Okavango River

Okavango
River
Sign overlooking a ferry crossing on the Okavango from Botswana into Namibia
Countries Angola, Namibia, Botswana
Mouth
 - location Moremi Game Reserve, Botswana
Length 1,700 km (1,056 mi)
Basin 530,000 km2 (204,634 sq mi)
Discharge
 - average 475 m3/s (16,774 cu ft/s)
 - max 1,000 m3/s (35,315 cu ft/s)
 - min 350 m3/s (12,360 cu ft/s)
Okavango river basin map

The Okavango River (formerly spelled Okovango or Okovanggo) is a river in southwest Africa. It is the fourth-longest river system in southern Africa, running southeastward for 1,600 km (990 mi). It begins in Angola, where it is known by the Portuguese name Rio Cubango. Further south it forms part of the border between Angola and Namibia, and then flows into Botswana, draining into the Moremi Game Reserve.

Before it enters Botswana, the river drops four metres in a series of rapids known as Popa Falls, visible when the river is low, as during the dry season.[1]

Discharging to an endorheic basin, the Okavango does not have an outlet to the sea. Instead, it empties into a swamp in the Kalahari Desert, known as the Okavango Delta or Okavango Alluvial Fan. In the rainy season there is an outflow to the Boteti River which in turn seasonally discharges to the Makgadikgadi Pans, which features an expansive area of rainy season wetland where tens of thousands of flamingos congregate each summer.[2] Part of the river's flow fills Lake Ngami. Noted for its wildlife, the Okavango area contains Botswana's Moremi Game Reserve.

During colder periods in Earth's history, a part of the Kalahari was a massive lake, known as Lake Makgadikgadi. In this time, the Okavango would have been one of its largest tributaries.

Water conflict

Both Namibia and Botswana experience drought and as a result of this, there have been concerns about possible conflict over use of the river's water. Namibia has built a water canal, measuring about 300 km long, and has proposed a project to build a 250 km pipeline to divert water from the river into Namibia to help relieve the drought.[3][4]

Botswana, however uses the Okavango Delta for both tourism income and a water source. The Department of Water Affairs in Botswana has submitted that 97% of the water in the river is lost through evaporation, so the country cannot afford to lose any extra water.

Namibia, in turn, has argued that it will only divert half a percent of the river's flow, and that it is entitled to any water that flows through its country. To deal with such issues, in September 1994 Angola, Namibia and Botswana signed an agreement to form the Permanent Okavango River Basin Water Commission (OKACOM), to provide advice to the three countries about the best ways to share the Okavango River's resources.[4][3]

Flood

Every wet season, Angola receives three times more rainfall than Botswana, discharging a higher than usual flow into the Okavango, turning swathes of outlying desert into a huge wetland.

Although the summer rains fall in Angola in January, they take a whole month to travel the first 1,000 km of the Okavango River. And then they take a further four months to filter through the plants and numerous channels of the final 250 km of the Delta. As a result, the flood is at its biggest sometime between June and August, during Botswana’s dry winter months. And the delta swells to three times its permanent size, attracting animals from miles around and creating one of Africa’s greatest concentrations of wildlife.

At its widest point in a big flood year the seasonal swamp stretches to 150 km across from east to west. And one of the factors that leads to the ever-changing nature of the Delta is the flatness of the area. If one were to take a cross section of the Delta at its widest point, one would find that the height variation from the mean over that 150 km is less than 2m, which means that a minor sand deposition can cause major changes.[5]

In very wet years, a part of the river's flow may extend along the Magweggana River (actually a northeastern distributary of the Okavango delta) and enter the Zambezi river, bypassing the Kalahari.

References

  1. ↑ Siyabona Africa Travel (Pty) Ltd, "Popa Falls | Okavango River | Botswana" webpage: TravelZA-PopaFalls
  2. ↑ C. Michael Hogan (2008) Makgadikgadi, The Megalithic Portal, ed. A. Burnham
  3. 1 2 Basedau, Matthias (2005-01-01). Resource Politics in Sub-Saharan Africa. GIGA-Hamburg. p. 294. ISBN 9783928049917.
  4. 1 2 Varis, Olli; Tortajada, Cecilia; Biswas, Asit K. (2008-03-15). Management of Transboundary Rivers and Lakes. Springer Science & Business Media. p. 96. ISBN 9783540749288.
  5. ↑ http://blog.africabespoke.com/okavango-delta-part-2/ Okavango River Flooding

Coordinates: 18°57′43″S 22°29′04″E / 18.96194°S 22.48444°E / -18.96194; 22.48444

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