Lake Victoria

Geography

Topography

Lake Victoria is located in East Africa, in the middle of the African big lakes. Crossed by the equator in North, its Coastal states are the Kenya in the North-East, the Uganda in north and the North-West and the Tanzania in the south. Of relatively low depth (40 meters on average, 83 meters to the maximum) and located at 1 133 meters of altitude, the lake occupies a depression formed by movements Tectonique S and framed by the two branches of the Vallée of the great rift formed four million years ago.

Coarsely rectangular with 320 kilometers length (of north in the south) and 275 kilometers of width (of is in west), the lake has very cut out banks formant of many Péninsule S, Presqu'île S, bays, courses and more 3 000 island S, majority uninhabited.

Geology

Four million years ago, the rift Est-africain starts to constitute by the play of normal faults which form Horst S and Graben S organized on two parallel axes. The light rising of the edges of its rifts causes the formation of a depression little marked in the eroded grounds Précambrien S located between them. Certain rivers, captured by this basin, then started to fill it between 750 000 and 400 000 years, giving rise to Lake Victoria.

The low depth of the lake and his strong report/ratio surfaces/volume make it vulnerable to the climate changes. The geological Carottage S realized in the Sédiment S showed that Lake Victoria was drained at least three times since its formation. These cycles of draining are probably related to the Glaciation S during which the Précipitation S decreased overall. The last draining of the lake goes back to 17 300 years and its filling with 14 700 years.

Climate and hydrology

Lake Victoria is subjected to a tropical Climat whose temperatures oscillate between 16 and 27 °C. From May to July, the winds of the south cause displacements of the water mass towards north. The rains are distributed throughout the year but two wetter periods are distinguished in April and in September - October. The annual average of precipitations rises with 1 450 millimetres.

The Bassin pouring sees a dozen river being thrown in the lake of which the Kagera, most important coming from Tanzania, the Burundi and the Rwanda. The emissary of Lake Victoria, the White Nile ( Bahr-el-Abiad ), runs out towards north to throw in the Lac Kyoga then the Lac Albert and finally the the Nile. The portion of the White Nile located between Lake Victoria and the lake Kyoga is also called the Nile Victoria and would have been born between 12 000 and 14 000 years front J-C. The affluents, whose flow varies much during the seasons, provide less than 20% of water of the lake, the remainder coming from the rains. The losses are partly due to the outgoing flow of the White Nile but also to the evaporation (variable according to the seasons and the wind) which represents a loss from 31 to 124 millimetres per month.

Until in the Years 1960, Lake Victoria was rather well balanced at the hydrological level and did not undergo strong variations of level. In 1962, the level is abruptly assembled following strong rains and was maintained thereafter, although presenting a light reduction. Starting from 2004, a material change started with a reduction in the level of the lake of two meters in two years. The cause of this fall would be the lack of Pluie S which acts as well directly on the lake as on the contributions of the affluents.

Biodiversity

There is 14 000 years, after the filling of the lake, the watery fauna of the rivers colonized Lake Victoria. Having suddenly access to a virgin habitat, the species diversified, occupying all the ecological niches. Thus appeared, according to the current theory, the many endemic species of Haplochromis. After the introduction of the Pole of the Nile, the Eutrophication of water and the invasion by the Hyacinth of water, this Biodiversité strongly decreased. It seems however that certain haplochromis starts to adapt to these new conditions, in particular by modifying their dietary habits.

Fauna

This paragraph will not quote the exhaustive list of the species present around Lake Victoria but will introduce only some families, kinds and outstanding species of the wildlife.

Mammals

In the Marsh with papyrus, the Antelope Sitatunga ( Tragelaphus spekeii ), with the long and split shoes adapted to walk in marshy ground, can still be met although become rare. Another antelope, the Large cobe of the reeds ( Redunca redunca ), can it also be seen on banks.

With regard to the Mammalian S more adapted to the watery lifestyle, the Hippopotamus ( Hippopotamus amphibius ) and the otter with white cheeks of the Cape ( Aonyx capensis ), are current.

