Lake Turkana

Lake Turkana
Jade Sea
Coordinates 3°35′N 36°7′E / 3.583°N 36.117°E / 3.583; 36.117Coordinates: 3°35′N 36°7′E / 3.583°N 36.117°E / 3.583; 36.117
Lake type Saline, monomictic, alkaline, endorheic
Primary inflows Omo River, Turkwel River, Kerio River
Primary outflows Evaporation
Catchment area 130,860 km2 (50,530 sq mi)
Basin countries Kenya, Ethiopia
Max. length 290 km (180 mi)
Max. width 32 km (20 mi)
Surface area 6,405 km2 (2,473 sq mi)
Average depth 30.2 m (99 ft)
Max. depth 109 m (358 ft)
Water volume 203.6 km3 (165,100,000 acre·ft)
Salinity 2.44‰[1]
Surface elevation 360.4 m (1,182 ft)
Islands North Island, Central Island, South Island (volcanic)
Settlements

El Molo, Loyangalani, Kalokol, Eliye Springs, Ileret, Fort Banya.

UNESCO World Heritage Site
Criteria viii, x
Reference 801
Inscription 1997 (21st Session)
Extensions 2001
IUCN category II (national park)

Lake Turkana (/tɜːrˈkɑːnə/ or /tɜːrˈkænə/), formerly known as Lake Rudolf, is a lake in the Kenyan Rift Valley, in northern Kenya, with its far northern end crossing into Ethiopia.[2] It is the world's largest permanent desert lake and the world's largest alkaline lake. By volume it is the world's fourth-largest salt lake after the Caspian Sea, Issyk-Kul, and Lake Van (passing the shrinking South Aral Sea), and among all lakes it ranks 24th.

Lake Turkana is now threatened by the construction of Gilgel Gibe III Dam in Ethiopia due to the damming of the Omo river which supplies most of the lake's water.

The water is potable, but not palatable. It supports a rich lacustrine wildlife. The climate is hot and very dry.

The rocks of the surrounding area are predominantly volcanic. Central Island is an active volcano, emitting vapour. Outcrops and rocky shores are found on the east and south shores of the lake, while dunes, spits and flats are on the west and north, at a lower elevation.

On-shore and off-shore winds can be extremely strong, as the lake warms and cools more slowly than the land. Sudden, violent storms are frequent. Three rivers (the Omo, Turkwel and Kerio) flow into the lake, but lacking outflow, its only water loss is by evaporation. Lake volume and dimensions are variable. For example, its level fell by 10 metres between 1975 and 1993.[3]

Due to temperature, aridity and geographic inaccessibility, the lake retains its wild character. Nile crocodiles are found in great abundance on the flats. The rocky shores are home to scorpions and carpet vipers.

Lake Turkana National Parks are now listed as a UNESCO World Heritage Site. Sibiloi National Park lies on the lake's eastern shore, while Central Island National Park and South Island National Park lie in the lake. Both are known for their Nile crocodiles.

An abundance of hominid fossils have been discovered in the area surrounding Lake Turkana.

Name

The lake was named Lake Rudolf (in honour of Crown Prince Rudolf of Austria) by Count Sámuel Teleki de Szék and his second-in-command Lieutenant Ludwig Ritter Von Höhnel, a Hungarian and an Austrian, on 6 March 1888.[4] They were the first Europeans to have recorded visiting the lake after a long safari across East Africa. Natives who live around Lake Turkana include the Turkana, Rendille, Gabbra, Daasanach, Hamar Koke, Karo, Nyagatom, Mursi, Surma, and Molo peoples. For the location of many of these peoples, refer to the dialect map in the article.

