论文部分内容阅读
Lake area changes in arid regions of northwest China have serious and damaging effects on human society in the 21th century, many famous lakes such as Lop Nor, Manasi Lake, etc.Climate change, characterized by temperature increases and precipitation changes during recent years, has greatly affected water storage in inland lakes of China.However, human activities play more important effects on these lake changes in the past 20 years.Thus, mapping and monitoring lake area changes in response to climate change and human activities is an urgent task for regional social and economic planning with respect to land use and water demand.Chaiwopu lake is located at Urumqi in Xinjiang, and it is an endoric lake.In the past 20 years, it areal extents shrinks dramatically.In order to expose the main cause of the area changes of Chaiwopu Lake, Landsat images are used to map its seasonal and annual area changes from 1990 to present, and the reason of the lake shrinking is also analyzed with meteorological and hydrological data.Chaiwopu lake is relative stable between 1990 and 2003, and the annual fluctuation rates is less than 2%, while it experienced continuous area decreased from 2004 to present, now it has shrunk to 7.6 km2, whose area has decreased more than 60%.Meteorological and hydrological data showed that the precipitation and run-off is increased in Chaiwopu basin, and some similar lake in Tienshan Mountain are experiencing area expansion changes.Therefore, climate change is not a main factor of lake area changes.Chaiwopu basin is the main water source areas of Urumqi, and more than 30% urban water use comes from the pumping groundwater of Chaiwopu.From 2004, the Urumqi Water Supply Company pumped 30 million m3 water, while in 2011, more than 100 million m3 water is pumped, and the annual increasing rate is more than 30%.As the groundwater is over pumped, the groundwater level has decreased dramatically.In hence, city development and the increasing urban water use is the main reason of the Chaiwopu lake shrinkage.