ATBARA RIVER. The last tributary of the Nile is the At bara, which joins it 4okm. upstream of Berber, after a total course of about 1,266 kilometres. It rises as the Takazze in the Lasta hills, close to the eastern escarpment of Abyssinia, and rapidly deepens its valley into a steep-sided ravine deeply cut into the basalt plateau until only 16km. from its source it is flowing in a ravine 600 metres deep; at some 5okm. E. of the mountains of Debra Tabor it turns northwards, being joined by numerous tribu taries, some of which are large streams carrying a considerable volume in the rainy season. In about lat. 13° 12' N., where the road from Adua to Gondar crosses it, the Takazze turns westwards, and under the name of Settit, joins the Atbara river coming from the south-east to form the main stream of the Atbara at a point 5o2km. from the Nile.
Like most of the rivers of Abyssinia, the Takazze is in flood in July and August, being fed by the summer rains of the Abyssinian plateau, but after October it falls rapidly, and from November to May the Takazze is of small depth, while the Atbara sinks to a number of separate pools which afford watering places for the Arabs.
The Takazze begins to rise with the early rains of Abyssinia in May, and early in June the middle reaches of the river are affected. Here at this time, owing to the deficient supply, the permanent water-surface is at most points below the surface of the river bed, except in the deep pools, but as the upper river rises, water flows down and raises this water surface till running water appears again in the bed of the river. The Atbara is often described as being tor rential in character, but this is more true of its tributaries in the upper reaches than of the river itself. Its slope is not excessively high, and when it has risen in flood it flows steadily, the sudden rises and falls which occur being due to its tributaries rising on the Abyssinian tableland, fed by the heavy rains of July and August.
The Atbara flood commences in July, when the average dis charge does not exceed 70o cubic metres per second ; in August it increases to 2,15o cubic metres per second and falls to about ',Igo cubic metres per second in September; afterwards the river falls rapidly.
The silt brought down to the Nile from Abyssinia by the Atbara during the annual flood may amount to from io to 15 million, metric tons.