Ethiopia’s Blue Nile delivers most of Egypt’s floodwater
The Blue Nile rises at Lake Tana in Ethiopia and runs roughly 1,450 kilometres through Ethiopia and Sudan before meeting the White Nile at Khartoum. In the rains it can supply about 85.6 percent of the Nile’s water, swamping the longer White Nile’s contribution when farmers need flood silt most.
The river starts at Gish Abay near Sekela, where Ethiopians call it the Abay, and flows out of Lake Tana. Its official length is 1,450 kilometres, 800 of them in Ethiopia, but estimates range from 1,460 to 1,600 kilometres, partly because the river runs through nearly impassable gorges cut some 1,500 metres into the Ethiopian Highlands. About 30 kilometres below the lake it plunges over the Blue Nile Falls, known in Amharic as Tis Abay, great smoke, one of the country's top attractions, and enters a canyon roughly 400 kilometres long that has long hindered travel between north and south Ethiopia. A British team that made the first descent from Lake Tana in 1968 called it the Grand Canyon, and later rafters added of the Nile.
Looping across north-west Ethiopia, it gathers dozens of tributaries, including the Didessa and Dabus on the left bank and the Beles on the right. In Sudan it runs about 650 kilometres past Er Roseires, picks up the Dinder, and at Khartoum merges with the White Nile to form the Nile proper, which carries on through Egypt to the Mediterranean.
Its power is seasonal. From June to September it supplies 80 to 86 percent of the Nile's water, and in the summer monsoon it tears fertile soil from the highlands, turning dark brown or nearly black with silt. Those floods built the fertility of the Nile Valley and so helped give rise to ancient Egypt and its myths, until the Aswan Dam, finished in 1970, ended them in lower Egypt.
It remains Egypt's lifeline: although shorter than the White Nile, it provides about 59 percent of the water reaching Egypt and over 85 percent of the Nile's overall flow. Sudan leans on it too. The Roseires and Sennar dams help supply the 80 percent of the country's power that comes from hydroelectricity, and they irrigate the Gezira Scheme, renowned for high-grade cotton and also growing wheat and fodder.
Source: Blue Nile
