Optimizing ecological flow guarantees at Datong Station through adaptive reservoir dispatch: a drought-aware strategy for the Three Gorges Dam

As the world's largest hydropower project, the Three Gorges Dam (TGD) significantly alters downstream hydrological regimes, yet its capacity to ensure ecological flow under drought remains inadequately quantified. This study introduces a novel phased proportion method to evaluate the TGD's adaptive operation based on six decades of daily streamflow data (1956–2023) at Datong Station. Key innovations and findings include: (1) Development of a period-sensitive ecological flow (Eco-flow) framework that captures the TGD's regulatory effect across flood control, storage, ebb, and water supply period. (2) Quantification of a significant 14.7% increase in Eco-flow during critical dry periods (guaranteed water supply period) under TGD operation, highlighting its drought mitigation capability despite an overall 5.4% reduction in multiyear average Eco-flow. (3) Application of a random forest model to demonstrate that TGD operation raises the ecological flow guarantee rate by 2.6% overall and by 4.6% during drought-sensitive periods compared to a naturalized scenario. (4) Proposal and validation of two reservoir discharge enhancement strategies, identifying an optimal release increase of 2,000 m³/s that improves the guarantee rate by 3.9% even with slightly reduced absolute flow. These findings provide a scientifically-grounded, adaptive management strategy to optimize ecological flow guarantees under climatic extremes, supporting sustainable dam operation and river basin resilience.