Irrawaddy River, Burmese Ayeyarwady, principal river of Myanmar (previously Burma), working via the centre of the nation. Myanmar’s most essential business waterway, it’s about 1,350 miles (2,170 km) lengthy. Its identify is believed to derive from the Sanskrit time period airāvatī, which means “elephant river.” The river flows wholly throughout the territory of Myanmar. Its complete drainage space is about 158,700 sq. miles (411,000 sq. km). Its valley varieties the historic, cultural, and financial heartland of Myanmar.
The Irrawaddy is shaped by the confluence of the Nmai and Mali rivers. Each branches rise within the glaciers of the excessive and distant mountains in northern Myanmar within the neighborhood of 28° N.
The depth of the primary channel averages about 30 toes (9 metres).
About 40 miles (65 km) downstream from Myitkyinā is the primary defile. Under Bhamo the river makes a pointy westward swing, leaving the Bhamo alluvial basin to chop via the limestone rocks of the second defile. Between Katha and Mandalay, the course of the river is remarkably straight, flowing virtually due south, besides close to Kabwet, the place a sheet of lava has brought on the river to bend sharply westward. Leaving the third defile at Kyaukmyaung, the river follows a broad, open course via the central dry zone—the traditional cultural heartland—the place massive areas encompass alluvial flats. From Mandalay (previously the capital of the dominion of Myanmar) the river makes an abrupt westward flip earlier than curving southwest to unite with the Chindwin River, after which it continues in a southwesterly course. It’s possible that the higher Irrawaddy initially flowed south from Mandalay, discharging its water via the current Sittang River to the Gulf of Martaban, and that its current westward course is geologically latest. In its decrease course, between Minbu and Prome, it flows via a slender valley between forest-covered mountain ranges—the ridge of the Arakan (Rakhine) Mountains to the west and that of the Pegu Mountains to the east.
The delta of the Irrawaddy begins about 58 miles (93 km) above Hinthada (Henzada) and about 180 miles (290 km) from its curved base, which faces the Andaman Sea. The edges of the delta are shaped by the southern extremities of the Pegu Mountains on the east and the Arakan Mountains on the west. The westernmost distributary of the delta is the Bassein (Pathein) River, whereas the easternmost stream is the Yangon River, on the left financial institution of which stands Myanmar’s largest metropolis, Yangon (Rangoon). As a result of the Yangon River is simply a minor channel, the circulate of water is inadequate to forestall Yangon Harbour from silting up, and dredging is important. The reduction of the delta’s panorama is low however not flat. The soils encompass tremendous silt, which is replenished constantly by fertile alluvium carried downstream by the river. On account of heavy rainfall and the movement and sediment load of the river, the delta floor extends into the Andaman Sea at a price of about 165 toes (50 metres) per yr.
The decrease Irrawaddy River basin has a moist tropical local weather, whereas the higher river basin has a heat humid subtropical local weather. Each climatic zones are dominated by the South Asia summer time monsoon, which brings the heaviest rains between Could and October. At Yangon, within the decrease basin, temperatures vary from a January imply of 77 °F (25 °C) to an April imply of 86 °F (30 °C); temperatures fall barely through the summer time wet season. Temperatures lower with altitude up the basin to the glaciated areas the place imply annual temperatures are under 68 °F (20 °C). Precipitation varies throughout the basin from 60 to 100 inches (1,500 to 2,500 mm) per yr and falls primarily from Could to October.
The quantity of the Irrawaddy and its tributaries fluctuates significantly via the yr, mainly due to the character of the monsoon rains, which happen between Could and October, but in addition due to the fast melting of snow and glaciers through the summer time, which provides nonetheless additional to the quantity. The typical discharge of the river close to the pinnacle of the delta varies between a low of 82,000 and a excessive of 1,152,000 cubic toes (2,300 and 32,600 cubic metres) per second; the annual common discharge is 460,000 cubic toes (13,000 cubic metres) per second. The vary between excessive and low water can also be nice. The bottom water degree happens in February, and the best in August. Usually, from December to March the river varies between the bottom degree and 5 toes (1.5 metres) above it, whereas from mid-June to mid-October the river is 20 to 30 toes (6 to 9 metres) above the bottom degree. The river ports subsequently discover it essential to have separate high- and low-water touchdown factors.