Nalo - Ministry of Power

50 000 MW HYDROELECTRIC INITIATIVE
Government of India
Ministry of Power
Central Electricity Authority
360MW NALO H.E. PROJECT
ARUNACHAL PRADESH
Preliminary Feasibility Report
April 2004
Consultant :
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National Hydroelectric Power Corporation Ltd.
(A Government of India Enterprise)

PRELIMINARY FEASIBILITY REPORT
NALO H. E. PROJECT
(4 x 90 MW)
TABLE OF CONTENTS
(i)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
CHAPTER TITLE PAGE
I EXECUTIVE SUMMARY 1-11
II BACKGROUND INFORMATION 12-18
III PROJECT AREA 19-23
IV TOPOGRAPHIC & GEO- TECHNICAL
ASPECTS
24-30
V HYDROLOGY 31-49
VI CONCEPTUAL LAYOUT & PLANNING 50-63
VII POWER POTENTIAL STUDIES 64-92
VIII POWER EVACUATION 93-94
IX ENVIRONMENTAL ASPECTS 95-109
X INFRASTRUCTURE 110-113
XI CONSTRUCTION PLANNING &
SCHEDULE
114-119
XII COST ESTIMATES 120-149
XIII ECONOMIC EVALUATION 150-157
PLATES 158-173
ANNEXURES 174-253

LIST OF TABLES
(ii)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
CHAPTER TABLE TITLE PAGE
II 2.1 Power Supply Position of North Eastern Region 17
2.2 Power Supply Position of All India 18
III 3.1 Circle wise number of villages, household and
population in Upper Subansiri District as per
1991 Census
IV 4.1 Generalised Geological Succession 25
V 5.1 Data Availability status 38
5.2 Average Monthly Rainfall Near Nalo Sub-Basin 39
5.3 Flood Computed by various methods 46
VII 7.1 10- daily Discharge Data (cumecs) 69
7.2 90% Dependable Year Flows for Power
Generation
70
7.3 Summary Sheet 71
7.3A Availability of Units in KWH/KW for
Incremental Installation in 90% Dependable
Year
72
7.4 Power Potential in 90% Dependable Year with
95% m/c availability
73
7.5 Power Potential in 90% Dependable Year 74
IX 9.1 Landuse-landcover Information within the
Submergence Area
99
9.2 Landuse-landcover Information within the 7 km
Radius from the Dam site at Nalo
100
X 10.1 Status of Road Network Connecting Project site 111
XI 11.1 Construction Schedule of Nalo HE Project 119
XIII 13.1 IDC Calculation at Present Day Cost 153
13.2 Unit Cost of Energy at Bus Bar at Current Price
Level with 12 % Free Power to Home State
154
13.2 A Unit Cost of Energy at Bus Bar at Current Price
Level without Free Power to Home State
155
13.3 Calculation of Energy Rate with Present Day
Cost with 12 % Free Power to Home State
156
13.3 A Calculation of Energy Rate with Present Day
Cost without Free Power to Home State
157
22

CHAPTER PLATE
LIST OF PLATES
(iii)
TITLE
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
PAGE
II 2.1 Proposed Cascade Development over River
Subansiri
158
2.2 Vicinity Map 159
IV 4.1 Geological Plan 160
4.2 Geological X- section near Dam site 161
V 5.1 Catchment Plan of Subansiri Basin 162
5.2 Catchment Plan of Nalo HE Project 163
VI 6.1 General Layout Plan 164
6.2 General Layout - Longitudinal Section 165
6.3 Layout Plan- Dam area 166
6.4 Dam- Upstream Elevation 167
6.5 Dam- Cross Sections 168
6.6 Water Conductor System- Cross Sections 169
6.7 Layout Plan- Power House Area 170
6.8 Power House- Cross Section 171
VIII 8.1 Single Line Diagram – Power Evacuation 172
8.2 Subansiri Basin- Power Evacuation System 173

CHAPTER FIGURE
LIST OF FIGURES
(iv)
TITLE
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
PAGE
V 5.1 Reservoir Elevation-Area-Capacity Curve 49
LIST OF ANNEXURES
CHAPTER ANNEXURE TITLE PAGE
I 1.1 Salient Features
II 2.1 CEA’s letter regarding Preparation of PFR-
Replacement Schemes (dated 29.01.2004)
2.2 Record note of Discussion with CEA regarding
vetting of Layout (dated 24.02.2004)
2.3 Comments of HP&I Division, CEA vide
letter No. 7/9/NHPC/HP&I/2004/695 dated
05.04.2004 and Reply of NHPC.
IV 4.1 Preliminary Appraisal for PFR by Geological
Survey of India, New Delhi
V 5.1A Monthly Rainfall (mm) at Taliha 195
5.1B Monthly Rainfall (mm) at Siyum 196
5.1C
Monthly Rainfall (mm) at Limeking
197
5.1D
Monthly Rainfall (mm) at Nacho
5.2 Synthetic 10-Daily Flow Series at Menga
(NHPC)
5.3 Synthetic Average 10-Daily Discharge Series
at Dam Site
5.4 Observation of CWC Received vide letter No.
7/9/NHPC/2004/HP&I/1014 dated
13.05.2004 and Reply of NHPC.
174
177
179
181
186
198
199
201
203

(v)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
CHAPTER ANNEXURE TITLE PAGE
VI 6.1 Observation of CMDD Division, CEA vide
letter No. 7/9/NHPC/2003/HP&I/872 dated
21.04.2004 and Reply of NHPC.
6.2 Comments of HCD (E&NE) Division, CEA
vide letter No. 3/5/2000-HCD (E&NE)/875
dated 08/04/2004 and Reply of NHPC.
VII 7.1 Record note of Discussion with CEA
Regarding Vetting of Power Potential dated
16.03.2004.
7.2 Comments of SP&PA Division, CEA vide
letter No.-7/9/NHPC/2004/HP&I/892 dated
22.04.2004 and Reply of NHPC.
7.3 Comments of SP & PA Division on Cost
Aspects, CEA vide letter No. 7/1/2004/
SP&PA(C)/239 dated 13.05.2004 and Reply
of NHPC.
IX 9.1 Report from NRSA, Hyderabad on Satellite
Remote Sensing Based Inputs for Initial
Environmental Studies for Nalo Project Site
9.2 Excerpts from Preliminary Floristic Report of
Botanical Survey of India, Itanagar
9.3 Brief Report on Faunal Diversity of
Zoological Survey of India, Itanagar
9.4 Report of Fishery Department, Govt. of
Arunachal Pradesh.
210
215
218
220
229
233
249
250
253

1.0 INTRODUCTION
CHAPTER – I
EXECUTIVE SUMMARY
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Nalo H.E. Project is located in a remote area up-stream of Ledi Ishi Nallah
in Upper Subansiri District of Arunachal Pradesh. This project envisages
utilisation of water of river Subansiri (called Si Ngit in upper reaches).
Subansiri is a tributary of river Brahmaputra. Three scheme viz.,
Subansiri lower (2000 MW), Subansiri Middle (1600MW) and Subansiri
Upper (2000MW) have been planned to harness power potential of river
Subansiri. CEA has identified eight additional projects totalling about 4900
MW in Subansiri Basin (Arunachal Pradesh) in their ranking studies, as a
part of exercise for development of balance hydroelectric potential in the
country and accorded priority for preparation of Preliminary Feasibility
Report (PFR) so that these could be taken up for preparation of Detailed
Project Report (DPR) and further development during the XI and XII Five
Year Plans.
While preparing PFRs of Naba, Niare, Oju-II and Oju-I projects it was
noticed that about 300 m head between Naba and Subansiri Upper
Project is unutilised. In CEA’s Ranking study and Reassessment study
report there is no proposal to develop this head. Accordingly, it was
considered prudent to explore possibilities of exploring potential of the
river in this stretch between Naba and Ebiya villages. In this reach the
river travels about 31 km descending from EL 770 m to EL 470 m
providing a gross head of 300 m.
As gradient of river in this stretch is gentle, developing this head through
one scheme, would have involved construction of about a 25 km long HRT
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
as water conductor system. Hence, it was considered prudent to go for
two schemes in cascade. As a result, concept of Nalo and Dengser
projects emerged. Various alternative layouts were developed on
toposheets and proposed sites were inspected by NHPC officers. Based
on the data/ information collected during site visits and study of
topographical and geological inputs as collected, the parameters of Nalo
Project are proposed taking into account Naba HE Project on upstream
and Dengser HE Project on downstream. A few alternatives of scheme
were studied, discussed with CEA and it is proposed to have the dam site
where River Bed Level is 660 m, tail race outfall at EL 635 m and 2.5/2.6
km long head race tunnel as water conductor system. Installed capacity of
this project would be 360 MW ( 4x 90 MW).
1.1 GENERAL PROJECT FEATURES
The Nalo HE Project envisages construction of
River diversion works comprising of 2 nos of 10.75 m diameter
horseshoe shaped diversion tunnels with u/s and d/s cofferdams.
A 125 m high concrete gravity dam from deepest foundation level to
provide a gross storage of 163.37 mcm at FRL of EL 765 m and a
storage of 113 mcm at MDDL of EL 745 m .
Spillway comprising of (a) low level orifice spillway - 5 nos of opening
size 9.75 m X 11.5 m with crest elevation at EL 715 m and (b) upper
level crest type spillway - 2 nos of opening size 9.75 m X 11.5 m with
crest elevation at EL 753.5 m.
4 nos of Desilting chambers of size 300m (L) x 17m (W) x 25 m (H) to
remove silt particle of size 0.2 mm and above.
2 nos 2.5 / 2.6 km long 7.5 m diameter horseshoe shaped headrace
tunnels.
2

2 nos 90 m high 20 m diameter surge shaft.
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
2 nos 6.25 m diameter steel lined pressure shafts (vertical height 82m).
A surface power house with 4 units of 90 MW each
A tail race channel having bed width of 60 m.
The power generated from the project will be evacuated at 400 KV level
and will be pooled at Daporijo through one double circuit transmission line.
Daporijo pooling point will be ultimately linked through HVDC line to the
National Grid.
The salient features of the project are as under :
SALIENT FEATURES
LOCATION
State : Arunachal Pradesh
District : Upper Subansiri
River : Subansiri/Si Ngit
Dam site : 1.6 km u/s of Ledi Ishi Nallah
Nearest BG rail head : Nagaon
Nearest airport : Lilabari (North Lakhimpur)
HYDROLOGY
Catchment area
Location of catchment
: 14500 sq.km.
Latitude : 27 o 50’ N to 29 o 00’ N
Longitude : 91 o 45' E to 93 o 49' E
Average annual rainfall : 2810 mm
3

RESERVOIR
Full reservoir level (FRL) : EL 765 m
Min. Draw Down Level (MDDL)
Gross storage
: EL 745 m
-at FRL : 163.37 mcm
-at MDDL : 113 mcm
Area under submergence at FRL : 283.8 ha
DIVERSION TUNNEL
Number : 2
Size : 10.75 m
Shape : Horse shoe
Length : 650/800 m
Diversion capacity (assumed) : 2600 cumec
U/s coffer dam : 28 m
D/s coffer dam : 14 m
DAM
Type : Concrete
Top elevation of dam : EL 770 m
Height of dam above deepest
foundation level
: 125 m
Length of dam at top : 366 m
River Bed level : EL 660 m
SPILLWAY
Design flood : 12300 cumec
Lower spillway
Crest elevation : EL 715 m
Type : Orifice
Number : 5
Size of opening
: 9.75 m x11.5 m
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
4

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Upper spillway
Crest elevation : EL 753.5 m
Type : Crest
Number : 2
Size of opening : 9.75 m x 11.5 m
Energy dissipation : Ski jump with preformed plunge
pool
Length of spillway : 120 m
INTAKE
Invert level : EL 725 m
Number : 2
Size of gate opening : 7.5 m x 8.5 m
Trash rack : 18 m x 20 m
Intake tunnel : 8.5 m
Intake tunnel length : 250/350 m
DESILTING CHAMBERS
Number : 4
Size : 17 m x 25 m
Length : 300 m
Design discharge per chamber : 111.8 cum
Particle size to be removed : 0.2 mm and above
HEAD RACE TUNNEL
Number : 2
Size : 7.5 m
Shape : Horse shoe
Length : 2.5 /2.6 km
Design discharge per tunnel : 186.4 cumec
SURGE SHAFT
Number : 2
Size : 20 m
Height : 90 m
5

PRESSURE SHAFT
Number : 2
Size : 6.25 m
Vertical height : 82 m
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER HOUSE
Type : Surface
Installed capacity : 360 MW
Number of units : 4 ( 90 MW each )
Power house size
(machine hall + service bay)
: 103 (L)x 22 (W) x 47 (H)
Type of turbine : Vertical Shaft Francis
C.L of turbine : EL 633 m
Draft tube opening for each unit : 2 nos , 5 m (W) X 4.3 m (H)
Net Operating Head : 221 m
TAIL RACE CHANNEL
Bed Width : 60 m
Side Slope : 1V:1.5H
Length : 50 m
Design discharge : 372.8 cumec
River Bed level : EL 635 m
Maximum TWL : EL 645 m
SWITCH YARD
Size : 80m (W) X160m(L)
POWER GENERATED
Installed capacity
Annual energy generation
: 360 MW
in 90% dependable year : 1732.99 MU
6

1.2 STUDIES/INVESTIGATIONS UNDERTAKEN
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Study of topographic maps and remote sensing imageries.
Reconnaissance of area for identifying probable alternative
sites of project components.
Study of regional geotechnical features/ seismotectonic
aspects.
Geological appraisal of proposed project components.
Water availability/ design flood studies based on available
meteorological / hydrological data.
Conceptual layout and project planning.
Power potential studies.
Study of biotic environment, socio-economic environment for
prediction of environmental impacts of the project.
Study of existing infrastructure.
Cost benefit and Economic evaluation.
Geophysical investigations are not expected to provide reliable
results because of steep topography. Accordingly,
geophysical methods are not attempted.
1.3 RESULTS OF STUDIES AND INVESTIGATIONS
1.3.1 Geology
The entire project is located in broadly two rock types i.e. Biotite gneiss
and Biotite Schist. The dam site has been chosen in a relatively straight
stretch of the river where rock is exposed on left bank as steep rocky
7

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
escarpment but right bank is covered under overburden and vegetation.
From regional geological assessment it is expected that dam, diversion
tunnel & desilting chambers will be housed in biotite gneiss of Gelensiniak
formation whereas powerhouse complex and most of the part of HRT will
be housed in Biotite Schist of Nacho formation.
1.3.2 Hydrology
The river Subansiri/ Si Ngit drains a catchment area of about 14500 sq.
km at the proposed damsite. The water availability for the project has
been considered on the basis of 10-daily discharge series for 20 year
synthetic flow series at Subansiri Upper dam site, located d/s of this
project on the Subansiri river itself, on the basis of catchment proportion.
The computed inflow series worked out has been utilised for Power
Potential studies. The design flood is assessed as 12300 cumec at dam
site.
1.3.3 Infrastructure
In order to complete the project in 6 years, broad Infrastructure
requirements such as road network (including upgradation of roads)
project office, residential colonies, arrangement for construction power,
explosive magazine, telecommunication etc. have been identified and
provision has been made in the cost estimate of the project.
The project area is located in a remote corner of Arunachal Pradesh. It is
connected by a 410 km long single lane road from Pahumara in Assam
(take-off point from NH-52) to Nalo Project. Provision for
widening/strengthening of road sections /bridges has been kept in
estimates of hydroelectric projects viz., Subansiri Middle, Subansiri Upper,
and Dengser located downstream of this project. Cost of upgradation of
road for Dengser-Nalo segment has been kept in estimate of Nalo Project
8

