The Okavango Delta is more correctly termed an alluvial fan comprising areas that are permanently, seasonally and occasionally flooded.
With sources in the plan alto highlands 1200 metres above sea level in Angola, the Okavango Delta is the culmination of a river system that has its catchment areas in Angola, flows through Namibia and then into Botswana where various processes govern the distribution across the alluvial fan.
These processes are both physical, dependent on slope, sedimentation, faults and channels carved long ago in the Kalahari Sands and also biological, shaped hippopotami pushing their way along the waterways, termites constructing their intricate mounds and the natural growth of papyrus. With so many factors shaping the Okavango, it is not surprising that the flow of water is variable and unpredictable.
The Delta consists of a multitude of main channels, smaller tributaries and lagoons as well as floodplains, islands and mainland areas. The watercourses are always changing due to annual flooding as well as a combination of sediment transport, seismic activity, the construction of termite mounds, the continual opening up of new channels by feeding hippopotami and the closing of others by new vegetation growth.
There are two somewhat distinct areas of the Delta – the permanent swamp which is inundated with water all year round, and the seasonal swamp which is flooded annually and dries gradually with the onset of summer. The vegetation of the permanent swamp includes groves of wild date palm, swathes of papyrus, islands fringed with forest and lagoons covered with floating water lilies. The seasonal swamp areas consist of open floodplains covered with grasses during the summer and inundated with water during the winter. The edges of these floodplains support tall and elegant real fan palms, sausage trees, fig trees and a variety of scrub vegetation.