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Ayeyarwady River

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Ayeyarwady River

Irrawaddy ()
Ayeyarwady
River
The new Irrawaddy Bridge at Sagaing, Ava Bridge behind
Country Burma
Tributaries
 - left Chindwin, Mu
 - right Myitnge
Cities Myitkyina, Mandalay, Bhamo
Source Mali River[1]
 - coordinates 22|0|N|97|23|0|E|type:river_region:MM name=

}}

Secondary source N'Mai River
 - coordinates 4|0|N|98|8|0|E|type:river_region:MM name=

}}

Source confluence
 - location Damphet, Kachin State
 - elevation 147 m (482 ft)
 - coordinates 42|0|N|97|30|0|E|type:river_region:MM name=

}}

Mouth Andaman Sea
 - location Ale-ywa, Ayeyarwady Division, Burma
 - elevation 0 m (0 ft)
 - coordinates 51|19|N|95|14|27|E|type:river_region:MM name=

}}

Length 2,170 km (1,348 mi)
Basin 413,710 km2 (159,734 sq mi)
Discharge
 - average 13,000 m3/s (459,091 cu ft/s)
 - max 32,600 m3/s (1,151,258 cu ft/s)
 - min 2,300 m3/s (81,224 cu ft/s)
Course, watershed, cities and major tributaries of the Irrawaddy River

The Irrawaddy River or Ayeyarwady River (, pronounced: [ʔèjàwədì mjɪʔ], also spelt Ayeyarwaddy) is a river that flows from north to south through Burma (Myanmar). It is the country's largest river and most important commercial waterway. Originating from the confluence of the N'mai and Mali rivers, it flows relatively straight North-South before emptying through the Irrawaddy Delta into the Andaman Sea. Its drainage area of about 255,081 km² covers a large part of Burma. After Rudyard Kipling's poem, it is sometimes referred to as 'The Road to Mandalay'.

As early as the sixth century the river was used for trade and transport. Having developed an extensive network of irrigation canals, the river became important to the British Empire after it had colonized Burma. The river is still as vital today, as a considerable amount of (export) goods and traffic moves by river. Rice is produced in the Irrawaddy Delta, irrigated by water from the river.

In 2007, Burma's military government signed an agreement for the construction of seven dams, yielding a total 13,360 kW, in the N'mai and Mali Rivers, including the 3,600 kW Myitsone Dam at the confluence of both rivers. Environmental organisations have raised concerns about the ecological impacts on the river's biodiverse ecosystems. Animals potentially impacted include the threatened Irrawaddy dolphin.

Etymology

The Burmese name of Irrawaddy (transliterated by the current government of Burma as Ayeyarwady) is derived from the ancient name of the river Ravi, also called Iravati, in India, but through its Pali, rather than its Sanskrit form.[2] Airavati in turn is the name of the elephant mount of Indra, an Indian god. Elephants were in Indian mythology often a symbol for water[3]

The Irrawaddy gives its name to a dolphin, the Irrawaddy dolphin (Orcaella brevirostris), which is found in the lower reaches of the river and known to help fishermen who practice cast-net fishing. Though sometimes called the Irrawaddy River Dolphin, it has been also found at sea.[4][5]

Physiography

The Irrawaddy River bisects Burma from north to south and empties through the nine-armed Irrawaddy Delta into the Indian Ocean.

Source

The Irrawaddy River arises by the confluence of the N'mai and Mali Rivers in Kachin State. Both the N'mai and Mali Rivers find their sources in the Himalaya glaciers of Northern Myanmar, in the vicinity of 28° N. The eastern branch of the two, N'mai, river[6] is the larger stream and rises in the Languela Glacier north of Putao.[7] It is unnavigable because of the strong current whereas the smaller western branch, the Mali river, is navigable, despite a few rapids. Herefore, the Mali river is still called by the same name as the main river by locals.[8] The controversial Myitsone Dam is currently under construction at the convergence of these rivers.

The town of Bhamo, about 240 kilometres (150 mi) south of the Mali and N'mai river confluence, is the northernmost city reachable by boat all the year round although during the monsoons most of the river cannot be used by boats. The city of Myitkyina however lies 50 kilometres (31 mi) south of the confluence and can be reached during the dry season.

Defiles

Between Myitkyina and Mandalay, the Irrawaddy flows through three well-marked defiles:[9]

  • About 65 kilometres (40 mi) downstream from Myitkyinā is the first defile.
  • Below Bhamo the river makes a sharp westward swing, leaving the Bhamo alluvial basin to cut through the limestone rocks of the second defile. This defile is about 90 metres (300 ft) wide at its narrowest and is flanked by vertical cliffs about 60 to 90 metres (200–300 ft) high.
  • About 100 kilometres (62 mi) north of Mandalay, at Mogok, the river enters the third defile. Between Katha and Mandalay, the course of the river is remarkably straight, flowing almost due south, except near Kabwet,[10] where a sheet of lava has caused the river to bend sharply westward.

