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Posts tagged Lake Ngami

Okavango Delta and Lake Ngami, Botswana – January 22nd, 2012

20.4S 22.7E

January 22nd, 2012 Category: Image of the day, Lakes, Rivers, Wetlands

Botswana - January 6th, 2012

The Okavango Delta (or Okavango Swamp), 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. Each year approximately 11 cubic kilometres of water irrigate the 15,000 km² area.

The Okavango Delta is produced by seasonal flooding. The Okavango river drains the summer (January–February) rainfall from the Angola highlands and the surge flows 1,200 kilometres in approximately one month. The waters then spread over the 250 km by 150 km area of the delta over the next four months (March–June). The flood peaks between June and August, during Botswana’s dry winter months, when the delta swells to three times its permanent size. Some flood-waters drain into Lake Ngami, which is visible here at the center of the bottom edge.

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. Although the lake has shrunk dramatically beginning from 1890, it remains an important habitat for birds and wildlife, especially in flood years.

Africa, from Floodplain Wetlands to Dry Salt Flats

20.4S 22.7E

May 30th, 2009 Category: Lakes, Rivers

Angola, Botswana, Zambia and Namibia - May 13th, 2009

Angola, Botswana, Zambia and Namibia - May 13th, 2009

The wet, interior highland of Angola (upper left quadrant) gradually changes into dry savanna in the interior south and southeast of the country (center left). In the south-east, the rivers belong either to the Zambezi system, or, like the Okavango, drain to Lake Ngami.

Lake Ngami can be observed at the bottom right, just below the Okavango Delta in Botswana.

Visible here as a thick green line north of the Okavango Delta is the Cuando River (alternatively spelled Kwando). This dark green band also marks the border between Angola and Zambia.

The Cuando, which flows into the Zambezi River,  has a wide floodplain.  As with all rivers in south-central Africa its flow varies enormously between the rainy season when it floods and may be several kilometres wide, and the dry season when it may disappear into marshes.

Another river, recognizable as a lighter green line, is visible north of the Cuando. This is the Zambezi River, and the wide green band is an area of wetlands in its Barotse Floodplain, at the end of the rainy season.

Moving southwest to a drier region in the bottom left corner of the image, the Etosha Pan stands out as a white and green area. It is a large endorheic salt pan, forming part of the Kalahari Basin in the north of Namibia. The 120-kilometre-long (75-mile-long) dry lakebed and its surroundings are protected as Etosha National Park, one of Namibia’s largest wildlife parks.

Okavango Delta, Botswana

January 16th, 2009 Category: Lakes

Okavango Delta in Botswana - November 29th, 2008

Okavango Delta in Botswana - November 29th, 2008

The Okavango Delta is created by the Okavango River, which is unusual in that it has no outlet to the sea.

Instead, it empties onto the sands of the Kalahari Desert in Botswana, irrigating 15,000 km², and thus creating the Okavango Delta (or Okavango Swamp). This is the world’s largest inland delta.

Each year some 11 cubic kilometres of water reach the delta and the nearby Moremi Wildlife Reserve. Some of this water reaches further south to create Lake Ngami.

The waters of the Okavango Delta are subject to seasonal flooding, which begins about mid-summer in the north and six months later in the south (May/June).

The water from the delta is evaporated relatively rapidly by the high temperatures, resulting in a cycle of cresting and dropping water in the south. Islands can disappear completely during the peak flood, then reappear at the end of the season.

The water entering the delta is unusually pure, due to the lack of agriculture and industry along the Okavango River.

It passes through the sand aquifers of the numerous delta islands and evaporates/transpirates by leaving enormous quantities of salt behind. These precipitation processes are so strong that the vegetation disappears in the center of the islands and thick salt crusts are formed.

In the image, we can see the delta during a period in which it appears green with vegetation and not much salt is visible. As there is little agriculture and industry along the river north of the delta, the water is not colored tan by runoff.

source Wikipedia

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