A novel framework for reservoir outflow simulation combining satellite observation and hydrologic modeling

Study region The Minjiang River Basin is located in Sichuan Province, China, within the upper reaches of the Yangtze River, characterized by complex mountainous terrain and reservoir systems. Study focus Many reservoirs in ungauged regions lack sufficient data, making satellite remote sensing a viable solution for long-term monitoring. Previous satellite-based approaches are mainly limited to monthly or semi-monthly scales, especially in complex terrain, limiting the timely estimation of reservoir outflow. This study presents a method coupling hydrologic modeling with satellite imagery for subweekly estimation of reservoir inflow, storage, and outflow, achieving high accuracy across the target reservoirs. New hydrological insights for the region The reconstructed area and storage series reveal consistent seasonal regulation across the target reservoirs in the mountainous Minjiang River Basin. However, the reservoirs storage showed an anomalous increase in anticipation of the drought in 2022, which likely reflects anticipatory water storage in response to expected water shortages. Besides, the subweekly series captured short-term reservoir responses following individual rainfall events that were not clear from monthly or coarser records, revealing short-term changes in reservoir inflow, storage, and outflow. The dynamics inform water allocation and demand planning in mountainous areas around the reservoirs. The estimated outflow series provide inflow information for downstream cascade reservoirs, supporting reservoir operation and water-resource management across the Yangtze River Basin, including the Three Gorges Reservoir.