The Mekong is a river in Southeast Asia. It is the world's 13th-longest river and the 7th-longest in Asia. Its estimated length is 4,350 km (2,703 mi), and it drains an area of 795,000 km2 (307,000 sq mi), discharging 475 km3 (114 cu mi) of water annually. From the Tibetan Plateau this river runs through China's Yunnan province, Burma (Myanmar), Laos, Thailand, Cambodia and Vietnam.
In 1995, Laos, Thailand, Cambodia and Vietnam established the Mekong River Commission to assist in the management and coordinated use of the Mekong's resources. In 1996 China and Burma (Myanmar) became "dialogue partners" of the MRC and the six countries now work together within a cooperative framework.
The extreme seasonal variations in flow and the presence of rapids and waterfalls in this river have made navigation difficult. The river is a major trading route linking China’s southwestern province of Yunnan to Laos, Burma (Myanmar) and Thailand to the south, an important trade route between western China and Southeast Asia.
The Mekong rises in the "Three Rivers Area" on the Tibetan Plateau in the Sanjiangyuan National Nature Reserve as the Lancang, together with the Yangtze and Yellow (Huang He) Rivers. It flows southwest through Yunnan Province, and through the Three Parallel Rivers Area in the Hengduan Mountains, along with the Salween River (Nujiang in Chinese) and the Yangtze.
After leaving China, it flows southwest and forms the border of Burma (Myanmar) and Laos for about 100 kilometres (62 mi) then turns southeast to briefly form the border of Laos with Thailand. The Mekong then flows east and south into Laos for some 400 kilometres (250 mi) and defines the Laos-Thailand border again for some 850 kilometres (530 mi) as it flows first east, passing in front of the capital of Laos, Vientiane, then turns south through central Southeast Asia. The river leaves the border and flows into Laos shortly before passing the city of Pakse. Thereafter, it runs more or less directly south, crossing into Cambodia.
At Phnom Penh the river is joined on the right bank by the river and lake system the Tonle Sap. When the Mekong is low, the Tonle Sap is a tributary; water flows from the lake and river into the Mekong. When the Mekong floods, the flow reverses; the floodwaters of the Mekong flow up the Tonle Sap. Immediately after the Sap River joins the Mekong by Phnom Penh, the Bassac River branches off the right (south) bank. The Bassac River is the first and main distributary of the Mekong; thus, this is the beginning of the Mekong Delta. The two rivers, the Bassac to the south and the Mekong to the north, enter Vietnam very soon after this.
In Vietnam, the Bassac is called the Hậu River (Sông Hậu or Hậu Giang); the main, northern, branch of the Mekong is called the Sông Tiền or Tiền Giang. In Vietnam, distributaries of the northern branch include the sông (river) Mỹ Tho, the sông Ba Lai, the sông Hàm Luông, and the sông Cổ Chiên.
The Mekong Basin can be divided into two parts: the 'Upper Mekong Basin' in Tibet and China, and the 'Lower Mekong Basin' from Yunnan downstream from China to the South China Sea. From the point where it rises to its mouth, the most precipitous drop in the Mekong occurs in Upper Mekong Basin, a stretch of some 2,200 km (1,400 mi). Here, it drops 4,500 metres (14,800 ft) before it enters the Lower Basin where the borders of Thailand, Laos, China and Burma (Myanmar) come together in the Golden Triangle. Downstream from the Golden Triangle, the river flows for a further 2,600 km (1,600 mi) through Laos, Thailand and Cambodia before entering the South China Sea via a complex delta system in Viet Nam.
The Mekong basin is one of the richest areas of biodiversity in the world. Only the Amazon boasts a higher level of biodiversity. Biota estimates for the Greater Mekong Subregion (GMS) include 20,000 plant species, 430 mammals, 1,200 birds, 800 reptiles and amphibians and an estimated 850 fish species. In 2009, 145 new species were described from the Mekong Region, comprising 29 fish species previously unknown to science, two new bird species, ten reptiles, five mammals, 96 plants and six new amphibians. The Mekong Region contains 16 WWF Global 200 ecoregions, the greatest concentration of ecoregions in mainland Asia.
Aquatic biodiversity in the Mekong river system is the second highest in the world after the Amazon. The Mekong boasts the most concentrated biodiversity per hectare of any river. The commercially valuable fish species in the Mekong are generally divided between ‘black fish’, which inhabit low oxygen, slow moving, shallow waters, and ‘white fish’, which inhabit well oxygenated, fast moving, deeper waters. People living within the Mekong river system generate many other sources of food and income from what are often termed ‘other aquatic animals’ (OAAs) such as freshwater crabs, shrimp, snakes, turtles, and frogs.
The internal drainage patterns of the Mekong are unusual when compared to those of other large rivers. Most large river systems that drain the interiors of continents, such as the Amazon, Congo, and Mississippi, have relatively simple dendritic tributary networks that resemble a branching tree. Typically, such patterns develop in basins with gentle slopes where the underlying geological structure is fairly homogenous and stable, exerting little or no control on river morphology.
In marked contrast, the tributary networks of the Salween, Yangtze, and particularly the Mekong, are complex with different sub-basins often exhibiting different, and distinct, drainage patterns. These complex drainage systems have developed in a setting where the underlying geological structure is heterogeneous and active, and is the major factor controlling the course of rivers and the landscapes they carve out.
- The headwaters of the Mekong in Zadoi County, Qinghai, China, are protected in Sanjiangyuan National Nature Reserve. The name Sanjiangyuan means "the Sources of the Three Rivers"; the reserve also includes the headwaters of the Yellow River and the Yangtze.
- The section of the river flowing through deep gorges in Yunnan province is part of the Three Parallel Rivers of Yunnan Protected Areas; a UNESCO World Heritage Site.
- The Tonle Sap Biosphere Reserve in Cambodia contains the largest lake in Southeast Asia. It is a UNESCO Biosphere reserve.
4,350 km (2,703 mi)
795,000 km2 (307,000 sq mi)