Lake Victoria

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Lake Victoria
Topography of Lake Victoria.png
Location Africa
Coordinates 1°S 33°E / 1°S 33°E / -1; 33Coordinates: 1°S 33°E / 1°S 33°E / -1; 33
Primary inflows Kagera River
Primary outflows White Nile (river) (known as the "Victoria Nile" as it flows out of the lake)
Catchment area 184,000 km2 (71,000 sq mi)
238,900 km2 (92,200 sq mi) basin
Basin countries Tanzania
Uganda
Kenya
Max. length 337 km (209 mi)
Max. width 250 km (160 mi)
Surface area 68,800 km2 (26,600 sq mi)
Average depth 40 m (130 ft)
Max. depth 83 m (272 ft)
Water volume 2,750 km3 (660 cu mi)
Shore length1 3,440 km (2,140 mi)
Surface elevation 1,133 m (3,717 ft)
Islands 84 (Ssese Islands, Uganda)
Settlements Bukoba, Tanzania
Mwanza, Tanzania
Musoma, Tanzania
Kisumu, Kenya
Kendu Bay, Kenya
Homa Bay, Kenya
Kampala, Uganda
Entebbe, Uganda
Jinja, Uganda
1 Shore length is not a well-defined measure.

Lake Victoria (Nam Lolwe in Luo; "Nalubaale" in Luganda; Victoria Nyanza in Bantu[1] ) is one of the African Great Lakes. The lake was named after Queen Victoria by the explorer John Hanning Speke, who was the first European to discover it, and which he did alone in 1858 while on an expedition with Richard Francis Burton to locate the source of the Nile River.[2][3]

With a surface area of 68,800 square kilometres (26,600 sq mi), Lake Victoria is Africa’s largest lake by area, and it is the largest tropical lake in the world. Lake Victoria is the world's 2nd largest freshwater lake by surface area; only Lake Superior in North America is larger. In terms of its volume, Lake Victoria is the world's ninth largest continental lake, and it contains about 2,750 cubic kilometers (2.2 billion acre-feet) of water.

Lake Victoria receives its water primarily from direct precipitation and thousands of small streams. The largest stream flowing into this lake is the Kagera River, the mouth of which lies on the lake's western shore. Lake Victoria is drained solely by the Nile River near Jinja, Uganda, on the lake's northern shore.[4]

Lake Victoria occupies a shallow depression in Africa and has a maximum depth of 84 m (276 ft) and an average depth of 40 m (130 ft).[5] Its catchment area covers 184,000 square kilometers (71,040 sq mi). The lake has a shoreline of 4,828 km (3,000 mi), with islands constituting 3.7% of this length,[6] and is divided among three countries: Kenya (6% or 4,100 km2 or 1,600 sq mi), Uganda (45% or 31,000 km2 or 12,000 sq mi) and Tanzania (49% or 33,700 km2 or 13,000 sq mi).[7]

Geology[edit]

Landsat 7 imagery of Lake Victoria

Lake Victoria has, during its geological history, gone through changes ranging from its present shallow depression, through to what may have been a series of much smaller lakes.[6] Geological cores taken from its bottom show Lake Victoria has dried up completely at least three times since it formed.[8] These drying cycles are probably related to past ice ages, which were times when precipitation declined globally.[8] Lake Victoria last dried out 17,300 years ago, and it refilled beginning about 14,700 years ago. Geologically, Lake Victoria is relatively young – about 400,000 years old – and it formed when westward-flowing rivers were dammed by an upthrown crustal block.[8]

Lake Victoria and the Great Rift Valley

This geological history probably contributed to the dramatic cichlid speciation that characterises its ecology, as well as that of other African Great Lakes,[9] although some researchers dispute this, arguing while Lake Victoria was at its lowest between 18,000 and 14,000 years ago, and it dried out at least once during that time, there is no evidence of remnant ponds or marshes persisting within the desiccated basin. If such features existed, then they would have been small, shallow, turbid, and/or saline, and therefore markedly different from the lake to which today's species are adapted.[10]

The shallowness of Lake Victoria, its limited river inflow, and its large surface area compared to its volume make it vulnerable to the effects of climate changes.

