The Mekong is a trans-boundary river in Southeast Asia. It is the world’s twelfth longest river and the seventh 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 the river runs through China’s Yunnan Province, Myanmar, Laos, Thailand, Cambodia, and Vietnam. In 1995, Laos, Thailand, Cambodia, and Vietnam established the Mekong River Commission (MRC) to manage and coordinate use of the Mekong’s resources. In 1996 China and Myanmar became “dialogue partners” of the MRC and the six countries now work together in a cooperative framework.
The extreme seasonal variations in flow and the presence of rapids and waterfalls in the Mekong make navigation difficult. Even so, the river is a major trade route between western China and Southeast Asia.
The English name “Mekong” derives from a contracted form of Thai and Lao Mae Nam Khong. In Thai and Lao, mae nam (‘mother of water[s]’) is used for any major river and Khong is the proper name. As such, Thai and Lao locals often refer to it in English as the “River Khong”. Khong itself, however, is an archaic word meaning ‘river’ or ‘the river’, cognate with Chinese 江 whose Old Chinese pronunciation has been reconstructed as /*kˤroŋ/ and which long served as the proper name of the Yangtze before becoming a generic word for major rivers. In Khmer, Mékôngk is itself glossed as ‘mother of water’, from mé (‘mother’) and taking kôngk as a form of kôngkea (‘water’).
Course
The Mekong rises as the Za Qu and soon becomes known as the Lancang (Lantsang) in the “Three Rivers Source Area” on the Tibetan Plateau in the Sanjiangyuan National Nature Reserve; the reserve protects the headwaters of, from north to south, the Yellow (Huang He), the Yangtze, and the Mekong Rivers.It flows through the Tibetan Autonomous Region and then southeast into Yunnan Province, and then the Three Parallel Rivers Area in the Hengduan Mountains, along with the Yangtze to its east and the Salween River (Nujiang in Chinese) to its west.
The Mekong then meets the tripoint of China, Myanmar and Laos. From there it flows southwest and forms the border of Myanmar and Laos for about 100 kilometres (62 mi) until it arrives at the tripoint of Myanmar, Laos, and Thailand. This is also the point of confluence between the Ruak River (which follows the Thai–Myanmar border) and the Mekong. The area of this tripoint is sometimes termed the Golden Triangle, although the term also refers to the much larger area of those three countries that was notorious as a drug producing region.
From the Golden Triangle tripoint, the Mekong turns southeast to briefly form the border of Laos with Thailand.
Khon Pi Long is a series of rapids along a 1.6-kilometre section of the Mekong River dividing Chiang Rai and Bokeo Province in Laos. The name of the rapids means “where the ghost lost its way”. It then turns east into the interior of Laos, flowing first east and then south for some 400 kilometres (250 mi) before meeting the border with Thailand again. Once more, it defines the Laos-Thailand border for some 850 kilometres (530 mi) as it flows first east, passing the capital of Laos, Vientiane, then turns south. A second time, the river leaves the border and flows east into Laos soon passing the city of Pakse. Thereafter, it turns and 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 Tonlé 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 (west) bank. The Bassac River is the first and main distributary of the Mekong. This is the beginning of the Mekong Delta. The two rivers, the Bassac to the west and the Mekong to the east, enter Vietnam shortly after this. In Vietnam, the Bassac is called the Hậu River (Sông Hậu or Hậu Giang); the main, eastern, branch of the Mekong is called the Tiền River or Tiền Giang. In Vietnam, distributaries of the eastern (main, Mekong) branch include the Mỹ Tho River, the Ba Lai River, the Hàm Luông River, and the Cổ Chiên River.
Natural history
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 freshwater fish species (excluding euryhaline species mainly found in salt or brackish water, as well as introduced species).The most species rich orders among the freshwater fish in the river basin are cypriniforms (377 species) and catfish (92 species).
