Which lake is the largest freshwater lake in Southeast Asia?

Tonle Sap is the largest freshwater lake in Southeast Asia. Located in northwestern Cambodia, it belongs to the Mekong river system and is famous for changing dramatically with the region's monsoon cycle.

During the dry season, the lake can shrink to roughly 2,500–2,700 square kilometres and become only about a metre deep. In the rainy season, its area can expand to around 16,000 square kilometres, while the water level rises by as much as 10 metres. This seasonal expansion floods surrounding forests and fields, creating exceptionally productive fish habitat.

The Tonle Sap River reverses direction: rising Mekong waters push into the lake during the wet season, then the lake drains back toward the Mekong. UNESCO designated the lake and surrounding ecosystem a Biosphere Reserve in 1997. Lake Toba is a common distractor because it is Southeast Asia's great volcanic lake, but Tonle Sap is the regional freshwater-area leader.