Hydrology and limnology[edit]

Lake Victoria receives 80% of its water from direct precipitation.[6] 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.[11] In the Kenya Sector, the main influent rivers are the Sio, Nzoia, Yala, Nyando, Sondu Miriu, Mogusi and the Migori. Combined, these rivers contribute far more water to the lake than does the largest single inflowing river, the Kagera River, which enters the lake from the west.[12]

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 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 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. 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.[13] These changes have arisen for multiple reasons: successive burning within its basin,[14] soot and ash from which has been deposited over the lake's wide area; from increased nutrient inflows via rivers,[15] and from increased pollution associated with settlement along its shores.

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.[6][16] By itself, this vegetative matter decays slowly. Animal flesh decays considerably faster, however, so the fertility of the lake is dependent on the rate at which these nutrients can be taken up by fish and other organisms.[16] There is little doubt that Haplochromis played an important role in returning detritus and plankton back into solution.[17][18][19] With some 80% 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 the water column, and even out of the lake via predation by humans and terrestrial animals.[17] The removal of Haplochromis, however, may have contributed to the increasing frequency of algal blooms,[15][18][19] which may in turn be responsible for mass fish kills.[15]

Fisheries[edit]

Lake Victoria supports Africa's largest inland fishery.[20]

Environmental issues[edit]

A number of environmental issues are associated with Lake Victoria.

Fishing[edit]

The introduction of exotic fish species, especially the Nile perch, has altered the freshwater ecosystem of the lake and driven several hundred species of native cichlids to near or total extinction.

Water hyacinth invasion[edit]

The Water hyacinth has become a major invasive plant species in Lake Victoria. The release of large amounts of untreated wastewater (sewage), 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 the lake in the late 1990’s”.[21][22] 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 the intake of water for industries.[21][23][24][25][26] On the flip side, 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. However, the overall effects of the Water hyacinth are still unknown.[23][27]

Growth of the Water hyacinth in Lake Victoria has been tracked since 1993, reaching its maxima biomass in 1997 and then declining again by the end of 2001.[23] 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).[26] The invasive weed was first attempted to be controlled by hand, removed manually from the lake, however, re-growth occurred quickly. Public awareness exercises were also conducted.[26] 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.[26][28][29][30]

Other factors which may have contributed to the decline of the Water hyacinth in Lake Victoria include varying weather patterns, such as El Nino 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 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 however, simply moved to another location. Additionally, the water quality and nutrient supply, temperature and other environmental factors could have played a role. Overall the timing of 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.[26] The Water hyacinth is in remission and this trend could be permanent if control efforts are continued.[31]

Pollution[edit]

Population density around Lake Victoria

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 is one of the most densely populated rural areas in the world. Its shores are dotted with cities and towns, including Kisumu, Kisii, and Homa Bay in Kenya; Kampala, Jinja, and Entebbe in Uganda; and Bukoba, Mwanza and Msoma in Tanzania. These cities and towns also are home to many factories that discharge their waste directly into the lake and its influent rivers. These urban areas also discharge raw sewage into the river, increasing its eutrophication that in turn is helping to sustain the invasive water hyacinth.[32]

History and exploration[edit]

Bismack Rock

The first recorded information about Lake Victoria comes from Arab traders plying the inland routes in search of gold, ivory, other precious commodities, and slaves. An excellent map, known as the Al Idrisi map from the calligrapher who developed it and dated from the 1160s, clearly depicts an accurate representation of Lake Victoria, and attributes it as the source of the Nile.

The lake as it is visible from the shores of the Speke Resort in Kampala, Uganda

The lake was first 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 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 on the shores of Lake Tanganyika, was outraged that Speke claimed to have proved his discovery to have been the true source of the Nile, which Burton regarded as still unsettled. A very public quarrel ensued, which not only sparked 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.[33]

In the past, the famous British 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.[34] Ultimately, 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.

