|Origin||Lesser Abay/Lake Tana|
|Length||1,450 km (900 mi)|
|Avg. discharge||2,349 m3/s (83,000 cu ft/s)|
|Basin area||325,000 km2 (125,000 sq mi)|
The Blue Nile (Amharic: ዓባይ; transliterated: ʿAbbai, but pronounced Abbai, Arabic: النيل الأزرق An Nīl al Āzraq) is a river originating at Lake Tana in Ethiopia. With the White Nile, the river is one of the two major tributaries of the Nile. The upper reaches of the river is called the Abbay in Ethiopia, where it is considered holy by many, and is believed to be the River Gihon mentioned as flowing out of the Garden of Eden in Genesis 2.
According to materials published by the Ethiopian Central Statistical Agency, the Blue Nile has a total length of 1,450 kilometres (900 mi), of which 800 km (500 mi) are inside Ethiopia. The Blue Nile flows generally south from Lake Tana and then west across Ethiopia and northwest into Sudan. Within 30 kilometres (19 mi) of its source at Lake Tana, the river enters a canyon about 400 kilometres (250 mi) long. This gorge is a tremendous obstacle for travel and communication from the north half of Ethiopia to the southern half. The power of the Blue Nile may best be appreciated at Tis Issat Falls, which are 45 metres (148 ft) high, located about 40 kilometres (25 mi) downstream of Lake Tana.
Although there are several feeder streams that flow into Lake Tana, the sacred source of the river is generally considered to be a small spring at Gish Abbai at an altitude of approximately 2,744 metres (9,003 ft). This stream, known as the Lesser Abay, flows north into Lake Tana. Other affluents of this lake include, in clockwise order from Gorgora, the Magech, the Northern Gumara, the Reb, the Southern Gumara and the Kilte. Lake Tana's outflow then flows some 30 kilometres before plunging over the Tis Issat Falls. The river then loops across northwest Ethiopia through a series of deep valleys and canyons into Sudan, by which point it is only known as the Blue Nile.
There are numerous tributaries of the Abay between Lake Tana and the Sudanese border. Those on its left bank, in downstream order, include the Wanqa River, the Bashilo River, the Walaqa River, the Wanchet River, the Jamma River, the Muger River, the Guder River, the Agwel River, the Nedi River, the Didessa River and the Dabus River. Those on the right side, also in downstream order, include the Handassa, Tul, Abaya, Sade, Tammi, Cha, Shita, Suha, Muga, Gulla River, Temcha, Bachat, Katlan, Jiba, Chamoga, Weter and the Beles.
After flowing past Er Roseires inside Sudan, and receiving the Dinder on its right bank at Dinder, the Blue Nile joins the White Nile at Khartoum and, as the River Nile, flows through Egypt to the Mediterranean Sea at Alexandria. The Blue Nile is so-called because during flood times the water current is so high, it changes colour to an almost black; since in the local Sudanese language the word for black is also used for the colour blue.
The distance from its source to its confluence is variously reported as 1,460 and 1,600 kilometres (907 and 1,000 miles). The uncertainty over its length might partially result from the fact that it flows through a virtually impenetrable gorges cut in the Ethiopian Highlands to a depth of some 1,500 metres (4,900 ft)—a depth comparable to that of the Grand Canyon of the Colorado River in the United States.
The flow of the Blue Nile reaches maximum volume in the rainy season (from June to September), when it supplies about two thirds of the water of the Nile proper. The Blue Nile, along with that of the Atbara River to the north, which also flows out of the Ethiopian Highlands, were responsible for the annual Nile floods that contributed to the fertility of the Nile Valley and the consequent rise of ancient Egyptian civilization and Egyptian Mythology. With the completion in 1970 of the Aswan High Dam in Egypt, the Nile floods ended.
The Blue Nile is vital to the livelihood of Egypt. Though shorter than the White Nile, 59% of the water that reaches Egypt originates from the Blue Nile branch of the great river; when combined with the Atbara River, which also has its source in the Ethiopian Highlands, the figure rises to 90% of the water and 96% of transported sediment. The river is also an important resource for Sudan, where the Roseires and Sennar dams produce 80% of the country's power. These dams also help irrigate the Gezira Plain, which is most famous for its high quality cotton. The region also produces wheat and animal feed crops.
The first European to have seen the Blue Nile in Ethiopia and the river's source was Pedro Paez, a Spanish Jesuit who reached the river's source 21 April 1613. Nevertheless the Portuguese João Bermudes, the self-described Patriarch of Ethiopia, provided the first description of the Tis Issat Falls in his memoirs (published in 1565), and a number of Europeans who lived in Ethiopia in the late 15th century like Pêro da Covilhã could have seen the river long before Paez, but not reached its places of source.
