95-544: Winam Gulf is a significant extension of northeastern Lake Victoria into western Kenya . Formerly known as Kavirondo Gulf , Nyanza Gulf , and Lake Nyanza Gulf , it is a shallow inlet and is connected to the main lake by Rusinga Channel (3 mi (4.8 km) wide), which is partly masked from the main body of the lake by islands. The port of Kisumu , Kenya's third-largest city, stands on its northeastern shore. The gulf has an average width of 25 km (16 mi) and extends for 64 km (40 mi) from Kisumu to
190-414: A feedback with one another, controlled by oblique rifting conditions. According to this theory, lithospheric thinning generates volcanic activity, further increasing magmatic processes such as intrusions and numerous small plumes. These processes further thin the lithosphere in saturated areas, making the thinning lithosphere behave like a mid-ocean ridge . According to marine geologist Kathleen Crane ,
285-556: A few species are extinct in the wild (only survive in captivity). Before the mass extinction that has occurred among the lake's cichlids in the last 50 years, about 90 percent of the native fish species in the lake were haplochromines. Disregarding the haplochromines, the only native Victoria cichlids are two critically endangered tilapia, the Singida tilapia or ngege ( Oreochromis esculentus ) and Victoria tilapia ( O. variabilis ). In 1927–1928 Michael Graham conducted
380-459: A great deal of intense debate within the scientific community of the day, but also much interest by other explorers keen to either confirm or refute Speke's discovery. In the late 1860s, the famous Scottish explorer and missionary David Livingstone failed in his attempt to verify Speke's discovery, instead pushing too far west and entering the River Congo system instead. Ultimately,
475-649: A number of active and dormant volcanoes, among them: Mount Kilimanjaro , Mount Kenya , Mount Longonot , Menengai Crater, Mount Karisimbi , Mount Nyiragongo , Mount Meru and Mount Elgon , as well as the Crater Highlands in Tanzania. Although most of these mountains lie outside of the rift valley, the EAR created them. Notable active examples of EAR volcanism include Erta Ale , Dalaffilla (also called Gabuli, Alu-Dalafilla), and Ol Doinyo Lengai . Erta Ale
570-401: A pre-Cambrian weakness in the crust, a suture zone of multiple cratons , displacement along large boundary faults, and the development of deep asymmetric basins. The second stage of rifting was characterized by the deactivation of large boundary faults, the development of internal fault segments, and the concentration of magmatic activity towards the rifts. Today, the narrow rift segments of
665-797: A result of the spread of the invasive water hyacinth (an optimum snail habitat), and the loss of many snail-eating cichlids in the lake. Evarcha culicivora is a species of jumping spider (family Salticidae ) found only around Lake Victoria in Kenya and Uganda. It feeds primarily on female mosquitos. Lake Victoria supports Africa's largest inland fishery (as of 1997). Initially the fishery involved native species, especially tilapia and haplochromine cichlids, but also catfish ( Bagrus , Clarias , Synodontis and silver butter catfish), elephantfish, ningu ( Labeo victorianus ) and marbled lungfish ( Protopterus aethiopicus ). Some of these, including tilapia and ningu ( Labeo victorianus ), had already declined in
760-613: A second hydroelectric complex in the area, the Kiira Hydroelectric Power Station , with World Bank assistance. By 2006, the water levels in Lake Victoria had reached an 80-year low, and Daniel Kull, an independent hydrologist living in Nairobi , Kenya, calculated that Uganda was releasing about twice as much water as is allowed under the agreement, and was primarily responsible for recent drops in
855-667: A shallow depression in Africa. The lake has an average depth of 40 m (130 ft) and a maximum depth of 80–81 m (262–266 ft). Its catchment area covers 169,858 km (65,583 sq mi). The lake has a shoreline of 7,142 km (4,438 mi) when digitized at the 1:25,000 level, with islands constituting 3.7% of this length. The lake's area is divided among three countries: Tanzania occupies 49% (33,700 km (13,000 sq mi)), Uganda 45% (31,000 km (12,000 sq mi)), and Kenya 6% (4,100 km (1,600 sq mi)). The lake
950-491: A sieve. The water is then ready to be chlorinated or treated in another way. The sand filtration helps reduce water-borne diseases and is based on the use of the local environment. The only outflow for Lake Victoria is at Jinja, Uganda, where it forms the Victoria Nile. The water for at least 12,000 years has drained across a natural rock weir. In 1952, engineers acting for the government of Colonial Uganda blasted out
1045-583: A water and sanitation project that serves Mwanza and the satellite towns of Lamadi, Misungwi, Magu, Bukoba, and Musoma on the bank of Lake Victoria. European Investment Bank started the project in 2013 with the aim of protecting the environmental health of the lake, through improved water and sanitation to the towns whose pollution is part of the degradation of the lake. The project aims to provide safe drinking water for an estimated one million people and improved sanitation for 100 000 people. Sediment and suspended solids are filtered out using sand, which acts like
