As Chad Basin, also known as the Lake Chad basin is called a low-lying, from the center in all directions, gradually rising level in Central and West Africa. From the environmental program of the United Nations shortly UNEP, Division connected to the Global International Waters Review, GIWA short, the region of the Chad Basin is managed as GIWA region No. 43.
The Chad Basin extends between 6 ° and 24 ° north latitude and between 8 ° and 24 ° east longitude. It covers an area of about 2.434 million km ², which corresponds to about 8% of the total area of the African continent and therefore it belongs to the large pool endorheischen the earth. Due to its location in the northern center of Africa 's natural spaces are characterized by very different landscapes and vegetation types. About half of the basin ( the North) occupied by the Ténéré Desert, Erg and the Erg du Bilma you Djourab. In the central part of the basin the desert goes on with their typical thorn bush savannah and dry in the semi-arid vegetation zones of the Sahel. In the catchment areas of the rivers Chari, Logone and Komadougou Yobe to large internationally important flood plains stretch. Along the river courses developed gallery forests and in the southern part of the basin, there are also the humid savannas of the Sudan with its typical dry forests.
The best-known geophysical element of the Chad Basin is Lake Chad, he determined for thousands of years the development of people, flora and fauna in this region. As a water reservoir between the desert and savannah of the Lake Chad has since time immemorial attracted many immigrants, explorers and adventurers to the present day. The annual fluctuation of the water level and the flood that is associated with this cyclical change, opened opportunities for the development of cultures and peoples, but also offered refuge and protection. The Chad Basin served as a crossroads for both ruling dynasties, and on Civil and presented by a region is, in the new political formations were able to develop that developed its own dynamics and extend well beyond this region. At the same time, the region also formed but always a natural boundary that prevented trade and interaction.
Despite the important role in the development of the cultural history of North, West and Central Africa, the social sciences, unlike the natural sciences, the Chad Basin discovered relatively late as a rich and promising area of research.
- 2.1 aquifers
- 2.2 emergence
- 3.1 Archaeological and written sources about the Chad Basin
- 4.1 Evaporation potential
- 4.2 The West African monsoon
- 4.3 paleoclimate
- 4.4 Air carousel of the last 1000 years
- 5.1 rivers
- 5.2 wadis
- 5.3 Lake Chad
- 5.4 Fitri Lake
- 5.5 Iro Lake
- 5.6 The lakes in the Kanem region
- 5.7 Ounianga lakes
- 6.1 Sahara vegetation zone
- 6.2 Tibesti - Jebel Uweinat mountain desert vegetation zone
- 6.3 Western Sahara deserts mountain vegetation zone
- 6.4 South Sahara grass and shrub savannah
- 6.5 Sahelian Acacia savanna
- 6.6 Lake Chad flooded savanna
- 6.7 Western Sudan savanna
- 6.8 Eastern Sudan savanna
- 6.9 Northern Congo forest - savanna vegetation zone
The Lake Chad basin is surrounded by high mountain ranges in the north and east, and south of up to 1420 meters high north equatorial threshold, which extends up to the watershed of the Nile, Congo and Shari in which up to 1330 meters high Bongo Massif. In the east it extends up to the 3088 meter high Jebel Marra in Darfur, in the northeast of the basin, the Ennedi massif rises up to 1450 meters on. In the north of the valley is located in the volcanic mountains of Tibesti, with 3415 meters ( Emi Koussi ) the highest elevation in the Central Sahara and the plateau of Djado. The border in the northwest mark the mountain ranges of the Tassili n'Ajjer, highest mountain Jebel Azao with 2,158 meters, in Algeria and of the Aïr Mountains in Niger. In the southwest of the Chad Basin, the Bauchiplateau, the Biu Plateau and the Mandara Mountains marks the geographical border. In the center of the Chad Basin is the Bodélé depression, it is also the deepest part of the Chad Basin, about 155 meters above sea level and is considered one of the richest natural sources of dust of the earth. From this region of particulate matter per year, up to 700,000 tons mobilized into the stratosphere, which then moves westward across the Atlantic, and contributes significantly to the fertilization of the Amazon rainforest. Lake Chad is located at 275 meters above sea level. Along the major river systems extend over an area of 90 to 100,000 km ², the major flooding savannas in the Logoneebene / Toupouri Valley, Massenya level, level of Aouk and Salamat in Chad, Grand Yaeres in the border region Cameroon / Chad, and the Hadejia - Nguru wetlands in Nigeria. Migratory birds in the northern hemisphere use this wet savannas as a resting and wintering quarters on their migration routes in tropical Africa.
At the Chad basin total of 8 African countries have a share. The demarcation between them follows the breakdown of the region from the colonial era, which the tribal areas, such as the Tuareg, spread over several states. Territorial the Chad Basin is subdivided as follows: Chad covered with 1.123 million km ², the center and the Sudan with 97.7 thousand km ² the east, the Niger covered with 674.8 thousand km ² the western part of the South share the states in Nigeria with 179.3 thousand km ², Cameroon with 47,700 km ² and the Central African Republic 216,000 km ². To the north are 91,000 km ² in Algeria and about 5100 km ² in Libya.
Lake Chad Basin Commission
The Lake Chad Basin Commission was established on 22 May 1964, headquartered in Fort Lamy, now N'Djamena. The founder states of this Commission were Cameroon, Niger, Nigeria and Chad. The Lake Chad Basin Commission currently has six member countries: Chad, Central African Republic, Cameroon, Nigeria, Niger, and Libya since April 2007. Sudan has only observer status since 1994, and Algeria has no activities. The Commission is responsible for the regulation and supervision of the use of water and other natural resources within the hydro- active regions of the Chad Basin. The Commission has adopted a subdivision of the Basin Committee for Strategic Planning ( BCSP ), this coordinate local activities of member countries.
