Describe the River Drainage of Africa

According to Colin Buckle (1979) and other authors, the drainage patterns of the
African Continent have been greatly affected by ‘basin and swell’ nature of Africa’s
surface with the accompaniment of Africa’s main rivers that reflect such an effect.
A number of these rivers such as River Nile are very old which were formed on
the African surface about 65 million years ago during the Eocene times.
Since then river Nile has undergone (or experienced) numerous changes even if it
has always flown to the north (Colin B. 1979).
It has been noted that during Pleistocene pluvial times the zone presently
occupied by the Swampy Sudd, around Juba-Khartoum area belonged to a vast Lake
which was known as Lake Sudd during those times.
Sources indicate that Lake Sudd drew its waters from ancestor rivers that formed
the present White and Blue Niles.
And eventually the White and Blue Niles over lopped the basin’s rim and started
flowing to the north, joining the Mediterranean sea passing through Sabaloka Gorge in
the north of Khartoum City.
Shore deposits show that some lakes might have been formed along the former
Nile course between Khartoum-Malakal zone.
This is evidenced by the present rivers, having some lake sediments which were
earlier deposited here.
Such ancient lakes in size and length were as large as the present lakes such as
Tanganyika, Malawi, etc.
Presently the rivers that dominate the entire northeastern section of Africa are the
tributaries of river Nile such as the Blue Nile, the Sobat, the Atbara.
As it is observed form the topographical map of Africa the above river Nile tributaries
mainly drain their waters from the lower northwest, eastern and southeastern slopes of the
Ethiopian Highlands. Some of them like Sobat and the Blue Nile, because of the
topographic nature of the eastern Ethiopian Highlands are characterized with series of
falls and rapids before they join the eastern low plains of the River Nile
According to Colin Blue (1979), the three rivers maintain tremendous erosive
power that is evidenced by large amounts of silt which have been deposited along the
lower and huge delta of the river Nile.
Africa has a number and famous rivers and it ranks among the world’s largest
rivers. But mainly it is drained by five major rivers, which have sources within the high
zones or highlands of Africa. They are:-
(1) River Congo,
(2) River Nile,
(3) River Niger,
(4) River Zambezi and
(5) River Orange.
Both in size and basins, these rivers are complex and they are longer than 1000km in
distance.
About 75% of African rivers drain in humid zones, where about ½ of Africa is
usually drained by the said five rivers.
Some rivers like the Nile and Niger drainage systems derive from the
amalgamation of several systems during the Cainozoic Era.
In contrast river Congo has a more well defined basin and compact.
River Zambezi and some of its tributaries for example pass through interior
swampy basins on the plains of High Africa before they descend to their large lowland
along the Coastal zone of the Western Sections of the Indian Ocean.
However, J.M. Pritchard (1979), indicated that the drainage systems of the
African Continent falls into three groups or categories in a ranking river categories
namely
I. Main drainage systems with rivers:
1. River Nile
2. River Congo
3. River Niger
4. River Zambezi
5. River Orange
II. Regional drainage systems:-
1. Maghreb region
2. Western region
3. West Equatorial region
4. Southwestern region
5. Southern region
6. Southeastern region
7. Eastern region
III. Basins of internal drainage systems:-
1. Lake Turkana
2. Okavango Basin
3. Lake Chad
IV. With no specific drainage systems:-
1. Sahara zone
2. Northeastern zone
Considering those (Category I) with sharp contrast to these complex continental
rivers which are spread over the interior large plains of Africa before they descend to
their respective oceans, also there are the short simple drainage basins of the continental
margins.
And this possibly what Colin Buckle (1979) categorised as ‘regional drainage
systems’.
Rivers belonging to this category maintain less than 650km long and the nature or
cause of these rivers are basically linear and at right angles towards the Coastline.
The African Continent drainage system also comprises numerous large and small
lakes, where some wide and deep like Tanganyika, Malawi, etc. some are shallow like
Chad, Victoria, etc.
Fairly, a number of African lakes in form and nature are associated with the Great
East African Rift System. Some lakes are human-made like; Nasser, Kariba, Volta,
Niger, etc.

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Titany answered the question on January 17, 2022 at 12:13