Despite Phase 2 of the Lesotho Highlands Water Project (LHWP) being under way, South Africa has to ensure that it reduces its water use and water losses before Phase 2 is commissioned in 2024.

Currently, 37% of all water supplied by municipalities is lost through leaking pipes, dripping taps and other infrastructure failures.

South African Institution of Civil Engineering president elect Chris Herold tells Engineering News that the LHWP would be viable, based on the assumption that South Africa reduces its total water demand by 15% by implementing water demand management to reduce water losses because of leaks.

Former Department of Water Affairs (DWA) director-general during Phase 1A and 1B for the project Mike Muller tells Engineering News that the LHWP will be essential for the water security of Gauteng and the surrounding areas, as it will add a significant contribution to the water available in the Vaal River System.

However, he expects the dam to meet Gauteng’s water needs until about 2030, but advises that, as South Africa’s population grows, the country needs to become accustomed to consuming less water. He also cautions that the Gauteng region will be vulnerable if there is a serious drought before the Polihali dam is commissioned.

Herold agrees, adding that South Africa, whose water demands are high, will not have sufficient water reserves to sufficiently mitigate the effects of a serious drought.

“We would have to impose severe water restrictions to supply everyone and we are already in a deficit. If we carry on without achieving the 15% water demand management target, then nearly all of the Polihali dam’s capacity would already be committed by the time it is commissioned. We would then need to commission the next scheme almost immediately afterwards and it is, therefore, critical that we get out of the deficit situation,” he explains.

Building new water infrastructure to meet incremental growth, such as population, is important for the Vaal system and many other regions, but the most viable solution is to reduce water demand, not just increase water supply, Herold states.

However, he says the LHWP interbasin transfer is the most feasible and economical method of increasing water supply for the Vaal system, as the water is delivered by gravity.

Council of Scientific and Industrial Research water resources competency area manager Harrison Pienaar says, while interbasin transfers remain critical for developing countries like South Africa, other interventions that are being considered to increase the country’s water supply include scientific engineering and technology options to promote and improve water use efficiency, water loss control, augmentation of local resources, effluent reuse and desalination.

At the same time, water treatment options to improve water resource quality are equally important, since quality and quantity dynamics are inextricably linked, he says.

Muller predicts that more water will be desalinated over the next few decades in South Africa’s coastal cities with more water recycled inland.
He says the environmental contribution of the LHWP should be celebrated.
“Instead of pumping water all the way from the Eastern Cape, where the Orange river flows from Lesotho into South Africa, it saves money and energy by diverting the water from the top of the Drakensberg, directly to users by gravity,” he says.

Phase 2 Components
Phase 2 of the LHWP will be implemented in terms of the agreement pertaining to two distinct but related systems – a water delivery system to augment the delivery of water to South Africa and using that water delivery system for hydropower generation.

The water delivery system comprises the Polihali reservoir on the Senqu river, in Lesotho.

The 2 322-million cubic metre Polihali dam will be constructed downstream of the confluence of the Senqu and Khubelu rivers, in Lesotho, and will be a 163.5-m-high concrete- faced rock-fill embankment dam wall.

The crest length will be 915 m, with a full supply level of 2 075 m above sea level. A 49.5-m-high saddle dam and a side channel spillway will also be constructed.

The Polihali-Katse tunnel, in Lesotho, will comprise a 38.2-km-long, 5.2-m-diameter water conveyance tunnel, connecting the Polihali reservoir with the Katse reservoir.

The Lesotho Highlands Development Authority (LHDA) tells Engineering News that the procurement for consultants for the water delivery aspect of Phase 2 is under way and is expected to continue until the end of 2017.

This stage includes the procurement of consultants for professional services pertaining to advance infrastructure works, such as roads, bridges, housing, telecommunications and main works – which includes the dam and tunnel – as well as environmental, social and public health aspects.

The procurement of consultants to undertake a further feasibility study on the hydropower generation system is also under way.

Three consulting contracts were awarded from March to April this year. They comprise the demarcation of the Polihali reservoir, the initial work on the Polihali north-east access road, and professional services for the evaluation, optimisation and site supervision of geotechnical investigations.

The LHDA also recently awarded a R74.3-million professional services contract for the planning, design and construction supervision of the housing and associated infrastructure for Phase 2 to Polihali Infrastructure Consultants – a joint venture between consultancy firm Mott MacDonald and architecture firm Khatleli Tomane Moteane.

The contract forms part of the advance infrastructure works that must be completed to facilitate the construction of the main works – the Polihali dam, transfer tunnel and hydropower station.

The contract began last month and is expected to be completed in 2021. It includes the preparation of preliminary and detailed architectural and engineering designs of temporary and permanent housing and associated infrastructure, the preliminary and detailed design of utilities, the preparation of tenders and contract documents, the procurement of construction contracts, the supervision of the construction programme and environmental monitoring during construction.

The housing project comprises accommodation facilities for the staff and labour force, site offices, workshops, plant yards and other work areas.

Some of the structures built as part of the professional services contract are intended for long-term use. These include staff accommodation in the Polihali reservoir areas that will be built as a village, with all the appropriate associated facilities; a visitor’s lodge at the staff village, which will become a tourist facility; and the employer’s and engineer’s offices at the dam site, which will become the operation’s staff offices and a visitors centre on completion of the scheme.

Construction
The construction of the Polihali dam and the Polihali-Katse tunnel is expected to begin at the end of 2018.

The LHDA tells Engineering News that the timeframe for the construction of the dam will begin with the appointment of the design consultant, which is expected at the end of 2016.

Construction of the dam should be completed by the second half of 2023, if the programme proceeds as planned.

The construction of the tunnel will begin following the appointment of a consultant in 2016 and the tunnel is expected to be completed in mid-2024.

The LHDA says the cost of the water- transfer component is expected to be about R22.9-billion on completion, but adds that measures are being investigated to actively contain project costs.

The expected value of the hydropower component of the project has not been ascertained, owing to the further feasibility studies currently under way.