Research And Implementation Of Multi-scale Agricultural Non-point Source Pollution Risk Assessment Visualization System In Chongqing Based On WebGIS

China’s agriculture has surpassed industry to become the largest non-point source pollution industry in China.Agricultural non-point source pollution(ANSP)seriously threatens the safety of drinking water of the whole country.Located in the hinterland of the Three Gorges Reservoir Area,Chongqing is an important ecological barrier in the upper reaches of the Yangtze River.With the social and economic development,the situation of ANSP in the Three Gorges Reservoir Area in Chongqing is becoming more and more serious.A series of complex characteristics of ANSP increase the difficulty of prevention and control,at the same time,there is a long-term problem of insufficient effectiveness of prevention and control technology in the prevention and control of ANSP.Propose effective and feasible technical solutions to control and prevent ANSP has become the focus and difficulty of current research.In recent years,GIS technology has become one of the main technologies to study ANSP.With the help of GIS technology,especially Web GIS technology,the collected data related to ANSP can be stored,processed,displayed and analyzed concisely and intuitively,and the environmental monitoring information system can be established,which can effectively provide assistance for environmental decision-making.This thesis is supported by the special key project of technological innovation and application development of Chongqing bureau of science and technology "construction of multi-stage grid management system of ANSP based on 3S technology",and takes Chongqing,Fuling district,Nantuo town and Muhe village as the research demonstration sites.A series of studies were carried out around the theme of "Chongqing multi-scale ANSP risk assessment visualization system based on Web GIS".The specific work of this thesis is as follows:(1)The data related to ANSP in the research demonstration sites were collected,integrated and processed.The causes of ANSP are complex,involving multiple subjects and scattered relevant data.All kinds of data are mostly in the form of words or figures,which are recorded separately in public platforms such as the government statistical yearbook and the annual reports of relevant government departments.There is a lack of data integration and persistent processing,and the form is relatively single and the expression is not intuitive enough.This leads to the absence of basic database construction related to ANSP in Chongqing,and the degree of data visualization is poor.This thesis collects geospatial data,attribute data,statistical data and other ANSP related data at certain time nodes in four research demonstration sites.Then,the collected data are digitized and visualized by using GIS technology and referring to the previous relevant research literature,and they are persistent,which also provides some data support for the follow-up research on ANSP in Chongqing.(2)A multi-scale ANSP database based on Hadoop is designed and built.Chongqing multi-scale ANSP risk assessment visualization system platform involves a wide range of relevant data types and a large amount of data,as well as a large number of geospatial data.With the continuous accumulation of research data related to ANSP at different scales and the addition of more research regional scales,the amount of data will become increasingly large and complex.If the traditional database is used to store the data related to multi-scale ANSP,there will be deficiencies in the flexibility and scalability of the database.Therefore,this thesis uses Hadoop open source cloud computing platform to build Hadoop cluster.Combined with the data characteristics and actual business requirements,through its distributed file system HDFS and distributed database HBase,this thesis designs and builds a multi-scale ANSP database based on Hadoop,which ensures the good flexibility and scalability of multi-scale ANSP database,It effectively solves the problem that the storage of increasing GIS geographic information data is limited under the traditional Web GIS platform.(3)A multi-scale ANSP risk assessment visualization system in Chongqing based on Web GIS is designed and developed.Firstly,the demand is collected through field research,on-site communication and discussion;Then,according to the requirements documents and relevant data obtained from pre-processing,the B/S four-tier architecture development mode is adopted,and Vue.js,Java Script,ECharts and other front-end development technologies,as well as a series of Web GIS development technologies such as Leaflet like map interactive library GMap and Geo Server,to build a multi-scale ANSP risk assessment visualization system in Chongqing.Users can view and analyze the relevant data of ANSP in the form of map interaction and data chart,so as to provide some assistance and reference for the management,analysis,planning and decision-making of ANSP in Chongqing.To sum up,combined with GIS technology,cloud computing technology,front-end development technology and other related technologies,this thesis designs and builds a multi-scale ANSP risk assessment visualization system in Chongqing,an effective and feasible technical solution is proposed to control and prevent ANSP to a certain extent.