The Mekong is the longest river in southeast Asia. From its source on the Tibetan plateau it runs for 4,800 km through China, Myanmar, Lao PDR, Thailand, Cambodia and Viet Nam to the South China Sea, where it discharges on average 475,000 million m3 per year. The total Mekong Basin (MB) catchment area covers 795,000 km2 and has 73 million inhabitants. The Lower Mekong Basin (LMB) comprises the four countries, - Cambodia, Lao PDR, Thailand and Viet Nam - that signed the 1995 river development agreement and covers 77% of the total basin with 55 million people. The degree of inundation of the 70,000 km2 floodplains depends on the strength of the monsoon, as 85-90 % of the discharge is generated during the wet season from May to October. Although far from pristine, the river still is in a relative good condition. Only 2 mainstream dams (in China) have been built, but many more on the tributaries. The number of fish species that has been found in the MB exceeds 2000. Many migrate across international borders, thus constituting trans-boundary resources.