Africa’s deepest lake is also Earth’s longest freshwater trench
Lake Tanganyika ranks second only to Baikal in freshwater volume and depth, yet stretches farther than any other freshwater lake. Shared by Tanzania, the Democratic Republic of the Congo, Burundi, and Zambia, it holds about sixteen percent of the planet’s available surface fresh water.
Set in the Albertine Rift’s mountain walls, it is Africa’s largest rift lake and deepest basin. Three basins formed at different times—the centre 9–12 million years ago, the north 7–8, the south 2–4—making Tanganyika one of roughly twenty lakes older than a million years. Catchment covers 231,000 square kilometres; the Lukuga is the sole major outlet toward the Congo, though precipitation and evaporation dominate the budget and at least ninety percent of inflow arrives as rain.
The Ruzizi, only about 10,000 years old, enters from Lake Kivu; Tanzania’s Malagarasi arrives from the east and once likely headed for the Lualaba before the rift lake rose. Practically endorheic for long stretches of its history, the lake’s sea connection depends on high water. Over its long life it has seldom drained to the ocean at all, and researchers have proposed that at various times it received water from a higher Lake Rukwa, connected with Lake Malawi, or even spilled toward the Nile. Surface temperatures swing from about 24 °C in southern August to 28–29 °C in late rains, while water below 400 metres stays near 23 °C. Seasonal mixing rarely reaches below 150 metres, driven mostly by wind-powered upwelling in the south, so the deep water stays sealed off.
Since the 1990s levels have risen roughly two metres, flooding places such as Nsumbu, Zambia. Alkaline chemistry near pH 9 in the upper hundred metres still hosts endemic cichlid radiations. At least 250 endemic cichlids live here, about 98 percent of its cichlid species found nowhere else, and although Malawi and Victoria hold more species, Tanganyika’s are the most varied in body form and genetics. Most keep to the top 100 metres, but Trematocara species have been caught below 300, deeper than any other cichlid known.
Nile crocodiles, among them the famously huge Gustave, patrol its wetlands alongside several kinds of hinged terrapin.
Source: Lake Tanganyika