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
to avoid duplication. Therefore, in case, Nalo H.E. Project is to be taken
up before construction of downstream projects, provision for R-
Communication in the estimate shall need to be revised, resulting in
higher tariff.
1.3.4 Power Potential Studies
The computed inflow series for 19 years has been considered in the
assessment of power benefits from the project.
The design energy for tariff at 95 % availability in a 90% dependable year
has been worked out 1732.99 MU.
A live storage of 50.37 mcm has been provided in the dam which would
enable the station to operate as peaking station. The live storage is
equivalent to 13511.70 MWh, which is sufficient to operate the station for
37.53 hour.
1.3.5 Power Evacuation Aspects
The power generated from the project would be evacuated at 400 KV level
through one number double circuit transmission line with Twin moose
conductor to pooling station proposed at Daporijo which in turn will be
connected to National Grid.
1.3.6 Environmental Aspects
The project is located in a remote area in the Subansiri Basin. To
appreciate landuse-landcover around the proposed project area, Initial
Environmental Studies have been carried out through National Remote
Sensing Agency (NRSA). The total land requirement for the construction
of various components is 740 ha. Out of which 285 ha. is private land
and remaining is forest land. Based on assessment of environmental
impacts, management plans have to be formulated for catchment area
treatment, Compensatory afforestation and other environmental issues.
9

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
These issues would be addressed during the investigation of DPR. No
major township will be submerged or affected due to construction of
project.
It is also stated that Ministry of Environment and Forest (MOEF) has
imposed a condition that “There would be no construction of dam
upstream of Subansiri river in future” while according clearance for
construction of Subansiri Lower HE Project. As this project is located
upstream of Subansiri Lower Project on Subansiri River, this condition is
required to be considered while taking up the project for preparation of
DPR.
1.3.7 Estimate of Cost
The project is estimated to cost Rs. 2609.66 crores excluding IDC at June,
2003 price level. The preliminary cost estimate of the project has been
prepared as per guidelines of CEA/CWC. The break up of the cost
estimate is given below:
Civil Works : Rs. 2212.47 Crores
Electro Mechanical Works : Rs. 334.89 Crores
Transmission Works : Rs. 62.31 Crores
Interest During Construction : Rs. 312.48 Crores
Grand Total : Rs.2922.14 Crores
1.3.8 Financial Aspects
The Nalo HE Project, with an estimated cost of Rs.2922.14 Crores
(including IDC of Rs.312.48 Cr) and design energy of 1732.99 MU in a
90% dependable year is proposed to be completed in 6 years. The tariff
has been worked out considering a debt-equity ratio of 70:30; 16% return
on equity, annual interest rate on loan at 10% and twelve percent free
power to home state. The tariff for first year and levellised tariff (with free
10

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
power to home state) is Rs.3.71 per unit and Rs.3.01 per unit respectively.
However, levellised tariff at present day cost without free power to home
state works out to be Rs.2.65 per unit.
1.3.9 Construction Schedule
The main infrastructure development is proposed to be initiated
simultaneously with preparation of DPR for which a provision of 18 months
will be kept in programme of stage-II activity and completed in initial 12
months after taking up construction (Stage-III activity) of the project. Main
construction activity is planned to be completed in 6 years.
1.4 CONCLUSION
Nalo HE Project works can be completed in 6 years. The project would
afford a design energy of 1732.99 MU in a 90% dependable year. The
tariff for first year and levellised tariff have been worked out as Rs.3.71 per
unit and Rs.3.01 per unit respectively (with provision of 12% free power to
home state).
The Preliminary Feasibility Report indicates that the scheme merits
consideration for taking up for survey and Investigation and preparation of
DPR. Nevertheless, it may be mentioned that MOEF has imposed ban
on construction of dam on Subansiri River upstream of Subansiri
Lower Project. Accordingly, matter needs to be taken up with MOEF for
review and lifting of ban before taking up investigation work leading to
preparation of DPR.
11

2.0 GENERAL
CHAPTER-II
BACKGROUND INFORMATION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Subansiri River is a major tributary of Brahmaputra contributing about 10%
of its total discharge. It has its origin in the Central Himalayas in Tibet at
an approximate altitude of 5340 m. Traversing through the snow clad
mountains of Great Himalayas, it enters India in its North-East corner in
Arunachal Pradesh. The river bed level drops from more than 4000 m
height in the mountainous region to less than 100 m in the foothills before
it enters the plains of Assam promising stupendous hydropower potential
with snowmelt combining with heavy rainfall it receives in its catchment
ensuring significant discharge in the river throughout the year.
2.1. PROPOSALS FOR HARNESSING HYDRO-POWER POTENTIAL
OF SUBANSIRI BASIN
To harness hydro-power potential of Subansiri river and to derive benefits
of flood moderation, DPR of Subansiri dam project (4800 MW) was
prepared by Brahmaputra Board during April 1983. But the project could
not be taken up for execution because of objections from Arunachal
Pradesh Govt. on account of large submergence of its land and
consequent displacement of inhabitants. Subsequently, cascade
development over river Subansiri was planned considering three projects
namely Subansiri Lower HE Project at Gerukamukh over river Subansiri
(2,000 MW), Subansiri Middle project at Tamen over river Kamla
(1,600 MW) and Subansiri Upper Project at Menga over river Subansiri
(2,000 MW).
12

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Subansiri Lower HE Project is now under construction by NHPC. The
feasibility reports of Subansiri Upper and Subansiri Middle project(s) have
already been prepared and detailed investigations leading to preparation
of DPR for these two projects are in progress.
In addition to the above 3 mega projects, 8 additional projects have been
taken up in Subansiri basin for preliminary feasibility study on priority basis
under “ 50,000 MW Hydro-electric Initiative ” launched by Hon’ble Prime
Minister of India launched in May, 2003. In fact, CEA has conducted
Ranking Study for harnessing the balance Hydropower potential available
in the country and identified 399 Schemes to add further 1,07,000 MW to
narrow the gap between supply and demand of power in the interest of
sustained economic growth of the country. In its first phase, 162 projects
are taken up for preliminary feasibility study to be completed within 10-18
months with a projected capacity addition of 50,560 MW. These projects
are expected to be developed expeditiously within next 10 years.
The eight new projects identified for preparation of PFR (Preliminary
Feasibility Report) in Subansiri basin under 50,000 MW Hydroelectric
Initiative were - Naba, Niare, Oju-I & II, Kurung - I & II , Hegio and
Duimukh.
Kurung-I & II projects have been clubbed and named as Kurung HE
Project. Further, Heigo project has been found to be located within
submergence of proposed Subansiri Middle Project. As such, in lieu of
these two projects, two schemes namely Nalo & Dengser located in
between Naba project and Subansiri Upper Project have been added to
list of PFR projects in Subansiri Basin (Annexure 2.1). Proposed cascade
development over river Subansiri is enclosed as Plate 2.1.
13

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Nalo HE Project is located at about 120 km upstream of Daporijo town in
Upper Subansiri District of Arunachal Pradesh. It has been envisaged as
a run-of-the-river Scheme on (Subansiri) river with generating capacity of
360 MW. Location of the project is indicated in the vicinity map enclosed
as Plate-2.2.
2.2 EVOLUTION OF CONCEPTUAL LAYOUT OF NALO HE SCHEME
While preparing PFRs of Naba, Niare, Oju-II and Oju-I projects it was
noticed that about 300 m head between Naba and Subansiri Upper
Project is unutilised. In CEA’s Ranking study or Reassessment study
report there is no proposal to develop this head. Accordingly, it was
considered prudent to explore possibilities of exploring potential of the
river in this stretch between Naba and Ebiya villages. In this reach the
river travels about 31 km descending from EL 770 m to EL 470 m
providing a gross head of 300 m.
As gradient of river in this stretch is gentle, developing this head through
one scheme, would have involved construction of about a 25 km long HRT
as water conductor system. Hence, it was considered prudent to go for
two schemes in cascade. As a result, concept of Nalo and Dengser
projects emerged. Various alternative layouts were developed on
toposheets and proposed sites were inspected by NHPC officers. Based
on the data/ information collected during site visits and study of
topographical and geological inputs as collected, the parameters of Nalo
Project are proposed taking into account Naba HE Project on upstream
and Dengser HE Project on downstream. A few alternatives of scheme
were studied and discussed with CEA and it is proposed to have the dam
site where River Bed Level is 660 m and tailrace outfall at EL 635 m.
Maximum TWL will be at EL 645 M. Summary record of the discussion
held with CEA is enclosed as Annexure –2.2. Further, details of various
14

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
alternative locations considered for finalising layout of Nalo HE Project are
given in chapter-VI.
Based on the limited available hydro meteorological data, hydrological
studies have been carried out and a synthetic 90 % dependable water
availability series developed for undertaking power potential studies. As
per power potential studies the installed capacity works out to 360 MW.
The design energy on a 90% dependable year works out to 1732.99 MU.
Preliminary observations and study of available information reveal that, no
major area of cultivable land is available around the proposed project area
needing irrigation. As such, there is no scope for development of irrigation
in this project. However, this aspect needs to be examined during
feasibility stage investigations.
PFR of Nalo HE Project has been made in accordance with the scope of
work and keeping in view observations/ comments of CEA (Annexure 2.3)
2.3 POWER SCENARIO & EXISTING INSTALLATIONS
The power system in India has grown from small, isolated stations, serving
limited consumers in and around large cities, into large regional Grids. The
generating capacity installed in the country has already grown to
107643.70 MW by March 2003.
The objective of the system development is to evolve self-sufficient
regional grid catering to the individual regional power demands. It is also
aimed at achieving the maximum benefits from integrated operation,
through a proper mix of thermal and hydro generation and ultimately to tie
the five regional grids together to form a robust National Power Grid,
providing even greater reliability.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
At present, Arunachal Pradesh Electricity Board has its own hydel
generation of 32.52 MW and diesel generation of 23.64 MW. Share of
Arunachal Pradesh in Central Sector Power Generation is around 117.0
MW (includes gas based Power projects).
2.4 NECESSITY OF THE PROJECT & RELATED ASPECTS
The power position in the North Eastern region and all India power supply
position have been summarized in Table-2.1 and Table-2.2. The benefits
from all schemes that have been cleared by CEA have been included.
Even after considering the co-ordinated operation of existing hydro,
nuclear and thermal stations as well as benefits from ongoing projects and
also from the scheme cleared by CEA and programmed for
implementation in 10th Plan, the all India regions are expected to face
power deficit in 10th five year plan. The regions will continue to remain in
deficit in 11th Five year plan also except in North-Eastern region as it is
evident from Table-2.1 even if all the cleared projects till date are
implemented. The surplus in North-Eastern region is planned to be
exported to regions having deficit. However, energy requirement and peak
requirement in the country will remain in deficit even by the end of 11 th
plan as shown in Table-2.2. Construction of Nalo HE Project will reduce
this deficit.
16

Table 2.1
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
17

Table 2.2
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
18

3.0 THE PROJECT
CHAPTER- III
PROJECT AREA
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Nalo HE Project is located in upper reaches of Subansiri River near
Nalo village. It is about 120 km from Daporijo town. Hydropower potential
of the river Subansiri is proposed to be harnessed through cascade of
several projects, viz.-Oju-I, Oju-II, Niare, Naba, Nalo, Dengser, Subansiri
Upper Project and Subansiri Lower Project. The proposed dam site of
Nalo project is accessible through Daporijo-Limeking road.
3.1 RIVER SYSTEM
River Subansiri originates in Tibet at an altitude of around 5340 m
beyond the Great Himalayan Range (Central Himalayas) and after
traversing about 375 km joins the Brahmaputra river. The river flows
through narrow gorge in most part of its length and generally follows an
easterly direction up to Siyum, and, thereafter it takes a south-easterly
course upto its confluence with Kamla. Then, it flows in a southerly
direction upto Kherkatiasuti and after flowing for another 60 km (approx.)
in south-westerly direction it confluences with the mighty Brahmaputra
River. It is one of the largest right bank tributary of Brahmaputra and
contributes about 10% of its total discharge. Major tributaries joining the
Subansiri river in the project area are Ledi Ishi, Kyo Ishi, Kodap & Kojap
nallah. These tributaries exhibit trellis and dendritic pattern of drainage.
Major villages/ towns located in the vicinity are Nalo, Jiba-Aying,
Doginalo & Nacho.
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3.2 LOCATION AND ACCESSIBILITY
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The project area is located near Nalo village. Powerhouse as well as
dam site can be accessed by all weather Daporijo- Limeking road
running on right bank of the river. The dam site of Nalo project is located
about 10 km upstream of Nacho. Major villages/towns present along the
Daporijo – Limeking road are Taliha, Kodak, Siyum, Ayingmoring, Nacho
& Limeking. Left bank of the river at proposed dam site can be
approached by a bamboo bridge located about 1 km upstream of dam
site. It is connected by a foot track. Proposed powerhouse site is located
on right bank of the river near Jiba-Aying village.
The nearest meter gauge and broadgauge railhead is North Lakhimpur
and Nagaon respectively. Nearest airport is at North Lakhimpur
(Lilabari) in Assam. Besides, there are helipads at Daporijo, Nacho,
Limeking near the project area.
3.3 CLIMATIC CONDITION
The area experiences a subtropical climate with temperatures ranging
from 11.5 0 to 39.5 0 C at Menga. However, from local enquiries it is learnt
that temperature falls to 0 0 C around the project area in winters. Ice-cold
winds blow during the morning and evening hours of the winter season.
Monsoon commences during May and lasts till the end of September.
Nevertheless, scanty rains are also common during winter season.
Average annual rainfall in and around project area is about 2810 mm.
The relative humidity as observed ranges from maximum 94% to
minimum 62%.
20

3.4 SOCIO- ECONOMIC ASPECTS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The project area is located in the Upper Subansiri District in Arunachal
Pradesh sharing the International Boundary with China in the North.
Upper catchment of Subansiri Basin in Indian territory falls in this district.
The area is inhabited mainly by the people from the Nyshis, Tagin
community, Galos and Hill Miris. The main livelihood of the population is
cultivation. They commonly practice terrace and jhoom cultivation.
3.4.1 Demography
The district is divided into 11(eleven) circles. The district has a diverse
terrain extending over valleys of lower altitude to heights upto 18000 ft.
Taksing is the remotest Circle bordering Tibet. It has snow bound peaks
where no habitation exists.
The Upper Subansiri District has an area of 7032 sqkm. The total
population of the district is 50,086 (1991 census). The population density
is approximately 8 persons per sq.km in the district. The male population
is 26,823 and the female population is 23,263. There is no educational
institution above higher secondary level. There are 3 nos. of Higher
Secondary Schools and 6 nos. of High Schools in the district. Population
of Nacho circle is 3404 persons where the project is located.
Circle wise population pattern of the Upper Subansiri District is
presented in tabulated form (Table 3.1) below.
21

Table 3.1
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Circle wise population in Upper Subansiri District as per 1991 census.
(Statistical Hand Book of Upper Subansiri District - 2000 )
Sl No. Name of Circles
Total No. of
Villages
Total No. of
House hold
Total
Population
01. Daporijo 56 2948 17425
02. Dumporijo 57 4299 7457
03. Baririjo 24 620 3292
04. Giba 62 980 5052
05. Taliha 89 1666 8057
06. Taksing 12 168 733
07. Nacho 42 827 3404
08. Limeking 18 209 863
09. Siyum 45 835 3803
Total 405 12552 50086
3.4.2 Ethnography
Race: The people of Arunachal Pradesh have been generally described
as descendants of Mongoloid, Paleo mongoloid and Proto-mongoloid
race. The distinctive characteristics of the tribes in their language, dress,
customs and food habits are direct reflection of the type of environment
they live in - in geographical isolation over a long period of time.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Tribes: The major tribes found in the project area belong to “Tagin”
community and “Nyishi”. These ethnic population usually live in different
groups called ‘busthi’ in the local language. Each ‘busthi’ generally
comprises of 15-25 homesteads. The houses (constructed of wood,
bamboo and thatches) are usually raised over a platform of logs about 3-
4 feet above the ground.
Social structure: The tribals of Arunachal Pradesh have highly ordered
and organised system of functioning in their villages. All matters relating
to the community as a whole are decided at the village level. The socioadministrative
structure of the society, as evolved over centuries,
recognises democratic participation right down to the village level.
Several self-governing institutions exist among these tribes. Such a
structure of ‘Nyshis’ in the area is locally known as ‘Nyele’.
Agriculture: Jhum cultivation is one of the predominant forms of
agriculture even today. Efforts are on to control this form of practice as
this results in cutting of forest trees & degradation of slopes. Most of the
people are dependent on agriculture. Only a few are working as traders,
daily wage labourers or salaried employees. Wet Rice Cultivation (WRC)
and Terrace Rice Cultivation (TRC) is also practiced in areas where flat
ground /river terraces are available.
Festival: Four main festivals are observed by the various communities
of the district. These are, (i) Si-Donyi, (ii) Boori-Yullo, (iii) Boori- Boot
and (iv) Mopin. The Tagin community celebrates the festival of Si-Donyi
in the month of January. Nyishis celebrates the Boori-Yullo festival
during the month of January. The Hill Miris community observes Boori-
Boot festival during the month of February. The Galo community
celebrates the Mopin festival during the month of April. There is another
festival known as Losar observed by the people of Taksing area in the
month of February.
23