J. W. Gregory reported in The Geographical Journal of 1894 that it was called "Basso Narok", meaning "Black Lake" in the Samburu language. Likewise, nearby Lake Chew Bahir is "Basso Naibor" in Samburu, meaning "White Lake". The Samburu are among the dominant tribes in the lake Turkana region when the explorers came."[5] What the native form of this phrase was, what it might mean, and in which language is not clear. The lake kept its European name during the colonial period of British East Africa. After the independence of Kenya, the president, Mzee Jomo Kenyatta, renamed it in 1975 after the Turkana, the predominant tribe there.

At some unknown time, the lake acquired an alternate name as the Jade Sea from its turquoise colour seen approaching from a distance. The colour comes from algae that rise to the surface in calm weather. This is likely also a European name. The Turkana refer to the lake as Anam Ka'alakol, meaning "the sea of many fish". It is from the name Ka'alakol that Kalokol, a town on the western shore of Lake Turkana, east of Lodwar, derives its name. The previous indigenous Turkana name for Lake Turkana was Anam a Cheper. The area still sees few visitors, being a two-day drive from Nairobi. The lake is also an imaginary boundary of the Rendille and Borana and Oromo to the Turkana land. The area is primarily clay-based and is more alkaline than seawater.

Biology

Satellite image of Lake Turkana, distinguishable from its jade color. The Omo River enters at the top. The river visible on the lower left is the Turkwel, which has been dammed for hydroelectric power.

Biomes

The major biomes are the lake itself, which is an aquatic biome, and the surrounding region, which is classified as desert and xeric shrubland. The Chalbi Desert is east of the lake. During moister times, a dry grassland appears, featuring Aristida adcensionis and A. mutabilis. During drier times, the grass disappears. The shrublands contain dwarf shrubs, such as Duosperma eremophilum and Indigofera spinosa. Near the lake are doum palms.

Plankton

Both phytoplankton and zooplankton are found in the lake.[6] Of the former, cyanobacteria are represented by Microcystis aeruginosa and microalgae by Botryococcus braunii. Also present are Anabaenopsis arnoldii, Planctonema lauterbornii, Oocystis gigas, Sphaerocystis schroeteri, and some others. The zooplankton includes copepods, cladocerans and protozoans.

Fish

Compared to other large African lakes, Turkana has relatively few fish species in total; the lake holds about 50 fish species, including 12 endemics: the cichlids Haplochromis macconneli, H. rudolfianus, H. turkanae and Hemichromis exsul, the barb Enteromius turkanae, the catfish Chrysichthys turkana, the robber tetras Brycinus ferox and B. minutus, the Rudolf lates Lates longispinis, the lampeyes Lacustricola jeanneli and Micropanchax rudolfianus, and the cyprinid Neobola stellae.[7] Non-endemics include species such as Nile tilapia, bichirs, the elephantfish Mormyrus kannume, African arowana, African knifefish, Distichodus niloticus, the Nile perch and numerous others.[6][8] During the early Holocene, the water level of the lake was higher, and it overflowed into the Nile River, allowing fish and crocodiles access. Consequently, the non-endemic fishes in the lake are mainly riverine species of Nilotic origin.[7] Some of the non-endemics do not breed in the lake, but migrate up the Omo River and other affluents to breed.[7] The lake is heavily fished.

Birds

The Lake Turkana region is home to hundreds of species of birds native to Kenya.[9] The East African Rift System also serves as a flyway for migrating birds, bringing in hundreds more. The birds are essentially supported by plankton masses in the lake, which also feed the fish.

Some birds more common to Turkana are the little stint, the wood sandpiper, and the common sandpiper. The African skimmer (Rhyncops flavirostris) nests in the banks of Central Island. The white-breasted cormorant (Phalacrocorax lucidus) ranges over the lake, as do many other waterbirds. The greater flamingo wades in its shallows. Heuglin's bustard (Neotis heuglinii) is found in the east of the lake region.

Reptiles

The lake formerly contained Africa's largest population of Nile crocodiles: 14,000, as estimated in a 1968 study by Alistair Graham.[10]

The lake also has a large population of large water turtles, particularly in the area of Central Island.

