African Rivers: Nile, Congo, and Niger

• Water resources in Africa are unevenly distributed, which can be a constraint on development.
• Rivers, lakes, wetlands, and underground water constitute the continent's freshwater resources.

Rivers

• Africa is home to many of the world's major rivers.
• The Nile, at 6,500km, is the world's longest river, draining the northeast of Africa.
• The Nile is formed by the White Nile from Lake Victoria joining with the Blue Nile from Lake Tana in Ethiopia, at Khartoum.
• The Nile flows north into the Mediterranean Sea through a delta in Egypt.
• The Congo River is 4,667km long, the 2nd longest in Africa and 5th in the world.
• The Congo drains much of central Africa, originating in Zambia and flowing north, west, and south to the Atlantic in the Democratic Republic of Congo.
• The Niger River is 4,180km long, the 3rd longest in Africa, with both a coastal delta in Nigeria and an inland delta in Mali.
• The Niger rises in the Fouta Djallon, flows north and east, then south to the Gulf of Guinea in Nigeria near Port Harcourt.
• The Zambezi is a major river in southern Africa, at 2,540km, with Victoria Falls.
• The Zambezi originates along the Zambia/Angola border and flows south and east to the Indian Ocean in Mozambique.

Natural Lakes

• Africa has some of the world's most prominent lakes.
• Lake Tanganyika is Africa's deepest lake (1,435m) and the world's second deepest, located within the rift valley.
• Lake Victoria is the largest natural lake in Africa with an area of 68,000 sq km, and third largest in the world.
• Lake Chad is extremely shallow and subject to significant seasonal changes in area.
• Lake Malawi and Lake Bosomtwi are also important lakes in Africa.

Man-Made Lakes

• The construction of large dams since the 1950s has created a new category of human-created lakes.
• Lake Volta (8,500 sq km), Lake Kariba (1,200 sq km), and Cabora Bassa are among the world's largest artificial lakes.
• Lakes provide benefits: fish, water for urban/industrial use and agricultural purposes.
• Lake Magadi in Kenya is a closed-basin, saline lake with large deposits of commercially mined sodium carbonate.

Formation of Lakes

• Faulting forms long, narrow, very deep lakes within rift valleys like Lakes Tanganyika and Malawi.
• Downwarping of the earth's surface from the weight of eroded material results in large, irregularly shaped, shallow lakes like Lake Chad and Lake Victoria.
• Volcanic craters can form small lakes in the East African highlands.
• Glaciers can deepen rock basins to form small lakes, especially on Mt. Kenya and Mt. Ruwenzori in East Africa.
• Damming rivers for hydroelectric power creates lakes, like Lakes Volta, Kariba and Nasser.

Wetlands

• Freshwater wetlands cover only 1% of Africa's area but are hydrologically, ecologically, and economically significant.
• Wetland subtypes include river floodplains, freshwater marshes, swamp forests, and peatlands.
• Freshwater marshes or swamps often occur by rivers and lakes, with dense papyrus growth and aquatic species.
• Wetlands are saturated by surface or underground water.
• Wetlands form either when water collects from flat land, or in areas with impermeable clay soils.
• Wetland vegetation is adapted for saturated soil, including papyrus reeds, sudd, lilies, and water hyacinth.
• Wetlands reduce downstream flood magnitudes by trapping and slowing inflowing water
• Wetlands help replenish underground water supplies by allowing increased water infiltration.
• Wetlands support diverse flora and fauna.

Swamps

• Two major swamps in Africa are the Sudd along the Nile in Sudan, and the Okavango Swamp in Botswana.
• Mangrove swamps occur along coasts with river estuaries.

Underground Water

• Africa's underground water resources connect to the bedrock geology.
• Ancient basement complex rocks or volcanic deposits have low groundwater capacity.
• Large sedimentary basins such as the Lake Chad Basin have high underground storage capacity.
• The Sahara Desert holds the largest reserves of underground water in sedimentary formations.
• Libya utilizes irrigation schemes to tap these sub-Saharan aquifers.

River Characteristics

• Rivers can undergo capture through headward erosion, facilitated by imperceptible watersheds.
• River capture examples include: The upper Niger becoming the lower Niger at Goa; Rocadas of the upper Cunene River of Angola becoming lower Cunene; and Black Volta becoming White Volta.
• Most rivers change color in the wet season due to sediments.
• Seasonal river flow varies, with some drying up completely.
• Rapids and waterfalls interrupt the course of rivers where they descend to coastal plains. Examples: River Congo: Livingstone and Stanley falls; Zambezi: Victoria falls; Nile: Owen falls, Palpawn-Boti falls.
• Trans-border rivers are rivers shared by two or more countries: Volta (Ghana, Burkina Faso, Cote d’Ivoire), Niger (Guinea, Mali, Nigeria), Zambezi (Zimbabwe, Zambia, Mozambique), Nile (Uganda, Ethiopia, Sudan, Egypt).

