Lake Dynamic Monitoring And Regional Climate Response Analysis In The Source Region Of Three Rivers Based On Time Series

As the place where the three major sources converge,the Three-River Source Region has important ecological functions such as ecological water storage,water conservation,and climate regulation.It is also a key national protection area in recent years.The dynamic changes of its lakes play an important role in the regional water cycle.In order to explore the long-term temporal and spatial changes of the lake area in the Three Rivers Source Region,this paper chooses 1990-2020 as the research period.Aiming at lake water bodies with complex backgrounds and large areas,a cloud platform based on Google Earth Engine combined with NDWI water bodies is proposed.Index,Canny edge detection algorithm and Otsu algorithm construct a ‘global-local'semi-automatic lake extraction method,select Landsat 5,7,8 data in this period,and extract the three river source areas in 1990,1995,2000,2005,2010,2015,and 2020's seven periods of data on the distribution of lakes with an area of more than 1km~2.And from the perspectives of the overall number and area of lakes,the number and area of lakes in different areas,the temporal and spatial distribution characteristics of lake changes,lakes in different basins,lakes with different replenishment types,and typical lakes,the dynamic changes of lakes in the study area over the past 31 years are analyzed.Finally,combined with the monthly data of 21 meteorological stations in the study area,the response of lakes and typical lakes in the whole area to regional climate elements such as precipitation and temperature is discussed,which will provide information for the safety and management of water resources and the construction and restoration of ecological environment in the Three-River Source Region in the later period.Effective support.The main conclusions of the paper are as follows:(1)The semi-automatic lake information extraction method based on GEE-based NDWI water index combined with Canny edge detection and Otsu algorithm can effectively segment the water and land boundaries to obtain refined lake extraction results.(2)In the nearly 30 years from 1990 to 2020,the total area and number of lakes larger than 1km~2 in the Three Rivers Source Region showed a trend of first decreasing and then increasing.Among them,in the two time periods of 2005-2010 and 2015-2020,the total lake area increased the most significantly,while the number of lakes increased most significantly from 2015 to 2020,with a sharp increase of 107 in 5 years;from lakes in different areas In terms of the overall change law: the larger the lake area,the more stable the number of lakes.Smaller lakes(1.0?A<2.0)have the most obvious fluctuations;in 31 years,the number of stable lakes has changed little,basically maintained a balance,and the extent of lake expansion is more obvious,mainly concentrated in Zhiduo County,Maduo County and Golmud In terms of lake basin distribution,lakes larger than1 km~2 are mainly concentrated in the source area of the Yangtze River and the source area of the Yellow River.In the source area of the Lancang River,there have been only one or two lakes in the past 30 years,and the lake area and quantity change trends in different basins are not consistent.(3)The changes in 7 typical lakes in the study area show that there are certain differences in the area changes between lakes under different recharge types,geographic environments,and climates,and the changes in lake area may be jointly controlled by these factors.(4)In the past 30 years,the changes in the total area of lakes in the Three-River Source Region are the result of the combined effects of temperature and precipitation,of which the effect of temperature is more significant.In different regions,the lake area responds differently to climatic factors,which is also related to the way the lake is recharged.