Ecological Indicators (Oct 2024)
An improved hydraulic method for calculating ecological flow considering the changes of rainfall and temperature within a year
Abstract
Ecological flow (Hereinafter referred to as EF) is vital for sustaining the health of aquatic ecosystems, whereas fluctuations in rainfall and temperature markedly influence the water needs of riverine aquatic organisms. However, traditional hydrological methods for calculating EF provide a single, fixed EF value throughout the year or for specific periods (such as the flood season or non-flood season), neglecting the dynamic effects of these environmental variables on flow requirements. Building on regression analyses of rainfall and temperature, this study proposes an improved hydraulic method (Hereinafter referred to as IHM) that integrates both rainfall and temperature effects. Utilizing the three cascade hydropower plants on the mainstream of the Liuxi River in Guangdong Province, China, as case studies, the proposed method expands upon traditional hydraulic methods by establishing a relationship between river hydraulic parameters and flow, and employing the ecological suitability thresholds of indicator species as constraints to calculate the EF solution sets for the three hydropower plants. By fitting functions to the basin’s rainfall and temperature data, linear interpolation was applied to distribute the EF solution sets across 12 months within a year. The IHM is subsequently compared and validated with the evaluation standards of the traditional method. The results demonstrate that the monthly EFs by the IHM for the three cascaded hydropower plants address the constraints of fixed EFs by traditional hydraulic methods, offering more accurate and context-specific EFs for each month. The monthly EFs by the IHM also typically conform to the Tennant method’s 10 % standard (fair status) and, during certain months, reach the 40 % standard (good status), thereby effectively preserving the stability of the river’s aquatic environment. The IHM provides a robust technical foundation and theoretical framework for the accurate determination of EFs in riverine hydropower plants.
