Lesotho Highlands Tunnel maintenance will not affect Gauteng water supply

The Water and Sanitation Director-General, Dr. Sean Phillips has assured residents of Gauteng that the planned closure of the Lesotho Highlands Water Tunnel for six months will not disrupt water supply to Rand Water and the availability of raw water.

Speaking in Pretoria on Friday, Phillips briefed the media on the scheduled maintenance work on transfer and delivery tunnels of the Lesotho Highlands Water Project , set to commence from 1 October, to 31 March.

Tunnel maintenance urgently required

“The last maintenance was conducted in 2019. During the shutdown of 2019 it was found that the steel liners in the tunnel urgently need extensive maintenance on both the Republic of South Africa and Lesotho side,” Phillips said.

The tunnel system encompasses a transfer tunnel, connecting Katse Dam with Muela Power Station and Muela Dam, as well as a delivery tunnel linking Muela Dam with the Ash River Outfall Works between Clarens and Bethlehem.

Phillips emphasised the importance of periodic inspections and maintenance, noting that the last maintenance took place in 2019, revealing urgent steel liner maintenance needs on both the South African and Lesotho sides.

Lesotho Highlands Water Commission oversees joint maintenance effort

Overseen by the Lesotho Highlands Water Commission, the joint governance body between South Africa and Lesotho, the maintenance work will be jointly carried out by the Lesotho Highlands Development Agency (LHDA) and the Trans Caledon Tunnel Authority (TCTA), an entity under the Water and Sanitation Department.

The tasks during the shutdown period include grit-blasting the steel-lined section, applying corrosion protection, and other identified maintenance and repair work from 2019.

Phillips stressed the time-intensive nature of the work, essential for safeguarding the infrastructure for another 20-30 years. He highlighted the risk associated with tunnel failure, which could disrupt the transfer of 780 million m3/annum of water to the Integrated Vaal River System (IVRS), from which Rand Water draws its supply.

Addressing the impact on the IVRS and Rand Water, Phillips noted a planned transfer reduction in 2024, with subsequent increases post-shutdown to recover the shortfall.

An analysis conducted in May 2023 indicated minimal impact on the IVRS performance, considering the reservoir levels. Further analysis is slated for May 2024 to mitigate risks for the 2024-2025 operating year.

Phillips assured that the Sterkfontein Dam’s full capacity serves as a reserve supply, minimising disruptions.