Study On Non-point Source Pollution In Songhuaba Reservoir Water Source Protection Zone Based On Land Use Change

With the control of point source pollution,non-point source pollution has become the main factors affecting water quality,the formation of non-point source pollution closely related to land use,the unreasonable land use will aggravate the non-point source pollution of water,the research of land use change affect the non-point source pollution has become a hot topic of research at home and abroad.The Songhuaba reservoir water source protection zone is an important water source of Kunming City,water quality is directly related to the safety of drinking water of millions of people in Kunming City,the months reservoir water quality monitoring data in 2016 from Kunming city environmental protection bureau show that reservoir water quality is wandering in ? class standard,only can be used as the minimum standard of drinking water.Agricultural land account for more than 1/4,a largely use of chemical fertilizers and pesticides pose a serious threat to water bodies.Since 2006,Kunming municipal government pay attention to the protection of water source area,the implementation such as returning farmland to forest and grass measures partly change the pattern of land use in water source area,therefore,under the background of land use change,studying the land use change impact on agricultural non-point source pollution has an important practical significance for protecting water quality,at the same time can also provide a scientific basis for the sustainable development of social economy.Based the TM image in the study area as data source,with“3S”technology support,deciphering the study area land use type graphics and analyzing land use a change,based on this,using output coefficient model to estimate the changeof non-point source pollutant TN and TP in the study area,in view of the research area special role in economic development in the city of Kunming,the paper put forward the non-point source pollution control measures,the main research content is as follows:(1)Preprocessing the TM image of 2007 and 2015,using supervised classification combined with artificial visual interpretation methods acquire the study area land use type graphics and land use data in the study area.The study analysis land use change,the result shows that:the land use has some change in the study area,mainly for arable land decrease,construction land?grassland?forest land?water and unused land increase.Analysis of dynamic degree of each land use type,arable land decrease with the annual speed of 1.64%,construction land growth significantly,the rest is water?grassland? unused land?forest land.The water source area landscape diversity index(SHDI)and evenness index(SHEI)increase,contagion index(CONTAG),Percentage of Like Adjacencies(PLADJ)decrease,which indicate that the study area land use types tend to be scattered,the exercise of the policy such as returning farmland to forest and grass intensify the change of landscape pattern in the study area.(2)This article selects output coefficient model suitable for the study area to calculated non-point source pollutant TN,TP load,the non-point source pollutant TN and TP produced by the land use have decreasing trend,TN load from 471.66 t in2007 fell to 446.06 t in 2015,reduce 25.6 t,TP load declined from 31.11 t in 2007 fell to 28.72 t in 2015,reduce 2.39 t;from the contribution rate of various land use to non-point source pollution,though arable land on the contribution rate of agricultural non-point source pollution has a decreasing trend,still about 70%,how to reduce the amount of non-point source pollutants produced by arable land is the key to improve the water quality in the study area.According to the analysis of water source area land use pattern and the changes of non-point source pollution,combined with the geographical conditions of the study area,putting forward the non-point source pollution prevention and control measures such as increasing proportion of forest land,the development of ecologicalagriculture,planning of vegetation filter belt,strengthening the construction of the ecological wetland to gives theoretical guidance to the water source protection.