Vaal Dam. Image: Department of Water and Sanitation
Despite recent improvements in the Vaal Dam’s water levels, a water expert warns that South Africans should continue to implement water conservation practices.
According to the Department of Water and Sanitation (DWS), the Vaal Dam sat at 24.3% on Monday before two sluice gates were opened at the Grootdraai Dam flowing into the Vaal.
On Wednesday, The Citizen’s sister paper Parys Gazette reported the Vaal Dam sat at 25.5% of capacity. This is an increase of 1.26 percentage points.
If the current net inflow of 1 054 cubic metres per second is sustained it could take 22.6 days to fill the Vaal Dam.
However, Water expert Carin Bosman warns against overly optimistic predictions about the dam’s recovery.
“Nobody can predict whether the Vaal Dam will be full at the end of January. It depends on both the inflows, which in turn depends on the amount of rain that we receive and the runoff that reaches the river upstream from the Vaal Dam, and the levels of consumption,” she told The Citizen.
The dam level rose to 27.62% following recent rainfall, with reports from the dam on Friday putting the level at 30.3% on Friday.
The department emphasised said this increase was not surprising.
“Significant rainfall has been recorded in the last 7 days within the catchment, and if the weather patterns persist, increased surface water levels are expected into the catchment resulting in inflows into the dam filling.
“The current filling of Vaal Dam, on average 2% of its full supply capacity per day during the rainy season, is not unusual.”
It said the current inflow was slightly less than it would have been had the Lesotho Highlands Water Project Tunnel not been closed for ongoing maintenance until the end of March.
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The Vaal Dam’s recent recovery comes after a concerning period of decline.
“The Vaal Dam had been declining by 1.5 weekly until around mid-December,” the DWS explained.
“This is primarily due to climatic factors including low inflows owing to lack of rainfall in the Vaal catchment and elevated temperatures (heat waves) which have led to increased evaporation losses.”
The department noted that the Vaal Dam’s structure makes it particularly vulnerable to evaporation.
“The Vaal Dam is one of the 3 largest dams in the country and its surface area is wide and shallow and is therefore susceptible to high evaporation losses.”
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Bosman says while the increase in the dam’s levels is an improvement, the recent rainfall might not be sufficient for long-term water security.
“We are not out of the woods yet, and should continue to use water sparingly and implement water conservation and water saving practices,” warns water expert Carin Bosman.
She points out that while recent inflows have been promising, the dam’s storage only increased by about 4% over the last ten days.
Bosman explains that in a typical hydrological year, the loss through evaporation and usage from the Dam is about 50% of its capacity. “If we don’t get any more good rains, we will have a 30% shortfall,” she cautioned.
While rapid filling of the dam has raised some concerns, Bosman provides reassurance about water quality.
“There are no water quality issues associated with the Vaal Dam filling up quickly. In fact, the opposite, as flushing with fresh runoff from rainfall will lead to a dilution of the contaminants that have built up over the dry season,” she explained.
Regarding infrastructure concerns, Bosman notes that proper design standards should prevent any significant issues.
“All instream infrastructure has to be designed and maintained to withstand a flood with a frequency of occurrence of 1 in 100 years, while other infrastructure has to be built outside of the 1 in 100 years flood line.
“If downstream infrastructures are damaged, it will most likely be as a result of not following these basic flood design principles.”
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South Africa’s national dam storage capacity has improved to 74.5% as of January 6, 2025, showing a 0.8% increase from the previous week’s 73.7%.
Gauteng leads the provincial statistics with 85.1% capacity, followed by the Western Cape at 83.0% and Mpumalanga at 82.3%.
“Most parts of the country received significant rainfall, resulting in increased surface water storage in majority of provinces particularly Limpopo, North West, Mpumalanga, KwaZulu-Natal and Gauteng,” the DWS reported.
“However, all overall percentages in all provinces are below 100%, but at healthy levels.”
Mpumalanga showed the most notable improvement, with storage capacity increasing from 77.5% to 82.9% in just one week.
Gauteng saw a modest increase to 85.1% from 84.0%, while Limpopo’s capacity improved from 69.8% to 73.2%. KwaZulu-Natal also recorded a 2% increase, reaching 81.0% from 79.8%.
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The DWS said it established protocols for managing the dam’s levels.
“The standard operating rule of the dam is that when it reaches 18%, we release water from Sterkfontain Dam, one of the 14 dams in the Integrated Vaal River System to replenish it,” the department stated.
The overall percentage of the Integrated Vaal River System currently stands at 71.1%.
Regarding potential flooding concerns, the DWS assured that “the standard operating procedures for flood management of Vaal Dam are in place”.
“Before the releases, the Department informs all the stakeholders downstream of the dam as per the Emergency Preparedness Plan.”
NOW READ: WATCH: Relief for the Vaal Dam as Grootdraai overflow gates open
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