Analysis Of Lake Water Area Changes And Causes In China Based On GF-1/6 Satellite Images

As an important carrier of surface water resources,lakes have many ecosystem functions,and are also an indicator of the impact of the earth's environment change and human activities.Lake water body area is an important indicator to characterize lake water volume and lake morphological changes.Studying lake water body area changes can find out the status of lakes,providing basic scientific data for the study of lake evolution laws under climate change and human activities,and sustaining lake water resources Utilization and management also have important guiding significance.However,current studies based on lake water area are often based on typical single lakes or lakes at a regional scale between years and years,and these studies often focus on long-term series of low-spatial resolution images.The successful networking of GF-1 and GF-6 have achieved a time resolution of 2 days for land area observations,which makes it possible to use remote sensing data with high time and frequency to reflect the changes in lake water surface area.This paper takes 2865 lakes with an area greater than 1.0km~2in the first national water conservancy survey as the research object,uses GF-1/6 remote sensing images with high temporal and spatial resolution as the data source,and uses the automatic extraction method based on spatial constraint vectors to obtain water bodies area,comprehensive use of RS and GIS technology to analyze its inter-annual and intra-annual spatio-temporal change characteristics,and visual interpretation methods to obtain the type of lake water change as the starting point for driving factors,combined with human data and meteorological data to illustrate the possible impact on lake changes factors,finally quantitatively get the dominant factors affecting the lake area with the gray correlation degree.Conclusion as below:(1)The number of lakes in the country is gradually decreasing,but the area is gradually increasing,the law of lake area changes in different regions is different.By classifying the lakes with an area of more than 1.0km~2across the country from 1 to 10,10 to 50,50 to 100,100 to 500,500 to 1000,1000 to 2000,and greater than 2000,it is found that about 70%of the lakes are concentrated area in the interval of 1?10km~2,although the total number of lakes in each year is decreasing year by year,because the decreased lakes are mainly concentrated in smaller areas,and the number of lakes with larger areas has increased,the area of lakes has shown a trend of increasing year by year.In addition,the lake area and number of lakes at different regional scales have different changing trends,the number of lakes and the area of lake area change are relatively stable in areas with a small number of lakes,mainly in the Pearl River Basin and Southeastern River Basins,while areas with a large number of lakes the number and area changes of lakes are also relatively complex,mainly in the northwestern river basin and the Yangtze River basin.(2)Lake water bodies at the national and regional scales change significantly during the year,and the law of water body changes in different years is inconsistent,but it has a certain seasonality.In the summer of 2018 and 2020,the lake has the largest water body area,followed by autumn,with the largest area being 235975.43km~2and 241946.55km~2respectively;the largest area in the summer of 2019,followed by spring,with the largest area being 238181.85km~2.Regional lakes have inconsistent changes during the year,the northern basin has smaller lake water areas in July,August and September,but larger water areas in December,January and February,such as the Songhua River Basin and the Yellow River Basin,Huaihe River Basin;the flood season of southern waters is relatively concentrated in July,August and September,for example,in the Yangtze River Basin,especially the seasonal lakes such as Poyang Lake and Dongting Lake,which fluctuate significantly during the year,the area of the lakes varies by more than 1,000 square kilometers within a month,which has a great impact on the trend of lake water body changes across the country.There are obvious differences in changes in different administrative regions during the year,Jiangxi Province and Hunan Province have great fluctuations during the year,while Fujian Province,Beijing,Guizhou Province,and Shanghai have relatively stable changes during the year.(3)Nearly two-thirds of the country's lakes have changed,including 1,019 lakes with a shrinking area and 846 lakes with an expanding area,among the lakes with a shrinking area,728 lakes have no encroachment,and 291 lakes have been invaded by humans,these two types of lakes are mainly small lakes of 1?10km~2.Lakes with changes in lake area tend to be clustered and distributed,while lake changes show obvious differences in spatial distribution,the area of lakes is shrinking in the north,especially in the Inner Mongolia Autonomous Region,and the south is dominated by various encroachments,the typical representative is Hunan Province and Hubei Province,the area of lakes centered on the Tibet Autonomous Region and Qinghai Province has stabilized,and there are even many lakes showing a trend of expansion.In addition,the leading factors that cause lake area changes in different regions are different,for example,Hubei Province is dominated by meteorological factors and is significantly affected by precipitation,but at the same time,the increase in aquaculture and irrigation area also has auxiliary effects to a certain extent;the change in lake area in Inner Mongolia Autonomous Region is dominated by human factors,the increase in effective irrigation area and livestock production leads to serious loss of soil moisture,which has become the main driving factor affecting the decrease in lake area.