The Lake Chad Basin Commission checks and monitors the hydro-active regions in the Chad Basin and refers to them as "conventional " basin. This conventional basin was in 1964 at the founding of approximately 427,500 km ². The definition states that it excludes areas that have no effective hydrological contribution to the water balance of the conventional basin, this affects mainly the northern regions of the basin. The area of the Control Commission was later expanded to include the hydro-active regions in northern Nigeria, in the south of Chad and northern Central African Republic. The current face of the conventional basin covers approximately 967,000 km ².
The largest areas of Chad Basin are covered by Quaternary sands. Below the sand layer, lying at about 75 m depth clays that have arisen in the Pliocene and have an average thickness of about 280 m. Under this clay layer is again an approximately 30 meter thick layer of sand that has arisen in the lower Pliocene. Below this layer are the aquifers of the actual Pliocene aquifer. Among appear sandstone formations called Continental Terminal and originated in the Tertiary, with a thickness of about 150 m. Below this layer is the lowermost aquifer, which is referred to as Continental Hamadien and originated in the Cretaceous period.
The aquifers in the Chad Basin is mainly composed of a series of deposits. These sediments, the four aquifers occur: the upper Quaternary phreatic aquifer, the Lower Pliocene aquifer, the Continental Terminal and the Continental Hamadien. Studies suggest that these aquifers are fed by percolating surface water, for this reason they are very sensitive to changes in climatic conditions and particularly to changes in runoff regime.
The quality of the groundwater of the Quaternary phreatic aquifer is suitable for the consumption of the local population and livestock. The lower Pliocene aquifer is at depths of about 250 m, with an average thickness of 60 meters. The capacity of the Lower Pliocene aquifer is unknown, but is used mainly in the Nigerian part of the basin. The withdrawal from this aquifer is estimated at about 3 million cubic meters per year.
The Continental Terminal aquifer is essentially a change from sandstone and clay. The deepest aquifer in the region is Continental Hamadien. This is an important aquifer extends to in some other West African regions of him are very few information.
In general, the active hydrographic basin is estimated at around 967,000 km ² in northern and northeastern boundary of the basin are the Nubian Sandstone aquifer and are located on the western border of the Iullemeden aquifers.
The Lake Chad basin was formed by extensional tectonic forces during the Cretaceous period. The geological and geomorphological development of the basin was accompanied by a slow and " cold " Stretching the reduction zone, due to the emergence of the West and Central African grave system. This had the consequence that resulted in a regional hydrological sink that is called Artesian Chad Basin. The Lake Chad basin is part of a large meridional zone of subsidence areas, extending from the Gulf of Gabes in the north to the Karoo level.
The total population was determined in 2003 with about 39 million inhabitants and is composed of more than 70 nations or ethnic groups. In Nigeria, about 22 million people, which accounts for approximately 59% of the total population in Chad about 8 million, 3 million in Sudan, Niger about 2 million, in Cameroon, about 2 million, the Central African Republic about 1 million people. The areas in Algeria and Libya are not considered to be inhabited, and only occasionally visited by nomads.
The population density is very unevenly distributed, while the northern regions have a population density of 0-1 inhabitants / km ², which is rising in the south-western regions of Nigeria at up to 500 inhabitants / km ². It is the most populous region around Kano in Nigeria, the east and the south shore of Lake Chad to find. A specific data collection is very difficult because the states often suffer from political instability.
Archeology and written sources about the Chad Basin
In 2001, TM was 266 at Borkou found a 7-6 million-year fossil in the reference, the Sahelanthropus tchadensis was named. From its discoverers, it was referred to as the oldest so far discovered may link in the human family tree after the separation of the chimpanzee, that is a close relative of the earliest common ancestor of Hominini. 1995 12 already from 3.5 to 3.0 million year old mandible was discovered on the north - Chadian reference KT, which was placed on the new type Australopithecus bahrelghazali.
The settlement of the Chad basin was determined from the change of pluvial and Interpluvialzeiten since time immemorial. Only from the age of Tschadien could archeological findings confirm this settlement. These include the burial grounds of the archaeological site in the western Gobero Chad Basin, which could be determined in two periods 7700-6200 BC and 5200-2500 BC.
Another find is a 8000 year old canoe that was found on the banks of Komadugu - Yobe River system; it is one of the oldest boats in human history.
The earliest highly developed culture was located in the southwestern Chad Basin and was named Gajiganna culture; the findings promoted simple clay figures of people and animals to day and from about 500 BC, fortified settlements could be detected. It consisted in a period of about 1800 to about 400 BC The most important archeological site of this culture is Zilum. It was replaced from about 400 BC by an iron-working culture, as demonstrated on the diggings Mdaga. Whether there was a transfer of technology from the Middle East, it is highly controversial because the Verhüttungstechnik that of the neighboring Nok culture is like.
More reports on the Chad Basin are narrated by Claudius Ptolemy, who mentions a kingdom of Agisymba in the 2nd century, which to this day is controversial, where it was, as in this report, no location information exist, but only vaguely taken from high ground nameless mountains talking about.
Archaeological traces in the Chad Basin can be found again until the 6th century AD, with the development of the Sao culture and their excavation sites south-east of Lake Chad.