CHAPTER-IV
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
TOPOGRAPHIC AND GEOTECHNICAL ASPECTS
4.0 INTRODUCTION
The Geological Survey of India has prepared a Preliminary Appraisal
Report entitled “Geology of Area Around the Proposed Nalo Hydroelectric
Project, Subansiri Basin, Arunachal Pradesh (March ’04)”. This appraisal
(Annexure 4.1) is the main source of geological inputs for evaluating
geotechnical aspects of the project. Nevertheless, proposed sites were
visited by NHPC geologists to collect site specific geotechnical details.
Topographic and geological aspects of the area have been used while
finalizing conceptual layout of the project (Plate-4.1).
4.1 REGIONAL TOPOGRAPHY AND GEOLOGY
The river Subansiri originates from Tibet and after traversing 375 km joins
the Brahmaputra River. At the project site river flows in an almost W-E
direction carving out a very narrow valley.
Project area in general is characterised by rugged topography typical of
Himalayan terrain. Geomorphologically, the area is composed of high
mountain ridges with steep slopes and deep incised valleys carved by
Subansiri river and perennial nallahs joining Subansiri river.
The Project area falls within higher Himalayas. At the proposed dam site
river valley is about 60 m wide with steep rocky slope at left bank and a
predominantly gentle slope on right bank. Right bank is covered by
overburden material and has a thick vegetation cover. Rock present at the
dam site is dark grey coloured slightly weathered to almost fresh biotite
gneiss. Geologists of G.S.I. (Surendra Singh, K.V.S Reddy, C.M.Bindal,
24

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
B.V.Ganesh and K.K. Rao, 1985-86) have carried out regional geological
mapping in this area.
4.2 REGIONAL GEOLOGY
The tectono-stratigraphic sequence of Upper Subansiri area as given
by Singh et al (1986) is reproduced below from GSI (March,2004) report.
(Table-4.1)
Table- 4.1
Generalised Geological Succession
Group Formation Litho-assemblages
S
U
B
A
N
S
I
R
I
G
R
O
U
P
Maza Granite Tourmaline leucogranite with biotite
gneiss and hornblende gneiss
Taksing Formation Schistose quartzite interbanded with
staurolite-garnet-biotite schists, calsilicate,
marble, meta-amphibolites
Gelensiniak Formation Kyanite-sillimanite-garnet gneiss,
migmatite gneiss, garnetiferous
biotite gneiss, biotite gneiss,
calc-silicate rock, marble with
graphitic
graphitic schists.
disseminations,
Nacho Formation Schistose Quartzite intercalated and
interbanded with biotite schist.
-----------------------------------------Kobaso Thrust-------------------------------------
Tali Massive quartzite, limestone/dolomite, phyllite and slate
Group
25

Maza Granites
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Tourmaline leucogranites, extensively exposed at Maza and further north
towards International Border with China have been designated as ‘Maza
Granites’. It is light grey fine grained and profusely jointed. Maza Granites
show hypidiomorphic granitar texure. Orthoclase, plagioclase and quartz
are its main mineral constituents. These are of intrusive igneous origin.
Taksing Formation
The metasedimentaries of Subansiri Valley constituting the Taksing
Formation are exposed in a NE-SW trending belt and are encountered
between Reddi and Taksing in Subansiri valley and also between Gelmo
and Ridding in the Tsari-Chu. White to light grey and fine quartzite
constitute the dominant lithounit of the Taksing Formation. Interbands of
staurolite – garnet –biotite- schist are common in the quartzite.
Gelensiniak Formation
The Gelensiniak Formation is most extensively developed in the
Subansiri Valley. Various types of gneisses belonging to this formation
are biotite gneiss, garnetiferrous biotite gneiss and kyanite- sillimanite
gneiss. These can be distinguished in the field on the basis of appearance
of index minerals such as Garnet, Kyanite, Sillimanite etc. Each type of
gneiss forms a distinct belt and have gradational contacts with one
another.
In the project area dark grey colured fine to medium grained well foliated
biotite gneiss is exposed.
Nacho Formation
It constitutes a litho-assemblage of white to light brown coloured
schistose-quartzite, intercalated as well as interbanded with dark biotite
schist. At Nacho the biotite schist bands show preponderence over the
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
quartzite. Further west dark grey biotite schist is well exposed. Near Dogi
Nalo, the Nacho Formation grades into overlying Gelensiniak Formation.
The quartzite, phyllite, limestone representing Tali Group are exposed
around Mara in southeastern corner. These are overridden by the medium
to high grade metamorphics and crystallines of the Subansiri Group along
the Kabaso Thrust.
4.3 TOPOGRAPHIC AND GEOTECHNICAL ASPECTS OF
COMPONENT STRUCTURES
To substantiate topographic/geological data, entire area has been
traversed and site specific information has been collected. A geological
section has been developed across the river near proposed dam site
(Plate-4.2), based on surface observations.
4.3.1 Dam
At the proposed site river flows through a wide valley. Width of the river
channel is about 60 m and width of the valley at the dam top is about 350
m. Left abutment is a steep rocky slope. Right abutment has a gentle
slope and is covered by overburden and thick vegetation. Nevertheless,
on right bank small rock outcrops are seen downstream of dam axis
indicating availability of rock at reasonable depth. Thickness of
overburden and quality of bedrock needs to be ascertained during
feasibility stage investigations. Dark grey coloured almost fresh to slightly
weathered biotite gneiss of Gelensiniak Formation is exposed in the
area. Rock is well foliated and moderate to closely jointed, dissected by
three to four prominent joint sets. Overburden on left abutment is very thin
but on right abutment it is comparatively thicker.
Depth of overburden in the river channel is not known at this stage. This
needs to be ascertained through exploratory drilling during feasibility /
DPR stage Investigations.
27

4.3.2 Water Conductor System
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Topography, geomorphology and geology are favorable for laying a tunnel
on the right bank. Proposed head race tunnel would be laid in puckered
biotite schist of Nacho Formation. However, intake tunnels and desilting
chambers will be housed in biotite gneiss of Gelensiniak Formation.
Engineering classification of rockmass expected to be negotiated in
various underground components of water conductor system needs to be
done during FR/DPR stage for estimating rock support requirement during
excavation.
4.3.3 Power House
The surface powerhouse is proposed on right bank of Subansiri river near
Jiba-Aying village. It will be located in moderate to closely jointed biotiteschist
belonging to Nacho Formation. Although, valley slope on right bank
are relatively gentler near proposed location, but some amount of slope
cutting will be required to create sufficient space for surface power house.
Therefore, depth of overburden and quality of bedrock at the back slope of
powerhouse needs to be studied during FR/DPR stage. If after detailed
study, surface powerhouse does not find favour option of underground
powerhouse may also be studied during FR/DPR stage.
Location of proposed surge shaft and pressure shaft needs to be studied
with a backup of detailed geological mapping and exploratory drilling/
drifting, during FR/DPR stage.
4.4 SEISMICITY
Seismotectonically, the area falls in the seismic zone –V of seismic zoning
map of India (IS-1893: Part- I :2002). Site specific design parameters need
to be worked out during Feasibility stage Investigations of the project.
28

4.5 CONSTRUCTION MATERIAL
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Subansiri River flows through a narrow valley. There are very few
river shoals or small terraces of riverine material, seen along course of the
river. Hence, very limited quantities of natural aggregates are expected to
be available from riverine shoals / terraces. Therefore, samples from rock
exposed around dam site and in reservoir area may be tested for using
this material as coarse and fine aggregates for production of concrete.
Biotite gneiss rock is present at dam site and upstream of it whereas
schistose quartzite intercalated with biotite schist is present downstream
of dam site. Desilting chambers and HRT would be laid in biotite gneiss
and biotite schist. Excavated rock from biotite gneiss is expected to be
useful as concrete aggregates (non- wearing surface only). Accordingly,
samples of rocks expected to be available in underground excavations
may also be tested during FR/DPR stage, if found suitable after testing.
Detailed construction material surveys may be conducted to identify
borrow areas and rock quarries. Quality and quantity of material for each
borrow area and rock quarry may also be ascertained during FR/DPR
stage investigations.
4.6 RECOMMENDATIONS
INVESTIGATIONS
FOR FURTHER STUDIES/
4.6.1 Topographic Surveys
- Detailed contour plans for Dam, Water Conductor System,
powerhouse and reservoir areas as per CWC guidelines.
- Cross- section of river at dam site and along other main
components of the project.
4.6.2 Geological Geotechnical Studies
- Detailed geological mapping of project components.
- Petrographic studies on rock samples.
29

- Rock mass classification for underground excavations.
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
- Drill holes and exploratory drifts at dam axis, water conductor
system and various components in the powerhouse area.
- Permeability / water pressure testing in drill holes.
- One or two sets of Groutability tests should also be done.
- Lab / In-situ rock mechanic testing for evaluation of physical
properties and engineering properties of the rock mass.
- Geophysical surveys for estimation of overburden at main civil
structures.
4.6.3 Remote Sensing Studies
- Regional geological appraisal of the area using remote sensing
data and aerial photographs.
- Preparation of lineament/ tectonic map of the area.
- Landuse classification using toposheets and Satellite imageries.
4.6.4 Construction Material Surveys
- Identification of borrow areas/ rock quarries.
- Survey of borrow areas / rock quarries for quantity estimation.
- Testing of representative samples for determination of physical
properties and alkali- aggregate reactivity potential.
30

5.0 GENERAL
CHAPTER – V
HYDROLOGY
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Nalo H.E. Project is proposed on river Subansiri a tributary of Brahmaputra
river, near Nalo village in Upper Subansiri district of Arunachal Pradesh.
The proposed dam site is located around 1.6 km upstream of confluence of
Ledi Ishi, with Subansiri, a right bank tributary of Subansiri river. The project
envisages construction of 125 m high dam above river bed on Singit or
Subansiri River with a gross storage capacity of 163.37 mcm at FRL i.e EL
765 m. The submergence area is estimated as 283.8 Ha at FRL whereas
the reservoir length is measured as around 9.7 km.
The hydrological investigations and analysis have been carried out with a
view to:
• Assess the availability of water for power generation by
establishing a long-term series of average 10-daily discharges
at the project site.
• Estimate the spillway design flood.
• Determine the capacity of the reservoir and the area of
submergence at different levels including FRL and MDDL.
• Reservoir Sedimentation
5.1 RIVER SYSTEM & BASIN CHARACTERISTICS
Subansiri is a major right bank tributary of river Brahmaputra. The river
originates beyond the Great Himalayan Range (Central Himalaya) at an
31

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
altitude of around 5340 m. Near its source, several mountain torrents,
rather a big “Chu” family of streams, drains into main valley. The principal
stream belonging to this “Chu” group is the Nye Chu which may be
considered as the main source of the river Subansiri originating from the
snow clad peaks of Krakang, Shabota, Baru and Mata (El 5389 m) lying
around 92 o and 93 o E longitudes and 28 o and 29 o N latitudes. The Nye Chu
is then joined by another stream Laro Chu near Chayal and thereby taking
the name of Chayal Chu. Another stream, the Char Chu, rising from the
snow clad peaks in the North joins the main stream Chyal Chu near
Karutra and crosses the international boundary soon after.
A small distance from the boundary, Yume Chu flowing from the north
merges with mainstream. After flowing further it receives the Tsari Chu and
the combined water of these streams flow as the Subansiri for about 200
km from this point finally outfalling into Kherkutia Suti, a spill channel of the
Brahmaputra. In higher reaches, where it is known as Tsari chu, the
Subansiri is flowing in an approximately easterly direction. The river cuts
across the central Himalayan ridge, which has a series of high peaks of
5000 m and above. It follows a Southeasterly course along the lesser
Himalayan zone with an average height of 3048 m and takes the name
Subansiri.
The river as it approaches the Miri hills in Arunachal Pradesh after crossing
the international boundary runs in an unexplored valley and the course of
the main river and its tributaries are more or less marked on conjectural
lines rather than by accurate mapping. In its early reaches as the river
gathers more and more torrents in the Himalayas, it rushes through deep
gorges, far below the snow tipped mountain peaks.
The main course of the Subansiri after entering the Miri hills in Arunachal
Pradesh runs between the Dafla hills and the Abor hills. Even in this reach,
very little is known of the river and its valley as it is covered with dense
32

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
vegetation and impenetrable forests. It is an enormous virgin terrain of
rugged mountains, covered by insatiable forest, fed by copious rains.
After traversing through the Miri Hills of the outer Himalaya (Siwalik
foothills), the Subansiri debouches into the plains of Assam near
Dulangmukh. Before entering the plains, Subansiri cuts a steep gorge of
unique beauty through the Siwalik rocks of Arunachal Himalaya.
Debouching from the hills near Dulangmukh the course of river lies in the
fertile plains of North Lakhimpur Civil Sub-Division of Assam. In the broad
and flat valley, the river flows in lazy and sinuous curves. The total length of
the river in the mountainous terrain is about 208 km. The riverbed falls from
a height of 4206 m to 80 m near Dulangmukh in the foothills. After flowing
for about 70 km from the hills, the river falls into the Kherkutia Suti and
thereafter flowing for another 60 km it outfalls into the river Brahmaputra.
Throughout its journey from the central Himalaya to the Arunachal foothills,
the Subansiri receives the discharges of numerous mountainous big and
small streams. The number of its tributaries is more in the Siwalik foothills
than in other zones. The total length of the known and well-defined
tributaries of Subansiri is 1960 km.
The region may be divided into four parts; the distant Tibetan mountains
beyond the international border, the reach lying between the international
boundary and Miri hills of Arunachal Pradesh, the Arunachal Pradesh
portion between the outskirt of Miri hills and the inter-state boundary of
Assam and Arunachal Pradesh and lastly the plains of Assam. The first two
belongs to the great Himalayan range, the third belonging to the Sub-
Himalayas and the fourth in the fertile plains of Assam.
Tibet, the birthplace of Subansiri is a land to conjure with. In the mountains,
blinding snow and ice build vast bewildering expanses. The streams flow
beneath the ice in winter, which have their turn in summer when they melt
and flow down the valleys lined up on either side with rows of white snow.
33

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
In this region are found towns, highly inaccessible in their mountain
retreats.
Down below in the region between the Miri hills of Arunachal Pradesh and
international boundary, the river passes through damp thick jungles and
rocky terrain.
The next reach is also in mountain terrain. These are the Sub-Himalayas,
the pattern of the hills and valleys being the same imposition of the
Himalayan range at a lower altitude. In the vastness of wild mountains,
there are unbelievable settlements of human habitation.
In the last lap of journey Subansiri passes through a broad fertile plain with
gentle slopes. Debouched from the narrow confines of the gorge, it spreads
and dissipates itself out in the plains of Lakhimpur District meandering and
altering channels of flow. The topography of this region is almost flat formed
of alluvial deposits. The river Subansiri in Arunachal Pradesh flows through
Upper and Subansiri Lower districts and in Assam its catchment area falls
in the North Lakhimpur and Dhemaji districts. The contribution of the river
Subansiri is estimated to be about 10.66 percent of the total discharge of
the river Brahmaputra at Pandu near Guwahati.
The snow line or limit of perpetual snow in the Himalaya varies depending
upon various local factors. The present snow line varies in altitude from
about 4267 m in the eastern part to about 5182 m in the western
Himalayas.
The catchment plan of Subansiri basin along with rainfall stations, G&D
sites marked is shown in Plate–5.1.
34

