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LESOTHO HIGHLANDS WATER PROJECT PHASE

2OVERVIEWBy P D Pyke

October 2012

Yield analysis - Polihali

• Dam yield ( MOL 1992, FSL 2065) viewed in isolation:– 14,75 m3/s 465mil. m3/a

• Incremental Orange River system yield– 5,76m3/s 182 mill.m3/a

• Phase 1 Dams Yield • 780 106 m3/annum• 24.7 m3/s• Polihali Contribution to System Yield (of LHWP)• 465 106 m3/annum• 14.75 m3/s• Total LHWP Phase1 and Phase 2 Yield • 1271 106 m3/annum• 40.3 m3/s - but also need yield replacement

dam for Orange River

Polihali Yield Analysis

Main Embankment

Main dam

Maximum height 163.5 m

Essential Excavation 40 000 m3

Dam fill volume 12 311 210 m3

U/s and d/s slope u/s 1: 1.4d/s 1:1.25, average 1:1.4

Crest width / length 10 / 915 m

Reservoir Volume 2 322 million m3

Surface area 50.4 km2