跨流域调水系统的水量调度问题涉及多水源、多用户、多目标等，关系结构复杂，决策变量众多，传统单一模拟方法或优化方法难以兼顾求解效率与优化性能的需求。针对此，提出一种多水源调度模拟-优化双层耦合求解算法，上层算法基于近似最优原则模拟本地水源调配，下层算法引入大系统分解协调优化外调水调配，能够在保障优化性能的同时有效降低计算复杂度。以南水北调东线工程一期及北延段为研究区域，以受水区用户加权缺水率平方和最小与源头调水总量最小为优化目标，构建水量调度多目标优化模型，并采用模拟-优化双层耦合算法进行求解。结果表明：相较于直接优化，模拟-优化双层耦合算法优化效果近似，但平均耗时更短；算法将本地水与外调水的联合调配按优先次序进行模型分解，提高了多水源调度结果的可解释性；算法能够为求解大规模跨流域调水多水源多目标水量调度问题提供参考。

Over a hundred water transfer projects have been implemented to address the disparity between the spatial distribution of water resources and economic and social development patterns in China, notably the Eastern and Middle Route of South-to-North Water Transfers Project. These projects are vital for supporting sustainable economic and social development. The integration of cross-basin and cross-regional water transfer projects with local water source projects forms a complex multi-water source system, which involves multiple regions, projects, users, as well as departments, which results in large-scale, multi-objective nonlinear programming challenges. Traditional simulation or optimization methods struggle to balance solution efficiency with optimization performance. Hence, studying simulation-optimization coupling algorithms is a practical approach to enhance calculation efficiency and ensure effective water resource utilization. This study examines the allocation sequence of local and external water resources, and proposes a dual-layer coupling solution algorithm for multi-water source scheduling. The algorithm first uses simulation methods to address local water source allocation (upper-layer algorithm), employing a uniform water supply mode to calculate the ideal optimal water supply quantity and adjust constraint violations period by period. Subsequently, a large-scale system decomposition and coordination method is used to manage external water allocation (lower-layer algorithm) based on upper-layer scheduling results. By introducing coordination variables to decouple system correlation constraints, the original complex system is transformed into multiple simpler subsystems, with optimal solutions obtained through feedback and iteration between subsystems and the coordination layer. A multi-objective optimization model for water quantity scheduling was developed in the Eastern Route of South-to-North Water Transfers Project area. The optimization goals were to minimize the total weighted water shortage rates of users in the receiving area and the overall amount of water transferred from the source. The simulation-optimization dual-layer coupling algorithm was employed to solve the problem, and its effectiveness was verified. Results for the typical dry year of 1992 showed that: (1) With a Yangtze River flow of 4.364 billion m3, the water demand of the receiving area can be met by prioritizing surplus local runoff from Hongze Lake and Dongping Lake; (2) Diverting 2.5 billion m3 of water from the Yangtze River can reduce the comprehensive water shortage rate in the receiving area to 16.52%. This water quantity scheduling plan is a coordinated approach addressing both water shortage and diversion; (3) The simulation-optimization dual-layer coupling algorithm, combined with constraint relaxation, local water source simulation, and large-scale system decomposition and coordination, effectively reduces the computational complexity of cross-basin water transfer system scheduling problems while ensuring optimization performance. The layered calculation demonstrates that the joint allocation relationship between local and external water transfers, thus improving the interpretability of multi-source scheduling results. The algorithm provides a reference for solving multi-objective water quantity scheduling problems in large-scale cross-basin water transfers.