It is the fifth largest fresh water 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, including at least 700 species of cichlids. 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 (relating to oxygen in the water) are maintained by moderately small chemical and thermal gradients.
Lake Malawi Geography
Lake Malawi is between 560 kilometres (350 mi) and 580 kilometres (360 mi) long, and about 75 kilometres (47 mi) wide at its widest point. The lake has a total surface area of about 29,600 square kilometres (11,400 sq mi). The lake is 706 m (2,316 ft) at its deepest point, located in a major depression in the north-central part. Another smaller depression in the far north reaches a depth of 528 m (1,732 ft). The southern half of the lake is shallower; less than 400 m (1,300 ft) in the south-central part and less than 200 m (660 ft) in the far south. The lake has shorelines on western Mozambique, eastern Malawi, and southern Tanzania. The largest river flowing into it is the Ruhuhu River, and there is an outlet at its southern end, the Shire River, a tributary that flows into the very large Zambezi River in Mozambique. 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 350 kilometres (220 mi) southeast of Lake Tanganyika, another of the great lakes of the East African Rift.
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 600 m (2,000 ft) below current level to 10–20 m (33–66 ft) above. During periods the lake dried out almost completely, leaving only one or two relatively small, highly alkaline and saline lakes in what currently are Malawi’s deepest parts. A water chemistry resembling the current conditions only appeared about 60,000 years ago. Major low-water periods are estimated to have occurred about 1.6 to 1.0–0.57 million years ago (where it might have dried out completely), 420,000 to 250,000–110,000 years ago, about 25,000 years ago and 18,000–10,700 years ago. During the peak of the low-water period between 1390 and 1860 AD, it may have been 120–150 m (390–490 ft) below current water levels.
The 25 km solo swim across Lake Malawi between Cape Ngomba and Senga Bay has been accomplished on 5 occasions by 16 swimmers
1992: Lewis Pugh 9hrs 52 minutes (UK/SA) and Otto Thanning (SA) 10hrs 5 minutes
2010: Abigail Brown (UK) 9hrs 45 minutes
2013: Milko van Gool (Netherlands) 8hrs 46 minutes and Kaitlin Harthoorn (US) 9hrs 17 minutes
2016: (current record) Jean Craven (SA), Robert Dunford (Kenya), Michiel Le Roux (SA), Samantha Whelpton (SA), Greig Bannatyne (SA), Haydn Von Maltitz (SA), Douglas Livingstone-Blevins (SA) 7hrs 53 mins
2019: Chris Stapley (Eswatini) and Jay Azran (SA) 8hrs 40 minutes, Andrew Stevens (Australia) 10hrs 50 minutes, and Ruth Azran (SA) 11hrs 8 minutes.
In 2019, Martin Hobbs (SA), became the first person to swim the full length of Lake Malawi (54 days), as well as setting the world record for longest solo swim in a lake