Rift Valley lakes

The Rift Valley Lakes are a group of lakes formed by the Great Rift Valley of eastern Africa. These lakes include some of the oldest, largest and deepest lakes in the world, and are a freshwater ecoregion of great biodiversity. The Ethiopian Rift Valley lakes are the northernmost of the African Rift Valley lakes. In central Ethiopia the Great Rift Valley splits the Ethiopian highlands into northern and southern halves, and the Ethiopian Rift Valley lakes occupy the floor of rift valley between the two highlands. Most of the Ethiopian Rift Valley lakes do not have an outlet, and most are alkaline. The largest of these lakes is Lake Abaya (1160 km², elevation 1285 m); other major lakes include Lake Chamo (551 km², 1235 m), Lake Awassa (129 km², elevation 1708 m), Lake Zway (485 km², elevation 1636 m), Lake Abijata (205 km², elevation 1573 m), and Lake Koka (250 km², elevation 1590 m). Lake Tana (3600 km², elevation 1788 m), the source of the Blue Nile, is not a Rift Valley lake, but lies in the Ethiopian highlands north of the Rift Valley.

South of the Ethiopian highlands, the Rift Valley splits in two. The Eastern Rift is home to the Kenyan Rift Valley lakes, and most of the Central African Rift Valley lakes lie in the Western Rift. The Kenyan section of the Rift Valley is home to eight lakes, of which two are freshwater and the rest alkaline. The largest of the Kenyan lakes is Lake Turkana (elevation 360 m), a large alkaline lake on the border of Kenya and Ethiopia with an area of 6405 km². Lake Logipe is a seasonal lake just south of Lake Turkana. Further south are lakes Baringo, Bogoria, Nakuru, Elmenteita, Naivasha and Magadi.

Lake Baringo is the second largest of the Kenyan Rift Valley lakes at 80 square miles, and is one the two fresh water lakes in Kenya. Four hundred bird species have been listed in the area, and the Goliath heronry is located on a rocky islet in the lake known as Gibraltar. Lake Naivasha is Kenya's other freshwater lake, with an area of 160 square kilometres, which varies somewhat with rainfall. It is the highest of the Kenya's Rift Valley lakes at an altitude of 1,890 m (5900 ft). Njorowa gorge used to form the lake's outlet, but it is now high above the lake and the forms the entrance to Hell's Gate National Park. Over 450 species of birds are found in the immediate area. Kenya's other rift valley lakes are small shallow soda lakes, with crystallised salt turning the shores white. The lakes are famous for the large flocks of flamingo that feed on the crustaceans. Lake Nakuru (40 km², elevation 1759 m) is a national park since 1968, and Lake Bogoria (34 km², elevation 960 m) is a national preserve. The eastern rift continues into Tanzania, where alkaline Lake Natron and Lake Eyasi host huge flocks of flamingoes.

The lakes of the Western or Albertine Rift, together with Lake Victoria, include the largest, deepest and oldest of the Rift Valley lakes. The Central African lakes are freshwater, home to an extraordinary number of endemic species. Upwards of 800 cichlid fish (Cichlidae) species live in the lakes (See Hubert Sauper's Darwins Nightmare and the resulting plummet in biodiversity). In addition to the cichlids, endemic species of Clariidae, Claroteidae, Mochokidae, Poeciliidae, Mastacembelidae, Centropomidae, Cyprinidae, Clupeidae and other fish families are also found in these lakes. The lakes are also important habitats for a number of amphibian species, including Bufo kisoloensis, Bufo keringyagae, Cardioglossa cyaneospila, and Nectophryne batesii.

The World Wildlife Fund has designated the Rift Valley lakes one of its Global 200 priority ecoregions for conservation.

Lake Victoria (elevation 1134 m), with an area of 68,800 km², is the largest lake in Africa, but is not actually within the rift valley; it occupies a depression between the eastern and western rifts, formed by the uplift of the rifts to either side. Lake Albert (5300 km², elevation 615 m) is the northernmost lake in the western rift. Lake Albert, Lake Victoria, and Lake Edward (2325 km², elevation 912 m), which drains north into Lake Albert, are part of the Nile River watershed. Just south of Lake Edward in the Western rift is Lake Kivu (2220 km², elevation 1460 m), which empties into Lake Tanganyika via the Ruzizi River. Lake Tanganyika (32,000 km², elevation 773 m) is the deepest of the Rift Valley lakes (more than 1400 meters), and is thought to be the second-oldest lake on the planet (after Lake Baikal). Lake Tanganyika is part of the Congo River watershed, into the Congo via the Lukuga River. Lake Mweru (4350 km², elevation 922 m) lies southwest of Lake Tanganyika on the border between the Democratic Republic of Congo and Zambia, in a geologic depression called the Lake Mweru-Luapula graben, which is outside the Albertine rift, but is part of the African rift system.

The alkaline Lake Rukwa lies in Tanzania to the southeast of Lake Tanganyika and north of Lake Malawi, in a parallel branch of the rift system. Lake Malawi (30,000 km², elevation 500 m) lies south of Lake Tanganyika in the rift valley, and is the second deepest at over 700 meters. It empties south into smaller Lake Malombe, which is drained by the Shire River, a tributary of the Zambezi River. Lake Chilwa (1750 km², elevation 622 m) lies southeast of Lake Malombe, and is the southernmost of the Rift Valley lakes.

Lake Victoria, Lake Tanganyika, and Lake Malawi are sometimes collectively known as the African Great Lakes.

Two other lakes on the Great Rift Valley — the Dead Sea and the Sea of Galilee — are located in Asia.