Multi-objective Water Operation Practices during the 2024—2025 Dry Season and Future End-of-flood-season Storage Analysis for the Beijiang River Basin

Facing the severe challenges posed by the frequent occurrence of extreme drought events and the intensified competitive utilization of water resources in the context of climate change, conducting research on refined water quantity dispatch during the dry season is of great practical significance for ensuring water supply safety, ecological integrity, and smooth navigation in the basin. This study focuses on the Beijiang section of the Pearl River basin, based on the measured data and dispatch practices during the extreme drought and dry season of 2024-2025. It systematically conducts multi-objective dispatch research centered on meeting daily and monthly average flow standards, reducing saltwater and supplementing freshwater, and ensuring navigation safety. Based on water demand, the required water storage capacity of reservoirs at the end of the flood season is inversely calculated to clarify the water storage target. The research indicates that the ecological base flow (211 m³/s) at the Shijiao section can be ensured by controlling the outflow from the Feilaixia Water Control Project to be no less than 220 m³/s, and dynamically reducing outflow during periods of abundant inflow to conserve water. For meeting monthly average flow standards (250 m³/s), a strategy of "conservative initial stage, later adjustment" should be adopted to avoid early increase in discharge that may lead to reduced dispatch capacity in the later stage. The dispatch for reducing saltwater and supplementing freshwater should be planned in advance, taking into account astronomical tides and holidays, and coordinated with upstream reservoirs for water replenishment. To ensure navigation safety, the water level at Feilaixia should be maintained at no less than 23 m, and effective navigation facilitation should be achieved through the strategy of "upper replenishment, middle dispatch, and lower storage" in conjunction with flood wave regulation at Baishiyao Reservoir. Based on the water balance analysis under extreme dry conditions, it is inversely calculated that the adjustable water storage capacity required at the end of the flood season for the nine key reservoirs in the basin is no less than 1.111 billion m³. Considering actual dispatch needs and historical operation data, the adjustable water storage target at the end of the flood season is set at 1.120 billion m³, which can ensure the achievement of multi-objective dispatch tasks.