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#17327718201011140-469: A west-facing scarp (east-plunging arch) along the southern half of its length that rises to 2,300 m (7,500 ft) above the sea floor. Its movement is concurrent with the EAR. Over time, many theories have tried to clarify the evolution of the East African Rift. In 1972 it was proposed that the EAR was not caused by tectonic activity, but rather by differences in crustal density. Since
1235-436: Is Caridina nilotica , which is common and widespread in Lake Victoria. Lake Victoria is home to 28 species of freshwater snails (e.g., Bellamya , Biomphalaria , Bulinus , Cleopatra , Gabbiella , and Melanoides ), including 12 endemic species/subspecies. There are 17 species of bivalves ( Corbicula , Coelatura , Sphaerium , and Byssanodonta ), including 6 endemic species and subspecies. It
1330-795: Is a basaltic shield volcano in the Afar Region of northeastern Ethiopia, active continuously since at least 1967, with a summit lava lake documented since at least 1906. The 2008 eruption of Dalafilla, its only documented activity since the start of the Holocene , is the largest recorded eruption in Ethiopian history. Ol Doinyo Lengai is currently the only active natrocarbonatite volcano on Earth. Its magma contains almost no silica; typical lava flows have viscosities of less than 100 Pa⋅s, comparable to olive oil at 26 °C (79 °F). EAR-related volcanic structures with dated activity since
1425-583: Is a part of the same river system known as the White Nile and is occasionally referred to as such, strictly speaking this name does not apply until after the river crosses the Uganda border into South Sudan to the north. The lake exhibits eutrophic conditions . In 1990–1991, oxygen concentrations in the mixed layer were higher than in 1960–1961, with nearly continuous oxygen supersaturation in surface waters. Oxygen concentrations in hypolimnetic waters (i.e.,
1520-447: Is a suitable tool to investigate Earth's subsurface structures deeper than the crust. It is an inverse problem technique that models which are the velocities of the inner Earth that reproduce the seismographic data recorded all around the world. Recent improvements of tomographic Earth models of P wave and S wave velocities suggest that a superplume upwelling from the lower mantle at the northeastern EAR feeds plumes of smaller scale into
1615-465: Is being altered and in some cases, broken by the indiscriminate eating habits of the Nile perch. The subsequent decrease in the number of algae-eating fish allows the algae to grow at an alarming rate, thereby choking the lake. The increasing amounts of algae, in turn, increase the amount of detritus (dead plant material) that falls to the deeper portions of the lake before decomposing. As a by-product of this
1710-578: Is generally cool and strong. Many cratons are found throughout the EAR, such as the Tanzania and Kaapvaal cratons . The cratons are thick, and have survived for billions of years with little tectonic activity. They are characterized by greenstone belts , tonalites , and other high-grade metamorphic lithologies. The cratons are of significant importance in terms of mineral resources , with major deposits of gold, antimony, iron, chromium and nickel. A large volume of continental flood basalts erupted during
1805-460: Is home to many species of fish which live nowhere else, especially cichlids . Invasive fish, such as the Nile perch , have driven many endemic species to extinction . Though having multiple local language names ( Swahili : Ukerewe ; Dholuo : Nam Lolwe ; Luganda : 'Nnalubaale ; Kinyarwanda : Nyanza ), the lake was renamed after Queen Victoria by the explorer John Hanning Speke ,
1900-634: Is in remission and this trend could be permanent if control efforts are continued. Pollution of Lake Victoria is mainly due to discharge of raw sewage into the lake, dumping of domestic and industrial waste, and fertiliser and chemicals from farms. The Lake Victoria basin, while generally rural, has many major centres of population. Its shores are dotted with key cities and towns, including Kisumu , Kisii , and Homa Bay in Kenya; Kampala , Jinja and Entebbe in Uganda; and Bukoba, Mwanza , and Musoma in Tanzania. These cities and towns are also home to many factories that discharge some chemicals directly into
1995-453: Is likely that undescribed species of snails remain. Conversely, genetic studies indicate that some morphologically distinctive populations, traditionally regarded as separate species, may only be variants of single species. Two of the snail genera, Biomphalaria and Bulinus , are intermediate hosts of the parasite that causes bilharzia (schistosomiasis). Human infections by this parasite are common at Lake Victoria. This may increase as
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#17327718201012090-426: Is near-endemic. Four species of freshwater crabs are known from Lake Victoria: Potamonautes niloticus is widespread in the lake and P. emini has been recorded from the vicinity of Bukoba in Tanzania, but both are also found elsewhere in Africa. The last were first scientifically described in 2017 and very little is known about them: P. entebbe is only known from near Entebbe (the only known specimen
2185-610: The African Great Lakes . With a surface area of approximately 59,947 km (23,146 sq mi), Lake Victoria is Africa's largest lake by area, the world's largest tropical lake, and the world's second-largest fresh water lake by surface area after Lake Superior in North America. In terms of volume, Lake Victoria is the world's ninth-largest continental lake , containing about 2,424 km (1.965 × 10 acre⋅ft) of water. Lake Victoria occupies