Local languages around lake Victoria

Nalubaale Dam[edit]

The only outflow for Lake Victoria is at Jinja, Uganda, where it forms the White Nile. The water 12,000 years ago drained over a natural rock weir. In 1952, British colonial engineers blasted out the weir and reservoir. 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 a second hydroelectric complex in the area, the Kiira 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,[35] and was primarily responsible for recent drops in the lake's level.

Transport[edit]

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 Kenyan independence in 1963, the fastest and most modern ferry, MV Victoria, was designated a Royal Mail Ship. In 1966, train ferry services between Kenya and Tanzania were established with the introduction of MV Uhuru and MV Umoja. The ferry MV Bukoba sank in the lake on May 21, 1996 with a loss of between 800 and 1,000 lives, making it one of Africa's worst maritime disasters.


See also[edit]


References[edit]

  1. ^ "The Victoria Nyanza. The Land, the Races and their Customs, with Specimens of Some of the Dialects". World Digital Library. Retrieved 18 February 2013. 
  2. ^ Dalya Alberge (11 September 2011). "How feud wrecked the reputation of explorer who discovered Nile's source". The Observer (The Guardian). Retrieved 29 December 2013. 
  3. ^ Moorehead, Alan (1960). "Part One: Chapters 1-7". The White Nile. Harper & Row. ISBN 0-06-095639-9. 
  4. ^ vanden Bossche, J.-P.; Bernacsek, G. M. (1990). Source Book for the Inland Fishery Resources of Africa, Issue 18, Volume 1. Food & Agriculture Org. (United Nations). p. 291. ISBN 92-5-102983-0. Retrieved 29 December 2013. 
  5. ^ United Nations, Development and Harmonisation of Environmental Laws Volume 1: Report on the Legal and Instituional Issues in the Lake Victoria Basin, United Nations, 1999, page 17
  6. ^ a b c d C. F. Hickling (1961). Tropical Inland Fisheries. London: Longmans. 
  7. ^ J. Prado, R. J. Beare, J. Siwo Mbuga & L. E. Oluka, 1991. A catalogue of fishing methods and gear used in Lake Victoria. UNDP/FAO Regional Project for Inland Fisheries Development (IFIP), FAO RAF/87/099-TD/19/91 (En). Rome, Food and Agricultural Organisation.
  8. ^ a b c John Reader (2001). Africa. Washington, D.C.: National Geographic Society. pp. 227–228. ISBN 0-7922-7681-7. 
  9. ^ Christian Sturmbauer, Sanja Baric, Walter Salzburger, Lukas Rüber & Erik Verheyen (2001). "Lake level fluctuations synchronize genetic divergences of cichlid fishes in African lakes" (PDF). Molecular Biology and Evolution 18: 144–154. PMID 11158373. 
  10. ^ J. C. Stager & T. C. Johnson (2008). "The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota". Hydrobiologia 596 (1): 5–16. doi:10.1007/s10750-007-9158-2. 
  11. ^ Simeon H. Ominde (1971). "Rural economy in West Kenya". In S. H. Ominde. Studies in East African Geography and Development. London: Heinemann Educational Books Ltd. pp. 207–229. ISBN 0-520-02073-1. 
  12. ^ P. J. P. Whitehead (1959). "The river fisheries of Kenya 1: Nyanza Province". East African Agricultural and Forestry Journal 24 (4): 274–278. 
  13. ^ R. E. Hecky, F. W. B. Bugenyi, P. Ochumba, J. F. Talling, R. Mugidde, M. Gophen and L. Kaufman (1994). "Deoxygenation of the deep water of Lake Victoria, East Africa". Limnology and Oceanography 39 (6): 1476–1481. JSTOR 2838147. 
  14. ^ R. E. Hecky (1993). "The eutrophication of Lake Victoria". Verhandlungen der Internationale Vereinigung für Limnologie 25: 39–48. 