Mammals

Over the dry grasslands ranges a frail population of grazing mammals and predators. The grazers are chiefly Grevy's zebra, Burchell's zebra, the beisa oryx, Grant's gazelle, the topi and the reticulated giraffe. They are hunted by the lion and the cheetah. Elephants and the black rhinoceroses are no longer seen, although Teleki reported seeing (and shooting) many. Closer to the dust is the cushioned gerbil (Gerbillus pulvinatus).

Geology

Lake Turkana is an East African Rift feature.[11] A rift is a weak place in the Earth's crust due to the separation of two tectonic plates, often accompanied by a graben, or trough, in which lake water can collect. The rift began when East Africa, impelled by currents in the mantle,[12] began separating from the rest of Africa, moving to the northeast. Currently, the graben is 320 km wide in the north of the lake, 170 km in the south. This rift is one of two, and is called the Great or Eastern Rift. There is another to the west, the Western Rift.

Lake Turkana is a unique feature of the East African landscape. Besides being a permanent desert sea, it is the only sea that retains the waters originating from two separate catchment areas of the Nile. The Lake Turkana drainage basin draws its waters mainly from Kenya Highlands and Ethiopian Highlands.

The basement rocks of the region have been dated by two analytical determinations to 522 and 510 million years ago (mya). No rift was in the offing at that time. A rift is signalled by volcanic activity through the weakened crust. The oldest volcanic activity of the region occurred in the Nabwal Hills northeast of Turkana and is dated to 34.8 mya in the late Eocene.[13]

The visible tectonic features of the region result from extensive extrusions of basalt over the Turkana-Omo basin in the window 4.18–3.99 mya.[14] These are called the Gombe Group Basalts. They are subdivided into the Mursi Basalts and the Gombi Basalts.

The two latter basalts are identified as the outcrops forming the rocky mountains and badlands around the lake. In the Omo portion of the basin, of the Mursi Basalts, the Mursi Formation is on the west side of the Omo, the Nkalabong on the Omo, and the Usno and Shungura east of the Omo. Probably the best known of the formations are the Koobi Fora on the east side of Turkana and the Nachukui on the west.

Short-term fluctuations in lake level combined with periodic volcanic ash spewings over the region have resulted in a fortuitous layering of the ground cover over the basal rocks. These horizons can be dated more precisely by chemical analysis of the tuff.[15] As this region is believed to have been an evolutionary nest of hominins, the dates are important for generating a diachronic array of fossils, both hominoid and nonhominoid—that is, both ape (includes hominins) and non-ape. Many thousands have been excavated.

Terraces representing ancient shores are visible in the Turkana Basin. The highest is 100 m above the surface of the lake (only approximate, as the lake level fluctuates), which occurred about 9500 years ago, at the end of the Pleistocene.[16] It is generally theorised that Turkana was part of the upper Nile system at that time, connecting to Lake Baringo at the southern end and the White Nile in the north, and that volcanic land adjustments severed the connection. Such a hypothesis explains the Nile species in the lake, such as the crocodiles and the Nile perch. High water levels also occurred approximately 9000, 6000 and 5000 years ago, each of which were followed by drops in lake level of more than 40m in less than 200 years.[16] It is thought that changes in the position of the Congo Air Boundary affected the ability of moisture from the Atlantic Ocean to reach eastern Africa,[17][18] which had a profound influence on the level of Lake Turkana and adjacent water bodies.[19][16]

Anthropology

Hominin fossils of some of the earliest human ancestors have been found in the Turkana Basin. Australopithecus anamensis fossils discovered by Meave Leakey in 1994 date to around 4 million years ago. Richard Leakey has led numerous anthropological expeditions in the area which have led to many important discoveries of hominin remains.

