Okavangodelta

- 19.523Koordinaten: 19 ° 30 ' S, 23 ° 0' O

The Okavango Delta is the inland delta of the Okavango Located in north- western Botswana. It is bordered on the south by the Kunyere and Thamalakane column that extend transversely to the Okavango as a hydrological barrier and represent a southern continuation of the African grave breach ( Rift Valley). The Okavango River fans out there, and seeps into the Kalahari basin and evaporated to a large extent. He is the middle of the semi-arid Kalahari with over 20,000 square kilometers, one of the largest and richest animal wetlands in Africa.

Geography and Hydrology

The Delta (actually an alluvial fan ) is divided into four areas, which differ significantly in terms of their ecology: the so-called Panhandle ( Panhandle ), the permanent water-bearing lower reaches of the Okavango River, the permanent swamps at the end of the panhandle, the temporarily dry areas covered in the periphery of the Delta as well as the larger island areas in the Okavango Delta ( Chiefs Iceland, Iceland Chitabe ) and the Sandveld tongues extending from the south in the delta.

The difference in altitude between the start of the panhandle and the foot of the Delta in Maun is at a distance of about 250 km is only 60 meters. The dry areas and islands rise only a maximum of 3 m above the surrounding area and have a size of a few square meters to many square kilometers. The origin of these dry areas is different and goes back to the channel systems, the activity of termites or geological structures. For the big island areas is believed to tectonic causes.

On a long dry season from April to November followed by a shorter, wet rainy season between December and April. The average annual rainfall is at the north end of the panhandle in Shakawe 550 mm and decreases to southeast to around 450 mm in Maun.

During the Okavango reached at Popa Falls at the beginning of the Pfannenstiel its peak in March, it will take about four months, until the tide reaches the Thamalakane in Maun at the other end of the Delta, thereby creating a water area of ​​about 12,000 square kilometers. With a correspondingly strong tide, the remaining water is discharged through the Thamalakane in the southeast of the delta. A smaller part of the water is passed through the Nhabe and Kunyere to Lake Ngami, the greater part flows through the Boteti further into the Kalahari to Lake Xau and in rare cases even further to the Makgadikgadi pan.

In particular, this massive delay of the flood, which is probably due to the strong vegetation density in the delta, is of enormous importance for wildlife in the region, since thereby the flood exactly arrives at the height of the dry season at the end of the delta and thus only rich the basis for the animal life creates.

It is of particular ecological significance, that the water of the delta is drinkable and no increased salt concentration occurs. This is remarkable, because over the Okavango about 500,000 t of dissolved salts are registered annually and 95 % of the water to evaporate, so usually significant salinity would be expected. For the lack of salinity of the water body two ecological processes are responsible: first, the transpiration predominates ( evaporation from the plant ) versus evaporation (evaporation from free water surfaces ), so there is an accumulation of salts in the islands, playing for the other the continuously changing flooding a role that gives the soil a chance to regenerate. Another explanation offer peat fire, by which the salts get into deeper layers.

Flora

Throughout the Delta about 1300 plant species have been identified. According to the four ecological areas, one can distinguish four different types of vegetation.

The canals in the delta can be found mainly large papyrus stocks ( Cyperus papyrus ) in the Panhandle glaucocladum also local stocks of Pennisetum. The vegetation along the channels may differ greatly locally.

The permanently flooded areas of the Delta outside the channels form a mosaic of open water, floating islands of vegetation and stable areas. Is correspondingly different vegetation.

In the area of ​​temporarily flooded areas is reflected depending on the duration and level of inundation different vegetation. In the highest and longest flooded areas is similar to the vegetation of the permanently flooded areas, the drier the particular area, the more bushes and trees are represented.

The islands and sandy stretches of the Delta are surrounded by grassland, which is increasingly giving way in the bushes and trees rarely flooded areas. Below are the Makalani palm ( Hyphaene petersiana ), Phoenix reclinata, a number of Ficus species (Ficus natalensis, F. sycomorus, F. veruculosa ), Syzygium cordatum, Acacia nigrescens and the Sausage Tree ( Kigelia africana). In the center of the islands there is an increased salinization of the soil due to the high evaporation, so that here also predominantly salt-tolerant plants can be found, but often also the central areas of the islands are completely free of trees.

Fauna

The size of the delta and the peculiarity that the water level in the delta if and only reaches its climax when the dry season in the surrounding areas, have the consequence that has settled an extremely versatile and dense wildlife in the environment of the Okavango delta. So far, 71 species of fish, 33 species of amphibians, 64 species of reptiles, 444 species of birds and 122 species of mammals have been identified. The rare Braunkehl heron occurs almost exclusively in the Okavango Delta.

Here, the Delta offers space for water- living species such as the hippopotamus (Hippopotamus amphibius) or Nile crocodile ( crocodilus niloticus ), swamp dwelling species such as Sitatunga, Lechwe, Waterbuck, but only animals that are dependent on water for drinking. Even species that survive long periods without water, are in the Delta to meet such as Gemsbok (Oryx gazella ).

Many species that depend on the water, hiking during the dry season, when the delta has its highest level, amplified by the surrounding countryside into a delta, including the elephants (Loxodonta africana), buffalo (Syncerus caffer ), wildebeest (Connochaetes taurinus ). The animal wealth also has a high population density of predators, including African wild dogs (Lycaon pictus), hyenas (Crocuta crocuta ... ), lion (Panthera leo), leopards (Panthera pardus ) and other big cats result. The marsh and water areas are also home to hundreds of sometimes very rare bird species.

History

The abundance of water in an otherwise arid environment has not only attractive to wildlife. Stone Age finds indicate human habitation of the area about 100,000 years ago. The area was formerly part of the Makgadikgadisees, but which is already dried up years ago about 4000. The Okavango Delta is also the first place of settled life of people in southern Africa and as the starting point of the livestock. Both are BC dates from archeology to 200 in this area. In the early 17th century, there were the first reports of River Bushmen. In the 18th century migrated some strains from the north and from the south of the different groups Batawana in the delta and settled along the Delta. Despite this migration, the delta has hardly permanent settlement. Causes is likely the remoteness of the area and the frequent occurrence of diseases such as malaria and sleeping sickness be.

Tourism

Due to its animal wealth and spectacular marsh represents the Okavango Delta, a popular destination for safari tourists, anglers and hunters dar. Almost all of the few highly regulated accommodations are as luxury lodges in the high price segment. Often they can only be reached by plane. While predominates in the central areas of the Delta and south of the safari tourism, can be found at the north -eastern edge of the delta several hunting concessions. The Okavango Delta is part of the cross-border conservation area Kavango - Zambezi Transfrontier Conservation Area.