2280-485: The African humid period began. Lake Victoria receives 80 percent of its water from direct rainfall. Average evaporation on the lake is between 2.0 and 2.2 metres (6.6 and 7.2 ft) per year, almost double the precipitation of riparian areas. Lake Victoria receives its water additionally from rivers, and thousands of small streams . The Kagera River is the largest river flowing into this lake, with its mouth on
2375-677: The Albertine Rift , and farther south, the valley of Lake Malawi . The rift also continues offshore from the coast of Mozambique along the Kerimba and Lacerda grabens , which are joined by the Davie Ridge, a 2,200 km-long (1,400 mi) relic fracture zone that cuts across the West Somali basin, straddling the boundary between Tanzania and Mozambique. The Davie Ridge ranges between 30–120 km (19–75 mi) wide, with
2470-558: The Ethiopian Highlands and the Kenya Highlands are hotspots of higher rainfall amid the semi-arid to arid lowlands of East Africa. Lakes which form within the rift, including Lake Victoria , have a large effect on regional climate. They are a source of water vapour, and also lead to the formation of lake breeze systems , which affect weather across large areas of East Africa. The east to west river valleys within
2565-623: The Miocene , 22–25 million years ago. It was formerly considered to be part of a larger Great Rift Valley that extended north to Asia Minor . A narrow zone, the rift is a developing divergent tectonic plate boundary where the African plate is in the process of splitting into two tectonic plates, called the Somali plate and the Nubian plate , at a rate of 6–7 mm (0.24–0.28 in) per year. The rift system consists of three microplates,
2660-641: The Oligocene , with the majority of the volcanism coinciding with the opening of the Red Sea and the Gulf of Aden approximately 30 Ma. The composition of the volcanics are a continuum of ultra-alkaline to tholeiitic and felsic rocks. It has been suggested that the diversity of the compositions could be partially explained by different mantle source regions. The EAR also cuts through old sedimentary rocks deposited in ancient basins. The East African Rift Zone includes
2755-823: The Victoria microplate to the north, and the Rovuma and Lwandle microplates to the south. The Victoria microplate is rotating anti-clockwise with respect to the African plate. Its rotation is caused by the configuration of mechanically weaker and stronger lithospheric regions in the EARS. Many of the African Great Lakes lie within the Rift Valley. A series of distinct rift basins, the East African Rift System extends over thousands of kilometers. North of
2850-525: The Welsh-American explorer Henry Morton Stanley , on an expedition funded by the New York Herald newspaper, confirmed the truth of Speke's discovery, circumnavigating the lake and reporting the great outflow at Ripon Falls on the lake's northern shore. Many towns and cities are reliant on Lake Victoria for their water supplies, for farming and other uses. The Lamadi water scheme is
2945-443: The hippopotamus , African clawless otter , spotted-necked otter , marsh mongoose , sitatunga , bohor reedbuck , defassa waterbuck , cane rats , and giant otter shrew . Lake Victoria and its wetlands has a large population of Nile crocodiles , as well as African helmeted turtles , variable mud turtles , and Williams' mud turtle . The Williams' mud turtle is restricted to Lake Victoria and other lakes, rivers, and swamps in
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3040-482: The upper mantle . Parallel to geological and geophysical measures (e.g. isotope ratios and seismic velocities) it is constructive to test hypotheses on computer based geodynamical models. A 3D numerical geodynamic model of the plume-crust coupling was capable of reproducing the lateral asymmetry of the EAR around the Tanzania craton . Numerical modeling of plume-induced continental break-up shows two distinct stages, crustal rifting followed by lithospheric breakup, and
3135-459: The 1990s, evidence has been found in favor of mantle plumes beneath the EAR. Others proposed an African superplume causing mantle deformation. Although the effects of deep-rooted mantle plumes are an important hypothesis, their location and dynamics are poorly understood, and a matter of active research. The question is still debated. The most recent and accepted view is the theory put forth in 2009: that magmatism and plate tectonics have
3230-950: The Afar triple junction, the rift follows two paths: west to the Red Sea Rift and east to the Aden Ridge in the Gulf of Aden . Southward from the Afar triple junction , the EAR consists of two main branches. The Eastern Rift Valley (also known as Gregory Rift ) includes the Main Ethiopian Rift , runs southward from the Afar triple junction, and continues south as the Kenyan Rift Valley, then transects Congo DR , Uganda , Rwanda , Burundi , Zambia , Tanzania , Malawi and Mozambique . The Western Rift Valley includes
3325-472: The East African Rift system form zones of localized strain. These rifts are the result of the actions of numerous normal faults which are typical of all tectonic rift zones. As aforementioned, voluminous magmatism and continental flood basalts characterize some of the rift segments, while other segments, such as the Western branch, have only very small volumes of volcanic rock. The African continental crust
