Research On The Impact Of Land Use Change In The Middle Reaches Of Tumen River On Non-point Source Pollution Based On FLUS Model And SWAT Model

Non-point source pollution has the characteristics of randomness,complicated migration and transformation mechanism,and large temporal and spatial variation.According to the 2010"First National Pollution Source Census Bulletin"data,non-point source pollution has become the main source of pollution in my country’s water bodies and the main reason for the deterioration of lake water quality in my country.This study selects the Burhatong River Basin of the Tumen River as the study area,uses the SWAT model to simulate the non-point source pollution of the Burhatong River Basin,analyzes the characteristics of land use changes from 1986 to 2016,and uses the SWAT model to analyze different lands Utilizing the impact of changes on the non-point source pollution of the watershed,using the FLUS model to simulate the land use under different scenarios in the watershed in 2036,and then using the SWAT model to evaluate the characteristics of non-point source pollution under different land use scenarios.The main findings of this study are as follows:(1)Based on the e Cognition9.02 software,the Landsat images of the Burhatong River Basin in 1986,1996,2006,and 2016 were classified by object-oriented,and finally the four phases of the land use classification map of the Burhatong River Basin in 1986,1996,2006,and 2016 were obtained.Through comparative analysis of the land use map of Phase IV,it is found that woodland is the main land use type in the Burhatong River Basin,and the area of woodland increased by 3577hm~2from 1986 to2016.Due to the early reclamation history,the proportion of agriculture in the watershed was second only to forest land,reaching 23.36%in 1986,but it was reduced to 22.80%in 2016.From 1986 to 2016,construction land showed a trend of continuous expansion,and its area accounted for an increase of 0.66%,while the remaining land use types only changed slightly.(2)Collecting and sorting out the spatial data and attribute data required by the SWAT model,constructing the Burhatong River Basin SWAT model,conducting sensitivity analysis on the model parameters,and selecting 23 parameters that have a greater impact on runoff and water quality.Use SWAT-CUP software to calibrate and verify the sensitivity parameters,and evaluate the accuracy of the model combined with the measured data at the lower stations of Mopanshan and Yanji.The R~2and N_Sof the runoff during the calibration period reached 0.91 and 0.91,respectively.R~2and N_Sreached 0.78 and 0.69,respectively.The R~2and N_Sof total phosphorus in the calibration period were 0.76 and 0.72,respectively.The R~2and N_Sin the verification period were 0.92 and 0.86,respectively.The R~2and N_Sof total nitrogen in the calibration period were 0.79 and 0.79,respectively.0.61,the results show that the constructed SWAT model can simulate the hydrology and water quality of the basin.(3)Using different land use data as the research basis to analyze the impact of land use changes on non-point source pollution,the contribution rate of different land uses to non-point source pollution is also different.Based on the pollution output information of 601 hydrological response units output by SWAT,the output intensity of nitrogen and phosphorus in different land uses was analyzed.In the Burhatong River Basin,the land use types that have a greater contribution to non-point source pollution are farmland,construction land,and woodland in order.In terms of total nitrogen and phosphorus input load:between 1986 and 2016,the output intensity of total nitrogen dropped from 379.6 kg/hm~2to 375.8 kg/hm~2,and the output intensity of total phosphorus dropped from 75.6 kg/hm~2to 71.3 kg/hm~2.The output of total nitrogen and phosphorus showed a downward trend.In terms of spatial distribution characteristics:the spatial distribution of total phosphorus is basically the same as that of total nitrogen.The areas with larger loads are mainly the areas where farmland and towns are concentrated in the lower reaches of the basin and the low-lying areas on both sides of the river.(4)After preparing the driving factor data required by the FLUS model,based on the 2006 land use data,adjust the model parameters to simulate the land use of the river basin in 2016 and compare with the actual land use.Kappa coefficient>0.75,simulation accuracy The future land use of the watershed can be simulated.A natural development scenario,an economic development scenario,and an ecological development scenario are set up,and the land use change under these three scenarios in the basin in 2036 is simulated.Natural development scenario:forest land increased by2%,farmland decreased by 2%,and the rest of the land remained basically unchanged.Economic development scenario:forest land decreases by 3%,farmland increases by1%,construction land increases by 2%,and the rest of the land use types remain unchanged.The third ecological protection scenario:increase of forest land by 3%,decrease of farmland by 3%,and slight changes in the use of the remaining land.(5)Using the land use maps of the three scenarios simulated by the FLUS model as the input data of SWAT to simulate the non-point source pollution output load under different scenarios in the basin in 2036,the results show that:under the ecological development scenario,the Burhatong River Basin in 2036 The annual output intensity of total nitrogen is 357.4kg/hm~2,and the output intensity of total phosphorus is63.9kg/hm~2.Under the economic development scenario,the annual output intensity of total nitrogen in the Burhatong River Basin in 2036 is 384.9 kg/hm~2,and the output intensity of total phosphorus is 75.5 kg/hm~2.Under the condition that the land use change of the watershed is not disturbed by policy,simulation of non-point source pollution under the natural scenario of 2036 found that the annual output intensity of total nitrogen is 363.4kg/hm~2,and the output intensity of total phosphorus is65.8kg/hm~2.Compared with 2016,under the natural and ecological development scenarios,the non-point source pollution of the river basin will continue to improve,while the non-point source pollution load risk under the economic development scenario will increase.