The Okavango catchment in Angola consists of two river systems: the Cubango with a catchment area of 115 000km? and an average annual rainfall of 983mm and the Cuito, with a catchmetn are of 65 000km? and an average annual rainfall of 876mm. A peculiarity of the Okavango Delta is that the outflows are a very minor fraction of the total input (inflow plus precipitation) due to the evapotranspiration losses from the large area. The swamp area changes continuously in response to inflow, precipitation and evapotranspiration.