Although a number of European explorers contemplated tracing the course of the Blue Nile from its confluence with the White Nile to Lake Tana, its gorge, which begins a few miles inside the Ethiopian border, has discouraged all attempts since Frédéric Cailliaud's attempt in 1821. The first serious attempt by a non-local to explore this reach of the river was undertaken by the American W.W. Macmillan in 1902, assisted by the Norwegian explorer B.H. Jenssen; Jenssen would proceed upriver from Khartoum while Macmillan sailed downstream from Lake Tana. However, Jenssen's boats were blocked by the rapids at Famaka short of the Sudan-Ethiopian border, and Macmillan's boats were wrecked shortly after they had been launched. Macmillan encouraged Jenssen to try to sail upstream from Khartoum again in 1905, but he was forced to stop 300 miles short of Lake Tana. Consul Cheesman, who records his surprise on arriving in Ethiopia at finding that the upper waters of "one of the most famous of the rivers of the world, and one whose name was well known to the ancients" was in his lifetime "marked on the map by dotted lines", managed to map the upper course of the Blue Nile between 1925–1933. He did this not by following the river along its banks and through its impassable canyon, but following it from the highlands above, travelling some 5,000 miles (8,000 km) by mule in the adjacent country.
In 1968 at the request of Emperor Haile Selassie of Ethiopia, a team of 60 British and Ethiopian servicemen and scientists made the first descent of the Blue Nile from Lake Tana to a point near the Sudan border led by the eminent explorer Captain (now Colonel) John Blashford-Snell. The team used specially built Avon inflatables and modified Royal Engineer Assault boats to navigate the formidable rapids. This expedition made many important scientific discoveries. They also had to fight off two attacks by bandits.
In 1999, writer Virginia Morell  and photographer Nevada Wier made the journey by raft from Lake Tana to the Sudan, afterwards publishing a documentary about their journey. In 2000, American and National Geographic reader, Kenneth Frantz, saw a photo take by Nevada Wier for National Geographic which would lead him to found the charity Bridges to Prosperity. This photo showed a bridge broken during World War II, with 10 men on either side of the broken span pulling each other across the dangerous gap by rope. This historic bridge was built by Emperor Fasilides of Ethiopia in approximately 1660 with Roman bridge technology brought to Ethiopia by Portuguese soldiers during the battle with the Muslim invaders in 1507. In both 2001 and 2009, Bridges to Prosperity volunteers would travel from the USA to Ethiopia to repair the broken bridge across the Blue Nile river, and later build a new cable suspended span not susceptible to flood. Bridges to Prosperity has now built over 93 footbridges in 13 countries.
On April 28, 2004, geologist Pasquale Scaturro and his partner, kayaker and documentary filmmaker Gordon Brown, became the first people to navigate the Blue Nile. Though their expedition included a number of others, Brown and Scaturro were the only ones to remain on the expedition for the entire journey. They chronicled their adventure with an IMAX camera and two handheld video cams, sharing their story in the IMAX film Mystery of the Nile and in a book of the same title. Despite this attempt, the team was forced to use outboard motors for most of their journey, and it was not until January 29, 2005, when Canadian Les Jickling and New Zealander Mark Tanner reached the Mediterranean Sea, that the river had been paddled for the first time under human power from source to sea.
- Edward Ullendorff, Ethiopia and the Bible (Oxford: University Press for the British Academy, 1968), p. 2.
- "Climate, 2008 National Statistics (Abstract)", Table A.1. Central Statistical Agency website (accessed 26 December 2009)
- These lists are based on the compilation in G.W.B. Huntingford, Historical Geography of Ethiopia from the first century AD to 1704 (London: British Academy, 1989), p. 34
- R. E. Cheesman, Geographical Journal, 71 (1928), p. 361
- Alan Moorehead, The Blue Nile, revised edition (New York: Harper and Row, 1972), pp. 319f
- Cheesman, pp. 358–374.
- Snailham, Richard. 1970. The Blue Nile Revealed. London: Chatto and Windus.
- Baynes, Thomas Spencer (1838). "Abyssinia". The Encyclopaedia Britannica: A Dictionary of Arts, Sciences, and General Literature, Volume 1 (Ninth ed.). Henry G. Allen and Company. p. 65.
- Richard Bangs and Pasquale Scaturro, Mystery of the Nile. New York: New American Library, 2005