The £2 billion (R14 billion) Lesotho Highland water project is one of the largest civil engineering projects currently under way in the world. When the £840 million (R5, 88 billion) first phase (IA) opens in 1998, it will be transferring 18m<sup>3</sup>/s of water from new reservoirs in Lesotho to the industrial heartland of South Africa and generating 72 MW of hydroelectricity. This paper introduces the basic elements of the project and then describes the management structures established for the project's implementation in terms of a treaty between the governments of Lesotho and South Africa. It also describes the infrastructure established for the project, financing and environmental considerations.
This paper describes the design of the 185m high double-curvature concrete-arch dam at Katse, the main impounding reservoir for the Lesotho Highlands water project. The £230 million (R1, 61 billion) project involved excavating 1, 3Mm<sup>3</sup> of concrete in just 77 months. In addition to the main dam, the project includes a 500kW mini-hydro plant and a 32m high concrete tailwater dam for the plunge pool. Concerns about the integrity of the basalt lava flows beneath the main dam led to the use of a preformed joint at the base of the dam to limit uplift and a novel system of massive concrete shear keys.
This paper describes the design and construction of the 45km long, 4, 35m diameter transfer tunnel on phase 1A of the Lesotho Highlands water project. The tunnel transfers water from the new Katse reservoir to the new underground hydro-electric power station at 'Muela in Lesotho. It was driven entirely through basaltic rock using three 5, 03m diameter TBMs and then lined with 300mm in situconcrete. The project also included a 98m high reinforced concrete intake tower in the Katse reservoir and five raise-bored ventilation shafts up to 299m deep.
A 72MW hydropower station is included in phase 1A of the Lesotho Highlands water project to allow Lesotho to become self-sufficient in energy production. This paper describes the design of the 'Muela underground power station and regulating reservoir formed by a 55m high dam. Features include the accommodation of hydraulic transients arising in the 45km long upstream tunnel, the changes made in the dam to take account of a thin clay layer in one abutment and the special consideration given to the provision of a bypass to allow water transfer to take place when the station is out of commission.
The delivery tunnel op phase 1A of the Lesotho Highlands water project extends 37km from the 'Muela reservoir in Lesotho to an outfall on the Ash/Axle River near Clarens in South Africa. The tunnel, for which tender design was carried out by one design consultant, was procured as two entirely separate detailed design and two separate construction contracts - the 15km southern section in Lesotho and the 22km northern contract in South Africa. Both contracts were completed successfully within time and budget. This paper introduces the overall tunnel project and then describes the work undertaken in each of the two separate design and construction contracts.