Projecting long-term hydrological changes in the Qinhuai River basin under CMIP6 climate scenarios

Understanding future hydroclimatic changes is essential for managing water resources in rapidly developing basins. This study used projections from six CMIP6 global climate models to explore four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, and SSP585) for China’s Qinhuai River Basin. The models were bias-corrected by quantile mapping and coupled with the Soil and Water Assessment Tool (SWAT) to project climate and runoff/streamflow. By 2100, temperature increases by 1.6°C under SSP126 to 5.6°C under SSP585, with the fastest warming rate (0.5°C per decade) in SSP585. Annual precipitation increases by 8.3–10.4% under SSP126/SSP245 and by about 10% under SSP370/SSP585 for 2081–2100. Multi-model ensemble projects increases in both precipitation and runoff; SSP370 shows the largest trend, with precipitation rising 2.5 mm/year and runoff 0.96 mm/year. Probability density analyses indicate the highest mean annual discharge (82–83 m³/s) occurs in the 2080s across all scenarios, while the largest variance appears in the 2060s under SSP126 (79.2) and in the 2080s under SSP245 (79.0). These patterns underscore complex interactions between climate change and socioeconomic pathways. The ensemble approach captures overall responses and helps reduce uncertainty. Further validation with long-term observations is encouraged to strengthen pathway-specific impact assessments and support integrated water-resources management.