Gandaki Gaupalika-08, Gorkha +977-010-416081/82 info@bghep.gov.np

Government of Nepal

Ministry of Energy, Water Resources and Irrigation

Budhigandaki Hydropower Project

Environment, Compensation Distribution, Resettlement & Rehabilitation Unit

RCIDP

Salient Features

1. Reservoir
Full Supply Level (FSL) El. 540 masl
Maximum Flood Water Level El. 542 masl
Reservoir upper boundary incl. 3m freeboard El. 545 masl
Minimum Operating Level (MOL) El. 496 masl
Minimum Operating Level Ultimate (MOL.ult.) El. 467 masl
Minimum Reservoir Level (MRL) El. 440 masl
Reservoir Bottom Level El. 326 masl
Gross Capacity (at FSL) 4 467 Mm3
Active storage between FSL and MOL 2 226 Mm3
Reserve Live Storage between MOL and MOL.ult. 952 Mm3
Conservation volume between MOL.ult. and MRL 582 Mm3
Dead Storage between MRL and reservoir bottom 708 Mm3
Surface Area (at FSL) 63 km²
Surface Area (at MOL) 39 km2
2. Hydrology
Catchment Area 5 005 km2
Long Term Average Flow 222 m3/s (see note at the end of this table)
Construction Flood (20 years) 3 070 m3/s
Design Flood Discharge (10 000 years) 6 260 m3/s
GLOF 3 000 m3/s
LDOF 5 200 m3/s
Probable Maximum Flood 9 800 m3/s
3. Sedimentology
Sediment inflow 9.8 million m3/year
Active storage loss after 50 years 7%
Active storage loss after 100 years 13%
4. Diversion System
Design Flood 3 070 m3/s
Tunnel section, lining Horseshoe exc., inner circular concrete lining
Number of tunnel 2
Diameter 12 m
Lengths
DT N°1
DT N°2
 
