Refined Environmental Flow Management: Integrating Fish Multiple Life‐Stage Requirements Into Fine‐Scale Operation of Cascade Reservoirs

ABSTRACT Following river damming, releasing the environmental flow (e‐flow) becomes an essential mechanism for sustaining the normal growth of aquatic biota. However, current reservoir e‐flow management typically adopts static threshold standards rather than dynamic or process‐based regulation. The ecological basis for e‐flow emphasizes the necessity of life history completion for target species, where reproduction and population abundance serve as key indicators for restoring ecological functions. This study selects fish as an indicator of riverine ecology and proposes a refined e‐flow management framework considering multiple life stages of fish. By linking species' functional traits to local habitats based on life history strategies for spawning, foraging and refuging, we establish fish environmental requirements and quantify stage‐specific habitat preference curves. The long‐term dynamics of habitat suitability under reservoir operation are simulated by coupling hydrodynamic and habitat models, and stage‐specific e‐flow ranges are quantified using the panel smooth transition regression model. Furthermore, during the spawning‐sensitive period, a two‐layer refined ecological operation model is developed to address daily/sub‐daily survival requirements of adult spawners and early‐stage fish. Applied to the three Gorges–Gezhouba cascade reservoirs on the Yangtze River, targeting the four major Chinese carps that are representative pelagic egg spawners, this framework quantifies fish‐centric e‐flow ranges across spawning, foraging, nutrient storage and overwintering periods and proposes joint ecological operation schemes for ‘control and re‐regulation’ cascade reservoirs across daily and hourly scales in different hydrological years. The study provides a scientific basis for restoring ecohydrological processes and safeguarding long‐term ecological integrity in regulated rivers.