Operation chart optimization of multi-hydropower system incorporating the long- and short-term fish habitat requirements

There are increasing calls to incorporate ecological requirements into hydropower operation, however it remains a challenge to balance average ecological benefit over a long period of time and ecological damage under wet/dry conditions. This study proposes a new hydropower-ecological operation chart of cascade hydropower stations in which limited ecological curves were introduced and all guiding curves were optimized, aiming to improve the long-term average fish habitat quality and to mitigate the negative impacts caused by drought/flood events on fish habitat without reducing power generation compared to the conventional reservoir operation. The JiaSA(JSA)-MaduShan (MS) cascaded reservoirs in Yuan Basin were chosen as the research area. The physical habitat simulation model (PHABSIM) is used to quantify the hydrological requirements of the target fish species at different life stages. At an ecological need fitness target of 70%, under the guidance of hydropower-ecological operation chart, without reducing the power generation, the average ecological need fitness at the downstream of JSA and MS hydropower stations is increased by 0.09% and 1.06%, the frequency of ecological damage is reduced by 6.12% and 25.00%, and the ecological damage degree during wet/dry periods is reduced by 1.96% and 0.52%, respectively. However, when ecological need fitness target is higher than 80%, the frequency and magnitude of ecological damage are significantly increased. Therefore, the proposed operation chart has the potential to increase the multi-objective benefits of hydropower system and can be easily applied to other cascaded reservoirs in different basins.