One of South Africa's most popular recreational boating sites, the Hartbeespoort Dam north of Johannesburg, is under siege from an alien weed that has cut off water access for the local yacht and boat clubs and now covers over a third of the dam.

The rapid spread of water hyacinth across the 20 square kilometre dam has been linked to the termination of a government weed-clearing programme. Private property owners are now clearing their own waterways, but are battling to make headway. Local farmers have also been invited to harvest the weed for fertiliser.

“From our shore, it [water hyacinth] stretches about 150 metres in – you can’t move,” Ferdi Botha from the Hartbeespoort Boating Club (HBC) told IBI. “If you had the guts you could run on it.”

Botha said the amount of open water in front of the club now depended on wind direction, which at times pushed the hyacinth towards the dam wall. Meanwhile, the nearby Transvaal Yacht Club is in a far worse position – hemmed in by the weed for weeks at a time, Botha said. “They (TYC) are stuck,” he said, adding that another local boat club had similarly suffocated.

“As a result of this we have lost revenue. In December and last Easter, our club [revenue] went down by about 50%,” Botha said. “We bought a little boat with a mesh scoop in front just to clear our area. If it is a good day we take our boat and push it into the dam.”

Other property owners are using bulldozers with a mechanical hand to try and stem the bloom. “It is a nightmare. Currently government is not doing anything about it.”

A similar hyacinth bloom in the 1970s had been treated with a poisonous crop spray that had damaged other organisms. Property owners were hoping to employ a similar method with a less harmful product, Botha said.