Lesotho Highlands Water Project shutdown to leave Gauteng 80 billion litres short

Gauteng and parts of four other provinces are being warned to make every drop of water count for the next six months.

The Lesotho Highlands Water Project (LHWP) shutdown is two weeks away and will run from 1 October to 31 March next year.

Maintenance on the LHWP tunnels will leave three Free State municipalities and all Rand Water customers reliant on dam levels to preserve their water security.

Rain to mitigate shutdown effects

The Trans-Caledon Tunnel Authority (TCTA) is responsible for the South African side of the LHWP, with the Katse and Mohale dams serving as the main feeders from across the border.

TCTA’s Head of Communications Wanda Mkutshulwa explained in detail to The Citizen the ramifications of the six-month shutdown.

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Gauteng is the largest sponge attached the LHWP, absorbing its colossal hydration needs from the Intergrated Vaal River System (IVRS).

“It’s important to point out that the IVRS is made up of 14 major and minor dams, of which only two are in Lesotho, and will be affected by the tunnel closure,” says Mkutshulwa.

“Other factors may impact the availability of water in the province, as is being currently reported, but these will most likely be mitigated by the anticipated summer rains,” he adds.

Dam levels across the interior are at varying levels. To top up the system before the shutdown, 100 million cubic metres are being released.

“However, it is still expected that, despite this additional allocation, there will be a minor shortfall of transfer for the LHWP of approximately 80 million cubic metres,” confirmed Mkutshulwa.

How much is a million cubic metres?

One cubic metre of water is equal to 1000 litres, making the shortfall approximately 80 billion litres.

A rectangular nine by four metre swimming pool with a depth of 1.2 metres has a volume of just under 50,000 litres, making the expected shortfall the equivalent of roughly 1.6 million average residential swimming pools.

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The Department of Water and Sanitation (DWS) states that as of 9 September, the Vaal River sat at 44% of its 2.6 billion cubic metre storage capacity, while the Sterkfontein Dam, which has a similar capacity, was at 97%.  

Mkutshulwa explained that the design of the IVRS has the dams complement each other to ensure the stability of the network.

“The standard operating rule is that Sterkfontein Dam releases water to the Vaal Dam when the Vaal Dam reaches a critically low water level.

“The Sterkfontein Dam is currently full and is being used to top up the Vaal Dam as deemed necessary,” he said.

A diagram of the IVRS from its source in Lesotho to the main supply dams. Picture: Supplied by TCTA.

Free State municipal readiness

The Free State municipalities affected by the shutdown will be the Dihlabeng, Nketona and Mafube Local Municipalities.

Areas in KwaZulu-Natal serviced by the Woodstock Dam, those in Mpumalanga serviced by the Grootdraai Dam and residents in the Free State and North-West relying on the Bloemhof Dam are all affected.

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Minister of Water and Sanitation Pemmy Majodina over the weekend urged the Free State municipalities to speed up their preparation efforts, saying some were lagging in their readiness.

“Where necessary, the DWS will intervene to support the municipalities to complete the projects which are critical in ensuring sustainable water supply to communities during the tunnel system shutdown,” stated Majodina on Sunday.

Vaal and Sterkfontein Dams ‘sufficient’ for Gauteng

An enquiry to Rand Water to ask about their readiness, with those questions being diverted the DWS, who were confident that areas serviced by the IVRS would be adequately supplied.

“[DWS] analysis confirmed that the impact of the tunnel closure on the overall IVRS will be minimal, considering that most dams in the IVRS are currently relatively full,” DWS’ Sanku Tsunke told The Citizen.

“There is a 95% probability that there will be sufficient water in the IVRS (excluding Sterkfontein Dam) during the tunnel closure period,” he added.

Rand Water had previously stated that they supplied roughly four billion litres per day, or roughly 720 billion litres over a six month period.

However, Mkutshulwa reiterated the reliance on rain, saying: “This shutdown is planned to be conducted during the summer season and any rainfall during the season will assist in managing the shortfall”.