A novel operation chart for cascade hydropower system to alleviate ecological degradation in hydrological extremes

Incorporating limited ecological curves, a novel operation chart optimization method is proposed for the multipurpose hydropower systems, which is capable of improving power generation and overall ecological condition and alleviating ecological degradation under extreme dry or wet conditions. The method mainly includes: (1) determine the optimal ecological discharge using weighted usable area-discharge curve based on the physical habitat simulation model (PHABSIM); and (2) establish the operation chart optimization model aiming to maximizing power generation and overall ecological condition and solve the model with DPSA; then (3) derive the limited ecological curves and incorporate them in the operation chart. A case study is performed with Jasajiang (JS) and Madushan (MDS) reservoirs on the Yuan River in southwestern China. The results show that the optimized operation charts result in a 1.72% and 5.99% increase in hydropower generation and a 0.27% and 1.13% increase in ecological conservation degree for MDS reservoir, respectively. In addition, the frequency of ecological damage is reduced from 6.11% to 1.11% for JS reservoir and from 26.67% to 3.89% for JS and MDS reservoirs, respectively. A further discussion using a time series of random runoff generated by first-order Markov model has confirmed the adaptability of this operation chart. The feasibility and potential applications of this operation chart has been confirmed.