Abstract: The downstream of Jinsha River is a national nature reserve for rare fishes. The natural reproduction and growth of fishes need appropriate ecological flow (AEF). In the purpose of exploring the effect of Xiluodu-Xiangjiaba cascade reservoirs on the AEF in the downstream of Jinsha River, the Range of Variability Approach (RVA) was employed to quantify the downstream AEF. A multi-objective model for the scheduling optimization of cascade reservoir group was established with objectives of maximizing power generation and minimizing the change degree of downstream AEF. The model was solved by Non-dominated Sorting Genetic Algorithm II (NSGA-II). The inflow of typical wet, normal and dry years was selected for the optimization. Results demonstrate that under the constraints, power generation in wet year increases by 0.7% to the maximum and the corresponding change degree of AEF soars by 20.82%; with ecological flow as objective, the change degree of AEF can be reduced by 28.06% by losing 0.48% of the power generation. The power generation in normal year increases by 1.28% compared with conventional operation, meanwhile the change degree of AEF augments by 13.87%; such change degree could decline by 22.53% by cutting power generation by 0.62%. The power generation in dry years grows by 1.89% compared with conventional operation while the change degree of AEF raises 4.96%; under the ecological objective, the change degree of AEF could lessen by 13.7% by curtailing 0.35% power generation. The research findings offer reference for the planning of ecological scheduling of Xiluodu-Xiangjiaba cascade reservoirs in the lower reaches of Jinsha River.

Key words: ecological operation, multi-objective optimization, NSGA-Ⅱ, storage period, lower reaches of Jinsha River