Kariba Dam

Kariba Dam
The dam as seen from Zimbabwe
Location	Zambia Zimbabwe
Coordinates	16°31′23.5″S 28°45′41.55″E / 16.523194°S 28.7615417°E / -16.523194; 28.7615417Coordinates: 16°31′23.5″S 28°45′41.55″E / 16.523194°S 28.7615417°E / -16.523194; 28.7615417
Construction began	1955
Opening date	1959
Construction cost	US$480 million
Owner(s)	Zambezi River Authority
Dam and spillways
Type of dam	Arch dam
Impounds	Zambezi River
Height	128 m (420 ft)
Length	579 m (1,900 ft)
Reservoir
Creates	Lake Kariba
Total capacity	180 km3 (150,000,000 acre·ft)
Catchment area	663,000 km2 (256,000 sq mi)
Surface area	5,400 km2 (2,100 sq mi)
Maximum length	280 km (170 mi)
Maximum water depth	97 m (318 ft)
Power station
Turbines	North: 4 x 150 MW (200,000 hp), 2 x 180 MW (240,000 hp) Francis-type South: 6 x 111 MW (149,000 hp) Francis-type
Installed capacity	North: 960 MW South: 666 MW Total: 1,626 MW (2,181,000 hp)
Annual generation	6,400 GWh (23,000 TJ)

The Kariba Dam is a double curvature concrete arch dam in the Kariba Gorge of the Zambezi river basin between Zambia and Zimbabwe. The dam stands 128 metres (420 ft) tall and 579 metres (1,900 ft) long.^[1] The dam forms Lake Kariba which extends for 280 kilometres (170 mi) and holds 185 cubic kilometres (150,000,000 acre·ft) of water.

Construction

The double curvature concrete arch dam was designed by Coyne et Bellier and constructed between 1955 and 1959 by Impresit of Italy^[2] at a cost of $135,000,000 for the first stage with only the Kariba South power cavern. Final construction and the addition of the Kariba North Power cavern by Mitchell Construction^[3] was not completed until 1977 due to largely political problems for a total cost of $480,000,000. During construction, 86 men lost their lives.^[2][4]

Power generation

The Kariba Dam supplies 1,626 megawatts (2,181,000 hp) of electricity to parts of both Zambia (the Copperbelt) and Zimbabwe and generates 6,400 gigawatt-hours (23,000 TJ) per annum. Each country has its own power station on the north and south bank of the dam respectively. The south station belonging to Zimbabwe has been in operation since 1960 and has six generators of 111 megawatts (149,000 hp) capacity each for a total of 666 megawatts (893,000 hp).^[5][6]

On November 11, 2013 It was announced by Zimbabwe's Finance Minister, Patrick Chinamasa that capacity at the Zimbabwean (South) Kariba hydropower station would be increased by 300 megawatts. The cost of upgrading the facility has been supported by a $319m loan from China. The deal is a clear example of Zimbabwe's "Look East" policy which was adopted after falling out with Western powers.^[7] Construction on the Kariba South expansion began in mid-2014 and is expect to be complete in 2019.^[8]

The north station belonging to Zambia has been in operation since 1976, and has four generators of 150 megawatts (200,000 hp) each for a total of 600 megawatts (800,000 hp); work to expand this capacity by an additional 360 megawatts (480,000 hp) to 960 megawatts (1,290,000 hp) was completed in December 2013. Two additional 180 MW generators were added.^[9][10][11]

Location

The Kariba Dam project was planned by the government of the Federation of Rhodesia and Nyasaland, or Central African Federation (CAF). The CAF was a semi-independent state within the Commonwealth in southern Africa that existed from 1953 to the end of 1963, comprising the former self-governing British colonies of Northern Rhodesia and Southern Rhodesia and the former British protectorate of Nyasaland. Northern Rhodesia had decided earlier in 1953 (before the Federation was founded) to build a dam within its territory, on the Kafue River, a major tributary of the Zambezi. It would have been closer to Zambia's Copperbelt which was in need of more power. This would have been a cheaper and less grandiose project, with a smaller environmental impact. Southern Rhodesia, the richest of the three, objected to a Kafue dam and insisted that the dam be sited instead at Kariba. Also, the capacity of the Kafue dam was much lower than that at Kariba.^[12] Initially the dam was managed and maintained by the Central African Power Corporation.^[13] The Kariba Dam is now owned and operated by the Zambezi River Authority,^[14] which is jointly and equally owned by Zimbabwe and Zambia.^[15]

Since Zambia's independence, two dams have been built on the Kafue River: the Kafue Gorge Dam and the Itezhi-Tezhi Dam.

