Study On The Impact Of Land Use Change On Water Quality (River Network) In The Three Gorges Reservoir Area Based On GIS And RS

The Three Gorges Project has attracted worldwide attention.It is a hundred years of water conservancy construction in China.It is a key measure to comprehensively control the flood control problem in the middle and lower reaches of the Yangtze River.It also has huge comprehensive economic benefits such as power generation,shipping,irrigation,water supply and development.But it also brings a series of ecological and environmental problems,especially the tributary of the Yangtze River in the reservoir area.On the one hand,the hydrological dynamics of the river are cyclical,such as the decrease of the flow velocity,the increase of the water depth,and so on.On the other hand,because of the rapid economic development in the reservoir area,the land use in the tributaries of the reservoir area has also changed significantly,such as the increase of urban construction land and the reduction of forest land use.Which are a serious threat to the reservoir area of the Yangtze River tributaries of the water quality,data show that hydrological changes lead to tributary eutrophication occurred more frequently,urbanization led to the growing domestic sewage and industrial wastewater discharge.In order to understand the response relationship between the Three Gorges reservoir area and the water quality of the tributaries in the reservoir area,this paper takes the 43 watersheds with the basin area of 100km2 in the Chongqing area as the research object,using the geographic information software ArcGIS and the remote sensing software ENVI to the reservoir river This paper analyzes the dynamic change of land use in the Three Gorges Reservoir area from the space and time,and analyzes the spatial and temporal changes of land use and the spatial variation law of Jialing River Basin.On this basis,,And the non-point source pollution load of each basin was calculated.Taking the Canowing River as an example,the Canoco analysis software and the statistical analysis method were used to study the relationship between land use and water quality of Yulin River.The main conclusions are as follows:(1)Access to basic river basin data and land use data.1)Through the ArcGIS analysis software to compute the DEM elevation map of the Three Gorges Reservoir area,the river network of the Three Gorges reservoir area is obtained,and the catchment watershed is generated according to the water outlet in the river network.There are 43 tributaries in the reservoir area greater than 100 km2.2)Using the Landsat series image,the remote sensing image classification was completed by using the decision tree classification method,and 129 land use maps of 43 watersheds in the Three Gorges Reservoir area in 1995,2005 and 2015 were generated.(2)This paper analyzes the present situation of land use in the Three Gorges reservoir area in 2015,and the proportion of vegetation and cultivated land in the basin is about 92% of the total area of Chongqing section of the Three Gorges reservoir area,and the proportion of land for construction and water is relatively low Accounting for 5.91% of the total area,1.92%,land use rate is low.(3)The spatial and temporal changes of land use in the Chongqing section of the Three Gorges Reservoir area were analyzed.1)The number and extent of land use in the Three Gorges reservoir area are analyzed.On the whole,the change of the basin is different in 20 years.From 1995 to 2005,the increase of construction land is the Jialing River basin.Xiaojiang River Basin;the largest increase in vegetation is the small river basin,the largest reduction is the Jialing River;cultivated land is the largest increase in the Ganjing River Basin,Longxi River to reduce the most.05 to 15 years,the largest increase in construction land is still the Jialing River Basin;the largest increase in the waters of the Lixiang River;vegetation is the largest increase in the Daning River Basin,the largest reduction is the Wujiang River Basin;the largest increase in cultivated land is Longxi River,Most of the Long River Basin.2)In terms of land use,the degree of land use in the last ten years is much higher than that in the previous ten years.In 1995,the largest land use level was Huaxi River.The land use level was the highest in 15 years,and the land use The degree of change is a large fish Creek River,indicating the fish Creek land use in a relatively rapid development period.3)The spatial and temporal transfer of land use is analyzed by Jialingjiang as an example.The results show that the land area with the largest area change is the vegetation land,followed by the cultivated land,the largest part of the vegetation and the land for cultivated land;the largest part of the land area Is the construction land.Among them,the main transfer type of vegetation is cultivated land;the main transfer type of cultivated land is construction land;construction land is the largest type of vegetation.4)The analysis of the Jialing River basin through the center of gravity and the standard deviation ellipse showed obvious differentiation characteristics.The distribution center of the construction land moved southward and then moved northward,and the degree of dispersion was reduced.The distribution of cultivated land and vegetation land moved northward,The degree of dispersion has increased,the water area as a whole to the east of a small amount of offset.Five sites of land size: lake> cultivated land> vegetation> river> construction land.(4)In the Three Gorges Reservoir area,the chemical oxygen demand,ammonia nitrogen,total nitrogen and total phosphorus in the Three Gorges Reservoir area were 8.54 × 105 t?3.91 × 104 t?9.46 × 104 t?6.52 × 103 t? Among them,livestock and poultry farming contributed the most to COD and TP,and the contribution of cultivated land to NH3-N was the highest,and vegetation contributed the most to TN.(5)And discusses the multi-scale response relationship between land use type and river water quality in Yulin River Basin.Land use type on the river water quality,the land use type,in the smaller spatial scale,the construction land and cultivated land is the main factor affecting the water quality,and in the larger spatial scale,the construction land and the vegetation is the land Is the main factor affecting water quality.And the seasonal difference of land use relation to river water quality is obvious.The construction land has a positive correlation with river water quality in dry season and wet season,and vegetation has negative correlation,while cultivated land is strong in wet season,Quarter was significantly weakened,showing a positive correlation between the weak points.