Study On The Ecological Flow Of The Upper Yellow River In Changing Environment

Eco-environmental issues have become a bottleneck in the development and operation or water conservancy projects.According to the planning and guiding ideology of China’s "13th Five-Year Plan" for the construction of water conservancy projects,large-scale hydropower stations are one of the construction priorities.The construction of water conservancy projects has changed the hydrological situation,hydrodynamics,and natural conditions of the river’s environment,making the spatial distribution of aquatic habitats of rivers change significantly.It is necessary to scientifically and quantitatively analyze the ecological effects of the project and provide reference suggestions.Ecological flow is an important indicator for the ecological health of rivers and is of great reference value for guiding the study of ecological effects of water conservancy projects.In this paper,we use the fuzzy habitat-based model of fish habitat based on the research on the habitat requirements of target fish species during the breeding period,and use mathematical fuzzy method,numerical simulation method,ecological hydrology,river dynamics,physiological ecology and other methods to carry out research on the ecological flow of the upper Yellow River.The main results obtained in this paper are as follows:(1)The research status of ecological flow is summarized and analyzed.The characteristics and applicability of different viewpoints and calculation methods are analyzed.Based on the hydrological characteristics,meteorological characteristics and aquatic biological characteristics in the upper reaches of the Yellow River,a habitat method based on target fish species is proposed to derive ecological flows.(2)According to the long series of hydrological data,water temperature data,and meteorological data accumulated in the Bando-Yangqu reach in the upper reaches of the Yellow River,as well as water quality data and aquatic biological data combined with field sampling and literature data,the annual changes in the environmental factors and interannual years are utilized.Changes to determine the reference system for the conservation of the target species habitat in the study area.(3)According to the results of aquatic biology survey and related literature data,the target fish species in the study area were determined.According to experimental data of the target fish species,the adaptability mechanism to water environment elements was obtained,and the fuzzy membership function and fuzzy rule base were determined according to the fuzzy mathematics method.(4)In view of the lack of ecological life flow factors in fish life history,based on the growth characteristics and sport characteristics of the target fish species,an individual fish model based on Lagrangian was constructed to simulate individual fish trajectories and explore the changing environment to target fishes influence.(5)Couple the individual fish model and the basic model to obtain the habitat model based on the target species,and construct the habitat recognition function according to the breeding habits parameters of the target species.Use the model simulation to obtain the distribution map of the spawning field during the breeding period of the target species.(6)In order to calculate the ecological significance of cell grids,fuzzy mathematics was used to evaluate the habitat quality of the spawning grounds simulated by the model.Using the dual indicators of effective habitat area and ratio of spawning sites to total area,the appropriate ecological flow range of target fish species was deduced.