Abstract: Large water diversion project has changed the natural flow regime in rivers, and has brought about out standing conflict between domestic water demand and eco-environmental water demand. With water demand and environmental flow components as sub-goals of optimization, the optimal combination of water diversion ratio and reservoir water storage is searched by using genetic algorithm with 39 decision variables, including 3 water diversion ratios and 36 reservoir storage levels. The trans-basin joint operation of Dahuofang water diversion project and Dahuofang reservoir is taken as a typical case study. Results conclude that the average annual water diversion amount is 172.42 million m³, which is 6.38 million m³ smaller than the original plan, obviously alleviating the conflict between the domestic and ecological water demand in the Hunjiang river basin and the ecological water demand in Dahuofang reservoir. Moreover, according to the weights of holistic domestic water shortage and environmental flow component, many combinations of sub-goals with different weights are designed to reflect the correlation between water shortage and environmental flow component. Decision-makers of reservoir operation could obtain the water diversion ratio and reservoir water storage which meets the water demand by adjusting the weights. The research results would offer reference for the decision-making of large hydro-projects.

Key words: trans-basin water diversion, optimal reservoir operation, trans-basin water resources management, environmental flow components, hydrological variability indicator, ecological integrity