In certain drier zones the Impala ( Aepyceros melampus ) lives, mammal resembling a gazelle or an antelope.

Birds

Lake Victoria is a crossing point of very many Oiseau X migrating but it is also the medium of life of a great number of species resident.

In the dense Marshes, many animals find shelter and food. It is there that the Bec-en-sabot saw ( Balaeniceps rex ) which nourishes Poisson S, of Batracien S, young people tortoises and which is currently classified like vulnerable species. One finds there also birds typical of the marshes with papyrus such as the Cisticole de Carruthers ( Cisticola carruthersi ), the Rousserolle of the canes ( Acrocephalus rufescens ), the Gobemouche of the marshes ( Muscicapa aquatica ), the Bouscarle with white wings ( Bradypterus carpalis ) and two threatened species, the watery Chloropète ( Chloropeta gracilirostris ) and the Gonolek of the papyruses ( Laniarius mufumbiri ).

In freer water, one can meet the white stilt ( Himantopus himantopus ) but also of the Cormoran S (Grand cormorant, Phalacrocorax carbo , and African Cormoran, Phalacrocorax africanus ) like various Héron S (the white Crabier Ardeola idae ) and Aigrette S (Aigrette garzette, Grande brush). The Gull with gray head ( Larus cirrocephalus ) and the Sterne Hansel ( Sterna nilotica ) will often meet in the interstitial water zones further away from bank.

In the Savanna raised which surrounds the lake, one can observe the Martin-chasseur of Senegal ( Halcyon senegalensis ), very coloured bird pertaining to the same family as the Martin-pêcheur S. Close to bank, one can sometimes see the œdicnème been vermiculated ( Burhinus vermiculatus ) or the Barbican guifsobalito ( Lybius guifsobalito ), black bird with intense red throat, or even various Souïmanga S, birds nectarivores not to be confused with hummingbirds, of which the Souimanga with red belt ( Nectarinia erythrocerca ). The Around unibande ( Kaupifalco monogrammicus ), raptor amateur of Lizard S, Snake S, small Mammalian S and young people Bird X, is often observed in this Biotope.

Reptiles and batrachians

The Crocodile of the Nile ( Crocodylus niloticus ) almost disappeared from this area of Africa. It is primarily victim of hunting made to obtain its skin. It nourishes alive preys like Oiseau X, lizards, tortoises, Insecte S, Crustacé S, Mollusque S and Batracien S.

With Lake Victoria, the laying has place and in January at the end of December, at the dry season when water drops. The eggs are deposited in sand where they incubate for three months.

The lake shelters several species of endemic fresh water tortoises like Pelusios williamsi or Emydura victoriae .

The monitors of the Nile ( Varanus niloticus ), which undergoes the predation of the crocodile, do not hesitate in return to plunder the nest of this last.

In these zones also batrachians live, in particular a species endémique : Xenopus victoriae .

Poisson

Lake Victoria contains more than 500 species of Poisson S including 300 endemic pertaining to the kind Haplochromis and two endemic species of Tilapia S pertaining to the kind Oreochromis ( Oreochromis esculentus and Oreochromis variabilis ).

The Pole of the Nile ( Lates niloticus ) and the Tilapia of the Nile ( Oreochromis niloticus ) were introduced into the lake by the Man.

There exists also a species of protoptère, or dipneuste African ( Protopterus aethiopicus ), fish pulmoné obliged to breathe regularly on the surface.

Since the introduction of the Pole of the Nile into the Years 1950, more than 200 endemic species of Haplochromis as well as the Oreochromis esculentus disappeared and of many species are threatened as the protoptère which seems even in the process of disappearance.

