湄公河（River Mekong）
The Mekong River (known in Tibet as Dza-chu,China as Lancang Jiang and Thailand as Mae Nam Khong),is a major river in southeastern Asia.It is the longest river in the region.From its source in China's Qinghai Province near the border with Tibet,the Mekong flows generally southeast to the South China Sea,a distance of 4,200 km (2,610 mi).The Mekong crosses Yunnan Province,China,and forms the border between Myanmar (Burma) and Laos and most of the border between Laos and Thailand.It then flows across Cambodia and southern Vietnam into a rich delta before emptying into the South China Sea.In the upper course are steep descents and swift rapids,but the river is navigable south of Louangphrabang in Laos.
The natural resource management issues and priorities differ in each of the countries and the level of development and populations vary significantly.In north-east Thailand,with over 20 million people,the water resources are virtually fully developed and problems are emerging associated with salinisation of arable lands as result of over-clearing of native vegetation and poor irrigation,soil erosion,and declining water quality in the rivers and streams.In Laos,with 5 million people and a much poorer country from a GDP perspective,the water resources are largely undeveloped.Cambodia,with 10 million people,is recovering from decades of war,and in the Mekong delta some 20 million Vietnamese live on some of the most highly productive agricultural land in the world.