Study Report

(A)      Dam, Reservoir, Hydrology, Sedimentology, Spillways, Diversion and Outlet Structures

(a)	Main Dam and Reservoir
	Type of Dam	Concrete Face Rockfill Dam (CFRD)
	Dam Height (on foundation)	220 m
	Dam Body Volume	26.7 Mm3
	Dam Crest Elevation	648.0 masl
	Parapet Wall Top Elevation	649.5 masl
	Dam Crest Length	630.0 m
	Maximum Normal Water Level (Max. NWL)	640.0 masl
	Minimum Normal Water Level (Min. NWL)	530.0 masl
	Total Storage Capacity	1,581 Mm³
	Live Storage	1,342 Mm³
	Dead Storage	239 Mm³
(b)	Hydrology
	Catchment Area (at dam site)	3,857 km2
	Dudhkoshi River Average Flow	209 m3/s
	Construction Flood (50-year return period)	3,892 m3/s
	Design Flood (10,000-year return period)	9,027 m3/s
	Probable Maximum Flood (PMF)	12,638 m3/s
(c)	Sedimentology
	Total Sediment Annual Yield	8.82 Mm3/year (15 Mt/year)
	Total Sediment Volume after 50 years	441 Mm³
	Dead Storage Loss after 50 years	239 Mm³ (100%)
	Active Storage Loss after 50 years	202 Mm³ (15%)
	Average Annual Energy with Sedimentation (50 years)	3,331 GWh
	Average Dry Season Energy with Sedimentation (50 years)	1,204 GWh
	Average Wet Season Energy with Sedimentation (50 years)	2,127 GWh
(d)	Main Spillway
	(i) Gated Spillway
	Type	Concrete gated
	Design Discharge (10,000 year return period)	9,027 m³/s
	Sill Elevation	624.0 masl
	Crest Length	60.0 m
	Radial Gates	4 nos, 15.0 m x 20.6 m (width x height)
	(ii) Labyrinth Weir
	Type	Labyrinth Overflow
	Design Discharge	2,250 m³/s
	Crest Elevation	640.5 masl
	Length	56.55 m
(e)	Auxiliary/Emergency Spillway
	(i) Labyrinth Weir
	Type	Labyrinth Overflow
	Design Discharge	3,700 m³/s
	Crest Elevation	644.0 masl
	Length	154.5 m
	(ii) Embankment Dam
	Type	Embankment Fuse Dam
	Design Discharge	7,800 m³/s
	Crest Elevation	647.3 masl
	Bottom Elevation	637.0 masl
	Length	154.5 m
(f)	Diversion Tunnels (DT)
	Type and Number	Horseshoe-shaped, 2 nos
	Diameter (Excavation)	13.9 m (Finished Dia. 12 m)
	Lengths	DT1 = 1,115.2 m DT2 = 1,289.6 m
	Total Design Flow	3,892 m³/s (50 years return period)
(g)	Bottom Outlet (BO) (one of the Diversion Tunnels will serve as BO during operation)
	Type and Number	Horseshoe-shaped, 1 no
	Diameter (Excavation)	13.9 m
	Maximum Discharge	2,400 m³/s (120 m gross head)
(h)	Low Level Outlet (LLO)
	Type and Number	Horseshoe-shaped, 1 no
	Diameter (Excavation)	9.6 m
	Length	929.3 m
	Maximum Discharge	1,000 m³/s (120 m gross head)
(i)	Middle Level Outlet (MLO)
	Type and Number	Horseshoe-shaped, 1 no
	Diameter (Excavation)	10.5 m and 13.2 m
	Length	695.0 m
	Maximum Discharge	1,000 m³/s (90 m gross head)

(B)       Main Powerhouse

(a)	Headrace Tunnel
	Type	Circular shaped Concrete Lined
	Diameter (Excavation)	9.32 m (with TBM), Finished Dia. 8.3 m
	Length	13.2 km
	Design Discharge at Rated Head	224.4 m³/s
(b)	Surge Shaft
	Type and Number	Circular, 1 no
	Diameter (Excavation)	20 m
	Height	221 m
(c)	Steel Penstock
	Type and Number	Circular, 1 no
	Diameter (Internal)	6.7 m (3.2 m Dia. in bifurcation)
	Length	528.0 m
(d)	Vertical Penstock Shaft
	Type and Number	Circular, 1 no
	Diameter (Excavation)	8.5 m
	Length	180.0 m
(e)	Powerhouse
	Type	Underground Powerhouse
	Capacity	600 MW (4 x 150 MW)
	Turbine	Francis (Vertical Axis)
	Turbine Rated Head	294 m

(C)      Dam Toe Powerhouse

(a)	Headrace Tunnel
	Type	D-Shaped, Concrete Lined
	Diameter (Excavation)	8.0 m x 8.0 m
	Length	880
	Design Discharge at Rated Head	40 m³/s
(b)	Surge Shaft
	Number	Circular, 1 no
	Diameter	7.0 m
	Height	140.15 m
(c)	Steel Penstock
	Type and number	Circular, 1 no
	Diameter (Internal)	2.8 m
	Length	186.5 m
(d)	Vertical Penstock Shaft
	Type and number	Circular, 1 no
	Diameter (Excavation)	3.6 m
	Length	82.5 m
(e)	Powerhouse
	Type	Underground
	Capacity	70 MW (2 x 35 MW)
	Turbine	Francis (Vertical Axis)
	Turbine Rated Head	182 m

(D)      Transmission Line and Sub-Stations

(a)	Transmission Lines
	Type and Voltage	Double Circuit, 400 kV
	Conductor	ACSR Moose (Quad bundle per phase)
	Length from Main Powerhouse substation (Dhitung Substation) to Dhalkebar substation	82 km
	Length from Dam Toe substation to Bhadaure substation – LILO	1.6 km
(b)	Substation/ Switchyard
	Number	3 nos
	Location	one next to Main Powerhouse and the other two are located next to Dam Toe Powerhouse

(E)       Energy, Costs, Economical and Financial Analysis, Implementation Plan

(a)	Energy Production
	Average Annual energy Production	3,377 GWh
	Average Dry Season Energy Production	1,252 GWh
	Average Wet Season Energy Production	2,125 GWh
(b)	Costs
	Total Capital Costs	1,593 MUSD
(e)	Project Implementation
	Construction period	7 years