The Okavango River (formerly spelled Okovango or Okovanggo), also known as the Cubango River, is a river in southwest Africa. It is the fourth-longest river system in southern Africa, running southeastward for 1,600 km (1,000 mi). It begins at an elevation of 1,300 metres (4,300 ft) in the sandy highlands of Angola. Farther south, it forms part of the border between Angola and Namibia, and then flows into Botswana. The Okavango does not have an outlet to the sea. Instead, it discharges into the Okavango Delta or Okavango Alluvial Fan, in an endorheic basin in the Kalahari Desert.
In Angola, the upper reaches of the Cuito (a tributary river to the Okavango) suffers clogging due to controlled burns of the vegetation, reducing water flow downstream as the accumulated water instead flows into the sand.[1]
Before it enters Botswana, the river drops 4 m in a series of rapids known as Popa Falls, visible when the river is low, as during the dry season.[2]
In the rainy season, an outflow to the Boteti River 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.[3] Part of the river's flow fills Lake Ngami. Noted for its wildlife, the Okavango area contains Botswana's Moremi Game Reserve.
Flood
Popa Falls (2018)
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. The delta then swells to three times its permanent size, attracting animals from kilometres 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; 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 2 m, which means that a minor sand deposition can cause major changes.[4]
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.
Sediment transport
The river carries annually 28,000 tonnes of suspended sediment and a similar amount of bedload to the terminal swamps.[5] Most of the particulate sediment carried by the river is fine sand, with some silt and mud, thanks to the geological makeup of the Okavango River catchment which is largely underlain by Kalahari sand. There is low concentration of dissolved solids in the river water - around 40 mg/L, made up mostly of silica, calcium and magnesium bicarbonates - but these dissolved solids form the largest component of sediment carried into the delta because the annual water volume is so large.[6]
History
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.
Both Namibia and Botswana experience drought, and as a result, concerns have been expressed 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.[7][8]
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 of one percent of the river's flow, and that it is entitled to any water that flows through its territory. To deal with such issues, in September 1994, Angola, Namibia, and Botswana signed an agreement to form the Permanent Okavango River Basin Water Commission, to provide advice to the three countries about the best ways to share the Okavango River's resources.[8][7]
^Hanibal Lemma, and colleagues (2019). "Bedload transport measurements in the Gilgel Abay River, Lake Tana Basin, Ethiopia". Journal of Hydrology. 577: 123968. Bibcode:2019JHyd..57723968L. doi:10.1016/j.jhydrol.2019.123968. S2CID 199099061.
^McCarthy, T S (October 2013). "The okavango delta and its place in the geomorphological evolution of Southern Africa". South African Journal of Geology. 116: 1–54. doi:10.2113/gssajg.116.1.1.
^ abBasedau, Matthias (2005-01-01). Resource Politics in Sub-Saharan Africa. GIGA-Hamburg. p. 294. ISBN9783928049917.
^ abVaris, Olli; Tortajada, Cecilia; Biswas, Asit K. (2008-03-15). Management of Transboundary Rivers and Lakes. Springer Science & Business Media. p. 96. ISBN9783540749288.
