At first glance, Africa appears to be endowed with abundant water resources. It has big rivers, large lakes, vast wetlands, and limited but widespread groundwater. Much of this is located in the Central African sub-region and in the island countries.

Africa has 17 rivers with catchments areas greater than 100 000 kM2 ; and it has more than 160 lakes larger than 27 kM2, most of which are located around the equatorial region and the sub-humid East African Highlands within the Rift Valley. The continent has a huge potential for energy production through hydropower (1.4 million GWh per year). To exploit this, efforts are already under way to create regional power pools in Southern Africa (the Southern Africa Power Pool) and in Western Africa.

Disregarding temporal and spatial climate variability, Africa has abundant rainfall and relatively low levels of withdrawals of water for the three major uses of water - agriculture, community water supply and industry - which are estimated to be about 3.8% of total annual renewable water resources.

Rainfall in Africa

On a continental basis, rainfall in Africa is about 670 mm per year with greater variation in time and place. Temporal variability of rainfall is typically 40% around the mean -much higher than in temperate zones. At sub regional level, the spatial distribution of rainfall is varied. The highest rainfall occurs in the Island countries (1,700 mm per year), the Central African countries (1,430 mm), and the Gulf of Guinea (1,407 mm). The lowest precipitation occurs in the northern countries where average annual rainfall is only 71.4 mm.

Internal Renewable Resources.

A further significant feature of water resources in Africa is the extremely low runoff in relation to precipitation. Table 2 shows that the amounts of surface and ground water flows that are generated from rainfall within the subregions are low for all the subregions in Africa. At continental level, renewable water resources constitute only about 20 percent of total rainfall. In the Sudano-Sahelian and Southern African subregions, the figures are 5.9% and 9.25 respectively. This may reflect high losses of rainwater. These losses may occur, in part, through evaporation of surface waters or through plants. The low values of the internal renewable resources also show that there is room for improvement in conservation of rainwater. More importantly, they account, in pa art, for the endemic drought in parts of the continent.

The subregions are:

Northern: Algeria, Egypt, Libya, Morocco and Tunisia

Sudano-Sahelian: Burkina Faso, Cape Verde, Chad, Djibouti, Eritrea, Mali, Mauritania, Niger, Senegal, Somalia, and Sudan

Gulf of Guinea: Benin, Cote d’lvoire, Ghana, Guinea, Guinea Bissau, Liberia, Nigeria, Sierra-Leone, Togo

Central: Angola, Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, Sao Tome and Principe, Democratic Republic of Congo

Eastern: Burundi, Ethiopia, Kenya, Rwanda, Tanzania, and Uganda

Islands: Comoros, Madagascar, Mauritius, and Seychelles

Southern Africa: Botswana, Lesotho, Malawi, Namibia, South Africa, Swaziland, Zambia, and Zimbabwe

Withdrawals.

Of the total amount of water withdrawn, 85% is for use in agriculture, 9% is for community water supply and 6% is for industry. The withdrawals are rather low in relation to both rainfall and internal renewable resources. The only exception is in the northern countries where the withdrawals are 18.6% and 152.6% of rainfall and internal renewal resources respectively. It is noteworthy that for Africa, as a whole, the amount of water withdrawn for the three major uses of water amounts to only 3.8% of internal renewable resources. This may reflect a low level of development and use of water resources on the continent.

Groundwater in Africa.

Groundwater is extremely important in Africa. It is estimated that more than 75 percent of the African population uses groundwater as its main source of drinking water. This is particularly so in North African countries such as Libya and Tunisia, as well as parts of Algeria and Morocco, and in Southern African countries such as Botswana, Namibia and Zimbabwe.

However, groundwater accounts only for about 15 percent of the continent’s total renewable water resources. In South Africa, for example, groundwater accounts for just 9 percent. As a rule, significant groundwater resources tend to occur in small sedimentary aquifers along the major rivers and in the coastal deltas and plains. Limited groundwater resources, generally sufficient for local water supply, can also be found in the widely occurring crystalline (basement) rocks.

Courtesy: The Africa Water Vision for 2025: Equitable and Sustainable Use of Water for Socioeconomic Development