The information and processes described in this section focus on the catchments of the Cubango, Cuito, Cuando and Zambezi rivers within south-eastern Angola. Their upper catchments and the Western Zambezi broadly form an area called the Okavango-Zambezi Water Tower. This is a highland consisting largely of sand which delivers most of the water carried south by the four rivers. Little, if any water is added in the lower catchments of the Cubango, Cuito and Cuando. All three rivers later flow south into Namibia and Botswana, and no further. The Zambezi is somewhat different, its upper catchment consisting of the Western Zambezi in Angola; and the elongate Bulozi Floodplain, that straddles the border of Angola and Zambia; and then the eastern Zambezi within Zambia. Water flowing into the Barotse Floodplains thus comes from three rather different, and perhaps complementary drainage systems. This report has two major purposes. First, is to inform managers and others concerned with KAZA about the origins of the four rivers that flow as linear oases through the trans-frontier conservation area. This was the need expressed by WWF (World Wildlife Fund) and TNC (The Nature Conservancy), and the document presented here forms part of the report commissioned for these two organisations. The second purpose comes from a need identified and expressed separately by TNC, which was to assemble information on the Upper Cubango, particularly regarding its functioning and current, proposed and possible developments. These developments may influence episodic flows in the Cubango River which are now critical for the productive functioning of the Okavango Delta.