Study On The Calculation Methods And Application Of Environmental Flow In The Middle And Lower Reaches Of Yangtze River

Thanks to the Three Gorges Dam?Xiluodu?Xiangjiabai and other water conservancy projects,the hydrological regime and the water using pattern in the middle and lower reaches of Yangtze River have been greatly changed.At the same time,the partial water environment problem become outstanding and water pollution is prevalent.The synthetic effect of these factors brings a great deal of ecological environment problems,and the research on the environmental flow helps to improve these problems.Firstly,according to the fundamental principles of river dynamics and based on the basic connotation of river function?river ecology and river environment,this paper explains the general connotation of ecological flow and environmental flow.Moreover,this paper points out that environmental flow and river health both are vital evaluating indicators in river management,and the content of both vary according to management objectives.Then,this paper gives a systematic summary of the environment problems in the middle and lower reaches of Yangtze River,mainly points out that the quantity of four major Chinese carps which are considered to be the indicator of the river health declined dramatically in successive years,and the declining trend correlate closely to the environmental flow.Furthermore,analyzes the correlation between the spawning amount of four major Chinese carps and several hydrological factors,the results show that the spawning amount is not only related to water temperature,but also significantly correlated with average days with discharge rise and average discharge rise.Combined with the general connotation of environmental flow,the characteristics and contents of environmental flow in middle and lower reaches of Yangtze River are given.Finally,Jianli river reach has been taken as an example to study and compute the environmental flow,a contrasting analysis of environmental flow's computing methods is made,the environmental flow of May?June?July are studied emphatically,the computational results based on RVA indicate that environmental flow of May?June?July is respectively 7648m3/s?12864m3/s?16953m3/s,respectively occupying 70%?83%?72%of average flux of multi-years,combined with all past ecology scheduling which conducted by Three Gorges Reservoir,this paper analyzes the other constituent components of environmental flow,such as total days with discharges rise,the range of discharges rise and so on.From this example,further demonstrated the scientific and rationality of environmental flow.