Several typical large lake regions were selected for this study including the Five Central Asia Country Lakes Region, Middle-Low-Reaches of Yangtze River Lakes Region, Qinghai-Tibet Plateau Lakes Region, and North America Great Lakes Region. MODIS synthesis data (every 8 days) were used to measure the spatial and temporal variations of surface water areas. For illustration purpose, Five Central Asia Country Lakes Region and Poyang Lake (Middle-Low-Reach of Yangtze River Lakes Region) are presented below.
Aral Sea, located in Central Asia, is an inland salt water lake with water supply mainly relied on Amu Darya and Syr Darya. Aral Sea was in a shrinking trend during 2001 to 2012 (Figure 4-1). The lake was relatively stable from 2001 to 2005, but declined gradually from 2006 to 2009 in the east part of Aral Sea, was recovered in 2010 and 2011. In 2012, however, the water area of Aral Sea dropped to the historical lowest point into 18766.5 km² (maximum in the year) which was a 39.10% decline comparing to the maximum surface water area of 2001.Water area shrinking in south Aral Sea contributed to most of the decline. In particular, the east part of south Aral Sea showed the most significant shrink with about 1/3 of surface water area reduction of the whole Aral Sea.
Poyang Lake, located in north part of Jiangxi Province, border on south bank of the Yangtze River, is the largest fresh water lake in China. Wet season of the Poyang Lake is from June to August every year. Winter is its dry season. From 2001 to 2012, the annual maximum surface water areas of Poyang Lake were all above 3000 km². During this period, surface water area reached the peak in 2002 at 3873.90 km². Annual minimum surface water areas in this period were all below 1400 km² with a decline tread. Minimum surface water area reached the lowest in 2011 at 721km².
Another large fresh water lake in China, Dongting Lake, maintained the maximum surface water areas above 1600 km² every year during this period. The year 2001 reached the highest of 2600.30 km²，and the lowest occurred in 2004 at 1641.40 km². The annual minimum surface water areas were all below 600 km² from 2001 to 2012. There also showed a volatility shrinking trend with the lowest in 2007 at 253km² (Figure 4-2).