Future Climate Change Increases Streamflow and Risks of Hydrological Hazards in the Pearl River Basin

Understanding and predicting climate change impacts on the terrestrial water cycle is essential for water resources management and hazard prevention. This study aims to project future runoff of a densely-populated river basin, the Pearl River Basin (PRB), under different Shared Socioeconomic Pahway (SSP) scenarios, by combining the Soil and Water Assessment Tool (SWAT) model and the CMIP6 climate projections. Results show that climate change will significantly increase the runoff of the PRB, with changing rates of 0.21, 0.20, 0.11, and 0.17 mm/month/year for low- to high-emission scenarios SSP126, SSP245, SSP370, and SSP585, respectively. Future runoff exhibits strong seasonal and spatial variability due to complex changes in precipitation and potential evapotranspiration across the basin. The PRB may experience higher flood risks during the wet season under all SSP scenarios, driven by a ~15% increase in runoff during the wettest month during 2061–2100 relative to that of 2021–2060. Conversely, drought risks may escalate in the East River Sub-basin of the PRB during the dry season under the high-emission scenarios (SSP370 and SSP585), with a ~20% reduction in runoff during the driest month during 2061–2100 relative to that of 2021–2060. The highest-emission scenario (SSP585) may lead to the most drastic hydrological changes, including increased risks of flooding and drought across different parts of the PRB. Our findings suggest intensified water cycling and increased hydrological risks in the PRB under a changing climate, highlighting the necessity of future water resource management to consider potential climate change impacts to mitigate the risks of floods and droughts effectively.