Mekong

Etymology of the Mekong River The name Mekong is derived from the Khmer-Sanskrit compound Me-Kongkea (Khmer: មេគង្គា), literally translating to "Mother Ganga." This name reflects a "Sacred Geography" established during the Indianization of Southeast Asia, specifically during the period of Shailendra (Javanese) influence over Water Chenla and the subsequent Khmer Empire. Linguistic Origins The etymology is composed of two distinct linguistic layers: • Me (មេ): An Austroasiatic (Khmer) root meaning "Mother," "Chief," or "Head." In Khmer nomenclature, it is used to designate the primary or most significant member of a category (e.g., Me-phum for village head). • Kongkea (គង្គា): A direct phonetic loan from the Sanskrit Ganga (गङ्गा), referring to the sacred Ganges River of India. In the Khmer language, the "G" sound from Sanskrit typically shifts to a "K" or "Kh" sound. Over centuries of common usage, the formal Me-Kongkea was shortened to Me-Kôngk (មេគង្គ), which was later phoneticized by Western cartographers as Mekong and by Tai-Kadai speakers as Mae Nam Khong (แม่น้ำโขง) and (ແມ່ນ້ຳຂອງ.) The Mekong was originally called Mae Nam Khong from a contracted form of Kra-Dai shortened to Mae Khong. In Thai and Lao, Mae Nam ("Mother of Water[s]") is used for large rivers and Khong is the proper name referred to as "River Khong". However, Khong is an archaic word meaning "river", loaned from Austroasiatic languages, such as Vietnamese sông (from *krong) and Mon kruŋ "river", which led to Chinese whose Old Chinese pronunciation has been reconstructed as and which long served as the proper name of the Yangtze before becoming a generic word for major rivers. To the early European traders, the Mekong River was also known as Mekon River, May-Kiang River and Cambodia River. Historian William Dalrymple suggests that Mekong comes from "Mā Gaṅgā" (Khmer: ម៉ែគង្គា ; UNGEGN: Mê Kôngkéa) which means Mother Ganges. Hindus think of the river Ganges as mother. The local names for the river include: • From Thai: • , , or just . • , , or just . • , , or just . • , , or just . • Tai Lue: , . • or . • Other: • () or , ( Nine Dragons River ). • . • , . • Tônlé Thum (lit. "Big River" or "Great River") or Mékôngk , Tônlé Mékôngk . • Khmuic: , '' means 'river' or 'water', here it means 'river', '' means 'canal'. So '' means 'canal river'. In the ancient time Khmuic people called it or which means 'giant canal river' or 'deep canal river' respectively. ==Course==

The Mekong rises as the Za Qu (; ) and soon becomes known as the Lancang River (, from the old name of Lao kingdom Lan Xang; the characters may also be literally understood as "turbulent green river"). It originates 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 then turns east into the interior of Laos, flowing first east and then south for some before meeting the border with Thailand again. Once more, it defines the Laos-Thailand border for some 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. ==Drainage basin==