3420-666: The Great Lakes. Believing he had found the source of the Nile on seeing this "vast expanse of open water" for the first time, Speke named the lake after Queen Victoria. Burton, who had been recovering from illness at the time and resting further south in Kazeh (near present-day Tabora ), was outraged that Speke claimed to have proved his discovery to have been the true source of the Nile River, which Burton regarded as still unsettled. A very public quarrel ensued, which not only sparked
3515-468: The Nile perch, since that requires a significant amount of capital resources. The water hyacinth has become a major invasive plant species in Lake Victoria. The release of large amounts of untreated wastewater (sewage) and agricultural and industrial runoff directly into Lake Victoria over the past 30 years has greatly increased the nutrient levels of nitrogen and phosphorus in the lake "triggering massive growth of exotic water hyacinth, which colonised
3610-582: The Owen Falls Dam in 1954. This allowed it to spread to Lake Kyoga where additional Nile perch were released in 1955, but not Victoria itself. Scientists argued that further introduction should wait until research showed the effect of the introduction in Kyoga, but by the late 1950s, Nile perch began being caught in Lake Victoria. As the species was already present, there were few objections when more Nile perch were transferred to Victoria to further bolster
3705-450: The Owen Falls Dam when shut down for maintenance, but this is considered highly unlikely by many scientists. The Nile perch had spread throughout the lake by 1970. Initially the population of the Nile perch was relatively low, but a drastic increase happened, peaking in the 1980s, followed by a decline starting in the 1990s. Due to the presence of the Nile perch, the natural balance of the lake's ecosystem has been disrupted. The food chain
3800-614: The Somali Jet) in the western Indian Ocean . The Somali Jet supplies water vapour for the high rainfall during the Indian Monsoon and is responsible for roughly half the global cross-equatorial atmospheric mass flux in the lower-branch of Hadley Circulation . The Rift Valley in East Africa has been a rich source of hominid fossils that allow the study of human evolution. The rapidly eroding highlands quickly filled
3895-407: The channel. Significant bays in the gulf include Naya Bay , Nyakach Bay , Osodo Bay , Kendu Bay , Homa Bay , Ruri Bay , Mirunda Bay , Asembo Bay , and Olambwe Bay . Islands in the gulf include Maboko , Rusinga , and Ndere Islands . 0°14′24″S 34°34′48″E / 0.24000°S 34.58000°E / -0.24000; 34.58000 Lake Victoria Lake Victoria is one of
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3990-462: The colonial government. In the following decades, the pressure to introduce the Nile perch continued, as did warnings about the possible effects of doing it. The first introduction of Nile perch to the region, done by the Uganda Game and Fisheries Department (then part of the colonial government) and local African fish guards, happened upstream of Murchison Falls directly after the completion of
4085-575: The complete disappearance of many endemic cichlid species has been called the "most dramatic example of human-caused extinctions within an ecosystem". Starting in the 1950s, many species have been introduced to Lake Victoria where they have become invasive and a prime reason for the extinction of many endemic haplochromine cichlids. Among the introductions are several tilapias : redbreast ( Coptodon rendalli ), redbelly ( C. zillii ), Nile ( Oreochromis niloticus ) and blue-spotted tilapias ( O. leucostictus ). Although these have contributed to
4180-544: The current Lake Victoria basin . During its geological history, Lake Victoria went through changes ranging from its present shallow depression, through to what may have been a series of much smaller lakes. Geological cores taken from its bottom show Lake Victoria has dried up completely at least three times since it formed. These drying cycles are probably related to past ice ages , which were times when precipitation declined globally. Lake Victoria last dried out about 17,300 years ago, and it refilled 14,700 years ago as
4275-423: The detritivores). The zooplanktivores have been least affected and in the late 1990s had reached densities similar to, or above, the densities before the drastic declines, although consisting of fewer species and often switching their diet towards macroinvertebrates . Some of the threatened Lake Victoria cichlid species have captive "insurance" populations in zoos, public aquaria and among private aquarists, and
4370-422: The ecosystem, it is estimated that at least 200 species (about 40 percent) of Lake Victoria haplochromines have become extinct, including more than 100 undescribed species. Initially it was feared that this number was even higher, by some estimates 65 percent of the total species, but several species that were feared extinct have been rediscovered after the Nile perch started to decline in the 1990s. Several of
4465-480: The end of 2001. Greater growth was observed in the northern part of the lake, in relatively protected areas, which may be linked to current and weather patterns and could also be due to the climate and water conditions, which are more suitable to the plants growth (as there are large urban areas to the north end of the lake, in Uganda). The invasive weed was first attempted to be controlled by hand, removed manually from
