Okavango River - Flood

Flood

If one thinks of the channels in the delta as the arteries of this gigantic living organism, then its heart is 1 250 km away in the Angola highlands. This distant heart beats but once a year when Angola receives three times the amount of rainfall that Botswana does, sending a giant pulse of water coursing across Africa which eventually drains its lifeblood into the waiting arteries of the Okavango. This is referred to as the flood but unlike in the rest of the world where a flood has negative connotations, in the Okavango the flood is always welcome.

Although the summer rains fall in Angola in January, they take a whole month to travel the first 1,000 km of the Okavango River. And then they take a further four months to filter through the plants and numerous channels of the final 250 km of the Delta. As a result the flood is at its biggest sometime between June and August, during Botswana’s dry winter months. And the delta swells to three times its permanent size, attracting animals from miles around and creating one of Africa’s greatest concentrations of wildlife.

At its widest point in a big flood year the seasonal swamp stretches to 150 km across from east to west. And one of the factors that leads to the ever changing nature of the Delta is the flatness of the area. To give an idea of how flat it is, if one were to take a cross section of the Delta at its widest point, along this cross section one would find that the height variation from the mean over that 150 km is less than 2m. So a little sand deposition can cause major changes.