Dynamic Changes Of Lakes In The Tibetan Plateau And Inner Mongolia-Xinjiang Lake Area And Their Response To Climate Fluctuation In The Past Forty Years

The authors extracted surface extent of all lakes in the study area from Landsat remote sensing images of the 1970's,the 1990's,around 2000 and 2010 based on RS and GIS and developed the lake spatial database in combination with on-the-spot investigations to a few representative lakes.The results show that the total surface area of lakes increased by 10.86%during the period the 1970's to the 1990's,increased by 5.53%during the period the 1990's to around 2000,and increased by 8.73%from 2000 to around 2010.It showed that lakes in the study area keep the expanding trend in the past forty years.But the situation varies throughout the study area.Additionally,lakes each of which has an area larger than 10 km2 on the Tibetan Plateau and has an area larger than larger than 5 km2 in Inner Mongolia and Xinjiang suitable for the surface area changes analysis were selected to compare the dynamic changes one by one,and division of these lakes into expansion area and atrophy area was made according to dynamic changes.Lake variations differ from area to area in different periods.In practical terms,between the 1970's and the 1990's,lakes in north and middle Tibet,southern Tibet,Qinghai Qiangtang Basin,east Qinghai,northwest Xinjiang and southeast Inner Mongolia shrunk whereas lakes in other places tended to expand.From the 1990's to 2000,lakes in north Qinghai and southeast Inner Mongolia shrunk.From 2000 to 2010,most lakes in the study area expect southern Tibet and east Inner Mongolia expanded.We found that the climate of the Tibetan Plateau and Inner Mongolia-Xinjiang lake area changed from warm dry to warm wet gradually characterized by increasing temperate,precipitation,and dropping evaporation through the meteorological data.In practical terms,the temperature of the study area increased significantly in the past forty years.Especially after 2000,the temperate of the Tibetan Plateau rose much faster.The precipitation showed a trend of increasing on the whole except Inner Mongolia whose precipitation dropped since 2000.The evaporation of the Tibetan Plateau,Xinjiang,Gansu and Ningxia dropped,whereas the evaporation of Inner Mongolia fluctuated in different periods.The response of lake variations to climate fluctuation is strong,but different climate parameters can produce different effects in different areas.?Temperature mainly affects lakes that rely on glacier melt water runoff for supply,such as Siling Lake and Chibuzhang Lake.?precipitation mainly influences lakes recharged by precipitation,such as Qinghai Qiangtang Basin and surface runoff.?Evaporation brings about water loss of all lakes,which influences areas with evaporation effect caused by raising temperature surpass the increasing precipitation and runoff,such as Yamdrok Lake.However,the area variations of lakes in Inner Mongolia affected by both climate and human activities.Irrigation and coal mining are two main factors responsible for the withering of many lakes.Under the influence of warm-wet climate,many salt lakes on the Tibetan Plateau expanded,and the influence of lake desalination and mineral resoures impoverishment on mineral resources exploitation was analyzed:?it has caused higher cost and more difficulties,even some salt lakes at the critical-grade level for industrial development will lose their exploitation value;?under the condition of salt lake desalination,effective extraction technologies of mineral resources such as lithium require development urgently;?such a situation may have some impact on the government's policy-decision for mineral resources development,and the establishment of the pre-warning and monitoring system of salt lakes in Qinghai is necessary.In a word,tectonic activities play an important role in the evolvement of lakes in long time scales,controlling the large pattern and climate shapes lakes more directly in short time scales,such as decades.Moreover,some other factor such as tectonics,glaciers,human activities,lake basin shape,open or closed systems,and catchments can exert a measure of influence over the lakes.