408m
438m
Crest Elevation of U/S Cofferdam El. 357 masl
Crest Elevation of D/S Cofferdam El. 332.50 masl
5. Dam
Type Concrete double curvature arch
Crest Level El. 542masl + 1.1m u/s parapet
Maximum Height (above dam foundation) 263 m
Crest Length / Width at base/ at crest 760 m / 80m / 8m
Upstream and Downstream Slopes Variable
Construction materials:  
   Conventional Vibrated Concrete (CVC) 1.92 million m3
   Roller Compacted Concrete (RCC) 3.84 million m3
Total Concrete Volume 5.75 million m3
6. Spillway
Type Orifice gated spillway with flip bucket
Number of bays 6
Bay dimensions Width 5.6 m – Height 8.4 m
Crest Level 1 at El.515 masl / 2 at El.495 masl
2 at El.470 masl / 1 at El.460 masl
Design Flood (Routed) 6 280 m3/s for PMF,
4 690 m3/s for Q10000
Gate Type Radial gate with hydraulic hoists
Gate size 5.6 m x 8.4m, Six gates
7. Waterway and Powerhouse
Intake structures Bell mouth intake structures close to the dam on the left abutment
Total Rated discharge 6x112=672 m3/s
Number of intake 6
Invert Level of Intake El. 450masl
HRT invert level at El.455.60masl
Gate Size- Stoplog and wheelgate Span = 4 m / Height = 6m
Headrace Tunnel HRT:  
   Number of HRT 6
   Intake Tunnels Ø 6m
Concrete lined circular
107m Horseshoe Exc. Section
   Headrace Tunnels Ø 5.3m circular
Steel lined 22mm From 87m for Unit 6 to 165m for Unit 1
Horseshoe Exc. Section
   Pressure Shaft Ø 5.3m circular
Steel lined 28 to 45mm
140m high
Circular Section
   Penstock Ø 5.3m circular
Steel lined 45mm
From 352m (unit 6) to 365m (unit 1) Horseshoe Exc. Section
Powerhouse and transformer building Type: Outdoor in the left bank
Width, Length and Height W 40 m x L 185 m x H 40 m
GIS building and potyard Adjacent PH on platform at El.342
Width, Length and Height W 60 m x L 112 m x H 15 m
8. Generating Equipment
Turbine:  
Type Francis Type, vertical axis,
Number of units in final stage 6
Net Head at Rated Water Level 200 m
Rated Discharge in finale stage 6 x 112 = 672 m3/s
Installed Capacity 6 x 200 MW = 1 200 MW
Mean Annual Energy
(Generation Scenario N°1)
3 383 GWh (see note at the end of this table)
Winter dry season Energy
(Generation Scenario N°1)
1 408 GWh (see note at the end of this table)
Summer wet season Energy
(Generation Scenario N°1)
1 975 GWh (see note at the end of this table)
Firm Power during dry season from 1 200 MW 8h/day in Dec.
to 934 MW 9h/day May
Firm Power during wet season from 918 MW 7h/day in June.
to 928 MW 4h/day Nov.
Turbine Rated Speed 230.8 rpm
Normal Tailwater level with 6 units in operation El. 323.30 masl
Generator:  
   Type Vertical shaft revolving
   Capacity in final stage 6 x 235 MVA = 1 410 MVA
9. Transmission Lines
Number 2
Voltage 400 kV
Circuit Double circuit
Conductor Quad Bundle MOOSE
Length BG HPP to Naubise 40.3 km
Length BG HPP to Hetauda 58.7 km
10. Substations
Number 2
Location 1 in Naubise and 1 in Hetauda
11. Costs  
Total Capital cost
   Environmental and Social Cost
   Civil Works
   HEM and E&M
   HV lines
   Infrastructures and roads
   Engineering and Administration
2 593 MUSD
612 MUSD
1 265 MUSD
571 MUSD
33 MUSD
55 MUSD
57 MUSD
12. Economic & Financial parameters  
Economical Internal Rate of Return EIRR
Unchanged for Low, Medium and High load demand forecast (In nominal term)
Generation Sc N°1 Sc N°2
15.5% 16.9%
(See note at the end of this table)
Financial Internal Rate of Return FIRR
For medium demand forecast
Generation Sc N°1 Sc N°2
7.0% 8.6%
Average energy cost US¢ 6.4/kWh
Capital recovery period 11 years
Energy Tariff
For financing with
80% soft loan at 2% and 20% equity
100% Public Dev. and Return on Equity 10%: Mixed Public/Pvt Dev. and Return on Equity 20%:
Generation Sc N°1 Sc N°2 US¢/kWh 9 7
US¢/kWh 14.5 11.5
13. Benefits  
Energy sales from Budhi Gandaki HPP Downstream flood reduction
Downstream increase of mean dry season flow of
Naranyani river at Devghat and Gandak Barrage
see 12. Discharge +50% from Jan. To May
14. Manpower requirement  
Foreign
Skilled
Semi-skilled
Unskilled
Total (persons)
300
570
1 140
3 990
6 000

Note:
It is worth mentioning that the recent measurements made during the last five years (2010-2015) on the discharge of the Budhi Gandaki river at dam site and at the long term operated DHM gauging station in Arughat (since 1964) allowed to obtain a better relationship between the discharges at Arughat gauging station and those at the dam site (see also section 2.1).

The Consultant estimates that the river runoff at dam site is likely to be 26% higher than anticipated in the hydrological study of the Feasibility Report which has adopted a conservative approach in the transposition law between discharges measured at Arughat and those at the dam site since only few years of parallel measurements were available when editing the Feasibility Report.

This increase in the river runoff at dam site has a direct consequence on the BG HPP annual generation output called Generation Scenario N°2 which would be 26% higher i.e. reaching 4 250GWh per annum (1 620GWh in dry season or 10.8 GWh/day with guaranteed capacity of 970 to 1200 MW).

The Consultant considers that the 5 years parallel river discharge measurements Arughat-Dam Site are sufficient to have a reasonable degree of confidence in the new transposition law but recommends to continue the measurements at dam site to increase the data base and fully firm up the additional project generation potential.
(see also section 4.2 and 4.4 of this Volume 1 Main Report Ref BG-DDR-Vol 1 Rev0)