. Rivers, Laos The Mekong Basin is frequently divided into two parts: the "upper Mekong basin" comprising those parts of the basin in Tibet, Yunnan and eastern Myanmar, 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 the upper Mekong basin, a stretch of some . Here, it drops before it enters the lower basin where the borders of Thailand, Laos, China, and Myanmar come together in the Golden Triangle. Downstream from the Golden Triangle, the river flows for a further through Laos, Thailand, and Cambodia before entering the South China Sea via a complex delta system in Vietnam. Loss of forest cover in the Thai areas of the lower basin has been the highest of all the lower Mekong countries over the past 60 years. On the Khorat Plateau, which includes the Mun and Chi tributary systems, forest cover was reduced from 42% in 1961 to 13% in 1993. Reach 2: Chiang Saen to Vientiane and Nong Khai. This reach is almost entirely mountainous and covered with natural forest although there has been widespread slash and burn agriculture. Although this reach cannot be termed "unspoiled", the hydrological response is perhaps the most natural and undisturbed of all the lower basin. Many hydrological aspects of the lower basin start to change rapidly at the downstream boundary of this reach. Reach 3: Vientiane and Nong Khai to Pakse. The boundary between Reach 2 and 3 is where the Mekong hydrology starts to change. Reach 2 is dominated in both wet and dry seasons by the Yunnan Component. Reach 3 is increasingly influenced by contributions from the large left bank tributaries in Laos, namely the Nam Ngum, Nam Theun, Nam Hinboun, Se Bang Fai, Se Bang Hieng and Se Done Rivers. The Mun-Chi river system from the right bank in Thailand enters the mainstream within this reach. Reach 4: Pakse to Kratie. The main hydrological contributions to the mainstream in this reach come from the Se Kong, Se San, and Sre Pok catchments. Together, these rivers make up the largest hydrological sub-component of the lower basin. Over 25% of the mean annual flow volume to the mainstream at Kratie comes from these three river basins. They are the key element in the hydrology of this part of the system, especially to the Tonle Sap flow reversal. Reach 5: Kratie to Phnom Penh. This reach includes the hydraulic complexities of the Cambodian floodplain, the Tonle Sap and the Great Lake. By this stage, over 95% of the total flow has entered the Mekong system. The focus turns from hydrology and water discharge to the assessment of water level, over- bank storage and flooding and the hydrodynamics that determine the timing, duration and volume of the seasonal flow reversal into and out of the Great Lake. Reach 6: Phnom Penh to the South China Sea. Here the mainstream divides into a complex and increasingly controlled and artificial system of branches and canals. Key features of flow behaviour are tidal influences and salt water intrusion. Every year, 35–50% of this reach is flooded during the rainy season. The impact of road embankments and similar infrastructure developments on the movement of this flood water is an increasingly important consequence of development. Table 2 summarises the mean annual flows along the mainstream. The mean annual flow entering the lower Mekong from China is equivalent to a relatively modest depth of runoff. Downstream of Vientiane this increases to over as the principal left bank tributaries enter the mainstream, mainly the Nam Ngum and Nam Theun. The flow level falls again, even with the right bank entry of the Mun-Chi system from Thailand. Although the Mun–Chi basin drains 20% of the lower system, average annual runoff is only . Runoff in the mainstream increases again with the entry from the left bank of the Se Kong from southern Laos and Se San and Sre Pok from Vietnam and Cambodia. (monkey bridge) and small nước mắm (fish sauce) workshop on the bank of the Tiền River (branch of Mekong), Binh Dai District, Ben Tre Province, Vietnam , Binh Dai District, Ben Tre Province, Vietnam Table 2: Lower Mekong Mainstream annual flow (1960 to 2004) at selected sites. Flows at Chiang Saen entering the lower basin from Yunnan make up about 15% of the wet season flow at Kratie. This rises to 40% during the dry season, even this far downstream. During the wet season, the proportion of average flow coming from Yunnan rapidly decreases downstream of Chiang Saen, from 70% to less than 20% at Kratie. The dry season contribution from Yunnan is much more significant. The major portion of the balance comes from Laos, which points to a major distinction in the low-flow hydrology of the river. One fraction comes from melting snow in China and Tibet and the rest from over-season catchment storage in the lower basin. This has implications for the occurrence of drought conditions. For example, if runoff from melting snow in any given year is very low, then flows upstream of Vientiane-Nong Khai would be lower. In a large river system like the Mekong, seasonal flows can be quite variable from year to year. Although the pattern of the annual hydrograph is fairly predictable, its magnitude is not. The average monthly flows along the mainstream are listed in Table 3, providing an indication of their range and variability from year to year. At Pakse, for example, flood season flows during August would exceed nine years out of ten, but exceed only one year in ten. Table 3: Mekong Mainstream monthly discharge, 1960–2004 (m3/s). There is little evidence from the last 45 years of data of any systematic changes in the hydrological regime of the Mekong. ==Geology==

The internal drainage patterns of the Mekong are unusual among those of large rivers. Typically, such patterns develop in basins with gentle slopes where the underlying geological structure is fairly homogeneous 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 elevation of the Tibetan Plateau during the Tertiary period was an important factor in the genesis of the south-west monsoon, which is the dominant climatic control influencing the hydrology of the Mekong Basin. Understanding the nature and timing of the elevation of Tibet (and the Central Highlands of Vietnam) therefore helps explain the provenance of sediment reaching the delta and the Tonle Sap Great Lake today. Studies of the provenance of sediments in the Mekong delta reveal a major switch in the source of sediments about eight million years ago (Ma). From 36 to 8 Ma the bulk (76%) of the sediments deposited in the delta came from erosion of the bedrock in the Three Rivers Area. From 8 Ma to the present, however, the contribution from the Three Rivers Area fell to 40%, while that from the Central Highlands rose from 11 to 51%. One of the most striking conclusions of provenance studies is the small contribution of sediment from the other parts of the Mekong basin, notably the Khorat Plateau, the uplands of northern Laos and northern Thailand, and the mountain ranges south of the Three Rivers area. The last glacial period came to an abrupt end about 19,000 years ago (19 ka) when sea levels rose rapidly, reaching a maximum of about above present levels in the early Holocene about 8 ka. At this time the shoreline of the South China Sea almost reached Phnom Penh and cores recovered from near Angkor Borei contained sediments deposited under the influence of tides, and salt marsh and mangrove swamp deposits. Although the hydraulic relationships between the Mekong and the Tonle Sap Great Lake systems during the Holocene are not well understood, it is clear that between 9,000 and 7,500 years ago the confluence of the Tonle Sap and the Mekong was in proximity to the South China Sea. The present river morphology of the Mekong Delta developed over the last 6,000 years. At this time the delta was advancing at a rate of per year. After 3.5 ka, however, the delta had built out beyond the embayment and became subject to wave action and marine currents. These deflected deposition south-eastwards in the direction of the Cà Mau Peninsula, which is one of the most recent features of the delta. For much of its length the Mekong flows through bedrock channels, i.e., channels that are confined or constrained by bedrock or old alluvium in the bed and riverbanks. ==History==

