Ingula is located in the Little Drakensberg range and straddles the border of the Free State and KwaZulu-Natal provinces .
A 2km long headrace tunnel connects the upper reservoir to the underground power station .
of water . The dams , 4.6km apart , are connected by underground waterways passing through a subterranean powerhouse with four 333MW generators .
Peak demand
The plant uses water from the upper reservoir to generate electricity when there is peak demand during the day . At night , excess power on the grid ,
18 Water Sewage & Effluent January / February 2017