the "great grey-green, greasy Limpopo River, all set about with fever-trees," where the "Bi-Coloured Python Rock-Snake" dwells in the Just So Stories is apt. Rainfall is seasonal and unreliable: in dry years, the upper parts of the river flow for 40 days or less. The upper part of the drainage basin, in the Kalahari Desert, is arid but conditions become less arid further downriver. The next reaches drain the Waterberg Massif, a biome of semi-deciduous forest and low-density human population. The fertile lowlands support a denser population, and about 14 million people live in the Limpopo basin. Flooding during the rainy season is an occasional problem in the lower reaches. During February 2000 heavy rainfalls during the passage of a cyclone caused the catastrophic 2000 Mozambique flood. The highest concentration of hippopotamus in the Limpopo River is found between the Mokolo and the Mogalakwena Rivers. There is a lot of mining activity in the Limpopo River basin with about 1,900 functioning mines, not counting about 1,700 abandoned mines. History Vasco da Gama, on his first expedition, was probably among the first Europeans to sight the river, when he anchored off the mouth in 1498. However, there has been human habitation in the region since time immemorial—sites in the Makapans Valley near Mokopane contain Australopithecus fossils from 3.5 million years ago. St Vincent Whitshed Erskine, later surveyor general for South Africa, traveled to the mouth of the river in 1868–69. A Zambezi shark was caught hundreds of kilometres upriver at the confluence of the Limpopo and Luvuvhu Rivers in July 1950. Zambezi sharks tolerate fresh water and can travel far up the Limpopo. In 2013, approximately 15,000 Nile crocodiles were accidentally released into the river from flood gates at the nearby Rakwena Crocodile Farm. Gallery See also Limpopo border gates Great Limpopo Transfrontier Park List of international border rivers Drainage basin A References External links Climate change implications for water resources in the Limpopo River Basin, study by IFPRI Green and blue water accounting in the Limpopo and Nile Basins, study by IFPRI Limpopo Watercourse Commission (LIMCOM) www.limcom.org Limpopo River Awareness Kit FROC - Reference frequency of occurrence of fish species in South Africa Rivers of Botswana Rivers of Zimbabwe International rivers of Africa Rivers of Mozambique Mozambique Channel Border rivers Botswana–South Africa border South Africa–Zimbabwe border Rivers of North West (South African province) Rivers of Limpopo