Lake area variations in the Altun Mountain National Nature Reserve 1970-2021

Lakes in the Qinghai-Xizang Plateau are very sensitive to climate changes and play an important role in regional water cycle and ecological environment balance． Area variations of 10 lakes greater than 1 km² in the Altun Mountain National Nature Reserve from 1970 to 2021 were investigated． Lake areas were extracted from large-scale topographic maps and remote sensing images of QuickBird and Landsat．The relationships of lake area and annual air temperature, precipitation and evaporation of four meteorological stations around the reserve were analyzed． The lakes in the reserve have shown three trends: expansion, stability, and shrinkage in the past 51 years, but most expanded． Large lakes are showing a trend of expansion, with the mid-1990s as the node． In the early stage, expansion was slow, but in later stages, significant rate of expansion was found． Variations in the area of medium-sized lakes show three trends: expansion, stability, and shrinkage． Two trends prevail for small lakes expansion and contraction． The trend of variations in lake area is not related to the size of the lake, but to balance of supply and expenditure． Shazi Lake and Xiaoshazi Lake have some river sections buried under sand． The lake area has changed relatively little over the years, indicating no large-scale movement of sand dunes towards the lake． The area of lakes in the reserve is positively correlated with temperature and precipitation, and significantly negatively correlated with evaporation． The lakes within the reserve are replenished by both rainfall and glacier meltwater, but the amount of glacier meltwater replenishment is greater than precipitation． The impact of temperature and precipitation on the area of expanding lakes is greater than evaporation． These results are helpful to understand the evolution of water resources controlled by climate change in the region, and can be used for further assessment of regional climate change and lake change．