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Lake Tanganyika: The Second Deepest Lake in the World
Lake Tanganyika Information and Facts
Lake Tanganyika is one of the African Great Lakes. With a depth of 1,470 meters (4,820 feet), it is the second deepest lake in the world, after Lake Baikal. It’s also the world’s second largest freshwater lake by volume. Lake Tanganyika is 673 kilometers (418 miles) long, which makes it the world’s longest lake.
The lake is located in 4 countries: Tanzania, Democratic Republic of the Congo, Burundi and Zambia, between 3 and 9 degrees South. Tanzania (46%) and the Democratic Republic of the Congo (40%) have the biggest shares of the lake. Zambia and Burundi each have 7% of the lake.
Lake Tanganyika is one of the 20 ancient lakes on Earth, and its age is estimated to be somewhere between 9 to 12 million years old.
Geography and Hydrography
Lake Tanganyika is located in the Albertine Rift, which is the western section of the East African Rift. It’s the second largest lake in Africa by surface area (after Lake Victoria), the largest lake in Africa by volume, and its maximum depth of 1,470 meters (4,820 feet) makes it the deepest lake in Africa, reaching 642 meters (2,106 feet) below sea level. Holding 18,900 cubic kilometers (4,500 cubic miles) of freshwater, it accounts for approximately 18% of all the world’s unfrozen surface freshwater.
With a length of 673 kilometers (418 miles) it is the world’s longest lake, and it stretches in a North-South direction. It averages around 50 kilometers (31 miles) in width, with a maximum of 72 kilometers (45 miles). The lake’s surface area of 32,900 square kilometers (or 12,700 square miles) makes it the fifth largest freshwater lake in the world in that aspect. It has a shoreline of 1,828 kilometers and an average depth of 570 meters (1,870 feet). Its maximum depth of 1,470 meters is reached in the northern section of the lake. The lake’s average surface water temperature is 25° C and the average pH is 8.4.
The 3 Main Basins
Lake Tanganyika has 3 basins. The Kigoma basin in the North reaches a depth of 1,310 meters. It is separated by the middle basin by a broad sill that reaches a depth of 655 meters. The middle basin is separated by the Kipili basin in the South by another sill 700 meters in depth. Kipili, the southern basin is the deepest, and the lake reaches its maximum depth of 1,470 meters here.
Because the lake is extremely deep and located in a tropical area, the bottom of the lake contains "fossil water" which lacks oxygen. This water may be up to 20 million years old. The lake is also known for its ferocious storms which generate 6-meter (20-foot) waves. Despite these storms, mixing between surface and bottom waters doesn’t occur, which makes the lake meromictic. Water temperatures in Lake Tanganyika are amazingly uniform, with the lower regions a mere 3° C colder than at the surface. The reason for this is unknown. The surface layer undergoes annual seasonal temperature change. The lake’s average transparency is 11 meters (36 feet). The lake’s proximity to the equator means that the solar radiation around it varies very little throughout the year. Nutrients that are supplied to the mixed layer, where photosynthesis occurs, are mostly internal from the lake itself. Atmospheric and riverine nutrient inputs are considered negligible.
Lake Tanganyika has a catchment area of 231,000 square kilometers (89,000 square miles). Four protected areas are located at the lake’s shores: Gombe Stream National Park and Mahale Mountains National Park in Tanzania, Rusizi Natural Reserve in Burundi (which is also a Ramsar Site), Gombe Stream National Park, and Nsumbu National Park in Zambia
Inflows and Outflow
The most important rivers that flow into the lake are the Malagarasi River (475 kilometers or 295 miles), the Ruzizi River (117 kilometers or 73 miles in length), and the Kalambo River. The Ruzizi River was formed about 10,000 years ago, and it enters the lake in its northern section, flowing in from Lake Kivu. The Malagarasi River is Tanzania’s second largest river and it enters the lake on its eastern shore. Because the Malagarasi River is actually older than Lake Tanganyika, it used to flow into the Congo River before the lake was formed. The Kalambo River has the second highest waterfall in Africa, the Kalambo Falls (215 meters or 704 feet high). There are many other smaller rivers and streams flowing into Lake Tanganyika, but their size is limited by the steep mountains in the lake’s basin.
The lake has only one outflow, the Lukuga River (320 kilometers or 200 miles in length). It’s ultimately drained into the Atlantic Ocean via the Lualaba River (Congo River’s largest tributary by volume), and the Congo River.
Lake Tanganyika has had many changes in its flow patterns since its formation. There are several major factors contributing to this, such as the lake’s great depth, its high altitude, and mountainous and volcanic area. It seems that it rarely had an outflow into the sea in the past, so it’s considered endorheic by many. Lake Tanganyika’s connection to the sea is dependent on high water levels.
The lake’s high rate of evaporation also makes it dependent on high inflow from Lake Kivu via the Ruzizi river, so that it can stay high enough to overflow. Also, it’s thought that the surface of Lake Tanganyika may have been at times 300 meters lower than it is today, which means that it didn’t flow into the sea.
The annual cycle in the region consists of 2 main seasons. The wet season is between October and April and is characterized by high humidity, considerable precipitation, weak winds over the lake, but also frequent thunderstorms.
The dry season lasts from May until the end of August, and is characterized by strong, southerly winds and little precipitation. These seasonal changes are the results of large-scale atmospheric processes.
