Theewaterskloof Dam, Earth-fill dam near Villiersdorp, South Africa

Theewaterskloof Dam is an earth-fill dam on the Sonderend River near Villiersdorp. Its wall is 646 metres long and 35 metres high, holding back a reservoir that covers 5,059 hectares when full. The dam appears as a broad sheet of grey-green water behind a low earthen embankment with a lighter crest, bordered by scrubland and distant mountains.

Built in 1978 on the Sonderend River near Villiersdorp, the dam holds 480 million cubic metres, about 41% of the storage capacity available to Cape Town. Its Charmaine intake tower feeds the Franschhoek Tunnel under the Franschhoek Mountains into the Berg River catchment; in winter the tunnel runs in reverse, carrying surplus Berg River water back into the reservoir.

The reservoir is the venue for the annual Synergy Live music festival, one of South Africa's largest outdoor music events, usually held on the last weekend of November or the first weekend of December. The name Theewaterskloof combines the Dutch-derived words for tea and water with kloof, Afrikaans for a ravine or gorge.

The dam lies near Villiersdorp on the Sonderend River, reached from the R43. The wall is 646 metres long and 35 metres high, with an inlet tower and conduit releasing water into the river. The reservoir covers 5,059 hectares when full, so the shoreline shifts widely with the level; the catchment above the Hottentots Holland range averages only 69 rain days a year.

During dry periods, dropping water levels reveal tree tops emerging from the surface, creating an unusual landscape across the expansive reservoir. These ghostly remains serve as reminders of the land that was flooded when the dam was filled.