New species are regularly described from the Mekong. In 2009, 145 new species were described from the region, including 29 fish species previously unknown to science, two new bird species, 10 reptiles, five mammals, 96 plants, and six new amphibians. Between 1997 and 2015, an average of two new species per week were discovered in the region. The Mekong Region contains 16 WWF Global 200 ecoregions, the greatest concentration of ecoregions in mainland Asia.
No other river is home to so many species of very large fish. The biggest include three species of Probarbus barbs, which can grow up to 1.5 m (4.9 ft) and weigh 70 kg (150 lb),the giant freshwater stingray (Himantura polylepis, syn. H. chaophraya), which can reach at least 5 m (16 ft) in length and 1.9 m (6.2 ft) in width, the giant pangasius (Pangasius sanitwongsei), giant barb (Catlocarpio siamensis) and the endemic Mekong giant catfish (Pangasianodon gigas). The last three can grow up to about 3 m (9.8 ft) in length and weigh 300 kg (660 lb). All of these have declined drastically because of dams, flood control, and overfishing.
One species of freshwater dolphin, the Irrawaddy dolphin (Orcaella brevirostris), was once common in the whole of the lower Mekong but is now very rare, with only 85 individuals remaining.
Among other wetland mammals that have been living in and around the river are the smooth-coated otter (Lutra perspicillata) and fishing cat (Prionailurus viverrinus).
The endangered Siamese crocodile (Crocodylus siamensis) occurs in small isolated pockets within the northern Cambodian and Laotian portions of the Mekong River. The saltwater crocodile (Crocodylus porosus) once ranged from the Mekong Delta up the river into Tonle Sap and beyond but is now extinct in the river, along with being extinct in all of Vietnam and possibly even Cambodia.
Fisheries
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.
OAAs account for about 20 percent of the total Mekong catch.When fisheries are discussed, catches are typically divided between the wild capture fishery (i.e., fish and other aquatic animals caught in their natural habitat), and aquaculture (fish reared under controlled conditions). Wild capture fisheries play the most important role in supporting livelihoods. Wild capture fisheries are largely open access fisheries, which poor rural people can access for food and income.
Broadly, there are three types of fish habitats in the Mekong: i) the river, including all the main tributaries, rivers in the major flood zone, and the Tonle Sap, which altogether yield about 30 percent of wild catch landings; ii) rain-fed wetlands outside the river-floodplain zone, including mainly rice paddies in formerly forested areas and usually inundated to about 50 cm, yielding about 66 percent of wild catch landings; and iii) large water bodies outside the flood zone, including canals and reservoirs yielding about four percent of wild catch landings.
The Mekong Basin has one of the world’s largest and most productive inland fisheries.An estimated two million tonnes of fish are landed a year, in addition to almost 500,000 tonnes of other aquatic animals. Aquaculture yields about two million tonnes of fish a year. Hence, the lower Mekong basin yields about 4.5 million tonnes of fish and aquatic products annually. The total economic value of the fishery is between US$3.9 and US$7 billion a year. Wild capture fisheries alone have been valued at US$2 billion a year. This value increases considerably when the multiplier effect is included, but estimates vary widely.
An estimated 2.56 million tonnes of inland fish and other aquatic animals are consumed in the lower Mekong every year. Aquatic resources make up between 47 and 80 percent of animal protein in rural diets for people who live in the Lower Mekong Basin. Fish are the cheapest source of animal protein in the region and any decline in the fishery is likely to significantly impact nutrition, especially among the poor.The size of this impact has not been established.
It is estimated that 40 million rural people, more than two-thirds of the rural population in the lower Mekong basin, are engaged in the wild capture fishery. Fisheries contribute significantly to a diversified livelihood strategy for many people, particularly the poor, who are highly dependent on the river and its resources for their livelihoods. They provide a principal form of income for numerous people and act as a safety net and coping strategy in times of poor agricultural harvests or other difficulties.In Laos alone, 71 percent of rural households (2.9 million people) rely on fisheries for either subsistence or additional cash income. Around the Tonle Sap Lake in Cambodia, more than 1.2 million people live in fishing communes and depend almost entirely on fishing for their livelihoods.