The two-million-year-old skull 1470 was found in 1972. It was originally thought to be Homo habilis, but the scientific name Homo rudolfensis, derived from the old name of this lake (Rudolf) was proposed in 1986 by V. P. Alexeev. In 1984, the Turkana Boy, a nearly complete skeleton of a Homo ergaster juvenile, was discovered by Kamoya Kimeu. More recently, Meave Leakey discovered a 3.5 million-year-old skull there, designated Kenyanthropus platyops ("the flat-faced man of Kenya").

Marta Mirazón Lahr discovered the earliest evidence of human warfare at the site of Nataruk, located near the shore of an ancient and larger Lake Turkana, and where numerous human skeletons showing major traumatic injuries to the head, neck, ribs, knees and hands are evidence of inter-group conflict between nomadic hunter-gatherers 10,000 years ago.[20]

Many language groups are represented in the area around Lake Turkana,[21] which is evidence for numerous migrations of diverse people over thousands of years. The current language groups include at least three separate subgroups of the Nilotic (Nilo-Saharan) and Cushitic (Afro-Asiatic) language families, which have further subdivided into more than 12 languages that surrounding the lake today.[22] In the early Holocene (during the Holocene Climatic Optimum), lake levels were high and fishing and foraging were the primary subsistence economies. This was mostly supplanted by animal-based agriculture by 5000 years ago, when the lake level was in a period of rapid fluctuation.[23] During the later Holocene, human responses to climatic changes included intensive fishing when lake level was high and a shift to cattle herding when the level dropped.[23] Megalithic graves are found widely distributed on the lake shores and appear to correspond to the period when domesticated animals were first introduced to the region about 5000 years ago,[24] while later, the dead were buried in small grave cairns.[25] People who live in the region today commonly practice mixed subsistence, switching between hunting, fishing and animal herding based on what is feasible in a given year.[23] However, the construction of infrastructure like Christian missionary stations, energy extraction (wind, oil) and NGO aid distribution points have made the region more connected to and dependent on outside resources for subsistence.[26][27] Traditional modes of subsistence like pastoralism and fishing are now supplemented by the cash-based economy.

Wind power

The Lake Turkana Wind Power consortium (LTWP) plans to provide 310 MW of power to Kenya's national electricity grid by tapping the unique wind conditions around the lake.[28] The plan calls for 365 wind turbines, each with a nameplate capacity of 850 kilowatts. As of October 2016 155 turbines had been installed with completion expected in 2017. It will be the largest wind power project in Africa.[29]

Dams

The Gibe III dam is already under construction by Ethiopia along its Omo River, with general recognition that it will cause a major decrease in river flow downstream and a serious reduction of inflow to Kenya's Lake Turkana, which receives 90 per cent of its waters from the river. According to the ARWG report, these changes will destroy the survival means of at least 200,000 pastoralists, flood-dependent agriculturalists and fishers along the Omo River 300,000 pastoralists and fishers around the shores of Lake Turkana - plunging the region’s ethnic groups into cross-border violent conflict reaching well into South Sudan, as starvation confronts all of them.

The report offers a devastating look a deeply flawed development process fueled by the special interests of global finance and African governments. In the process, it identifies major overlooked or otherwise minimized risks, not the least of which is a U.S. Geological Survey estimation of a high risk for a magnitude 7 or 8 earthquake in the Gibe III dam region.

Impact on Lake Turkana Edit The magnitude of the impact that the dam and possible irrigation projects induced by the dam will have on the water level of Lake Turkana is controversial. A hydrological study conducted for the African Development Bank in November 2010 concluded that the filling of the dam will reduce the lake's water level by two metres, if no irrigation will be undertaken. Irrigation would cause a further drop in the lake level.[29]