Insects

Water of Lake Victoria is colonized by watery Insecte S, the Notonecte S inter alia, and by many Larve S of insects. One attends periodically above water of the lake the appearance of true clouds of insects. The latter are formed when the nymph S of certain species (Trichoptère S, Chaoborus , Simuliidae , transitory S, Odonate S, Chironome S, Moustique S, etc) are transformed into adults and take their take-off. The majority are inoffensive but can be awkward for the inhabitants of the vicinity.

Certain mosquitos can transmit diseases such as the Malaria, the fever with Chikungunya and the Yellow fever. On banks, periodic gatherings of heads of cattle attract the glossine, or Tsetse fly, able to transmit the Maladie of the sleep of which the person in charge is the Trypanosome (Protozoaire). The Simulie S can they also transmit diseases to protozoa (Onchocercose, Filariose).

Other arthropods

The Crustacés are numerous in Lake Victoria. One finds many species of Copépode S ( Cyclops , Diaptomus , etc), of Ostracode S and Cladocère S ( Daphnia , Bosmina , Leptodora , Chydorus , etc).

It seems that there was a drastic change in the proportions of shellfish species forming the Zooplancton Lake Victoria during the 20th century. The species of Copépode S about the Cyclopoida increased by 8% to 97% of the biomass between 1927 and 1990 whereas the Copepoda about the Calanoida (like Diaptomus ) and the Cladocère S decreased by 50 and 40% in 1927 up to 2 and 1% in 1990. This modification is perhaps due more to the Eutrophisation of water that to the modifications of the predatory fauna of the lake.

One finds also two species of endemic higher shellfish of the région : a Shrimp ( Caridina nilotica ) and a Crab ( Potamonautes niloticus ).

Other invertebrates

The Mollusque S are them also many with 126 species and under species in the lake of which some are endemic : Gastropodous S ( Crushed ovata , Bellamya unicolor , Biomphalaria glabrata , Melanoides tuberculatus ) and Lamellibranche S (kinds Pisidium , Mutella , Coelatura and Sphaerium ).

Lake Victoria lodges some species of Annélide S, Sangsue S and Oligochète S (like Alma emini ) and of the Rotifères (kinds Brachionux and Anuraenopsis ). A endemic jellyfish of fresh water, Limnocnida victoriae , is also present in the littoral zones and of the sponge S (like Spongilla nitens ) in the rock habitats.

Flora

This paragraph will not quote the exhaustive list of the species present around Lake Victoria, but will introduce only some families, kinds and outstanding species of the wild flora .

The area of Lake Victoria is currently occupied by wooded Savane S intersected with vast wide cultivated. In North formerly large a Forêt extended which prolonged that of the basin of Congo but there remain nothing any more but scraps about it.

In the marshy zones , on bank or at a shallow depth, one finds various species like Poaceae ( Miscanthus violaceus , Leersia will hexandra ), of the Sphaigne S (kind Sphagnum ), a Melastomataceae ( Dissotis brazzaei ), Roseau X of the kind Phragmites , two-handed hammers (kind Typha ), Potamot S (kind Potamogeton ) and Nénuphar S ( Nymphaea caerulea , Nymphaea lotus ).

Along the banks, with the shelter of the waves, draws up an important vegetation which penetrates until in the mouth of certain affluents. One finds among these plants the papyrus ( Cyperus papyrus ), which reaches four to five meters height. The papyrus pushed all the year all along the Nile a few thousands of years ago but today, one does not find it any more but in the South of the Sudan and around Lake Victoria where it covers great extents. One can also find in the same zones of the ferns ( Cyclosorus interruptus VAr. striatus ), of the ficus (like Ficus verruculosa ) and of the plants of the family of the Limnophyton ( Limnophyton obtusifolium ).

In the calm zones one finds plants watery like the Utriculaire (kind Utricularia ), of the Hydrocharitaceae ( Hydrilla verticillata , kind Vallisneria ), the swimming Mâcre or water sweet chestnut ( Trapa natans ) whose fruit is edible, a Poaceae called hippo fatty , that is to say “grass with hippopotamus” ( Vossia cuspidata ) and plants of the kind Ceratophyllum . All contribute to create habitats for many small animals. The water pistie or lettuce ( Pistia stratiotes ) seems to have disappeared because of the proliferation of another plant, the Jacinthe of water ( Eichornia crassipes ).