5.1.1 Catchment Area
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Nalo basin lies between Longitude 91 o 45′ E to 93 o 49′E and Latitude
27 o 50’ N to 29 o 00’ N. The proposed dam site lies at Longitude 93 o 46’54”E
and Latitude 28 o 24’27” N. The total catchment area up to the proposed dam
site is about 14500 sq.km. The permanent snow cover has been assumed
above an elevation of 4500 m. The snowfed area at proposed dam site has
been estimated as 9484 sq.km. The rainfed area upto the proposed dam
site is 5016 sq.km. The river bed level at the proposed dam site is around
EL 660 m. Average slope of river upto proposed dam site is estimated as
around 11 m per km.
The catchment plan of Subansiri Upper basin upto Nalo dam site is given in
Plate-5.2. This catchment plan has been prepared on the basis of
catchment plan prepared for the Subansiri basin by Brahmaputra Board and
then by NHPC. Toposheets of 1:50000 scale covering the catchment area
of the basin are not available and as most of the area falls in Tibetan
catchment, therefore it is difficult to collect them in feasibility stage also.
However, on availability of toposheets, the catchment plan need to be
verified in feasibility stage/DPR stage.
5.1.2 Temperature and Humidity
The climate in the entire region is humid and fairly uniform. Thick mist
formation from early morning everyday, which completely envelope the area
and blocks out the sun is generally, the climatic feature during winter. The
temperature varies from high altitude to lower altitude. The maximum and
minimum temperature is 39.5 o C and 11.5 o C as observed at Menga. The
relative humidity ranges from maximum 94% to minimum 62%.
35

5.1.3 Precipitation Characteristics
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Subansiri basin extends from tropical to temperate zones and therefore the
area exhibits a great diversity in rainfall characteristics. In the Northern and
Central Himalayan tracts precipitation is scarce on account of high altitudes.
Southeast part of the Subansiri basin comprising the sub-Himalayan and
the plain tract in Arunachal Pradesh and Assam, lies in the tropics.
Precipitation occurs in this region in copious quantities due to Northeast as
well as Southwest monsoon. Particularly the Southwest monsoon causes
very heavy precipitation in the whole of this region during May to October.
July and August are generally the high flood months.
The Eastern and Central Himalayas function as a great climate divide. In
winter, it serves as a barrier to the intense cold continental air flowing
southwards and in monsoon months, the moist rain bearing winds are
forced up the mountains to deposit their moisture.
The southwest monsoon, which enters Assam and adjoining area around
end of May and beginning of June establishes firmly over the entire North
East India by June end. During the monsoon season a low-pressure region
extends from the seasonal low over Rajasthan to the head of Bay of
Bengal. This monsoon axis oscillates about the normal position to the North
and South during the season. When it moves North towards the foothills of
Himalaya the rainfall over Assam increases and this is one of the primary
causes of flood in the Brahmaputra Valley. Sometimes a minor east west
oriented trough over Assam and West Bengal, while the primary trough is
along normal position, can also give rise to increased precipitation over the
Brahmaputra catchment. Land based low and depressions form in situ over
Assam and adjoining region or move across Bangladesh and influence in
increasing the precipitation over the various reaches of Brahmaputra Valley.
36

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The other features that normally cause increased precipitation over the
Brahmaputra basin are passage of upper air trough in the monsoon
westerlies and sometimes by the appearance of the remnants of mid
latitude western disturbances over extreme North Arunachal Pradesh in
conjunction with other precipitation causing features.
The above account of weather and precipitation distribution is influenced by
local orographic effects, with minor ranges, spurs, valleys of different width
and narrow gaps permitting winds to enter from particular direction, in the
sheltered valleys. The orography of the catchment is so complex that a
detailed study would be possible only with a dense network of
observatories.
The other meteorological situation causing very heavy rainfall is the
passage of cyclonic storms, originating in Bay of Bengal, over the area.
This is generally noted in late May or June and in late September or
October, when the cyclonic storm developing over the Bay initially moves
towards approximately 20 o N.
The raingauge network in Subansiri Upper basin is not as per desired
standards. No raingauge station is available within the catchment of Nalo
H.E. Project. NHPC has established rain gauge stations at Taliha, Siyum,
Menga, Daporijo, Dumporijo, Nacho and Limeking in respect of Subansiri
Upper Project. Out of these raingauge stations namely Taliha, Siyum,
Nacho and Limeking lies near Nalo dam site, though outside the catchment
of Nalo. Data Availability status of raingauge stations near Nalo is placed
as Table 5.1.
37

TABLE-5.1
DATA AVAILABILITY STATUS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
------------------------------------------------------------------------------------------------
S.No STATION DATA AVAILABLE
------------------------------------------------------------------------------------------------
1. Taliha 1968-69,76-86,2000-2003
2. Limeking 1966,68-69,77-80,2001-2002
3. Siyum 1966,68-69,2001-2002
4. Nacho 2001-2003
------------------------------------------------------------------------------------------------
The rainfall data is not continuous and missing in between prior to year
2000. Further, it is not truly representative of entire basin. The raingauge
stations could not be established due to inaccessibility and poor
infrastructure of this region. Also most of the portion of this basin falls in
Tibet. Monthly rainfall at all four stations for each year is given as
Annexure 5.1A, 5.1B, 5.1C and 5.1D. Average monthly rainfall in near the
catchment of proposed project is shown in Table –5.2. The average annual
rainfall in the vicinity of the Nalo sub-basin is around 2810 mm.
38

TABLE- 5.2
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
AVERAGE MONTHLY RAINFALL NEAR NALO SUB-BASIN
MONTH TALIHA LIMEKING SIYUM NACHO AVERAGE
JAN 62.5 111.8 40.2 22.5 59.2
FEB 116.1 79.0 83.0 59.3 84.3
MAR 186.2 174.5 193.3 138.7 173.2
APR 283.7 199.9 232.3 173.1 222.3
MAY 286.5 384.0 297.3 283.6 312.8
JUN 315.5 537.2 573.0 582.4 502.0
JUL 373.3 488.5 483.8 425.6 442.8
AUG 281.0 444.0 392.5 473.5 397.8
SEP 294.3 384.8 358.7 425.0 365.7
OCT 123.7 186.5 189.1 117.8 154.3
NOV 66.7 44.6 97.7 45.4 63.6
DEC 49.3 40.2 20.0 17.8 31.8
TOTAL 2438.8 3074.8 2960.9 2764.6 2809.8
39

5.2 WATER AVAILABILITY STUDY
5.2.1 Data Available
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Gauge and discharge data is not available anywhere in the catchment of
Nalo H.E. Project. Due to difficult condition of communication, accessibility
and terrain, despite continuous efforts, much information about the
discharge pattern in the catchment of proposed project could not be
obtained. On the basis of available data and information the study has been
made. However, few G&D sites has been established by various agencies
within the Subansiri basin as detailed below.
Brahmaputra Flood Control Commission (BFCC)/ Brahmaputra Board
established a gauge discharge site at Daporijo 25 km d/s of Subansiri
Upper dam site in 1978. The gauge and discharge Station at Bhimparaghat
located 15 km downstream of the Subansiri Lower dam site was
established by Central water Commission in 1956, which was subsequently
shifted, to Chouldhowaghat in 1960 located 12 km downstream of the
Subansiri Lower dam site. In 1971 the site was taken over by B.F.C.C.,
Govt. of Assam. The gauge discharge site at Gorge Mouth was established
in July 1973 located 2 km down stream of Subansiri Lower dam site, which
was subsequently shifted to Subansiri Lower dam site in August 1977. A
G&D site was established at Tamen on Kamla River, where gauge and
discharge data is available from 1980 to 1998.
NHPC has established G&D sites at Menga (260 m u/s of proposed dam
site, operational since June 2000), Tamen Bridge (3 km d/s of Subansiri
Middle dam site, operational since June 2000), Deo Nallah (situated at
around 300 m d/s of Subansiri Lower dam site, operational since October
2000) and Chouldhowaghat (operational since December 2000). A G&D
site has also been established on Pein River, which joins Kamla near
Tamen Bridge. A gauge site is at Ferryghat, which is around 1.9 km d/s of
40

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
proposed Subansiri Lower dam site. At present, floats are being used to
measure the velocity. Current meters are also used mainly in lean season.
5.2.2 Methodology
The following methodology thought up to apply to obtain water availability
series at proposed dam site.
5.2.2.1 Rainfall Runoff Relationship
First option is to generate discharge series on the basis of rainfall data
available in the basin. A rainfall-runoff regression analysis could be
performed in Nalo basin and the relationship so developed could be used to
compute the discharge at proposed dam site. However this could not be
done due to non-availability of discharge as well as rainfall for Nalo sub
basin. A runoff factor of 0.73 had been established after detailed rainfallrunoff
analysis in Subansiri basin as discussed in feasibility report of
Subansiri Upper Project. This factor could be used to compute runoff from
rainfall. This methodology could also not be adopted because of the nonavailability
of discharge and rainfall data within the Nalo sub-basin.
5.2.2.2 Based on Discharge Series at Subansiri Upper Dam site
Water availability study in Subansiri at Menga had been performed
considering entire Subansiri river system as one, so as to maintain
consistency in the flow at all the observation sites. After detailed analysis a
20-year synthetic flow series (enclosed as Annexure-5.2) had been
obtained at Subansiri Upper dam site (CA=20250 sq.km, Rainfed=9564
sq.km). This synthetically generated 20 years discharge series at Subansiri
Upper dam site may be transferred to Nalo dam site on the basis of
Catchment proportion considering the two basins as hydro-meteorologically
homogeneous. The catchment correction factor has been worked out as
0.524.
41

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
For the present, the second methodology (catchment proportion) has been
adopted. The discharge series so obtained has been checked for the
consistency with the rainfall data available near Nalo basin. The runoff
factor thus worked out as 0.72. However, this factor has been computed
based on non-concurrent data base, therefore, detailed analysis need be
done on availability of concurrent rainfall-runoff within the basin.
The average 10 daily flow series at proposed dam site has been placed as
Annexure-5.3. Average annual yield of at proposed dam site has been
worked out as 10167 mcm.
After establishing gauging station near proposed dam site with proper
raingauge network in Subansiri Upper basin, detailed water availability
study need be conducted in feasibility stage/DPR stage.
5.3 RESERVOIR ELEVATION AREA CAPACITY CURVE
The reservoir elevation-area-capacity curve at proposed dam site has been
obtained on the basis of 1:50000 scale toposheets at 40 m contour interval.
Area under various contours at 40 m interval has been measured from the
elevation of 660 m to 800 m. The volume between any two elevations is
calculated using the conical formula :
Where
V = (A1+A2+√A1A2)*H/3
V = The volume between two contours
H = Contour interval
A1 = Area at level of first contour
A2 = Area at level of second contour
42

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The incremental volumes thus obtained are added to obtain cumulative
volume. The reservoir elevation-area-capacity curve at proposed dam site
is given in Figure-5.1. This curve is subject to modification after availability
of reservoir cross-sections or 1:15000 scale contour maps for the
catchment.
5.4 DESIGN FLOOD
Design Flood for a project can be estimated by following approaches:
(i) Deterministic approach using Unit Hydrograph technique.
(ii) Statistical approach using Flood frequency analysis
(iii) Empirical methods
(i) Deterministic Approach Using Unit Hydrograph Technique
Due to non-availability of G&D data, short term rainfall, hourly gauges
etc, design storm values in the proposed catchment, rating curves
and observed flood hydrographs could not be obtained for computing
the Unit Hydrograph and Design Flood hydrograph. However, this
approach has been used partially while transferring the flood of
Subansiri Upper dam site to the proposed dam site.
(ii) Statistical Approach Using Flood Frequency Analysis
Due to non-availability of long term, consistent G&D data near the
proposed scheme, flood frequency analysis could not be performed
at the project site.
43

(iii) Empirical Methods
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The following empirical relationships have been used to estimate the
design flood peak:
• Dicken’s Formula
Q = CA 3/4
Where,
C = Dickens constant with value between 11-14 for North-
Indian Hilly catchment. A value of 14 has been
adopted in present study.
A = Catchment area in sq.km
Therefore
Q = 14 x 5016 3/4
= 8344 cumec
• Fuller’s Formula
Qmax = C.A 0.8 (1+0.8logT)*(1+2.66A -0.3 )
Where,
C = constant varying between 0.026 to 2.77 (2 adopted)
Qmax = Maximum 24-h flood with a frequency of T years in
cumec
A = Catchment Area in sq.km
1000 year Flood
Q1000 =2 * 5016 0.8 (1+0.8log(1000))*(1+2.66*5016 -0.3 )
= 7487 cumec
44

• Ali Nawaz Jung Formula
Q = C(0.386A) (0.925-1/14log0.386A)
Where
C = 49 to 60 (55 adopted)
Q = 55* (0.386*5016) (0.925-1/14log(0.386*5016))
= 10211 cumec
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
• Transferring design flood at Subansiri Upper dam site
on the basis of Dickens formula.
1-Day and 2-day PMF of 12226 cumec and 15210 cumec
has been estimated at Subansiri Upper dam site
(CA=20250 sq.km, Rainfed Area = 9564 sq.km). A base
flow (including snow melt) of 3000 cumec had been
assumed during computation of design flood by
deterministic approach. The Nalo H.E. Project is located
upstream of this dam site. Catchments of both the projects
can be considered as hydro-meteorologically
homogeneous. Therefore, it seems logical to transpose the
design flood value of Subansiri Upper dam site to
proposed dam site. This transposition has been done by
Dicken’s formula using a conversion factor of 0.616 at
proposed dam site. The design flood based on 1-day PMF
and 2-day PMF at Subansiri Upper dam site thus
computed as 10535 cumec and 12374 cumec respectively.
A comparative study of flood peak computed by various methods is placed
as Table-5.3.
45

TABLE- 5.3
FLOOD COMPUTED BY VARIOUS METHODS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S.No. Method Flood Peak (cumec)
1 Dickens Formula 8344
2 Fuller’s Formula 7487
3 Ali Nawaz Jung Formula 10211
4 Transposition of 2-day PMF on the
basis of Dickens formula.
5 Transposition of 1-day PMF on the
basis of Dickens formula.
12374
10535
Based on above mentioned studies summarized in Table-5.3, for prefeasibility
stage study, a design flood of 12300 cumec at dam site of the
proposed project has been recommended.
It is worth mentioning here that although deterministic approach of design
flood computation has not been used in the present study for Nalo sub
basin, however, this approach has been used partially, as the design flood
at Subansiri Upper dam site had been computed by this method only. The
detail of design flood study may be referred in feasibility report of Subansiri
Upper Project.
On availability of more data/information, design flood need be estimated by
deterministic approach using unit hydrograph technique and probabilistic
approach using flood frequency analysis in feasibility stage/DPR stage.
46

5.5 RESERVOIR SEDIMENTATION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
As per compendium on silting of reservoirs in India, the sediment rate
varies from 0.05658 to 0.2785 Ham/Sq.km/year for Indus, Ganga and
Brahmaputra basin.
An attempt has been made for an approximate assessment based on
sediment yield rate of some of the North bank tributaries, which are flowing
through Arunachal Pradesh and where sediment rates were earlier worked
out for designing respective projects. All these tributaries have nearly
similar topographical, physiographical, geological and soil vegetation cover
characteristics. The values worked out are as below (Including bed load):
(a) River Siang at Passighat =0.055 ham/sq.km/year
(b) River Ranganadi at Yazali Dam site =0.074 ham/sq.km/year
(c) River Debang at Munli dam site =0.100 ham/sq.km/year
(adopted value)
(d) River Subansiri At Chouldhowaghat =0.057 ham/sq.km/year
(e) River Lohit at Mompani =0.011 ham/sq.km/year
(f) River Lohit at Digerighat =0.235 ham/sq.km/year
Considering all the above, for the present, a silt rate of 0.057
ham/sq.km/year as calculated at Chouldhowaghat on Subansiri river may
be adopted at the proposed dam site of Nalo H.E. Scheme.
Detailed reservoir sedimentation study needs be done during feasibility
stage with more observed data at the proposed site using a suitable
method.
47