This sheet of lava is the Singu Plateau, a volcanic field from the Holocene. This field exists of magma from the fissure vents and covers an area of about 62 square kilometres (24 sq mi). The plateau is also known as Letha Taung.[11]

Leaving this plateau at Kyaukmyaung,[12] the river follows a broad, open course through the central dry zone[13] – the ancient cultural heartland[14] – where large areas consist of alluvial flats. From Mandalay (the former capital of the kingdom of Myanmar), the river makes an abrupt westward turn before curving southwest to unite with the Chindwin River, after which it continues in a southwestern direction. It is probable that the upper Irrawaddy originally flowed south from Mandalay, discharging its water through the present Sittoung River to the Gulf of Martaban, and that its present westward course is geologically recent. Below its confluence with the Chindwin, the Irrawaddy continues to meander through the petroleum producing city of Yenangyaung, below which it flows generally southward. In its lower course, between Minbu and Prome, it flows through a narrow valley between forest-covered mountain ranges—the ridge of the Rakhine Yoma Mountains[15][16] to the west and that of the Pegu Yoma Mountains to the east.[17][18]

The Irrawaddy Delta

Main article: Irrawaddy Delta

The delta of the Irrawaddy begins about 93 kilometres (58 mi) above Hinthada (Henzada) and about 290 kilometres (180 mi) from its curved base, which faces the Andaman Sea. The westernmost distributary of the delta is the Pathein (Bassein) River, while the easternmost stream is the Yangon River, on the left bank of which stands Myanmar's former capital city, Yangon (Rangoon). Because the Yangon River[19] is only a minor channel, the flow of water is insufficient to prevent Yangon Harbour from silting up, and dredging is necessary. The relief of the delta's landscape is low but not flat.[20] The soils consist of fine silt, which is replenished continuously by fertile alluvium carried downstream by the river. As a result of heavy rainfall varying from 2,000 to 3,000 millimetres (79–118 in) a year in the delta,[21] and the motion and sediment load of the river,[22] the delta surface extends into the Andaman Sea at a rate of about 50 metres (160 ft) per year.[23]

Hydrography

Due to it also silted up around 278 tons of sand every year.

Variation between high and low waterlevel is also great.[27] At Mandalay and Prome, a range of 9.66 to 11.37 metres (31.7–37.3 ft) has been measured between low-water level and floodlevel respectively. Because of the monsoonal character of the rain, the highest point is recorded in August, the lowest in February.

This variation in water level makes it necessary for ports along the river to have separate landing ports for low- and high-water.[27] Still, low water levels have caused problems for ports along the river,[28] as in the BamawMandalayPyay sectors, the shallowest point is as shallow as 60 centimetres (2.0 ft).[29]

Within the basin, the average population density is 79 people/km². For these people, the river supply amounts to 18,614 m³ per person per year.[30]

Ecology



The Irrawaddy river is home to a large diversity of animals, including about 43 fishspecies.[31]

The most well-known of these species is the Irrawaddy Dolphin (Orcaella brevirostris), a euryhaline species of Oceanic dolphin with a high and rounded forehead, lacking a beak. It is found in discontinuous sub-populations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and South-East Asia.

Along the North-South course of the Irrawaddy River, a number of notably different ecoregions can be distinguished.

Northern Mountains

The streams of the Nmai and Mali that form the Irrawaddy originate in high and remote mountains near the border with Tibet. This part of Burma, which extends north from Myitkyina and the Irrawaddy confluence, lies entirely outside the tropics. Rain falls at all seasons of the year, but mostly in the summer. The valleys and lower hill ranges are covered with tropical and subtropical evergreen rainforest instead of monsoon (deciduous) forest. This region is characterised by subtropical and temperate forests of oak and pine are found at elevations above 900 metres (3,000 ft). This evergreen forest passes into sub-tropical pine forest at about 1,500 metres (4,900 ft) feet. Above 1,800 metres (5,900 ft), are forests of rhododendrons, and that in turn into evergreen conifer forest above 2,400 metres (7,900 ft) feet.

The Central Basin and Lowlands

The Irrawaddy river basin covers an approximate area of 255 81 km2 (31 sq mi).[32] The Central Basin consists of the valley of the middle Irrawaddy and lower Chindwin. It lies within the 'dry zone' and consists almost entirely of plains covered with the teak-dominated Irrawaddy Moist Deciduous Forest ecoregion surrounding drier patches of dry forests. The central basin receives little rain (ave 650mm per year) although it does flood quickly during the July–October storms. The one meteorological factor which does not vary greatly, and which is the most important for plant life, is atmospheric humidity. This is always high, except in the winter in certain localities. Humidity usually does not fall below 75% and is 90% or more for long periods during summer. Another feature is the prevalent southerly summer winds which erode the soil of the basin.

