The brown-watered Mekong is one of the great rivers, and one of the longest, of Southeast Asia. From its glacial sources in the lofty Tibetan Highlands, the Mekong flows for 2,600 miles (4,200 kilometers) through China, Laos, Thailand, Cambodia, and Vietnam, finally emptying into the South China Sea south of Ho Chi Minh City.
Hurtling down the mountainous plateaus of Yunnan Province, the river creates steep-walled gorges between the Yangtze and Salween rivers. The Yangtze and Salween, as well as the Huang He, also have their origins in the mountains of Tibet. The Mekong becomes more placid and broad as it continues through the Indochinese peninsula. Flowing toward the sea, the river forms the boundary between Laos and Myanmar and part of the boundary between Laos and Thailand.
It then continues southward through Cambodia, where it passes over the giant Khone Falls. One of the world’s most powerful cataracts, this series of rapids and falls drops a total of 70 feet (21 meters). Noted for its tremendous volume, the Khone Falls has a mean annual flow of 410,000 cubic feet (11,600 cubic meters) per second. The river is 8 miles (13 kilometers) wide along this stretch.
At Phnom Penh, Cambodia, the river is linked with Tonle Sap, or Great Lake, a huge natural reservoir. During the dry season, which lasts from October to May, the lake covers about 1,000 square miles (2,600 square kilometers). It may cover up to 10,000 square miles (26,000 square kilometers) in the flood season between June and October when the Mekong’s swollen waters back up into the lake (see Cambodia). During flood season the river’s depth can increase from 5 feet (1.5 meters) to nearly 45 feet (14 meters). The wide delta created by the Mekong in southern Vietnam receives the rich alluvial soil that has helped the area to become one of the world’s great producers of rice. The river is navigable to Luoangphrabang (Luang Prabang), Laos.