5.6 RECOMMENDATIONS FOR FUTURE STUDIES
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The following are the improvements suggested for feasibility/DPR stage
study:
• Proper raingauge network along with Gauge-discharge-sediment
observation sites on Subansiri river near proposed dam site need
be established before taking up preparation of feasibility report
/DPR.
• After establishing gauge and discharge site on Subansiri river
with proper raingauge network in Subansiri Upper basin, detailed
water availability study need be conducted in feasibility/DPR
stage.
• The reservoir elevation-area-capacity curve need be revised after
availability of reservoir cross-sections or 1:15000 scale contour
maps in feasibility/DPR stage study.
• On availability of more data/information, design flood need be
estimated by deterministic approach using unit hydrograph
technique and probabilistic approach using flood frequency
analysis in feasibility/DPR stage.
• Detailed reservoir sedimentation study need be done during
feasibility/DPR stage with observed data on Subansiri river at the
proposed dam site using a suitable method.
The observations of CWC along with reply of NHPC have been
enclosed as Annexure 5.4 and need to be referred during feasibility/
DPR stage.
48

Elevation
(metre)
Reservoir
Area (ha)
Reservoir
Capacity
(Mcum)
660 0.00 0.00
680 79.18 5.28
720 185.78 56.78
760 266.96 146.84
800 401.36 279.59
-----> Elevation (m)
Figure 5.1
RESERVOIR ELEVATION AREA CAPACITY CURVE
800
780
760
740
720
700
680
280
260
240
Capacity
Curve
220
200
180
Area (Ha)
120
Area Curve
100
Note : This curve is prepared from 1:50000 scale
toposheets and is applicable for pre-feasibility stage only.
80
60
40
20
0
800
780
760
740
720
700
680
49
-----> Elevation (m)

CHAPTER-VI
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
CONCEPTUAL LAYOUT & PLANNING
6.1 FINALIZATION OF CONCEPTUAL LAYOUT
6.1.1 General
Nalo and Dengser HE Projects are replacement Schemes in Subansiri
Basin to exploit unutilized the head available between Naba and Upper
Subansiri HE schemes and cover shortfall in the number of schemes
allocated to NHPC, due to,- a) Combining of Kurung stage-I and Kurung
stage-II HE Projects and b) Hegio HE Scheme (Annexure 2.1).
6.1.2 NHPC PROPOSAL
Based on the topographical input (SOI Toposheet No. 82 H/15 in 1 in
50,000 Scale), the NHPC had developed certain layouts. These were also
examined in the field. Based on topography, geology and parameters of u/s
and d/s projects in the cascade, layout of Nalo H.E. Project has been
finalised. It is proposed to locate diversion structure on river Subansiri
where the river bed level is EL 660 m with FRL at EL 765 m. NHPC has
been advised to keep the FRL of the scheme taking into account the tail
water level of the upstream Naba HE Project. River bed level at power
house site (tailrace outfall) of Nalo HE scheme has been proposed as
EL635 m, keeping in view the FRL of the downstream project i.e. Dengser
HE Project (EL 630 m). The length of water conductor system would be
3.75 km. Conceptual layout of the project proposed by NHPC was vetted by
CEA (Annexure 2.2) and NHPC has been advised to proceed with
preparation of PFR of Nalo HE Project as proposed by them.
50

ALTERNATIVE STUDIES
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Subsequent to vetting of project parameters by CEA, the project layout/
parameters have been finalized considering the proposed Naba HE Project
located on upstream and Dengser HE Project located in downstream as a
part of the cascade development over river Subansiri.
a) Location of Dam axis
Alternative dam site namely alternative-1, alternative-2 and alternative-3
located 3.1 km d/s, 0.8 km d/s and 1.6 km u/s of Ledi Ishi nallah have been
considered (location as indicated on Plate 6.1). At these locations the river
bed level is about EL625 m, EL642 m and EL 660 m respectively. Taking
into account topographical, geological conditions and layout of the project,
the dam axis (alt- 3) prima facie has been found to be preferable and as
such adopted for PFR preparation. Needless to mention that during detailed
investigation for DPR preparation location of dam axis shall need to be
reviewed.
b) Location of Power house and layout of water conductor system
Alternative of laying water conductor system on left as well as right bank of
the river were examined. The length of water conductor system on left
bank works out to be slightly less, in comparison to its length on right bank.
However, the existing approach road to project is on right bank.
Accordingly, water conductor system is laid on right bank to facilitate taking
up of construction activity.
As per topography from SOI Toposheet No. 82 H/15 (1 in 50,000 Scale)
surface power house has been proposed. However, it may be mentioned
that based on the topographical and geological data collected during
feasibility /DPR stage, if required, above arrangements shall be reviewed.
51

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Based on topographical details (SOI toposheet no.82 H/15 in 1 in 50,000
scale) and geological details project layout has been developed.
Various components of the project are:
a) River diversion works comprising of 2 nos 10.75 m diameter
horseshoe shaped diversion tunnel with u/s and d/s cofferdams.
b) Concrete gravity dam.
c) Water conductor system consisting of
i) Intake structure
ii) 4 nos 300m x 17m x 25m Desilting chamber.
iii) 2 nos 7.5 m diameter horseshoe shaped Head Race
Tunnel.
iv) 2 nos 20 m diameter Surge Shaft.
v) 2 nos 6.25 m diameter steel lined Pressure Shaft each
feeding two units.
vi) 60 m wide Tailrace channel.
d) Surface power house.
e) Switch yard 80 m x 160 m.
Proposed General Layout plan and Longitudinal section through water
conductor system is enclosed as Plate-6.1 & Plate-6.2 respectively.
52

6.2 PRELIMINARY DESIGN FEATURES
6.2.1 River Diversion Works
6.2.1.1 Diversion Tunnel
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
No G&D data for river Subansiri near proposed dam site is available.
Keeping in view the hydrological studies as carried out for Subansiri Upper
HE Project the diversion tunnel shall be designed for passing an assumed
diversion discharge (non monsoon period) of 2600 cumec. For the
construction of dam and appurtenant works, the river diversion is proposed
to be carried out through 2 nos. of 10.75 m diameter concrete lined,
horseshoe shaped diversion tunnel located on the left bank of the river. The
length of diversion tunnels shall be about 650/800 m.
6.2.1.2 Coffer Dam
To facilitate river diversion, upstream and downstream cofferdams with a
central impervious core shall be provided. These coffer dams shall be
located about 100 m u/s and 250 m d/s of the proposed dam axis. The
height of u/s and d/s coffer dams shall be 28 m and 14 m respectively. As
the diversion scheme has been designed to cater for non-monsoon flood,
cofferdams may get damaged during monsoon period and as such, shall
require rebuilding before undertaking works in subsequent working season.
6.2.2 Dam
6.2.2.1 Dam Location
Based on the topography, the dam axis has been proposed with river bed
level as EL +660 m.
53

6.2.2.2 Type of Dam
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Two alternatives were considered for the diversion structure. In first
alternative concrete dam having 5 nos. of lower level orifice type spillway
with a size of 9.75 m x 11.5 m. In addition 2 nos. of Upper level spillways
one on either side of lower spillway a size of 9.75 m x 11.5 m has was
considered. In second alternative, Rockfill dam with side spillway on right
abutment with d/s chute (with same size and number of openings as in first
alternative). Provision of spillway on right bank resulted in high quantities of
excavation along with high cut slopes. Further it necessitated provision of
50-55 m high retaining wall or cellular wall to support the rock fill material.
Keeping above in view first alternative was found to be more favourable.
The IS code stipulates consideration of 1 in 100 year monsoon flood for
diversion in case of embankment dam and 1 in 25 years non-monsoon
flood for concrete dam. The same also favours provision of concrete dam.
In view of above pre-feasibility of the project has been examined with
concrete gravity dam. However, it may be mentioned that based on the
topographical and geological data collected during feasibility stage, if
required, type of the dam and its height shall be reviewed.
6.2.2.3 Fixation of FRL and MDDL
The bed level of tailrace outfall of proposed Naba H.E. Project located
upstream is EL ± 770 , keeping the difference of about 5 m between tailrace
outfall bed level of upstream project & FRL , the FRL for Nalo project has
been proposed as EL 765 m. Needless to mention that during FR/DPR
stage considering the finally adopted parameters of upstream Naba H.E.
Project, FRL of Nalo H.E. Project shall need to be optimised to minimise
54

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
loss of head. MDDL has been fixed at EL 745 m considering proposed
power intake level and power potential studies.
6.2.2.4 Dam Arrangement
The proposed dam is concrete gravity dam across the river with dam top at
EL 770 m. The deepest foundation level has been assumed as EL 645 m
i.e. 15 m below the river bed level (overburden and weathered rock). The
dam is divided in blocks of 15.0/18.0 m width each. The central 7 blocks
shall be overflow/spillway blocks of 15.0/18.0 m width flanked by nonoverflow
blocks on either side of 15.0 m each.
Spillway
Spillway for dam is proposed to be designed for a probable maximum flood
(PMF) of 12300 cumec. Design discharge is proposed to be passed partly
through upper level and rest through lower spillway. Provision of upper level
spillway shall also facilitate in reservoir operation/regulation. Five nos. of
lower level orifice type spillway (inclusive of 1 bay as emergency) is
proposed with crest at EL 715 m and spillway opening size 9.75 m x 11.5
m. In addition two nos of Upper level spillways one on either side of lower
spillway with crest at EL 753.5 m and opening of 9.75 m x 11.5 m has been
proposed. Total length of spillway structure is 120 m.
Non Overflow Blocks
The non-overflow blocks have been provided with top width of 10 m and
downstream slope of 1.1 H: 1V. An upstream slope of 1H: 4V has been
provided below the level of EL 750 m.
Proposed layout of dam area, upstream elevation & cross sections of dam
are enclosed as Plate 6.3, Plate 6.4 and Plate 6.5.
55

6.2.2.5 Energy Dissipation Arrangement
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
A ski-jump type energy dissipation arrangement has been provided
downstream of spillway with flip bucket having lip angle of 30 0 . It may be
mentioned that based on stage- discharge curve at dam site developed at
DPR stage, the lip level of spillway bucket will be kept above maximum tail
water level. A preformed plunge pool of size 100 m (L) x 120 m (B) has
been provided.
6.2.3 Water Conductor System
6.2.3.1 Head Race Tunnel Intake
The water is led to 2 nos intake tunnel through intake structures with invert
at EL 725 m. The invert has been kept 10 m above the lower spillway crest
to minimize silt entry in water conductor system. 2 nos Intake shall be
provided with gate opening of 7.5 m x 8.5 m. An inclined type trash rack
structure is proposed at the entrance of the intake structure with a trash
rack cleaning machine.
6.2.3.2 Desilting Chamber
In order to remove particle having size more than 0.2mm, desilting
chamber has been proposed. Desilting chamber shall have four chambers
each of size 300 m (L) X 17 m (W) X 25 m (H). 2 nos of 8.5 m dia intake
tunnel about 250/350 m long have been proposed between HRT intake
structure and desilting chamber. The 2 nos intake tunnel bifurcates into four
6.0 m dia feeder tunnel feeding each desilting chamber. Tunnel of size
5.3 m dia has been provided after each desilting chamber subsequently
combining to two HRT.
56

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
For flushing out of accumulated silt, each desilting chamber has been
provided with silt flushing duct of size 2.0 m (W) X2.0m (H).Two silt flushing
duct combines to one SFT of size 3.75 m dia. Thus, two SFT have been
proposed.
6.2.3.3 Head Race Tunnel
2 nos of 7.5 m diameter horseshoe shaped headrace tunnel has been
proposed on the right bank of the river. The length of the tunnel shall be
about 2.5/2.6 Km. One 6.5 m (D shaped) intermediate adit about 300 m in
length has been proposed to facilitate construction of HRT.
Rock bolts, shotcrete with wire mesh has been proposed as tunnel support
system. Provision of steel rib support has also been kept to take care of
poor rock strata wherever encountered. The tunnel shall be 600 mm thick
concrete lined.
6.2.3.4 Surge Shaft
2 nos of 20 m diameter and 90 m high circular restricted orifice type
concrete lined surge shaft with gate has been proposed.
Rock bolts, shotcrete with wire mesh has been proposed as shaft support
system. Surge Shaft shall be concrete lined (1000 mm thick).
6.2.3.5 Pressure Shaft
Downstream of Surge Shafts, 2 nos of 6.25 m diameter steel lined pressure
shaft with 82 m vertical drop has been proposed. The centerline elevation of
lower horizontal portion has been kept at EL 633 m i.e. center line of
turbine. After horizontal portion at bottom, each pressure shaft divides in
57

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
two nos 4.25 m dia penstock suitably connected to main inlet valves to feed
each unit of powerhouse.
6.2.3.6 Draft Tube and Tail Race Channel
The water from turbine shall be discharged back to river through draft tubes
and tailrace channel. 2 nos of 5.0 m (W) x 4.3 m (H) draft tube opening for
each unit shall be provided. After the draft tube gates, discharge from four
units shall be led to 60 m wide concrete lined tail race channel about 50m
long.
Proposed cross sections of Water Conductor System are enclosed as
Plate 6.6.
6.2.4 Power House
Based on topography a surface powerhouse has been proposed. It may be
mentioned that the location and type of power house shown in PFR is
indicative only and underground power house, if necessary, may be
considered during F.R. / D.P.R. stage based on collected detailed
topography and geological data.
6.2.4.1 Power House Building
A surface powerhouse has been proposed to house four units of 90 MW
each. The size of power house ( machine hall + service bay ) will be
22m (W) x 103 m (L) x 47m (H) with unit spacing of 19 m. Control block
has been proposed on upstream of the machine hall. The transformers are
proposed to be kept on draft tube gate deck on downstream of the machine
hall.
58

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Proposed layout and cross section of Power House are enclosed as
Plate 6.7 & 6.8.
6.2.5 Switch Yard
Switch yard is proposed on right bank. The size of switch yard will be 80 m
(W) x 160 m (L).
6.2.6 Hydro-Mechanical Equipment
Following hydro-mechanical equipment have been envisaged for Nalo
Hydroelectric Project.
6.2.6.1 Diversion Tunnel Gate and Hoist
After the construction of the dam, for the purpose of plugging the diversion
tunnel, four nos. (two nos. for each tunnel) fixed wheel type gates will be
provided at the inlet of the tunnel. The gates shall be operated by means of
electrically operated rope drum hoists located on the hoist platform installed
over the trestles above deck level. The gate is meant for one time closure,
just before plugging of the tunnel.
6.2.6.2 Lower Spillway Radial Gates, Hoists, Bulkheads and Gantry
Crane
Five numbers submerged type radial gates shall be provided to regulate the
water level in the reservoir. Each gate shall be operated by means of
suitable capacity hydraulic hoist comprising of a power pack and two
cylinders one on each end of the gate.
59

Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
One trolley mounted mobile gasoline engine operated power pack capable
of operating one gate at 25% of the normal rated speed is envisaged for
emergency operation of spillway radial gates.
One portable oil filter unit for filtration, dehydration & degasification of
hydraulic oil is also being provided.
One number Fixed wheel type bulkhead gate fabricated in two units has
been envisaged to cater to the maintenance requirement of five numbers
spillway radial gates. The bulkhead gate shall be able to be lowered under
unbalanced / emergency / flowing water condition corresponding to MDDL
by means of a suitable Capacity Gantry crane with the help of lifting beam.
6.2.6.3 Upper Spillway Radial Gates, Spillway Stoplog & Hoists
Two numbers crest type radial gates shall be provided to control the
discharge through the gated portion of the spillway. Each gate shall be
operated by means of suitable capacity hydraulic hoist comprising of a
power pack and two cylinders one on each end of the gate.
Two numbers grooves with required embedded parts shall be
provided in the upstream of upper spillway radial gate for the
maintenance of radial gates. The bulkhead gate provided for the
maintenance of lower spillway radial gates will be used for the
maintenance of upper spillway radial gates also.
6.2.6.4 Trash Rack and Trash Rack Cleaning Machine
Upstream face of each intake shall be provided with the trash rack screen,
which will be cleaned by means of a trash rack-cleaning machine.
60