The natural habitats of this central zone have been much altered for farming and there are few protected areas.

Irrawaddy dry forests

The predominant trees of the drier patches are the thorny Terminalia oliveri and the hardwood dahat teak (Tectona hamiltoniana) with stands of Indaing Dipterocarpus tuberculatus which is cut for timber. The wildlife includes many birds, small mammals and reptiles such as the huge Burmese python. However, most of the large animals including the tiger have been hunted out or seen their habitats disappear.

Irrawaddy Delta Area


The Irrawaddy River and its tributaries flow into the Andaman Sea through the Irrawaddy Delta. This ecoregion consists of mangroves and freshwater swamp forests. It is an extremely fertile area because of the river-borne silt deposited in the delta. The upper and central portions of the delta are almost entirely under cultivation, principally for rice. The southern portion of the ecoregion transitions into the Myanmar Coast mangroves[33] and is made up of fanlike marshes with oxbow lakes, islands, and meandering rivulets and streams.[34][35]

Birds of the delta are both winter visitors and passage migrants including Phalacrocorax carbo, a wide variety of Anatidae, Fulica atra, about 30 species of migratory shorebirds, Chlidonias hybrida, Hydroprogne caspia, and the Brown-headed Gull (Larus brunnicephalus), which is very common. One of the most numerous wintering shorebird is the Lesser Sand Plover (Charadrius mongolus), which occurs in flocks of many thousands along the outer coast of the delta. The Wood Sandpiper and Red Junglefowl (Tringa glareola) are also abundant.

In the late 19th century, the Spot-billed Pelican (Pelecanus philippensis) nested in huge numbers in south Burma. One colony on the Sittang plain to the east of the delta was described in November 1877 as covering 300 square kilometres (100 sq mi) and containing millions of birds. Immense colonies still bred in the area in 1910, but the birds had disappeared completely by 1939. Small numbers were regularly reported in the delta in the 1940s, but no breeding sites were located. As of 2010, no pelicans have been recorded, and it may well be that the species is now extinct in Burma.[36]

Several species of large mammal occur in the delta, but their populations are small and scattered, with the possible exceptions of the Malayan Sambar (Cervus unicolor equinus), Hog Deer (C. porcinus), and Wild Boar (Sus scrofa), which have been reported from all Reserved Forests. Asian Elephants (Elephas maximus) were once widespread throughout the country with numbers as high as 10,000 animals, but in the last decade numbers have dwindled, partly due to transferring the animals to logging camps.[37] Other species reported to be present include the Leopard, Bengal Tiger, Crab-eating macaque, Wild Dog, and otters (Panthera pardus, P. tigris, Cuon alpinus, and Lutra species).[38]

The estuarine crocodile (Crocodylus porosus) can be found in the Southern part of the river delta. The species was formerly abundant in coastal regions of Burma, but is now known principally from the lower Ayeyarwady Delta. Population numbers have decreased because of a combination of commercial skin hunting, habitat loss, drowning in fishing nets and over-collection of living animals to supply crocodile farms.[39]

It was at this river that a battle between a crocodile and a tiger was observed, which ended with the reptile devouring the tiger.[40]

Despite recent declines in the Sea Turtle populations, five species are known to nest in Burma at well known island and mainland beaches known as turtle-banks. These are the Olive Ridley (Lepidochelys olivacea), loggerhead (Caretta caretta), green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) marine turtles.[41]

Tributaries

The Irrawaddy River has five major tributaries. As they flow through the northern tip of Burma – the Kachin State – they cut long north-south alluvial plains and relatively narrow upland valleys between the 2,000 to 3,000 metres (7,000–10,000 ft) mountain ridges.[42] The rivers joining the Irrawaddy are, from north to south:

  1. Taping River
  2. Shweli River
  3. Myitnge River
  4. Mu River
  5. Chindwin River

Economy and politics


As early as the sixth century, ancestors of the Burmese were using the Irrawaddy river, which runs through the center of Burma, to gain power in the region through trade and transport on the China – India route. By the twelfth century, a well-developed network of irrigation canals made for flourishing rice cultivation. Later, the river became a key economic tool of British interests, who set up trading ports along its shores.[43]

Today, the Irrawaddy is still the country's most important commercial waterway. Despite Mandalay's position as the chief rail and highway focus in northern Burma, a considerable amount of passenger and goods traffic moves by river. As the Irrawaddy Delta is one of the world's major rice-growing areas, one of the most important goods transported is rice. Teak logs – Myanmar is one of the world's top exporters – are floated down the river as large rafts. Before it is transported, teak has to be seasoned, because otherwise it won't float.[44] This happens by girdling, a practice where a deep circular cut through bark and sap is made into the heartwood. Other major goods that are transported from the nation's heartlands to Yangon for export are other foodstuffs, petroleum, cotton, and local commodities.

