Abbay River

Blue Nile
Blue Nile Falls (Tis Issat) at Lake Tana
Country	Ethiopia
Basin features
Main source	Lesser Abay/Lake Tana
River mouth	Confluence with White Nile in Khartoum, Sudan, forming main branch of Nile River
Basin size	325,000 km2 (125,000 sq mi)
Physical characteristics
Length	1,450 km (900 mi)
Discharge	Average rate: 1,548 m3/s (54,700 cu ft/s)

The Blue Nile (Amharic: ዓባይ^?; transliterated: ʿAbbay but pronounced Abbai, Arabic: النيل الأزرق‎‎ an-Nīl al-Azraq) is a river originating at Lake Tana in Ethiopia. With the White Nile, the river becomes one of the two major tributaries of the Nile. The upper course of the river is called the Abbay in Ethiopia, where many regard it as holy. Some Ethiopians have long identified the Blue Nile as the River Gihon mentioned as flowing out of the Garden of Eden, in Genesis 2 and "encircling the entire land of Cush".

The Blue Nile is so-called because floods during the summer monsoon erode a vast amount of fertile soil from the Ethiopian Highlands and carry it downstream as silt, turning the water dark brown or almost black. In the local Sudanese language, the word for black is also used for the colour blue.

The distance of the river from its source to its confluence has been variously reported as being between 1,460 kilometres (910 mi) and 1,600 kilometres (990 mi). This uncertainty over the length might partially result from the fact that the river flows through a series of 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.