Abstract: This study examines cascade reservoirs operation to consider carp spawning and utilize water resources effectively via a case study of the Xiluodu-Xiangjiaba cascade hydropower stations in the lower Jinsha mainstream. First, we collect information from previous studies and measurements and estimate the appropriate ecological flow (AEF) required for fish spawning. Then a double-layer multi-objective model for cascade reservoirs operation is constructed using the long-short term coupling nested model, with an upper layer model solved by non-dominated sorting genetic algorithm (NSGA-II) and a lower layer model by the genetic algorithm (GA). This model is applied to the cascade reservoirs and their daily operation schemes are determined with a suitable consideration in improving the spawning habitats. The results show that to promote fish spawning, the total capacity of electric power production decreases by 191 million kW·h or a relative decrease of 1.76%, the fitness of ecological flow increases by 0.123, and the effective flood pulses cover up to 12 days. This study could help formulate ecological operation schemes for cascade reservoirs that need to promote the spawning of four major Chinese carps in the downstream.

Key words: Xiluodu Reservoir, Xiangjiaba Reservoir, four major Chinese carps, ecological operation, coupling nested model