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Lake Tana

From Wikipedia
Lake Tana
lake
InflowsLesser Abay River, Reb River, Gumara River, Magech River Edit
OutflowsBlue Nile, Tana-Beles interbasin water transfer Edit
Drainage basinNile basin Edit
Basin countryEthiopia Edit
CountryEthiopia Edit
Edey de administrative territorial entity insydAmhara Region Edit
Coordinate location12°0′0″N 37°15′0″E Edit
Map

Lake Tana (Amharic: ጣና ሐይቅ, romanized: T’ana ḥāyik’i; previously dem transcribe as Tsana[1]) be de largest lake for Ethiopia insyd den a source of de Blue Nile. Wey dem locate am for Amhara Region insyd for de north-western Ethiopian Highlands insyd, de lake be approximately 84 kilometres (52 miles) long den 66 kilometres (41 miles) wide, plus a maximum depth of 15 metres (49 feet),[2] den an elevation of 1,788 metres (5,866 feet).[3] De Gilgel Abay, Reb den Gumara rivers feed Lake Tana. Ein surface area dey range from 3,000 to 3,500 square kilometres (1,200 to 1,400 square miles), wey dey depend for season den rainfall top. Dem regulate de lake level since de construction of de control weir wey de lake dey discharge into de Blue Nile. Dis dey control de flow to de Blue Nile Falls (Tis Abbai) den hydro-power station.

For 2015 insyd, dem nominate Lake Tana region as a UNESCO Biosphere Reserve wey dey recognize ein national den international natural den cultural importance.[4]

Ovaview

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Views ova Lake Tana
De Island Church for Lake Tana top
A local tour guide dey demonstrate how a stone dey struck to signal meal times at a monastery for Zege Peninsula top
Beginning of de Blue Nile river by ein outlet from Lake Tana
A resort hotel for Lake Tana top for Bahir Dar insyd

Volcanic activity form Lake Tana, wey block de flow of rivers wey dey inflow for de early Pleistocene insyd, about 5 million years ago.[5]

De lake be originally much larger dan e dey today. Seven large permanent rivers dey feed de lake as well as 40 small seasonal rivers. De main tributaries to de lake be Gilgel Abbay (Little Nile River), den de Megech, Gumara, den Rib rivers.[5]

Lake Tana get a number of islands, wey number dey vary plus de lake ein level. E fell about 6 feet (1.8 m) for de last 400 years insyd. According to Manuel de Almeida, a Portuguese missionary for de early 17th century insyd, der be 21 islands, seven anaa eight of wey get monasteries for dem top "formerly large, but rydee diminish much.[6] "Wen James Bruce visit de area for 1771 insyd, he note dat de locals wey dem count 45 islands wey dem inhabit, but state he believe dat "de number go fi be about eleven."[6] Anton Stecker, for 1881 insyd, make a detailed examination of de lake, wey e enable substantially accurate maps,[1] den dem count 44 islands.[7] A 20th-century geographer name 37 islands, of wey he believe 19 have anaa had monasteries anaa churches for dem top.[6]

Dem keep remains of ancient Ethiopian emperors den treasures of Ethiopic Christianity for de isolated island monasteries (wey dey include Kebran Gabriel, Ura Kidane Mehret, Narga Selassie, Daga Estifanos, Medhane Alem of Rema Island, Kota Maryam, den Mertola Maryam). For de island of Tana Qirqos top be a rock wey dem show to Paul B. Henze, for wey dem tell am Mary, mother of Jesus rest for ein journey back from Egypt; dem sanso tell am say Frumentius, wey introduce Christianity to Ethiopia, be "allegedly buried for Tana Cherqos top."[8] Dem inter de body of Yekuno Amlak for de monastery of St. Stephen insyd for Daga Island top. Emperors wey tombs sanso be for Daga top dey include Dawit I, Zara Yaqob, Za Dengel, den Fasilides. Oda important islands for Lake Tana insyd dey include Dek, Mitraha, Gelila Zakarias, Halimun den Briguida.

Dem believe dem already build monasteries during de Middle Ages ova earlier religious sites. Dem dey include de fourteenth-century Debre Maryam, den de eighteenth-century Narga Selassie, Tana Qirqos, wey dem say dem already house de Ark of de Covenant before dem move am to Axum, den Ura Kidane Mehret, wey dem know give ein regalia. A ferry service dey link Bahir Dar plus Gorgora via Dek den various lakeshore villages.

Der sanso be Zege Peninsula for de southwest portion of de lake top. Zege be de site of de Azwa Maryam monastery.