Friends of Lake Turkana, a Kenyan organization representing indigenous groups in northwestern Kenya whose livelihoods are linked to Lake Turkana, had previously estimated that the dam could reduce the level of Lake Turkana by up to 10 meter affecting up to 300,000 people.[30] This could cause the brackish water to increase in salinity to where it may no longer be drinkable by the indigenous groups around the lake. Currently, the salinity of the water is about 2332 mg/L, and it is estimated that a 10-meter decrease in the water level of Lake Turkana could cause the salinity to rise to 3397 mg/L.[20] Raising salinity could also drastically reduce the number of fish in the lake, which the people around Lake Turkana depend on for sustenance and their livelihoods. According to critics, this "will condemn the lake to a not-so-slow death."[9]

According to dam proponents, the impact on Lake Turkana will be limited to the temporary reduction in flows during the filling of the reservoir. Various sources state that the filling could take between one and three wet seasons.[9][26] The total storage volume of the reservoir of Gibe III dam will be between 11.75 and 14 billion cubic meter, depending on sources. According to the firm that builds the dam this would reduce the water level in the lake by "less than 50 cm per year for three years" and that salinity "will not change in any way".[26]

According to the International Lake Environment Committee, 90% of Lake Turkana's water is delivered by the Omo River on which the Dam would be built.[31] With no outlet, Lake Turkana loses 2.3 meters of water every year to evaporation, and its level is sensitive to climatic and seasonal fluctuations. For purposes of comparison, the historic level of Lake Turkana declined from a high of 20m above today's level in the 1890s to the same level as today in the 1940s and 1950s. Then it increased again gradually by 7 meters to reach a peak around 1980, and subsequently decreased again.[31]

The Environmental and Social Impact Assessment (ESIA) summary of the project did not assess the impact of the dam on the water level and water quality of Lake Turkana.[32] The director of Kenya's Water Services Regulatory Board, John Nyaoro, argued that the dam would have no negative impact on Lake Turkana.[33]

