Multi-Objective Optimal Operation Model of Cascade Reservoirs and Its Application on Water and Sediment Regulation

Abstract

Recently suspended river, where formed both in tributary and in main stream of Ningxia-Inner Mongolia reaches in the Upper Yellow River, severely threatens people’s lives and property safety downstream. In this paper, taking Ningxia-Inner Mongolia reaches for the example, water and sediment are regulated by cascade reservoirs upstream, which can form artificial controlled flood, to improve the relationship of water-sediment and slow down the speed of sedimentation rate. Then, multi-objective optimal operation model of cascade reservoirs is established with four objectives: ice and flood control, power generation, water supply, water and sediment regulation. Based on optimization technique of feasible search space, the non-dominated sorting genetic algorithm (NSGA-II) is improved and a new multi-objective algorithm, Feasible Search Space Optimization-Non-dominated Sorting Genetic Algorithm (FSSO-NSGA-II) is innovatively proposed in this paper. The best time of water and sediment regulation is discussed and the regulation index system and scenarios are constructed in three level years of 2010, 2020 and 2030. After that regulation efforts and contribution to sediment transportation are quantified under three scenarios. Compared with history data in 2010, the accuracy and superiority of multi-objective model and FSSO-NSGA-II are verified. Even more, four-dimensional vector coordinate systems are proposed innovatively to represent each objective and sensitivity of three scenarios are analyzed to clarify the impact on regulation objectives by regulation indexes. At last, relationships between four objectives are revealed. The research findings provide optimal solutions of multi-objectives optimal operation by FSSO-NSGA-II, which have an important theoretical significance to enrich the methods of water and sediment optimal operation by cascade reservoirs, guiding significance to water and sediment regulation implementation and construct water and sediment control system in the whole Yellow River basin. We establish an multi-objective optimal operation model with four regulation objectives. We proposed a improved multi-objective algorithm (FSSO-NSGA-II) based on feasible search space optimization. Regulation index system and three scenarios are constructed. Four-dimensional vector coordinate systems are proposed to represent each objective and sensitivity of scenarios are analyzed. Relationships between four objectives are revealed.