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

Study region: The Middle Route of the South-to-North Water Diversion Project in China.Study focus: Long-distance water transfer projects are characterized by complex and variable hydraulic conditions, making them vulnerable to avoid sudden incidents. Effective emergency regulation requires gate operations that are simple and minimize drainage losses. However, most existing studies assume continuous gate closure, deviating from staged closure used in real operations, leading to different 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 hydraulic response to staged gate closure was examined. Using synchronized staged closure as the baseline, several optimized schemes were evaluated for effectiveness.New hydrological insights for the region: Under identical regulation intervals, optimizing the drainage process increases gate operation frequency but reduces water level fluctuation amplitudes. Extending the interval reduces operation frequency while maintaining low fluctuations. The optimized schemes achieved moderate reductions in gate operations but substantially decreased drainage volumes and water level oscillations. Gate operations generally followed a two-stage pattern—initial rapid adjustment followed by slower regulation—with asynchronous operation of gates at the ends of canal pools and staged drainage adjustments. The proposed model and strategies demonstrate strong applicability for emergency regulation in long-distance water transfer systems, offering practical insights for improving operational safety and efficiency.