Analysis And Evaluation Of Water Quality In Yibin-wanzhou Section Of Upper Reaches Of The Yangtze River

Yangtze River water environment quality has been widely concerned by domestic and foreign experts and scholars,and the research on water quality evaluation model of long reach has been the focus of environmental workers.In this paper,researching the domestic and foreign literature,analyzing the similiarties and differences of different methods for water environmental quality assessment,and according to the situation of research status,selecting grey correlation,BP neural net work and comprehensive water quality identification index method to evaluate and analysis the quality of water environment.In this paper,Yibin-Wanzhou section of the upper reaches in the Yangtze River is the research object.The cities,the populatio,the industry and agerculture of this river section are extensive.So the water environment quality evaluation on thei section is of great significance to the production.The data is of 11 river sections water quality data of upper reaches of Yangtze River in 2004~2013.The average value of 16 pollutant index of each section were calculated to pollutant sharing rate.Selecting 8 polllution indexes of the lowest scorer for the evaluation of water environment quality: total phosphorus,potassium permanganate index,dissolved oxygen,lead,cadmium,fluoride,BOD five ammonia.By using grey evaluation method,BPnueral network evaluation method and comprehensive water quality identification index method to evaluate the average data,mean flood and non flood season average data.Comparing the diffenrent methods of evaluation,analysising the defferences and their respective charavteristics,exploring the applicability of deffrent methods.On the basis of this,the changing trend of the indexes in time and sapace was studied.Based on the facal coliform group,find out the associated water quality index.Selecting 6 sections within the one hour ecomic circle,Beibei Zhutuo Linjiangmen,Cuntan,longevity,Qingxichang,the weight of each section is defined by AHP.Based on the weight,analysising the Kuznets curve of pollution indecators and GDP per capita in Chongqing.The results shows that there are some differences between three methods,grey correlation evaluation method for index change is more sensitive than the other two methods,the evaluation results than the other tow methods is poor.but the results is more comsistent to environment protection depatments.The trend of 3 water quality method is still consistent in time and space.Through the comprehensive evaluation of water quality results,the flood season water quality of each section is obviously inferior to that of the non flood season.In the densely populated and developed areas,the water quality of the section is inferior to that in the ralatively small population and relatively weak industrial area.The water environmental quality of Yibin-Wanzhou selection of upper reaches of the Yangtze River shows a good trend in general.The saptial and temporal trends of the selected pollution indicators,most of the indicators change trend is smooth,the trend in space is the same.The results of spatial and temporal analysis are the same as those of water quality evaluation.Based on thefecal coliform,analysing correlation to each indeivator.And it was found that the correlation degree between fecal coliform and water temperature,permanganate index,total phosphorus was higher in some sections.TP index does not exist enviromental Kuznets curve,permanganate index,dissolved oxygen and BOD five showing the environmental Kuznets curve is not obvious in the left half;the ammonia,lead and cadmium shows the rihgt half,but there is still the possibility of a rebound;fitting curve of fluoride and GDP per capita are meet “ N ” type of environmental Kuznets curve.