Commercial transportation on the Irrawaddy is maintained for about 1,300 km: from Hinthada to Bhamo (1,080 km) throughout the year, but from Bhamo to Myitkyina (200 km) for only seven months. More than 3,200 km of navigable waterways exist in the Irrawaddy delta, and there is a system of connecting canals. The Sittang is usable by smaller boats, but the Salween, because of its rapids, is navigable for less than 160 km from the sea. Small steamers and country boats also serve the coasts of the Rakhine and Tenasserim regions. On the Chindwin River, transportation is carried on by steam or diesel vessels throughout the year up to Homalin—about 640 km from its confluence with the Irrawaddy. Seasonal navigation is carried on into Tamanthi, which is 57 miles (92 km) by river above Homalin.

The Chindwin valley has no railroad and relies heavily on river transport. Chauk, downstream from the confluence in the oil-field district, is a petroleum port. It is linked to Yangon by road and rail. Hinthada, near the apex of the delta, is the rail junction for lines leading to Kyangin and Bassein (Pathein). A ferry operates between Hinthada on the west bank and the railway station at Tharrawaw on the east bank.

Dams

Burma's junta signed an agreement with China Power Investment Corporation in May 2007 for the construction of seven hydroelectric dams along the Irrawaddy, Mali, and N'Mai River in Kachin State. The total planned output of all seven plants will be 15,160 MWs of electricity, making it the largest hydropower project in Burma, surpassing the 7,100 MW TaSang Dam in Shan State.[45] The following data is available for the dam locations:

Capacity, Height and Length Data for the Dam Projects
Location Myitsone Chibwe Pashe Lakin Phizaw Khaunglanphu Laiza
Height (m) 152 47,5
Length (m) 152 220
Capacity (MW) 3,600 2,800 1,600 1,400 1,500 2,700 1,560

The power generated by the dams will be transmitted to other countries in the South-East Asian region, with most going to China.[46] Other countries targeted for power export are Thailand, India and Bangladesh.

The largest of the seven, the

Chinese involvement comes from Changjiang Institute of Surveying, Planning, Design and Research.

At least one Japanese company is involved, Kansai Electric Power Company.[49]

Controversy


Due to its location and size, construction of the Myitsone Dam has raised significant ecological and sociological concerns. According to the Irrawaddy Myitsone Dam Multipurpose Water Utilizing Project study, the maximum water level of the reservoir will be 290 metres. This makes for a flood zone of 766 km2, compromising 47 villages.[50]

Other consequences of the inundation include loss of farmland, loss of spawning habitat as fishes can not swim upstream anymore. The Myanmar.

Ecological concerns focus on the inundation of an area that is the border of the Indo-Burma and South Central China biodiversity hotspots. The Mali and N'mai River confluence region falls within the Mizoram-Manipur-Kachin rainforests, added to the WWF list of outstanding examples of biodiverse regions.[52]

The location of the Myitsone Dam, located less than 100 km from a fault line where the Eurasian and Indian tectonic plates meet, raised concerns about its earthquake resistance. Earthquakes in the region, such as the 5.3 magnitude earthquake that struck near the Burma-China border on 20 August 2008,[53] prompted Naw Lar, the coordinator of the KDNG dam research project, to ask the junta to reconsider its dam projects.[54]

Major cities and towns

The river flows through the following cities:

Bridges

Until the construction of the Ava (Innwa) Bridge, a 16 span rail and road cantilever bridge built by the British colonial government in 1934, the only way across the Irrawaddy was by ferry. The bridge was destroyed by the retreating British Army during the World War II and was rebuilt in 1954 after Burmese independence and was the only bridge to span the Irrawaddy until recent times when a spate of bridge construction has been carried out by the government.[55][56]

  1. Bala Min Htin Bridge over the N'Mai Hka at Myitkyina, November 1998
  2. Irrawaddy Bridge (Yadanar Pone Bridge/New Ava Bridge) at Sagaing, April 2008
  3. Anawrahta Bridge at Chauk, March 2001[57]
  4. Ayeyarwady-Magway Bridge at Magway
  5. Bo Myat Tun Bridge at Nyaungdon, November 1999
  6. Nawaday Bridge at Pyay, September 1997
  7. Maubin Bridge at Maubin, February 1998
  8. Ayeyarwady-Dedaye Bridge at Dedaye, March 2003[58]

Gallery

Notes

External links

  • On Thinner Ice 如履薄冰: signs of trouble from the Water Tower of Asia, where headwaters feed into all the great rivers of Asia (by GRIP, Asia Society and MediaStorm)
  • NASA Earth Observatory
  • image
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