Lake Manyara, Hydrology and basin

Lake Manyara is an lake located in Monduli District of Arusha Region, Tanzania and is the seventh-largest lake of Tanzania by surface area, at 470-square-kilometre (180 sq mi). It is a shallow, alkaline lake in the Natron-Manyara-Balangida branch of the East African Rift. The northwest quadrant of the lake (about 200 sq, km.) is included within Lake Manyara National Park and it is part of the Lake Manyara Biosphere Reserve, established in 1981 by UNESCO as part of its Man and the Biosphere Programme.

There are differing explanations for how Lake Manyara got its name. The name Manyara may come from the Maasai word “emanyara”, which is the spiky, protective enclosure around a family homestead (boma). Possibly the 600 m high rift escarpment hems in the lake, like the enclosure around a Maasai boma.[5] Another theory is that the Mbugwe tribe, who live in the Lake Manyara area, may have given the lake its name based on the Mbugwe word manyero, meaning a trough or place where animals drink

Hydrology and basin
Lake Manyara has a catchment area of about 18,372 km2 with elevations between 938 m and 3633 m above sea level. The lake is in a closed basin with no outflow, wherein water is only lost by evaporation. It is fed by underground springs, but the vast majority of the inflow comes from rainwater fed permanent and ephemeral rivers that drain the surrounding catchment. The lake’s depth and the area it covers fluctuates significantly.

At its maximum, during the wet season, the lake is 40 km wide by 15 km with a maximum depth of 3.7 m. In 2010, a bathymetry survey showed the lake to have an average depth 0.81 m, and a maximum depth of about 1.18 m. In extreme dry periods the surface area of the lake shrinks as the waters evaporate and at times the lake has dried up completely. Lake Manyara is a soda or alkaline lake with a pH near 9.5, and it is also high in dissolved salts.

The water becomes increasingly brackish in the dry season as water evaporates and salts accumulate.[9] During dry spells, large areas of mud flats become exposed along the shore.[8] These alkaline flats sprout into grasslands, attracting grazing animals, including large herds of buffalo, wildebeest and zebra.[3] The Western side of the lake is flanked by a steep rift escarpment, to the North are the Ngorongoro highlands, while in the East and Southeast an undulating plain with isolated volcanic mountains gives way to a peneplain. Several springs, streams, wetlands and smaller lakes, both perennial and seasonal, drain into the lake. The shores of the saline lake host at its Northern tip the town of Mto wa Mbu with its irrigation agriculture.

Fish
The main fish species inhabiting the lake are catfish and tilapia. There is a small fishery, but fish only tend to be found near the inflow areas, where salt concentrations are lower. Lake Manyara is the type locality for the endangered fish Oreochromis amphimelas, a species of in the cichlid family, endemic to Tanzania, found in Lake Manyara and a number of other saline lakes with closed basins. Exploitation is prohibited in the parts of Lake Manyara within the National Park and the protected park areas provide important seed stock for the replenishment of fished populations.

Birds
Lake Manyara National Park is known for flocks of thousands flamingos that feed along the edge of the lake in the wet season. At times, there have been over an estimated 2 million individuals of various species of water birds. The following table summarizes the most numerous species, according to the Important Bird Areas factsheet: Lake Manyara.