okavango, river, other, uses, cubango, formerly, spelled, okovango, okovanggo, also, known, cubango, river, river, southwest, africa, fourth, longest, river, system, southern, africa, running, southeastward, begins, elevation, metres, sandy, highlands, angola,. For other uses see Cubango The Okavango River formerly spelled Okovango or Okovanggo also known as the Cubango River is a river in southwest Africa It is the fourth longest river system in southern Africa running southeastward for 1 600 km 1 000 mi It begins at an elevation of 1 300 metres 4 300 ft in the sandy highlands of Angola Farther south it forms part of the border between Angola and Namibia and then flows into Botswana The Okavango does not have an outlet to the sea Instead it discharges into the Okavango Delta or Okavango Alluvial Fan in an endorheic basin in the Kalahari Desert OkavangoOkavango in Kavango NamibiaOkavango river basin mapLocationCountriesAngolaNamibiaBotswanaPhysical characteristicsMouth locationMoremi Game Reserve BotswanaLength1 700 km 1 100 mi Basin size530 000 km2 200 000 sq mi Discharge average475 m3 s 16 800 cu ft s minimum350 m3 s 12 000 cu ft s maximum1 000 m3 s 35 000 cu ft s Contents 1 Flow 2 Flood 3 Sediment transport 4 History 5 Water conflict 6 References 7 External linksFlow EditMain article Kalahari Basin In Angola the upper reaches of the Cuito a tributary river to the Okavango suffers clogging due to controlled burns of the vegetation reducing water flow downstream as the accumulated water instead flows into the sand 1 Before it enters Botswana the river drops 4 m in a series of rapids known as Popa Falls visible when the river is low as during the dry season 2 In the rainy season an outflow to the Boteti River 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 3 Part of the river s flow fills Lake Ngami Noted for its wildlife the Okavango area contains Botswana s Moremi Game Reserve Flood Edit Popa Falls 2018 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 The delta then swells to three times its permanent size attracting animals from kilometres 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 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 2 m which means that a minor sand deposition can cause major changes 4 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 Sediment transport EditThe river carries annually 28 000 tonnes of suspended sediment and a similar amount of bedload to the terminal swamps 5 Most of the particulate sediment carried by the river is fine sand with some silt and mud thanks to the geological makeup of the Okavango River catchment which is largely underlain by Kalahari sand There is low concentration of dissolved solids in the river water around 40 mg L made up mostly of silica calcium and magnesium bicarbonates but these dissolved solids form the largest component of sediment carried into the delta because the annual water volume is so large 6 History EditDuring 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 Confluence of Cuito from top and Okavango flowing from left to right 2018 18 01 40 S 020 47 31 E 18 02778 S 20 79194 E 18 02778 20 79194Water conflict EditBoth Namibia and Botswana experience drought and as a result concerns have been expressed 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 7 8 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 of one percent of the river s flow and that it is entitled to any water that flows through its territory To deal with such issues in September 1994 Angola Namibia and Botswana signed an agreement to form the Permanent Okavango River Basin Water Commission to provide advice to the three countries about the best ways to share the Okavango River s resources 8 7 References Edit Society National Geographic Okavango Wilderness Project www nationalgeographic org Into the Okavango Archived from the original on 8 November 2020 Siyabona Africa Travel Pty Ltd Popa Falls Okavango River Botswana webpage TravelZA PopaFalls permanent dead link C Michael Hogan 2008 Makgadikgadi The Megalithic Portal ed A Burnham 1 http blog africabespoke com okavango delta part 2 Archived 2009 07 19 at the Wayback Machine Okavango River Flooding Hanibal Lemma and colleagues 2019 Bedload transport measurements in the Gilgel Abay River Lake Tana Basin Ethiopia Journal of Hydrology 577 123968 Bibcode 2019JHyd 57723968L doi 10 1016 j jhydrol 2019 123968 S2CID 199099061 McCarthy T S October 2013 The okavango delta and its place in the geomorphological evolution of Southern Africa South African Journal of Geology 116 1 54 doi 10 2113 gssajg 116 1 1 a b Basedau Matthias 2005 01 01 Resource Politics in Sub Saharan Africa GIGA Hamburg p 294 ISBN 9783928049917 a b Varis Olli Tortajada Cecilia Biswas Asit K 2008 03 15 Management of Transboundary Rivers and Lakes Springer Science amp Business Media p 96 ISBN 9783540749288 External links Edit Geography portal Africa portalOKACOM Homepage Coordinates 18 57 43 S 22 29 04 E 18 96194 S 22 48444 E 18 96194 22 48444 Retrieved from https en wikipedia org w index php title Okavango River amp oldid 1139524695, wikipedia, wiki, book, books, library,
