Last updated on November 27th, 2022
In the Zambezi Valley, the locals feared the river god Nyami Nyami. This serpent-like creature devours people and leaves a bloody trail in the water. Western colonists attempted to tame the river and its god by building the Kariba Dam. The construction suffered multiple setbacks due to natural disasters but work continued despite heavy losses. It stood as the tallest dam wall in the world upon completion in 1959. Others have since surpassed the record, but it remains a source of pride for the African continent. Here are 50 interesting facts about the Kariba Dam.
The Kariba Dam at a Glance
1. What’s in a Name?
The river god lives under a rock near the dam. Locals avoided the place, fearing that a whirlpool might suck them in. They called it a trap, or “Kariba” in the local language. Now, the dam traps the water with its high wall.
2. Claim to Fame
The Kariba Dam is known for its massive reservoir. The artificial lake is the largest in the world by volume. With 180 cubic kilometers of water, it is almost five times bigger than the Three Gorges Reservoir.
3. Annual Output
The dam is among the most productive power plants in Africa. Its average annual generation is pegged at 6,400 gigawatt-hours, providing cheap energy for the region.
4. Project Timeline
Engineers estimated a four-year construction period. Despite unforeseen challenges, they finished the structure six months ahead of schedule. Onsite work ran from 1955 to 1959.
5. Dam Type
Kariba is an arch dam, which is similar to the Hoover Dam. Both have a concrete wall that curves upstream for increased strength against water pressure. The sides lean against solid rock walls for support.
6. Construction Cost
It is one of the most ambitious projects in Africa. The first stage cost $135 million, covering only the south power cavern. Adjusting for inflation, it would cost over $1.2 billion today.
7. Dam Dimensions
The Kariba Dam is an impressive structure. Its height of 128 meters is equivalent to a building with 43 floors. It is 579 meters long, with a base of 24 meters and a thin crest of 13 meters.
8. The Reservoir
Lake Kariba began to fill up with water in 1958. The process took five years, with the artificial lake stretching 280 kilometers long, 40 kilometers wide, and 97 meters deep.
9. The Spillway
The Zambezi River can overwhelm the dam during heavy storms. Operators open six sluice gates on the wall, directly releasing water to the plunge pool and letting gravity move it downstream.
10. The Power Station
The Kariba Dam has dual power stations. On the north side, you will see four 150 MW and two 180 MW turbines. On the south side, you will find six 125 MW and two 150 MW turbines. The total installed capacity is 1,626 MW.
The History of the Kariba Dam
11. A Colonial Plan
Africa was different in the 1950s. Back then, parts of Malawi, Zambia, and Zimbabwe formed a colony of the British Empire called the Federation of Rhodesia and Nyasaland. Their need for energy led to a dam construction plan.
12. The Original Site
The Kariba Gorge was not the original location. The initial plan was to build a smaller and cheaper dam on the Kafue River of Northern Rhodesia, close to the Copperbelt mines that required more power.
13. The Big Switch
Southern Rhodesia, the most affluent part of the colony, did not like the Kafue plan. It was too far and too small for them. Officials insisted on building at the Kariba site for greater accessibility and higher power generation.
14. Dam Designer
The Kariba Dam is a French design. The engineering firm Coyne et Bellier specializes in dams, tunnels, nuclear plants, and hydroelectric power plants. Their other projects include the Tignes Dam in France, the Bin el Ouidane Dam in Morocco, and the Daniel-Johnson Dam in Canada.
15. First Contractor
The project drew 74 bids from around the world. The winner was Impresit, a joint venture of four Italian companies. After the Kariba Dam, it completed other engineering projects in Iran, Ghana, Pakistan, and India. It was also involved in the Panama Canal expansion.
16. Kariba Town
Workers had to live near Lake Kariba throughout the construction period. The British contractor Costain built their residences. Today, the site is a modern resort town drawing tourists with its impressive views.
17. The 1958 Flood
In the spring of 1958, nature reminded everyone of its power. The worst flood in living memory swept through the construction site, destroyed the facilities, and delayed the project’s completion.
18. Restarting the Operation
All storms pass. After the initial shock, the workers came together to rebuild the site from scratch. They replaced sections of the cofferdam, pumped out the water, and continued the operation.
19. Opening Ceremonies
Proud of their achievement, the African colony invited a special guest to the official opening ceremony: the Queen Mother herself, Queen Elizabeth II. She had a parade on May 17, 1960, and went on to inspect the new dam.
20. Second Contractor
It is not over yet. The second phase involved the construction of the north power cavern. The British engineering firm Mitchell Construction won the bid and completed the project in 1977. The total cost ballooned to $480 million.
Challenges and Solutions
21. A Dam in the Wild
It is hard to build in the middle of nowhere. Can you imagine the logistics? That is why the designers proposed a concrete arch dam. It uses fewer materials without compromising strength – a practical choice in the remote Kariba Gorge.
22. Building Roads and Bridges
There were not even any roads leading to the dam site. Vehicles had to follow elephant paths across the rugged terrain. Eventually, they built roads and bridges to facilitate transport from the main highway and railways.
23. Number of Workers
Nothing compared to its scale in the 1950s. This gigantic dam required a large labor force, including foreign and local workers. For four years, they lived in a housing facility that could accommodate 7,000 people.
24. Landing Strip
The Italian team flew in through multiple flights. Workers built a landing strip for faster transport and emergencies. After the dam construction, the locals built an airport around it and turned it into a busy transport hub.
25. Diversion Tunnels
Water had to move away from the construction site. The men dug large diversion tunnels on the sides of the river. Later, these tunnels became the outlets for water flowing through the turbines in the hydroelectric plants.
26. Crushing Rocks
Concrete needs three ingredients: cement, sand, and aggregate. They improvised for the last one, getting rocks from nearby caves and crushing them into various sizes to reduce dependence on off-site materials.
27. Grading Sand
Sand came from the riverbed. Truckloads went into conveyor belts with washing and screening stations, dividing the material into three different grades before sending them to the appropriate bins.
28. Storing Cement Onsite
Cement was a different story. It had to come from 400 miles away, delivered via rail before getting on trucks to the construction site. Large metal silos kept out moisture. The site storage capacity was 24,000 tons.
29. Mixing Concrete
It was fast or bust. Workers had to move fast when pouring concrete because of the tremendous volume requirements. They built concrete mixing plants onsite. These churned out 80,000 cubic meters a month.
30. Buckets on Cables
Aerial cables boosted productivity. They did not have to carry the concrete down to the dam. They suspended large buckets on a pulley system and let these slide to their destinations. Gravity did all the work.
31. Doubts Emerge
What would happen if the dam collapsed? Fears increased as Kariba aged. In 2010, opening the floodgates led to the evacuation of 130,000 people. Heavier rain could have worse results.
32. Foundation Question
How long can the dam hold? In 2014, engineers said that torrential waters from the spillway dug a crater in front of the wall called a plunge pool. Without immediate repairs, it will weaken the foundation and damage the structure.
33. Widespread Damage
A Kariba collapse would be devastating. It could send a wall of water as far as Mozambique, overwhelming its dams and knocking out 40% of the hydroelectric capacity in southern Africa. About 3.5 million people are also at risk.
34. Proactive Disaster Prevention
Prevention is better than cure. The Kariba Dam Rehabilitation Project began in 2017 with two goals: reshape the plunge pool and refurbish the dam spillway – all while having minimal effect on power generation.
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