The Nalgad Hydropower Project is located on Nalgad in Jajarkot District in the Karnali Province of Nepal. Nalgad is one of the main tributaries of Bheri River. The project is a storage project with a 248 m high RCC dam. The storage creates a reservoir with total storage volume of 474 MCM and a live storage of 350 MCM. The main dam contains a spillway to pass a flood upto PMF, providing a crest width of 88 m. The dam site of the project is located just downstream of the confluence of Andheri Khola, which is approximately 9.25 km upstream from the confluence of the Nalgad and the BheriRiver and the powerhouse is located on the left bank of Nalgad River approximately 700 m upstream from the suspension bridge at Dalli.
The waterway consists of 8.168 km long concrete lined horseshoe shaped Head Race Tunnel of diameter 5.85m, a surge shaft of diameter 16 m and 165.50 m high, horizontal steel lined penstock tunnel of diameter 4.0 m and length 84.34m (excluding curve part), a 245.91 m and 338.26m long vertical drop shaft 1 and 2 respectively (including upper & lower curves) of diameter 4.0 m and a 907.32 m (horizontal between drop shaft 1 and 2) and 35 m long steel lined pressure tunnel of 4.0 m diameter horizontal bottom pressure tunnel. Two underground caverns for power station and transformer and GIS, housing 4 x 104.25MW Vertical Axis Pelton turbine and generator sets, with an installed capacity of 417 MW, utilizing a rated net head of 610 m and discharge 78.4 m³/s
Key Features of Nalgad Hydropower Project
|
Description |
|
|
Name of the Project |
Nalgad Hydropower Project |
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District |
Jajarkot |
|
Name of the River |
Nalgad River |
|
Types of Scheme |
Storage |
|
Project Road |
25 km |
|
Geology |
|
|
Dam Site |
Dolomite with frequent intercalation of black Shale |
|
Headrace Tunnel |
Limestone, Dolomite, and Shale |
|
Power station |
Sandstone |
|
Hydrology |
|
|
Catchment Area (up to Dam site) |
569 km² |
|
Average Precipitation |
2124 mm |
|
Average Monthly Flow |
28.67 m³/s |
|
Flood Discharge (1 in 20 years wet season) |
653 m³/s |
|
Flood Discharge (1 in 10,000 years wet season) |
1975 m³/s |
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Probable Maximum Flood (PMF) |
5051 m³/s |
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Sediment Yield |
1490 t/km²/year |
|
Diversion Tunnel |
|
|
Type, Shape |
Partially Lined, D Shaped |
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Diversion Flow |
560 m³/s |
|
Length |
374.30m |
|
Dimension |
6 m wide by 7 m high |
|
Reservoir |
|
|
Full Supply Level (FSL) |
1580 masl |
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Minimum Operating Level (MOL) |
1498 masl |
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Total Storage Volume |
474 million m³ |
|
Live Storage Volume |
350 million m³ |
|
Dam |
|
|
Type of Dam |
Curved Gravity Roller Compacted Concrete |
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Height above Foundation |
248 m |
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Crest Elevation |
1588 masl |
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Crest Wall Height |
1000 mm |
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Length of Crest |
495 m |
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Width of Crest |
10 m |
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Environmental In-stream flow release |
0.64 m³/s |
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Spillway |
|
|
Type |
Ogee shaped, non - gated overflow weir |
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Design flood |
1,000 yr peak inflow 1408 m³/s 10,000 yr peak inflow 1975 m³/s PMF peak inflow 5051 m³/s |
|
Overflow Crest Elevation |
EL. 1580 masl |
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Overflow Crest Width |
88 m |
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Main Intake |
|
|
Type |
Bellmouth |
