Author(s): Zhengjie Yin; Cunhua Yang; Luli Chen
Linked Author(s):
Keywords: Environmental flow; Hydrologic alteration; Dam operation; Flow regime; River ecosystem
Abstract: To mitigate possible negative impacts of cascade dams in the Lower Jinsha River and maintain the natural flow regime of national natural reserve areas of rare and special fishes of the upper Yangtze River, environmental flow demands need to be considered in the cascade dams operation. Due to lack of regular ecological observation data, multiple hydrology-based environmental flow methodologies including Tennant, minimum monthly flow, 7Q10 and Q90 are applied to provide specific environmental flow prescripts to guide the reservoir release. A joint operation optimization model is developed for the cascade dams in the Lower Jinsha River for maximal hydropower generation under various environmental flow constraints. The economic and ecological performances of cascade dams operation are evaluated by total hydropower outputs and hydrological alteration degree of downstream river individually. The operation results are analyzed and discussed, and some questions on the tradeoff relationship between ecology and hydropower generation, inherent relationship between ecological constrains and hydrological alteration, and rationality criteria of environmental flow are further addressed. The conclusions indicate: (1) optimal operation for ecological considerations under environmental flow constrains only reduce hydropower outputs slightly, no more than 2. 4% ; (2) environmental flow constrains help lower hydrological alteration induced by hydropower dams, among the four e-flow methodologies Tennant is best in term of ecology; (3) there is a limitation for hydrology-based environmental flow methodologies, and it is necessary to stress ecological foundation and ecological relevance for e-flow methodology. The paper will provide technical references for future ecological re-operation of the cascade dams.
Year: 2013