Water Quality Evaluation And Cause Analysis Of Taojiang River Based On BP Neural Network And WPI

The water environment in southern China,especially the Yangtze River Basin,has always been the focus of social attention.Scientific water quality assessment helps to understand the situation of water pollution in time,and can point out the direction for solving the problem of water pollution and protecting the water environment.This is of great significance to the development of social economy and the protection of the ecological environment.The Ganjiang River is an important tributary of the Yangtze River,and the Taojiang River Basin in the upper reaches of the Ganjiang River is a typical rare earth mining area in China.In this paper,the Taojiang River Basin is taken as the research area.Based on remote sensing image data,measured water quality indicators and precipitation data in the basin,the author used descriptive statistical analysis to analyze the results of water quality indicator detection of 10 monitoring sections in the basin from 2014 to 2017.The analysis results show that the content of the detected dissolved oxygen,permanganate index,BOD₅,ammonia nitrogen,total phosphorus,fluoride and other 6 indicators have obvious temporal and spatial distribution differences in the watershed,and ammonia nitrogen is the most obvious.Combined with the characteristics of the BP neural network model,a three-layer BP neural network model with only one hidden layer is used to classify the water quality of the Taojiang River Basin.At the same time,the water pollution index method is used to evaluate the water quality of the basin,and then the similarities and differences between the two evaluation methods are analyzed and compared.The water quality evaluation results based on the BP neural network model show that the water quality categories of each monitoring section of the Taojiang River are mainly category I and II.The water pollution index evaluation results show that the water quality categories of most monitoring sections are Type II and Type III,accounting for 55%and 29%respectively.The two evaluation methods have in common that both evaluation methods show that the Taojiang River water quality generally meets the watershed functions and protection objectives of the basin,and the water quality of the Longtoutan section is poor.According to the results of water quality evaluation and referring to the field investigation data,this paper analyzes the causes of water pollution in Taojiang River Basin,and concludes that the water quality in Taojiang River Basin is jointly affected by natural precipitation and man-made pollutant discharge.Sources of pollutants mainly include unreasonable application of pesticides and fertilizers in various agricultural activities,domestic sewage and garbage,as well as wastewater and tailings discharged from various industrial activities focusing on rare earth mining and selection.Therefore,the water environment management work can start from improving the water environment prevention and control policies and regulations,promoting the prevention and control of agricultural non-point source pollution and industrial pollution,and strengthening the treatment of urban and rural life pollution.