By Leigh Kemp
The Okavango Delta is the remnant of an ancient inland lake that once covered most of the interior of southern Africa and was fed by the Zambezi River before tectonic activity forced it to change its course. The Okavango River rises in the highlands of Angola and flows more than 1500km before spilling into the delta in the heart of the Kalahari Desert.
The Okavango Delta is a collection of large and small islands, channels and floodplains, and various vegetation types such as mopane woodland and floodplain savanna. The islands are mostly fringed by thick riverine woodland including spectacular trees such as African ebony, sausage trees and various fig species.
The seasonal floodplains provide wildlife with rich grazing during the times when the water has subsided. The water is at its lowest at the beginning of the rainy season and with the arrival of the rains the floodplains green up.
The Kwando River also rises in the Angolan highlands and soon after entering Botswana it turns east, forming the Linyanti Swamp in its bend, before flowing into Lake Liambezi and becoming the Chobe River.
The Savuti Channel flows out of the Linyanti and wends its way through the arid woodlands north of the delta before emptying into the Savuti Marsh nearly 100km away in the Mababe Depression.
The Savuti has a unique history in that it has a tendency to dry up for years before flowing again. This uncertainty is now known to be caused by tectonic activity - the source of the channel becomes blocked thus stopping the flow and then reopens again after some years. The channel dried up in 1981 - and only last year did it start flowing again.
South of the great northern waterways are the more arid reaches of the Kalahari where water is at a premium. The Makgadikgadi Salt Pans are the remnant of an ancient inland lake that was fed by the Zambezi River before tectonic forces changed the course of the river.
The pans today, the largest in the world, are dry except for some seasons of exceptional rain when they may partially fill. The edges of the pans are dominated by short grasses that attract herbivores in numbers during the rainy season. The Central Kalahari is covered by arid savannah grassland and woodland. The ancient riverbeds are a haven for wildlife in the wet season where the lush grasses attract herbivores in their tens of thousands.
From this wide range of eco-systems comes Botswana's rich wildlife heritage and fascinating animal behaviour.