A highly invasive weed now covers the entire Vaalkop Dam. (Photos: Centre for Biological Control)
Hartbeespoort Dam on steroids. That’s how landowners around the Vaalkop Dam in the North West have described the dam’s heavy infestation with the invasive alien aquatic plants, water hyacinth and common salvinia.
These water weeds are now smothering 100% of the Vaalkop Dam — a crucial water source for the Bojanala and Waterberg districts — and it’s become a “desperate situation”, according to Martin Frere, a board member of Bushwillow Estate, on the dam.
This week, the Vaalkop Dam Alien Vegetation Action Group, which comprises Bushwillow Estate, Finfoot Lodge and Mziki Nature Reserve, warned that the structure is at risk of ecological and economic collapse.
Situated about 60km northwest of the polluted Hartbeespoort Dam, Vaalkop is considerably less well-known. Although it is about half the size of Hartbeespoort Dam, it is the primary source of drinking, agricultural, and industrial water for the North West, supplying towns such as Rustenburg, Swartruggens and Thabazimbi, the Sun City resort and the platinum mining belt with potable water.
A major distinction is that Hartbeespoort Dam is primarily used for irrigation downstream, Frere noted. In contrast, Vaalkop Dam has a huge water treatment plant, run by Magalies Water.
“Its capacity is 270 million litres a day so the water used from that dam is predominantly potable water … It’s a really significant water resource for the province. If Magalies Water had to stop abstraction, the consequences would be devastating,” he said.
Despite the dam’s importance, authorities have largely ignored its plight, the Vaalkop Dam Alien Vegetation Action Group said.
The first little islands of water hyacinth, the world’s worst aquatic weed, were first detected in the system in October 2017. The invasion was immediately reported to the then-department of forestry, fisheries and the environment and then to the department of water and sanitation in 2018.
According to the action group, the water and sanitation department “halted a plan to control the invasion chemically”. Despite frequent attempts by local stakeholders to address why this was the case, their queries and communications were “largely ignored”.
The water quality of the Vaalkop Dam has been compromised by poorly treated wastewater from local municipalities, as well as by water fed directly into the dam through the Crocodile River downstream of Hartbeespoort Dam, “arguably South Africa’s most polluted system”.
Frere said two natural rivers feed into Vaalkop Dam: the Elands River and the Hex River. The Hex River emanates from the Bospoort Dam in Rustenburg, which is “renowned for bad water quality” because of the dysfunctional Rustenburg wastewater treatment plant.
The other inlet into Vaalkop Dam is a canal from the Roodekoppies Dam, which is fed by the sewage-polluted Hartbeespoort Dam.
“About 70% of the water in Vaalkop comes from that canal so it’s really obvious that that is the source of the really bad nutrient situation in Vaalkop Dam. Water hyacinth just loves bad water; it feeds and multiplies at phenomenal rates,” he said.
The weed flowers and produces prolific numbers of seeds that can remain viable for about 25 years.
In 2020, affected people contacted the Centre for Biological Control (CBC) at Rhodes University to introduce a biological control agent, the tiny water hyacinth hoppers, to the dam and to establish rearing facilities, in a similar manner to what was implemented at Hartbeespoort Dam. This was to manage and reduce the spread of the water hyacinth.
While these biocontrol agents — natural enemies of the water hyacinth — were released and although three rearing stations were established, there simply weren’t enough stakeholders around the dam to set up enough to supplement what the centre sent.
“We’ve been dosing the dam for four years but we just haven’t been able to hit the same infestation of insects on Vaalkop as was witnessed on Harties,” Frere said. “Harties had 2 500 bugs per square metre; we’ve only managed to get it up to 700. It’s just from a lack of resources.”
In June last year, the CBC surveyed dams and rivers in the North West and highlighted that a new invader, common salvinia, was spreading down the Crocodile River from Hartbeespoort Dam, as well as down the Hex River from another invaded site, the sewage-polluted Bospoort Dam.
Officials were made aware of the severity of the invasion, which had also reached the Limpopo River that forms the national border with Botswana.
In January, Vaalkop Dam’s water level stood at a very low 25% but by April, following the late summer rains, it was overflowing. This increase in water, rich in nutrients, allowed both water hyacinth and common salvinia to explode. The amount of aquatic weeds on the system soared from about 100 hectares in January to 1 000 hectares at the end of May.
