Kunene River

Published: March 24, 2012, 12:00 am

Updated: June 5, 2012, 1:57 am

Topics:

Geology (main) Conservation Biology (main) Marine Ecology (main) Biogeography (main) Water (main) Ecoregions (main) Biodiversity (main) Biomes (main) Rivers (main) Geography (main) Zoology (main) Forests (main)

Kunene River dividing Namibia and Angola through the arid Namib Desert. @ C.Michael Hogan

The Kunene River (also Cunene River) is a major watercourse in southwestern Africa, 1050 kilometers long, with its watershed primarily within the nation of Angola but also drawing water from a portion of northern Namibia.

The river rises in the central highlands of Angola, and thence flows southward to form a major element of the border between Namibia and Angola before the final discharge is to the Atlantic Ocean in the vicinity of the Angola-Benguela Front. The geometry of the Kunene riparian zone is distinctly narrow, with rugged arid landscapes persisting on both sides of the river over long distances, and a virtual lack of any major floodplains.

There is a relatively high rate of endemism of aquatic biota in the Kunene. Proposed expansion of dams on the Kunene poses a threat to biodiversity in the river, especially regarding proposals at Epupa Falls. However, a greater threat to the Kunene is a plan by Angola to greatly expand withdrawal of water from the river to expand irrigated agriculture by 600,000 hectares; not only will this action significantly diminish downriver flow rates, but also add considerable nitrate, herbicide and pesticide substances to the river.

Source: Kunene River Awareness Kit

Geology and hydrology

The ancient course of the Kunene is thought to have been connected to the present day Okavango and Zambezi Rivers; accordingly, the aquatic fauna of these rivers is interpreted to have a considerable overlap. The Kunene is Namibia's most rapidly flowing river, descending through gorges and forming rapids and waterfalls along the Angola border. The river's U-shaped cross section leaves an indelible footprint of glaciers that scraped the stony walls of rock lining the riparian zone, some 280 million years before present.

The Kunene headwatersHeadwaters are the source of water at the origin of a river or stream. are at elevations of about 2000 meters, 32 kilometers east of the town of Huambo. This plateau is known as the planalto and consists of a rolling eroded surface underlain chiefly by basement complex. The locale is fertile and well-watered and fertile, having evolved as a densely populated agricultural area. This area also hosts the headwaters of other important rivers rising in the central highlands of Angola such as the Kuanza, Queve and Kubango.

Geographically, the basin can be divided into three main sections: the Upper, the Middle and the Lower Kunene. The Upper Kunene is characterised by highlands with gentle rolling hills separated by broad shallow valleys between an altitude of 1800 and 1200 meters up to Huambo and Matala towns. The Middle Kunene consists of rolling hills in the northern areas with the terrain becoming more level towards Ruacana and the Namibian border in the south, whilst the Lower Kunene exhibits mountainous topography and semi-arid to arid conditions. As the Kunene approaches its mouth, the river crosses the Namib desert.

The relatively small catchmentCatchment is the entire area of a hydrological drainage basin. and the steep river bed slope in the upper and lower sections also mean that flows run relatively quickly to the coast, leaving the river almost dry at the end of the dry season. Tributaries of the Kunene in the northern highlands are typically perennial while the middle reaches are fed by largely perennial rivers draining wide floodplains. Tributaries in the lower reaches are entirely ephemeral, characterized by brief flash floods, and contribute negligible total flow to the Kunene due to the arid conditions encountered here. (Kunene River Awareness Kit)

The catchment area of the Kunene Basin is approximately 106,560 square kilometres (41,143 square miles) in area, of which 14 100 km² (13%) lies within Namibian territory. Its mean annual discharge is 174 cubic meters per second (6145 cubic feet per second) at its mouth on the Atlantic. Water quality of the Kunene River is relatively high, since the human population density and agricultural intensity is relatively low, including a conspicuous absence of overgrazing. However, bacteria and other microbial pathogens pose a material threat to Kunene water quality, due to the fact that only a small fraction of the domestic wastewater in Angola is treated; consequently, considerable impacts to human health from cholera, diarrhoea, typhoid, gastro-entertitis and hepatitis.

The drainage pattern of the Kunene River basin. Source: AHT GROUP AG 2010 and Kunene River Awareness Kit

Elevation profile along the Kunene River. Source: AHT GROUP AG 2010 and Kunene River Awareness Kit

Aquatic biota

Nile crocodile on Angolan side of the Kunene. Photographer is in the river at a range of four meters from the crocodile. @ C.Michael Hogan As referenced under geological history, the Kunene shares prehistorical connections to the Okavango and Zambezi, and hence shares biodiversity characteristics. Regarding freshwater bivalves, the central reaches of the Kunene manifest particularly high endemism, similar to parts of the Okavango, Chobe, Upper Zambezi and Etosha Pan basins. The bivalve Etheria elliptica, which also occurs in the Upper Zambezi, is a freshwater mussel in the family Etheriidae, known from a limited extent of the central Kunene River in Angola. It is threatened by proposed dam construction on the Kunene.

There are eighty identified fish species present in the Kunene River, five of which are endemics. The endemic taxa are:

• the 26 centimeter (cm) long demersal Kunene happy (Sargochromis coulteri);
• the eight cm long benthopelagic Kunene dwarf happy (Orthochromis machadoi);
• the 14 cm benthopelagic Namib happy (Thoracochromis buysi);
• the seven cm benthopelagic Kunene kneria (Kneria maydelli); and,
• the demersal fish Hippopotamyrus longilateralis.