The first European source via the Chad Basin is Leo Africanus, who traveled in the region in 1513 and a land Shary and Lake Gaoga reported. Other sources can be found in the book L' Universale Fabrica, written by Giovanni Lorenzo Anania, the ( Niger ) and the lake Lago di Sauo Saharan reports of a Rio Negro. This work was published in 1571-1592 in several volumes and served numerous cartographers this time as the source.
Since the geography of inner Africa was virtually unknown until the 19th century, these are the only sources of the region from that time. The first modern reports submitted by the German Friedrich Conrad Hornemann, who traveled in the region in 1800 in the British mandate; other reports submitted by Denham, Clapperton and Oudney from the year 1841. Probably the most famous traveler in the region but were Heinrich Barth, Adolf Overweg, Gustav Nachtigal and the Frenchman Henri Carbou that the dialect of the Chadian Arabic language in the region Waddai systematically explored.
The types of climate in the Chad Basin is divided by vollaridem climate in the north, characterized by deserts, on semiradies climate in the zone of the Sahel to Semihumides climate in the area south of Lake Chad and vollhumidem climate in the mountainous regions of Nigeria, Cameroon and the Central African Republic.
The Lake Chad basin is located in the zone of the Intertropical Convergence Zone, ITCZ for short, this extends from 15 degrees north to 15 degrees south latitude. The seasonal shift of the ITCZ results for the region, separation into rainy and dry seasons. Rainfall is generally from April to October in the south and from July to September in the northern part of the basin, at this time the region is under the influence of south-west monsoon. In general, the rainfall from July to September to fall from the most productive. The average rainfall in Chad basin is very unevenly distributed due to the climatic conditions. The Southwest recorded 1600 mm per year on average, the north, however, less than 150 mm per year. The evaporation rate is very high at 2300 mm / year.
The effect of the south-west monsoon on the basis of average monthly flow of the river Chari measured at the hydrological station of N'Djamena ( in m³ / s) ( Calculated using the data for a period of 58 years, 1933-91 )
In the dry season the months of November to March, the Chad basin is under the influence of the north-east trade winds from the Sahara, these are called Harmattan.
In July, average daytime temperatures throughout the territory of the Chad Basin around 30 degrees Celsius, in the more northern regions they reach 35 to 40 degrees Celsius.
The regions in the Chad Basin have repeatedly experienced in the past, the absence of the south-west monsoon, this led to the great drought of the years 1972-74 and 1983-84 with the well-known famines for the population in the affected areas.
The potential evaporation is generally very high in the Chad Basin and reaches its peak in April and May, when the humidity saturation deficit is high and it is reduced in July and August with the arrival of the rainfall of the West African Monsoon. Below is a brief increase in September and October and then falls to a minimum in December and January when the air temperatures reach the annual minimum in the region. The mean annual evaporation rate increases to the north by about 60 mm per degree of latitude, in the areas south of the Chad Basin. In general, the potential evaporation varies from 1500 - 1800 mm per year over the area in the north- eastern Nigeria. It rises to 2,300 mm / year in the north- east of Lake Chad and up to 6,000 mm / year in the desert lowlands in the north-eastern part of the basin.
The West African monsoon
The West African monsoon (WAM ) is a coupled atmosphere-ocean - land system, which in the summer rainfall and winter drought across the continent. The processes in this system over the land, the sea and the atmosphere are characterized in the interacting space and time scales.
The investigations of the West African Monsoon Multidisciplinary Analysis project ( AMMA ) have shown that the influx of cold water in the Guinean Gulf plays a crucial role in this system, at the beginning of the monsoon season. Similar to the meteorological conditions in the Mediterranean or in the Indian Ocean are the water temperatures as the key factors in the variability and the retreat of the monsoon rainfall in autumn. The annual cycle of sea surface temperature in the Gulf of Guinea is asymmetric with a rapid cooling of the highest water temperatures in April to the lowest water temperature in August and a gradual increase in the water temperature up to next April. The rainfall over West Africa and Chad basins are significantly characterized by the pre- guiding air masses, leading to a horizontal movement of air above the marine boundary layer to the different temperature anomalies over West and Central Africa. With the development of high air pressure at sea level and the development of the surface wind to an anomaly in the intertropical convergence Secondary is promoted. The studies also showed that the seasonal changes of sunlight control the seasonal changes and leads to a net increase in the amount of energy in the atmospheric column. This excess energy leads to a horizontal energy exports, by which the thermal circulation of humid air masses is excited to a collection of thermally charged humidity in the range of the ITCZ. This process is modulated in Germany the yield of precipitation.
The variability of the WAM in the last few decades is not really clear, it shows on the one hand an increase in water temperatures in the Gulf of Guinea, but also a change in the time- spatial sequence of the triggering mechanisms of the monsoon. A change in the ITCZ is also not excluded, but studies on this are still lacking at present. However, the results of these changes are measurable, the Isoheyt lines migrated in the last 50 years by about 200 km to the south, which led to a significant decrease in rainfall in the Chad Basin.
From the climatic history of the Chad Basin only the age of the younger Quaternary has been sufficiently explored, as a result of since the beginning of the Quaternary period, the prevailing Flächenumbildung and the beginning of the hull surface fragmentation were detected by neuentstandener river valleys. The impact of the frequent changes of warm and humid pluvial and desert-like Interpluvialzeiten on the relief have been explored, however, because of a lack of radiometric age determinations and the lack of datable traces preserved as well as due to the extinction of older relief states.
