Lake Malawi, also known as Lake Nyasa in Tanzania and Lago Niassa in Mozambique, () is an African Great Lake and the southernmost lake in the East African Rift system, located between Malawi, Mozambique and Tanzania.
It is the fourth largest freshwater lake in the world by volume, the ninth largest lake in the world by area and the third largest and second deepest lake in Africa. Lake Malawi is home to more species of fish than any other lake in the world, The Mozambique portion of the lake was officially declared a reserve by the Government of Mozambique on June 10, 2011, while in Malawi a portion of the lake is included in Lake Malawi National Park.
Lake Malawi is a meromictic lake, meaning that its water layers do not mix. The permanent stratification of Lake Malawi's water and the oxic-anoxic boundary are maintained by moderately small chemical and thermal gradients.
Geography
Lake Malawi is between Evaporation accounts for more than 80% of the water loss from the lake, considerably more than the outflowing Shire River. The outflows from Lake Malawi into the Shire River are vital for the economy as the water resources support hydropower, irrigation and downstream biodiversity.
Concerns have been raised over the future climate change impacts of Lake Malawi due to the recent decline in lake levels and the overall drying trend. The climate in the lake region is already experiencing changes, with the temperatures predicted to increase throughout the country.
The lake is about southeast of Lake Tanganyika, another of the great lakes of the East African Rift.
The Lake Malawi National Park is located at the southern end of the lake.
<gallery widths="180px">
File:Lake Malawi00.jpg|Lake Malawi (1967)
File:Mwaya Beach, Malawi.jpg|Mwaya Beach
File:Monoxylon beach Lake Malawi 1557.jpg|Beach at Cape Maclear near Monkey Bay
</gallery>
Geological history
thumb|left|upright=1.75|[[Topographic profile of Lake Malawi's rift shoulder]]
thumb|The [[East African Rift (red) with the Rift Valley lakes, Malawi being in the south]]
Malawi is one of the major Rift Valley lakes and an ancient lake. The lake lies in a valley formed by the opening of the East African Rift, where the African tectonic plate is being split into two pieces. This is called a divergent plate tectonics boundary. Malawi has typically been estimated to be 1–2 million years old (mya), but more recent evidence points to a considerably older lake with a basin that started to form about 8.6 mya and deep-water condition first appeared 4.5 mya.
The water levels have varied dramatically over time, ranging from almost below current level to above. The thermocline is located at a depth of . The water is very clear for a lake and the visibility can be up to , but slightly less than half this figure is more common and it is below in muddy bays. However, during the rainy season months of January to March, the waters are more muddy due to muddy river inflows.
European colonisation
The Portuguese trader Candido José da Costa Cardoso was the first European to visit the lake in 1846. David Livingstone reached the lake in 1859, and named it Lake Nyasa. The Lake of Stars nickname came after Livingstone observed lights from the lanterns of the fishermen in Malawi on their boats, that resemble, from a distance, stars in the sky. Later, after experiencing the unpredictable and extremely violent gales that sweep through the area, he also referred to it as the Lake of Storms.
Borders
thumb|Dashed line: current [[Malawi border <br />Dotted line: Tanzanian claim]]
Tanzania–Malawi dispute
The partition of the lake's surface area between Malawi and Tanzania is under dispute. Tanzania claims that the international border runs through the middle of the lake. On the other hand, Malawi claims the whole of the surface of this lake that is not in Mozambique, including the waters that are next to the shoreline of Tanzania. Malawi currently administers these waters. Both sides cite the Heligoland Treaty of 1890 between the United Kingdom and Germany concerning the border. The wrangle in this dispute occurred when the British colonial government, just after they had captured Tanganyika from Germany, placed all of the waters of the lake under a single jurisdiction, that of the territory of Nyasaland, without a separate administration for the Tanganyikan portion of the surface. Later in colonial times, two jurisdictions were established.
The dispute came to a head in 1967 when Tanzania officially protested to Malawi; however nothing was settled. Occasional flare-ups of conflict occurred during the 1990s and in the 21st century. In 2012, Malawi's oil exploration initiative brought the issue to the fore, with Tanzania demanding that exploration cease until the dispute was settled.
Malawi–Mozambique border
In 1954, an agreement was signed between the British and the Portuguese making the middle of the lake their boundary with the exception of Chizumulu Island and Likoma Island, which were kept by the British and are now part of Malawi. entered service in 1935. The ferry entered service in 1951. In recent years she has often been out of service, but when operational she runs between Monkey Bay at the southern end of the lake to Karonga on the northern end, and occasionally to the Iringa Region of Tanzania. The ferry entered service in 1980. She normally serves the southern part of the lake but if Ilala was out of service she operated the route to Karonga. The Tanzanian ferry was built in 1988. Her operator was the Tanzania Railway Corporation Marine Division until 1997, when it became the Marine Services Company Limited. Songea plies weekly between Liuli and Nkhata Bay via Itungi and Mbamba Bay.
Wildlife
thumb|An [[African fish eagle catching a fish in Lake Malawi]]
Wildlife found in and around Lake Malawi or Nyasa includes Nile crocodiles, hippopotamus, monkeys, and a significant population of African fish eagles that feed off fish from the lake.
Fish
Fishing
thumb|left|[[Lake Malawi sardines (Engraulicypris sardella) spread out to dry on the shore of the lake]]
Lake Malawi has for millennia provided a major food source to the residents of its shores since its waters are rich in fish. Among the most popular are the four species of chambo, consisting of any one of four species in the subgenus Nyasalapia (Oreochromis karongae, O. lidole, O. saka and O. squamipinnis), as well as the closely related O. shiranus. Other species that support important fisheries include the Lake Malawi sardine (Engraulicypris sardella) and the large kampango catfish (Bagrus meridionalis). A drop in the lake's water level represents another threat, and is believed to be driven by water extraction by the increasing human population, climate change and deforestation. O. karongae and O. squamipinnis by about 94%, and O. lidole might already be extinct) and they are now seriously threatened. The IUCN recognises 117 species of Malawi cichlids as threatened; some of these have tiny ranges and may be restricted to rocky coastlines only a few hundred metres long.