4560-418: The extinction of native fish by causing significant changes to the ecosystem , outcompeted natives and (in the case of the Nile tilapia) possibly hybridized with the highly threatened native tilapias, the most infamous introduction was the large and highly predatory Nile perch ( Lates niloticus ). As early as the 1920s, it was proposed to introduce a large pelagic predator such as the Nile perch to improve
4655-450: The feeding apparatus, changes to the eyes (giving them better sight in turbid water) and smaller head/larger caudal peduncle (allowing faster swimming). The piscivorous (affected by both predation and competition from Nile perch ), molluscivorous and insectivorous haplochromines were particularly hard hit with many extinctions. Others have become extinct in their pure form, but survive as hybrids between close relatives (especially among
4750-486: The fertility of the lake is dependent on the rate at which these nutrients can be taken up by fish and other organisms. There is little doubt that Haplochromis played an important role in returning detritus and plankton back into solution. With some 80 percent of Haplochromis species feeding off detritus, and equally capable of feeding off one another, they represented a tight, internal recycling system, moving nutrients and biomass both vertically and horizontally through
4845-433: The first Briton to document it in 1858, while on an expedition with Richard Francis Burton . Geologically, Lake Victoria is relatively young at about 400,000 years old. It was formed when westward-flowing rivers were dammed by an upthrown crustal block. During the Miocene era, what is now the catchment area of the lake was on the western side of an uplifted area that functioned as a continental divide, with streams on
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#17327718201014940-492: The first ever systematic Fisheries Survey of Lake Victoria . In his official report of the expedition, Graham wrote that "The ngege or satu Tilapia esculenta , is the most important food fish of the lake, whether for native or non-native consumption. No other fish equals it in the quality of the flesh. It is convenient size for trade, travels well and is found in much greater numbers than other important fish, such as semutundu (Luganda), Bagrus sp. ". Furthermore, Graham noted that
5035-406: The first half of the 20th century due to overfishing . To boost fishing, several species of non-native tilapia and Nile perch were introduced to the lake in the 1950s. Nevertheless, the natives continued to dominate fisheries until the 1970s where their decline meant that there was a strong shift towards the non-native Nile tilapia (now 7 percent of catches), non-native Nile perch (60 percent) and
5130-514: The first true bathymetric map of the lake. The deepest part of the lake is offset to the east of the lake near Kenya and the lake is generally shallower in the west along the Ugandan shoreline and the south along the Tanzanian shoreline. Many mammal species live in the region of Lake Victoria, and some of these are closely associated with the lake itself and the nearby wetlands. Among these are
5225-401: The fisheries in the lake. At the same time it was warned that this could present a serious danger to the native fish species and required extensive research into possible ecological effects before done. These warnings primarily concerned the native tilapia O. esculentus , as the smaller haplochromine cichlids (despite playing an important role in local fisheries) were regarded as "trash fish" by
5320-458: The inland routes in search of gold , ivory , other precious commodities, and slaves . The lake existed and was known to many Africans in the catchment area who left no written records long before it was sighted by a European in 1858 when the British explorer John Hanning Speke reached its southern shore while on his journey with Richard Francis Burton to explore central Africa and locate
5415-521: The intake of water for industries. On the other hand, water hyacinth mats can potentially have a positive effect on fish life in that they create a barrier to overfishing and allow for fish growth, there has even been the reappearance of some fish species thought to have been extinct in recent years. The overall effects of the water hyacinth, however, are still unknown. Growth of the water hyacinth in Lake Victoria has been tracked since 1993, reaching its maxima biomass in 1997 and then declining again by
5510-411: The introduction of MV Uhuru and MV Umoja . The ferry MV Bukoba sank in the lake on 21 May 1996 with a loss of between 800 and 1,000 lives, making it one of Africa's worst maritime disasters. Another tragedy occurred recently on 20 September 2018 that involved the passagers ferry MV Nyerere from Tanzania that caused the deaths of over 200 people. On 6 November 2022, Lake Victoria
5605-547: The introduction of Nile perch , the extinction of cichlids in the genus Haplochromis has also been blamed on the lake's eutrophication. The fertility of tropical waters depends on the rate at which nutrients can be brought into solution. The influent rivers of Lake Victoria provide few nutrients to the lake in relation to its size. Because of this, most of Lake Victoria's nutrients are thought to be locked up in lake-bottom deposits. By itself, this vegetative matter decays slowly. Animal flesh decays considerably faster, however, so