Evidence can be a Altdünenzone, Erg Ancien called up via expanded to today's 800 mm isohyet line and indicates an extremely arid climate until about 40 000 years ago. It joined a wetter phase of at 40000-20000 years ago. This humid phase was followed by a period of extreme drought, Ogolien and Kanemien called, which lasted until 12 000 years. Called dunes advances, Erg Recent, up to the present 500 mm isohyet - line have been assigned. Years ago, about 10,000 known wet time began, also called Tschadien, which was separated 7500-7000 years ago by a drying phase of. It came from before 9000-5000 years to two phases in which the Lake Chad reached a much greater extent than today. The Paläotschadsee covered thereby also the north of the present-day Republic Chad. The sea borders can prove this by the dark brown sediments were deposited in a former bank area, they are now a few decimeters thick.
From a short wet period of 3500-2500 years ago, with a shallow lake and Sumpfseebildung, interrupted, there was an increase in aridity to small variations until today. This resulted in the Sahara, but also partly in the Sahel to remobilization of sand dunes up to the present time.
Air carousel of the last 1000 years
The climate of the last 1,000 years in the Chad Basin oscillates between Arid to Semi-Arid in the zone of the Sahel and Semi-Arid to Humid in the zone of the Sudan United landscape. This change was made in different lengths of time scales, which took place from about 1700 AD, the oscillation in ever shorter time scales. Only in the period from about 900 AD are also written sources about the Chad Basin and the Kanem -Bornu destination description of, in Arabic records, including conclusions about the climatic conditions could be drawn.
So could evaluations by the written Arabic sources and guided by core drilling on and were determined in Chad that the climate until about 1150 AD predominated in the Semi-Arid Sahel to subhumid with a reduced evaporation potential. In the zone of the Sudan United landscape prevailed to this time humid climates. The Lake Chad was at this time a size of 36,000 km ², of Seelevel was about 286 meters above sea level.
It was followed until about 1300 AD a period in which an increasing aridity was observed. After a short recovery period, until about 1380 AD, culminating this change to about 1450 AD, when the southern basin of Lake Chad dried up. Written sources are reporting a severe drought in this period, up to about 1480 AD stopped.
Until 1520 AD, the climate recovered in the Chad Basin and precipitation increased, then the climate switched back to an arid climate trend. Written sources report for the period 1541 to 1562 AD by the great famine Bu Ihagbana and 1563-1568 of the famine Zima Azadu. The climate rebounded to about 1610 AD, this was evident by the expansion of Lake Chad, this covered until about 1700 AD, again an area of 36,000 km ². During the same period, however, report written sources of several long-lasting droughts and famine. Thus, a dry period in the years 1639-43 was recorded, reported from 1644 to 1680 by the famine Dala Dama and 1681-1684 a new dry period on the territory of today's state of Borno was recorded.
Accordingly lie from these periods always been reports of a southern migration in the dry phase and a northern migration of the population in the more humid phases. In the mid -17th century is reported by Kreda strain of Tubbu - people that they emigrated completely and permanently in the hills of Kanem from the region Borkou.
As initially mentioned takes the oscillation of the climate to from about 1700 AD, the Lake Chad reached the 284 meters mark rarely even, in some extreme years, the water level of the lake was so low, that the Grand Barrier divided the sea, as in the decade of 1830. few years, from 1901 to 1915 and from 1973. the Grand Barrier falls from a surface level of the lake from 280 meters dry.
In the decade from 1720 to 1730 several droughts and famines are recorded. From 1738 to 1756 report sources of the great drought in the southern Chad Basin. The Arid phases in the Sahel are at this time getting longer and accordingly is the change from semi-humid to humid climate phases in the Sudan United landscape in ever shorter time scales, the duration of the semi-humid phases steadily extended and spoken 1900 only to semi-humid climate conditions can be.
Written sources report 1790-1810 of several dry periods, this pattern was repeated 1828-39; several famines were recorded in the latter period. At the beginning of the colonial period, from 1898, was a great drought in north-east Nigeria by British colonial authorities reported that lasted until 1915. From the French colonial authorities a great famine in the years 1940-49 was recorded. The climate then stabilized until the middle of the 1960 decade on a semi-arid climate level in the Sahel.
From the mid- 1960 decade, one can speak only of an arid climate in the Sahel. The corresponding consequences were the big dry periods 1969-74 and 1983-87, which were received in each case as Big Dry and famine in history. Lake Chad as a climate indicator decreased its size of 23,000 km ² (1962 /63) on approximately 1,100 km ² in 1994, then there was a slight increase in size to 1,350 km ² by 2001, since then the Seegröße stabilized at this level. Occur in some years repeated heavy rain events on, but mostly new hunger crisis, as in 2005 in the southern Niger and 2010 in the western Sahel, led.
In Chad Basin are two major river systems, the Chari - Logone and of the Komadougou Yobe, as well as some of the smaller rivers and wadis. In this large region is home to a variety of lakes, of which Lake Chad, the Nguru Lake and Lake Fitri are the most famous and have a national significance. Numerous lakes in the region are additionally protected areas required under the Ramsar Convention, as the Maladumba Lake. But the lakes in northern Chad basin, such as the Mare de Zoui offer unique flora and fauna habitats to survive in the arid climate of the Sahara. The lakes in the south of the basin are mainly linked to the fishery for the local population of meaning as the Bomboro - Lake Mamoun and the Lake. Lakes, such as Lake Fianga are unique, because it's on a watershed and drains into two different river systems. About the seasonally occurring Mare de Tizi contrast, little is known.
The Chari - Logone river system has a catchment area of 650,000 km ², ranging from the highlands of Adamawa up in the Darfur region of Sudan. The river system is under the influence of the tropical climate in the highlands of the North Equatorial threshold and has a single flood season, which inundate the wetlands of the Yaeres in the Waza - level in the months of August to November in part. The average discharge of this river system in the Lake Chad is indicated 37.8 km ³ / year.
