Changes In The Dynamics Of Endorheic Lakes In The Alpine Regions Of Central Asia Over The Last 30 Years

Lakes serve as crucial indicators of regional climate change and also play indispensable roles in maintaining the regional ecological balance.Central Asia is broadly defined as the central region of Asia,stretching from the Caspian Sea in the west to the Daxing’an Mountains in the east,from the Altai and Sayan Mountains in the north to the Himalayas in the south,precipitation is scarce in the region and evapotranspiration is high.The highland and alpine regions are the main areas of water resource formation in the arid zones of Central Asia,and the changes in lakes in these regions are indicative of environmental changes in mountainous areas and are also important for understanding the formation of water resources in mountainous areas.Previous studies of lakes in Central Asia have focused on densely populated oases with high human activity,and have monitored large plain coccyx lakes,while systematic and comprehensive observations and analyses of small highland and alpine endorheic lakes are still lacking.In this study,8 typical endorheic lakes,namely Lake Karakul,Lake Issyk-Kul,Lake Sayram,Lake Achit,Lake Uureg,Lake Uvs,Lake Khyargas and Lake Telmen,were selected as the study area,and their dynamics were monitored over the past 30 years.A long time series of year-by-year data sets on lake area,water level and water volume changes were constructed for each lake to analyze their change patterns.In addition,the factors influencing changes in lake dynamics were analyzed in conjunction with meteorological data and information related to human activities.The main research elements and conclusions are as follows:(1)The water levels of 8 typical endorheic lakes in the highland region of the Central Asian were monitored for several years using a combination of in situ data,ICESat-1,Cryo Sat-2 and ICESat-2 satellite altimetry data.Lake Issyk-Kul and Lake Selim in the central part of the Tianshan Mountains have been relatively stable over recent years,with relatively small changes in water levels.Lakes Uvs and Uureg on the Altai Mountains and Mongolian Plateau and adjacent areas showed a slight increase in water levels,while Lakes Achit,Lake Khyargas and Lake Telmen in the same area showed varying degrees of decrease in water levels.(2)Using the JRC dataset,the lake area changes of 8 typical alpine endorheic lakes for the long time series from 1990 to 2021 was extracted on the Google Earth Engine platform,and their change trends were analyzed.In terms of spatial distribution,Lake Karakul,located on the Pamir Plateau,showed an increasing trend in area;Lake Issyk-Kul and Lake Sayram,located in the central Tien Shan region,both shrank in area,but the amount of change in the area of Lake Sayram was greater.Lake Uvs and lake Uureg,located on the Mongolian Plateau and adjacent to the Altai Mountains,both increased slightly in area,while Lake Achit,Lake Khyargas and Lake Telmen,all located in the same region,showed a slight trend of reduction.(3)Based on the changes in water level and area of each lake,the overall changes in water volume of 8 typical alpine endorheic lakes in central Asia were calculated according to empirical formulas.Between 2003 and 2021,the water area,water level and water volume of lakes in the western part of the study area,i.e.the Pamir Plateau and the Western Tien Shan region,showed an increasing trend,while in the eastern part,the area,water level and volume of lakes in the Altai Mountains and the adjacent areas of the Mongolian Plateau,with the exception of lake Uureg,showed a deficit in water volume We further analysed the potential drivers of lake dynamics,showing that most high mountain plateau lakes are mainly influenced by basin climate change and glacial meltwater,while Kyrgyz and Issyk-Kul lakes are also disturbed by human activities in their long-term dynamics.