  15. ^ a b c Peter B. O. Ochumba & David I. Kibaara (1989). "Observations on blue-green algal blooms in the open waters of Lake Victoria, Kenya". African Journal of Ecology 27 (1): 23–34. doi:10.1111/j.1365-2028.1989.tb00925.x. 
  16. ^ a b R. S. A. Beauchamp (1954). "Fishery research in the lakes of East Africa". East African Agricultural Journal 19 (4): 203–207. 
  17. ^ a b Les Kaufman (1992). "Catastrophic change in species-rich freshwater ecosystems: the lessons of Lake Victoria". BioScience 42 (11): 846–858. JSTOR 1312084. 
  18. ^ a b Les Kaufman & Peter Ochumba (1993). "Evolutionary and conservation biology of cichlid fishes as revealed by faunal remnants in northern Lake Victoria". Conservation Biology 7 (3): 719–730. doi:10.1046/j.1523-1739.1993.07030719.x. JSTOR 2386703. 
  19. ^ a b Tijs Goldschmidt, Frans Witte & Jan Wanink (1993). "Cascading effects of the introduced Nile perch on the detrivorous/phytoplantivorous species in sublittoral areas of Lake Victoria". Conservation Biology 7 (3): 686–700. doi:10.1046/j.1523-1739.1993.07030686.x. JSTOR 2386700. 
  20. ^ Kim Geheb (1997). The Regulators and the regulated: fisheries management, options and dynamics in Kenya's Lake Victoria Fishery (Ph.D. thesis). University of Sussex. 
  21. ^ a b Luilo, G. B. (August 01, 2008). Lake Victoria water resources management challenges and prospects: a need for equitable and sustainable institutional and regulatory frameworks. African Journal of Aquatic Science, 33, 2, 105-113.
  22. ^ Muli, J., Mavutu, K., and Ntiba, J. (2000) Micro-invertebrate fauna of water hyacinth in Kenyan waters of Lake Victoria. International Journal of Ecology and Environmental Science 20: 281–302
  23. ^ a b c Kateregga, E., & Sterner, T. (January 01, 2009). Lake Victoria Fish Stocks and the Effects of Water Hyacinth. Journal of Environment & Development, 18, 1, 62-78.
  24. ^ Mailu, A. M., G. R. S. Ochiel, W. Gitonga and S. W. Njoka. 1998. Water Hyacinth: An Environmental Disaster in the Winam Gulf of Lake Victoria and its Control, p. 101-105.
  25. ^ Gichuki, J., F. Dahdouh Guebas, J. Mugo, C. O. Rabour, L. Triest and F. Dehairs. 2001. Species inventory and the local uses of the plants and fishes of the Lower Sondu Miriu wetland of Lake Victoria, Kenya. Hydrobiologia 458:99-106.
  26. ^ a b c d e Albright, T. P., Moorhouse, T. G., & McNabb, T. J. (January 01, 2004). The Rise and Fall of Water Hyacinth in Lake Victoria and the Kagera River Basin, 1989-2001. Journal of Aquatic Plant Management, 42, 73-84.
  27. ^ Jäger, J., Bohunovsky, L., Radosh, L., & Sustainability Project. (2008). Our planet: How much more can earth take?. London: Haus.
  28. ^ Ochiel, G. S., A. M. Mailu, W. Gitonga and S. W. Njoka. 1999. Biological Control of Water Hyacinth on Lake Victoria, Kenya, p. 115-118.
  29. ^ Mallya, G. A. 1999. Water hyacinth control in Tanzania, p. 25-29.
  30. ^ United Nations Environment Programme., & Belgium. (2006). Africa's lakes: Atlas of our changing environment. Nairobi, Kenya: UNEP.
  31. ^ Crisman, T. L., Chapman, Lauren J., Chapman, Colin A., & Kaufman, Les S. (2003). Conservation, ecology, and management of African fresh waters. Gainesville: University Press of Florida.
  32. ^ "Water Hyacinth Re-invades Lake Victoria". Image of the Dat (NASA). February 21, 2007. 
  33. ^  "Speke, John Hanning". Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900. 
  34. ^ "Kenya, Africa – Lake Victoria in Kenya". Jambo Kenya Network. Retrieved July 14, 2008. 
  35. ^ Fred Pearce (February 9, 2006). "Uganda pulls plug on Lake Victoria". New Scientist 2538: 12. 

External links[edit]

Institutions of the East African Community