Non-iterative coordination method for multi-objective flood control operation of a reservoir group based on equivalent projection theory

Study region The middle Yellow River Basin (MYRB) Study focus In real-time flood control operation, high-dimensional nonlinear models challenge timely decision-making. Conventional iterative decomposition–coordination methods suffer from slow convergence in dimensionality reduction. This study proposes an efficient multi-reservoir flood control optimization method (EOM-EP) by coupling a non-iterative coordination framework based on equivalent projection theory (EP) with parallel computing. Numerical experiments demonstrate its accuracy and computational efficiency. Application to typical flood events in the MYRB further highlights upstream-downstream risk transfer mechanisms and flood regulation roles of mainstem and tributary reservoirs. New hydrological insights for the region (1) The non-iterative global coordination mechanism of EOM-EP is applicable to flood control operation of reservoir groups at different scales, and, compared with the Lagrange method, its performance becomes increasingly superior as the dimensionality of decision variables increases. (2) A significant upstream–downstream risk conflict exists between the reservoir group and the Huayuankou section in the MYRB, and balanced objective weights favor reservoir-group spatiotemporal synergy in flood storage and release while mitigating imbalanced risk allocation. (3) Reservoir operation strategies depend on flood spatial composition. The Xiaolangdi reservoir dominates mainstem floods (P1); tributary-dominated floods (P2) require consideration of Hekoucun reservoir risk and compensatory regulation by tributary reservoirs; and concurrent floods (P3) require strengthened coordination to reduce peak superposition. The system flood-control risk across scenarios ranks P2 > P3 > P1.