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 210 BCE, with Ban Chiang being an excellent example of early Iron Age culture. The earliest recorded civilization 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 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 front line between the emergent states of Siam and Tonkin (North Vietnam), with Laos and Cambodia, then on the coast, torn between their influence. The first European to encounter the Mekong was the Portuguese António 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 Spanish 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 French invaded the region in the mid-19th century, capturing Saigon in 1861, and establishing a protectorate over Cambodia in 1863. The first systematic European 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 and 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 found 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 expelled French from its former colony and defeated US-supported governments. During the wars in Indochina in the 1970s, a significant quantity of explosives (sometimes, entire barges loaded with military ordnance) sank in the Cambodian section of the Mekong (as well as in the country's other waterways). Besides being a danger for fishermen, unexploded ordnance also creates problems for bridge and irrigation systems construction. As of 2013, Cambodian volunteers are being trained, with the support of the Office of Weapons Removal and Abatement within the US State Department Bureau of Political-Military Affairs, to conduct underwater explosive removal. The many maps of the river basin produced throughout recorded history reflect the region's changing human geography and politics. In 1995, Laos, Thailand, Cambodia, and Vietnam established the Mekong River Commission (MRC) to manage and coordinate the use and care of the Mekong. In 1996 China and Myanmar became "dialogue partners" of the MRC and the six countries now work together in a cooperative framework. In 2000, the governments of China, Laos, Thailand and Myanmar signed an ''Agreement on Commercial Navigation on Lancang-Mekong River among the Governments of the People's Republic of China, the Lao People's Democratic Republic, the Union of Myanmar and the Kingdom of Thailand'' which is the mechanism for cooperation with regard to riverine trade on the upper stretches of the Mekong. ==Natural history==

can still be found along a stretch of the Mekong in Cambodia (Khmer called "Kanteay") The Mekong basin is one of the richest areas of biodiversity in the world. Only the Amazon boasts a higher level of bio-diversity. 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 species previously unknown to science were described from the region, including 29 fish species, 2 bird species, 10 reptiles, 5 mammals, 96 plants, and 6 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. The biggest include three species of Probarbus barbs, which can grow up to and weigh , the giant freshwater stingray (Himantura polylepis, syn. H. chaophraya), which can reach at least in length and 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 in length and weigh . 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. Protected areas • 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. Natural phenomena The low tide level of the river in Cambodia is lower than the high tide level out at sea, and the flow of the Mekong inverts with the tides throughout its stretch in Vietnam and up to Phnom Penh. The very flat Mekong delta area in Vietnam is thus prone to flooding, especially in the provinces of An Giang and Dong Thap (Đồng Tháp), near the Cambodian border. ==Fisheries==

, Vietnam 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 largest recorded freshwater fish, a giant freshwater stingray in 2022 and previously a Mekong giant catfish in 2005, were both caught in the Mekong 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% of the total Mekong catch. 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. 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. Fish are the staple of the diet in Laos and Cambodia, with around 80% of the Cambodian population's annual protein intake coming from fish caught in the Mekong River system, with no alternative source to replace it. An MRC report claims that dam projects on the Mekong River will reduce aquatic life by 40% by 2020, and predicted that 80% of fish will be depleted by 2040. Thailand will be impacted, as its fish stocks in the Mekong will decline by 55%, Laos will be reduced by 50%, Cambodia by 35%, and Vietnam by 30%. 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% of rural households (2.9 million people) rely on fisheries for either subsistence or additional cash income. Around the Tonlé Sap Lake in Cambodia, more than 1.2 million people live in fishing communes and depend almost entirely on fishing for their livelihoods. ==Dams==

Dams in the Mekong reference those built for hydropower, irrigation and other uses (such as water supply). As of February 2024, dams in the Mekong are distributed as follows: Table 4: Dams in the Mekong River Basin Notes: HPPs = Hydropower Plants. Data calculated from the CGIAR Research Program on Water, Land and Ecosystems - Greater Mekong 'Dataset on the Dams of the Irrawaddy, Mekong, Red and Salween River Basins'. Only HPPs with an installed capacity of 15 Megawatts (MW) or more are included; and/or dams with a reservoir area of 0.5 km2 or more. There are also multiple HPPs under construction within the basin. As of February 2024, there is one under construction in Cambodia, three in the TAR, and 14 in Laos. Of the Mekong's HPPs, 15 are located on the Mekong mainstream. Of these, 13 are in China, and two in Laos. An additional mainstream dam is currently under construction in Laos, and another in China. ==Navigation==

