|Central coordinates||38o 58.62' East 8o 41.76' North|
|IBA criteria||A1, A4i, A4iii|
|Altitude||1,800 - 1,900m|
|Year of IBA assessment||1996|
Site description Green Lake is one of a number of crater lakes near Debre Zeit in East Shewa Zone, 50 km west of the zonal capital, Nazaret. Like all of the volcanic crater lakes in this area, Green Lake is a closed system, being fed directly by rain and by water flowing down from the crater rims. The maximum depth is 32 m, and the water is highly alkaline. The lake is encircled by an almost continuous crater wall with steep and, in places, precipitous slopes rising almost 200 m above the water. Cliffs and scattered trees that grow on these cliffs make up the major habitats surrounding the lake. Drier slopes around the lake support various Acacia spp. where disturbance and grazing are minimal. Severely eroded areas are either bare or carry highly drought-tolerant shrubs, scramblers and succulents, the most conspicuous of which are Carissa edulis, Euphorbia tirucalli, Pterolobium stellatum, Caesalpina spinosa and Opuntia ficus-indica. The water exclusively supports an abundant population of the blue-green alga Spirulina platensis, as a result of which the water appears green (hence the name of the lake). The dense algal growth in the lake produces a huge amount of oxygen during the day, but at night photosynthesis ceases, the algae use up the oxygen, and the lake becomes almost completely anaerobic by daybreak. This phenomenon partly explains the absence of fish from the lake. Debre Zeit is an important town (see site ET032).
Key Biodiversity See Box for key species. This lake is important for the large concentrations of waterfowl that it supports on a seasonal basis. Recent surveys have recorded c.80 species, including a range of Palearctic and Afrotropical waders, ducks and geese. Green Lake supports, along with the other Debre Zeit lakes, a wintering population of 10–15 Aythya nyroca. Of particular importance are the substantial numbers of Phoenicopterus minor known to use the lake: over 25,000 (including 2,000 dead birds) were recorded during a survey in November 1995, though a second survey in October 1996 found only 25. Other significant waterbird counts include Tachybaptus ruficollis (500 in 1995, 250 in 1996), Anas clypeata (700) and Himantopus himantopus (300).
Non-bird biodiversity: None known to BirdLife International.
|Species||Season||Period||Population estimate||Quality of estimate||IBA Criteria||IUCN Category|
|Ferruginous Duck Aythya nyroca||winter||1996||4-5 individuals||-||A1||Near Threatened|
|Lesser Flamingo Phoeniconaias minor||non-breeding||1996||25,000 individuals||-||A1, A4i||Near Threatened|
|A4iii Species group - waterbirds||non-breeding||1996||20,000-49,999 individuals||unknown||A4iii|
|Land-use||Extent (% of site)|
References Belay et al. (1986), Brook Lemma (1994), Ministry of Natural Resources Development (1995), Mohr (1961), Talling and Wood (1988).
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Recommended citation BirdLife International (2015) Important Bird Areas factsheet: Green Lake. Downloaded from http://www.birdlife.org on 30/08/2015
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