Research On The Response Of Land Use/Cover Change And Lake Non-point Source Pollution In Dianchi Lake Basin

Land use/cover change(LUCC)research is currently a hot spot in global change research.The hydrological cycle of a river basin is simultaneously affected by climate change and LUCC.Most hydrological response studies focus on the impact of future climate change on runoff,but ignore the future.The role of LUCC;in the study of lake environment,hydrological stability and water quality safety are the basis for sustainable lake environmental health;lake environment is being affected by climate change and LUCC on a global scale,and the impact of LUCC on lake non-point source pollution has been Become the top priority of research in the field.How to establish a sustainable development of land resource utilization and environment of lake response strategy is one of the global problems that contemporary people need to solve urgently.This paper uses GIS spatial analysis methods and remote sensing object-oriented classification technology to classify and study the change process and characteristics of LUCC in the Dianchi Lake Basin from 2000 to 2020,and calculate the ecological service value of the basin at different times,and then use the soil and water assessment tool set model(SWAT),substituting the data of soil,climate,topography,LUCC at each time period,water system,hydrology and water quality in the study area,scientifically analyze the response of changes in watershed land use to non-point source pollution of lakes.The specific performance is:(1)LUCC is mainly affected by urbanization and agricultural industry upgrading.Since 2000-2020,the expansion of construction land and the decrease of arable land are the general trends.In 2000,the proportion of arable land in Dianchi Lake dropped from 39.24% to 25.02% in 2020,and the area of arable land decreased by about400km2;while construction land increased from 7.86% in 2000 to 22.67% in 2020,and the area expanded to nearly three times the original size.In addition,the proportion of forest land decreased by 0.3% compared with 2000,and the proportion of garden land increased by 0.36%.It can be seen from the comprehensive dynamic degree table that the fastest change is from 2010 to 2015,the comprehensive dynamic degree of the Dianchi Lake Basin is 0.82%/a;the second is from 2015 to 2020,the comprehensive dynamic degree is 0.60%/a,which is 2005-In 2010,the comprehensive dynamic degree was 0.43%/a.From 2010 to 2020,the comprehensive index of land use degree gradually increased.Estimating the changes in the ecological service function of LUCC in the Dianchi Lake Basin from 2000 to 2020.From the perspective of the overall ecological service value,the overall ecological service value of the Dianchi Lake Basin gradually fluctuates and declines from 2000 to 2020,and the five periods are 3.145 billion yuan respectively./Year,3.050 billion yuan/year,2.979 billion yuan/year,3.069 billion yuan/year,and 2.978 billion yuan/year.(2)The model simulation verification results confirmed that the SWAT model has good applicability in the Dianchi Lake Basin,and the SWAT model established in this paper is suitable for further studies such as simulation and prediction in the Dianchi Lake Basin.According to the estimation of the SWAT model,the comparison of the indicators in the Dianchi Basin in 2000 and 2020 shows that: total precipitation decreased by 115.1%,surface runoff increased by 55.2%,lateral flow increased by48.3%,groundwater inflow to rivers increased by 93.5%,and water production increased by 43.5 %,the amount of sand production decreased by 10.9%,the amount of soil loss decreased by 83.9%,the amount of nitrogen fertilizer application increased by 57.5%,the yield of phosphorus in the sediment decreased by 169.8%,the amount of nitrogen absorbed by plants increased by 53.3%,and the amount of phosphorus absorbed by plants increased by 56.1% The amount of nitrate in the surface runoff increased by 87%,the biomass increased by 62.90%,the leaf area index at the end of the period increased by 1.7%,the total nitrogen of the main channel decreased by 192.9%,and the total phosphorus of the main channel decreased by 238.9%.(3)The Logistic-CA-Markov model predicts the LUCC situation under the two periods of sustainable development scenarios in 2030 and 2050,and uses the overlay analysis function of GIS spatial analysis to quantitatively understand the changes of land types.The results show the temporal and spatial changes of land use in the study area from 2000 to 2050.On the whole,cultivated land has decreased year by year,construction land has increased due to policy constraints,and has increased and declined.Grassland has also shown a trend of increasing after decreasing,water bodies have remained generally stable,and woodland has remained generally maintained.Stable,road facilities increase first and then stabilize.Regarding temperature and precipitation,this article uses the high-resolution data set NASA Earth Exchange/Global Daily Downscaled Projections(NEX-GDDP)released by the National Aeronautics and Space Administration to extract regional precipitation and temperature data from 2017 to 2099,and re-run the SWAT model.The response results of non-point source pollutants in the river basin to LUCC show:From 2020 to 2030: total precipitation will increase by 53.05%,surface runoff will be reduced by 82.05%,lateral flow will be reduced by 99.60%,groundwater flow into rivers will be reduced by 56.92%,water production will be reduced by 76.94%,sediment production will be increased by 91.86%,and soil loss will be reduced Increase by 94.37%,reduce the amount of nitrogen fertilizer by 117.82%,increase the yield of phosphorus in sediment by 66.87%,reduce the amount of nitrogen absorbed by plants by 99.30%,reduce the amount of phosphorus absorbed by plants by 95.87%,and reduce the amount of nitrate in surface runoff-345.87%,The biomass decreased by-76.88%,the leaf area index at the end of the period increased by 0.81%,the total nitrogen in the main channel increased by 67.30%,and the total phosphorus in the main channel increased by 72.39%.Under the sustainable development scenario between 2030-2050: total precipitation increased by 3.27%,surface runoff increased by 6.54%,lateral flow increased by 0.70%,groundwater flow into rivers increased by 3.39%,water production decreased by 3.42%,and sediment production increased 9.18%,soil loss increased by 6.31%,nitrogen fertilizer application increased by 5.44%,phosphorus production in sediment increased by 8.97%,nitrogen absorption by plants decreased by 4.73%,phosphorus absorption by plants increased by 3.86%,and nitric acid in surface runoff The salinity increased by 3.33%,the biomass increased by 2.14%,the leaf area index at the end of the period increased by 1.34%,the total nitrogen in the main channel increased by 0.78%,and the total phosphorus in the main channel increased by 0.82%.To sum up,it can be predicted that the watershed area can guarantee 30% of cultivated land,20% of grassland,16% of woodland,more than 11% of water and less than 17% of construction land,and the watershed ecological service function can be achieved.Tend to be optimized to realize the sustainable development of the LUCC structure.