From SW Laos the river descends onto the Cambodian plain, where it receives water from Tônlé Sap during the dry season by way of the Tônlé Sap River; during the rainy season, however, the floodwaters of the Mekong reverse the direction of the Tônlé Sap River and flow into Tônlé Sap, a lake that is a natural reservoir. The Mekong River finally flows into the South China Sea through many distributaries in the vast Mekong delta (c.75,000 sq mi/194,250 sq km), which occupies SE Cambodia and S Vietnam. The delta, crisscrossed by many channels and canals, is one of the greatest rice-growing areas of Asia. It is a densely populated region; Vinh Long, Can Tho, and Long Xuyen are the chief towns there. Ho Chi Minh City (Saigon) is located just east of the delta. The Mekong delta was the scene of heavy fighting in the Vietnam War.
The Mekong River is navigable for large vessels c.340 mi (550 km) upstream; Phnom Penh is a major port. North of the Cambodian border, the Mekong was navigable in short sections, but dams and other developments have increased the reach of river traffic in the 21st cent. At Khone Falls, a series of rapids (6 mi/9.7 km long) in S Laos, the Mekong drops 72 ft (22 m). The falls are the site of a hydroelectric power station, part of the Mekong Scheme, a project undertaken by the United Nations in the early 1960s to develop the potentials of the lower Mekong basin. The project sought to improve navigation, provide irrigation facilities, and produce hydroelectricity. The Mekong River Commission, whose members consist of Cambodia, Thailand, Laos, and Vietnam, intends to pursue similar joint projects and to explore the establishment of fisheries and the construction of a trans-Indochinese roadway system. China is developing the upper Mekong, constructing a series of dams to provide hydroelectric power and a navigable waterway; the first, at Manwan, was completed in 1993. Laos is also undertaking an extensive hydroelectric development of the river and its tributaries.
The Mekong is one of the world’s major rivers. It is the 11th-longest river in the world, and 7th longest in Asia. (discharging of water annually). Its estimated length is , and it drains an area of . From the Tibetan Plateau it runs through China's Yunnan province, Burma, Thailand, Laos, Cambodia and Vietnam. All except China and Burma belong to the Mekong River Commission. A South Asian regional association, Mekong-Ganga Cooperation is named after this river. The extreme seasonal variations in flow and the presence of rapids and waterfalls have made navigation extremely difficult.
In English it is called "the Mekong River", but in the Tai languages it is essentially the "Khong River." Such is the case with the Mae Nam Ping in Chiang Mai which is known as the "Ping River", and the Tonle Sap in Cambodia - where Tonle translates as "Great lake or river", making the Tonle Sap River an unnecessary repetition of what is in fact the "Sap River."
In Thai, โขง is a species of crocodile; some believe this is tone-shifted from คด or โค้ง , both adjectives to describe curves or meanders of a river or road.
In the Upper Mekong, the northern part of the river down to the Burma-Thai-Laos boarder, the river is relatively clear and fast flowing with the influx snowmelt guaranteeing a relatively uniform circumannual flow in the river. The water tends to be neutral, with a pH of 6.9 ranging to 8.2 and the nutrient level is low. In the Lower Mekong area the river is turbid , especially during the rainy season. Due to bank erosion the water gets a rusty-tan colour from the soil. The river temperature in the Lower Mekong varies between 21.1°C to 27.8°C and the pH fluctuates between 6.2 to 6.5. The two main biotopic areas in the river follow the division between the Upper and Lower Mekong. The fish in the fast-flowing upper reaches are dominated by different loaches (Cobitidae), sucker catfish (Sisoridae), hillstream loach (Homalopteridae) and carp (Garrinae). The slower middle and lower parts of the river are dominated by species of carp (Cyprinidae), catfish (Siluridae, Clariidae, Schilbeidae, Bagridae, Sisoridae and Akysidae) and murrels (Chanidae and Ophicephalidae).
No other river is home to so many species of very large fish. The biggest include the Giant River Carp (Probarbus jullieni), which can grow up to 1.5m and weigh 70kg, the Giant pangasius (Pangasius sanitwongsei), Siamese giant carp (Catlocarpio siamensis) and the endemic Mekong Giant Catfish (Pangasianodon gigas), all three of which can grow up to about 3m in length and weigh 300 kg. All of these are in serious decline, both because of dams and flood control and overfishing.
