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Africa’s grand anomaly

Africa’s grand anomaly

Africa’s grand anomaly

In the middle of the Kalahari - one of the earth’s famed deserts - lies a vast oasis of such grandeur that it would have Bedouins palpitating with excitement. We are not talking of a puddle of water with a few desultory palm trees that causes feverish ecstasy among the Saharan wanderers, but of a vast inland delta filled with innumerable islands, countless palms and water enough for every camel ever born.

From the air the Okavango Delta is a verdant paradise of shimmering blue waterways and copious life of inconceivable variety. Yet, not far from the myriad streams, you are aware of the infinite grey-brown and inhospitable land that stretches away to a distant, featureless horizon.

It’s because of a series of natural coincidences that the sparkling waterways of the Okavango Delta exist. Nearly half a million tons of salts are swept annually from the Angolan highlands, propelled by the 18 billion litres of water that the Kavango River carries along its 1,600km course. The flood is then trapped between two fault lines and evaporated by the fierce sun, or transpirated by the plants, leaving the minerals behind.

These salts should have reduced the Okavango to a lifeless wasteland, making the Dead Sea look positively lively by comparison, yet the Delta’s waterways are beguilingly sweet. This wonder is achieved through the employ of hundreds of thousands of sophisticated pumps, which we call trees. They extract the salts from the water and then deposit them in concentrated piles in the centre of the islands.

Trees, nature’s miracle workers, are extremely complex and vulnerable organisms in which life abides in only three delicate layers of cells that are to be found just beneath the bark. They form a wet sleeve around the lifeless heartwood and, micron by micron, they raise as much as a thousand litres of liquid daily from the ground via the roots and hoist it to the leaves from where much of it escapes into the atmosphere.

The salts in the meanwhile gather in white mounds in the middle of the islands and were it not for an ingenious system that rids the Delta of the ever-accumulating minerals, they would overwhelm the trees that created them within 150 years, leading ultimately to the destruction of the Okavango basin. With exquisite timing that spans much the same period, the major rivers and channels - which have over the years been raised above the general ground level by a peat build-up along their banks – burst through their elevated sides and alter direction, leaving behind vast areas to dry out. 

The salts are also left behind and are gradually leeched into the soils by the rains, while the peat slowly dehydrates and becomes buried under new vegetation. In time, lightning strikes will start a peat fire that will smoulder underground for decades at a stretch, consuming the salts. All the while, in some other part of the Delta, the process is starting afresh.

Read more articles from this issue:
Zambezi Traveller (Issue 13, June 2013)

Read more about the region in our destination guide:

Other articles in this series:
Paradise unveiled
A short history of the Falls
The sacred hills of the Matopos
The smoke that thunders
Valley of abundance
Superlative and unexplored
The great enigmas
Africa’s grand anomaly
The Middle Zambezi
The Zambezi’s final triumph