Hyacinth crisis continues
After yet another site visit to the Brakpan Dam, it was noted by the Democratic Alliance that the Ekurhuleni Metropolitan Municipality is not serious about ridding the dam of hyacinth.
Brakpan ward councillor Brandon Pretorius and councillors Jill Humphreys and Tiziana Plaskitt, both members of the environmental oversight committee, conducted a visit to the dam on Friday, last week.
The councillors explained that the ongoing reason for the hyacinth infestation is the continued sewage being released into the waterway.
According to them, the neighbouring water treatment plant is operating well above capacity and is incapable of maintaining an effective operation.
They also believe the current attempts to remove the infestation is largely ineffective.
“The Watermaster is doing its daily scoops while it remains functional, but the flowering hyacinth is way ahead of the game,” said Pretorius.
“Moreover, the removed material has to be eradicated in a way that pre-empts regrowth.
“The seeds and all aspects of the plant that can achieve propagation must be destroyed.”
As one can see from the enormous heaps of removed material around the dam, the hyacinth is re-growing much faster than it is being removed.
The floating plants are also flowering, which redoubles its growth.
Other methods have been considered in dealing with the infestation, including insects and chemical control.
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“The weevil attacks the plant and slows down the growth, however, this method is very slow,” said Pretorius.
“Poison has many side effects; besides affecting all life in the water, the poisoned plants sink to the bottom and mix with the sludge from the sewage.”
The councillors consulted with a hyacinth expert working on the issue at the Hartbeespoort Dam.
“According to him, the Brakpan Dam is about 30 times smaller than Hartbeespoort Dam and without having knowledge of the water quality in the dam etc, he assumed that the hyacinth density is between 200 and 300 ton/ha,” said Pretorius.
“If one assumed 250 ton/ha, then you have about 17500 ton of hyacinth (wet) on the dam.
“Under current climatic conditions growth will be about 50 ton/ha/m.
“This means that each month the mass of hyacinth will grow by 3500 ton.
“If harvesting is done at 3500 ton/m (117 ton/day) the surface will remain 100 per cent covered.”
An aerial image of the dam indicates that it already reached 100 per cent coverage between November 13 and 18, last year.
“So the bottom line is that if the sewage ingress is not contained, the hyacinth will not be removed and will keep on entirely covering the dam,” said Pretorius.
“The Watermaster is too slow to succeed and cannot keep up with the growth, which means the water will become completely oxygen deprived.
“The dam and all life in it will die.”
The councillors have vowed to keep on looking for solutions to the problem, which could include the assistance of local stakeholders and the community.
“We will do everything possible to assure the positive outcome the community of Brakpan expects,” added Pretorius.
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