MEKONG RIVER

The Irrawaddy and Mekong river basins and their drainage networks. Cambodian Mkngk, Chinese (Wade-Giles) Lan-ts'ang Chiang, or (Pinyin) Lancang Jiang, Laotian Mnam Khong, Thai Mae Nam Khong, Vietnamese Sng Tin Giang, longest river in Southeast Asia, the 7th longest in Asia, and the 12th longest in the world. It has a length of 2,700 miles (4,350 kilometres). Rising in Tsinghai province, China, it flows through the eastern part of the Tibet Autonomous Region and Yunnan province, after which it forms part of the international border between Myanmar (Burma) and Laos, as well as between Laos and Thailand, also flowing through Laos, Cambodia (Kampuchea), and Vietnam before draining into the South China Sea to the south of Ho Chi Minh City (Saigon). Vientiane, capital of Laos, and Phnom Penh, capital of Cambodia, both stand on its banks. About three-fourths of the drainage area of the Mekong lies within the four countries traversed by its lower basinLaos, Thailand, Cambodia, and Vietnam. Cambodian Mkngk, Wade-Giles romanization Lan-ts'ang Chiang, Pinyin Lancang Jiang, Laotian Mnam Khong, Thai Mae Nam Khong, Vietnamese Sng Tin Giang longest river in Southeast Asia, having a length of approximately 2,700 miles (4,350 km). The Mekong River drains more than 313,000 square miles (810,600 square km) of land. The headwaters, known as the Ang-ch' and the Cha-ch', rise at elevations of more than 16,000 feet (4,900 m) in the T'ang-ku-la Mountains on the southern border of Tsinghai province in China. The upper Mekong, comprising roughly one-fourth of the total length, descends in a southerly direction across the highlands of Yunnan province in a long, narrow, deeply cut valley. It then forms part of the international border between Myanmar (Burma) and Laos, as well as between Laos and Thailand, and flows successively through Laos, Cambodia, and Vietnam before entering the South China Sea in a wide delta south of Ho Chi Minh City (formerly Saigon) in Vietnam. South of the Myanmar-Laos border, the lower Mekong basin receives the drainage of the Khorat Plateau of Thailand, from most of Cambodia, and from the western slopes of the Annamese Cordillera (Chane Annamitique) in Laos and Vietnam, before the river divides into two streamsthe Mekong and the Bassacin its delta section. South of Yunnan, most of these drainage areas have similar landforms, soils, and tropical broadleaf vegetation. Vientiane, the capital of Laos, and Phnom Penh, the capital of Cambodia, stand on the banks of the Mekong. The mean annual discharge of the river at Krchh in central Cambodia is about 500,000 cubic feet (14,000 cubic m) per second. Flow comes chiefly from rainfall in the lower basin and reflects the variation in seasonal rainfall caused by monsoon winds. When the wet southwesterly monsoon winds blow from July to October, the highest water levels are reached, coming as early as August or September in the upper reaches of the Mekong and as late as October in the southern reaches. The lowest levels occur during the dry weather caused by the northeasterly monsoon winds from November to May. The lower Mekong River basin is home to about one-third of the combined population of Cambodia, Laos, Thailand, and Vietnam. About nine-tenths of these people are engaged in agriculture and produce rice, the chief crop of the basin. Rice cultivation, however, is impossible during the long dry period without irrigation. In 1957 the Mekong River Development Project was initiated by the United Nations. The project called for cooperation between Laos, Thailand, Cambodia, and South Vietnam in building facilities for the generation of hydroelectric power and for improvements in irrigation, flood control, drainage, and navigation. Additional reading United Nations, Atlas of Physical, Economic, and Social Resources of the Lower Mekong Basin (1968), includes maps of resources and a descriptive text. C. Hart Schaaf and Russell H. Fifield, The Lower Mekong: Challenge to Cooperation in Southeast Asia (1963); W.R. Derrick Sewell and Gilbert F. White, The Lower Mekong: An Experiment in International River Development (1966); and Gilbert F. White et al., Economic and Social Aspects of Lower Mekong Development (1962), are reviews of early planning for the lower basin. A later comprehensive plan for the lower basin is surveyed in Interim Committee for Coordination of Investigations of Lower Mekong Basin, Perspectives for Mekong Development (1988). Committee for Coordination of Investigations of the Lower Mekong Basin, Mekong Work Programme 1993: Ongoing and Proposed Projects (1992), outlines basinwide programs for the planning and development of water and related resources (e.g., agriculture, fisheries, and transport). Gilbert F. White Jeffrey W. Jacobs