Construction of the Polihali Dam, the massive concrete-faced rockfill dam (CFRD) being constructed in the Lesotho eastern highlands under Phase II of the Lesotho Highlands Water Project (LHWP) is now 50% complete and is on track for the start of impoundment in the 2027/2028 rainy season.

With the construction of multiple elements of the Polihali Dam infrastructure underway simultaneously, the site is a hive of activity and construction achievements.
Recent construction milestones on the main dam include reaching elevation 2 020 on the rockfill and upstream concrete curb in mid-May slightly ahead of the construction programme timelines. By the end of June the upstream concrete curb and rockfill had reached the 2 024 metre elevation. With a total of 9.6million cubic metres of rock placed at an average of 26 000 cubic metres per work day, the rockfill on the 166-metre high concrete faced rockfill dam is now 67% complete. The next step is to raise the rockfill on the downstream side of the dam to equal the upstream rockfill and concrete curb; thus achieving the third milestone.

The concrete curb forms a competent clean surface for the face slab construction, and the casting of the starter slabs for the main face slab is underway. The starter slabs are initial reinforced concrete panels constructed immediately adjacent to the toe slab or plinth at the base of the dam’s upstream slope. They serve as the starting point for constructing the main concrete face. Concrete works on the main dam internal and external plinths are complete.

Work on the saddle dam which is a 43-metre high CFRD, and is in itself a large dam, has progressed well. At the end of June, 375 627 cubic metres of rock had been placed for the saddle dam wall; the internal and external plinth concrete works were complete and the concrete curb on the upstream side of the dam wall had reached the 2 047 metre elevation.

The intake tower – a massive concrete structure 100 metres high by 21 metres across, similar to the one at Katse – is underway. The intake tower is a hydraulic structure located upstream dedicated to managing water flow.

The bottom outlet tunnel with its embedded 2.2 metre diameter compensation pipe, the source of downstream releases to the river, will also feed a small hydropower station of 4.4 megawatts. It is also progressing well.

The spillway, another extremely large concrete structure, also continues both with final excavation and concrete construction. Excavation of the plunge pool is also underway.

While the physical construction progress is clearly visible, there are other achievements on the Polihali Dam project which are a source of pride to the LHDA and the project team. These include its zero fatalities and high lost time injury-free numbers, and that it has created employment for many people. By the end of April that figure stood at 2 709 people. Of these, 2 062 are semi-skilled employees, 99% of whom are Basotho nationals, contributing to enhancing skills and hands on learning in the country.

The Polihali Dam is approximately one kilometre downstream of the confluence of the Khubelu and Senqu (Orange) rivers. It will create a reservoir capable of storing 2 325 million cubic metres of water and will enable water delivery to South Africa to be increased incrementally from the current 780 million cubic metres per year to 1 270 million cubic metres annually.

As construction progresses toward its expected completion in 2029, the Polihali Dam is testament to what can be achieved through innovative engineering, international cooperation, and a vision for sustainable development. It is not just a dam; it is a catalyst for regional transformation enhancing water and energy security and regional connectivity.

The Lesotho Highlands Water Project is a model for large-scale infrastructure projects enhancing the LHWP’s position as Africa’s benchmark in cutting edge engineering at high altitude.

2026 marks the 40th anniversary of the signing of the LHWP Treaty, a proud moment in the history of the project and the Lesotho Highlands Development Authority.