Lake Malawi

Lake Malawi
View from orbit
Lake type	Rift lake
Primary inflows	Ruhuhu River[1]
Primary outflows	Shire River[1]
Catchment area	k
Basin countries	Malawi, Mozambique, Tanzania
Max. length	560 km[1] to 580[2]
Max. width	75 km[1]
Surface area	29,600 km² (11,429 sq. mi.) [1]
Average depth	292 m[3]
Max. depth	706 m[3]
Water volume	8,400 km³[3]
Surface elevation	500 meters above sea level
Islands	Likoma and Chizumulu islets
References	[1][3]

Lake Malawi (also known as Lake Nyasa in most countries, or Lake Nyassa, Lake Niassa, or Lago Niassa in Mozambique), is an African Great Lake and the southmost lake in the Great Rift Valley system of East Africa. This lake, the third largest in Africa and the eighth largest lake in the world, is located between Malawi, Mozambique, and Tanzania. It is the second deepest lake in Africa, though its placid northern shore gives no hint of its depth. This great lake's tropical waters reportedly are the habitat of more species of fish than that of any other body of water on the Earth.^[4]

Geography

Lake Malawi or Lake Nyaza is between 560^[1] and 580 kilometres long^[2], and about 75 kilometres wide at its widest point. The total surface area of this lake is about 29,600 square kilometres (11,429 square miles).^[1] This lake has shorelines on western Mozambique, eastern Malawi, and southern Tanzania. The largest river flowing into this lake is the Ruhuhu River. This large freshwater lake has an outlet, which is the Shire River, a tributary that flows into the very large Zambezi River.^[2]

Lake Malawi lies in the Great Rift Valley that was 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. Lake Malawi or Nyaza itself is variously estimated at about 40,000 years old ^[1] or about one to two million years.^[5]

In addition, Lake Malawi or Nyaza is located about 350 kilometers southeast of Lake Tanganyika, another of the huge lakes of the Great Rift Valley.

European discovery and colonization

David Livingstone was the first European explorer to reach for the shores of this lake, arriving in 1859, and naming it "Lake Nyasa."^[2] Much of the African region surrounding this lake was soon claimed by the British Empire and formed into the colony of Nyasaland. Although the Portuguese took control of the eastern shore of this lake, the island of Likoma was used as a mission station by the Universities' Mission to Central Africa, and as a result, Likoma and the nearby islet of Chizumulu were incorporated into Nyasaland rather than to Mozambique. Today, these islets form lacustrine exclaves: Malawian land surrounded by Mozambiquian waters.

On August 16, 1914, Lake Malawi or Nyaza was the scene of a brief naval battle when the British gunboat Guendolen, commanded by a Captain Rhoades, heard that World War I had broken out, and he received orders from the British Empire's high command to "sink, burn, or destroy" the German Empire's only gunboat on the lake, the Hermann von Wissmann, commanded by a Captain Berndt. Rhoades's crew located the Hermann von Wissmann in a bay near "Sphinxhaven", in German East African territorial waters. Guendolen disabled the German boat with a single cannon shot from a range of about 2,000 yards. This very brief gunboat conflict was hailed by The Times in England as the British Empire's first naval victory of World War I.^[6][7] Up until that time, the lakeshore that is now in Tanzania had been a part of German East Africa.

The Borders of the Lake

A view of the lake from Likoma Island

The largest portion of the area of Lake Malawi or Nyaza is in Malawi. However, about a quarter of the area belongs to Mozambique. This area includes the waters surrounding the Malawian islets of Likoma and Chizumulu, which are this lake's only two inhabited islets. The islet of Likoma is dominated by a large stone and bric Anglican cathedral that was built by missionaries in the early 20th century. A notable feature of both islets is their significant number of baobab trees. The islets support a population of several thousand people, who in addition to being fishmen, grow plants such as cassavas, bananas, and mangoes for food.

Lake Nyasa or Lake Malawi ?

The geographic name of the lake itself is also disputed. Malawi claims that this lake is named "Lake Malawi", whereas most other countries (most notably Tanzania) and internationally-made maps state that the name of the lake is "Lake Nyasa". The origin of the dispute over the name of the lake has its background in geopolitical disputes that began before the independence of Malawi was achieved in 1964, when the territory had been known as "Nyasaland".

Further complications emerged for various political reasons during the 1960s, when President Hastings Banda of Malawi became the only African leader to establish diplomatic relations with the white-ruled country of South Africa. This recognition of the South African regime was fiercely repudiated by almost all other African leaders, including President Julius Nyerere of Tanzania. This contrasting in policies toward South Africa gave some more impetus to disputes between the Malawi and Tanzania, especially concerning the name of the Lake itself, and also the water boundary between the two countries.

For this same lake, the name "Lac Maravi" had been used on the map of "Afrique sud" by J. B. B. d'Anville, which was published in France in 1749. Stanley Livingstone's name for the lake was based on his colleague's misunderstanding of African languages of the area. When Livingstone asked his staff members, who were not from the area of the lake, to state its name for him, they said the word "nyasa", not realising that this was the local word for any large body of water (such as a lake). This name could also be spelled "niassa", "nyanja", or "nyanza", based on the other languages of the region.

Presently the dispute between the two governments over the lake's name is mostly dormant. Diplomatic relations between Malawi and Tanzania, and the relationships between their wildlife police forces and other associations are largely cordial.

