Author(s): Zhenhua Cui; Shuai Niu; Ni Xiao; Liang Wang; Wenlin Zhai

Linked Author(s):

Keywords: Chishui River; Environmental Flow; Hydraulic Analysis; Weighted Usable Area (WUA)

Abstract: [Objective] The National Nature Reserve for the Rare and Endemic fishes of the Upper Reaches of the Yangtze River is located in Chishui River Basin, and some small hydropower stations have been decommissioned in recent years. Conducting research on environmental flow for these target rare and endemic fishes and applied in reservoir regulation in cases where small hydropower stations have been decommissioned but the reservoirs remain is of significant importance. [Methods] This paper employs the Instream Flow Incremental Methodology (IFIM) to conduct two-dimensional hydrodynamic simulations and fish habitat simulations of the river reach below the reservoir dam in Chishui River Basin, thereby establishing a quantitative response model between the environmental flow and the suitable physical habitat area for target fishes. Based on fish samples collected at the downstream of the case study reservoir, Sinogastromyzon sichangensis Chang and Acrossocheilus monticolus (Gunther) are selected as target species for habitat simulation in the watershed. Using on-site fish sample data, this study calculates and proposes suitability curves of flow velocity and water depth for the target fish species. By analyzing the Weighted Usable Area (WUA), changes in suitable physical habitats under various environmental flow during sensitive periods are examined, thus determining the optimal range of environmental flow for the target fish species. Integrating reservoir operation objectives, an ecological reservoir scheduling scheme is proposed. [Results] Through calculations with 28 flow simulation schemes, it is revealed that the suitable habitat area reaches its maximum at a flow rate of 9 m3/s, occupying 27.9% of the total river channel area. The optimal flow range lies between 2 to 20 m3/s, during which the area of river habitat suitable for fish survival accounts for over 20% of the total river area. Through reservoir regulation, the guarantee rate of environmental flow during sensitive periods can be improved. [Conclusion] The findings of this project provide technical support for calculating the environmental flow for reservoirs during sensitive periods of rare fishes and for optimal reservoir regulation.

DOI: https://doi.org/10.3850/iahr-hic2483430201-111

Year: 2024