Lake Tanganyika is a large African lake. It is the second oldest freshwater lake in the world, the second largest by volume, and the second deepest lake in all cases after Lake Baikal in Siberia. [5][6] It is the longest freshwater lake in the world, and the lake is shared by four countries which are Tanzania, Democratic Republic of Congo, Burundi and Zambia, Tanzania (46%) and Democratic Republic of Congo (40%) occupying the majority of the lake area. It drains into the Congo River system and eventually into the Atlantic Ocean.
Geography and geological history
Lake Tanganyika lies within the Albertine Fault, the western branch of the East African Rift, and is confined to mountain valley walls. It is the largest rift lake in Africa and the second largest by volume in the world. It is the deepest lake in Africa and contains the largest amount of fresh water, accounting for 16% of the fresh water available in the world. It extends for 676 km (420 mi) in a general north-south direction and is 50 km (31 mi) wide. The lake covers 32,900 square kilometers (12,700 sq mi), with a coastline of 1,828 kilometers (1,136 mi), an average depth of 570 meters (1,870 ft) and a maximum depth of 1,471 meters (4,826 ft) (in the northern basin). It has an area of 18,900 square kilometers (4,500 cubic metres).
The lake’s catchment area is 231,000 square kilometers (89,000 sq mi). Two major rivers flow into the lake, as well as many small rivers and streams (their lengths are limited by the steep mountains around the lake). The only major flow is the Lukuga River, which drains into the Congo River. Precipitation and evaporation play a larger role than rivers. At least 90% of the water flow comes from precipitation at the surface of the lake and at least 90% of the water loss is from direct evaporation.
The main river that flows into the lake is the Ruzizi River, which was formed about 10,000 years ago, and which enters the north of the lake from Lake Kivu. The Malagarasi River, the second largest river in Tanzania, enters the eastern side of Lake Tanganyika. Malagarasi is older than Lake Tanganyika, and before the lake formed, it may have been the source of the Lualaba River, the main source of the Congo River.
The lake has a complex history of changing flow patterns, due to its high elevation, great depth, slow refill rate, and mountainous location in a volatile volcanic region that has undergone climatic changes. Apparently, it rarely flowed into the sea in the past. It has been described as “practically inward” for this reason. The connection of the lake with the sea depends on the rise in the water level which allows the water to flow out of the lake via the Lukuga River into the Congo. When not overflowing, the lake’s exit into the Lukuga River is usually blocked by sand bars and clumps of weeds, and this river instead relies on its own tributaries, particularly the Niemba River, to maintain the flow.
Due to the tropical location of the lake, it has a high rate of evaporation. Thus, it depends on the large flow through the Ruzizi from Lake Kivu to keep the lake high enough to flood. This flow appears to be no more than 12,000 years old, and was caused by lava flows blocking and diverting the previous flow of the Kivu Basin into Lake Edward and then the Nile system and diverting it to Lake Tanganyika. Ancient beach marks indicate that Tanganyika may have been at times 300 meters (980 ft) lower than its present level, with no outlet to the sea. Even its current outlet is intermittent, and thus may not have been operational when first visited by Western explorers in 1858.