Impact assessment of cascade freshwater reservoir using the ecological security assessment (ESA) model across a four-year timescale

Abstract

The existence of cascade reservoirs in complex ecosystems not only assists humans to regulate and use water resources efficiently, but the presence of hydropower also contributes to reducing carbon emissions. In recent decades, the ecology of the water sources comprising cascade reservoirs has been subject to a wide range of threats. Assessing these threats is essential for sustainable operation and management strategies of cascade reservoirs. This paper aimed to propose an ecological security assessment framework using an improved Driver-Pressure-State-Impact-Response model to assess a typical riverine cascade reservoir located in the subtropical region of Zhejiang, China. Combining quantitative and qualitative methods to describe the indicators involved in social, economic, ecological, and management. Simultaneously, the degree of deviation from the standard state of ecological security in the study area is assessed with the help of the ecological security index. The analysis shows that the ecological security index of the study area for the four years increased from 81.67 in 2019 to 90.14, where the lowest value has been the socio-economic impact index, indicating that the study area is in a state of ecological security with a score higher than 90.00, but the impact of socio-economic activities on the study area is more pronounced in comparison with other aspects. The model shows that control management with a score of 92.70 in 2022 plays a vital connecting role. Good control management increases socio-economic growth by 16.82%, improves ecological health by 10.23%, and enhances ecosystem services by 5.25% compared to 2019.