5700-805: The introduction of the European flax gill net of 5 inch mesh had undoubtedly caused a diminution in the number of ngege in those parts of the Kavirondo Gulf, the northern shore of the lake, the Sesse Islands and Smith's Sound which are conveniently situated close to markets. Survey catches in 1927–28 included several Haplochromis species that are now thought to be extinct, including: Haplochromis flavipinnis , Haplochromis gowersii , Haplochromis longirostris , Haplochromis macrognathus , Haplochromis michaeli , Haplochromis nigrescens , Haplochromis prognathus . As well as being due to
5795-406: The lake for its natural resources. Hundreds of endemic species that evolved under the special conditions offered by the protection of Lake Victoria have been lost due to extinction, and several more are still threatened. Their loss is devastating for the lake, the fields of ecology, genetics and evolution biology, and more evidently, for the local fisheries. Local fisheries once depended on catching
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#17327718201015890-411: The lake in the late 1990s". This invasive weed creates anoxic (total depletion of oxygen levels) conditions in the lake, inhibiting decomposing plant material, raising toxicity and disease levels to both fish and people. At the same time, the plant's mat or "web" creates a barrier for boats and ferries to maneuver, impedes access to the shoreline, interferes with hydroelectric power generation, and blocks
5985-473: The lake or its influent rivers. The set up of small beaches and local authorities around the lake lack proper sewage treatment facilities allowing pollutants to find their way into the water. Large parts of these urban areas also discharge untreated (raw) sewage into the river, increasing its eutrophication that in turn is helping to increase the invasive water hyacinth. Increased logging and act of deforestation has led to environmental degradation around
6080-405: The lake's level. Since the 1900s, Lake Victoria ferries have been an important means of transport between Uganda, Tanzania, and Kenya. The main ports on the lake are Kisumu, Mwanza, Bukoba, Entebbe , Port Bell , and Jinja. Until 1963, the fastest and newest ferry, MV Victoria , was designated a Royal Mail Ship . In 1966, train ferry services between Kenya and Tanzania were established with
6175-515: The lake's western shore. Lake Victoria is drained solely by the Nile River near Jinja, Uganda, on the lake's northern shore. In the Kenya sector, the main influent rivers are the Sio , Nzoia , Yala , Nyando , Sondu Miriu , Mogusi , and Migori . The only outflow from Lake Victoria is the Nile River, which exits the lake near Jinja, Uganda. In terms of contributed water, this makes Lake Victoria
6270-496: The lake's wide area; from increased nutrient inflows via rivers, and from increased pollution associated with settlement along its shores. Between 2010 and 2022 the surface area of Lake Victoria increased by 15% flooding lakeside communities. The lake is considered a shallow lake considering its large geographic area with a maximum depth of approximately 80 metres (260 ft) and an average depth of 40 metres (130 ft). A 2016 project digitized ten-thousand points and created
6365-449: The lake; however, re-growth occurred quickly. Public awareness exercises were also conducted. More recently, measures have been used such as the introduction of natural insect predators, including two different water hyacinth weevils and large harvesting and chopping boats, which seem to be much more effective in eliminating the water hyacinth. A green power plant that uses harvested water hyacinth (but also can use other degradable waste)
6460-634: The layer of water that lies below the thermocline , is noncirculating, and remains perpetually cold) were lower in 1990–1991 for a longer period than in 1960–1961, with values of less than 1 mg per litre (< 0.4 gr /cu ft) occurring in water as shallow as 40 metres (130 ft) compared with a shallowest occurrence of greater than 50 metres (160 ft) in 1961. The changes in oxygenation are considered consistent with measurements of higher algal biomass and productivity. These changes have arisen for multiple reasons: successive burning within its basin, soot and ash from which has been deposited over
6555-404: The lungfish, tilapia, carp and catfish that comprise the local diet. Today, the composition and yields of such fish catches are virtually negligible. Extensive fish kills, Nile perch, loss of habitat and overfishing have caused many fisheries to collapse and many protein sources to be unavailable at the market for local consumption. Few fisheries, though, have been able to make the switch to catching
6650-459: The native Lake Victoria sardine (30 percent). Because of its small size, the abundant open-water Lake Victoria sardine only supported minor fisheries until the decline of other natives. At the peak in the early 1990s, 500,000 tonnes (490,000 long tons; 550,000 short tons) of Nile perch were landed annually in Lake Victoria, but this has declined significantly in later years. A number of environmental issues are associated with Lake Victoria and
6745-619: The onset of the Holocene include approximately 50 in Ethiopia, 17 in Kenya , and 9 in Tanzania . The EAR is the largest seismically active rift system on Earth today. The majority of earthquakes occur near the Afar Depression, with the largest typically occurring along or near major border faults. Seismic events in the past century are estimated to have reached a maximum moment magnitude of 7.0. The seismicity trends parallel to
