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LESOTHO HIGHLANDS WATER PROJECT : KEY STATISTICS

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KATSE DAM

Katse Dam Wall

  • Type of dam : Double curvature concrete arch
  • Height above foundation : 185 m
  • Crest length : 710 m
  • Thickness of dam wall : 60 m at base and 9 m at crest
  • Spillway length : 150 m
  • Volume of concrete in wall : 2.32 million m3
  • Maximum capacity of spillway : 6 250 m3/s
  • Dead weight of dam wall : 5.5 million tonnes

Katse Reservoir

  • Total capacity : 1 950 million m3
  • Active storage : 1 519 million m3
  • Surface area at full capacity : 36 km2
  • Full supply level (ASL) : 2 053 m
  • Minimum operating level : 1 989 m
  • Mean annual precipitation at the dam : 750 mm
  • Mean annual lake evaporation at the dam : 1 160 mm

Katse Dam Catchment

  • Catchment area : 1 869 km2
  • Mean annual runoff : 560 million m3

 

MOHALE DAM

Mohale Dam Wall

  • Type of dam : Concrete Faced Rockfill
  • Height above foundation : 145 m
  • Crest length : 600 m
  • Volume of rockfill in wall : 7 million m3
  • Maximum capacity of spillway : 2 600 m3/s
  • Dead weight of dam wall : 17.5 million tonnes

Mohale Reservoir

  • Total capacity : 938 million m3
  • Active storage : 856 million m3
  • Surface area at full capacity : 22 km2
  • Full supply level (ASL) : 2 075 m
  • Minimum operating level : 2 005 m
  • Mean annual precipitation at the dam : 850 mm
  • Mean annual lake evaporation at the dam : 1 150 mm

Mohale Dam Catchment

  • Catchment area : 938 km2
  • Mean annual runoff : 315 million m3

 

MUELA DAM AND HYDROPOWER PLANT

Muela Dam

  • Type of dam : Double curvature concrete arch
  • Height above foundation : 55 m
  • Volume of concrete in wall : 60 000 m3
  • Dead weight of dam wall : 150 000 tonnes

Muela Reservoir

  • Total capacity : 6.0 million m3
  • Active storage : 4.1 million m3
  • Full supply level (ASL) : 1 775 m
  • Minimum operating level : 1 759 m
  • Maximum capacity of spillway : 584 m3/s

Muela Power Plant

  • Plant capacity (Phase 1) : 72 MW
  • Turbines : 3 Francis vertical shaft turbines @ 24 MW each
  • Maximum head : 287 m
  • Minimum head : 196 m
  • Nominal speed : 750 rev/minute
  • Generators : 32 MVA power output, 50 Hz frequency and 11kV voltage
  • Machine hall : 60 m long, 14.5 m wide and 30 m high
  • Transformer chamber : 20 m long, 12.5 m wide and 8 m high
  • Penstock valve chamber : 21 m long, 11.5 m wide and 10 m high
  • High pressure shaft : 160 m deep by 2.5 m diameter (steel lined)
  • Lift and cable shaft : 180 m deep by 5.5 m diameter (concrete lined)
  • Upstream surge shaft : 158 m deep by 9 m diameter (concrete lined)
  • Downstream surge shaft : 60 m deep by 9 m diameter (concrete lined)

 

MATSOKU DIVERSION WEIR

  • Type of dam : Stone faced concrete gravity
  • Height above foundation : 15 m
  • Crest length : 180 m

 

PHASE 1 TUNNELS

Katse Reservoir to Muela Reservoir (Transfer Tunnel)

  • Type : TBM driven with concrete lining
  • Bed rock : Basalt lava with dolerite dykes
  • Length : 45 km
  • Internal diameter : 4.5 m
  • Maximum capacity : 44 m3/s approx.
  • Contract value : $343 million @ 1990 prices

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Muela Reservoir to Vaal River basin (Delivery Tunnel)

  • Type : TBM driven with concrete lining
  • Bed rock : Sandstones and siltstones with dolerite dykes
  • Length : 37 km
  • Internal diameter : 4.6 m
  • Maximum capacity : 44 m3/s approx.
  • Contract value : $210 million @ 1990 prices

Mohale Reservoir to Katse Reservoir

  • Type : TBM driven with pre-cast concrete lining
  • Bed rock : Basalt lava with dolerite dykes
  • Length : 32 km
  • Internal diameter : 4.0 m
  • Maximum capacity : 30 m3/s approx.
  • Contract value : $145 million @ 1997 prices

Matsoku to Katse Tunnel

  • Type of tunnel : Drill and blast with concrete lining
  • Length : 5.7 km
  • Internal dimensions : 4 m wide by 5 m high
  • Gradient : 1 in 200
  • Maximum capacity : 50 m3/s
  • Contract value : $35 million @ 1997 prices