Lesotho launches Polihali dam project

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Construction Review Online

Lesotho has launched the construction of Polihali dam in a ceremony that brought together dignitaries from the Kingdom of Lesotho and representatives of the South African government. The Polihali dam will be useful to both countries.

The project The dam will store part of the waters of the Orange River (Senqu) and the Khubelu River. Its concrete rockfill wall will be 165m high with a ridge length of 921m and a ridge width of 9m. At its base, the slope will be 470m wide. The dam will have a spillway with a concrete side channel spillway.

The Lesotho Highlands Development Authority (LHDA) estimates that 13 million cubic metres of rock will be extracted from the dam site and compacted for backfill construction. The Polihali dam will form a reservoir on the Orange and Khubelu rivers covering an area of 5,053 hectares, with a total storage capacity of 2,325 million cubic metres. It will be supported by a saddle dam, an auxiliary reservoir built to contain the reservoir created by a primary dam.

Lesotho highlands water supply programme The construction of the Polihali Dam is part of Phase II of the Lesotho Highlands Water Supply Project. It is a programme to build several dams in Lesotho to capture the waters of the upper Orange River Basin and reverse part of its flow in order to provide South Africa, and in particular the Johannesburg region, with drinking water. Two tunnels are under construction to supply the Polihali dam.

The work is being carried out by SCLC Polihali Diversion Tunnel Joint-Venture, a joint venture formed by the Italian companies Salini Impregilo and Cooperativa Muratori Cementisti CMC di Ravenna, as well as the South African company CMI Infrastructure and LSP Construction from Lesotho. Part of the water from the Polihali dam will be transferred to the Katse dam in South Africa via a tunnel while some of the water will be used to generate electricity for Lesotho.

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