Olifantsnek Dam, Arch dam in Rustenburg, South Africa.

Olifantsnek Dam is a concrete arch dam on the Hex River, about 25 km west of Rustenburg. Its wall stands 30 m high and 129 m long, holding a reservoir of 14.2 million cubic metres that spreads over 272 hectares and reaches some 5 km downstream. The dam was designed by engineer John Gibson as the first arch dam in the area.

The dam was built in 1929 by the Department of Water Affairs to support irrigation for agriculture in the region. This early infrastructure became essential for local development.

The reservoir is stocked with Nile tilapia, African catfish and introduced carp, and waterbirds such as herons, ibises and cormorants live along its banks. Local tourism bodies run half-day tours that include the control room and an explanation of how water is released into the irrigation canals.

The location is open and windy, so visitors should be prepared for changing weather conditions throughout the day. Information signs at the site help explain water levels and access areas.

The dam wall was strengthened in 2004 after surface cracks appeared, and electronic monitoring systems were installed to measure stress. A 4-kilometre walking trail circles the reservoir, passing acacia trees and granite rocks. The reservoir is also stocked with Nile tilapia, African catfish and introduced carp.