In the highlands of Adamawa rivers Yedseram and Ngadda spring which also strive towards Lake Chad, but no longer reach him since the droughts of the 1960s and 80s. The Yedseram and Ngadda to flow at its upper reaches 130 km ² Sambisa swamps, thereby forming a flow system because the Ngadda receives a significant portion of its annual runoff from Yedseram.
The Springing in the Mandara Mountains El Beid is the most water-rich Nigerian river in the region. He receives a substantial part of its annual runoff from the drying off Yaeres, in the south of Lake Chad. His course of the river forms the border between Cameroon and Nigeria to reach the former shoreline of Lake Chad to more than 400 km.
The catchment area of the Komadougou Yobe has a size of 148,000 square kilometers and extends into the area of Kano, the headwaters of the Hadejia and the Bauchiplateaus, the headwaters of the Jama'are in Nigeria. The area behind the the confluence of two source rivers Hadejia - Nguru is designated as wetlands and has a maximum extension of 6,000 km ², beginning in late August with the onset of flood season. The Komadougou Yobe no longer reaches the open waters of Lake Chad and flows about 120 km off the coast of today's line in an inland delta with no outlet.
In the north and east of the Chad Basin there are only a few wadis that lead time or seasonal surface water. Worth seeing, the coming out of the Darfur Wadi Kaya. The also the Darfur springing Wadi Bahr Azoum seasonal forms a part of the Chari - Logone river system. The current coming from the Tassili n'Ajjer Wadi Tafassassed and reaches the northern edge of the Ténéré desert.
In the region of Tibesti Mountains wadis are called Enneri. Five major Enneris flow north into the region Sarir Tibesti in Libya, where the water runoff is dependent on the spreading rate of precipitation. Thus, a water discharge rate of 453 m³ / s in 1954 were measured at Enneri Bardargué. This flood peak was followed by four years with an average discharge rate of 5 m³ / s and 1963 he reached three flood peaks with 4, 9 and 32 m³ / s To the south, dehydrate temporarily filled with water Enneri Touaoul, Tegaham, Enneri Wed, Enneri Ké and irrigate the surrounding desert areas. The Touaoul and Ké flow together in the south of the Tibesti and form the Enneri Miski who does flow into the Borkou level.
The wadis, which spring from the Ennedi Massif are regionally called the Quadi. They form an extensive drainage system that extends to the highlands Wadai around the city of Abeche. The largest is the Quadi Batha, he reached to the west of the Lake Fitri.
The to the region around the oasis Safi reaching Wadi Bahr -el- Ghazal is also regionally known as the Soro. He reached the eastern edge of Lake Chad. He is not a wadi in the traditional sense of the lake supplies water, but there is an overflow channel of Lake Chad. The Bahr -el- Ghazal is flooded when the Seelevel Chad reached the mark of 286 meters above the sea level.
To the west of the basin of the valley Dilia or Dilia de Lagane is called. In the age of the Tschadien Dilia de Lagane led permanently water to Lake Chad, today Dilia de Lagane leads only water during heavy rainfall in the southern Termit massif, but does not reach the Tschadeesee.
Lake Chad is the biggest lake in the Chad Basin and has a long history behind it, which can be characterized " the small Lake Chad from the Mega - Chad " with the words. At its greatest extent it reached in Tschadien, about 10,000 to 5,000 years ago, and covered an area of approximately 350,000 km ². This can be seen in the sedimentation areas and the beach ridges are still visible today.
The size of Lake Chad has up to the present day constantly changing. It included 1962/63 still nearly 23,000 km ², it shrank to 1985 on approximately 3,000 km ². The shrinkage of the lake in the modern age is related to two factors: firstly, the average annual rainfall since the sixties has declined by about a quarter, on the other hand, the abstraction of water for agricultural projects on the tributaries has increased constantly. 90% of the amount of water supplied to the lake from the river system of the Logone - Chari, only 10% by local rainfall and the Nigerian rivers, where water is removed also by the increasing agricultural use. The water level has its annual low point in July, then rises in the rainy season slowly and peaked in December.
The Lake Fitri is located at coordinates 12 ° 41' -13 ° 00'N / 17 ° 24' -17 ° 38'E, about 250 km east of Lake Chad. In the vernacular, it is also called little brother of Lake Chad, with whom he was associated until 5,000 years. It covers an area of 300 sq. km with a maximum extension of 35x20 km with an orientation from northwest to southeast. He is part of a 1950 km ² large biosphere zone. The Fiti Lake is classified in the category of freshwater Sahelian lake and have low salinity. It is fed by seasonal rainfall and the inflow of 3-4 months Batha flowing with fresh water. In contrast to Lake Chad is one of the few Fitri Sahel waters that have not experienced a hydrological change through large-scale irrigation systems. Although he has repeatedly dried up in the past, as in the years 1901, 1973 and especially during the severe drought from 1984 to 1985.
The Iro - Lake is a small lake, 15 km long and up to 7 km wide and is located at 10 ° 05'N / 19 ° 25'E, about 5 km north of the Bahr Salamat, with whom he more or less continuous at flood is connected. At low tide it is about 387 m above sea level and has an area of nearly 100 km ². A continuous flood zone is located between the lake and the river, but the northern shore are not flooded extensively. The lake is bordered by a dense herbaceous vegetation along their banks.
