Composite Image: Cambodia

The Tonle Sap Lake of Cambodia is one of the largest lakes in Asia, and it is unique in that the direction of flow of the river that feeds it changes by season. In June and November, the Tonle Sap River changes course. In June, with monsoon rains swelling the Mekong River, excess water is pushed into the Tonle Sap, which then drains back upstream into the lake, flooding the surrounding low plains. By monsoon's end in November, the pressure is relieved and the Tonle Sap reverses course and returns to the normal direction of flow.