Study On China's Major Lakes Changes By Using GLAS And Optical Remote Sensing Images

Dynamic changes in lakes play an important role in regional water cycle and climate change.Remote sensing satellite is capable of supporting lake monitoring with the advantage of large-area and accurate observation.However,traditional optical data can only acquire the area information of lakes,and it doesn't work well in monitoring water-level changes.Instead,Ice,Cloud,and land Elevation Satellite/Geoscience Laser Altimeter System(ICESat-1/GLAS),a space-borne LiDAR sensor,was widely used as an effective tool for water-level measurement in global scale.Even so,GLAS data still can hardly provide any relevant information about lakes border,which greatly limits its application in monitoring the changes of lakes water reserves.Given that the information provided by two different data sources is complementary,the fusion of GLAS data and remote sensing optical images will be an available way of monitoring water reserve change.In this study 62 lakes located in China first selected as research objects,and the area of each lake is larger than 100 km2.These selected lakes belong to four different lake regions,the Qinghai-Tibet Plateau lakes,the Inner Mongolia-Xinjiang Plateau lakes,the Eastern plains lakes and the Yunnan-Guizhou Plateau lakes.However,due to the limitation of data quality and coverage,only 10 typical lakes were used for further study.They are Nam Co,Selin Co,Yamzhuo Yumco,Qinghai Lake,Bosten Lake,Hulun Lake,Dongting Lake,Poyang Lake,Dianchi Lake and Fuxian Lake,respectively.This paper aims at monitoring the dynamic changes of lakes water reserves.Our specific objective is to monitor the changes of lake water reserves combining GLAS data and other remote sensing data,and further to analyze the driving factors of lake water reserves changes.The main conclusions are as follows:1)In the Qinghai-Tibet Plateau,the water levels of both Nam Co and Selin Co increase,while the water levels of Yamzho Yumco Lake and Qinghai Lake decrease from the year 2003 to 2009.Among all lakes,Selin Co showed a fastest rise in water elevation(0.42 m/a),area(32.59 km2/a)and volume(1.2 km3/a),this is related to the increase in glacier melting water;2)Both Bosten and Hulun Lake in the Inner Mongolia-Xinjiang Plateau had a decrease in water level and area.Specifically,the water level of Bosten Lake showed a more rapid decline which is up to-0.41 m/a,the area of Hulun Lake showed a larger shrink,which is up to-35.57 km2/a,this is related to the warm and dry temperature;3)The water level and area of Dongting Lake and Poyang Lake in the Eastern plains showed obvious seasonal variation.The volume of each lake is quite different in February,May and October each year.The volume changes of the two lakes range from-1.2~2.8 km3,-3.29~3.06 km3,respectively;4)Due to the effects of precipitation and human factors,the Fuxian Lake had a rise in both area and water level with 0.31 km2/a and 0.19 m/a,respectively.In contrast,the area and water level of Dianchi Lake showed a decrease with 1.91 km2/a and 0.04 m/a,respectively;5)Precipitation,temperature and evapotranspiration are the three primary factors leading to lake changes.Nam Co and Selin Co are mainly supplied by glacier melt water.Yamzho Yumco,Qinghai Lake,and Bosten,Hulun Lake belong to the lakes which are greatly affected by precipitation.Due to temperature warming and drying,evaporation is greater than precipitation,which leads to a decrease in water storage.The changes of Dongting Lake and Poyang Lake show a significant seasonal difference.Fuxian Lake and Dianchi Lake are mainly affected by human factors such as dam engineering.