Nalsing Gad Storage Project

Salient Feature of the Project
Name of Project =Nalsing Gad Storage Project
District= Jajarkot
Location of project site=82°14’00″E-82°19’12”E
Longitude=28°47’28″N-28°58’00″N
Name of the River=Nalsyagu Gad River
Type of Scheme=Storage
Project Road= 25 KmGeologyDam Site= Dolomite with frequent intercalation of black Shale
Tunnel =Limestone, Dolomite and Shale
Powerhouse= Sandstone
Seismic Survey 58 Profiles – Total 8165 meter
Core Drilling 14 Holes – Total 602 Meter

Hydrology

Catchment Area (up to Dam site) =571.5 Km²
Average Precipitation =1718 mm
Average Monthly Flow =29.35 m³/s
Flood Discharge (1 in 20 year wet season)=675 m³/s
Flood Discharge (1 in 10,000 year wet season)= 2244 m³/s
Probable Maximum Flood (PMF)= 4488 m³/s
Sediment Yield =3960 t/km²/year

Diversion Tunnel

Shape= Circular Shaped
Type= Concrete Lined
Diameter=8.0 m
Length=1145

Reservoir

Full Supply Level (FSL)=1570 masl
Minimum Operating Level (MOL) =1498 masl
Total Storage volume=419.6 Million m³
Live Storage Volume= 296.3 Million m³

Dam

Type= Ogee shaped, non gated side channel
Maximum Height above Foundation=200m
Crest Elevation= 1580.30 masl
Length of Crest=545.00 m
Width of crest= 10 m

Spillway / Gated Spillway 

Type= Ogee Shaped ,open chute way with gate controlled weir, flip bucked and plunge Pool
Design Flood (1 in 1000 years)= 1510 m³/s
Overflow Crest Elevation= EL.1555.30
Effective overflow Width= 24m
Length of Spillway Chute= 420.00m
Length of Plunge Pool =170 m
Radial Gate (No. and W ×H)= 2 Nos. (12.0 m × 18.0m)

Side Spillway / Emergency Spillway

Type= ogee shaped, non gated side channel overflow weir
Design flood (1 in 1000 years)=1510 m³/s
Overflow Crest Elevation=EL.1555.30 masl
Effective overflow Width=120 m

Main Intake 

Type= Sloping
Deck Level =1575 masl
Intake Tunnel=1 No.
Invert level of intake=1481.0 masl
Intake Openings 6 Nos.(5.0m×3.5m)

Headrace Tunnel

Length=8215 m
Type= Concrete lined modified Horse Shoe
Finished Diameter=5.7 m

Surge Tank

Type =Restricted Orifice
Height=171.97 m
Diameter=12.0
Max Water Level=1607.30 masl
Min Water Level =1454.12 masl
Top level =1610.97 masl
Invert Level (of tunnel below surge tank)=1439.00 masl

Inclined Shaft

Shape =Circular
Inclination =60°
Height =564 m in two stages
Diameter =4.2 m
Length =900m

High Pressure Tunnel

Type= Steel Lined Penstock
Length= 90m
Finished Diameter= 3.9 m

Powerhouse

Type= Steel Line Penstock
Length= 90m
Finished Diameter= 3.9 m

Powerhouse

Type =Under Ground
Size (L× W ×H)= 106 m × 13m × 31 m
Tail Water Level (turbine pit)= 867.6 masl

Turbine

Type of Turbine= Vertical Axis Pelton Turbine
Number of Units =4 No
Turbine Centre line level= 872 masl
Installed Capacity= 410 MV (4× 102.5 MW)

Tailrace 

Shape= Inverted D shaped
Type =Concrete Lined
Size (W × H)=4.5 m × 3.5 m
Tail Water Level ( at outlet)=863.3 masl

Transmission Line

Length =112 km
Voltage =400k V
Circuit =Double
Interconnection Point=Kohalpur S/S

Power

Maximum Gross Head =698.0 m
Designed Net Head =635.5 m
Maximum Net Head =684.36m
Minimum Net Head =612.11m
Design Discharge =75.0 m³/s
Maximum Power Flow =77.92 m³/s
Overall Efficiency =87.80 %
Maximum Daily Generation=12 equivalent hrs
Minimum Daily Generation=2 equivalent hrs
Installed Capacity =410 MV

Energy

Dry Season Energy (November to April)=643.29 GWh
Wet Season Energy (May to October) =150.88 GWh
Spill Energy =611.89 GWh
Total Energy =1406.06 GWh
Regulated Energy=56.19%
Plant Factor (Spill Energy not Considered)= 22.11%
Discharge Utility Factor (Spill Energy not Considered)= 53.83%
Plan Factor (Inclusive of Spill Energy)= 39.15%
Discharge Utility Factor (Inclusive Of Spill Energy)=98.09%

Project Cost 

Total Project Cost (Base Cost)= 737.39 MUS$(2012 Price Level)
Local Component =157.75 MUS$(2012 Price Level)
Foreign Component =579.64 MUS$(2012 Price Level)
Installation Cost=1799 US$ per kW

Financial Indicators 

Total Project Cost (Base Cost)= NRs. 64153.19 Million (At exchange rate of NRs. 87.00)
Final Cost ) NRs. 108,263.74 Million
Total Debt =NRs. 26,665.66 Million
Interest Rate on Debt= 8.0%
Expected Return on Equity= NRs. 64153.19 Million (At exchange rate of NRs. 87.00)
Average Energy Cost (for 14% return on equity) Nrs. 9.11/KWH for Total Energy (2012 Price Level)
Average Energy Cost (for 14% return on equity ) NRs.16.09/KWh for saleable Energy (2012 Price Level)
Debt Service Ratio= 2.0 (in the First year of operation)
Financial Internal Rate of Return=8.9%
Benefit Cost Ratio= 1.15 (at 10 % discount rate)
Payback period =12.18 Year
Analysis Period =25 years

Economic Indicators (Based on Avoided Cost)

Economic Internal Rate of Return=21.88%
Benefit Cost Ratio=2.25 (at 10% discount rate)
Net present Value= 738.64 Million US$
Pay Back Period =12.18 Years
Specific Energy Cost for Hydro=16.31 US Cent/k Wh (at 10% discount rate)
Specific Energy Cost for Thermal =36.72 US cent/k Wh (at 10 % Discount rate)
Analysis Period= 25 years

Economic Indicators (Based on LRMC Cost) 

Winter Season Energy Rate= 12.72 US Cent per KWh
Summer Seasons Energy Rate= 3.82 US Cent per KWh
Emission Benefit =0.598 US Cent per kWh
Benefit Cost Ratio= 2.25 (at 10% discount rate)
Net Present Value= 76.57 Million US$ ( at 10% discount rate)

Environmental Impact Assessment (Based on Prefeasibility Study)

Relocation of Houses= 150
Inundation of Forestland= 270ha
Inundation Of Forestland= 290ha
Number of People Affected= 825
Environmental Cost= 11.81 MUS$

Reference:-http://www.nhpdc.gov.np/salient-feature.php

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One thought on “Nalsing Gad Storage Project

  1. The project is good & is effective to eradicate loadshedding of Nepal. But the main concern point is how long it will take time to go in construction phase & time of construction period.

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