An improved multi-objective optimization model for supporting reservoir operation of China's South-to-North Water Diversion Project

•An improved multi-objective optimization model for reservoir operation was proposed.•Ecological water demand was calculated combining those of steady- and pulse-states.•The model was applied to the South-to-North Water Diversion Project in China.•Both economic and ecological benefits were considered for reservoir operation.

An improved multi-objective optimization model based on goal programming (GP) for supporting reservoir operation was developed under inflow senarios of multiple runoff guarantee rates (i.e., 25%, 75%, perennial mean, and 95%) and ecological goals with the combination of steady- and pulse-state ecological water demands. Under these four scenarios, discharge flows of Danjingkou Reservoir would be 358.40, 369.67, 268.91 and 98.14 × 108 m3/a, and those at Taocha Canal headwork would be 104.61, 86.62, 95.08 and 64.00 × 108 m3/a, respectively. The generated results for stream flows could successfully meet the predetermined operational goals for the project. Comparatively, under the scenario of 95% runoff guarantee rate, the obtained strategies could not satisfy the ecological water demands. The modeling results indicated that the capacity of water diversion and storage for Danjiangkou Reservoir would be enhanced due to the operation of the South-to-North Water Diversion Project. The results showed the risks associated with possible flooding would be comparatively low under those four runoff guarantee rates. This represents the current priority for flood control in Danjiangkou Reservoir needs to be changed into multiple ones including ecological water supply, water transfer, as well as downstream water security maintenance.

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