Inland Waters

General Characterictics of Rivers. African rivers are mainly rain-fed and overflow in the rainy season. In the wetter regions there is a thick network of rivers. It is here that the great rivers of Africa begin. In the arid regions, on the other hand, rivers are few. There are no permanent rivers in the Sahara, only dry stream beds — wadis. The occasional rain-storm fills these wadis with rush­ing torrents which, however, soon disappear in the sands. As they flow down the led­ges on the plateaus, they form numerous rapids and waterfalls that hinder navigation. Africa occupies one of the first places among the parts of the world in water-power ('white coal'). This energy, however,, remains almost unused.
Following the slope of the land, most African rivers emp­ty their waters into the Atlan­tic Ocean. Those flowing into the Indian Ocean are much fewer.   Vast   regions   in   the

Fig. 133. Africa:  Ocean drainage-basins and undrained areas

undrained,   as   their   waters   have   no   outlet    to   the    sea (Fig. 133).
Great African Rivers. The Nile, Africa's greatest river, is 6,500 kilometres long. Its source is in the mountains of East Africa. It flows through Lake Victoria and in its upper course forms a series of waterfalls. Upon reaching flat country it flows calmly through the vast marshes, dividing into several branches. Thickly interlaced marsh plants form floating islands (called 'sudds') that block the current and hinder navigation. Now called the White Ni1e, it is
soon joined by the B1ue Nile flowing from the Abyssinian Highlands.

Fig. 134. Flood-time in the Nile Valley.
On the higher places villages and roads can be seen. In the distance are the
pyramids — the  tombs  of  the  Pharaohs   (ancient kings of Egypt). Beyond
these stretches the desert.

After this it makes several crooks and forms numerous rapids, rushing swiftly on amidst the granite rocks. It is here only navigable in parts. In its lower course the Nile flows across desert land, receiv­ing not a single tributary. Much of its water evaporates in these arid regions. It falls into the Mediterranean Sea, forming a large delta called the Delta in reference to the Nile.
Owing to the tropical rains in its upper course, especially on the Abyssinian Highlands, the river rises, carrying great quantities of muddy water downstream. In its lower reaches, therefore, the Nile overflows towards the end of summer and beginning of autumn, despite the great heat and absence of rain (Fig. 134). It waters the fields leaving a great deal of rich silt on them.

has the largest volume of water of any river in Africa. It forms many waterfalls and rapids and is only partly navigable.
The great waters of the Niger flow into the Gulf of Guinea. Rising in the mountains near the Atlantic coast it first makes its way into the interior, then curves back to the ocean. This river has many rapids and waterfalls, too. At its estuary it forms a delta.
Of the rivers flowing into the Indian Ocean the Zambeziis the largest. It forms a great waterfall called the Victoria Fa11s. At this place the Zambezi is over 900 metres wide. It falls from a height of 120 metres into a narrow crevice that crosses the river's course. The roar is heard for dozens of

Fig 135. The Victoria Falls on the Zambezi River.

kilometres around, and the spray is hundreds of metres high. Reflected in the sun the drops of water sparkle and flash in beautiful changes of colour.
Lakes. The largest and deepest lakes are in the eastern part of Africa. There are many in the depressions of the Eastern Rift Valley. The deepest is Lake Tanganyika (1,435 metres), bordered by high and steep shores. It is second only to Lake Baikal in depth. Lake Tanganyika has an outlet to the Congo River.
The largest in area is Lake Victoria. Not very deep, it lies in a shallow depression on a plateau.
In the centre of Africa, south of the Sahara, lies Lake Chad, without an outlet but fresh watered all the same (probably due to an underground channel). It is not deep, but often changes its shape, becoming now smaller, now larger, depending on the amount of rain and the floods of the rivers falling into it.
Questions and Assignments.

• Trace the Nile and Congo basins on the outline map. Which
  is larger? Why are the waters of the Congo River always full?
• Point out the undrained areas of Africa on the physical map.
• Mark and name on the outline map the chief rivers and lakes
  of Africa.