Mohale Dam - highlands water project - phase 1b

Name of Project:

Mohale Dam - highlands water project - phase 1b



Country:
Lesotho

Client:
Lesotho Highlands Development Authority

Construction period:
March 1998 - June 2002

The Mohale dam is part of the Lesotho Highlands Water Project (LHWP), one of the most ambitious multipurpose water schemes. The main purpose of the project is to deliver approximately 70 m³/s of high-quality water to the Vaal dam reservoir. The Gauteng region includes the cities of Johannesburg and Pretoria, and has the highest concentration of mining and industrial activities in South Africa.

Mohale is a 145 m high rockfill concrete-faced dam with a total embankment volume of 7.5 million m³. It is located on the Senqunyane river, 100 km east of Maseru, Lesotho’s capital city. The dam has a crest length of 700 m and crest width of 12 m and is the highest dam of this type in Africa. The ungated spillway, whose chute terminates in a flip bucket, is built on the left abutment of the dam. It has a discharge capacity of 6,000 m³/s and is completed with a stilling basin. Its construction required 30,000 m³ of concrete.

The river diversion was achieved with two concrete lined diversion tunnels blasted through the left bank, 650 m and 560 m long, with a cross-section of 6.70 x 5.50 m.

MAIN TECHNICAL DATA:
Open-air rock excavation: 500,000 m3
Underground excavation: 40,000 m3
Dam embankments: 7,200,000 m3
Upstream cofferdam embankments: 145,000 m3
Open-air concrete: 85,000 m3
Dam concrete facing: 34,000 m3
Underground concrete:  5,000 m3

OTHER PROJECTS: Lesotho

Last update: 18/09/2013