The lakes in the Kanem region
Several smaller lakes are permanent immediately east of Lake Chad, in the dunes of Erg Kanem, where the water table reaches the surface and forms these lakes in the hollows between the dunes. In the past pluvial periods they were a part of Lake Chad and clays were deposited on the lake bottom from. The three Djikare lakes are closest to Lake Chad. The largest lake is Bodou, about 71 km north- west of Bol and 11 km inland "normal" from the shores of Lake Chad. It has an area of 40 ha and a maximum depth of 2 m. Its water is highly saline, due to the high evaporation rate. The two Moilo lakes are about 31 km north-east of Bol, and each have areas of about 60 ha and lows near 2 m. The Rombou lake is located about 70 km northeast of Bol. It covers an area of 15 ha and is about 1 meter deep. Direct precipitation over the lakes is less than 300 mm per year and the sunshine is on average 3000 hours / year, while the potential evaporation is about 2300 mm per year. These lakes are surrounded by lush vegetation.
Southeast of the Tibesti Mountains on the edge of the Mega - Chad Basin, the area of the lakes is Ounianga, these are located on a NW- SE axis. This area is occupied by a sandstone structure and at his feet are a number of permanent salt lakes at altitudes near 402 m above sea level. sea level. These lakes owe their existence to the fact that water from an underground aquifer reaches the surface and emerges in depressions between sand dunes.
The most important lakes are at Ounianga Kebir (19 ° 05 ' N/20 ° 31 ' E), the largest lake in it the Joa - sea (345 m asl) has an area of 370 ha, with a maximum depth of 25 m. In its immediate vicinity the lakes Uma, Mioji and Forodom lie. A second group of lakes is situated about 50 km east at the oasis Ounianga Serir (18 ° 55'N / 21 ° 51'E ). Here are ten lakes in rough rugged country in parallel. These are the lakes Melekoui, Dierke, Ardiou, Teli, Abrome, Hogou, Diara, Tarem, Tibichei and Bokou. The Teli Lake is the largest, and occupies an area of about 70 ha, with a maximum depth of 10 m. The lakes are aligned on a North-East -West axis, their long axes are parallel to the prevailing wind direction.
The Chad Basin can be divided into nine different vegetation zones. These offer a wide variety of habitats for a variety of animal and plant species. So there are vast deserts, thorn bush savanna, savannah, rivers, lakes, wetlands and extensive mountain regions with a large variety of flora and fauna. An example is the Chad Basin all large African animals such as hyenas, lions, elephants, hippos, cheetahs, crocodiles and ostriches. Lake Chad with its tributaries and its wetlands creates a unique ecosystem of global importance. This not only provides native wildlife habitat but serves migratory birds from the northern hemisphere resting and hibernation options on their train routes. In addition, this vast ecosystem provides an effective protection against the spread of deserts.
Sahara vegetation zone
The surface of the vegetation zone Sahara in Chad Basin is characterized by vast deserts with sand dunes, Erg, Chech or Raoui called large stone and rocky deserts with their vegetation -free plateau, Hamada's called, called large gravel plains, Reg, dry river beds, the wadis and large flat salt beds. The precipitation in these areas can be less than 25 mm per year. The average annual temperatures are around 25 degrees Celsius and can rise during the summer months to over 50 degrees Celsius.
The flora in these areas is very poor in species and includes about 500 plant species of which about 162 are endemic to the Sahara. They grow mainly in the wadis, oases, hills, valleys and rivulets on individual groundwater lead areas.
The fauna in the Sahara is much richer in species than previously thought, most to observe insects and arthropods are, but also a few mammals and reptiles are found in this region. On bird species are in the Sahara desert and the Alaemon alaudipes Sparrow (Passer simplex) home.
Tibesti - Jebel Uweinat mountain desert vegetation zone
The mountainous region of Tibesti belongs to the category arid desert climate. The annual rainfall is indicated because of its height below 600 mm per year, but it can absorb and store this moisture exist little to no floors, as these are classified as aridisole desert soils. The known maximum temperatures are around 30 ° Celsius in the lowlands and 20 ° Celsius in the high altitudes of the mountains. In the winter months, however, this drops to about 12 ° in the lowlands and 9 ° C in the high altitudes.
The vegetation in the mountains of Tibesti varies with the altitude and slope. In the southwestern mountain slopes are the wadis Enneri Tegaham, Enneri Wed, Enneri Ké which lead surface water at greater precipitation and growth of trees such as the Doumpalme ( Hyphaene thebaica ), the toothbrush tree ( Salvadora persica ), tamarisk ( Tamarix articulata ), the Anabaum ( Acacia albida ) and other tropical plants, Abutilon, Hibiscus, and Tephrosia allow.
In the higher elevations of the mountains rising to the south and southwest slopes of the endemic Ficus teloukat, on the western slopes of the Myrtus nivellei and on the northern slopes of the Tamarix gallica nilotica.
At larger mammals occur the Dorcas gazelle ( Gazella dorcas ), the Barbary sheep (Ammotragus lervia ) and the cheetah (Acinonyx jubatus ) in the mountains. Populations of smaller mammals include rock hyrax ( Procavia capensis ), the Kaphasen (Lepus capensis ) and the spiny mice ( Acomys spp.).
West Sahara desert mountain vegetation zone
This vegetation zone of the Chad basin is determined by the topography of the mountains Tassili n'Ajjer and the Aïr. The climate of this region is described as hot and dry in summer and cold and dry in the winter months. The annual rainfall is given as 150 mm. The temperatures reach 30 ° C in the lowlands and 12 to 18 ° C in the higher elevations of the mountains, and ground frosts occur in the fall and snow can in the cold winter months. In the mountains there are Gueltas the permanent lead water in narrow gorges and secure by their low evaporation rate of flora and fauna in this otherwise barren mountains survival. In the oases of the Aïr also an extensive garden restaurant will be operated.