6840-462: The oxygen levels in the deeper layer of water are being depleted. Without oxygen, any aerobic life (such as fish) cannot exist in the deeper parts of the lake, forcing all life to exist within a narrow range of depth. In this way, the Nile perch has degraded the diverse and thriving ecosystem that was once Lake Victoria. The abundance of aquatic life is not the only dependent of the lake: more than thirty million people in Tanzania, Kenya and Uganda rely on
6935-540: The plants. Heavy winds and rains along with their subsequent waves may have also damaged the plants during this same time frame. The plants may not have been destroyed, instead merely moved to another location. Additionally, the water quality, nutrient supply, temperature, and other environmental factors could have played a role. Overall, the timing of the decline could be linked to all of these factors and perhaps together, in combination, they were more effective than any one deterrent would have been by itself. The water hyacinth
7030-570: The principal source of the longest branch of the Nile. However, the most distal source of the Nile Basin, and therefore the ultimate source of the Nile , is more often considered to be one of the tributary rivers of the Kagera River (the exact tributary remains undetermined), and which originates in either Rwanda or Burundi . The uppermost section of the Nile is generally known as the Victoria Nile until it reaches Lake Albert . Although it
7125-577: The region dried out, as happened to Lake Victoria about 15,000 years ago. In recent history only Lake Kyoga was easily accessible to Victoria cichlids, as further downstream movement by the Victoria Nile (to Lake Albert) is prevented by a series of waterfalls, notably Murchison . In contrast, the Owen Falls (now flooded by a dam ) between Victoria and Kyoga were essentially a series of rapids that did not effectively block fish movements between
7220-403: The region reducing the absorption of polluting chemicals and deteriorating the water quality. As of 2016, an environmental data repository exists for Lake Victoria. The repository contains shoreline, bathymetry, pollution, temperature, wind vector, and other important data for both the lake and the wider Basin. The first recorded information about Lake Victoria comes from Arab traders plying
7315-598: The region, notably Kyoga , Edward – George , Albert, and Kivu . Most of these lakes are relatively shallow (like Victoria) and part of the present-day upper Nile basin. The exception is Lake Kivu, which is part of the present-day Congo River basin , but is believed to have been connected to Lakes Edward and Victoria by rivers until the uplifting of parts of the East African Rift . This deep lake may have functioned as an "evolutionary reservoir" for this haplochromine group in periods where other shallower lakes in
7410-403: The remaining species are seriously threatened and additional extinctions are possible. Some species have survived in nearby small satellite lakes, have survived in refugias among rocks or papyrus sedges (protecting them from the Nile perch), or have adapted to the human-induced changes in the lake itself. Such adaptions include a larger gill area (adaption for oxygen-poor water), changes in
7505-488: The rift could eventually cause eastern Africa to separate from the mainland, although this potential event could take tens of millions of years. Studies that contribute to the broader understanding on the evolution of rifts can be grouped into the techniques of isotope geochemistry, seismic tomography and geodynamical modeling. The varying geochemical signatures of a suite of Ethiopian lavas suggest multiple plume sources: at least one of deep mantle origin, and one from within
7600-691: The rift system, including the Turkana Channel in northern Kenya and the Zambezi river valley, concentrate low-level easterly winds and accelerate them towards Central Africa . This leaves East Africa drier than it otherwise would be, and also supports the high rainfall in the Congo Basin rainforest . The formation of the east–west valleys could in turn be important for the aridification of East Africa over millions of years. The barrier presented by EARS concentrates monsoonal winds (known as
7695-451: The rift system, with a shallow focal depth of 12–15 km (7.5–9.3 mi) beneath the rift axis. Further away from the rift axis, focal depths can be below 30 km (19 mi). Focal mechanism solutions strike NE and frequently demonstrate normal dip-slip faulting, although left-lateral motion is also observed. The East African Rift system affects regional, continental and even global climate. Regions of higher elevation, including
7790-422: The spiny eel Mastacembelus frenatus , elephantfish ( Gnathonemus , Hippopotamyrus , Marcusenius , Mormyrus , Petrocephalus , and Pollimyrus ), the climbing gourami Ctenopoma muriei and marbled lungfish ( Protopterus aethiopicus ). At a genus level, most of these are widespread in Africa, but the very rare Xenobarbus and Xenoclarias are endemic to the lake, and the common Rastrineobola
7885-515: The stock in 1962–63. The origin of the first Victoria introductions in the 1950s is not entirely clear and indisputable evidence is lacking. Uganda Game and Fisheries Department (UGFD) officials denied that they were involved, but circumstantial evidence suggests otherwise and local Africans employed by UGFD have said that they introduced the species in 1954–55 under the directive of senior officials. UGFD officials argued that Nile perch must have spread to Lake Victoria by themselves by passing through
