Tonle Sap is the largest freshwater lake in Southeast Asia. It forms a natural floodplain reservoir that is drained by the Tonle Sap River into the Mekong River near Phnom Penh. Uniquely, when the level of the Mekong River is high the flow of the Tonle Sap River reverses and water is pushed back into the lake, raising its level by up to 10 meters and increasing its area from 2,500-3,000 square kilometers in the dry season to 10,000-16,000 square kilometers in the rainy season. This unique hydrological cycle and the vast areas of seasonally flooded low forest and shrubs that it creates result in a very high biodiversity of fish, reptiles, birds, and mammals. The Tonle Sap ecosystem is the main source of animal protein for much of the population of Cambodia more than 1 million people live on and around the lake. The lake is fringed by many villages that literally “move house” by pulling up the stilts and floating the house to new moorings, when the lake begins to flood. The lake sometimes becomes a little odorous in the dry season.