The Blue Nile is called so because of its relatively calm and clear waters (it appears "blue" from a distance) especially compared to its sister tributary, the "White" Nile, which is filled with rapids and waterfalls. The Blue Nile traverses wide, flat plains and so does not pick up the sediment, or the speed, of the White Nile.
Contrary to popular belief, the Blue Nile does not lay within the boundaries of modern-day Egypt and instead meets up with the White Nile at the city of Khartoum in Sudan. In the 19th century, however, Egypt and Britain exerted essentially joint control over Sudan and part of the Blue Nile fell under Egyptian control.
The source of the Blue Nile is Lake Tana, located in Ethiopia, and more than half of the Blue Nile's length is located in that country. Though there are actually many feeder streams, the Blue Nile's "sacred" source is a spring in a town near Lake Tana called Gish Abbai.
In Ethiopia (especially in the town of Gish Abbai and surrounding regions), the Blue Nile is called "Gish Abay" in reference to its source stream. In Arabic, its name is al-Nil al-Azraq.
As early as the 15th and 16th centuries, explorers such as the Spaniard Pedro Paez and the Portuguese Pero da Covilha have claimed to traced the origins of the Blue Nile. Officially, it was not until 2004 that the first full navigation of the Blue Nile from its origins to its termination was completed.
