Tradeoff analysis between economic and ecological benefits of the inter basin water transfer project under changing environment and its operation rules

Abstract

Inter basin water transfer projects inevitably affect the ecosystem of the river in the water source area, especially under the changing environment. The tradeoff analysis between economic and ecological benefits has become a focus problem in actual multi-objective reservoirs operation. Therefore, this paper aims to research the tradeoff relationship by the multi-objective reservoirs optimal operation model considering economic and ecological objectives. Specifically, mutated runoff series are corrected by seasonal and trend decomposition using Loess (STL), and three ecological water demand processes are gained from the corrected runoff. Then, an improved evolutionary algorithm is proposed to solve this model, named Non-dominated Shorting Particle Swarm Optimization with Feasible Search Space (FSS–NSPSO). Furthermore, contour maps and functional formulae are fitted to describe the tradeoff analysis among three objectives. Finally, operation rules are generated considering ecological water demand. The paper applies the model to the Hanjiang to Wei River Water Diversion Project. The results indicate that: (1) the ecological water quantity in the river has decreased further under the influence of changing environment. (2) The FSS-NSPSO has advantages in terms of convergence, uniformity, and diversity compared to the Fast Elitist Non-dominated Sorting Genetic Algorithm and Non-dominated Sorting Particle Swarm Optimization. Real number coding, less evolutionary operator parameters and a feasible search space in the FSS-NSPSO are benefit for solving complex multi-objective reservoir models. (3) The contradiction between ecological and economic benefits is obvious. Ecological water demand process affects reservoir operation benefit. (4) The reservoir operation rules can be generated based on the modified ecological water demand process to balance the interests of multiple parties. This study is expected to be of merit to quantitative tradeoff analysis between ecological and economic benefits in inter basin water transfer projects, and as a reference method for multi-objective reservoir operation models.