Research On Changes In Poyang Lake Basin In The Past 20 Years Based On Multi-source Remote Sensing Data

Poyang Lake is the largest freshwater lake in China.Continuous monitoring of hydrological changes in Poyang Lake can provide basic data for ecological environment changes in the basin.Due to the influence of the basin shape of Poyang Lake and the environmental climate,the water area and the surrounding wetland have significant seasonal dynamic changes.With the help of real-time,dynamic and periodicity of remote sensing technology,lakes and wetlands can be monitored on a large scale and in time.In this study,multi-source remote sensing data were used to monitor the annual and interannual changes of the water area and wetland in Poyang Lake.In the view of 2020China floods,a remote sensing quantitative estimation of the flood storage potential of the lake reservoir in Poyang Lake Basin was conducted.The content of this paper mainly includes the following aspects:⑴The Monthly Water History of Poyang Lake’s Global Surface Water from 1999 to2018 was obtained based on Google Earth Engine.The seasonal water history of Poyang Lake was synthesized to study the long time series changes of the Water area of Poyang Lake in 76 seasons.Due to the lack of some seasonal water history,the water flooded frequency obtained by percentile segmentation were used to reconstruct the complete water boundary of Poyang Lake on a quarterly basis to analyze the seasonal variation of the water area of Poyang Lake.The results show that the area of Poyang Lake has significant inter-annual variation and obvious seasonality.In summer and autumn,the area of water is slightly higher in summer than in autumn,but the opposite is true in some years,such as 2005 and 2008.The water area in the wet season is usually larger than that in the dry season,but the water area in the autumn of 2006 is the smallest throughout the year.⑵All available images from Sentinel-1&2 and Landsat-8 satellites during 2017-2019are used to carry out remote sensing classification and information extraction of wetlands in the study area by Random Forest classification(RF)on GEE.The results show that using the advantages of massive remote sensing images in the continuous macroscopic monitoring of wetlands,this paper analyzed the characteristics of inter-annual and intra-annual spatial and temporal dynamics of Poyang Lake wetlands.Sentinel-1&2 and Landsat-8 provide a good data basis for monitoring the dynamic changes of Poyang Lake wetland.According to the statistical analysis of the 3-year classification results,the characteristics of dynamic changes of each wetland type were observed during the year.In February of each year,the area of mudflat and grass reaches the maximum,while the area of water is the minimum.In June and July of each year,the area of water reaches the maximum,and the area of mudflat and grass reaches the minimum,with obvious seasonal changes.The classification of monthly time series can more accurately explain the monthly and seasonally changes of wetland types.⑶Against floods in the Poyang Lake basin in southern China in 2020,obtain the GEE platform in January 2020 to October all available not phase Sentinel-1 images at the same time,the Edge Otsu algorithm,the Poyang Lake Basin is greater than 1 km~2 of lakes and reservoirs for water extraction,respectively in combination with the extraction of waters of lake basin terrain and SRTM DEM of Poyang Lake Basin of lakes and reservoirs water storage capacity estimation.The results show that Sentinel-1 is capable of providing high temporal resolution data for monitoring the dynamic changes of water area in Poyang Lake,and the accuracy of Edge OTSU algorithm is over 95%.The water extraction effect is good,and the total water area of Poyang Lake and other lakes and reservoirs in the Poyang Lake Basin showed the same change trend,showing a single peak trend of increasing first and then decreasing.DEM combined with the vector boundary of the lake and reservoir,combined with the empirical formula,can estimate the lake reserves,and understand the flood regulation and storage effect of lakes in the Yangtse River from the perspective of the change of lake and reservoir water quantity.From January to October in 2020,the maximum throughput of Poyang Lake is 12.18 km~3,the total throughput of other lakes and reservoirs greater than 1km~2 in the Poyang Lake Basin is 2.94 km~3,and the flood storage capacity of Poyang Lake Basin is 15.12 km~3.