Major Rivers
The Blue Nile River
Blue Nile makes about 80% by volume of the Great Nile River. The Blue Nile from Ethiopia originating form Lake Tana and the White Nile that originated form Lake Victoria merge into the Great Nile River at Khartoum, the Sudan capital to form the longest river of the world draining to the Mediterranean Sea.The Blue Nile Falls is one of the most popular tourist destination sites along the historic route. The Blue Nile Falls is situated near Tis-Abay town, 30 kms to the east of Bahir Dar, which is 20-30 minutes walk from the little town of Tiss Abey.
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.
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 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.
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, situated 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.