Luangwa River ago, there was no way out and the Luangwa Rift filled with a Rift Valley Lake called the Madumabisa Lake, which rivalled Lake Malawi in size. The water of the lake overflowed in a river to the south-west, towards what is now the Kalahari, where it combined with the Okavango, Upper Zambezi, Cuando and Kafue rivers, emptying into the Limpopo River and flowing to the Indian Ocean. Several geological events combined to produce the current river systems. Faulting produced another graben just to the south of the Luangwa Rift, and running east-west: the Zambezi Rift Valley and the Chicoa Trough.
Shashe River Shashe is a sand filled channel, with extensive alluvial aquifers in the river channel and below the alluvial plains. These supply water for a number of irrigation schemes including Sibasa and Shashi. More than two million years ago, the Upper Zambezi River used to flow south through what is now the Makgadikgadi Pan (presently a vast seasonal wetland) to the Shashe River and thence the Limpopo River. There is a road bridge and a rail bridge south of Francistown. The lower Shashe River forms the border between Botswana and Zimbabwe and is unbridged. However, at Tuli, both sides of the