, Laos For thousands of years the Mekong River has been an important conduit for people and goods between the many towns on its banks. Traditional forms of trade in small boats linking communities continue today, however the river is also becoming an important link in international trade routes, connecting the six Mekong countries to each other, and also to the rest of the world. China has been the driving force behind the demolition plan as it aims to expand trade in the area. The plan is split into two phases. The first phase, from 2015 to 2020, involves a survey, a design, and an assessment of the environmental and social impacts of the project. These have to be approved by the four countries involved: China, Laos, Myanmar, Thailand. The second phase (2020–2025) involves navigational improvements from Simao in China to 243 border posts in China and Myanmar, a distance of . On 4 February 2020, the Thai Cabinet voted to stop the project to blast and dredge of the river bed after Beijing failed to stump up the money for further surveys of the affected area. ==Bridges==

Construction of Myanmar–Laos Friendship Bridge started on 19 February 2013. The bridge will be long and have an wide two-lane motorway. The First Thai–Lao Friendship Bridge connects Nong Khai city with Vientiane in Laos. The bridge opened on 8 April 1994. It has two lanes with a single railway line in the middle. On 20 March 2004, the Thai and Lao governments agreed to extend the railway to Tha Nalaeng in Laos. This extension has since been completed. The Second Thai–Lao Friendship Bridge connects Mukdahan to Savannakhet. The two-lane, , bridge opened to the public on 9 January 2007. The Third Thai–Lao Friendship Bridge opened for traffic on 11 November 2011, connecting Nakhon Phanom Province (Thailand) and Thakhek (Laos), as part of Asian Highway 3. The Chinese and Thai governments agreed to build the bridge and share the estimated US$33 million cost. , China The Fourth Thai–Lao Friendship Bridge opened to traffic on 11 December 2013. It links Chiang Rai Province, Thailand with Ban Houayxay, Laos. There is one bridge over the Mekong entirely within Laos. Unlike the Friendship Bridges, it is not a border crossing. It is at Pakse in Champasak Province. It is long, and was completed in 2000. ). The Kizuna Bridge is in Cambodia, in the city of Kampong Cham, on the road linking Phnom Penh with the remote provinces of Ratanakiri and Mondolkiri, and Laos. The bridge opened for traffic on 11 December 2001. The Prek Tamak Bridge, north of Phnom Penh opened in 2010. Phnom Penh itself has no bridge under construction yet, although two new bridges have recently opened on the Tonle Sap, and the main bridge on the highway to Ho Chi Minh was duplicated in 2010. Another new bridge was built at Neak Leung on the Phnom Penh to Ho Chi Minh Highway 1 with Japanese government assistance, and opened in 2015. In Vietnam, the Mỹ Thuận Bridge was opened in 2000, crossing the first channel—the left, main branch of the Mekong, the Sông Tiền or Tiền Giang—near Vĩnh Long. Since 2008, the Rạch Miễu Bridge crosses it near Mỹ Tho, between the provinces of Tiền Giang and Bến Tre. Cần Thơ Bridge crosses the second channel—the right, main distributary of the Mekong, the Bassac (Song Hau). Inaugurated in 2010, it is the longest main span cable-stayed bridge in Southeast Asia. ==Environmental issues==

Drought linked to a changing climate and dozens of hydroelectric dams are damaging the Mekong ecosystem. When drought ends and the inevitable floods begin, the effects of Mekong dams on flood pulse dynamics over the entire Lower Mekong are poorly understood. Sewage treatment is rudimentary in towns and urban areas throughout much of the Mekong's length, such as Vientiane in Laos. Water pollution impacts the river's ecological integrity as a result. Much of the 8.3 billion tonnes of plastic present on earth makes its way to the oceans. Ninety percent of plastic in the oceans is flushed there by just 10 rivers. The Mekong is one of them. A growing number of academics, NGOs, and scientists have urged the international community and the Mekong River Commission to reduce the use of hydropower, giving concerns of long-term sustainability. Some of them have urged an immediate moratorium on new construction of hydropower projects and a shift to solar and other forms of renewable energy, which are becoming more competitive and faster to install. Sand mining of the Mekong River in the countries Laos, Cambodia and Vietnam has led to various environmental impacts on both areas local and downstream to these operations due to the disturbance of the river's natural flow. These impacts include river embankment instability, reduced supply of vital floodwater and sediments to floodplains, increased salinity levels and both the disturbance and displacement of various species. Mining in "Karen and Shan states, where tin and rare-earth mining" is causing mounting pollution (as of 2025) to the Mekong basin. ==See also==