The Blue Nile is a river rising from Lake Tana in Ethiopia. It flows for around 1600 km before meeting with the White Nile at Khartoum in Sudan and forming the Nile. The Blue Nile is the source of the annual flood that enriches the soil of Egypt and which provided the fertility required to support the development of Ancient Egyptian civilisation. The Nile Flood was also central to Egyptian Mythology. The flood is caused by the overflowing of Lake Tana and the enrichment of the river by volcanic soils.
The Blue Nile is so-called because its water is visibly purer for most of the year than the grey-coloured water of the White Nile.