Lake Victoria

Lake Victoria is one of the African Great Lakes. With a surface area of approximately 59,947 km2 (23,146 sq mi),[6][7] Lake Victoria is Africa’s largest lake by area, the world’s largest tropical lake,[8] and the world’s second-largest fresh water lake by surface area after Lake Superior in North America.[9] In terms of volume, Lake Victoria is the world’s ninth-largest continental lake, containing about 2,424 km3 (1.965×109 acre⋅ft) of water.[7][10] Lake Victoria occupies a shallow depression in Africa. The lake has an average depth of 40 m (130 ft) and a maximum depth of 80–81 m (262–266 ft).[7][10][11] Its catchment area covers 169,858 km2 (65,583 sq mi).[12] The lake has a shoreline of 7,142 km (4,438 mi) when digitized at the 1:25,000 level,[13] with islands constituting 3.7% of this length.[14]

The lake’s area is divided among three countries: Tanzania occupies 49% (33,700 km2 (13,000 sq mi)), Uganda 45% (31,000 km2 (12,000 sq mi)), and Kenya 6% (4,100 km2 (1,600 sq mi)).[15]

The lake is home to many species of fish which live nowhere else, especially cichlids. Invasive fish, such as the Nile perch, have driven many endemic species to extinction.

Geologically, Lake Victoria is relatively young at about 400,000 years old. It was formed when westward-flowing rivers were dammed by an upthrown crustal block.[20] During the Miocene era, what is now the catchment area of the lake was on the western side of an uplifted area that functioned as a continental divide, with streams on the western side flowing into the Congo River basin and streams on the eastern side flowing to the Indian Ocean. As the East African Rift System formed, the eastern wall of the Albertine Rift (or Western Rift) rose, gradually reversing the drainage towards what is now Lake Victoria. The opening of the main East African Rift and the Albertine Rift down warped the area between them as the rift walls rose, creating the current Lake Victoria basin.[21]

During its geological history, Lake Victoria went through changes ranging from its present shallow depression, through to what may have been a series of much smaller lakes.[14] Geological cores taken from its bottom show Lake Victoria has dried up completely at least three times since it formed.[20] These drying cycles are probably related to past ice ages, which were times when precipitation declined globally.[20] Lake Victoria last dried out about 17,300 years ago, and it refilled 14,700 years ago[22] as the African humid period began.[23]