6.2.6.5 Intake Gate and Rope Drum Hoists
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Two numbers fixed wheel type gates shall be provided just downstream of
the bell mouth of the intake tunnels. The intake gates shall be lowered /
raised under unbalanced / flowing water condition corresponding to FRL by
means of suitable capacity electrically operated rope drum hoists.
6.2.6.6 Desilting Chamber Inlet, Outlet Gates & Hoists
Four numbers Fixed Wheel type gates shall be provided at the inlet of
desilting chambers for the maintenance requirement of desilting chambers.
The gates shall be lowered / raised under unbalanced / flowing water
condition corresponding to FRL by means of suitable capacity electrically
operated rope drum hoists.
Two numbers slide type gates shall be provided at the outlet of desilting
chambers to isolate the chambers for the maintenance requirements. The
gate shall be lowered / raised under balanced head condition by means of
suitable capacity EOT Crane with the help of lifting beam.
6.2.6.7 Silt Flushing Tunnel Gates & Hoists
In four silt-flushing tunnels, each tunnel is provided with a set of two slide
(Emergency & Service) gates for regulating the discharge through flushing
tunnels. Both the (Emergency & Service) gates shall be operated by means
of hydraulic hoists comprising of individual double acting cylinder and a
common power pack. The gate grooves are provided with bonnet structures
embedded in the concrete and a watertight bonnet cover at the top of the
groove.
61

6.2.6.8 Surge Shaft Gate
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
Two numbers slide type gate shall be provided at the intake of pressure
shafts. The gate shall be operated under balanced head condition by
means of an electrically operated rope drum hoist.
6.2.6.9 Draft Tube Gates and Gantry Crane
To isolate turbines from the tail race tunnel to cater to the inspection /
maintenance requirements of turbines, eight numbers Fixed Wheel type
draft tube gates (two nos. for each unit) have been envisaged. The gates
shall be operated under balanced head conditions by suitable capacity
Gantry Crane with the help of lifting beam.
6.2.6.10 Adit Inspection Gate
One number adit shall be provided with manually operated hinged type gate
in the concrete plug at the HRT construction to give access to the head
race tunnel in the event of any inspection, repair and maintenance.
6.2.6.11 Pressure Shaft Steel Liner
Two nos. Pressure Shaft of dia. 6250 mm fully steel lined will take off from
downstream of steel transition of surge shaft gate to feed the turbine placed
in the power house. It comprises horizontal & vertical ferrules, 2 nos.
vertical bends, 2 nos. plan bends, 1 no bifurcation and branch pipes for
each pressure shaft to feed four turbines.
The material of Pressure Shaft liner shall conform to IS 2002 Gr. 3.
However, for bifurcation material shall conform to ASTM A537 Cl. 1.
6.2.6.12 Instrument and Remote Control
Gates shall be provided with PLC based remote control system for Control
and operation of gates and automatic control of the reservoir level.
62

6.2.6.13 Diesel Generating Set
Preliminary Feasibility Report
Nalo HE Project (4 X 90 MW)
One diesel generating set complete with all accessories, equipment,
instrument and wiring will be provided for emergency operation of gates and
hoists.
6.3 FURTHER STUDIES REQUIRED
Following are some of the studies required to be undertaken during the
preparation of feasibility report / detailed project report:
• Optimisation / finalisation of location of dam type and height of dam
based on topographical and geological inputs
• Optimisation / finalisation of layout of water conductor system based
on topographical and geological inputs
• Optimisation / finalisation of location and orientation of powerhouse
based on topographical and geological inputs
• Evaluation of engineering properties of rock mass.
• Transient analysis and Model studies.
• Detailed design computation to fix size of various components of the
project.
• Integrated reservoir operation and power potential studies of Nalo HE
Project with other Subansiri Basin projects.
• The observations of CWC along with reply of NHPC have been
enclosed as Annexure 6.1 & 6.2 and need to be referred during
Feasibility/DPR stage.
63

7.0 INTRODUCTION
CHAPTER - VII
POWER POTENTIAL STUDIES
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Chapter contains the optimization of power potential of the project on
the basis of the discharge data for the synthetic year June 01 to May 20
(19 Years). Nalo H.E. Project is essentially a run-of-the-river scheme. The
installed capacity of Nalo project has been proposed as 360 MW
comprising of four units, each of 90 MW in the Surface type powerhouse.
The salient features of the project are as follows: -
Installed capacity = 360 MW
No. & size of unit = 4 units of 90MW
Type of power house = Surface type
Net head = 107 meters
Design discharge per unit = 93.2 cumecs
Type of switchgear = Conventional
Turbine type = Vertical Francis
Speed of turbine = 214.3 rpm
Generation voltage = 11 KV
Transmission voltage = 400 KV
GSU Transformer = 13 Nos., 34 MVA, 1-phase
Energy generation in 90%
dependable year with 95%
Machine availability
= 1732.99 MU
64

7.1 AVAILABLE DATA
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Power Potential studies have been carried out based on following
data
a) Discharge Data
b) FRL, MDDL, TWL, Head losses and Area capacity curve.
c) Due to non availability of evaporation loss, evaporation loss has not
been accounted for in the power potential study.
7.2 DISCHARGE DATA
Inflow series of 19 years i.e. 1-2 to 19-20 has been obtained and used for
carrying out power potential and optimization studies. The 10- daily
discharge data in cumecs for all 19 years is shown in the enclosed
Table-7.1. The criterion of 90% dependable flow is applied for conducting
power potential studies and inflow of same is shown in Table-7.2.
7.3 FIXATION OF FULL RESERVOIR LEVEL (FRL)
The FRL level has been fixed at EL 765.0m based on the consideration
that the bed level of tailrace outfall for upstream proposed Naba H.E.
Project is at EL 770 m .
7.4 FIXATION OF MINIMUM DRAW DOWN LEVEL (MDDL)
The choice of MDDL has mainly been based on firm power requirement &
water cover to intake structure . The MDDL has been fixed at EL 745 m.
65

7.5 FIXATION OF TAIL WATER LEVEL (TWL)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The fixation of tail water level of Nalo power house (i.e EL 645 m) has
been considered based on the River bed level EL 635 m at proposed
power house site of this project.
All these values shall require to be reviewed during detail investigation of
the power house complex and Tail race vis-à-vis Topographical and
geological features of the area.
7.6 OPERATING HEAD AND HEAD LOSSES
Full Reservoir Level (FRL) and Minimum Draw Down Level (MDDL) are
respectively at EL 765 m and 745 m. while the average tail water level
corresponding to 4 units running has been taken as EL 645 m. Head
losses in the water conductor system have been taken as 5% of the gross
head. The net operating head for turbines has been calculated from the
following formula,
Net Operating Head:
= MDDL + 2/3(FRL-MDDL) - Maximum Tail Water level – Head Losses
Thus, by above-mentioned formula, net operating head works out to be
107.0 m.
7.7 DEFINITION OF TERMS
7.7.1 90% Dependable Year
This is the lower decile of the series of the corresponding monthly period
of the record i.e. (N+1) x 0.90th year where N is the years for which
hydrological data are available. 90% dependable year comes out as 10-11
as shown in the enclosed Table-7.3.
66

7.7.2 Annual Design Energy
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
This is the yearly energy generated during the 90% dependable year 10-
11 with 95% machine availability, which works out to 1732.99 MU as
shown in Table-7.4. Further it is also mentioned that the load factor during
monsoon i.e. March to November and lean period i.e. Dec. to Feb are
69.60% and 15.87% respectively.
7.7.3 Installed Capacity
The installed capacity of Power house has been selected based on the
following considerations: -
• Assessment of the energy generation with various installed
capacities.
• Maximum utilization of the available inflow.
• Incremental value of energy generation with the increased installed
capacity.
• Annual Load factor.
The power potential study has been carried out for different installed
capacities ranging from 210 MW to 660 MW with an increment of 30 MW,
as shown in Table-7.5. Based on the above-mentioned parameters, the
installed capacity of the power plant has been selected as 360MW
(Annexure 7.1).
7.7.4 Size of Generating Units
The power load demand in India is increasing at a very rapid rate, and
both hydro electric and thermal (including nuclear) power potential in the
67

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
country are being developed not only to meet the overall requirements, but
simultaneously also to provide a proper hydro and thermal power for
optimum operation of the system. Keeping this in view current practice is
to opt for largest size hydro units permissible within the parameters of
economy, operating efficiency, maintenance, optimum utilization of
available water, transport limitations etc. Based on above-mentioned
parameters, 4 No. Units of 90 MW each have been proposed for this
project.
7.7.5 Annual Energy Generation
The restricted energy generations in the 90% dependable year i.e. (10-11)
are shown in the enclosed Table-7.4. It may be seen from this table, that
the total energy generation in 90% dependable year with 95% machine
availability restricted to an installed capacity of 360 MW is 1732.99 MU.
The observations of CEA alongwith reply of NHPC have been enclosed as
Annexure 2.3, Annexure 7.2 and Annexure 7.3 and needed to be
referred during feasibility/ DPR stage. All the suggestions made by CEA
have been incorporated in the report.
68

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
TABLE – 7.1
DISCHARGE DATA (Cumecs)
Month 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20
JUNE
JULY
AUGUST
SEPTEMBER
OCTOBER
NOVEMBER
DECEMBER
JANUARY
FEBRUARY
MARCH
APRIL
MAY
1-10 492.85 566.86 272.94 268.21 476.97 209.23 295.88 1127.03 202.66 143.23 255.80 343.43 327.54 501.43 155.90 631.53 146.16 134.07 611.35
11-20 857.14 725.43 434.70 505.02 746.53 228.85 347.09 1408.97 193.10 297.93 290.04 417.71 308.80 855.74 292.02 439.38 187.34 175.79 936.14
21-30 1305.27 873.72 456.62 666.80 844.43 283.63 495.99 1263.24 311.32 368.86 269.85 596.81 556.71 1144.36 445.15 443.16 279.69 338.61 948.94
1-10 642.67 748.03 535.77 801.11 1086.80 538.75 580.81 1474.65 891.05 607.68 413.38 708.09 489.73 712.68 975.67 385.55 316.97 397.91 1117.63
11-20 1008.71 752.87 525.04 1301.60 974.83 431.36 836.73 1627.29 694.81 468.63 713.66 565.00 768.24 841.70 913.19 320.03 613.60 756.95 1354.05
21-31 875.61 610.58 417.68 987.43 779.52 674.55 1027.29 2049.64 995.86 746.06 521.46 925.59 607.71 1030.23 801.43 357.19 763.45 681.22 1782.59
1-10 990.15 499.87 470.11 781.31 720.45 697.44 329.93 645.81 853.55 393.01 532.10 429.79 955.77 733.12 801.15 561.85 843.94 468.63 562.16
11-20 966.28 547.46 489.65 618.76 632.06 774.60 421.36 728.91 1090.48 603.00 582.10 583.84 1247.86 777.43 721.60 863.04 1120.37 433.24 628.67
21-31 624.84 629.23 901.83 507.45 766.95 708.83 389.33 798.77 807.46 537.79 960.57 1032.75 794.79 735.18 631.70 941.86 1339.13 438.42 1011.12
1-10 574.95 367.59 1423.58 365.24 477.05 554.09 299.74 666.84 605.27 384.55 907.31 780.26 405.31 663.69 345.59 696.98 1116.37 446.45 723.53
11-20 725.34 617.64 1283.45 323.17 398.80 427.67 365.63 477.13 545.42 716.92 993.40 824.58 379.00 482.91 381.17 545.20 789.80 412.03 587.53
21-30 437.75 536.53 983.64 421.49 445.86 347.33 421.67 664.97 589.60 900.82 795.28 608.04 302.19 443.45 366.70 721.23 863.18 323.88 394.87
1-10 252.41 270.35 589.21 291.62 627.37 563.08 382.66 536.10 652.76 505.86 665.92 352.42 570.93 543.27 300.63 429.30 392.29 457.51 347.47
11-20 445.25 259.30 404.75 409.81 625.45 510.19 201.23 578.19 279.04 269.43 252.64 392.32 248.04 276.60 225.20 263.33 427.98 458.09 348.26
21-31 243.22 236.40 292.90 226.10 304.32 263.75 161.81 262.65 290.91 157.76 237.27 198.59 205.54 162.34 198.21 186.56 336.30 273.36 318.61
1-10 154.91 223.85 178.19 129.01 153.15 204.63 147.70 260.49 163.35 116.17 171.35 120.75 166.01 169.90 217.98 191.76 200.53 163.46 159.44
11-20 112.49 189.75 107.63 105.46 122.11 118.95 161.80 223.00 170.88 135.75 146.90 114.47 157.73 145.41 179.36 172.43 120.63 103.16 96.11
21-30 121.47 109.54 120.06 97.52 104.60 103.08 146.46 146.87 106.57 95.93 133.23 93.82 116.45 104.46 124.11 130.83 83.03 89.22 95.04
1-10 80.10 101.96 121.31 78.94 108.24 81.17 141.82 92.97 73.71 82.45 90.09 102.86 78.68 109.03 134.37 89.32 83.82 106.50 116.13
11-20 80.60 81.21 102.45 85.90 78.99 83.11 96.78 98.39 76.61 67.08 105.53 78.77 81.56 121.67 95.40 72.83 70.56 94.59 83.30
21-31 76.17 66.44 87.51 83.89 82.62 68.69 79.89 88.03 63.55 60.27 93.17 70.09 79.24 105.63 80.57 75.21 72.67 88.76 71.94
1-10 82.70 70.04 82.87 66.96 69.84 51.41 91.65 80.00 50.86 46.10 107.30 53.02 63.98 110.32 61.61 58.28 72.59 75.25 65.87
11-20 65.82 76.92 79.61 53.32 73.13 61.40 85.77 63.86 47.68 45.22 108.06 53.42 52.32 99.72 67.64 46.25 73.94 75.77 54.11
21-31 67.86 68.77 72.38 50.25 73.57 68.10 92.70 60.14 50.06 47.07 102.18 59.21 49.68 94.81 74.32 51.48 70.10 70.33 51.58
1-10 74.46 70.85 71.97 56.10 87.71 75.43 102.01 53.70 61.23 62.73 92.55 70.94 65.95 124.04 99.04 65.83 80.36 94.21 48.22
11-20 83.84 80.74 69.74 50.95 90.16 70.05 76.08 49.80 77.47 49.15 93.52 52.82 51.86 77.87 96.59 72.91 57.85 102.11 48.11
21-28 79.53 71.29 75.55 69.87 94.86 66.06 79.04 51.94 74.76 77.24 85.84 78.70 65.75 93.32 104.22 73.11 85.71 107.91 61.54
1-10 72.29 95.63 86.05 66.63 120.95 83.16 102.20 94.52 123.68 83.06 98.90 101.03 98.65 110.06 116.98 79.04 117.17 96.33 58.93
11-20 81.32 114.89 114.73 68.28 116.03 76.01 94.85 98.77 97.55 118.52 88.76 131.10 134.06 121.05 91.86 87.91 97.08 127.56 69.54
21-31 73.22 133.29 146.11 75.84 94.94 72.53 120.38 86.50 99.21 110.02 101.90 131.94 114.95 105.21 89.54 125.47 84.58 161.49 77.64
1-10 124.18 191.30 161.66 137.06 170.96 115.96 170.23 103.38 122.78 114.92 159.46 161.94 151.52 112.48 163.52 226.34 126.05 198.21 102.43
11-20 160.16 153.45 229.57 163.26 164.60 149.15 177.55 181.23 146.29 115.16 183.86 156.26 202.57 109.47 135.66 190.61 119.85 272.33 105.79
21-30 193.61 186.08 302.46 174.99 144.14 184.79 132.75 194.81 148.80 141.68 183.40 173.86 172.71 105.84 208.33 245.73 177.89 196.93 152.49
1-10 240.28 189.64 352.33 241.74 189.24 311.29 298.57 219.17 192.94 298.78 323.34 201.00 217.75 244.92 253.14 252.73 189.50 313.86 198.65
11-20 384.61 241.77 412.33 298.49 265.90 285.81 456.79 155.68 142.68 361.63 277.86 192.93 216.13 210.27 188.54 197.81 139.43 414.88 198.70
21-31 298.90 180.15 234.00 537.33 170.64 325.53 666.27 248.61 165.53 342.53 155.95 395.08 212.03 129.10 255.06 150.85 114.02 308.28 256.03
69

