In order to explore the impact of hydrological variation and external diversion of water supply on power generation and ecology of hydropower stations, taking the downstream water-reducing reach of Guanting Reservoir as an example, based on the calculation of ecological flow under hydrological variation, the ecological assurance degree of the water-reducing reach is defined. A multi-objective optimal operation model for reservoir power generation and ecological guarantee degree is established, and the non-dominated sorting genetic algorithm（NSGA-II） is used to solve multiple scenarios. The results show that the inflow runoff of Guanting Reservoir changed in 1971 and 1983 respectively, and the power generation and average ecological assurance degree decreased significantly after the hydrological variation. The multi-objective relationship between hydropower generation and ecology is significant, and the reduction of 37.4% in power generation can increase 67.8% in ecological benefits. The power generation and the average ecological guarantee degree are significantly improved after the recharge of the external water source, especially in the dry year, which increased by 56.9% and 40.3% respectively.

This article investigates the hydrological response and ecological flow in the diversion area from the Hanjiang River to the Weihe River. Quantifies the impact of the inter-basin diversion project on the hydro-ecological environment of the downstream river. MIKE BASIN is initially utilized in this research to create the multi-year reservoir operating model of Sanhekou Reservoir. Then Indicators of Hydrologic Alteration (IHA) and Range of Variability Approach (RVA) are used to evaluate the change degree of hydrological indicators. Secondly, set seven different ecological flow process schemes considering ecological demand and inter-annual wetness and dryness variability. Finally, evaluate the optimization scheme by Analytic Hierarchy Process (AHP). According to the hydrological response results, suggestions are put forward from the perspective of engineering and non-engineering. The results show that the simulation results of the MIKE BASIN have a high degree of fitting with the design results, which verifies the rationality of the model. Under the design scheme, the overall hydrological change of the river is 72.91% and the hydrological response of the river is high changed. Scheme 6 can reduce the overall hydrological change to (56.63%) moderate change under the premise of less impact on economic benefits, and scheme 6 is the optimal scheme. The research results not only guarantee the ecological function of the river but also provide guidance and reference significance for the actual operation of the reservoir.