7980-411: The subcontinental lithosphere. In accordance, a 2014 study compares the geochemical signature of rare earth isotopes from xenoliths and lava samples collected in the EAR. The results corroborate the coexistence of a superplume "common to the entire rift" with another mantle material source being either of subcontinental type or of mid-ocean ridge type. The geophysical method of seismic tomography
8075-411: The two lakes. The Victoria haplochromines are distinctly sexually dimorphic (males relatively brightly colored; females dull), and their ecology is extremely diverse, falling into at least 16 groups, including detritivores , zooplanktivores , insectivores , prawn-eaters, molluscivores and piscivores . As a result of predation by the introduced Nile perch , eutrophication and other changes to
8170-426: The upper Nile basin. Lake Victoria formerly was very rich in fish, including many endemics, but a high percentage of these became extinct since the 1940s. The main group in Lake Victoria is the haplochromine cichlids ( Haplochromis sensu lato ) with more than 500 species, almost all endemic, and including an estimated 300 that still are undescribed . This is far more species of fish than any other lake in
8265-464: The upwelling between stages of an upper mantle plume. Prior to the rift's formation, enormous continental flood basalts erupted, uplifting the Ethiopian , Somali, and East African plateaus. The first stage of rifting of the EAR was characterized by rift localization and magmatism along the entire rift zone. Periods of extension alternated with relative inactivity. There was also the reactivation of
8360-455: The valley with sediments, creating a favorable environment for the preservation of remains. The bones of several hominid ancestors of modern humans have been found here, including those of " Lucy ", a partial australopithecine skeleton discovered by anthropologist Donald Johanson dating back over 3 million years. Richard and Mary Leakey have also done significant work in this region. In 2008, two other hominid ancestors were discovered here:
8455-756: The water column, and even out of the lake via predation by humans and terrestrial animals. The removal of Haplochromis , however, may have contributed to the increasing frequency of algal blooms , which may in turn be responsible for mass fish kills . The non-cichlid native fish include African tetras ( Brycinus ), cyprinids ( Enteromius , Garra , Labeo , Labeobarbus , Rastrineobola and Xenobarbus ), airbreathing catfish ( Clariallabes , Clarias and Xenoclarias ), bagrid catfish ( Bagrus ), loach catfish ( Amphilius and Zaireichthys ), silver butter catfish ( Schilbe intermedius ), Synodontis squeaker catfish, Nothobranchius killifish, poeciliids ( Aplocheilichthys and Micropanchax ),
8550-403: The weir and reservoir to replace it with an artificial barrage to control the level of the lake and reduce the gradual erosion of the rock weir. A standard for mimicking the old rate of outflow called the "agreed curve" was established, setting the maximum flow rate at 300 to 1,700 cubic metres per second (392–2,224 cu yd /sec) depending on the lake's water level. In 2002, Uganda completed
8645-680: The western side flowing into the Congo River basin and streams on the eastern side flowing to the Indian Ocean. As the East African Rift System formed, the eastern wall of the Albertine Rift (or Western Rift) rose, gradually reversing the drainage towards what is now Lake Victoria. The opening of the main East African Rift and the Albertine Rift downwarped the area between them as the rift walls rose, creating
8740-431: The world, except Lake Malawi . These are the result of a rapid adaptive radiation in the last circa 15,000 years. Their extraordinary diversity and speed of evolution have been the subjects for many scientists studying the forces that drive the richness of life everywhere. The Victoria haplochromines are part of an older group of more than 700 closely related species, also including those of several smaller lakes in
8835-429: Was collected in 1955 and it is unknown if it was in or near the lake) and P. busungwe only at Busungwe Island in the northwestern part of the lake. The latter likely is the smallest African freshwater crab with a carapace width up to about 1.6 cm (0.6 in), although P. kantsyore of Kagera River , and Platythelphusa maculata and P. polita of Lake Tanganyika are almost as small. The only shrimp/prawn
8930-474: Was constructed in Kisumu County in 2013. In addition to the biogas it produces, its by-product can be used as fertilizer . Other factors which may have contributed to the decline of the water hyacinth in Lake Victoria include varying weather patterns, such as El Niño during the last few months of 1997 and first six months of 1998 bringing with it higher levels of water in the lake and thus dislodging
9025-468: Was the site of a commercial passenger aircraft crash. Precision Air Flight 494 an ATR 42–500 carrying 39 passengers and four crew, crashed while approaching Bukoba Airport , resulting in 19 fatalities. East African Rift The East African Rift ( EAR ) or East African Rift System ( EARS ) is an active continental rift zone in East Africa . The EAR began developing around the onset of
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