Fig. 1 The Sudanese Rift System Bahr El Arab Rift System, is nearly 12 kms deep at its central part. This rift is possibly still active, there are reported tectonic activity in its northern and southern boundaries. The Sudd swamps which forms the central part of the Basin is possibly still subsiding. The White Nile Rift System, although shallower than Bahr El Arab, it is about 9 km deep.The Blue Nile Rift System, geophysical exploration in this area estimated the depth of the sediments to be 5-9 kms.
Fig. 2 The Tertiary River Nile basins before the joining of the river system, showing the closed lake basins and river deltas in each rift system.
Map showing the alluvial fans of Gash and Atbara in the Atbara rift system; Soba and Gezira fans in the Blue Nile Rift system; Nuba and Adar in the White Nile rift; the Sudd in Bahr El Arab rift. ( K= Khor, R=River, W= Wadi).
The Evolution of the River Nile in Sudan
Ramsis Salama; ramsis@managedwater.org
There are two theories in relation to the age of an integrated Nile. The first one is that the integrated drainage of the Nile is of young age, that the Nile basin was formerly broken into series of separate basins, only the most northerly (the Proto Nile basin) feeding a river following the present course of the Nile in Egypt and in the far north of the Sudan (De Heinzelin, 1968; Butzer and Hansen, 1968; Wendorf and Schild 1976; and Said, 1981). Said (1981) stress the fact that Egypt itself supplied most of the waters of the Nile during the early part of its history. The other theory is that the drainage from Ethiopia via rivers equivalent to the Blue Nile and the Atbara/ Takazze flowed to the Mediterranean via the Egyptian Nile since well back into Tertiary times.
Since then, the discovery of the Intercontinental Rift System (Salama, 1997), with massive amounts of continental sediments supported the first hypothesis that the River Nile in Sudan was during the Tertiary a series of separate closed basins, each basin occupying one of the major Sudanese Rift System (Salama, 1987). These basins were not interconnected except after their subsidence ceased and the rate of sediment deposition was enough to fill up the basins to such a level that would allow connection to take place. The filling up of the depressions led to the connection of the Egyptian Nile with the Sudanese Nile, which captures the Ethiopian and Equatorial head waters during the latest stages of tectonic activities of Eastern, Central and Sudanese Rift Systems (Salama, 1997).The connection of the different Niles occurred during the cyclic wet periods. The River Atbara overflowed its closed basin during the wet periods which occurred about 100 000 to 120 000 yrs B.P. The Blue Nile was connected to the main Nile during the 70 000 – 80 000 yrs B.P. wet period. The White Nile system in Bahr El Arab and White Nile Rifts remained a closed lake until the connection of the Victoria Nile some 12 500 yrs B.P..
Supporting evidence for these periods comes from isotope data collected along the White Nile and the Blue Nile near Khartoum. The results showed that recharge water infiltrated from the Nile under the present prevailing arid climate and extends 12 – 17 km only away from the Niles (Farah, 1999), while groundwater away from the Nile is from meteoric origin and has been recharged during more humid wetter periods. All this indicates the River Nile in Sudan is a recent phenomenon.
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