南水北调中线总干渠受跨渠桥梁运输及汛期外洪等影响，存在突发水污染风险。为此，构建了统一的水动力水质模型，通过St.Venant方程组模拟普通渠段水流运动，并结合节制闸、分水口、倒虹吸、退水闸等特殊结构处的连续方程和能量方程，实现了全线统一建模，避免了分段建模的复杂性。基于断面控制体，建立了一维水质模型，确保污染物质量守恒，提高了模拟精度。模型以FORTRAN90语言开发，实现突发水污染扩散及处置在线预演。模拟结果表明，关闭分水口、增加退水闸排水量可显著提高污染物排放效率，节制闸关闭速度对污染控制效果至关重要。研究为中线突发水污染事件的防控提供了技术支持。

The middle route of the South-to-North Water Diversion Project is affected by cross-canal bridge transportation and external floods during the flood season, and there is a risk of sudden water pollution. To this end, a unified hydrodynamic water quality model was constructed. The St. Venant equations were used to simulate the water flow movement in ordinary canal sections, and the continuity equations and energy equations at special structures such as control gates, diversions, inverted siphons, and water discharge gates were combined to achieve unified modeling of the entire line, avoiding the complexity of segmented modeling. Based on the cross-section control body, a one-dimensional water quality model was established to ensure the conservation of pollutant mass and improve the simulation accuracy. The model was developed in FORTRAN90 language and integrated into the "Digital Twin South-to-North Water Diversion Middle Route" system to achieve online preview of sudden water pollution diffusion and disposal. The simulation results show that closing the diversion and increasing the discharge of the water discharge gate can significantly improve the pollutant emission efficiency, and the closing speed of the control gate is crucial to the pollution control effect. The research provides technical support for the prevention and control of sudden water pollution incidents in the middle route.