3.1 Current Spatial Distribution of Large Terrestrial Surface Water Areas in China
The maximum area of large terrestrial surface water areas in China in 2012 was 67,100 km², 0.70% of the total land area of China. The minimum area of large terrestrial surface water areas in China in the same year was 56,400 km², 0.59% of total land area of the country (Figure 3-1). There is an increasing trend of large terrestrial surface water areas in China from 2001 to 2012.
While the spatial distribution pattern of large terrestrial surface water areas in China was quite wide, it concentrated in several regions or provinces. Based on provinces (provincial level cities and regions), the area of large terrestrial surface water areas was calculated. The top three provinces (or regions) with the highest number of large terrestrial surface water areas were (in order): Tibet Autonomous Region, Qinghai Province, and then Hubei Province. The total number of large lakes and reservoirs in the three provinces (regions) were 186, 59 and 33 respectively, occupying 36.4%, 11.5% and 6.5% of the nation’s total number of large lakes and reservoirs. The three top provinces (regions) with the highest areas of large terrestrial surface water areas were (in order): Tibet Autonomous Region, Qinghai Province, and Xinjiang Uygur Autonomous Region. Total Areas of large terrestrial surface water areas in the three provinces (regions) were 22,806 km²，11,434 km² and 5,482 km²,respectively，representing 33.3%, 16.7%, and 8.0% of the total area of the nation’s large terrestrial surface water areas.

3.2 Spatial and Temporal Variation of Large Terrestrial surface water areas in China
China’s large terrestrial surface water areas were mainly located in China’s five large lakes regions, respectively Tibet Plateau, Mongolia- Xinjiang (Mon-Xin) Plateau, East Plain, Northeast Plain and Yunnan-Guizhou (Yun-Gui) Plateau(Figure 3-1).
Lakes in Qinghai-Tibet Plateau located in the hinterland of the plateau, mostly are inland ones. Lake frozen period in winter is relatively long, rainfall, snow melting and glacial water are main sources of water supply. Wet seasons normally occur from the end of April to the beginning of May when snow melting water provides larger amount of supply to lakes. Surface water area in Qinghai-Tibet Plateau declines slightly during June to July summer season. Generally speaking, Qinghai-Tibet Plateau lakes have a longer water coverage time with small variations (Figure 3-2).

East Plain Lake Districts located in the area covering Beijing, Jiangsu, Zhejiang, Hebei, Henan, Shandong, Hunan, Jiangxi, Anhui, Hubei, Shanghai, Fujian, Guangxi, Hong Kong, Macau, and Taiwan, etc. Along middle and low reaches of Yangtze River and Huaihe River, low reaches of Yellow and Haihe River, and the Grand Cannel. East Plain Lakes are close to the sea with a warm and wet climate. Lakes get large amount of water supply by rainfall. Wet seasons occur from July to August when precipitation is high. In 2012, the difference of maximum and minimum surface water areas of East Plain Region, the richest one of large terrestrial surface water areas in China, indicated the higher variations of surface water area in the region (Figure 3-3).

Mon-Xin (Mongolia-Xinjiang) Region covers Inner Mongolia, Xinjiang, Shanxi, Shaanxi, Ningxia, Gansu provinces and autonomous regions. With arid and semi-arid inland region, this region suffers from water supply shortage. While precipitation in the region is little, leading to small surface run-off, lake evaporation is high exceeding lake water supply. It is clear that climate variation, particularly precipitation and temperature conditions determine the surface water area change in this region. In addition, in arid and semi-arid northwest region, many hydraulic engineering works were built to retain water, causing lake water supply declined and even totally interrupted. As a result, surface water area of this region has shrinked significantly. In general, surface water area of this region increases slowly from April to June, and then increases relatively faster in the rain season of July and August. It shows some volatility increase from September to October (Figure 3-4).

The Northeast Lake Region, covers Heilongjiang, Jilin, Liaoning provinces, is surrounded by mountains in three sides. In the middle of the district are Songnen Plain and Sanjiang Plain where lakes are concentrated in plains with high river density. Surface water area of Northeast District Lakes is relatively smaller during April and May. The area increases rapidly since July rain season then becomes stable in October frozen season (Figure 3-5).

The Yunnan-Guizhou (Yun-Gui) Plateau Lakes Regions, including Sichuan, Chongqing, Yunnan and Guizhou provinces, has all out-flow flesh water lakes. Larger lakes in this region, located along geological fault lines or ridge lines of large watersheds, are mostly tectonic lakes with deep water body. Comparing with other Lakes Regions, the changes of large terrestrial surface water areas were little. Water supply for lakes in the region is mainly from southwestern monsoon precipitation. Rainfall from May to October accounted for more than 80% of the total annual rainfall. Lake water level changes with seasonal rainfall variation. In 2012, the minimum surface water area occurred in August, which was unusual comparing with previous records. This could be attributed to droughts and higher water consumption in 2012(Figure 3-6).