The seven-month maintenance work on the Lesotho Highlands Water Project (LHWP) tunnel has been successfully completed, with water once again flowing from Lesotho into South Africa.

The process of refilling the tunnel with water, which takes about one month, started on May 13 – six weeks later than initially planned.

The LHWP tunnel system was closed on October 1 for six months for a joint maintenance operation undertaken by the Trans Caledon Tunnel Authority (TCTA), on Delivery Tunnel North in South Africa, and the Lesotho Highlands Development Agency (LHDA), on the Transfer and Delivery South Tunnels in Lesotho.

The tunnel was scheduled to reopen in March this year, but maintenance work delays experienced in the Delivery Tunnel South, in Lesotho, extended the closure to allow the maintenance work to be completed.

While the TCTA’s maintenance work on the South African side was completed on March 19, ever-changing weather patterns and technical challenges on the Lesotho side of the tunnel presented challenges that led to implementing agent LHDA requesting an extension.

With the work completed, work to fill the tunnel started with the filling of Muela dam in Lesotho between May 13 and 17.

Water from Lesotho reached the Little Caledon tunnel on May 21 and the Ash River Outfall Works, in Clarens, in the Free State, on May 22.

The maintenance work was aimed at protecting the infrastructure, which supplies Gauteng and surrounds with 780-million cubic metres of water a year.

After the month-long process of dewatering the tunnel and conducting general inspections, the repairs started on November 1.

The work included various technical, civil, mechanical, and electrical engineering tasks, as well as sand sandblasting, including the recoating of the steel lining of the tunnel and removing corrosion that had built up over many years.

At the time, the Department of Water and Sanitation provided a three-month buffer beyond the initial six months – with Sterkfontein dam and other storage dams within the Integrated Vaal River System on standby to release water into the Vaal dam if its levels dropped to 18%.

Further, about 700-million cubic metres of water had been transferred in anticipation of the closure, with the remaining 80-million cubic metres for 2024 to be transferred once maintenance has been completed.