Cascaded Hydropower Operation Chart Optimization Balancing Overall Ecological Benefits and Ecological Conservation in Hydrological Extremes Under Climate Change

In this study, we proposed a new method to derive multi-purpose reservoir operation chart with the objectives of maximizing power generation and ecological conservation and minimizing ecological damage under future climate change. This double-parameter ecological operation chart (DEOC) was obtained by incorporating limited ecological curves into original conventional operation chart (COC) and then establishing and solving the operation optimization model considering both ecological profits and hydropower generation. Unlike COC where reservoirs are operated based on the current water level, reservoir operation under DEOC is based on both current reservoir water level and inflow. A case study was conducted in Jasajiang (JS) and Madushan (MDS) cascade reservoirs on the Yuan River in southwestern China. The monthly runoff data for the period 2021–2050 under RCP4.5 and RCP8.5 was simulated using the Soil and Water Assessment Tool (SWAT) driven by the General Circulation Models (GCMs), and the optimal ecological flow range calculated by PHABSIM for a given river section was used to determine the limited ecological curve. The operation optimization model considering both ecological profits and hydropower generation was established and solved to obtain DEOC. Compared with COC, DEOC results in a significant increase in power generation (>9%) and a reduction in ecological damage frequency without affecting the overall ecological conservation rate, especially at an ecological target of 70% and 80%, which can improve the adaptation of reservoir operation to climate change.