Okavango River
Encyclopedia
The Okavango River is a river
in southwest Africa
. It is the fourth-longest river system in southern Africa, running southeastward for 1600 km (994.2 mi). It begins in Angola
, where it is known as the Cubango River. 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 meters, across the full 1.2 km-width of the river, in a series of rapids known as Popa Falls, visible when the river is low, as during the dry season.
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 Pan
s, which features an expansive area of rainy season wetland
where tens of thousands of flamingo
s congregate each summer. Part of the river's flow fills Lake Ngami
. Noted for its wildlife
, the Okavango area contains Botswana's Moremi Game Reserve.
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, however, 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 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.
as the arteries of this gigantic living organism, then its heart is 1 250 km away in the Angola
highlands. This distant heart beats but once a year when Angola receives three times the amount of rain
fall that Botswana
does, sending a giant pulse of water coursing across Africa
which eventually drains its lifeblood into the waiting arteries of the Okavango. This is referred to as the flood
but unlike in the rest of the world where a flood has negative connotations, in the Okavango the flood is always welcome.
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. To give an idea of how flat it is, if one were to take a cross section of the Delta at its widest point, along this cross section one would find that the height variation from the mean over that 150 km is less than 2m. So a little sand deposition can cause major changes.
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
in southwest Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. It is the fourth-longest river system in southern Africa, running southeastward for 1600 km (994.2 mi). It begins in Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
, where it is known as the Cubango River. Further south it forms part of the border between Angola and Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
, and then flows into Botswana
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
, draining into the Moremi Game Reserve.
Before it enters Botswana, the river drops four meters, across the full 1.2 km-width of the river, in a series of rapids known as Popa Falls, visible when the river is low, as during the dry season.
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
Kalahari Desert
The Kalahari Desert is a large semi-arid sandy savannah in Southern Africa extending , covering much of Botswana and parts of Namibia and South Africa, as semi-desert, with huge tracts of excellent grazing after good rains. The Kalahari supports more animals and plants than a true desert...
, known as the Okavango Delta
Okavango Delta
The Okavango Delta , in Botswana, is the world's largest inland delta. It is formed where the Okavango River empties onto a swamp in an endorheic basin in the Kalahari Desert, where most of the water is lost to evaporation and transpiration instead of draining into the sea...
or Okavango Alluvial Fan. In the rainy season there is an outflow to the Boteti River
Boteti River
The Boteti River is a natural watercourse in Botswana. It derives flow from the core Okavango Delta through the Thamalakane River in Maun. It flowed year-round before the mid 1990s, after which decreasing flows led to seasonal desiccation in some lower reaches...
which in turn seasonally discharges to the Makgadikgadi Pan
Makgadikgadi Pan
The Makgadikgadi Pan is a large salt pan in the middle of the dry savanna of northeastern Botswana. It is one of the largest salt flats in the world...
s, which features an expansive area of rainy season wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
where tens of thousands of flamingo
Flamingo
Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae...
s congregate each summer. Part of the river's flow fills Lake Ngami
Lake Ngami
Lake Ngami is an endorheic lake in Botswana north of the Kalahari Desert. It is seasonally filled by the Taughe River an affluent of the Okavango River system flowing out of the western side of the Okavango Delta. It is one of the fragmented remnants of the ancient Lake Makgadikgadi...
. Noted for its wildlife
Wildlife
Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....
, the Okavango area contains Botswana's Moremi Game Reserve.
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.Botswana, however uses the Okavango Delta
Okavango Delta
The Okavango Delta , in Botswana, is the world's largest inland delta. It is formed where the Okavango River empties onto a swamp in an endorheic basin in the Kalahari Desert, where most of the water is lost to evaporation and transpiration instead of draining into the sea...
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, however, 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 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.
Flood
If one thinks of the channels in the deltaRiver delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
as the arteries of this gigantic living organism, then its heart is 1 250 km away in the Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
highlands. This distant heart beats but once a year when Angola receives three times the amount of rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
fall that Botswana
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
does, sending a giant pulse of water coursing across Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
which eventually drains its lifeblood into the waiting arteries of the Okavango. This is referred to as the flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
but unlike in the rest of the world where a flood has negative connotations, in the Okavango the flood is always welcome.
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
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...
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
Wildlife
Wildlife includes all non-domesticated plants, animals and other organisms. Domesticating wild plant and animal species for human benefit has occurred many times all over the planet, and has a major impact on the environment, both positive and negative....
.
At its widest point in a big flood year the seasonal swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or 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. To give an idea of how flat it is, if one were to take a cross section of the Delta at its widest point, along this cross section one would find that the height variation from the mean over that 150 km is less than 2m. So a little sand deposition can cause major changes.