In Angola, much of the Cuvelai Drainage stretches between the Kunene River (called Rio Cunene in Angola) in the west and the Okavango River (Rio Cubango) in the east. It is from this upper catchment in southern Angola that the Cuvelai receives most of its water. From there, about 100 channels (iishana) cross into Namibia and then progressively merge into the Omadhiya lakes from where water sometimes flows south into Etosha Pan, its final destination. As a result of gentle gradients, water flows slowly, but infiltration is limited since most of the channels have beds of impermeable clay or saline soil. The channels vary in width from less than ten metres to over a kilometre. Surface water flows are entirely contained within the Owambo Basin, with all water either evaporating or seeping into the ground; river basins with these characteristics are called 'endorheic'.

To the east and south of the Cuvelai Drainage are two areas where there is little surface water and few people live. The northeastern area has a few ephemeral drainage lines and a deep cover of aeolian sand which holds little water and few nutrients. Following good rains, water may flow along the drainage lines but the flows seldom go far or reach the network of iishana channels. Much of the inactive drainage area to the south and west is rocky, in part of Otavi Group dolomites (figure 2.16) in gentle hills which overly karst aquifers, and partly of flatter areas dominated by calcretes which formed from calcium carbonates that dissolved out of the dolomites. There is little surface water in this southern area.