Revised operating rules for the Lesotho Highlands Water Project (LHWP) are currently being negotiated, and South Africa must use the opportunity to improve operation, reduce waste and keep the region water secure, the South African Academy of Engineering (SAAE) said in a new advisory note.

In a statement accompanying its 'Building a Better post-Covid Water Sector Advisory Note 5: Revision of operating rules for the Lesotho Highlands Water Project', the SAAE called on the South African government to engage urgently with Lesotho to end the wasteful release of water from the Katse and Mohale dams.

“Water is being released to generate hydropower in Lesotho, even when the Vaal and Bloemhof dams in South Africa are full and overflowing and the Lesotho dams are less than 65% full. As a result, water that could have been stored in Lesotho as a reserve, in case of future drought in South Africa, is being permanently lost,” it said.

The 14 dams of the Integrated Vaal River Supply System (IVRS), which provide a reliable water supply to the economic heartland of South Africa, are increasingly under strain owing to rising demand from population growth and economic activity.

“Supply from the IVRS will come under increasing strain until the Polihali dam, the next stage of the LHWP, is completed in 2028. It is critical that all options are considered to maintain reserves to ensure that the IVRS region is resilient to droughts during this period.”

In April, when both Vaal and Bloemhof were full and overflowing, the Vaal dam at 105% capacity and Bloemhof at 109%, water continued to be released from Katse and Mohale even though they were still recovering from earlier drought and only 79% and 40% full, respectively.

“At present, the way the IVRS is operated wastes water. When there are good rains, instead of storing the water to use when it is needed, the Katse and Mohale dams in Lesotho release a continual flow to Vaal and Bloemhof dams. If those dams are full, water from the IVRS simply runs to the sea,” the SAAE says.

As a result, a huge volume of water, equating to almost 8% of the total IVRS storage capacity, that could have been stored in Lesotho’s dams was lost to potential users.

“This approach also increases evaporation, another source of water losses. Less water would be lost through evaporation if it was stored in Lesotho deep cool dams rather than in the shallower and warmer Vaal dam.”

“This inefficient operation puts the security of IVRS users at risk and should be ended. This will require amendments to the agreement between Lesotho and South Africa on operating arrangements. However, the current negotiations are only considering the operation of the new Polihali dam. Their scope must be expanded to address the whole LHWP system, as was intended under the revised Treaty between the countries,” the SAAE said.

The original LHWP Treaty agreement, signed in 1986, allowed Lesotho to build the 72 MW Muela hydropower station as an ancillary development, using the water released to South Africa to generate electricity.

“If it agrees to change its operating routines and keep additional water in storage rather than always releasing a constant flow to generate electricity, Lesotho will have to be compensated financially or in kind to ensure that its users and institutions are no worse off than before. In addition, the South African government will have to guarantee that South Africa’s Eskom will supply electricity to Lesotho under conditions no less favourable than those enjoyed with Muela generating,” the academy explained.

However, the costs involved for South Africa will be small compared with those that would be caused by severe drought restrictions across Gauteng and the wider IVRS.

“Cape Town’s Day Zero experience cost the City billions of Rand, so compensation to Lesotho for the insurance provided by their storage would be cheap at the price.”

Greater cooperation in water releases may also bring additional benefits to Lesotho if it can coordinate with South African State-owned power utility Eskom to generate electricity at peak periods, when it is more valuable, particularly as the proportion of intermittent renewable sources supplying South Africa’s grid increases.

“Detailed technical consultations between water and electricity authorities in both Lesotho and South Africa will be required to design, agree and implement new operating arrangements. However, the operating and royalty payment negotiations now underway are only focusing on LHWP2. It is urgent to ensure that these additional issues are placed on the agenda and finalised as part of the revised LHWP agreement.”

The SAAE has urged Water and Sanitation Minister Senzo Mchunu and his counterparts in the departments of Mineral Resources and Energy, Public Enterprises, and International Relations and Cooperation, and the Treasury, to engage with Lesotho and to agree on operating arrangements that maintain South Africa’s resilience to drought and on compensation to Lesotho for loss of income that might be incurred from reduced water transfers and electricity generation at their Muela hydropower station.

The SAAE has offered to support the process if required.