Lake Tana sanso be a central location of de Beta Israel, wey dey complete plus de only Jewish monasteries for de world insyd,[9] before demma immigration to Israel.

Water characteristics den floods

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Wey dem compare to oda tropical lakes, de waters for Lake Tana insyd dey relatively cold, wey e typically range from about 20 to 27 °C (68–81 °F). De water get a pH wey be neutral to samwat alkaline den ein transparency be quite low.[10]

Sekof de large seasonal variations for de inflow of ein tributaries, rain den evaporation insyd, de water levels of Lake Tana dey typically vary by 2–2.5 m (6.6–8.2 ft) for a year insyd, wey dey peak for September–October insyd just after de main wet season. Wen de water levels dey high, de plains around de lake often flood den dem connect oda permanent swamps for de region insyd to de lake.[10]

Fauna

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Lily pads dey float near de shore for Lake Tana top

Since der dey no inflows dat dey link de lake to oda large waterways den de main outflow, de Blue Nile, de Blue Nile Falls obstruct am, de lake dey support a highly distinctive aquatic fauna, wey generally dem relate am to species from de Nile Basin.[11] De lake ein nutrient levels dey low.[10]

Fish

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Der be 27 fish species for Lake Tana insyd den 20 of dem be endemic.[10] Dis dey include one of only two cyprinid species flocks wey dem know (de oda, from Lake Lanao for de Philippines insyd, introduced species already decimate am). E dey consist of 15 relatively large, up to 1 m (3 ft 3 in) long, Labeobarbus barbs dat dem formerly include for Barbus insyd instead.[11][12] Among dem, L. acutirostris, L. longissimus, L. megastoma den L. truttiformis dey strictly piscivorous, den L. dainellii, L. gorguari, L. macrophtalmus den L. platydorsus dey mostly piscivorous.[10] Demma most important prey be de small Enteromius den Garra species.[10][12][13] De remaining Labeobarbus for Lake Tana insyd get oda specialized feeding habits: L. beso (non-endemic den dem no closely relate am to de odas) dey feed for algae top, L. surkis mostly for macrophytes top, L. gorgorensis for macrophytes top den molluscs, L. brevicephalus for zooplankton top (howeva, juveniles of all members of de species flock dey feed for zooplankton top), L. osseensis for macrophytes top den adults insects, den L. crassibarbis, L. intermedius (non-endemic buh dem closely relate am to de odas), L. nedgia den L. tsanensis for benthic invertebrates like chironomid larvae top. Among de endemic Labeobarbus, eight species spawn for de lake ein wetlands insyd den de remaining move seasonally into ein tributaries wey dem spawn.[10]

For addition to de Labeobarbus species flock insyd, de endemic species be Enteromius pleurogramma, E. tanapelagius, Garra regressus den Afronemacheilus abyssinicus (one of only two African stone loaches). De remaining non-endemic species be Nile tilapia (widespread for Africa insyd, buh plus de endemic subspecies tana for de lake insyd), E. humilis, G. dembecha, G. dembeensis den de large African sharptooth catfish.[10][11]

Fishing den threats

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Various Labeobarbus barbs den African sharptooth catfish wey dem catch for de lake insyd

Lake Tana dey support a large fishing industry, wey mainly dey base for de Labeobarbus barbs top, Nile tilapia den sharptooth catfish. According to de Ethiopian Department of Fisheries den Aquaculture, dem land 1,454 tons of fish for 2011 insyd at Bahir Dar, wey de department dem estimate am be 15% of ein sustainable amount.[14] Nevertheless, for a review insyd dat compare catches for 2001 insyd to dem ten years earlier, dem find dat typical sizes of both de tilapia den de catfish significantly decrease, den populations of de Labeobarbus barbs dat dey breed for de tributaries insyd decline significantly.[10] Among de endemic fish, dem consider most threatened (endangered anaa vulnerable) anaa data deficient (available data insufficient give evaluating a status) by de IUCN.[15] For de early 2000s insyd, de local government give de first time introduce a fisheries legislation den dem hope dis go get a positive effect for de fish populations top.[10]

Oda serious threats be habitat destruction den pollution. Bahir Dar becam a large city den e dey rapidly grow; dem generally release ein wastewater directly into de lake.[10] De vegetation for de lake ein wetlands insyd, wey be an important nursery give de Labeobarbus den oda fish, dem already clear am at a fast pace. A potentially serious threat to de unique ecosystem go be an introduction of a large den efficient predatory species like de Nile perch, wey dem implicate am for numerous extinctions insyd for Lake Victoria insyd. De piscivorous Labeobarbus of Lake Tana be relatively inefficient predators dat only fi take fish up to about 15% of de length of de predator einself.[10]

