Monitoring Glacial Lake Variations Based on Remote Sensing in the Lhozhag District,Eastern Himalayas,1980-2007

Based on the datasets of topographic maps of 1980,Landsat TM of 1988/1990,Landsat ETM+of 2000,and ALOS AVNIR-2 of 2007 as well as 42 years(1967-2008) temperature and precipitation data in the Lhozhag District of the eastern Himalayas,the characteristics of glacial lake change and its reason were investigated.The results show that: 1) The total area of 53 glacial lakes(with an area larger than 0.02 km2 in 1980) increased from 9.97 km2 in 1980 to 13.05 km2 in 2007.The overall increase was 3.08 km2,which was 30.9% of the total glacial lake area in 1980.Compared with the non-glacial-fed lakes,the area of glacial lakes in 1980 was found larger than the latter,and was distributed in more grades and elevation gradients.Moreover,area expansion during 1980-2007 of glacial lakes was as large as 102.7 times that of the non-glacial-fed lakes,much larger than the latter.It shows that the distribution and change of glacial lakes were affected deeply by glacier-meltwater supply.2) During the period of 1980-2007,the average annual temperature of Cona Station increased significantly,which was in agreement with the trend of global warming elsewhere.The annual precipitation in Cona Station increased a little during 1980-2007.Therefore,the increase of glacial meltwater caused by rising temperature and increasing precipitation in the study area jointly determined the expansion of glacial lakes.Increased annual temperature acted as the most significant factor for recent glacial lake expansion in the Lhozhag District,while increased precipitation made some contributions,too.3) The risk assessment of outburst probability for 32 recognizable glacial lakes larger than 0.1 km2 in 2007 shows that Cuogalongpu,Jialangka,Angge and Bailang lakes were in the highest rank of outburst in the study area.