Turkana, Lake (Kenya and Ethiopia)

Lake Turkana () is a saline lake in the Kenyan Rift Valley, predominantly in northern Kenya; the far northern end crosses into Ethiopia. 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 22nd. Lake Turkana is now threatened by the construction of the Gilgel Gibe III Dam in Ethiopia due to the damming of the Omo River which supplies most of the lake's water. Although the lake commonly has been—and to some degree still is—used for drinking water, its salinity (slightly brackish) and very high levels of fluoride (much higher than in fluoridated water) generally make it unsuitable for drinking; it has also been a source of diseases spread by contaminated water. Increasingly, communities around the lake rely on underground springs for drinking water. The same characteristics that make it unsuitable for drinking limit its use for irrigation. 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 southern 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 vary. For example, the level fell by 10 metres (33 ft) between 1975 and 1993. Despite the lack of outflow, in ecology it is often regarded as a part of — or at least associated with — the Nile basin because of its prehistoric connection to this system and the similarities in their aquatic faunas. Due to local temperatures — the lake water is 27–31 °C [81–88 °F], and the mean air temperature of the region is similar or slightly higher — aridity and geographic inaccessibility, the lake retains its wild character. Nile crocodiles are found in great abundance on the shore flats. The rocky shores are home to scorpions and carpet vipers. The lake is rich in fish and fishing is very important to the local economy, but is threatened by falling water levels and overfishing. 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. The area 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.