Optimization of stage-controlled gate operations for upstream canal cascades post-contingency: A case study of MR-SNWDP hydraulic system

The Middle Route of the South-to-North Water Diversion Project in China. Long-distance water transfer projects are characterized by complex and variable hydraulic conditions, making them vulnerable to sudden incidents. Effective emergency regulation requires gate operations that are simple and minimize drainage losses. However, most existing studies do not constrain the gate-closure method, often allowing rapid continuous closure, which differs from the staged closure used in actual operations, and may alter hydraulic responses. In this study, an optimal emergency control model was developed by coupling a hydrodynamic model with a multi-objective genetic algorithm. Under a large-flow interruption scenario triggered by a pollution accident, the study examined hydraulic responses to staged gate closure and evaluated optimized schemes using synchronized staged closure as the baseline. Under identical regulation intervals, optimizing drainage increases gate operation frequency but reduces water level fluctuation. Extending the interval reduces operation frequency while maintaining low fluctuations. Compared to the baseline, the optimized scheme achieved moderate reductions in gate operations, reduced drainage volume by 42.1 % and maximum water level fluctuation by 48.8 %. Gate operations generally followed a two-stage pattern—initial rapid adjustment followed by slower regulation—with asynchronous operation of gates and staged drainage adjustments. The proposed model and strategies provide practical guidance for safer and more efficient emergency regulation in long-distance water transfer systems. • Staged gate closures reduce backwater peaks and shorten hydraulic oscillations. • An emergency optimization model is developed, closely aligned with field operations. • Optimized strategies lower operation frequency, drainage volume, and water-level swings.