Tonle Sap is the largest fresh water lake in ASEAN. Its dimension changes depending on the monsoon and dry season. During rainy season (June-October), the lake will be filled up by water flowing in from the Mekong River, causing the lake to be as deep as 14 metres and the water surface to expand to around 10,000 square kilometers. During the dry season (November-May) the water surface could shrink down to around 3,000 square kilometers, where the depth could be as low as 2 metres, as water from the lake flows back into the Mekong River. The surrounding forest near the lake is home to over 300 species of fishes, widlife, and reptiles. More than 100 species of birds also call this area their habitat.