Oda fauna

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Great white pelicans for Lake Tana top

Among oda fauna, de lake dey support relatively few invertebrates: Der be fifteen species of mollusks, wey dey include one endemic, den sanso an endemic freshwater sponge.[11]

About 230 species of birds, wey dey include more dan 80 wetland birds such as de great white pelican, African darter, hamerkop, storks, African spoonbill, ibis, ducks, kingfishers den African fish eagle, dem know dem from Lake Tana.[10] E be an important resting den feeding ground give many Palearctic migrant waterbirds.[11]

Der dey no crocodiles, buh de African softshell turtle den Nile monitor dem already record dem near de Blue Nile outflow from de lake.[16] Hippos dey present, mostly near de Blue Nile outflow.[10]

References

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  1. 1 2 Garstin & Cana 1911.
  2. ↑ Statistical Abstract of Ethiopia. 1967–1968.
  3. ↑ "Lake Tana, source of the Blue Nile". Observing the Earth. European Space Agency. 5 November 2004. Retrieved 4 November 2013.
  4. ↑ Homepage of Lake Tana Biosphere Reserve
  5. 1 2 Vijverberg, Jacobus; Sibbing, Ferdinand A.; Dejen, Eshete (2009). "Lake Tana: Source of the Blue Nile". The Nile. Monographiae Biologicae. Vol. 89. pp. 163–192. doi:10.1007/978-1-4020-9726-3_9. ISBN 978-1-4020-9725-6.
  6. 1 2 3 Beckham, C. F.; Huntingford, G. W. B. (1954). Some Records of Ethiopia, 1593-1646. Series 2. London: Hakluyt Society. p. 35 and note.
  7. ↑ Hayes, A.J. (1905). The Source of the Blue Nile: A Record of a Journey Through the Soudan to Lake Tsana in Western Abyssinia, and of the Return to Egypt by the Valley of the Atbara. Smith, Elder & Company. p. 73. Retrieved 28 May 2021.
  8. ↑ Henze, Paul B. (2000). Layers of Time: A History of Ethiopia. New York: Palgrave. p. 73. ISBN 978-0312227197.
  9. ↑ Kribus, Bar; Krebs, Verena (2018). "Beta Israel (Ethiopian Jewish) Monastic Sites North of Lake Tana Preliminary Results of an Exploratory Field Trip to Ethiopia in December 2015". Entangled Religion. 6: 309–344. doi:10.13154/er.v6.2018.309-344.
  10. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Vijverberg, J.; F.A. Sibbing; E. Dejen (2009). "Lake Tana: Source of the Blue Nile". In H.J. Dumont (ed.). The Nile. Monographiae Biologicae. Vol. 89. Springer Science + Business Media B.V. pp. 163–193. ISBN 978-1-4020-9725-6.
  11. 1 2 3 4 5 "Lake Tana". Freshwater Ecoregions of the World. 2008. Archived from the original on 5 October 2011. Retrieved 24 January 2012.
  12. 1 2 de Graaf, Martin; Dejen, Eshete; Sibbing, Ferdinand A.; Osse, Jan W. M. (2000). "Barbus tanapelagius, A New Species from Lake Tana (Ethiopia): its Morphology and Ecology". Environmental Biology of Fishes. 59 (1): 1–9. Bibcode:2000EnvBF..59....1D. doi:10.1023/A:1007608208630.
  13. ↑ de Graaf, Martin; Megens, Hendrik-Jan; Samallo, Johannis; Sibbing, Ferdinand (2007). "Evolutionary origin of Lake Tana's (Ethiopia) small Barbus species: indications of rapid ecological divergence and speciation". Animal Biology. 57 (1): 39–48. doi:10.1163/157075607780002069.
  14. ↑ "Information on Fisheries Management in the Federal Democratic Republic of Ethiopia" Archived 28 February 2008 at the Wayback Machine, Food and Agricultural Organization (FAO), January 2003
  15. ↑ "The IUCN Red List of Threatened Species". IUCN. 2019. Retrieved 18 November 2019.
  16. ↑ Largen and Spawls (2010). The Amphibians and Reptiles of Ethiopia and Eritrea. ISBN 978-3-89973-466-9

Works cited

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Dem retrieve am from "https://gpe.wikipedia.org/w/index.php?title=Lake_Tana&oldid=108589"