Note that demersal species are those inhabiting the river floor, while benthopelagic species are those that live near the river bottom. The freshwater crab Potamonautes dubius is also endemic to the Kunene and its tributaries.

The limited distribution dragonfly Paragomphus cataractae occurs only at Epupa Falls on the Kunene along with six other southern Africa falls or rapids locations, including the downstream vicinity of Victoria Falls on the Zambezi.

Kunene estuary

Aerial view of the Kunene Estuary. @ C.Michael Hogan For millennia, the precise location of the Angola-Benguela Front has oscillated as part of the natural cycle of climate and oceanic current change. This location is not a simple intuitively obvious function of average temperature versus latitude of the Front. For example, the Front has been at the mouth of the Kunene River at a time not in the distant past, and has now moved further northward along the Angolan coast, during a presumed period of warming, leaving the Atlantic coastal oceanic current fed by the cooler Benguela Front.

The unique nature of this confluence of two oceanic currents of two distinct temperatures creates some unusual ecological outcomes. For example, as of 2011, the Angola-Benguela Front has moved from a location near the mouth of the Kunene River to a point northward. This outcome has left a disjunct population of Leatherback turtles and other warmer water organisms trapped at the Kunene mouth and estuary, where the temperature is warm enough to sustain the species. Normally these species are only found north of the Angola-Benguela Front.

Terrestrial ecoregions

Eight World Wildlife Fund ecoregions occur in the watershed of the Kunene River:

1. Angolan montane forest-grassland mosaic
2. Angolan miombo woodlands
3. Angolan mopane woodlands
4. Zambezian baikiaea woodlands
5. Angolan scarp savanna and woodlands
6. Namibian savanna woodlands
7. Kaokoveld Desert
8. Kalahari Acacia-Baikiaea woodlands

Ecoregions of the Kunene watershed. Source: World Wildlife Fund, AHT GROUP AG 2010 and Kunene River Awareness Kit

Arid grassland of the Namib Desert, several kilometers south of the Kunene. @ C.Michael Hogan In the middle reaches of the Kunene River lies the Angolan mopane woodlands ecoregion; in fact, the Kunene bisects this ecoregion and is the sole perennial watercourse in the entire Angolan mopane woodlands ecoregion. The mopane species in this ecoregion occurs either as a shrub or a tree, depending on local soil and microclimate and other abiotic conditions. In some areas it forms a dense woodland, whereas in others it grows as a low shrub intermingled with scattered trees. In Angola, the mopane thrives across expansive areas in a low, thorny bushveld. It is associated with Acacia kirkii, A. nilotica subsp. subalata, A. hebeclada subsp. tristis, A. erubescens,Combretum apiculatum, Commiphora spp.,Dichrostachys cinerea, Grewia villosa, Indigofera schimperi, Jatropha campestris, Melanthera marlothiana, Peltophorum africanum, Rhigozum brevispinosum, R. virgatum, Securinega virosa, Spirostachys africana, Terminalia prunoides, T. sericea, Ximenia americana, and X. caffra. On alluvial soils Acacia kirkii becomes abundant.

The lower reaches of the Kunene run through the Namib desert, a remote sparsely inhabited region chiefly settled by the Himba people and other Namibian and Angolan tribes. Six avian species are endemic to the Namib Desert:

• the dune lark (Certhilauda erythrochlamys)
• Benguela long-billed lark (C. benguelensis);
• Gray’s lark (Ammomanes grayi);
• bank cormorant (Phalacrocorax neglectus);
• tractrac chat (Cercomela tractrac); and,
• Rüppell’s korhaan (Eupodotis rueppellii).

The Dune lark is strictly endemic to this ecoregion while the Gray’s lark, Rüppell’s korhaan, and C. benguelensis are found only in this ecoregion and the Kaokoveld Desert ecoregion.

References

• P.Barnard,C.J. Brown, A.M. Jarvis, and A. Robertson. 1998. Extending the Namibian protected areas network to safeguard hotspots of endemism and diversity. Biodiversity and Conservation 7: 531-547.
• Matthias Basedau and Andreas Mehler. 2005. Resource politics in Sub-Saharan Africa. books.google.com 355 pages
• Will Darwall, K.Smith, W.R.T.Darwall, K.G.Smith, D.Tweddle. 2009. The Status and Distribution of Freshwater Biodiversity in Southern Africa. IUCN 118 pages
• H.U.Lass, M.Schmidt, V.Mohrholz, and G.Nausch. Hydrographic and current measurements in the area of the Angola–Benguela Front. J. Phys. Oceanogr., 30:2589–2609, 2000.
• F.C.de Moor, H.M.Barber-James, A.D.Harrison, C.R.Lugo-Ortiz. 2000. The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river. African Journal of Aquatic Science. Vol.25, no.1
• Mikiyasu Nakayama. 2003. International Waters in Southern Africa. United Nations University Press. ISBN9280810774 Google eBook
• World Wildlife Fund, C. Michael Hogan. 2012. Angolan mopane woodlands , Encyclopedia of Earth, ed. M. McGinley, NCSE, Washington DC

Citation

C. Michael Hogan (2012) Kunene River. ed. P. Saundry, Encyclopedia of Earth, NCSE. Washington DC retrieved from http://editors.eol.org/eoearth/wiki/Kunene_River