Kariba Dam – A Brief History

17 May, 2015 - 00:05 0 Views

The Sunday Mail

The Zambezi River rises in north western Zambia and its catchment area covers 1 352 000 square kilometres and eight countries, namely Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia and Zimbabwe. It enters the Indian Ocean in Mozambique at Quelimane.

It flows for some 2 650 kilometres from its source to the Indian Ocean. It is the fourth largest river in Africa after the Congo, the Nile and the Niger and it is the largest river in Africa flowing into the Indian Ocean.

Kariba Dam is located approximately halfway down the Zambezi River.

The Electricity Supply Commission instigated an investigation for possible hydro-electric schemes to be situated at Kariba and in 1941 funds were allocated. As a result of this survey, a river gauging station was set up at Chirundu as well as at a campsite 25 kilometres downstream from the present dam wall.

Both Southern Rhodesia (Zimbabwe) and Northern Rhodesia (Zambia) were in contention as it was thought that the Kafue River Gorge site in Northern Rhodesia was preferable to Kariba. The matter was solved in 1951 by a board of experts known as “The Panel” who all agreed that the dam be built on the Zambezi River, at the Kariba Gorge site.

In August 1955, the then Federal Government of Rhodesia and Nyasaland (Zambia, Zimbabwe and Malawi) called for tenders for the construction of the dam wall. The contract for the construction of the wall and power station was awarded to Italian consortium Impresit on July 16 1956.

Kariba Dam was designed by the French engineer and inventor Andre Coyne. A specialist in “arch dams”, he personally designed over 55 dams, Kariba being one of them.

In September 1956, engineers started excavation of the foundations for the dam and powerhouse for the power station on the south bank. The power stations are some 152 metres below ground level. Over one million cubic metres of rock was excavated.

By December 1956, the north bank coffer dam and diversion tunnel were both completed. Block of the main dam containing four temporary openings were concreted inside this coffer dam. A suspension footbridge was also built downstream of the dam site.

In March 1958, there was an unprecedented flood amounting to about 16 000 cubic metres per second of water which passed through the site flooding the coffer dam causing considerable damage and disruption.

Parts of the suspension footbridge were swept away and the river in the gorge rose some 34 metres above the low water level. Kariba Dam was originally designed to have only four spillways. This flood called for a re-design and finally six gates were installed.

After this flood, construction of the dam progressed inside the main coffer dam and above the blocks built earlier in the north bank coffer dam. By December 1958, water began building up behind the dam wall as the diversion tunnel and temporary opening were blocked. For the first time in thousands of years, the free flow of the mighty Zambezi River ceased!

In December 1959, the first generator was commissioned and on May 17 1960, the Kariba Hydro Electric Scheme was officially opened. Kariba North Bank Power Station was commissioned in 1976.

Operation Noah

The construction of the then largest man-made dam in the world necessitated a spectacular wildlife rescue operation that captured headlines throughout the world. This is because the waters of the lake, which were rising behind the dam wall, were covering the land on which the animals were living. Almost 5 000 animals were rescued and released into the Mavuradonha National Park and Chete Safari Area.

Before Kariba Dam was built, the area around Kariba Gorge on both sides of the Zambezi River was home to the Tonga/Korekore people.

The water of the dam flooded the whole of the Zambezi Valley upstream of it and compelled the resettlement of 57 000 people on both sides of the river. Not only was there insufficient time to plan and implement a credible resettlement programme for these people, but insufficient resources were made available for the task.

About 22 000 people were resettled in Zimbabwe to sparsely watered and isolated areas. Nearly 35 000 were resettled in Zambia. — Courtesy of Kariba Dam, A Visitor’s Guide.

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