World Multipurpose River Projects

Lessons

Senior 6 · Geography

World Multipurpose River Projects

4 lessons

Lesson 3 of 4

Case Studies: the Aswan High Dam and the Akosombo Dam

45 min

Two dams, two African independence projects

In the 1950s and 1960s two newly independent African states each staked their future on one great dam. Egypt under Gamal Abdel Nasser built the Aswan High Dam on the Nile (1960–1970); Ghana under Kwame Nkrumah built the Akosombo Dam on the Volta (1961–1965). Compare them in Figure 1, then read each case study and decide which brought the better balance of benefits and costs.

Figure 1. Four African dams compared: the area flooded by each reservoir and the power each can generate. Drawn by Ganzaa.

Case study 1: the Aswan High Dam, Egypt

Feature	Facts
River and site	The Nile at Aswan, southern Egypt, on a hard granite outcrop at the First Cataract
Built	1960–1970, with Soviet loans, engineers and machinery after the United States, the United Kingdom and the World Bank withdrew their offers in 1956
Dam	An embankment dam 111 m high and 3,830 m long, 980 m wide at the base
Reservoir	Lake Nasser: about 500 km long (its southern part, in Sudan, is called Lake Nubia), 5,250 km², holding 132 km³
Power	12 turbines, 2,100 MW; in 1970 about half of Egypt's electricity

Aims: to end the yearly cycle of destructive floods and of droughts, to store water from wet years for dry ones, to extend irrigation, and to generate electricity.

Benefits

Flood and drought control. Egypt no longer depends on the size of each year's flood; stored water carried it through dry years in the Ethiopian highlands.
Irrigation. Even after about 10 km³ a year is lost to evaporation, the water available for irrigation rose by about 22 km³ a year. Perennial irrigation allows two or three crops a year, and new land was reclaimed from the desert.
Electricity for industry (fertiliser, steel, aluminium) and, for the first time, for most villages.
Navigation is easier with a steady flow, and Lake Nasser supports a new fishing industry.

Problems

Silt trapped in Lake Nasser. The fertile silt that once renewed the floodplain now settles in the lake, so farmers rely on chemical fertilisers.
Coastal and delta erosion because sediment no longer reaches the Mediterranean.
Fishing losses at sea. Egypt's Mediterranean catch fell from 35,000–40,000 tonnes a year to about 20,000 tonnes by 1971, as sardines that fed on silt-nourished plankton disappeared.
Waterlogging and salinisation of irrigated land, and the spread of bilharzia along permanent canals.
High evaporation from a large lake in a hot desert: estimates range from 10 to 16 km³ a year.
Displacement: 100,000 to 120,000 Nubian people in Egypt and Sudan were resettled, and their homeland was flooded. Twenty-two monuments, including the temples of Abu Simbel, were cut up and moved in a UNESCO campaign; other sites were lost under the lake.

Worked example 1: how much of Lake Nasser evaporates?

Problem. Lake Nasser holds 132 km³. Estimates of evaporation range from 10 to 16 km³ a year. What percentage of the lake's capacity is lost each year at each estimate?

Solution.

\frac{10}{132} \times 100 \approx 7.6\% \qquad \frac{16}{132} \times 100 \approx 12.1\%

Interpretation. Between about one thirteenth and one eighth of the lake's capacity evaporates every year. This is why the British hydrologist Harold Hurst had proposed storing Nile water further south, in Sudan and Ethiopia, where evaporation is lower, an argument Ethiopia uses today for the Grand Ethiopian Renaissance Dam.

Case study 2: the Akosombo Dam, Ghana

Feature	Facts
River and site	The Volta at Akosombo, in a gorge through the Akwapim hills in south-eastern Ghana
Built	1961–1965 by the Volta River Authority (VRA), financed by Ghana with loans from the World Bank, the United States and the United Kingdom, tied to an agreement to supply the Volta Aluminium Company (VALCO)
Dam	A rock-fill embankment dam 114 m high and 660 m long
Reservoir	Lake Volta: 8,502 km², about 3.6% of Ghana's area, holding 148 km³; the largest artificial lake in the world by surface area
Power	Six turbines of 170 MW: 912 MW at first, upgraded to 1,020 MW in 2006

Aims: mainly to supply cheap electricity to an aluminium smelter, the Volta Aluminium Company (VALCO) at Tema, and through it to industrialise Ghana; also to supply homes and neighbouring countries, and to develop fishing, transport and irrigation.

Benefits

Electricity for industry, cities and exports to Togo and Benin; a second dam downstream at Kpong (1982) reuses the same water.
Industry: the VALCO smelter and the new port and industrial town of Tema.
Lake transport: ferries and cargo boats carry goods and people along the lake between the south and the north of Ghana.
Fishing: Lake Volta became one of the country's main sources of freshwater fish.
Tourism and irrigation along the lake shore, and flood control on the lower Volta.

Problems

Displacement: about 80,000 people from 700 villages, 1% of Ghana's population, were moved into 52 new resettlement villages; many lost their way of life, and some villages later lost more than half their people.
Disease: bilharzia, river blindness and malaria increased around the lake, encouraged by weeds such as Ceratophyllum.
Dependence on rainfall: in drought years the lake falls and power must be rationed.
Drowned forest: tree stumps under the water endanger boats.
Coastal erosion downstream, notably around Keta, as less sediment reaches the sea.
Who benefits? For decades much of the power went to the smelter at a low price, while many rural Ghanaians, including resettled villages, had no electricity.

