Study On The Assessment Of Pollution Loads Of Tuojiang River Watershed In Sichuan Province And Its Management System Development

The Tuojiang River watershed is a first-order tributary of the Yangtze River,its water quality plays an essential role in the Sichuan province and the total Yangtze River.In recent years,the rapid development of social economy in the watershed has led to prominent water environment pollution,which has become a prominent bottleneck restricting the high-quality development of the watershed.The assessment of pollution loads and the development of its management system are important prerequisites for implementing pollutants control policies to improve water environment.Therefore,this study established a study framework that includes pollution loads estimation,driving factors identification,multi-scenario prediction and management system development,to study the pollution loads of Tuojiang River watershed,in order to provide theoretical and technical support for improving the water environment quality the watershed and ensuring the water ecological security of the upper reaches of the Yangtze River.Firstly,using pollutants discharge coefficient method,this study separately estimated COD,NH₃-N,TN and TP pollution loads from seven pollution sources in the 28 districts（counties）of Tuojiang River watershed from 2007 to 2017,including industrial point sources,urban domestic,rural domestic,rural domestic waste,agricultural runoff,agricultural solid waste and livestock and poultry breeding pollution sources,and then analyzed their spatial and temporal distribution characteristics and spatial correlation and identify their crucial socio-economic driving factors.Secondly,this study established a modified pollutants discharge coefficient method by introducing social and economic driving factors,then predicted pollution loads from urban domestic and agricultural non-point sources in each district（county）from 2018 to 2030 based on the modified method,and explored their temporal and spatial variation characteristics.Then,applying the STIRPAT model,this study identified the crucial socio-economic driving factors of pollution loads in each district（county）,and then explored the change trend of pollution loads in each district（county）from 2018 to 2030 by scenario analysis method.Finally,this study developed a watershed pollution loads management system using Spring Boot and Vue.js framework.The main research results are as follows:（1）From 2007 to 2017,COD,NH₃-N,TN and TP all showed an increasing trend,among which the increase of COD pollution load was the largest,which was 74.65×10³t.Urban domestic and livestock and poultry breeding are the main pollution sources of the four pollution loads.The districts（counties）with higher pollution loads are mainly concentrated in the midstream.COD,NH₃-N,TN and TP pollution loads all had strong positive spatial correlation.The influence of socio-economic driving factors on pollution loads has obvious spatial heterogeneity,and the total population is the main factor promoting the increase of four pollution loads.（2）From 2017 to 2030,COD,NH₃-N,TN and TP pollution loads all will increase rapidly,and the increments will be 3816.38×10³t,255.15×10³t,467.06×10³t and 64.16×10³t,respectively.Urban domestic and livestock and poultry breeding will still be the main pollution sources.The districts（counties）with higher COD,NH₃-N,TN and TP pollution loads will be distributed in Xindu,Longquanyi,Ziliujing,Jiangyang districts and Anyue county.（3）From 2017 to 2030,COD,TN and TP pollution loads will increase under RS,MS,SS and NS scenarios.Concretely,the increase of COD pollution load will be the largest under NS scenario,which will be 143.23×10³t.The increase of TN and TP pollution loads will be the largest under RS scenario,which will be 30.52×10³t and 16.11×10³t,respectively.The NH₃-N pollution load will increase under RS,MS and NS scenarios,and decrease under SS scenario.The increase of NH₃-N pollution load will be the most obvious under RS scenario,with an increase of 43.40×10³t.In the setting four scenarios,the districts（counties）with higher COD,NH₃-N,TN and TP pollution loads will be distributed in the midstream and downstream.（4）The watershed pollution loads management system was designed and developed by using the Spring Boot and Vue.js framework.It can realize the estimation,correction and prediction of COD,NH₃-N,TN and TP pollution loads from seven pollution sources,including industrial point source,urban domestic,rural domestic,rural domestic waste,agricultural runoff,agricultural solid waste and livestock and poultry breeding pollution sources,as well as the download and data visualization of pollution load calculation results.It has the advantages of fast operation,simple operation,strong scalability and easy maintenance.The assessment framework of watershed pollution loads and their management system were designed and developed in this study,which can be applied to assess pollution loads in other similar watershed,expanding the research scope of watershed pollution load.Moreover,the conclusions drawn from this study have certain reference significance for restoring the water environment quality of the Tuojiang River Basin and protecting the water ecological security of the upstream of the Yangtze River.