Cambodia’s most important river is the Mekong, the longest river in Southeast Asia and the tenth largest in the world. The Mekong flows from north to south through Cambodia and is navigable for much of its course. Other rivers in the country include the Tonle Srepok and the Tonle Sab. Cambodia’s principal lake, the Tônlé Sap (Great Lake), is the largest in Southeast Asia. From the northwest, the Tonle Sap drains into the Mekong via the Tonle Sab River, entering the Mekong at Phnom Penh. Each year during the monsoon season (approximately May to October), the waters of the Mekong increase and reverse the flow of the Tonle Sab, which begins to drain into the lake. The lake then expands dramatically, flooding the provinces along its banks. When dry weather returns, the river reverses its course again and flows back into the Mekong, draining the northwestern provinces. At the height of the flooding, the Tonle Sap reaches more than 10,000 sq km (4,000 sq mi), or about four times its size in the dry season. The lake is one of the richest sources of freshwater fish in the world

   Forests cover 53 percent of Cambodia’s land. The densest forests thrive in the mountains and along the southwestern coast. Higher plains and plateaus contain savannas covered with high, sharp grass. Plants growing in Cambodia include rubber, kapok (a tree with seeds that yield a cotton-like fiber), palm, coconut, and banana, all of which are exploited commercially.Wildlife in Cambodia includes elephants, deer, wild ox, panthers, bears, and tigers. Cormorants, cranes, parrots, pheasants, and wild ducks are also found, and poisonous snakes are numerous. Logging and mining activities, along with unregulated hunting, have diminished the country’s wildlife rapidly.