Environmental impacts

Population displacement and resettlement

The dam under construction in the 1950s, showing the dangers faced by the workers.

The creation of the reservoir forced resettlement of about 57,000 Tonga people living along the Zambezi in both Northern Rhodesia and Southern Rhodesia.^[16] From "The Shadow of The Dam", a first-hand account written by David Howarth in the 1960s, referring to the situation in Northern Rhodesia:- "Everything that a government can do on a meagre budget is being done. Demonstration gardens have been planted, to try to teach the Tonga more sensible methods of agriculture, and to try to find cash crops which they can grow. The hilly land has been plowed in ridge contours to guard against erosion. In Sinazongwe, an irrigated garden has grown a prodigious crop of pawpaws, bananas, oranges, lemons, and vegetables, and shown that the remains of the valley could be made prolific if only money could be found for irrigation. Cooperative markets have been organized, and Tonga are being taught to run them. Enterprising Tonga have been given loans to set themselves up as farmers. More schools have been built than the Tonga ever had before, and most of the Tonga are now within reach of dispensaries and hospitals."^[17]

There are many different perspectives on how much resettlement aid was given to the displaced tribe. According to anthropologist Thayer Scudder, who has studied these communities since the late 1950s, "Today, most are still 'development refugees.' Many live in less-productive, problem-prone areas, some of which have been so seriously degraded within the last generation that they resemble lands on the edge of the Sahara Desert."^[18]

A 2005 book, "Deep Water" by Jacques Leslie focused on the plight of the people resettled by the dam, and found the situation little changed. Kariba remains the worst dam-resettlement disaster in African history.^[19]

Over 6000 large animals threatened by the rising water were rescued by Operation Noah.

Basilwizi Trust

The dam as seen from Zimbabwe

In a quest to restore their lives and find justice, the Tonga formed their own advocacy group in 2000, the Basilwizi Trust.^[20]

River ecology

The Kariba Dam controls 90% of the total runoff of the Zambezi River, thus changing the downstream ecology dramatically.

Wildlife rescue

From 1958 to 1961, 'Operation Noah' captured and removed around 6,000 large animals and numerous small ones threatened by the lake's rising waters.

Recent activity

On the 6th of February 2008, the BBC reported that heavy rain might lead to a release of water from the dam, which would force 50,000 people downstream to evacuate.^[21] Rising levels led to the opening of the floodgates in March 2010, requiring the evacuation of 130,000 people who lived in the floodplain, and causing concerns that flooding may spread to nearby areas.^[22]

In March 2014 at a Zambezi River Authority organized conference, engineers warned that the foundations of the dam had weakened and there was a possibility of dam failure unless repairs were made.^[23]

On 3 October 2014 the BBC reported that “The Kariba Dam is in a dangerous state. Opened in 1959, it was built on a seemingly solid bed of basalt. But, in the past 50 years, the torrents from the spillway have eroded that bedrock, carving a vast crater that has undercut the dam's foundations. … engineers are now warning that without urgent repairs, the whole dam will collapse. If that happened, a tsunami-like wall of water would rip through the Zambezi valley, reaching the Mozambique border within eight hours. The torrent would overwhelm Mozambique's Cahora Bassa Dam and knock out 40% of southern Africa's hydroelectric capacity. Along with the devastation of wildlife in the valley, the Zambezi River Authority estimates that the lives of 3.5 million people are at risk.”^[24]

In January 2016 it was reported that water levels at the dam had dropped to 12% of capacity. Levels fell by 5.58 metres (18.3 ft), which is just 1.75 metres (5 ft 9 in) above the minimum operating level for hydropower. Low rainfalls and overuse of the water by the power plants have left the reservoir near empty, raising the prospect that both Zimbabwe and Zambia will face water shortages.^[25]

See also

• Cahora Bassa Dam
• Nyami Nyami
• List of largest power stations in the world
• List of crossings of the Zambezi River

References

External links

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