Aquatic Ecosystem Health Indicators Of The Mainstream Of The Yellow River

River health reflects the scientific development view and sustainable development strategy in Chinese watershed management. And it has important significance in promoting economical efficiency, environmental sustainability, social justice, and realizing harmonious co-existence between human and river. The river health mark, evaluation index, and its quantitative standards have become an urgent problem in river health idea application. River ecosystem health is very important content in river health. To provide the scientific basis for healthy repair of the Yellow River, this paper using methods of ecology, eco-hydrology, eco-hydraulics, environmental hydraulics, environmental science, management science and economics and taking the aquatic ecosystem maintenance in the mainstream of the Yellow River as starting point, put forward aquatic ecosystem health index system of the mainstream of the Yellow River, then studied indicators identification and its quantitative standards. The main contents and findings of this dissertation are as follows:(1)The health sign of aquatic ecosystem of the mainstream of the Yellow Rivers was defined that the aquatic ecosystem of the mainstream the Yellow Rivers is all right, and there exists continuous stream flow in its channel. The protection scale of the key population and the ecologic flow as the indicators to characterize the aquatic ecosystem health were put forward.(2) The aquatic ecosystem of the mainstream of the Yellow Rivers was divided into several parts using the systematic cluster analysis taking the channel ecological function consistency as principle and taking the biological factors (zooplankton, Phytoplankton, benthos, fishes) and the non-biological factors (the physical and chemical status of water, climate, landform) as classification index.(3) The thought was given to recognize the key species and key population for aquatic ecosystems in different reach of the mainstream of the Yellow River. First, according to the food chain structure of aquatic ecosystem in different reach of the mainstream of the Yellow River, the key index of various species in aquatic ecosystems was calculated and compared, and the key species were identified. Secondly, based on the population structure of key species, population protection orders of the key species were calculated. The population receiving priority to protection was the key population of river aquatic ecosystems. (4) The protecting scale of the key population was calculated using logistic growth model, taking the initial biomass as the protection scale of key population and selecting the bait-creatures in the mainstream of the Yellow River as main influential factors to the growth of the key population.(5) The basic elements to calculate river eco-flow should include water flow and ecology. In water flow conditions study, the application of the river hydraulics model HEC-RAS is more extensive and in ecological analysis, the physical habitat simulation model (PHABSIM) is oriented. The advantages of these two models were integrated and the method to calculate eco-flow based on the HEC-RAS model and the PHABSIM model was put forward. Firstly, the method used HEC-RAS model to calculate water level of every cross section; then, it used water depth calculation method offered by hydraulics model in PHABSIM to deduce the flow velocity of every part in each cross section; at last, it used habitat model in PHABSIM combining fitness curve of key population to estimate eco-flow of each cross section. In theory, the results are more reasonable than hydrology and hydraulics methods.