The endangered Siamese crocodile (Crocodylus siamensis) is reported to occur along the Mekong but is very rare.
The difficulty of navigating the river has meant that it has divided, rather than united, the people who live near it. The earliest known settlements date to 2100 BCE, with Ban Chiang being an excellent example of that early Iron Age culture. The earliest recorded civilisation was the 1st century Indianised-Khmer culture of Funan, in the Mekong Delta. Excavations at Oc Eo, near modern An Giang, have found coins from as far away as the Roman Empire. This was succeeded by the Khmer culture Chenla state by around the 5th century. The Khmer empire of Angkor was the last great Indianized state in the region. From around the time of the fall of the Khmer empire, the Mekong was the frontline between the emergent states of Siam and Tonkin (North Vietnam), with Laos and Cambodia, then situated on the coast, torn between their influence.
The first European to encounter the Mekong was the Portuguese Antonio de Faria in 1540; a European map of 1563 depicts the river, although even by then little was known of the river upstream of the delta. European interest was sporadic: the Spaniards and Portuguese mounted some missionary and trade expeditions, while the Dutch Gerrit van Wuysthoff led an expedition up the river as far as Vientiane in 1641-42.
The first systematic exploration began with the French Mekong Expedition led by Ernest Doudard de Lagrée and Francis Garnier, which ascended the river from its mouth to Yunnan between 1866 to 1868. Their chief finding was that the Mekong had too many falls and rapids to ever be useful for navigation. The river's source was located by Pyotr Kuzmich Kozlov in 1900.
From 1893, the French extended their control of the river into Laos, establishing French Indochina by the first decade of the 20th century. This lasted until the First and Second Indochina Wars ended French and American involvement in the region.
After the Vietnam War, the tensions between the U.S.-backed Thai government and the new Communist governments in the other countries prevented cooperation on use of the river.
There is also a third bridge, located in Champasak province, in Laos. Unlike the Friendship bridges, this bridge is not a border crossing. It is long, and was completed in 2000 (Pakxe bridge ).
|Mekong Dams||compl.||MW||Geo coordinate|
The two most controversial current issues are the building of dams and the blasting of rapids.
A number of dams have already been built on the river's tributaries, notably the Pak Mun dam in Thailand. This has been criticized on grounds of cost as well as damage to the environment and to the livelihoods of affected villagers, though none have been built on the main part itself.
China is engaged in an extensive program of dam-building on the river itself: it has already completed one at Manwan, a second is under construction at Dachaoshan, and another twelve are under consideration.
Poverty stricken Cambodia is one nation that is completely dependent on the river for food and the vast majority of its fledgling economy. The annual floods provide much needed water for crops of the otherwise dry dusty land, and to refresh Tonle Sap, yet its major cities are all vulnerable to flooding. The Mekong River Commission, a panel of the region's nations, has accused China of blatant disregard for the nations downstream in its plans to dam the river in an effort to stop the dams, but to no avail. Since the building of the first Chinese dam, many species have become endangered including the Mekong dolphin and manatee, water levels have dropped as ferries get stuck, fish caught are small and the catch is less than half of before the dam, the turnover at Chiang Rai port is less than 1/4 of previous years, and crossings from Chiang Rai to isolated Luang Prabang have lengthened from 8 hours to 2 days due to inadequate water levels.
Despite all these problems, new dams planned will have significantly worse impact if carried out as planned. All nations downstream and the environment will suffer from added pollution (due to development and relatively lax regulation and enforcement in China compared to Thailand, poisoning the food supply from pesticide runoff and heavy industry, as well as promoting algal blooms from organophosphates from agriculture, as well as water hyacinth infestation), river blockage problems as fish cannot swim upstream to spawn, and potentially devastating very low water flow.
Other environmental concerns arise from increased water flow in some parts as well as China clears rocks and sandbars, blasts gorges, and slows water as it dams and floods other sections, and relocates indigenous peoples. Cambodia by far the most exposed, depending on a fine balance of water flow, fearing scenarios of mass famine and devastating floods, the likes of which destroyed the Angkor kingdom 700 years ago. Laos' biggest cities all hug the Mekong as does Vietnam's largest city and financial hub, Ho Chi Minh City, which would be vulnerable mostly to low flow and pollution.