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The Lesotho Highlands Water Project is one of the largest and most intricate construction projects currently underway in the world. The components included in the project tend to vary from one report to another but in general the total project was originally envisaged to transfer 70 m3/s from the upper portions of the Lesotho Highlands into the Vaal River basin. The scheme was designed in phases, with each phase providing additional transfer capacity to the previous phase with the ultimate transfer of 70 m3/s only being achieved on completion of the final phase.

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Although several configurations have been investigated, the latest generally accepted proposal is for a scheme comprising up to 6 different phases, of which only the first two (phases 1a and 1b) have been approved to date (April 1998).  The most generally accepted components are as follows:


Phase 1a

  • the 185 m high Katse Dam;
  • the intake structure capable of handling 70 m3/s ;
  • the 45 km long transfer tunnel from Katse reservoir to the Muela reservoir
  • the Muela Dam and hydro-power station;
  • the 37 km long delivery tunnel from the Muela reservoir to the Vaal River basin.

Phase 1b

  • the 145 m high Mohale Dam;
  • the 32 km long transfer tunnel from the Mohale reservoir to upstream of Katse Dam;
  • the 15 m high Matsoku Diversion Weir;
  • the 5.7 km long transfer tunnel from the Matsoku Weir to Katse Dam.

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