ABRUPT CHANGE OF LAKE ENVIRONMENT IN WEST CHINA: AN EVIDENCE FOR GLOBAL CLIMATE WARMING

Expanding or shrinking of lakes, especially in the closed basin, directly reflects the balance situation of water\|heat regime in the catchment. Fluctuations of the water\|level can be used as an indicator of climatic and environmental changes. Authors have investigated many lakes in West China in recent years, including lakes in the Tibet Plateau and in the arid area in the northwest China. We found that all lakes have been in shrinkage, some of them were changed into swamp and some dried dramatically up, which caused the abrupt change of the lake environment. This change led the grassland to be retrogression and desertification, and made the eco\|environment deterioration in West China.The Xingcuo Lake, in the height of 3425m ASL with 29km\+2 drainage area, located in the Zoige Basin, Northeastern Tibet Plateau, had changed into swamp in the area of 2km\+2 , and the vast area of peripheral marsh changed into grassland by the years of 1990. But the topographic map in the scale of 1/100000 and aerial photography surveyed at the end of 1960’s show clearly that this lake was in the area of 3 3km\+2 and surrounded by vast area of marshland. In the north central part of the Tibet Plateau, the Gourencuo Lake, in the height of 4650m ASL, was in the area of 23 5km\+2 with the average water depth of 1 3m in 1990. Then a dramatic change had been appearing in the recent years. When authors went there again in 1998,they found that the lake dried fully up. A thin salt crystal layer with saturated brine covered the flat central lake floor. This means that at least 30×10 6 m 3 water volume stored in the lake had been lost by the evaporation in 8 years, and many sand dunes had been formed. This abrupt change of lake environment could be recognized as the result of natural process or climate warming because of no human activity there.