The plains of the Mekong and Tonle Sap basin are confined in the North by the Dangrek and Central Annamite Mountains, and to the South by the Cardamom Mountains and Elephant Mountains. The plains completely surround the Tonle Sap Lake in the western half of the country and wind their way through the middle of the country following the course of the Mekong River. The two basins actually form a single body of water, the whole of which effects about 75% of Cambodia's land cover.