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Table 7.2
90% DEPENDABLE YEAR FLOWS FOR POWER GENERATION
MONTH / PERIOD
JUN
JUL
AUG
SEP
OCT
NOV
DEC
JAN
FEB
MAR
APR
MAY
90% dependable year 10-11
flows CUMECS
1-10 143.23
11-20 297.93
21-30 368.86
1-10 607.68
11-20 468.63
21-31 746.06
1-10 393.01
11-20 603.00
21-31 537.79
1-10 384.55
11-20 716.92
21-30 900.82
1-10 505.86
11-20 269.43
21-31 157.76
1-10 116.17
11-20 135.75
21-30 95.93
1-10 82.45
11-20 67.08
21-31 60.27
1-10 46.10
11-20 45.22
21-31 47.07
1-10 62.73
11-20 49.15
21-28 77.24
1-10 83.06
11-20 118.52
21-31 110.02
1-10 114.92
11-20 115.16
21-30 141.68
1-10 298.78
11-20 361.63
21-31 342.53
70

Installed
Capacity(MW)
360
Table 7.3
SUMMARY SHEET
Selected
Head
107
FRL 765
Design
Discharge
372.79
MDDL 745 Head Losses 5%
Sl.No. Year
Total Inflow
(MCM)
Unrestricted
Energy (MU)
Energy (with
95% M/C
Availability)
(MU)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Overall
Efficiency
Machine
Availability
Monsoon Period
Load Factor (%)
(March to Nov.)
92%
95%
Lean period
Load factor
(%) (Dec. to
Feb.)
1 8-9 14956.79 4012.14 1855.91 74.42% 19.17%
2 19-20 12264.77 3290.01 1756.33 70.22% 18.09%
3 1-2 11543.89 3096.64 1832.92 73.00% 20.55%
4 3-4 11143.93 2989.35 1962.30 77.64% 23.00%
5 14-15 10995.51 2949.53 1798.35 68.94% 27.95%
6 5-6 10965.93 2941.60 1845.61 72.89% 22.53%
7 17-18 10398.07 2789.27 1661.02 65.28% 19.81%
8 12-13 10038.68 2692.86 1815.62 72.81% 18.39%
9 11-12 9938.23 2665.92 1826.68 70.06% 26.50%
10 9-10 9928.91 2663.42 1668.15 66.48% 17.06%
11 4-5 9849.40 2642.09 1775.41 70.97% 17.75%
12 2-3 9605.69 2576.72 1819.82 71.92% 20.49%
13 13-14 9427.09 2528.81 1763.05 70.31% 17.55%
14 16-17 9173.26 2460.72 1806.62 72.17% 17.98%
15 15-16 9154.77 2455.76 1781.23 68.47% 24.41%
16 7-8 8920.21 2392.84 1873.80 72.40% 25.49%
17 6-7 8704.51 2334.97 1777.21 70.55% 18.66%
18 10-11 8517.07 2284.69 1732.99 69.60% 15.87%
19 18-19 8327.15 2233.75 1883.59 73.41% 24.13%
71

S.
NO.
Table 7.3 A
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
AVAILABILITY OF UNITS IN KWH/KW FOR INCREMENTAL INSTALLATION IN
90% DEPENDABLE YEAR
Net Head 107.00
INSTALLED
CAPACITY
MW
ANNUAL
ENERGY
MU
LOAD
FACTOR %
1 210 1259.93 68.49%
2 240 1377.29 65.51%
3 270 1492.29 63.09%
4 300 1596.75 60.76%
5 330 1692.51 58.55%
6 360 1777.06 56.35%
7 390 1843.51 53.96%
8 420 1902.55 51.71%
9 450 1961.59 49.76%
10 480 2014.04 47.90%
11 510 2060.73 46.13%
12 540 2099.91 44.39%
13 570 2136.63 42.79%
14 600 2165.95 41.21%
15 630 2188.27 39.65%
16 660 2210.59 38.23%
10-11
Overall
Efficiency
INCREMENTAL
ENERGY MU
92%
INCREMENTAL
ENERGY
KWH/KW
LOAD
FACTOR FOR
ADDITIONAL
CAPACITY %
117.36 3912.00 44.66%
115.01 3833.53 43.76%
104.46 3481.90 39.75%
95.76 3192.00 36.44%
84.55 2818.29 32.17%
66.45 2215.13 25.29%
59.04 1968.00 22.47%
59.04 1968.00 22.47%
52.45 1748.41 19.96%
46.68 1556.09 17.76%
39.19 1306.24 14.91%
36.72 1224.00 13.97%
29.32 977.23 11.16%
22.32 744.00 8.49%
22.32 744.00 8.49%
72

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Table 7.4
POWER POTENTIAL IN 90% DEPENDABLE YEAR WITH 95% m/c
AVAILABILITY
YEAR 10-11 Live storage(Mcum)= 50.37
Net Head 107.00 Restricted MW 360 Overall Efficiency 92%
UNRESTRICTED UNRESTRICTED RESTRICTED ENERGY
PERIOD
INFLOW
Mcum
INFLOW
cumecs
POWER
POTENTIAL MW
ENERGY (MU) POWER RESTRICTED TO
POTENTIAL 360 MW
95% m/c
Availability
(360 MW) (MU)
1-10 123.75 143.23 138.32 33.20 138.32 33.20 33.20
Jun-10 11-20 257.41 297.93 287.71 69.05 287.71 69.05 69.05
21-30 318.69 368.86 356.20 85.49 356.20 85.49 85.49
1-10 525.04 607.68 586.84 140.84 360.00 86.40 82.08
Jul-10 11-20 404.89 468.63 452.55 108.61 360.00 86.40 82.08
21-31 709.06 746.06 720.47 190.20 360.00 95.04 90.29
1-10 339.56 393.01 379.53 91.09 360.00 86.40 82.08
Aug-10 11-20 520.99 603.00 582.32 139.76 360.00 86.40 82.08
21-31 511.12 537.79 519.35 137.11 360.00 95.04 90.29
1-10 332.26 384.55 371.36 89.13 360.00 86.40 82.08
Sep-10 11-20 619.42 716.92 692.33 166.16 360.00 86.40 82.08
21-30 778.31 900.82 869.92 208.78 360.00 86.40 82.08
1-10 437.07 505.86 488.51 117.24 360.00 86.40 82.08
Oct-10 11-20 232.79 269.43 260.19 62.45 260.19 62.45 62.45
21-31 149.94 157.76 152.35 40.22 152.35 40.22 40.22
1-10 100.37 116.17 112.18 26.92 112.18 26.92 26.92
Nov-10 11-20 117.29 135.75 131.10 31.46 131.10 31.46 31.46
21-30 82.88 95.93 92.64 22.23 92.64 22.23 22.23
1-10 71.23 82.45 79.62 19.11 79.62 19.11 19.11
Dec-10 11-20 57.96 67.08 64.78 15.55 64.78 15.55 15.55
21-31 57.28 60.27 58.20 15.36 58.20 15.36 15.36
1-10 39.83 46.10 44.52 10.68 44.52 10.68 10.68
Jan-11 11-20 39.07 45.22 43.67 10.48 43.67 10.48 10.48
21-31 44.74 47.07 45.46 12.00 45.46 12.00 12.00
1-10 54.20 62.73 60.57 14.54 60.57 14.54 14.54
Feb-11 11-20 42.46 49.15 47.46 11.39 47.46 11.39 11.39
21-28 53.39 77.24 74.59 14.32 74.59 14.32 14.32
1-10 71.76 83.06 80.21 19.25 80.21 19.25 19.25
Mar-11 11-20 102.40 118.52 114.45 27.47 114.45 27.47 27.47
21-31 104.57 110.02 106.25 28.05 106.25 28.05 28.05
1-10 99.29 114.92 110.97 26.63 110.97 26.63 26.63
Apr-11 11-20 99.50 115.16 111.21 26.69 111.21 26.69 26.69
21-30 122.41 141.68 136.82 32.84 136.82 32.84 32.84
1-10 258.14 298.78 288.53 69.25 288.53 69.25 69.25
May-11 11-20 312.45 361.63 349.23 83.81 349.23 83.81 83.81
21-31 325.54 342.53 330.78 87.33 330.78 87.33 87.33
Total 8517.07 2284.69 1777.06 1732.99
Annual
L/F=
56.35%
L/F monsoon
(March to Nov.)=
69.60%
L/F non-monsoon
(Dec. to Feb.)=
15.87%
Total Inflow during
Monsoon
season(Mcum)=
8056.90
Total Inflow during Nonmonsoon
season
(Mcum)= 460.16
Average Power
during nonmonsoon
season
(MW)=
57.65 MWhr.= 13511.70
FIRM POWER(MW) 43.67 Hrs from Live storage 37.53
73

Period
Net Head 107.00 Design Discharge of Unit 93.2
Inflow
(Cumecs)
Power
Potential
(MW)
Unrestricted
Energy
Generation
(MU)
Table 7.5
POWER POTENTIAL IN 90% Dependable Year
Incre
menta
l Steps
10-11
30 Overall Efficiency 92%
ENERGY GENERATION IN MU RESTRICTED TO VARIOUS MW
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
210 240 270 300 330 360 390 420 450 480 510 540 570 600 630 660
Jun-10 1-10 143.23 138.32 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20 33.20
11-20 297.93 287.71 69.05 50.40 57.60 64.80 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05 69.05
21-30 368.86 356.20 85.49 50.40 57.60 64.80 72.00 79.20 85.49 85.49 85.49 85.49 85.49 85.49 85.49 85.49 85.49 85.49 85.49
Jul-10 1-10 607.68 586.84 140.84 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 115.20 122.40 129.60 136.80 140.84 140.84 140.84
11-20 468.63 452.55 108.61 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 108.61 108.61 108.61 108.61 108.61 108.61 108.61
21-31 746.06 720.47 190.20 55.44 63.36 71.28 79.20 87.12 95.04 102.96 110.88 118.80 126.72 134.64 142.56 150.48 158.40 166.32 174.24
Aug-10 1-10 393.01 379.53 91.09 50.40 57.60 64.80 72.00 79.20 86.40 91.09 91.09 91.09 91.09 91.09 91.09 91.09 91.09 91.09 91.09
11-20 603.00 582.32 139.76 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 115.20 122.40 129.60 136.80 139.76 139.76 139.76
21-31 537.79 519.35 137.11 55.44 63.36 71.28 79.20 87.12 95.04 102.96 110.88 118.80 126.72 134.64 137.11 137.11 137.11 137.11 137.11
Sep-10 1-10 384.55 371.36 89.13 50.40 57.60 64.80 72.00 79.20 86.40 89.13 89.13 89.13 89.13 89.13 89.13 89.13 89.13 89.13 89.13
11-20 716.92 692.33 166.16 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 115.20 122.40 129.60 136.80 144.00 151.20 158.40
21-30 900.82 869.92 208.78 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 115.20 122.40 129.60 136.80 144.00 151.20 158.40
Oct-10 1-10 505.86 488.51 117.24 50.40 57.60 64.80 72.00 79.20 86.40 93.60 100.80 108.00 115.20 117.24 117.24 117.24 117.24 117.24 117.24
11-20 269.43 260.19 62.45 50.40 57.60 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45 62.45
21-31 157.76 152.35 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22 40.22
Nov-10 1-10 116.17 112.18 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92 26.92
11-20 135.75 131.10 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46 31.46
21-30 95.93 92.64 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23 22.23
Dec-10 1-10 82.45 79.62 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11 19.11
11-20 67.08 64.78 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55 15.55
21-31 60.27 58.20 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36 15.36
Jan-11 1-10 46.10 44.52 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68 10.68
11-20 45.22 43.67 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48 10.48
21-31 47.07 45.46 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00 12.00
Feb-11 1-10 62.73 60.57 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54 14.54
11-20 49.15 47.46 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39 11.39
21-28 77.24 74.59 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32 14.32
Mar-11 1-10 83.06 80.21 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25 19.25
11-20 118.52 114.45 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47 27.47
21-31 110.02 106.25 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05 28.05
Apr-11 1-10 114.92 110.97 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63 26.63
11-20 115.16 111.21 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69 26.69
21-30 141.68 136.82 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84 32.84
May-11 1-10 298.78 288.53 69.25 50.40 57.60 64.80 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25 69.25
11-20 361.63 349.23 83.81 50.40 57.60 64.80 72.00 79.20 83.81 83.81 83.81 83.81 83.81 83.81 83.81 83.81 83.81 83.81 83.81
21-31 342.53 330.78 87.33 55.44 63.36 71.28 79.20 87.12 87.33 87.33 87.33 87.33 87.33 87.33 87.33 87.33 87.33 87.33 87.33
2284.69
1259.
93
1377.
29
1492.
29
1596.
75
1692.
51
1777.
06
1843.51 1902.55 1961.59 2014.04 2060.73 2099.91 2136.63 2165.95 2188.27 2210.59
74

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
1-2
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGEUNRESTRICTEDUNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10 425.82 492.85 475.94 114.23 360 86.40 82.08
June-01 11-20 740.57 857.14 827.73 198.66 360 86.40 82.08
21-30 1127.75 1305.27 1260.49 302.52 360 86.40 82.08
1-10 555.26 642.67 620.62 148.95 360 86.40 82.08
July-01 11-20 871.52 1008.71 974.10 233.79 360 86.40 82.08
21-31 832.18 875.61 845.58 223.23 360 95.04 90.29
1-10 855.49 990.15 956.18 229.48 360 86.40 82.08
Aug-01 11-20 834.86 966.28 933.13 223.95 360 86.40 82.08
21-31 593.85 624.84 603.41 159.30 360 95.04 90.29
1-10 496.75 574.95 555.22 133.25 360 86.40 82.08
Sep-01 11-20 626.69 725.34 700.46 168.11 360 86.40 82.08
21-30 378.22 437.75 422.73 101.46 360 86.40 82.08
1-10 218.08 252.41 243.75 58.50 244 58.50 58.50
Oct-01 11-20 384.70 445.25 429.98 103.19 360 86.40 82.08
21-31 231.16 243.22 234.88 62.01 235 62.01 62.01
1-10 133.84 154.91 149.59 35.90 150 35.90 35.90
Nov-01 11-20 97.19 112.49 108.63 26.07 109 26.07 26.07
21-30 104.95 121.47 117.30 28.15 117 28.15 28.15
1-10 69.20 80.10 77.35 18.56 77 18.56 18.56
Dec-01 11-20 69.64 80.60 77.84 18.68 78 18.68 18.68
21-31 72.39 76.17 73.56 19.42 74 19.42 19.42
1-10 71.46 82.70 79.87 19.17 80 19.17 19.17
Jan-02 11-20 56.86 65.82 63.56 15.25 64 15.25 15.25
21-31 64.49 67.86 65.53 17.30 66 17.30 17.30
1-10 64.33 74.46 71.90 17.26 72 17.26 17.26
Feb-02 11-20 72.44 83.84 80.97 19.43 81 19.43 19.43
21-28 54.97 79.53 76.80 14.75 77 14.75 14.75
1-10 62.46 72.29 69.81 16.75 70 16.75 16.75
Mar-02 11-20 70.26 81.32 78.53 18.85 79 18.85 18.85
21-31 69.58 73.22 70.70 18.67 71 18.67 18.67
1-10 107.29 124.18 119.92 28.78 120 28.78 28.78
Apr-02 11-20 138.38 160.16 154.66 37.12 155 37.12 37.12
21-30 167.28 193.61 186.97 44.87 187 44.87 44.87
1-10 207.60 240.28 232.04 55.69 232 55.69 55.69
May-02 11-20 332.30 384.61 371.41 89.14 360 86.40 82.08
21-31 284.07 298.90 288.65 76.20 289 76.20 76.20
Total 11543.89 3096.64 1894.26 1832.92
Annual
L/F 60.07%
L/F monsoon
(March to Nov.)
73.00%
L/F non-monsoon (Dec
to Feb.)
20.55%
75

