International Hydrological Programme
Africa
The African continent occupies an area of 30.1 million km2 spanning the equator. It has a rapidly growing population of well over 700 million, many living in some of the world’s least developed countries.
The hydrological network is the world’s least developed with sparse coverage and short fragmentary records, except for the Nile Basin and in certain countries in the north and south of the continent.
Most of Africa is composed of hard Precambrian rocks forming a platform with some mountainous areas, mainly on the fringes of the continent and where the rift valley crosses east Africa.
The climate is much more varied than the relief with the hottest of deserts and the most humid of jungles – the amount and distribution of precipitation in space and time being paramount. Annual totals vary from 20 mm a year over much of the vastness of the Sahara to 5,000 mm towards the mouth of the Niger.
With large amounts of solar radiation and high temperatures, African evaporation rates are high. The deserts that cover about one third of the continent in the north and south have little surface water but large volumes of groundwater.
The Congo (central Africa) is the world’s second largest river and the Nile the longest (6,670 km), but the Orange (South Africa), Zambesi (southern Africa), Niger and Senegal (West Africa) rivers are also important. The average annual flow from Africa for the 1921–1985 period was about 4,000 km3. Many of the rivers have a considerable hydropower potential that is already exploited by certain dams and power. These schemes have aided development but some have serious hydroecological and social effects. Parts of the large areas under irrigation suffer from high water tables and increased salinity.
Water problems are most acute in Africa, where it is estimated that 300 million people are affected by water shortages. Adequate management of its water resources is crucial for the future of the African continent.