The flora in this vegetation zone is determined by the surface of the land. In the plains extended Regs, Hammadahs and numerous wadis are around which are grouped the vegetation. At higher altitudes the vegetation image changes into a Sahara mountain vegetation with rare and largely endemic plants and tree species, some of which relics of the past, the humid Sahara region. This mainly affects the Duprey cypress, the Tarout (Cupressus depreziana ), the wild olive ( Olea lapperrini ) and the myrtle ( Myrtus nivellei ).
The fauna of this vegetation zone is very diverse, so live populations of Dorcas gazelle ( Gazella dorcas ), the Dama Gazelle ( Gazella dama) on the plateaus of the mountains. Migratory birds from Europe use this region as a resting and wintering area. There are also many reptiles such as the Slender Blind Snake ( Telescopus obtusus ) or the white-bellied sand race Lotter ( Echis leucogaster ). Also amphibians, such as the green toad (Bufo viridis ) are found in this region.
South Sahara grass and shrub savannah
The vegetation zone of the Southern Sahara grass and shrub savannah is a dry savanna, also a border country and a transit zone between the Sahara and the Sahel acacia savannah, it is about 100 to 200 km wide. Rainfall is abundant here than in the Sahara and be between 100 to 200 mm per year.
The flora is determined in the north of this region by seasonal savannas can in the summer, favored by rainfall from July to September, grow. They consist mainly of the love grass ( Eragrostis ), Aristida and the dune grass ( Stipagrostis ). Interspersed these savannas are with the herbs and shrubs, such as Tribulus, Heliotropium and Pulicharia. Mainly grown in the wadis and areas with aquifers in this ecoregion the screen (Acacia tortilis ) and the Acacia ehrenbergiana. In the south, this region also Rispenhirsen ( Panicum turgidum ) grow.
In this region live next to the ostrich (Struthio camelus ), larger mammals such as the Addax ( Addax nasomaculatus ), the dunes Gazelle ( Gazella leptoceros ), the Dama Gazelle ( Gazella dama), the striped hyena ( Hyaena hyaena ), the cheetah (Acinonyx jubatus ), the African Wild Dog ( Lycaon pictus).
Sahelian Acacia savanna
The vegetation zone of the Sahel acacia savannah is a dry and thorn shrub savannah. It follows on from the South Sahara grass and shrub savannah and includes most of the Chad Basin. The topography in this ecoregion is generally flat, with no major bumps or mountains. The rainfall varies from 200 mm per year in the northern area of up to 600 mm per year in the southern part of the region. The monthly maximum temperatures range 33-36 degrees Celsius, the lowest temperatures reach 18 to 21 degrees Celsius in the cooler months. The young and thin topsoil is no discernible stratification and meets the Entisol floors of the USDA soil classification, these cover the largest part of this region, in the northern part change this off with Aridisol soils, surface water is only seasonally available in the rainy season.
The flora in this region is a mostly tree grown by savanna, interspersed with thorny bushes. The grassland is dominated by the one-year short grasses Aristida mutabil, Chloris prieurii and Cenchrus biflorus.
In this ecoregion, a larger number of endemic animal species. Among the birds is the rust Lark ( Mirafra rufa), the mask Shrike (Lanius nubicus ) and the Sudan Beutelmeise ( Anthoscopus punctifrons ) endemic to this region. Beginning of the 20th century there were in this region large stocks of elephant, the West African Giraffe (Giraffa camelopardalis peralta ) and the ostriches, but these were heavily hunted, so significant holdings were only able to survive in national parks and other protected areas. The scimitar-horned oryx once occurring in large flocks (Oryx dammah ) is now regarded as possibly extinct.
Lake Chad flooded savanna
The Lake Chad flooded savanna located in the zone of Lake Chad and the adjacent floodplains its tributaries. The lying areas in this flood plains and wetlands cover an approximate area of 2.5 million hectares and have a great far beyond the Chad Basin also reaching significance. The vegetation zone consists of a variety of surface forms, so there are small groups of islands, large wetlands, reed grass savannas and large open water surfaces in the region of Lake Chad and permanent grass savannah and seasonal savannas, such as the Yaéré. The more commonly used in this region term " Sudd " means a permanent flood plain.
Lake Chad is divided on a north and southern basin. The northern basin has an approximate depth of 6 meters and is currently (2011) only seasonally flooded with water of Komagoudou Yobe. The southern basin has a depth of about 2 to 3 meters and is currently covered only in the core area of the tributary of the Shari with a permanent open water surface.
The flora in this vegetation zone of the southern lake basin is determined by the large areas with the genuine papyrus ( Cyperus papyrus ), Phragmites the mauritianus, Vossia cuspidata and other marsh plants are covered, the riparian vegetation. On the open water of the lake swim the water lettuce ( Pistia stratiotes ), and covers a large area of the lake. In the area of the northern lake basin the reed (Phragmites australis) and Typha australis dominate the vegetation.
The waters of Lake Chad can be described as tropical waters with low salinity, which is rich in phytoplankton and a large diversity of algae and fish. Thus, more than 1,000 different species of algae and more than 140 species of fish were counted in open waters.
