The six-month planned shutdown of the Lesotho Highlands Water Project Tunnel will not cause any disruption of water supply to Rand Water and to Gauteng municipalities and other provinces that are its customers.

The Lesotho Highlands Tunnel will be closed from 1 October to 31 March for scheduled maintenance.

“This much-needed maintenance is critical to maintain the integrity of the delivery tunnels as a tunnel failure will risk the transfer of the 780 million cubic metres per annum into the Integrated Vaal River System (IVRS) from which Rand Water draws water to supply to its customers,” said Sean Phillips, the director-general of the department of the water and sanitation, at a briefing on Friday.

During the maintenance shutdown in 2019, it was found that the steel liners in the tunnel urgently needed extensive maintenance on both the South African and Lesotho side.

The work needed during the shutdown period includes grit-blasting the steel-lined section around the entire circumference reapplying corrosion protection on the tunnel lining, and other maintenance and repair work identified during the 2019 shutdown.

“The six-month period required to conduct maintenance is crucial to avoid any catastrophic event which may result from a lack of maintenance,” he said, noting that this work is expected to protect the infrastructure for another 20 or 30 years.

According to Phillips, because of the tunnel shutdown, 700 million m³ per year will be transferred in 2024, which is 80 million m³ less than the normal annual transfer volume. After the shutdown period, the water transfers will be increased to enable that shortfall in transfers to be recovered.

In May last year, the department undertook an analysis to assess the risk to the IVRS’ performance because of the outage – and to determine the effects of the shutdown on water availability to users in South Africa.

This analysis indicated that the effects of the outage on the overall IVRS will be “insignificant” considering that at this time the dams in the IVRS such as the Sterkfontein Dam and others are relatively full, he said.

“This means that the closure of the tunnel for maintenance will not result in any disruption of water supply to Rand Water and to the municipalities in Gauteng and other provinces which are customers of Rand Water.:

The standard operating rule is that Sterkfontein Dam releases water to the Vaal Dam when the Vaal Dam reaches a minimum operating level of 18%.

The department’s analysis indicates that this is unlikely to occur at any probability level in the 2023/2024 operating year. “Hence, releases from the Sterkfontein Dam to support the Vaal Dam are not envisaged for the current 2023/2024 operating year and Sterkfontein Dam remains full to date.”

Further analysis will be undertaken in May to ensure there are also no likely risks to water supply from the IVRS in the 2024/2025 operating year. “The fact that the Sterkfontein Dam is full means that it can provide a reserve supply of water to top up the Vaal Dam as needed.”

Since 2021, he said the department has been “continuously holding meetings with stakeholders to discuss action plans compiled by the municipalities and the stakeholders, to mitigate any challenges and bottlenecks as the planned maintenance programme is implemented”.

In a letter sent to Minister of Water and Sanitation, Senzo Mchunu, and Phillips earlier this month on the closure of the tunnel, the Water Crisis Committee noted that the growing intricacy of the ongoing water crisis in Johannesburg has raised “significant concerns”, prompting the need for coordinated efforts from the department, Rand Water, Johannesburg Water, municipalities, and civil society to address the challenges effectively.

The committee was formed in October last year by Johannesburg residents deeply affected by prolonged and unexplained water shortages.

“We acknowledge that the department of … is liaising with municipalities and has devised plans to ensure continuous water supply during the shutdown,” read the letter. “To prevent misinformation and fear-mongering, it is crucial to inform all water consumers well in advance and encourage prudent planning for the period of disruption. The Water Crisis Committee’s priority is to ensure citizens are well-informed, prepared, and have access to essential water for dignified living.”

Phillips added that the planned closure of the tunnel for maintenance will not have any effect on the ongoing construction of Phase II of the Lesotho Highlands Project.

He said that the main contracts for the new dam and the tunnel were awarded in October 2022. “The contractors are on site, and the project is on track to start delivering additional water into the IVRS in 2028.”