Африканың ұлы көлдері: Малави көлі

African Great Lake

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.

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.

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.

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.

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. Both sides cite the Heligoland Treaty of 1890 between Great Britain 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.

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 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.

Lake Malawi is home to 28 species of freshwater snails (including 16 endemics) and 9 bivalves (2 endemics, Aspatharia subreniformis and the unionid Nyassunio nyassaensis). The endemic freshwater snails are all members of the genera Bellamya, Bulinus, Gabbiella, Lanistes and Melanoides. Lake Malawi is home to a total of four snail species in the genus Bulinus, which is a known intermediate host of bilharzia. A survey in Monkey Bay in 1964 found two endemic species of snails of the genus (B. nyassanus and B. succinoides) in the lake, and two non endemic species (B. globosus and B. forskalli) in lagoons separated from it. The latter species are known intermediate hosts 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. More recently, the disease has become a problem in the lake itself as the endemic B. nyassanus has become an intermediate host. This change, first noticed in the mid 1980s, is possibly related to a decline in snail eating cichlids (for example, Trematocranus placodon) due to overfishing and/or a new strain of the bilharzia parasite. The atyid shrimp Caridina malawensis is endemic to the lake, but it is poorly known and has historically been confused with C. nilotica, which is not found in the lake. Pelagic zooplanktonic species include two cladocerans (Diaphanosoma excisum and Bosmina longirostris), three copepods (Tropodiaptomus cunningtoni, Thermocyclops neglectus and Mesocyclops aequatorialis), and several ostracods (including both described and undescribed species).

Lake Malawi is famous for the huge swarms of tiny, harmless lake flies, Chaoborus edulis. These swarms, typically appearing far out over water, can be mistaken for plumes of smoke and were also noticed by David Livingstone when he visited the lake. The aquatic larvae feed on zooplankton, spending the day at the bottom and the night in the upper water levels. They lay their eggs at the water's surface and the adults die. and the adult flies are important both to birds and local people, who collect them to make kungu cakes/burgers, a local delicacy with a very high protein content.