Remote Sensing Monitoring And Analysis Of Plateau Lake Water Body Change In Yunnan Province Based On Multi-source Remote Sensing Data And Gee Platform(1988-2018)

The nine plateau lakes in Yunnan Province cover an area of about 1042 km²,with a water storage capacity of about 302×10⁸m³,accounting for 13.6%of the total water resources in Yunnan Province.Plateau lakes play a significant role in the social and economic development and ecological civilization construction of Yunnan Province.As important parameters of lake changes,area,water level,and storage of lakes have become important indicators of global or regional climate and environmental changes influenced by climate and human activities.Based on multi-source remote sensing data,this study extracts the area of plateau lakes in Yunnan Province from 1988 to2018 and the water levels of Fuxian Lake,Erhai Lake,Dianchi Lake,and Chenghai Lake from 2002 to 2018.The changes in lake water storage capacity are estimated through the lake water area and the water level.By analyzing the temporal and spatial changes of lake water bodies in the Yunnan Plateau in the past 30 years and discuss the impact of regional climate change and human activities on the lake water changes in the Yunnan Plateau.The research results of this paper will provide theoretical methods and technical support for the management of plateau lakes and ecological environment protection in Yunnan Province.The main research content of the thesis includes the following aspects:1.The water area of nine plateau lakes in Yunnan Province from 1988 to 2018was extracted as follows:(1)The accuracy of each water index to extract the water area of each lake shows as follows:WI₂₀₁₅is the most suitable for rural lakes(Chenghai Lake,Fuxian Lake and Xingyun Lake).MNDWI obtains the highest extraction accuracy in lakes with more surrounding cultivated land such as Erhai Lake,Qilu Lake,Yangzonghai Lake and Yilong Lake,while AWEI_shobtains the highest extraction accuracy in lakes with urban background and water pollution(Dianchi Lake).NDWI_{Mc Feeters}is the most effective for lake water extraction from Lugu Lake;(2)On the whole,the area of the nine plateau lakes in Yunnan Province has changed dramatically over the past 30 years,and the overall trend has been decreasing first and then increasing slowly.From 1988 to 1998,the overall lake area fluctuated steadily.In 2018,the lake's total area first decreased and then increased,reaching a maximum of 1033.8 km²in 1994 and a minimum of 974.8 km²in 2013;(3)From the perspective of individual lakes,among the three large plateau lakes(>200km²),Dianchi Lake's area has changed a lot,and the area fluctuates the most during2006-2012.Among the other six smaller plateau lakes(<100 km²),Qilu Lake and Yilong Lake areas have the most extensive changes,and they have first decreased and then increased after 2010;(4)From the perspective of the changes in the dry/rainy season,Erhai Lake,Lugu Lake,and Yilong Lake fluctuate significantly in the dry/rainy season,while the other plateau lakes have no noticeable changes in the dry/rainy season;(5)The total area of the nine plateau lakes in 2001(wet year,1023.6km²)was greater than that in 2009(the dry year,1005.9 km²).The water area of Dianchi Lake,Erhai Lake,Lugu Lake,and Xingyun Lake was more extensive in 2001 than in2009,and the water area of the remaining five lakes did not change much between dry years and wet years.2.Based on the three satellite altimetry data of ICESAT-1/GLA14,Cryosat-2/SIRAL GDR,and ENVISAT/RA-2 GDR,this paper retrieves the water levels of Fuxian Lake,Erhai Lake,Dianchi Lake,and Chenghai Lake from 2002 to2018,using water level elevation.The fusion method obtains the water level change sequence.Through linear regression analysis of the water level sequence of the four lakes,it can be obtained that the average annual rate of change of Fuxian Lake,Erhai Lake,Dianchi Lake,and Chenghai Lake are-0.114 m/a,0.004 m/a,0.006 m/a,and-0.133 m/a,respectively.The goodness of fit(R²)of the straight line is 0.316,0.002,0.014,0.204,respectively.According to the comparison between the water level sequence extracted by satellite altimetry data and the measured water level sequence,the difference calculation is performed to obtain Fuxian Lake and Dianchi Lake the average difference between the water level extracted by Chenghai through satellite altimetry data and the actual water level is-0.409 m,0.374 m,and 0.09 m,respectively.3.Estimating the changes of lake water storage capacity based on changes in the area and water level of plateau lakes.Studies have shown that the estimated water storage volume of Fuxian Lake in 2018 increased by 0.078×10⁸m³compared with that in 2009,the rate of change is-0.0056×10⁸m³/a,showing a trend of decreasing first and then increasing.The estimated water storage capacity of Dianchi Lake in2018 has increased by 0.82×10⁸m³compared to 2009,the rate of change is0.059×10⁸m³/a,showing a slow increase trend;The estimated water storage volume of Chenghai Lake in 2013 decreased by 3.03×10⁸m³compared to 2009,the changing rate is-0.34×10⁸m³/a,showing a slowly decreasing trend.4.Analyzed the correlation between water body changes of nine plateau lakes in Yunnan Province and climate factors and human activities in this study.Results show that:(1)The lakes greatly affected by precipitation are Chenghai Lake,Dianchi Lake,and Fuxian Lake.During some periods,Its area and water level are significantly positively correlated with precipitation(R>0,p-value<0.05);(2)The lakes greatly affected by temperature are Chenghai Lake,Dianchi Lake,Fuxian Lake,Lugu Lake,and Yilong Lake.The lake area and water level are negatively correlated with the surrounding temperature(R<0);(3)The impact of human factors such as land use/cover change(LUCC),the implementation of policies,and related water conservancy projects on the lake area and water level changes,Dianchi Lake,Yilong Lake,Qilu Lake,Erhai Lake,and Fuxian Lake are affected by the intensity of human activities.In summary,climatic factors and human activities are important factors affecting the nine plateau lakes changes in Yunnan Province.