Assessing Climate Change Impacts on Runoff Variability and Extremes in China Using High‐Resolution Simulations

ABSTRACT Understanding how climate change influences hydrological variability and extremes is crucial for assessing future hydroclimatic risks and climate adaptation needs. Despite the importance of China as a region highly vulnerable to climate change, few studies have assessed future runoff variability and extremes at a high spatial resolution across the entire country. This study provides a comprehensive analysis of future runoff changes across China at 0.25‐degree resolution under medium (SSP245) and high (SSP585) emission scenarios. This analysis uses the Joint UK Land Environment Simulator (JULES), specifically tailored for simulating hydrological processes in China. The model is driven by downscaled and bias‐corrected Global Climate Models, using the bias‐correction and spatial disaggregation method. Results highlight significant regional disparities in annual runoff, with the Southeast basin experiencing an increase of 41.45 mm/decade under SSP585, compared to a national average increase of 7.30 mm/decade. Seasonal patterns reveal contrasting trends: wetter summers and drier winters are expected in the south, whilst the northwest is expected to experience the opposite pattern. More than 56% of regions, especially in the Pearl River and Southeast basins, are projected to face an increase in extreme high runoff. Extreme low runoff is projected to intensify across over 40% of China, with the central Yangtze River basin being particularly affected. Both extreme high and low runoff are expected to become more severe in the far future, with more severe impacts under SSP585. These findings reveal the spatial differences in runoff changes under climate change, highlighting the varying impacts across different regions and the need for tailored adaptation strategies.