Seasonal flooding in the Okavango Delta, Botswana - recent history and future prospects

Seasonal flooding in the Okavango Delta is influenced equally by local rain fall and in-flow from the catchment to the north. Local rainfall is convect ive, modulated by the semi- permanent anticyclone over southern Africa and easterly waves, and is subject to the well-documented 18-year oscillation o f the subcontinental interior. The catchment is more strongly influenced by the ITCZ and CAB. The easterly catchment (Quito River) responds to instabi lities in tropical lows in the Indian Ocean easterlies, and the western cat chment (Cubango River) to variability in the Atlantic equatorial westerlies . The latter shows a quasi-18-year oscillation, which is out of phase with that to the south. This has buffered flooding in the Okavango swamps in the past. Discharge in the Quite has declined since 1980, which has had a seve re influence on flooding in the Okavango swamps. This decline Is also evide nt in discharge records of the Zambezi, and the longer Zambezi record sugge sts that this may be related to an 80-year oscillation.