The Department of Water and Sanitation would like to update the water users of the Integrated Vaal River System (IVRS) about the planned maintenance work on the transfer and delivery tunnels of the Lesotho Highlands Water Project (LHWP) over the six-month period, from 1 October 2024 to 31 March 2025.
The Lesotho Highlands Water Project
The LHWP is a water supply project with a hydropower component (it supplies hydropower to Lesotho). It was developed as a partnership between Lesotho and South Africa. It comprises several large dams and tunnels throughout Lesotho. Lesotho is paid royalties by South Africa for the water. A treaty was signed by the two governments in 1986, indicating that the project would be implemented in phases. Phase 1, consisting of the Katse Dam, Muela power station, Mohale Dam, and 82 km of tunnels was completed in 2003. Phase 1 transfers 780 million cubic metres of water per annum into the IVRS.
Phase 2 of the project, which is currently under construction, includes a 165m high Concrete Faced Rockfill Dam at Polihali and a 38km long concrete-lined gravity tunnel connecting the Polihali Dam reservoir to the Katse Dam. Once completed, LHWP 2 will transfer an additional 490 million cubic meters of water per annum from the Orange (Sengu) River in Lesotho into the IVRS in South Africa.
The maintenance work to be carried out
The tunnel system consists of a Transfer Tunnel, linking Katse Dam with Muela Power Station and Muela Dam, and a Delivery Tunnel, linking Muela Dam with the Ash River Outfall Works between Clarens and Bethlehem.
Inspections and maintenance of the tunnels must be conducted at intervals between five and ten years. 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 RSA and Lesotho side. This process will take six months to complete.
The planned maintenance work is being overseen by the Lesotho Highlands Water Commission (a joint governance body between the Republic of South Africa and the Government of Lesotho) and will be jointly undertaken by the Lesotho Highlands Development Agency (LHDA) and the Trans Caledon Tunnel Authority (TCTA) (an entity under the Minister of Water and Sanitation).
The work required to be undertaken during the shutdown period includes grit-blasting the steel-lined section around the entire circumference and re-applying corrosion protection on the tunnel lining, as well as other maintenance and repair work identified during the 2019 maintenance shutdown. This work is expected to protect the infrastructure for another 20-30 years.
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 m3/annum of water to the Integrated Vaal River System (IVRS), from which Rand Water draws water to supply its customers. The six months period required to conduct maintenance is thus crucial to avoid any catastrophic event which may result from a lack of maintenance.
Impact of the maintenance work on the Integrated Vaal River System and Rand Water
As a result of the tunnel shutdown, 700 million m3 per annum will be transferred in 2024, a shortfall of 80 million m3 from the normal annual transfer volume. After the shutdown period, the water transfers will be increased to enable the shortfall in transfers to be recovered.
An analysis was undertaken in May 2023 to assess the risk to the IVRS’ performance as a result of the outage, and to determine the impact of the shutdown on water availability to users in South Africa. 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. 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 (1 May – 31 April). Hence, releases from 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 2024 to ensure that 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.
Impact of the maintenance work on towns and irrigators in the Free State
The shutdown will also not have any significant water supply implications for domestic users along the Liebenbergsvlei River and its tributaries in the Free State during that period. The Liebenbergsvlei River normally receives outflows from the tunnel. However, while the tunnel is shut down, additional water will be supplied from the Saulspoort Dam (which will be filled with water before the commencement of the shutdown period), and this will ensure that the water requirements of towns along the river, including Bethlehem, Reitz, and Tweeling will have sufficient water for the duration of the tunnel shutdown.
Licensed irrigators along the Liebenbergsvlei River and its tributaries will be provided with notices to restrict their abstraction during the shutdown period to certain days of the week, so that they abstract water from rivers fed by the Saulspoort Dam in a sustainable way during the tunnel closure. Abstraction of water from the river will be closely monitored by the department during the closure to ensure that there is no illegal abstraction which might affect the ability of licensed irrigators to abstract the water which they require.
Consultation with stakeholders
The Department started engagements with all the affected municipalities in 2021, as well as other interested and affected stakeholders and government departments, informing them of the planned tunnel closure. Subsequently, the Department has been continuously holding meetings with these 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.
The Department has also developed communication and stakeholder engagement plans that tie in with the stakeholder engagement plans that each of the three affected municipalities in Free State must also have in place and these are currently being rolled out to ensure that all water users including members of the communities that will be affected are informed and participate in relevant activities that will ensure that the programme is implemented successfully with minimal disruptions to livelihoods.
The Department would like to urge all water users who will be affected by the planned tunnel maintenance to use water sparingly during this period, as a means of managing any unforeseen risks. A water restrictions notice is being prepared in this regard.
Continuation of Phase II of the Lesotho Highlands Project
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. 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.