Human Exploitation of Water Resources

• Water provides domestic water supply for drinking, cooking, washing and is important for most industrial activities.
• Water cools engines and part of industrial products for breweries.
• Water transports people, agricultural and industrial goods, floats logs. Rivers used are Nile, Niger, Zaire, Zambezi, and Volta.
• Waterbodies provide a source of fish for communities, with fishing as an economic activity (Kisangani in Congo, Aswan in Egypt, and Yeji in Ghana).
• The FAO reported African inland waters produced 2,300,000 metric tons of fish in 2008 with Uganda being the largest producer at 450,000 metric tons, followed by Nigeria (304,300 metric tons), Tanzania (231,700 metric tons).

Importance of African Rivers (Cont.)

• Africa has ~40% of the world's hydroelectric power (HEP) potential.
• Dam construction sites are located where large rivers cut through axes of uplift or resistant rock, forming deep gorges, waterfalls, or rapids.
• Irrigation projects facilitate year-round agriculture.
  • Examples of irrigation projects: Aswan (Egypt), Gezira schemes (Sudan), Sanssanding (Mali), Kainji (Niger), Richard Toll scheme on R. Senegal, and the Tana River Development Scheme (Kenya).
• Gorges, rapids, waterfalls, deltas, and hydroelectric power (HEP) attract tourists, providing recreation.
  • Examples of sites for tourism: Victoria Falls (R. Zambezi) and Kabalega Falls (R. Nile).
• Black Volta (Ghana/Cote d’Ivoire), L. Tanganyika (Tanzania/DR Congo), L. Nyasa (Malawi/Mozambique/Tanzania), Orange (South Africa/Namibia), Zambezi (Zambia/Zimbabwe), and Pra (Ashanti/Central regions) all serve as administrative/political boundaries.

Dams in Africa

• Nkhula B. Hydro station - Shire River, Malawi
• Kariba - Zambezi River, Zambia/Zimbabwe
• Carbora Bassa - Zambezi River, Zimbabwe
• Kafue - Kafue River, Zambia
• Ruacana Falls - Cunene River, Angola
• Imboulou Dam - Lefini River, D.R. Congo
• Inga - Congo River, D.R. Congo
• Kainji - Niger River, Nigeria
• Akosombo - Volta River, Ghana
• Kossou - Bandama River, Cote d’Ivoire
• Pangani - Pangani River, Tanzania
• Seven Forks - Tana River, Kenya
• Owen Falls dam (Nalubaale) - White Nile River, Uganda
• Koka - Awash River, Ethiopia
• El Roseires - Blue Nile River, Sudan
• Grand Ethiopian Rennaisance Dam - Blue Nile River, Ethiopia
• Sennar Dam - Blue Nile River, Sudan
• Aswan High Dam - Nile River, Egypt
• Bui - Black Volta River, Ghana

Advantages of HEP Dams

• Water for irrigation (e.g. Aswan High Dam)
• Inland transportation
• Domestic and industrial water use
• Fishing
• Tourism and recreation
• Employment
• Cheap supply of HEP for domestic and industrial uses
• Revenue to government
• Control of floods downstream
• Development of new towns (e.g. Akosombo and Tema)

Disadvantages/Problems of Dams

• Displacement of people
• Silting of the lake created by the dam
• Flooding if the dam holds more water than its holding capacity permits
• High cost of construction and maintenance
• High salinity and growth of aquatic weeds
• Excessive evaporation
• Disruption of traditional ways of life
• Spread of water-borne diseases
• Submergence of large agricultural areas and forests

Limitations of African Rivers

• Physical Factors: Rapids and waterfalls interrupt river courses: The Nile between Khartoum and Aswan has six cataracts, the Congo has 32 rapids, e.g. Livingstone and Stanley falls on R. Zaire
• African rivers are short and narrow, with swift flow due to dry conditions and high evaporation rates.
• Sandbars/silting at river mouths results in shallow areas, making it difficult for large vessels and challenging the construction of harbors.
• Seasonal rivers overflow their banks, causing flooding and farmland destruction, and can dry up e.g. the Benue requires larger vessels to retreat downstream during dry seasons.
• Floating vegetation/marine weeds e.g. water hyacinth, are common.
• Winding courses of rivers e.g., Congo, Niger, Volta, and Senegal lead to longer and more difficult transportation.
• Shallow riverbeds result from rivers passing through sandy areas which causes sediment deposition in lower areas, meaning inhibited navigation.
• Insects and disease transmission breeding e.g., sleeping sickness (tse tse flies), river blindness (simulium fly/black fly), and malaria (mosquitoes): These are abundant in riverine communities.
• Human Factors include cultural myths/superstitions.
• Inadequate investment in irrigation, navigation, and HEP facilities.
• Political instability/civil wars
• Low technology
• Lack of international cooperation and agreements for river development/utilization.