Tonlé Sap
Tonlé Sap ( , literally 'large river' ("tonlé"); 'fresh, not salty' ("sap"), commonly translated as 'great lake') is a seasonally inundated freshwater lake, Tonlé Sap Lake, and an attached river, the long Tonlé Sap River, that connects the lake to the Mekong River. They form the central part of a complex hydrological system, in the Cambodian floodplain covered with a mosaic of natural and agricultural habitats that the Mekong replenishes with water and sediments annually. The central plain formation is the result of millions of years of Mekong alluvial deposition and discharge. From a geological perspective, the Tonlé Sap Lake and Tonlé Sap River are a current freeze-frame representation of the slowly but continuously shifting lower Mekong basin. Annual fluctuation of the Mekong's water volume, supplemented by the Asian monsoon regime, causes a unique flow reversal of the Tonlé Sap River. The largest freshwater lake in Southeast Asia, it contains an exceptional large variety of interconnected eco-regions with a high degree of biodiversity and is therefore a biodiversity hotspot. It was designated a UNESCO biosphere reserve in 1997.