IRRAWADDY RIVER BASIN
The names of the Irrawaddy
The Irrawaddy is the biggest river in Myanmar, into which most of the river’s basin falls. Here, it is known as the Ayeyarwady. The river itself is often regarded as only starting at the confluence of two of its major tributaries, the N’Mai and the Mali Rivers, which converge in southern Kachin State. Nevertheless, these two rivers are part of the Irrawaddy’s basin. The N’Mai rises in the eastern glaciers of the Tibet Autonomous Region of China, while the Mali rises in Kachin’s northern mountains. Other important tributaries are the Shweli, which rises in China’s Western Yunnan Province, and where it is known as the Long Jiang; and the Chindwin River, the largest tributary of the Irrawaddy.
80% of the Irrawaddy’s annual flow falls with the monsoon between May and October. This huge surge of water is referred to as a ‘flood pulse’, and causes extensive flooding throughout the system.
The Irrawaddy is about 2,170 km long, while its basin covers 413,710 km² of which 91% lies within Myanmar, around 5% (21,400 km²) in China, and 4% (17,400 km²) in India. The river discharges about 400 km³ of water into the Andaman Sea. This is equivalent to about 160 million Olympic-sized swimming pools.
The Irrawaddy is heavily sedimented. It is currently ranked as carrying the fifth largest suspended sediment load globally, with estimates ranging from 261 to 364 million tons per year.
While it’s wet, it’s also dry
The ‘Dry Zone’ lies within Myanmar’s central plains, which are bounded by mountains to the east and west. Encompassing parts of Mandalay, Magway and Sagaing, it covers more than 75,000 km² and represents 13% of Myanmar’s land area. It is the driest region in Myanmar, receiving between 500 and 1,000 mm a year. In contrast, areas in northern Kachin State receive up to 4,000 mm a year.
The ARB encompasses 14 major ecoregions, with a variety of montane, alpine, temperate and subtropical forest ecosystems.
The river is home to the critically endangered Irrawaddy Dolphin, found mainly in the coastal regions of the Delta. There is a small population of dolphins in a 200 km stretch north of Mandalay. This population is famous for cooperative fishing with local communities.
The biodiversity of the river’s fisheries is fairly low if compared with the Mekong. About 200 species of fish are thought to live in the Irrawaddy.
A river of development
The Irrawaddy is Myanmar’s most economically important river. Many of its largest urban areas – including Yangon – fall within its basin. The total population in the basin was estimated at 39.5 million people in 2015, with about 1.9 million in Yunnan, 2.8 million in India and 35 million in Myanmar– making up about 66% of that country’s total population.
The Irrawaddy has a large hydropower potential, and Myanmar’s soaring electricity demand has focused on developing this. Currently, there are a total of 41 hydropower dams in the basin, mostly concentrated in China (35). The Irrawaddy’s irrigation potential has also been heavily developed – in Myanmar, there are some 115 irrigation dams with a reservoir surface are of 0.5 km² and above.
The Irrawaddy Delta is a zone of intensive economic activity. Some 60% of Myanmar’s rice harvest come from the four states that share the Delta.
Fisheries constitute an important source of livelihoods in the Basin. Little is known, however, about the magnitude of fish landings.
Loosing forests and other environmental challenges
Forest ecosystems are under pressure from rapid deforestation; it is estimated that Myanmar lost more than 546,000 hectares of forest a year between 2010-15. Over half of the loss occurred in Chindwin in the Kachin and Shan States, and the Sagaing Region. Forest loss has mainly been due to illegal and legal timber extraction; forest clearing for the expansion of commercial agriculture is now, however, becoming the leading cause of deforestation in Myanmar.
The Irrawaddy Basin contains significant mining resources, such as jade, coal, gold and other minerals. The river is increasingly threatened by chemicals used in mining operations, and also in agriculture.
An ancient river
The astonishing stupas of Bagan are located within the Irrawaddy River Basin. So too, Mandalay – the seat of Burma’s former royal house – is located in the Basin.
IRRAWADDY RIVER BASIN MAP
Click below to download the Irrawaddy River Basin map.