Impacts of basin-wide reservoir operations on future Yangtze river flood and flow regimes under bias-corrected CMIP6 projections

Study region: The Yangtze River Basin, China. Study focus: Existing studies primarily focus on the historical impacts of a few large dams at localized sites, leaving the collective impacts of basin-wide reservoir operations under future climate scenarios poorly understood. We address this gap by implementing a hydroclimate framework that incorporates 327 dams into the mizuRoute river model. We applied a water-balance-based bias-correction method to five GCMs under three SSP scenarios. This approach reduces runoff biases and allows reliable projection of future changes in river discharge and hydrological extremes for 2041–2070 relative to 1980–2014. Furthermore, the relative contributions of climate change and reservoir regulation to these shifts are quantitatively isolated. New hydrological insights for the region: Results indicate that reservoir regulation dominates future flood changes with a reduction of −20.5% to −21.4%, largely offsetting the 13%–16.1% increase driven by climate change. However, this buffer is being outpaced by climate intensification, resulting in future regulated flood peaks that still exceed historical levels by 8.59%. Simultaneously, the basin will transition to a perennial high-flow state in the dry season that fundamentally homogenizes natural eco-hydrological conditions. Downstream tributaries emerge as the most volatile zones, facing the highest climate-driven intensification risk. These findings underscore the urgent need for a cohesive, basin-wide coordinated strategy to manage escalating residual risks under intensifying climate extremes.