Okavango Delta, Botswana
The Okavango Delta is created by the Okavango River, which is unusual in that it has no outlet to the sea.
Instead, it empties onto the sands of the Kalahari Desert in Botswana, irrigating 15,000 km², and thus creating the Okavango Delta (or Okavango Swamp). This is the world’s largest inland delta.
Each year some 11 cubic kilometres of water reach the delta and the nearby Moremi Wildlife Reserve. Some of this water reaches further south to create Lake Ngami.
The waters of the Okavango Delta are subject to seasonal flooding, which begins about mid-summer in the north and six months later in the south (May/June).
The water from the delta is evaporated relatively rapidly by the high temperatures, resulting in a cycle of cresting and dropping water in the south. Islands can disappear completely during the peak flood, then reappear at the end of the season.
The water entering the delta is unusually pure, due to the lack of agriculture and industry along the Okavango River.
It passes through the sand aquifers of the numerous delta islands and evaporates/transpirates by leaving enormous quantities of salt behind. These precipitation processes are so strong that the vegetation disappears in the center of the islands and thick salt crusts are formed.
In the image, we can see the delta during a period in which it appears green with vegetation and not much salt is visible. As there is little agriculture and industry along the river north of the delta, the water is not colored tan by runoff.