The Remarkable History of Lake Kariba
As early as 1941, funds were allocated to conduct a survey of Kariba Gorge for a possible ground-breaking hydroelectric dam site on the Zambezi River.
Both Southern and Norther Rhodesia (Zimbabwe and Zambia as they are today) were in contention as it was theorised that the Kafue site in Northern Rhodesia was a better position to the one on the Zambezi. The question was solved by a board of experts who agreed that the dam should be built on the Zambezi River. In August 1955 the then Federal Government of Rhodesia and Nyasaland, called for tenders for the construction of the dam wall.
The contract for the construction of Kariba township was awarded to Richard Costain, and the main contract for the wall and transmission lines to the Italian consortium, Imprasit. The Kariba South Bank Power Station of the Kariba Dam hydroelectric scheme was officially opened by her Majesty, Queen Elizabeth the Queen Mother on 17th May, 1960.
The dam wall of Lake Kariba is located at the former Kriwa (Kariba) gorge, it is the largest man-made dam wall in the world, standing 128 m (420 ft) tall and 579 m (1,900 ft) long. It is a concrete double curvature arch dam, of mass concrete construction reinforced around the spillway gates.
Kariba was designed for the safe passage of a 10 000 year flood, based on river flow data available at the time. In the original design of the dam, the spillway had been designed for a 3-month flood of volume 68km3. During construction, in 1957, a peak flood occurred, the highest on record and created vast amounts of damage to the wall and the building equipment.
As a result, the dam engineers revised their spillway design to a 3-month flood of 74km3. In the following season, 1958, a peak flood was once again recorded. This led to further revision of the spillway design to it’s preset capacity of 92 km3.
Kariba’s rising waters put the lives of thousands of animals in danger. This prompted the most extensive and courageous rescue operation ever undertaken.
As the dam wall closed and the waters rose, milliards of large crickets, mice, rats, and the like emerged and scurried away from the encroaching waters. The skies above were blackened by swarms of birds sating themselves on the harvest. In the water the voracious tiger fish rampaged and, glutted with drowning insects, died. Many animals, notably the larger carnivores, retreated inland. Others, however, instinctively made for high ground to wait out another seasonal flood, and were trapped on temporary islands created by the unrelenting upsurge as Lake Kariba filled.
Senior ranger Rupert Fothergill, Brian Hughes (an ex-fireman who could not swim) and their assistants arrived. Under-manned and under-equipped, Operation Noah had begun.
They began by trying to manoeuvre the large animals into the water and sheaparding them to safety. In so doing, it was revealed that many mammals could swim long distances – waterbuck a full mile and baboon 400 yards, for instance. They also discovered that hornless female buck could paddle further than the males. And they observed instances of intelligent, adaptive behaviour such as waterbuck ferrying offspring on their backs and large horned bull antelope supporting their heads on logs, or testing them on others’ backs, during their journey to safety.
Others, declining the swim, were driven into the water for easier capture before being trussed and transported to shore. During this time tranquilliser darting techniques were pioneered.
This was a heroic period, when a handful of men drove themselves to the verge of collapse whilst their gains were pathetically small as thousands of animals drowned or died from shock or injuries sustained during the rescue operations.
Through the British Sunday Mail (February 15 1959) the story of Operation Noah fired the sentimental imagination of the world. Soon there were more feature writers, television cameramen, do-gooders, and inquisitive officials than there were designated rescuers and their intrusion severely hampered operations. A request for and nylon stockings to plait as replacements for the ropes which burnt captured animals, saw millions of pairs inundate the locals SPCA in another unstoppable flood.
Provoked by pressures of a press-fed public and humanitarian organisations, the task force was increased and better equipped by the Southern Rhodesia government. Overseas financial aid was refused, however, because of the danger of donors deeming it their right to intervene in the project. These funds were diverted to Northern Rhodesia (Now Zambia) and used to launch their participation in the rescue campaign.
Operation Noah, the largest animal rescue ever undertaken, saved over 5000 animals, including 50 black rhino between 1960 and 62. How many creatures died will never be known. Ironically, in the 12 years up till then, over 300 000 animals had been killed as part of the programme to control the spread of Tsetsi fly in Southern Rhodesia.