The Okavango Delta - Story of the Floods

The Okavango Delta in Botswana is a large inland Delta formed where the Okavango River reaches a tectonic trough in the central part of the basic of the Kalahari.
Water levels are directly affected by meteorological conditions, which produce different environmental circumstances, each and every year. Of the many unpredictable forces that the locals in the Delta have to contend with, meteorological conditions are the greatest. It is unfortunately not possible to predict the exact course of each flood and rainy season, these things are simply not predictable.  This makes it very difficult and at certain times of the year, impossible, to predict water levels. The water levels in any region in the Delta can remain static for months and then drop suddenly and dramatically without warning. A short, but violent, thunderstorm, can likewise raise water levels for several weeks at a time.


The life-cycle of the Delta floods:

• January - February: The Okavango River drains the summer rainfalls from the Angola highlands and the surge flows 1,200 kilometers in approximately one month.
• March - June: The waters arrive and then spread over the 250km x 150km area of the delta over the next 4 months. The high temperature of the delta causes rapid transpiration and evaporation, resulting in a cycle of rising and falling water levels.
• June - August: The flood peaks during Botswana’s dry winter months when the delta swells to three times its  natural/usual size, attracting animals from kilometers around and creating one of Africa’s greatest concentration of wildlife.
• September – December: Temperatures begin to again rise as summer arrives and the delta waters dry and the Kalahari sand soaks it up. The major channels within the Delta remain, however the smaller waterways dry up completely. During the summer months the water levels are completely reliant on the localized rainfall whilst the Delta awaits the floods from Angola once again at the beginning of the year.

 
The delta is very flat with less than 2 metres variation in height across its 15,000km2.
Some numbers to boggle the brain:

• Each year approximately 11 cubic kilometres (11,000,000,000 litres) of water spread over the 6,000 -15,000km2 area.
• Approximately 60% is consumed through transpiration by plants
• 36% by evaporation
• 2% percolates into the aquifer system
• 2% flows in Lake Ngami

• 0% flow into any sea or ocean
  
  Information gathered from Multiple sources including Wikipedia and Footsteps in Africa