The mat is a mixed carpet of water hyacinth and common salvinia, which blocks out light, preventing oxygen from being produced in the water column. This causes most of the aquatic life in the system to die, turning the dam, which is a birding, fishing and wildlife hotspot, into a “largely lifeless” body of water.
“We have now found that [common salvinia] in a whole lot of North West systems and one of them is Vaalkop,” said research scientist Julie Coetzee, the deputy director of the CBC. “It probably came in either from the Harties water or upstream from Bospoort Dam.”
Both Bospoort and Vaalkop are between 95% and 100% covered in a mixture of water hyacinth and salvinia. “It looks like a golf course or a mealie field,” she said. “It’s insane.”
Additionally, water quality is compromised, necessitating increased and additional treatment by Magalies Water, the region’s bulk water supplier.
The Vaalkop Dam Alien Vegetation Action Group is fearful that the amount of organic matter on the dam’s surface will drastically increase the total organic carbon in the water.
“The direct result is that Magalies Water will doubtless need to increase its chlorination dosing, which in turn will result in creating increased chlorine disinfection by-products, such as carcinogenic trihalomethanes,” it said.
Last year, Magalies Water increased its chlorine dosing levels, thereby creating trihalomethanes. “This year, the TOC challenge will be much higher.”
Coetzee added: “What they’ve been doing is adding chlorine and there’s only a certain amount of chlorine you can add to water that is meant to be for drinking. Soon, we’re not going to be able to do anything with it [Vaalkop’s water].
“We’re now trying to get Sun International aware of this huge threat that if Magalies Water can’t treat the water any longer because of all these weeds, they are not going to be receiving drinking water.”
The plant invasion must be addressed urgently, the action group said. It has had numerous meetings regarding both the poor water quality and the water weed invasion. “However, these meetings are often not attended by the relevant officials despite invitations extended to them,” Coetzee said.
A high-level meeting was held on 24 May at Bushwillow Estate, where the department of water and sanitation, Magalies Water, the CBC and local people committed to working towards an integrated management plan for the system, which will requires extensive funding.
The Vaalkop action group noted that in the absence of implementing a management plan, the region risks losing access to potable water, as well as the deterioration of aquatic biodiversity, which supports a premier wildlife haven for the province.
Pelham Jones, of the Mziki Nature Reserve, warned that a conservation crisis was unfolding. “This is a very rich natural area. We have everything from the Cape clawless otter, a very nice population of fish eagles and so many aquatic birds, mammals, and so on and they, in turn, are obviously being negatively affected.
“I don’t know what this surface cover will do to the fish population but clearly it will be very detrimental for all of the obvious reasons.”
The North West Parks and Tourism Board and Magalies Water had not responded to the Mail & Guardian’s inquiries by the time of publication.
Wisane Mavasa, spokesperson for the water department, said the Vaalkop Dam receives water from Hartbeespoort Dam through a canal and is downstream of Bospoort Dam.
“All three dams have alien invasive plants. It is suspected that the plants from Bospoort migrated downstream to Vaalkop,” she said.
The department, through its implementing agent, Magalies Water and the CBC, is working on Hartbeespoort Dam’s infestation and upstream to improve the water quality in the dam.
“Communities around Hartbeespoort Dam also assist in rearing biological controls under the supervision and guidance of the centre. Community members around Vaalkop have initiated similar rearing stations,” said Mavasa.
She cited the community meeting on 24 May with Magalies Water and the department, where it was resolved that an integrated plan needs to be developed to address the water quality and infestation on the dams.
“This will also include upstream wastewater works from Rustenburg that are leading to a reduction in water quality,” she said, noting that the draft plan will be tabled to the deputy minister, Sello Seitlholo, within the coming weeks for consideration and discussion with the relevant role players including the water services authorities.
Jones, however, was sceptical. “If, at the time, the department had reacted with proactive interventions, the problem could have been not resolved, but managed at a fraction of the price it’s going to now cost to resolve this. It’s just unfortunately too little, too late.”
David Magae, the spokesperson for Magalies Water, said it concerns centre “more on the difficulties associated with treating the heavily-laden water with organics coupled with increased costs.
“Water being produced by Vaalkop Waterworks still complies with national quality standards for drinking water and continues to do so as Magalies Water has skills and experienced workforce … Treatment costs have increased drastically as Magalies Water is using more chemicals including chlorine.
The way forward is to trace the source of pollutants “entering our water sources and eliminate them”, he added.