Experts allay worries over decline in Vaal Dam level

It is not time to panic over the declining water level at Vaal Dam, although it is worrying, say water experts.

Ferrial Adam, executive manager of WaterCAN said she hadn’t panicked yet, but was concerned.

This followed an announcement by the department of water and sanitation that it would release water from Sterkfontein Dam into the Vaal Dam if the level dropped from the current 28.2% to 18%.

Declining Vaal Dam water level

Adam said she would only start to panic when the level dropped to 18%, when asked what the government was doing to avert drought.

“In the meantime, we need to prepare,” said Adam.

“So, what else is the government putting in place to manage a potential drought? We need some good rain,” she said.

ALSO READ: Vaal Dam now below a third of its capacity

“We need better enforcement of level 1 restrictions. I am still seeing people using hosepipes and watering gardens at midday and these are not residents, but malls and wedding venues.”

Hennops River Revival founder Tarryn Johnston said: “We know there is enough water. But what about the water footprint, what is the quality, and what does it do to the cost of treatment and, ultimately, the consumer price?”

Johnston said Gauteng lost about 49.2% of water, which was higher than the previous year’s 46.2%.

Gauteng lost 49.2% of water

“How much more are we going to pay for water we don’t get because things are not getting fixed and is it worth it to increase the cost if we’re not going to get it?”

This week the department of water and sanitation (DWS) spokesperson Wisane Mavasa said measures were in place for the release of water from Sterkfontein Dam into the Vaal Dam to augment its level when it reached 18%.

“The standard operating rule for releases of water from Sterkfontein into the Vaal Dam is when the Vaal Dam reaches 18% of its capacity,” she said.

ALSO READ: Vaal Dam levels drop by 15 percentage points in two months, but ‘not a significant concern’ yet

Mavasa said the dam was at 28.2% and had been falling by 1.5 to 2% weekly, primarily due to climatic factors, including low inflows owing to lack of rainfall in the Vaal catchment area and elevated temperatures.

Because the surface area of Vaal Dam was so wide and shallow it was susceptible to high evaporation losses, she said.

“Another cause for the drop in levels is due to low inflows as a result of the Lesotho Highlands Water Project (LHWP) tunnel closure for planned maintenance work currently underway.

Low inflows because of LHWP tunnel closure

“The tunnel transfers 780 million cubic metres of water per annum into the Integrated Vaal River System [IVRS],” she said.

Mavasa said there was a shortfall of 80 million from the normal annual transfer volume this year due to the shutdown.

“The DWS analysis was conducted to assess the risk of the IVRS performance as a result of the tunnel closure for six months, from 1 October to 31 March 2025.

ALSO READ: Rand Water rubbishes claims of ‘poisoned’ Vaal Dam water

“The results of the analysis indicated the impact of the outage on the overall IVRS will be insignificant considering that dams in the IVRS such as the Sterkfontein Dam and others are relatively full,” she said.

Mavasa said this meant the closure of the tunnel would not result in any disruption of water supply to Rand Water and municipalities in Gauteng and other provinces.

When the analysis was done in May, there was a low probability for the release from Sterkfontein Dam to augment Vaal Dam.

Low probability probability for release from Sterkfontein Dam

“This low risk was assessed at 5%. It has been noted that this 5% probability has materialised due to below-normal rainfall and high evaporation rates,” she said.

The department has since issued a notice to water users and the general public along the Nuwejaarspruit and Wilge rivers of possible release of water from Sterkfontein.