Estimation Of Non-point Source Pollution Load And Its Response To Land Use Change In The Nansihu Basin

With the rapid development of human society and economy,water shortage was becoming more and more obvious in China;The decline of water quality caused by non-point source pollution is an important factor in the shortage of water resources.Non point source pollution,which caused the deterioration of water quality and eutrophication of the water body,brought about other ecological and environmental problems,such as wetland degradation,which was a serious threat to the production and life of human beings and the sustainable development of society and economy.It was necessary to provide important theoretical basis and technical support for the study of watershed pollution prevention and sustainable development of ecological environment by carrying out research on the spatial and temporal pattern of non-point source pollution,evolution characteristics of control zoning and the effect of land use.Therefore,combined with remote sensing(RS),geographic information system(GIS)and related non-point source pollution model,the regional non-point source pollution load was quantitatively studied by considering the factors such as land use type,livestock breeding and population.Analysis of the spatial distribution pattern and key research on factors affecting land use can promote the sustainable development of regional resources and the environment,and promote the coordinated development of human production,life and social economy.In this study,the Nansi Lake Basin was used as the research object,and based on the 3S technology,the output coefficient model and the equal-standard pollution load method were used to analyze the spatio-temporal evolution characteristics of nitrogen and phosphorus non-point source pollution from 1990 to 2013,to explore the main pollutants and the main source of the non-point source pollution and the most active units of affecting the TN,TP changes,and to analyse the evolution of nitrogen and phosphorus pollution control zoning by cluster analysis.Based on the analysis of land use change,dynamic analysis,spatial dynamic analysis and transfer matrix analysis,the trend of land use change was discussed since 1990,and the response of watershed non-point source pollution load to land use change was investigated by using some conceptions such as contribution rate and unit contribution rate index in nearly 24 years.The main conclusions of this paper are as follows:(1)During the period from 1990 to 2013,the average annual emissions of non-point source TN and TP in the Nansi Lake Basin were 182660.43 t/a and 10335.53 t/a,respectively,and the trend first rises,then falls,and finally goes smoothly.The main pollutants of non-point source pollution are TN;The main pollution source of TN is land use;The main pollution source of TP is agricultural life and livestock breeding;Precipitation is the most active unit that affects TN,TP changes.(2)Pollution level of TN and TP of the non-point source pollution in the Nansi Lake Basin is not uniform.In general,the pollution degree in the lake west area is more serious than that in the east,and there is a narrowing tendency in regional differences of pollution levels.Lake West area is the key management area,and Beisha River Basin,Guangfu River Basin and Liangji Canal River Basin are priority control and key management area.(3)Among the six types of land use,the area of construction land and water area has increased,and the area of cultivated land,woodland,grassland and unused land has decreased,and the magnitude of the change is sorted as follows: Construction land > Cultivated land > Waters > Woodland > Grassland > Unused land.UCI is more objective than the contribution rate to reflect the impact of land use on non-point source pollution,and the impact of cultivated land on non-point source pollution is higher,and other types of land use are less affected and have little difference.