evidence: The Lake Victoria basin is part of a plateau rising eastward from the lakeshore to the Rift highlands. The lower part, forming the lake basin proper, is itself a plateau area lying between 3,000 and 4,000 feet (900 and 1,200 metres) above sea level. The rolling grassland of this plateau is cut almost in half by the Kano Plain, into which an arm of the lake known as Winam Gulf (Kavirondo Gulf) extends eastward for 50 miles (80 km). The floor of the Kano Plain merges north and south into highlands characterized by a number of extinct volcanoes. These include Mount Elgon, rising to 14,178 feet (4,321 metres) at the Ugandan border on the extreme north of the basin. [...] There are no major groundwater basins, and, apart from the Tana River, most of the rivers in Kenya are short and often disappear during the dry season. Lake Victoria, with a surface area of 26,828 square miles (69,484 square km), is the largest lake in Africa, the second largest freshwater body in the world, and a major reservoir of the Nile River. Lake Rudolf, some 150 miles (240 km) long and 20 miles (30 km) wide, is the largest of the country’s Rift Valley lakes. Other lakes are rather small, and their surface areas fluctuate considerably.