Effects of climate change and human activity on lake shrinkage in Gonghe Basin of northeastern Tibetan Plateau during the past 60 years

Changes in the status of freshwater resources are a topic of major global,regional and local concern.This is especially so in the arid and semi-arid regions of China,where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development,as well as in sustaining natural ecosystems.Recent climate change,as well as the effects of localized human activity,such as the use of water for irrigation agriculture,may have significant effects on the status of the water resources in the region.Here,we report the results of a study of changes in the areas of lakes in Gonghe Basin,northeastern Tibetan Plateau of China,over the last 60 years.The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950 s to 1980 s.The cause is ascribed mainly to human activity including exploitation of farmland,against a background of increasing population;in addition,climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly.After the construction of several reservoirs,significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes.However,both the area of farmland and the population size remained approximately constant after 1990.We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors(precipitation and temperature).As the regional temperature reached a new high,the area of some of the lakes decreased sharply before finally maintaining a relatively steady state.We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.