All these rivers have their sources in the Central Highlands and in some instances have cut deeply incised gorges into the landscape. Especially in the west they can be regarded as a linear oasis, facilitating the western distribution of many species through otherwise unsuitable habitat through the escarpment zone and the Namib Desert.
The largest of these rivers are the Hoanib in the south and the Hoarusib in central Kaokoland. Rivers with smaller catchments are the Khumib, Sechomib, Munutum, Nadas and Engo.
The riparian vegetation mainly consists of trees such as ana tree Faidherbia albida, camel-thorn Acacia erioloba, umbrella-thorn Acacia tortilis, wild tamarisk Tamarix usneoides, mustard bush Salvadora persica, leadwood Combretum imberbe, mopane Mopane colophospermum, Angolan green-thorn Balanites angolensis, wild ebony Euclea pseudebenus and makalani palm Hyphaene petersiana. On the highlands species such as tamboti Spirostachys africana, bird-plum Berchemia discolor, small-leaved brides-bush Pavetta zeyeri and magic guarri Euclea divinorum also occur.
Information provided by Wessel Swanepoel.