A very large, isolated, chloro-carbonate alkaline lake, the northernmost and by far the largest of the chain of Rift Valley lakes in Kenya. The Omo river delta at the extreme northern end of the lake lies within Ethiopia (IBA ET069). Turkana’s water is brackish, but drinkable, and the lake holds freshwater fish. The c.600 km of lake shore vary greatly in substrate, from rock (most of the southern sector, the central eastern shore, and North, Central and South Islands) to pebble, sand (most of the north-western shore, and patches elsewhere) and mud (at Loiyengalani, El Molo and Allia Bays, the Omo delta and the inlets of the Turkwel and Kerio rivers). Beds of the submerged plant Potamogeton pectinatus occur in the most sheltered muddy bays. The country surrounding the lake is semi-desert with sparse vegetation: annual rainfall averages less than 250 mm (substantially less in some places), and it may not rain for several years at a stretch. South and Central Islands are National Parks and, in the north-east, c.13% of the shoreline is protected within Sibiloi National Park.
See Box for key species. Turkana is an extremely important waterbird site: 84 waterbird species, including 34 Palearctic migrants, have been recorded here. Over 100,000 Calidris minuta may winter, representing more than 10% of the entire East African/South East Asian wintering population (cf. Rose and Scott 1997). As well as supporting many wintering Palearctic migrants, the lake is a key stop-over site for birds on passage. Waterbirds are distributed all around the lake, but the highest densities are on mud and pebble shores; particular concentrations occur in sheltered muddy bays and the Omo delta. At least 23 species breed here, including Ardea goliath, and up to 50 pairs of the regionally threatened Rynchops flavirostris have bred on Central Island (but have now shifted to less disturbed localities). Other regionally threatened species include Casmerodius albus (occurs in small numbers, with 60 estimated in February 1992); Ephippiorhynchus senegalensis (nine estimated in February 1992) and Circaetus cinerascens.
Non-bird biodiversity: Lake Turkana is rich in fish, with 47 species, seven of which are endemic. The sheltered muddy bays with beds of waterweed Potamogeton are important for fish spawning. The fish in turn support a large population (estimated at some 14,000 in 1968) of Crocodylus niloticus.
Pressure/threats to key biodiversity
Most of the lake has no formal protection, and in this wild and remote area the protection given by National Park status is largely nominal. Fortunately, direct human pressure on the lake is relatively low. Turkana’s water level has been dropping steadily for many years (a decrease of 10 m was recorded between 1975 and 1992), mainly due to reduced inflow from the Omo river that supplies 90% of the lake’s water. The Omo flows from the Ethiopian Highlands, where irrigation projects and the effects of prolonged drought have diminished its flow. Important Kenyan inflows, such as the Turkwel, have also been substantially reduced in recent years by hydro-power and irrigation schemes. Some islands that supported nesting waterbirds are now joined to the mainland and have been overrun by goats. Disturbance by fishermen seems to be a general problem for the island-nesting birds: in particular, fishermen’s camps on Central Island have forced the Rynchops flavirostris that nested there to shift elsewhere, and the present status of this breeding colony is unclear. Pressure on the fish populations is increasing, although attempts to institute industrial-scale-fishing projects have failed. Some bird species, particularly gulls, may benefit from the upsurge in fishing and fish drying. Human populations around the lake are becoming more sedentary; consequent overgrazing by livestock causes deterioration of the lakeshore vegetation, and erosion of soils in the very strong winds that characterize this area.