Akosombo Dam

Year:1965

Duration:4 years

Cost:$258m ($2.1bn today)

Country: Ghana

What did this project achieve?

The dam generates hydro-electricity and provides water for irrigating nearby farmland.

The Akosombo Dam – also known as the Volta Dam – is on the Volta River in south east Ghana.

At 124m tall and 660m long, the structure holds back the waters of Lake Volta – the largest man-made lake in the world by surface area.

The Lake Volta reservoir covers a third of Ghana’s land area – a total of 8,502km². With a capacity of 148km³, the 400km-long Lake Volta is also the third-largest artificial lake in the world by volume.

Akosombo is a rockfill dam. A rockfill dam is a structure built mainly of compacted rock and shaped like an embankment or hill.

The reservoir’s force hits the core of the embankment – from here it’s directed down and transferred to the dam’s foundations.

The structure was built between 1961 and 1965 and completed a month ahead of schedule.

Funded by the World Bank, the UK and the United States, the ambitious project has been called ‘the largest single investment in the economic development plans of Ghana’.

The scheme was designed to generate electricity for Ghana’s aluminium industry. Its original electrical output was 912MW, boosted to 1,020MW by modifications in 2006.

The project saw the flooding of part of the Volta River basin and its upstream fields. Around 80,000 people had to be relocated – about 1% of the population.

People from 700 different villages – many of whom were subsistence farmers - were moved into 52 resettlement villages as part of the scheme.

The dam is owned and run by the Volta River Authority, an agency of the government of Ghana.

Difference the project has made

The Akosombo Dam was politically important – it was seen as proof of Ghana’s ability to build major infrastructure projects.

Originally, the project supplied Ghana’s aluminium industry with the power it needed. Today the scheme provides 85% of the country’s electricity.

The project had some negative environmental effects - the Volta Lake is now a habitat for disease-carrying insects such as black flies and mosquitoes.

How the work was done

The Akosombo Dam was built by engineering firm Impregilo. The Italian company had just finished work on the Kariba Dam on the Zambezi river between Zambia and Zimbabwe.

The scheme comprised a main dam, a secondary dam, water intakes, a power station and two spillways. A spillway is a passage to let surplus water out of a dam.

Challenges the project team faced included the difficulties of excavating extremely hard ground in the area. As is often common when building rockfill dams, materials dug up – in this case quartzite, a kind of sandstone - were used to construct the scheme.

Other problems included the Volta itself – the river flooded in 1963, setting the project back three months as workers had to dredge stretches of the river bed again.

As well as generating electricity, engineers designed the scheme to provide water for irrigating nearby farmland.

A total of 28 workers died over the five years of the project’s construction – 12 were killed in an explosion on the site in 1966. There’s a memorial to all of them in the nearby St Barbara’s Catholic Church in the town of Akosombo.

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Akosombo is responsible for the largest artificial body of water in the world.

Salini Impregilio website

Fascinating facts

With a shoreline of 7,250km, Lake Volta is big enough to be seen from space.

More than 7.9m³ of construction materials were used to build the dam.

With over 80,000 people relocated, most of the population of the eastern region of Ghana was affected by the construction of the scheme.

People who made it happen

  • Client: Government of Ghana
  • Designer: William Halcrow and Partners
  • Contracting engineer: Italian engineering firm Impregilo (now Salini Impregilo)

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