Research on multi-objective operation based on improved NSGA-Ⅱ for the cascade reservoirs in the Lower Yellow River

Research on the tradeoff relationship between water supply, electricity generation and ecological benefits has great significance for reservoir comprehensive utilization and watershed management. In this paper, an integrated operation model considering multiple goals is constructed based on the contradiction and unity between different objectives of reservoir operation, which is designed to explore the relationship of the water supply, power generation and ecological benefits. And an improved multi-objective evolutionary algorithm with Individual Constraints and Group Constraints is proposed to solve the model. The Xiaolangdi and Xixiayuan cascade reservoirs in the lower Yellow River are taken as a case study, the results show that the method can obtain a set of dispatching schemes which reflect the non-dominated relationships among the multi-objectives in a relatively short time. It is found that the asymmetric tradeoffs between the benefits of ecology, water supply and power generation really exists. Specifically with the increase of power generation, the guarantee rate of ecological and comprehensive water supply decreases. Furthermore, the power generation competes with ecological water shortage stronger than comprehensive water shortage. The study can provide technical support and reference value to multi-objective operation in the lower Yellow River in the future.