in annual mean and more extremes in high and low flows. Meanwhile, hydropower generation will exhibit an increase in magnitude and interannual variability, with a marked rise in spilled water. The results also show the likelihood of experiencing a more extended high flow season, which will consequently impact the flood season with the increase in the frequency and magnitude of flood events, necessitating more prudent and optimal operating rules for the dams on the river system. Moreover, the regulation function of dams is expected to strengthen in the flood season and weaken in the dry season. These findings indicate the increasing importance of dams as a critical water infrastructure system and underline the need for existing operations in adaptation to future climate.