The lake undergoes an important phenomenon of Eutrophisation and human origin. For example, the phosphorus rate doubled during the 20th century. This increase is mainly due to the rejection of waste of cutting-up of the Perche of the Nile, carried out on banks of the lake, like with a combined action of overpopulation (as well on the level of the human ones as of the pets) and Déforestation. This phenomenon is undoubtedly at the origin of the demographic explosion of the Bactérie S of the type Cyanobacteria whose population was multiplied by seven since second half of the Années 1960. These bacteria started to form great extents on the surface of the lake in the Années 1980 and can cause the death of fish by consumption of the Dioxygène at the time of their Décomposition.

For several years (1980 and 1990), the lake has undergone a massive invasion of the Jacinthe of water ( Eichornia crassipes ), a watery plant originating in tropical America. This plant blocks the progression of the boats, obstructs fishing and the hydroelectric production of energy, pollutes the drink water and causes the disappearance of fauna in certain zones. It obstructs the passage of the light indeed, preventing the development of green algas whose certain fish species are nourished, prevents the oxygenation of water surface and its decomposition consumes such a quantity of Dioxygène that the medium quickly becomes Anoxique. A programme of elimination of the plant is in hand, utilizing primarily a collecting of the plant and an attempt at introduction of Charançon S ( Neochetina eichhorniae and Neochetina brushi ) nourishing water hyacinth. In 1995, 90% of the coast of the Uganda was covered by the plant but the fight against the plant starts to bear its fruits. If it is possible to reach a balance, this plant could be useful because it is able to metabolize the Phosphore in excess. Moreover, because of low content of water of Dioxygène on the level of its roots, it holds the pole of the Nile remotely. One thus met among the roots of water hyacinth, in edge of the interstitial waters, the fish species considered disappeared or in danger which, less demanding in dioxygene, find a refuge there. But when one is inserted in the density of the vegetable carpet, the medium becomes Anoxique and any life disappears.

History

The historical elements dating from the period former to the European discovery of the lake are difficult to recall fault of scriptural sources. One can base oneself, for the study of the “obscure centuries”, on archaeological research , the study Linguistique and Génétique of the current occupants of the area and with regard to the posterior period at the 16th century, on the oral traditions recalling the past of the various lake kingdoms which were established as from this time. The Historiographie of the area informs us about the very ideological turnings and ethnicists which the history in the area with in basic line could take a rather artificial differentiation between two types of populations, stockbreeders “nilo-hamitic” opposed to the “farmers bantous”, with the absolutely dramatic consequences that one knows with regard to the Rwanda.

Prehistory

The Palynologie teaches us that between IIe and thousand-year-old Ier front J-C., the Arbre S and the Roseau X see their surface decreasing with the profit of the Graminée S. One explains this fact by the combined action of a climatic drying which occurs at that time and by the action of the man. At the beginning of the Christian era, one observes an intense human presence on the islands of the lakes and in the valley of Kagera. One associates this population with the age of iron and one characterizes it by the production of a type of ceramics known as dimple bases with the particular geometrical reasons also called Urewe of the name of the site where he was discovered on the Kenyan coast of the lake.

Kingdoms interlacustres

The first scriptural information source which is known to us on Lake Victoria comes from Arab merchants crossing from the coast the Est-africain plate in the search of Or, Ivoire and slaves. Al Idrissi is, towards 1160, the first to have drawn up a chart clearly representing the lake and the representative as being the source of the Nile. As from the 16th century develop in the area of the big lakes of the centralized kingdoms, several being located on North-western bank of the lake. The kingdom of the Bouganda, with at its head a line of absolute monarchs called Kabaka S, dissociated other kingdoms with the wire of time by its power and formed the framework of current Uganda.