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Invert Level |
1478.5 masl |
|
Intake Pipe |
1 no, 118.0m long, steel lined, circular shape |
|
Intake gates |
2 nos. 4.5 m x 3 m |
|
Stoplogs |
2 nos. 4.5 m x 3 m |
|
Headrace Tunnel |
|
|
Length |
8168.5 m |
|
Design Discharge |
78.4 m³/s |
|
Type |
Concrete lined Horse Shoe shape. |
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Finished Diameter |
5.85 m |
|
Surge shaft |
|
|
Type |
Restricted Orifice (Diameter = 3.0 m) |
|
Height |
165.5 m |
|
Diameter |
16.0 m |
|
Max Water Level |
1601.9 masl |
|
Min Water Level |
1466.8 masl |
|
Top Level |
1603.0 masl |
|
Invert Level (of tunnel below surge shaft) |
1437.50 masl |
|
Penstock (Top Horizontal) |
|
|
Shape |
Circular |
|
Type |
Steel lined |
|
Inclination |
Horizontal (excluding curve part) |
|
Length |
84.34 m |
|
Diameter |
4 m |
|
Vertical Drop Shaft-1 |
|
|
Shape |
Circular |
|
Type |
Steel lined |
|
Inclination |
Vertical (including upper and lower curve) |
|
Height |
245.91 m |
|
Diameter |
4 m |
|
Penstock Tunnel (Horizontal Between Drop shaft-1 & 2) |
|
|
Shape |
Circular |
|
Type |
Steel lined |
|
Inclination |
Horizontal |
|
Length |
907.32 m |
|
Diameter |
4 m |
|
Vertical Drop Shaft-2 |
|
|
Shape |
Circular |
|
Type |
Steel lined |
|
Inclination |
Vertical (including upper and lower curve) |
|
Height |
338.26 m |
|
Diameter |
4 m |
|
High pressure Tunnel |
|
|
Type |
Steel lined |
|
Length |
35m |
|
Finished Diameter |
4m |
|
Power Station |
|
|
Type |
Underground |
|
Size (L x W x H) |
110.9 m x 16 m x 37.5m |
|
Tailwater Level (turbine Pit) |
867.12 masl |
|
Transformer Cavern |
|
|
Type |
Underground |
|
Size |
111.2 m x 15.2 m x 20.4 m |
|
Turbine |
|
|
Turbine axis centre line elevation |
872.00m |
|
Type and No of Units |
Vertical Axis Pelton, 4 |
|
Installed capacity |
417 MW (4 x 104.25 MW) |
|
Tailrace Tunnel |
|
|
Type, Shape |
Concrete Lined, Inverted D-shaped |
|
Tail Water level at turbine pit |
867.12m |
|
Length |
520 m |
|
Excavation Size (W x H) |
7 m x 6 m |
|
Tailrace Canal (Cut and Cover) |
|
|
Shape |
Rectangular |
|
Type |
Concrete Box Culvert |
|
Length |
170 m |
|
Size (W x H) |
5.3 m x 4.3 m |
|
Tailwater Level at outlet |
862.00 masl |
|
Transmission Line |
|
|
Length |
112 km |
|
Voltage |
400 kV |
|
Circuit |
Double |
|
Interconnection Point |
Kohalpur S/S |
|
Power |
|
|
Maximum Gross Head |
708.0 m |
|
Design Net Head |
610.0 m |
|
Maximum Net Head |
692.0 m |
|
Minimum Net head |
610.0 m |
|
Design Discharge |
78.4 m3/sec |
|
Overall Efficiency |
87.80% |
|
Maximum Daily Generation |
9 equivalent hours |
|
Minimum Daily Generation |
1 equivalent hour |
|
Power Potential Studies |
|
|
Installed Capacity |
417 MW |
|
Annual Potential energy |
3655 GWh |
|
Firm Energy |
672 GWh |
|
Secondary Energy |
608 GWh |
|
Total Energy |
1280 GWh |
|
Average Annual Load Factor |
35.4% |
|
Dry Season Energy |
604.9 GWh |
|
Dry Season Load Factor |
33.4 % |
|
Opinion of Probable Construction Costs (OPCC) |
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Costing in Million USD (Exchange Rate = NRs 132.8 September 2023) |
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|
Item |
Description |
Option 1 - With Transmission Lines |
Option 2 - Without Transmission Lines |
|
|
1 |
Preliminary Works and Access Roads |
95.71 |
95.71 |
|
|
2 |
Civil Works |
664.78 |
664.78 |
|
|
3 |
Hydro-mechanical Works |
49.04 |
49.04 |
|
|
4 |
Electro-mechanical Works |
109.20 |
109.20 |
|
|
5 |
Transmission Line and Sub-Station |
85.93 |
- |
|
|
6 |
Running Sub Total (Base Cost) |
1,004.67 |
918.73 |
|
|
7 |
Allowances |
100.47 |
100.47 |
|
|
8 |
Running Sub Total (Item 6 + Item 7) |
1,105.13 |
1,019.20 |
|
|
9 |
Mark-ups |
128.01 |
128.01 |
|
|
10 |
Construction Cost (Item 8 + Item 9) |
1,233.15 |
1,147.22 |
|
|
11 |
Project Administration & Management |
160.66 |
160.66 |
|
|
12 |
Grand Total (Item 10 + Item 11) |
1,393.81 |
1,307.88 |
|