Study on ecological flow in Western Route of South-North Water Transfer Project under multi-objective requirements

Abstract

[Objective] Ecological flow serves as a fundamental constraint in determining the transferable water volume for the Western Route of the South-North Water Transfer Project, requiring comprehensive quantification that balances multiple requirements such as the maintenance of downstream ecological functions, water resource utilization, and scheduling management. However, the optimal selection of ecological flow method under different requirements in the Western Route Project requires further research. [Methods]64 years of observed hydrological data from two key control stations—Yajiang station and Dajin station—in the water transfer watershed were utilized, and ten typical hydrological method were selected to calculate ecological flow, including the Tennant method, Texas method, and intra-annual distribution method. Additionally, a fuzzy optimization method was applied to evaluate the suitability of these hydrological method for ecological flow under different requirement weights. [Results] The result showed that ecological flow result calculated by different hydrological method exhibited different suitability under four critical requirements: hydrological regime consistency, downstream ecological requirement assurance, upstream water transfer capacity, and long-term inflow satisfaction. When these four requirements were comprehensively evaluated using the fuzzy optimization method, the Texas method demonstrated the highest suitability. Intra-annual ecological flow ranges were recommended at 64.6~608 m³/s for the Yajiang station and 48.4~491 m³/s for the Dajin station. [Conclusion] The suitability assessment of hydrological method under multi-objective requirements has enhanced the technical framework for research on ecological flow in the Western Route Project. It provides important scientific references for ensuring ecological safety, optimizing water resource allocation, and informing subsequent engineering design and scheduling management.

Keywords

Western Route of South-North Water Transfer / ecological flow / hydrological method / fuzzy optimization method / suitability assessment / multi-objective requirements / water diversion project / influencing factors