Surface Water in the Basin

The surface water resources in the basin are dominated by the perennial Kunene River and its tributaries in Angola, as well as some ephemeral rivers in the southern part of the basin.

Rivers and Streams

The majority of the runoff is generated from the rain falling between October and March over the highlands of Angola. The catchment lies relatively far to the west of the country where rainfall is largely unreliable and variable, resulting in a large difference between good and bad years. The relatively small catchment and steep river bed slope in the Upper and Lower section also mean that flows run relatively quickly to the coast, leaving the river almost dry at the end of the dry season.

The long term average catchment runoff for the Kunene River basin measured from gauging stations is estimated at approximately 5 000 Mm³/a (million cubic meters per annum) at Ruacana, 1 600 Mm³/a at Gove and 4 900 Mm³/a at Matala. There is currently no information available on the runoff of tributaries and sub-catchments.

The major tributaries of Kunene River are:

• The Que River - the longest tributary in the dense river network of the Upper Kunene sub-basin with a length of 140 km. It drains the south western part of the sub-basin.
• The Chitanda River - drains the eastern part of the Middle Kunene and has a length of 265 km.
• The Mucope River - originates just south of Matala in the center of the basin and drains most of the central floodplain in the Middle Kunene sub-basin, with a length of 190 km.
• The Kaculuvar River - originates near Lubango and drains the western part of the Middle Kunene.  It is the longest tributary of the Kunene with a length of over 320 km.
• The Otjindjangi River originates in Namibia and only flows for part of the year during and immediately after precipitation (ephemeral stream). It drains part of the Lower Kunene sub-basin.

A map with the drainage pattern of the Kunene River basin is provided below: While the tributaries in the semi-arid Lower Kunene are commonly ephemeral streams, many of the channels in the Middle Kunene are non-perennial and all streams in the Upper Kunene basin are perennial.

Lakes

There are no naturally occurring lakes in the Kunene basin, but there are man-made dams on the Kunene River and some of its tributaries, storing water for water flow regulation, irrigation, hydropower generation and domestic water supply:

• The Cuando Dam on the Etembo tributary, near Huambo, and the Gove Dam in the Upper Kunene;
• The Matala Dam  in the Middle Kunene; and
• The Ruacana Dam and Olushandja, storing water from the Calueque Dam in the Lower Kunene.

Pans and Vleis

Vleis can occur in the Lower Kunene after rains when a shallow seasonal or intermittent lake is formed. There are no pans in the modern Kunene River basin but the Etosha pan in Namibia is believed to have been created by the Kunene in the distant past, while the Oshakati pan is occasionally flooded by the Kunene River.

From Ruacana, the river used to flow south-eastwards into Namibia where it discharged into a great lake in the Etosha district in Namibia. However, at some time, perhaps during a great flood, it must have overflowed the banks of the old Kunene channel and found a new course to the sea, its waters being captured by another river. The old courses leading to Etosha remain clear but now contain only intermittent streams, while the Etosha Pan is the remnant of the lake. The pan is currently a shallow saline depression which has not been fully flooded during the past 50 years.

The Oshakati Pan in northwest Namibia is another pan connected to the Kunene River but not physically located in the basin. The pan consists of fossil drainage lines, interconnecting many long linear pans, extending southwards from the Kunene Flats of Angola into Namibia. Water enters the northern sector, in Angola, from the Mui and Cuvelai Rivers (Hughes and Hughes 1992).

There is still uncertainty and no evidence whether the Kunene River would at very high floods overflow into the channels ('aka shanas' or 'iishana') of the Cuvelai Basin. Satellite images during the high floods in 2008, 2009 and 2011 did not show active flow linkages (see also Floods in the Basin chapter).