Oviston is a little town, 10 km from Venterstad, on the southern bank of the Gariep Dam. It was established in 1965 to accommodate workers on the Orange-Fish River Tunnel project. The name is derived from the Afrikaans Oranje-Vis-tonnel, ‘Orange-Fish Tunnel, that is situated nearby.

The construction of the Orange-Fish Tunnel made the irrigation of thousands of hectares of additional land in the Eastern Cape possible, diverting water from the Orange River to the Great Fish River.

The Orange-Fish Tunnel is an engineering marvel. The inlet is located at Oviston and under a distinctive flat-topped hill called Teebus, between the small towns of Steynsburg and Hofmeyr, is the outlet end of the world’s third-longest continuous aqueduct. Opened in 1976, the Orange-Fish Tunnel remains one of South Africa’s most outstanding engineering feats, critical for millions of people in the Eastern Cape.

For more than 11 months of the year, an average of 22 cubic metres of water per second from the Gariep Dam thunder through this 82.45km underwater aqueduct under the Suurberg Mountains, supplying the towns of Cradock, Cookhouse, Somerset East, Kirkwood, Steynsburg, Addo, Adelaide, Bedford and the cities of Grahamstown and Port Elizabeth. The water irrigates crops and dairies in the fertile Karoo Heartland as well as the multi-million-rand Sundays River Citrus orchards around Addo and Kirkwood.

The Orange-Fish Tunnel becomes a fleeting tourism attraction in midwinter, when the massive cloverleaf intake roller-valves at Gariep Dam are closed. The constant roar of the water quiets to a trickle while a maintenance team from the Department of Water and Sanitation (DWS) comes in.

Dressed in overalls, gumboots and head torches, they splash through this odd world, with the occasional dead or live fish or crab brushing past their ankles in the deeper tunnels as they caulk tunnel linings, fix holes and replace the worn linings of the pepperpot valves specially designed to control the flow of the water. During these few weeks, visitors (usually curious irrigation farmers and friends) are allowed to see this exceptional place from the inside, as long as there is someone available to guide them around.

Source – Karoo Space
Read more about the tunnel – https://karoospace.co.za/the-orange-fish-tunnel/