Seasonal, during the rainy season, growing in the southern shore region called Yaéré - grass savannas. This is dominated by Echinochloa pyramidalis which, Vetiveria nigritana, Oryza longistaminata and Hyparrhenia rufa. The Yaéré vegetation dies in the dry season. In the wetter areas of the Yaéré the so-called ' Karal' or ' Firki' tree savannas grow. The tree stands are dominated by seyal (Acacia seyal ) on the hills and the Acacia nilotica in the valleys. The plant surface in this tree savanna is formed by up to 2 to 3 meters tall herbs and grasses, such as the Caperonia palustris, Echinochloa colona, Hibiscus asper, Hygrophila auriculata and Schoenfeldia gracilis.
Western Sudan savanna
The Western Sudan savannah is a savannah and covers the southwestern areas of the Chad Basin in the states of Nigeria and Niger. There is a flat country with no major surveys which is separated from the Eastern Sudan savannah by the Mandara mountains in the highlands of Cameroon. The temperatures in the summer can reach 35 to 40 ° C and winter 15 to 20 ° Celsius. The annual total precipitation in this region varies from 600 mm in the north to 1600 mm per year in the southern areas of this ecoregion. The soils are moderately fertile and subject to a lateritic weathering in this region.
The flora in this vegetation zone is characterized by loosened and far- permanent forests that are interspersed with forests and bush are underlaid with an understory of grasses and broad-leaved herbs langhalmigen. Along the rivers to gallery forests lay out.
In the Western Sudan savannah live a large number of different animal species, many of which are endemic in this savanna landscape. Larger populations of the bush block ( Tragelaphus scriptus ), the warthog ( Phacochoerus africanus), the Ethiopian Vervet monkey ( Chlorocebus aethiops ), the savannah monitor ( Varanus Exanthematicus ), the Anubispavians (Papio anubis ) and the Mantelpavians (Papio hamadryas ) live in this ecoregion. The once large stocks of African mammals such as the elephant, survive only in protected areas.
Eastern Sudan savanna
The Eastern Sudan savannah is a dry savannah and spreads out to the south of Chad and the north- west of the Central African Republic. Its topography is characterized by a pronounced lowland, without major surveys. Its climate is characterized by a dichotomy between dry and rainy season. The highest temperatures may vary from 30 to 33 ° C and the lowest 18-21 ° C. The annual rainfall varies from 600 mm in the north to 1,000 mm in the southern part. The soil quality, according to the USDA soil classification, ranging from Entisol - over to Alfisolböden Ultisol - up.
The flora in this vegetation zone is similar to the Western Sudan savannah with its loosened and far- permanent forests, which are also interspersed with bush forests and are backed by an understory of grasses and broad-leaved herbs langhalmigen. However, it differs in that the trees mostly shed their leaves in the dry season and wither the grass areas. The tree stands are dominated by Anogeissus leiocarpus, the Kigelia aethiopica seyal Acacia (Acacia seyal ).
The fauna in this vegetation zone is characterized by a variety of intact populations of larger African mammals groups. In contrast to the Western Sudan savannah, the number of endemic species is low, only a kind of mouse goundae Mus, and two reptile species, the beak nose snake Rhamphiophis maradiensis and Panaspis wilsoni are endemic. At large mammals wild populations of the African Elefantes (Loxodonta africana), the African wild dog ( Lycaon pictus), the lion (Panthera leo) and cheetah come before (Acinonyx jubatus ).
Northern Congo forest - savanna vegetation zone
This vegetation zone includes the northern areas of the North Equatorial emerging in the Central African Republic ( CAR) and the Highlands in Cameroon and corresponds in its classification of a humid savanna.
It is a narrow transit zone between the Congolese rainforest areas and the Sudan / Sahel savannah. The northern Congo forest - savanna vegetation zone forms the northern forest-savanna landscape of the African continent with a large number of different ecosystems. The annual precipitation amounts range 1200-1600 mm. In the rainy season the temperatures reach 31 to 34 ° C and in the dry season are the minimum temperatures at 13 to 18 ° C. The soils in the CAR are described as not withering Entisol floors and in Cameroon due to its mountainous location as Oxisol - Ultisol to floors.
The flora in this vegetation zone is determined by its character as a transit zone between the Sahel and the rainforest. The tree stands is dominated by the genus Isoberlinia spp.
The fauna is very diverse and is characterized by a moderate biodiversity. In this zone, larger populations of African Elefantes (Loxodonta africana), the Black Rhinoceros ( Diceros bicornis), the giant eland ( taurotragus derbianus ) and in the eastern sector of the Bongo (Tragelaphus eurycerus ) occur.
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- S. Kropelin, D. Verschuren, A.-M. Lézine, H. Eggermont, C. Cocquyt, P. Francus, J.-P. Cazet, M. Fagot, B. Rumes, JM Russell, F. Darius, DJ Conley, M. Schuster, H. von Suchodoletz, DR Engstrom: Climate - Driven Ecosystem Succession in the Sahara: The Past 6000 Years892 kb PDF format published in Science Magazine May 2008 Volume 320, Issue 5877
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- Tibesti - Jebel Uweinat montane xeric woodlands on WWF 's website
- Sahara desert on WWF Website English
- West Saharan Montane Xeric Woodlands on WWF Website English
- The Sahelian Acacia Savanna on WWF Website English
- West Sudanian savanna on WWF Website English
- East Sudanian savanna on WWF Website English
- Northern Congolian Forest -Savannah Mosaic on WWF Website English
- Chad information on BirdLife International 2.20 MB PDF format English
- Niger Country Information on English BirdLife international496 kb PDF format
- Central African Republic information on BirdLife International 432 kb PDF format English
- Studies on Cultural Studies No. 121, Published by Matthias Krings and Editha plate: Living with the Lake ( English), Rüdiger Koppe Verlag Köln ISBN 978-3-89645-216-0