There are controversies between Egypt and Ethiopia over dams..................look deeper.........there is all kinds of awful stuff going on................

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.^[3] 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.

There are numerous tributaries of the Abay between Lake Tana and the Sudanese border. Those on its left bank, in downstream order, include the Wanqa River, the Bashilo River, the Walaqa River, the Wanchet River, the Jamma River, the Muger River, the Guder River, the Agwel River, the Nedi River, the Didessa Riverand the Dabus River. Those on the right side, also in downstream order, include the Handassa, Tul, Abaya, Sade, Tammi, Cha, Shita, Suha, Muga, Gulla River,Temcha, Bachat, Katlan, Jiba, Chamoga, Weter and the Beles.^[3]

After flowing past Er Roseires inside Sudan, and receiving the Dinder on its right bank at Dinder, the Blue Nile joins the White Nile at Khartoum and, as the River Nile, flows through Egypt to the Mediterranean Sea at Alexandria. The Blue Nile is so-called because during flood times, the water current is so high that the river turns almost black (in the local Sudanese language, the word for black is also used for the colour blue).

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.