Study On The Spatial Influence Of Land Degradation On Water Quality Of Dianchi Lake In Dianchi Lake Watershed

Land Use and Land Cover Change?LUCC?is an important factor affecting the change of water environment in the watershed,and it is the main driving force for the change of natural environment and ecological environment.The Dianchi Lake water-shed is the region with the highest urbanization rate in Kunming.Due to the unreason-able exploitation and utilization of its land natural resources and the discharge of a large number of pollutants into the lake,the water environment pollution in the watershed is aggravated.The Dianchi Lake watershed in Kunming is regarded as the research area in this paper.Based on the Landsat remote sensing images of nearly 20 years and the water quality monitoring data from 1998 to 2014,the spatio-temporal variation process of land use and water quality in Dianchi Lake is revealed by remote sensing?RS?,ge-ographic information system?GIS?and mathematical statistics.The distance attenua-tion function and spatial influence model are used to discuss the change of water envi-ronment in Dianchi Lake caused by land use change.The results show that:?1?In recent20 years,cropland has been largely transformed into construction land,woodland,un-used land and grassland,and the area of construction land and woodland has increased significantly?P<0.001?,the area of cultivated land and grassland has decreased sig-nificantly?P<0.001?,and the area of unused land was fluctuating upward trend?P<0.05?.?2?From 1998 to 2014,the variation trend of various water quality parameters was significant,the comprehensive trophic level index?TLI?of Caohai was signifi-cantly reduced,and the improvement effect of Waihai water quality was not obvious.?3?There is a clear correlation between the spatial difference of land development type and the water quality of lake is comprehensively affected by various land use types.COD_Mn and DO of Waihai are comprehensively affected by construction land,wood-land,cropland and grassland.Construction land and cropland have a strong correla-tion with COD in Caohai,BOD and TP in Waihai.It shows that the urbanization inten-sity of Dianchi Lake watershed has been further intensified in the past 20 years,and the land degradation in Dianchi Lake watershed represented by the impervious surface expansion is the main cause of eutrophication in Dianchi Lake.