Optimized operation of diversion-type hydropower reservoir to alleviate ecological degradation of the de-watered river reach

Abstract

Diversion-type hydropower stations usually cause seriously de-watered situation of the natural river reach, which has adverse effects on the downstream river ecosystem. To alleviate the negative impacts on ecosystem of natural river reach, this study quantified the ecological requirements and incorporated them into the reservoir operating schemes to provide the ecological flow, which is beneficial to the balance between ecosystem protection and hydropower generation. The method mainly includes (1) propose an optimal ecological flow calculation method based on runoff probability distribution, (2) combine minimum ecological flow with optimal ecological flow to define the ecological protection degree, and then (3) establish the multi-objective optimization model of reservoir with the goal of maximizing ecological protection degree and power generation (DPM) and solve it with NSGA-II. In the meanwhile, the optimization model with the goal of minimizing ecological water shortage and maximizing power generation (SPM) was established and solved which was regarded as a control batch. A case study performed with the Liujiaping (LJP) reservoir in Hunan Province of South China demonstrates that optimized operation can play a protective role in the ecology of the dewatered section. And DPM has better ecological benefits than SPM under the same power generation benefits, especially when the emphasis is placed on ecological benefits.