European discovery and colonization

The lake was discovered by the Européens in 1858 when the British explorer John Hanning Speke reached his Southern bank. It named then it name of the Reine Victoria which reigned at that time with the the United Kingdom and in its colonies.

The kabaka of Bouganda, Mutesa, favorably accommodated Europeans and in 1890 signed an agreement with the British East Africa Company to secure German aimings on its kingdom. As from this moment little by little an English Indirect rule in the Northern zone of Lake Victoria was set up while the Germans carried out by Emin Pasha colonized the territory of the German Eastern Africa including/understanding the Southern part of the lake known later under the name of Tanganyika.

The lake was the theater of naval confrontations during the First World War Britanniques opponent and Germans. The German general Lettow-Vorbek who carried out a effective Guerilla against the forces of the Alliance (Belgium, Portugal, the United Kingdom) created a small naval force which was deployed on the lake. In reaction, the British made come from England of the drain-holes dismounted and conveyed by railway to the lake in order to take control of it. The July 17th 1916, they captured two German steamers in Nyanza. Vis-a-vis the disproportion of the forces, the Germans had to withdraw this zone.

Demography

Lake Victoria is located in the middle of a dorsal of settlement corresponding to the African highlands running of the Érythrée to the South Africa while passing by the Rwanda and the Malawi.

Its circumferences densément populated (246 hab/km) contrast with the human vacuums which, with regard to the area of Lake Victoria, correspond to the West with the Congolese basin and in the East with the steppe plate of the Eastern Africa.

The accesses of the lake in addition form a zone of contact between populations of different linguistic groups, on the one hand the speakers of the nilo-Saharan family who populate the South-Sudan, the North of the Kenya and the Uganda and which are found especially in the North-eastern zone of the lake (Luo, Kalenjin) and on the other hand the populations of languages bantoues populating all the Southern Africa and which reach in the zone of the lake their septentrional limit (Ganda, Sukuma, Soga, Luhya, etc).

The residents of the lakes speak the Swahili which is an idiom bantou like Common language. They are mainly of religion Chrétienne, Catholiques and Protestants.

Navigation

Ferries connect the main ports of Lake Victoria, Kisumu, Mwanza, Bukoba, Entebbe, Beautiful Port and Jinja. The first were built with the the United Kingdom and brought into service at the beginning of the 20th century in prolongation of the line of Railroad connecting the coastal town of Mombasa to the Kenya with Kisumu at the edge of the lake. These ferries contributes to the opening-up of the area of the big lakes. In 1996, a steamer, the MV Bukoba sailing between Bukoba and Mwanza and being in overload of passengers ran, causing the death of hundreds of people.

Catalog of films

Lake Victoria was the object in 2004 of documentary largely mediatized, the Nightmare of Darwin , presenting the consequences due to the decline of the Biodiversité of the lake and to the industrial fishing of the Perche of the Nile. This film, which wants to be according to its producer Hubert Sauper an allegory of the Mondialisation and its consequences, received many rewards whose César of the best first film 2006 but also was very criticized for its supposed lack of honesty.

Appendices

List of the Tanzania Lakes

External bonds and sources

Travel medicine Kampala
Convention of Ramsar on the wetlands
List of the birds of Uganda
Lake Victoria shrinks At year alarming spleen
Lake Victoria
Hyacinth of water
the biology of Tilapia nilotica
Living room lake: lake Victoria
African newspaper off ecology, Goudswaard, Witte and Chapman: Decline off the African lungfish (Protopterus aethiopicus) in Lake Victoria (East Africa)
Wanink, Katunzi, Goudswaard, Witte and van Densen: The shift to smaller zooplankton in Lake Victoria boat Be attributed to the “sardine” Rastrineobola argentea (Cyprinidae) , 2002 Ifremer/CNRS/Inra/Cemagref/Editions scientists and medical Elsevier
Christian Jean-Pierre, Africa of the big lakes , Flammarion, 2OOO. Work on the History of the area of the big lakes.

Random links: