Ensuring that this does not happen falls to the Gamtoos Irrigation Board which is responsible for the management of alien vegetation in the Swartkops River system, among other provincial projects funded by the Department of Environmental Affairs.
According to area manager Andrew Knipe, the battle for the Swartkops has been raging for the last few years, and steady progress is being made, as teams of workers clear and maintain the river and floodplain. Since 2011, the project has cleared more than 765 hectares, with follow-up work completed on over 2,672 hectares.
“Water hyacinths, in particular, need repeated follow-ups and will re-establish very quickly if we stop clearing operations,” said Knipe, adding that the population in the lower reaches of the Swartkops River was the lowest it had been in years.
“However, the problem is compounded by industrial and agricultural pollutants entering the river.”
This, Knipe warns, is not a problem that is going to go away any time soon, with pollution levels escalating.
“One of the problems is that the capacity of the Kelvin Jones water treatment works is too small to cope with the vast amounts of sewage being fed into it, so sewage is released into the river,” Knipe said, explaining that when pollution levels are high, the water hyacinth population explodes, doubling every 14 days.
If the water hyacinths get out of control they can cover the entire river, absorbing all the oxygen from the water, killing fish and plant life.
The solution, in part, lies in clearing the river of these aquatic weeds, as well as the surrounding land of alien vegetation, including eucalyptus (bluegum), acacia saligna (Port Jackson willow) and sesbania.
Keeping control of this mammoth task is project manager James Jansen, who works with an annual budget of R1.5-million and oversees three teams of 12 members each.
“One of the major challenges is that we’re treating the symptoms not the cause,” said Jansen.
He said clearing alien vegetation from the river banks exposed the river to more sunlight, allowing for the faster breakdown of nutrients.
“It also increases the run-off, which means that more water gets into the rivers.
“In terms of the water hyacinth itself, there were stretches where the river was completely covered and we have managed to clear big patches,” said Jansen.
“This is vitally important as communities living close to the banks use the water directly. Also, Swartkops has been declared a national marine estuary, so it’s a critical part of the ecosystem for fish breeding.”
Educating the public about the environmental dangers posed by invasive alien plants remains an important aspect of the work that lies ahead, said Knipe.
“We have the support of many land owners along the Swartkops River. With their assistance, we have been able to clear long stretches of river from Uitenhage,” he said.
“Fantastic work is also being done in the surrounding catchments of Sand/Bulk River and Van Stadens.
“The road ahead is a difficult one and, even though a lot of resources have been dedicated to the fight, more needs to be done if we are to rid our country of this scourge.”