Table 4: Samanalawewa Hydroelectric Project Main Characteristics

Type Rock Fill Earth Core
Height 100m
Length 530m
Volume of fill 4.5Mm3
Catchment Area 341.7Km2
Annual Average runoff 598Mm3
Normal High Water Level EL 460m
High Flood Level EL 460.7m
Minimum Operation Level EL 424m
Live Storage Capacity 218Mm3
Type Gated overflow chute
Design Discharge 3600m3/sec (10,000 year flood)
Number of gates 03 Nos.
Dimensions 12m wide, 14m high
Spillway Ogee Level EL 446.7m
Diversion Tunnels
Number of Diversion Tunnels 02 Nos.
Diameter 6.8m
Length 550m
Designed Capacity 145m3/sec (100 year flood)
Low Level Outlets
Emergency Release Gate 2.0m x 2.0m Jet Flow Gate
Irrigation Release Gate 0.6m dia. Pipe with Howel Bunger Valve
Head Race Tunnel
Diameter 4.5m (concrete lined dia.)
Length 5350m
Surge Chamber
Type Restricted Orifice Type
Diameter of Riser 6.0m
Diameter of Chamber 18.0m
Height 94 m
Type Steel Surface
Diameter 3.85m to 2.85m
Length 840m
Power Station
Type Surface
Number of Units 02
Installed Capacity 120MW (2 x 60 MW)
Average Annual Energy 403GWh
Turbine Type Francis
Turbine – Rated Head 320m
Rated Discharge 42m3/sec
Speed 500rpm
Rated Output 62MW
Rated Output 71.6MVA
Power factor 0.85
Generated Voltage 10.5kV
Fly wheel effect (GD2) 715tm2
Type Open Cannel
Length 585m
Power Transmission
Transformers 02 Nos., 75 MVA, 3 phase
Transmission Line 132kV double circuit 17km to Balangoda