Worked example 2: land flooded for each megawatt

Problem. Using Figure 1, calculate the reservoir area per megawatt of capacity for Akosombo, Aswan and the Grand Ethiopian Renaissance Dam (GERD), and comment.

Solution.

\text{Akosombo} = \frac{8502}{1020} \approx 8.3\,\mathrm{km^2\,MW^{-1}} \qquad \text{Aswan} = \frac{5250}{2100} = 2.5\,\mathrm{km^2\,MW^{-1}} \qquad \text{GERD} = \frac{1875}{5150} \approx 0.36\,\mathrm{km^2\,MW^{-1}}

Interpretation. Lake Volta drowned more than 20 times as much land per megawatt as the GERD reservoir. The Volta basin behind Akosombo is low and flat, so the water held back by the dam spread out into a vast, shallow lake (mean depth $\frac{148\,\mathrm{km^3}}{8502\,\mathrm{km^2}} \approx 17\,\mathrm{m}$ ). A deep gorge in high country, like the GERD site, gives more power with less land lost, fewer people moved and less evaporation. The comparison is only partial: Aswan was built mainly for water storage and irrigation, not power.

Comparing the two

	Aswan High Dam	Akosombo Dam
Main purpose	Water storage, flood control and irrigation	Electricity for aluminium smelting
Climate of reservoir	Hot desert: very high evaporation	Humid tropics: high rainfall but variable
People resettled	100,000–120,000 Nubians	About 80,000
Key downstream effect	Loss of silt; delta erosion; fertiliser use	Coastal erosion around Keta
Main health problem	Bilharzia in permanent canals	Bilharzia, river blindness, malaria

Warning

Common mistakes

Confusing the Aswan Low Dam (1902) with the High Dam (1970). The High Dam, 6 km upstream, created Lake Nasser.
Calling Lake Volta the largest reservoir by volume. It is the largest by surface area; Lake Kariba holds more water.
Ignoring who benefits. A strong answer asks which groups gained and which paid the cost.

UNESCO and NHK: "Nubian Monuments from Abu Simbel to Philae". As you watch, note how the rising waters of Lake Nasser threatened the temples, and how the international campaign moved them; this is one of the social and cultural costs of the Aswan High Dam.

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Practice

State three aims of the Aswan High Dam.
Explain why Egyptian farmers began to use chemical fertilisers after the dam was built.
Explain two reasons why the Mediterranean sardine catch fell after 1970.
What was the main purpose of the Akosombo Dam, and which company was its main customer?
Calculate the mean depth of Lake Nasser from its volume (132 km³) and area (5,250 km²), and compare it with Lake Volta (about 17 m).
Describe three problems faced by people resettled for the Akosombo Dam.
"The Aswan High Dam has done Egypt more good than harm." Evaluate this view.

Show answersHide answers

Any three: control floods; store water for drought years; extend perennial irrigation; generate electricity; improve navigation.
The silt that once renewed the floodplain each year is now trapped in Lake Nasser, so soil fertility must be replaced with fertilisers.
Less silt and nutrients reach the sea, so the plankton on which sardines fed declined; the flow of fresh water into the sea also changed.
To supply cheap electricity for aluminium smelting; the Volta Aluminium Company (VALCO) at Tema.
132 km³ ÷ 5,250 km² ≈ 0.025 km ≈ 25 m; Lake Nasser is deeper on average than Lake Volta (17 m), but it lies in a hot desert where evaporation is far higher.
Any three: loss of farmland and traditional ways of life; poor land and housing in new villages; disease near the lake; poverty and out-migration; little or no electricity in the villages.
Good: flood and drought protection, 22 km³ more irrigation water a year, electricity, reclaimed land. Harm: loss of silt and fertility, delta erosion, salinisation, bilharzia, evaporation of 10–16 km³ a year, displacement of Nubians and loss of heritage. Judgement: most writers conclude that the benefits to Egypt's food and water security outweigh the costs, but that the costs fell unfairly on the Nubians and on the delta, and could have been reduced.

Summary

The Aswan High Dam (1970) gave Egypt control over the Nile: flood and drought protection, more irrigation and power, at the cost of lost silt, delta erosion, salinisation, disease, evaporation and the displacement of the Nubians.
The Akosombo Dam (1965) gave Ghana power, industry, lake transport and fish, at the cost of 80,000 people resettled, disease, drowned land and coastal erosion.
Comparing land flooded per megawatt shows why site choice matters.

Sources and credits

Aswan Dam, Akosombo Dam, Lake Volta and Lake Nasser: Wikipedia contributors, CC BY-SA 4.0, adapted by Ganzaa. Figures for both dams are taken from these articles and their cited sources, including the Volta River Authority.
Zambezi River Authority, Kariba HES technical data; European Space Agency, Lake Kariba image description (surface area); Webuild, GERD, 2025. Figures in Figure 1 cited.

Photos: Aswan High Dam panorama looking downstream (Visanu Euarchukiati, CC BY-SA 4.0) and Akosombo Dam from the Volta Hotel (SandisterTei, CC BY-SA 3.0), via Wikimedia Commons.

Video: "Nubian Monuments from Abu Simbel to Philae", UNESCO and NHK, embedded from YouTube.

Figure 1, the worked examples and the exercises were drawn and written by Ganzaa.

This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1Two dams, two African independence projects

2Case study 1: the Aswan High Dam, Egypt

3Case study 2: the Akosombo Dam, Ghana

4Comparing the two

Two dams, two African independence projects

Case study 1: the Aswan High Dam, Egypt

Case study 2: the Akosombo Dam, Ghana

Comparing the two