Tanzania–Malawi dispute

The partition of Lake Nyasa's surface area between Malawi and Tanzania is under dispute. Tanzania claims that the international border runs through the middle of the lake^[8]. This is along the lines of the border that were set out between the German and British territories before 1914. 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. The foundations of this dispute were laid when the British colonial government, which had recently captured Tanganyika from Germany, placed all of the water under the jurisdiction of the territory of Nyasaland, without a separate administration for the Tanganyikan portion of the surface. This dispute has led to conflicts in the past, though in recent years, Malawi has declined to attempt to enforce any claims to the disputed portion.

Occasional flare-ups of conflict during the 1990s, and also sometimes in the 21st Century, have impacted fishing rights, particularly those of Tanzanian fishermen who reside on the lakeshore who have occasionally been accused of fishing in Malawian waters.

Transportation on the Lake

A jetty juts into the water at Nkhata Bay

Large-scale transportation between villages on the shores of Lake Malawi or Nyaza, and also between the lakeshore and the inhabited islets is provided by steamboats or motorboats on the lake, or else by air transportation. The steamship MV Ilala is the best known one, though in recent years it has often been out of service. When operational, this ship steams between Monkey Bay at the southern end of the lake to Karonga on the northern end, and occasionally to the Iringa Region of Tanzania.

Vessels travel about twice a week from Nkhata Bay on the lakeshore to the Likoma and Chizumulu islets, taking several hours to make the crossing. Neither of the islets has a usable port, and larger boats anchor offshore before transferring their passengers and cargoes to the islets in small watercraft.

Wildlife

An aquarium with fish species from Lake Malawi (Lincoln Park Zoo, Chicago)

Lake Malawi or Nyasa has for millennia provided a major food source to the residents of its shores since its waters are rich in fish such as the chambo, consisting of any one of four species of the cichlid genus Nyasalapia, and the kampango, a large catfish (Bagrus meridionalis). Some of the fish that are caught are exported from Malawi, but the wild population of fish is increasingly threatened by overfishing and water pollution.

The painted hunting dog is believed to be extinct in Malawi, with its last remaining population being spotted in the eastern Miombo woodlands just east of the lake.^[9] Other wildlife that is found in and around Lake Malawi or Nyasa include crocodiles, hippopotamus, monkeys, and a significant population of African fish eagles that feed off fish from the lake.

Cichlids

Lake Malawi is home to numerous cichlid species including Livingston's cichlid (Nimbochromis livingstonii).

Lake Malawi is noted for being the site of evolutionary radiations among several groups of animals, most notably cichlid fish. Several hundred endemic species are found in the lake, many of which have become popular among aquarium owners due to their bright colors. Recreating a Lake Malawi biotope^[10] to host cichlids became quite popular in the aquarium hobby. The cichlids of the lake are divided into two basic groups, loosely referred to as the haplochromines and the tilapiines. Within the first group, Haplochrominae, there are two subgroups. The first one consists of open water and sand dwelling species whose males display bright colors and whose females show a silvery coloration with sometimes irregular black bars or other markings. The second subgroup is known both locally and popularly as mbuna, which means "rockdwellers". The Mbuna species tend to be smaller, often specialized aufwuchs feeders, and often both sexes are brightly colored. All haplochromines from lake Malawi are mouthbrooders.

The second group, the tilapiines, comprises the only substrate-spawning species in the lake (Tilapia rendalli), in addition to the four mouthbrooding species of chambo (Nyasalapia).

Snails

The lake also supports populations of snails, some of which carry bilharzia. A survey in Monkey Bay in 1964 found two endemic species of snails of the genus Bulinus in the lake, and B. globosus and B. forskalli in lagoons separated from it. The latter species are known vectors of bilharzia, and larvae of the parasite were detected in water containing these, but in experiments C. Wright of the British Museum of Natural History was unable to infect the two species endemic to the lake with the parasites. The field workers, who spent many hours on and in the lake, did not find either B. globosus or B. forskalli in the lake itself.^[11]

There are a number of fish species in the lake that specialise in preying on snails, and the lake snails show behavioural modifications that give them some protection. One lives at the bases of rosettes of the plant Vallisneria, while the other burrows in the sand. The bilharzia vector, B. globosus, crawls over the leaves of aquatic plants and so is more susceptible to predation. In the early 1960s the snail-eating fish were still abundant, and bilharzia was not a problem to people bathing in the lake but they could contract it if they paddled in streams, ponds or swamps near the lake. Infective larvae may have been carried into the lake during floods, although they would have survived only a few days. More recently there have been reports of this disease being contracted in the lake. The apparent increase in risk may be associated with heavy fishing off the beaches over the past 40 years and with declines in the populations of snail-eating fish.^[12]

In addition to the potential vectors of bilharzia, there are a number of other snail and clam species which are endemic to the lake. Empty shells of large Lanistes are used as brood shelters by mbuna such as Pseudotropheus livingstonei, while a small catfish, which grows to less than 30 mm in length, uses smaller shells as brood shelters.^[12]

Water chemistry

Lake Malawi 1967

The water in Lake Malawi or Nyasa is typically slightly alkaline with a pH ranging from 7.7 to 8.6, a carbonate hardness of 107 to 142 mg L⁻¹, and a conductivity of 210 to 285 µS cm⁻¹. Given its tropical latitude, the water of this lake is generally warm, having a surface temperature that ranges from 24 to 29 degrees celsius (75 to 84 degrees fahrenheit), with a deep water temperature of about 22 celsius (72 °F), year round.

See also

• African Great Lakes
• Lake Malawi National Park
• Rift Valley lakes

References

Further reading

• Mayall, James (December 1973). "The Malawi-Tanzania Boundary Dispute". The Journal of Modern African Studies 11 (4): 611–628. doi:10.1017/S0022278X00008776. 
• Recent study on Lake Malawi water levels reveals drought 100,000 years ago

External links

• Index of Lake Malawi Cichlids