See also

References

  1. ↑ HYDROLOGICAL IMPACTS OF ETHIOPIA’S OMO BASIN ON KENYA’S LAKE TURKANA WATER LEVELS & FISHERIES (2010), page 2-65 (Pdf)
  2. ↑ The boundary between Ethiopia and Kenya has been a contentious rational distinction. A brief consideration of the topic can be found in the State Department document, Ethiopia – Kenya Boundary Archived 18 March 2009 at the Wayback Machine.
  3. ↑ Historic lake levels are graphed in the World Lakes Database.
  4. ↑ A summary of the European discovery as well as Teleki's map and some Turkana tribe legends are stated in a University of Trieste document online.
  5. ↑ "Contributions to the Physical Geography of British East Africa" Geographical Journal, 4 (1894), pp. 289–315.
  6. 1 2 The World Lakes Database includes mention of the lake plankton, some of which are responsible for its turquoise colour.
  7. 1 2 3 Freshwater Ecoregions of the World (2008). Lake Turkana. Accessed 2 May 2011
  8. ↑ Fish Species in Lake Turkana
  9. ↑ The Internet hosts a number of bird sites giving scientific names, data and photographs of birds found around the lake: The Sibiloi National Park site, the Kenya Birds site, the African Bird Image Database, the Birdlife International site, and many others.
  10. ↑ Alistair Graham, Eyelids of Morning
  11. ↑ A good introduction is stated in the Regions of Kenya site.
  12. ↑ For the mantle currents, or "plumes", see the abstract of Tertiary Mafic Lavas of Turkana ..., Journal of Petrology Volume 47, Number 6 Pp. 1221–1244.
  13. ↑ See the abstract of Geochronology of the Nabwal Hills ..., Geological Magazine; January 2006; v. 143; no. 1; p. 25-39.
  14. ↑ See Mineral chemistry of Turkana basalts and implications for basin development, Karla Knudson, Louise Miltich, Nick Swanson-Hysell. The article is highly technical. Look for the summaries.
  15. ↑ Refer to the abstract of Precise ... geochronology for the upper Koobi Fora Formation...., Journal of the Geological Society; January 2006; v. 163; no. 1; p. 205-220.
  16. 1 2 3 Bloszies, C.; Forman, S. L.; Wright, D. K. (2015-09-01). "Water level history for Lake Turkana, Kenya in the past 15,000 years and a variable transition from the African Humid Period to Holocene aridity". Global and Planetary Change. 132: 64–76. doi:10.1016/j.gloplacha.2015.06.006.
  17. ↑ Costa, Kassandra; Russell, James; Konecky, Bronwen; Lamb, Henry (2014-01-01). "Isotopic reconstruction of the African Humid Period and Congo Air Boundary migration at Lake Tana, Ethiopia". Quaternary Science Reviews. 83: 58–67. doi:10.1016/j.quascirev.2013.10.031.
  18. ↑ Tierney, Jessica E.; Russell, James M.; Sinninghe Damsté, Jaap S.; Huang, Yongsong; Verschuren, Dirk (2011-04-01). "Late Quaternary behavior of the East African monsoon and the importance of the Congo Air Boundary". Quaternary Science Reviews. 30 (7–8): 798–807. doi:10.1016/j.quascirev.2011.01.017.
  19. ↑ Junginger, Annett; Roller, Sybille; Olaka, Lydia A.; Trauth, Martin H. (2014-02-15). "The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15–5 ka BP)". Palaeogeography, Palaeoclimatology, Palaeoecology. 396: 1–16. doi:10.1016/j.palaeo.2013.12.007.
  20. ↑ Lahr, M. Mirazón; Rivera, F.; Power, R. K.; Mounier, A.; Copsey, B.; Crivellaro, F.; Edung, J. E.; Fernandez, J. M. Maillo; Kiarie, C. (2016). "Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya". Nature. 529 (7586): 394–398. PMID 26791728. doi:10.1038/nature16477.
  21. ↑ Lynch, B. M.; Robbins, L. H. (1979-07-01). "Cushitic and Nilotic Prehistory: New Archaeological Evidence from North-West Kenya". The Journal of African History. 20 (3): 319–328. ISSN 1469-5138. doi:10.1017/S0021853700017333.
  22. ↑ Ehret, Christopher (1998). Eastern and Southern Africa in World History 1000 BC to AD 400. University of Virginia Press. ISBN 9780813920573.
  23. 1 2 3 Wright, David K.; Forman, Steven L.; Kiura, Purity; Bloszies, Christopher; Beyin, Amanuel (2015-06-27). "Lakeside View: Sociocultural Responses to Changing Water Levels of Lake Turkana, Kenya". African Archaeological Review. 32 (2): 335–367. ISSN 0263-0338. doi:10.1007/s10437-015-9185-8.
  24. ↑ Grillo, Katherine M.; Hildebrand, Elisabeth A. (2013-06-01). "The context of early megalithic architecture in eastern Africa: the Turkana Basin c. 5000-4000 BP". Azania: Archaeological Research in Africa. 48 (2): 193–217. ISSN 0067-270X. doi:10.1080/0067270X.2013.789188.
  25. ↑ D.K. Wright, K.M. Grillo & R. Soper. "Stone Cairns and Material Culture of the Middle to Late Holocene, Lake Turkana". www.african-archaeology.de (in German). Retrieved 2017-03-07.
  26. ↑ McCabe, Terrance (1990). "Success and Failure: The Breakdown of Traditional Drought Coping Institutions Among the Pastoral Turkana of Kenya". ResearchGate. Retrieved 2017-03-07.
  27. ↑ MONTCLOS, M.-A. P. D.; KAGWANJA, P. M. (2000-06-01). "Refugee Camps or Cities? The Socio-economic Dynamics of the Dadaab and Kakuma Camps in Northern Kenya". Journal of Refugee Studies. 13 (2): 205–222. ISSN 0951-6328. doi:10.1093/jrs/13.2.205.
  28. ↑ Lake Turkana Wind Power
  29. ↑ Africa’s Largest Wind Project Advances, New York Times, 16 March 2010

Sources


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