Flora and Fauna
Lake Tanganyika and its shores boast an exceptional diversity of plants and animals. It’s estimated that the lake is home to more than 2,000 animal and plant species, out of which 600 are endemic.
The lake is home to 250 cichlid fish species, out of which 98% are endemic to the lake. It’s also home to 75 non-cichlid fish species, out of which approximately 60% are endemic. Most fish live along the lake’s shoreline, to a maximum depth of about 180 meters (590 feet).
However, the lake’s largest biomass of fish lives in the open waters, and it’s comprised out of 6 important species: 4 species of predatory Lates and 2 species of sardines. The incredible diversity of fish in the lake makes it important resources for the study of speciation in evolution.
The bright colors of the cichlids in Lake Tanganyika make them very popular among aquarium owners.
Lake Tanganyika is also home to a great number of invertebrates.
There are 68 snail species in the lake, out of which 45 are endemic. Additionally, there are 15 bivalve species, out of which 8 are endemic. The snails are atypical for freshwater, with features like thickened shells or distinct sculpture, which make them more similar to marine snails, even though they are unrelated to latter. This is also the main reason why they are referred to as thallasoids, which means "marine-like". All the thallasoids in Lake Tanganyika are endemic to the lake.
Tanganyicia, Spekia, Lavigeria, Reymondia and Tiphobia are among the 17 freshwater snail genera endemic to the lake. Additionally, 30 species of non-thallasoid snails live in the lake, among which 5 are endemic.
More than 200 species of crustaceans live in Lake Tanganyika, out of which more than 50% are endemic. There are 10 species of crabs, all endemic, 11 species of small atyid shrimp, and several copepods. The great diversity of crustaceans in Lake Tanganyika makes it the richest in that aspect among all other rift valley lakes.
Other invertebrates in the lake include 28 annelids species (17 endemic), 20 nematodes species (7 endemic), 20 species of leeches (12 endemic), 11 flatworm species (7 endemic), 9 sponge species (7 endemic), 6 bryozoa species (2 endemic), as well as a small hydrozoan jellyfish.
Crocodiles can be found on almost the entire shoreline, except in the area around Mpulungu.
Invasive Plant Species
Lake Tanganyika is affected by a number of invasive plant species. The water hyacinth is becoming invasive on the lake’s swampy shores, wetlands, and some parts of the lake. Other invasive plant species include the Nile cabbage, the red water fern, duckweed, the water fern, hydrilla, hornwort, pondweed, filamentous algae and phytoplankton, various plants of the mimosoidea sub-family, Uganda grass, lantana, castor oil plant, candle bush, sicklepod, coffee senna, hairy senna, lead tree, guava, Mauritius thorn, black wattle, Mexican sunflower, toon tree, blackwood cassia, common reed, paper reed, bulrush, pith tree, and the hippo grass.
The 1 million people living around the lake are greatly dependent on the lake fish for protein. Fisheries operate from around 800 sites, with an estimated 100,000 people involved in their activities.
Fish from Lake Tanganyika is exported throughout the entire East Africa. The middle of the 1950s marked the beginning of commercial fishing on the lake, which had a great impact on pelagic fish species. The total catch in 1995 was around 196,570 tons. However, the industrial fisheries which boomed in the 1980s ultimately collapsed.
There are 3 important types of fisheries in the lake: artisanal lift nets, industrial purse seines, and traditional methods like gillnets, scoop nets, and hook and line.
The lake is also an important trade route between riparian countries. The forests around the lake are used as firewood, charcoal, and many other non-timber products.
Action must be taken in order to preserve the beauty of the lake, and its role as a source of life. Overfishing, combined with the use of destructive fishing gears, threaten to deplete the fish stocks in the lake. Industrial pollution is also increasing, as breweries, abattoirs, battery manufacturers in Burundi’s capital and other smaller cities from around the lake, release their waste directly into the water.
Other immediate causes of concerns include unsustainable agricultural practices and deforestation, invasive species, and the effects of the global climate change.
There are 2 ferries which carry passengers and cargo: MV Mwongozo, which goes from Kigoma to Bujumbura, and MV Liemba, which goes from Kigoma to Mpulungu. Tragedy struck the lake on December 12th, 2014, when the ferry MV Mutambala sank, and more than 120 lives were lost.
The British explorers Richard Burton and John Speke were the first westerners to reach the lake, in 1858, while trying to locate the source of the Nile. David Livingstone also passed by the lake later on, and named the southern part of the lake "Liemba", which is thought to be a word from the Fipa language.
During World War I, there were 2 important battles fought on the lake.
In the war’s early stages, the Germans had complete control of the lake, using it to transport troops and cargo across the lake, which was used as a base from which surprise attacks were launched on the Allied troops.
The Allied forces needed to gain control of the lake, so they brought two armed boats from England, transporting them by rail, road, and river to Albertville (currently Kalemie), on the lake’s western shore. The boats were used to capture the German boat Kingami, and sink the Hedwig, which greatly strengthened the Allies’ position on the lake.
In 1965, the Argentinian revolutionary Che Guevara used Lake Tanganyika’s western shores as training grounds for guerilla forces in the Congo, but pulled out in less than a year.
More recently in 1992, Lake Tanganyika was featured in Pole to Pole, a documentary series by the BBC, in which Michael Palin crossed the lake aboard the MV Liemba.