Tonlé Sap is a lake in the northwest of Cambodia. Belonging to the Mekong River system, Tonlé Sap is the largest freshwater lake in Southeast Asia and one of the most diverse and productive ecosystems in the world. It was designated as a Biosphere Reserve by UNESCO in 1997 due to its high biodiversity. During the 21st century, the lake and its s…Tonlé Sap is a lake in the northwest of Cambodia. Belonging to the Mekong River system, Tonlé Sap is the largest freshwater lake in Southeast Asia and one of the most diverse and productive ecosystems in the world. It was designated as a Biosphere Reserve by UNESCO in 1997 due to its high biodiversity. During the 21st century, the lake and its surrounding ecosystems have come under increasing pressure from deforestation, infrastructure development and climate change.