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
2-3
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10
June-
11-20
02
21-30
489.77
626.77
754.90
566.86
725.43
873.72
547.42
700.55
843.75
131.38
168.13
202.50
360
360
360
86.40
86.40
86.40
82.08
82.08
82.08
1-10 646.29 748.03 722.37 173.37 360 86.40 82.08
July-0211-20
650.48 752.87 727.04 174.49 360 86.40 82.08
21-31 580.30 610.58 589.64 155.66 360 95.04 90.29
1-10 431.89 499.87 482.73 115.85 360 86.40 82.08
Aug-0211-20
473.00 547.46 528.68 126.88 360 86.40 82.08
21-31 598.02 629.23 607.65 160.42 360 95.04 90.29
1-10 317.60 367.59 354.98 85.20 355 85.20 85.20
Sep-0211-20
533.64 617.64 596.46 143.15 360 86.40 82.08
21-30 463.57 536.53 518.13 124.35 360 86.40 82.08
1-10 233.58 270.35 261.08 62.66 261 62.66 62.66
Oct-02 11-20 224.04 259.30 250.41 60.10 250 60.10 60.10
21-31 224.68 236.40 228.29 60.27 228 60.27 60.27
1-10 193.40 223.85 216.17 51.88 216 51.88 51.88
Nov-0211-20
163.95 189.75 183.24 43.98 183 43.98 43.98
21-30 94.64 109.54 105.78 25.39 106 25.39 25.39
1-10 88.09 101.96 98.46 23.63 98 23.63 23.63
Dec-0211-20
70.17 81.21 78.43 18.82 78 18.82 18.82
21-31 63.15 66.44 64.17 16.94 64 16.94 16.94
1-10 60.52 70.04 67.64 16.23 68 16.23 16.23
Jan-03 11-20 66.46 76.92 74.28 17.83 74 17.83 17.83
21-31 65.36 68.77 66.41 17.53 66 17.53 17.53
1-10 61.21 70.85 68.42 16.42 68 16.42 16.42
Feb-0311-20
69.76 80.74 77.97 18.71 78 18.71 18.71
21-28 49.27 71.29 68.84 13.22 69 13.22 13.22
1-10 82.63 95.63 92.35 22.16 92 22.16 22.16
Mar-0311-20
99.27 114.89 110.95 26.63 111 26.63 26.63
21-31 126.68 133.29 128.72 33.98 129 33.98 33.98
1-10 165.29 191.30 184.74 44.34 185 44.34 44.34
Apr-03 11-20 132.58 153.45 148.18 35.56 148 35.56 35.56
21-30 160.77 186.08 179.69 43.13 180 43.13 43.13
1-10 163.85 189.64 183.14 43.95 183 43.95 43.95
May-0311-20
208.89 241.77 233.48 56.04 233 56.04 56.04
21-31 171.22 180.15 173.97 45.93 174 45.93 45.93
Total 9605.69 2576.72 1868.21 1819.82
Annua
L/F 59.24%
L/F monsoon
(March to Nov.)
71.92%
L/F non-monsoon (Dec
to Feb.)
20.49%
76

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
3-4
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month
RESTRICTED RESTRICTED
DISCHARGE DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10
June-
11-20
03
21-30
235.82
375.58
394.52
272.94
434.70
456.62
263.58
419.79
440.95
63.26
100.75
105.83
264
360
360
63.26
86.40
86.40
63.26
82.08
82.08
1-10 462.91 535.77 517.40 124.17 360 86.40 82.08
July-0311-20
453.63 525.04 507.03 121.69 360 86.40 82.08
21-31 396.96 417.68 403.35 106.48 360 95.04 90.29
1-10 406.18 470.11 453.98 108.96 360 86.40 82.08
Aug-0311-20
423.06 489.65 472.86 113.49 360 86.40 82.08
21-31 857.10 901.83 870.90 229.92 360 95.04 90.29
1-10 1229.97 1423.58 1374.74 329.94 360 86.40 82.08
Sep-0311-20
1108.90 1283.45 1239.43 297.46 360 86.40 82.08
21-30 849.86 983.64 949.90 227.97 360 86.40 82.08
1-10 509.07 589.21 569.00 136.56 360 86.40 82.08
Oct-03 11-20 349.70 404.75 390.86 93.81 360 86.40 82.08
21-31 278.37 292.90 282.85 74.67 283 74.67 74.67
1-10 153.95 178.19 172.08 41.30 172 41.30 41.30
Nov-0311-20
92.99 107.63 103.94 24.95 104 24.95 24.95
21-30 103.73 120.06 115.94 27.83 116 27.83 27.83
1-10 104.81 121.31 117.15 28.12 117 28.12 28.12
Dec-0311-20
88.52 102.45 98.93 23.74 99 23.74 23.74
21-31 83.17 87.51 84.51 22.31 85 22.31 22.31
1-10 71.60 82.87 80.02 19.21 80 19.21 19.21
Jan-04 11-20 68.79 79.61 76.88 18.45 77 18.45 18.45
21-31 68.79 72.38 69.90 18.45 70 18.45 18.45
1-10 62.18 71.97 69.50 16.68 70 16.68 16.68
Feb-0411-20
60.26 69.74 67.35 16.16 67 16.16 16.16
21-29 58.75 75.55 72.96 15.76 73 15.76 15.76
1-10 74.35 86.05 83.10 19.94 83 19.94 19.94
Mar-0411-20
99.12 114.73 110.79 26.59 111 26.59 26.59
21-31 138.86 146.11 141.10 37.25 141 37.25 37.25
1-10 139.67 161.66 156.11 37.47 156 37.47 37.47
Apr-04 11-20 198.35 229.57 221.70 53.21 222 53.21 53.21
21-30 261.33 302.46 292.08 70.10 292 70.10 70.10
1-10 304.41 352.33 340.25 81.66 340 81.66 81.66
May-0411-20
356.25 412.33 398.19 95.56 360 86.40 82.08
21-31 222.39 234.00 225.97 59.66 226 59.66 59.66
Total 11143.93 2989.35 2023.64 1962.30
Annua
L/F 64.17%
L/F monsoon
(March to Nov.)
77.64%
L/F non-monsoon
(Dec to Feb.)
23.00%
77

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
4-5
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
04
1-10
11-20
21-30
231.74
436.34
576.11
268.21
505.02
666.80
259.01
487.70
643.92
62.16
117.05
154.54
259
360
360
62.16
86.40
86.40
62.16
82.08
82.08
1-10 692.16 801.11 773.63 185.67 360 86.40 82.08
July-04 11-20 1124.58 1301.60 1256.95 301.67 360 86.40 82.08
21-31 938.46 987.43 953.56 251.74 360 95.04 90.29
1-10 675.05 781.31 754.51 181.08 360 86.40 82.08
Aug-04 11-20 534.60 618.76 597.53 143.41 360 86.40 82.08
21-31 482.28 507.45 490.04 129.37 360 95.04 90.29
1-10 315.57 365.24 352.71 84.65 353 84.65 84.65
Sep-04 11-20 279.22 323.17 312.08 74.90 312 74.90 74.90
21-30 364.17 421.49 407.03 97.69 360 86.40 82.08
1-10 251.96 291.62 281.62 67.59 282 67.59 67.59
Oct-04 11-20 354.07 409.81 395.75 94.98 360 86.40 82.08
21-31 214.89 226.10 218.35 57.64 218 57.64 57.64
1-10 111.47 129.01 124.59 29.90 125 29.90 29.90
Nov-04 11-20 91.12 105.46 101.84 24.44 102 24.44 24.44
21-30 84.26 97.52 94.17 22.60 94 22.60 22.60
1-10 68.20 78.94 76.23 18.30 76 18.30 18.30
Dec-04 11-20 74.22 85.90 82.95 19.91 83 19.91 19.91
21-31 79.73 83.89 81.02 21.39 81 21.39 21.39
1-10 57.86 66.96 64.67 15.52 65 15.52 15.52
Jan-05 11-20 46.07 53.32 51.49 12.36 51 12.36 12.36
21-31 47.76 50.25 48.53 12.81 49 12.81 12.81
1-10 48.47 56.10 54.17 13.00 54 13.00 13.00
Feb-05 11-20 44.02 50.95 49.20 11.81 49 11.81 11.81
21-28 48.30 69.87 67.48 12.96 67 12.96 12.96
1-10 57.57 66.63 64.34 15.44 64 15.44 15.44
Mar-05 11-20 58.99 68.28 65.93 15.82 66 15.82 15.82
21-31 72.08 75.84 73.24 19.34 73 19.34 19.34
1-10 118.42 137.06 132.36 31.77 132 31.77 31.77
Apr-05 11-20 141.06 163.26 157.66 37.84 158 37.84 37.84
21-30 151.19 174.99 168.99 40.56 169 40.56 40.56
1-10 208.86 241.74 233.44 56.03 233 56.03 56.03
May-05 11-20 257.90 298.49 288.25 69.18 288 69.18 69.18
21-31 510.68 537.33 518.90 136.99 360 95.04 90.29
Total 9849.40 2642.09 1824.23 1775.41
Annual
L/F 57.85%
L/F monsoon
(March to Nov.)
70.97%
L/F non-monsoon (Dec
to Feb.)
17.75%
78

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
5-6
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10 412.10 476.97 460.60 110.54 360 86.40 82.08
11-20 645.00 746.53 720.92 173.02 360 86.40 82.08
June-
05
July-05
Aug-05
Sep-05
Oct-05
Nov-05
Dec-05
Jan-06
Feb-06
Mar-06
Apr-06
May-06
21-30 729.59 844.43 815.47 195.71 360 86.40 82.08
1-10 939.00 1086.80 1049.52 251.88 360 86.40 82.08
11-20 842.25 974.83 941.39 225.93 360 86.40 82.08
21-31 740.86 779.52 752.78 198.73 360 95.04 90.29
1-10 622.47 720.45 695.74 166.98 360 86.40 82.08
11-20 546.10 632.06 610.38 146.49 360 86.40 82.08
21-31 728.91 766.95 740.64 195.53 360 95.04 90.29
1-10 412.17 477.05 460.69 110.56 360 86.40 82.08
11-20 344.57 398.80 385.12 92.43 360 86.40 82.08
21-30 385.23 445.86 430.57 103.34 360 86.40 82.08
1-10 542.05 627.37 605.85 145.40 360 86.40 82.08
11-20 540.39 625.45 604.00 144.96 360 86.40 82.08
21-31 289.22 304.32 293.88 77.58 294 77.58 77.58
1-10 132.32 153.15 147.90 35.50 148 35.50 35.50
11-20 105.50 122.11 117.92 28.30 118 28.30 28.30
21-30 90.37 104.60 101.01 24.24 101 24.24 24.24
1-10 93.52 108.24 104.53 25.09 105 25.09 25.09
11-20 68.25 78.99 76.28 18.31 76 18.31 18.31
21-31 78.53 82.62 79.79 21.06 80 21.06 21.06
1-10 60.34 69.84 67.45 16.19 67 16.19 16.19
11-20 63.19 73.13 70.62 16.95 71 16.95 16.95
21-31 69.92 73.57 71.05 18.76 71 18.76 18.76
1-10 75.78 87.71 84.70 20.33 85 20.33 20.33
11-20 77.89 90.16 87.06 20.90 87 20.90 20.90
21-28 65.56 94.86 91.60 17.59 92 17.59 17.59
1-10 104.50 120.95 116.80 28.03 117 28.03 28.03
11-20 100.25 116.03 112.05 26.89 112 26.89 26.89
21-31 90.23 94.94 91.68 24.20 92 24.20 24.20
1-10 147.71 170.96 165.09 39.62 165 39.62 39.62
11-20 142.21 164.60 158.95 38.15 159 38.15 38.15
21-30 124.54 144.14 139.19 33.41 139 33.41 33.41
1-10 163.50 189.24 182.75 43.86 183 43.86 43.86
11-20 229.74 265.90 256.78 61.63 257 61.63 61.63
21-31 162.17 170.64 164.78 43.50 165 43.50 43.50
Total 10965.93 2941.60 1906.96 1845.61
Annual
L/F 60.47%
L/F monsoon
(March to Nov.)
72.89%
L/F non-monsoon (Dec
to Feb.)
22.53%
79

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
6-7
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
06
1-10
11-20
21-30
180.78
197.73
245.06
209.23
228.85
283.63
202.05
221.00
273.90
48.49
53.04
65.74
202
221
274
48.49
53.04
65.74
48.49
53.04
65.74
1-10 465.48 538.75 520.27 124.87 360 86.40 82.08
July-06 11-20 372.70 431.36 416.57 99.98 360 86.40 82.08
21-31 641.09 674.55 651.41 171.97 360 95.04 90.29
1-10 602.59 697.44 673.52 161.64 360 86.40 82.08
Aug-06 11-20 669.25 774.60 748.03 179.53 360 86.40 82.08
21-31 673.67 708.83 684.52 180.71 360 95.04 90.29
1-10 478.73 554.09 535.08 128.42 360 86.40 82.08
Sep-06 11-20 369.50 427.67 413.00 99.12 360 86.40 82.08
21-30 300.10 347.33 335.42 80.50 335 80.50 80.50
1-10 486.50 563.08 543.77 130.50 360 86.40 82.08
Oct-06 11-20 440.80 510.19 492.68 118.24 360 86.40 82.08
21-31 250.67 263.75 254.70 67.24 255 67.24 67.24
1-10 176.80 204.63 197.61 47.43 198 47.43 47.43
Nov-06 11-20 102.78 118.95 114.87 27.57 115 27.57 27.57
21-30 89.06 103.08 99.54 23.89 100 23.89 23.89
1-10 70.13 81.17 78.39 18.81 78 18.81 18.81
Dec-06 11-20 71.81 83.11 80.26 19.26 80 19.26 19.26
21-31 65.28 68.69 66.33 17.51 66 17.51 17.51
1-10 44.42 51.41 49.64 11.91 50 11.91 11.91
Jan-07 11-20 53.05 61.40 59.30 14.23 59 14.23 14.23
21-31 64.72 68.10 65.77 17.36 66 17.36 17.36
1-10 65.17 75.43 72.84 17.48 73 17.48 17.48
Feb-07 11-20 60.53 70.05 67.65 16.24 68 16.24 16.24
21-28 45.66 66.06 63.79 12.25 64 12.25 12.25
1-10 71.85 83.16 80.31 19.27 80 19.27 19.27
Mar-07 11-20 65.67 76.01 73.40 17.62 73 17.62 17.62
21-31 68.93 72.53 70.04 18.49 70 18.49 18.49
1-10 100.19 115.96 111.99 26.88 112 26.88 26.88
Apr-07 11-20 128.87 149.15 144.04 34.57 144 34.57 34.57
21-30 159.65 184.79 178.45 42.83 178 42.83 42.83
1-10 268.95 311.29 300.61 72.15 301 72.15 72.15
May-07 11-20 246.94 285.81 276.00 66.24 276 66.24 66.24
21-31 309.38 325.53 314.36 82.99 314 82.99 82.99
Total 8704.51 2334.97 1821.27 1777.21
Annual
L/F 57.75%
L/F monsoon
(March to Nov.)
70.55%
L/F non-monsoon (Dec
to Feb.)
18.66%
80

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
7-8
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
07
1-10
11-20
21-30
255.64
299.89
428.53
295.88
347.09
495.99
285.73
335.19
478.97
68.58
80.44
114.95
286
335
360
68.58
80.44
86.40
68.58
80.44
82.08
1-10 501.82 580.81 560.89 134.61 360 86.40 82.08
July-07 11-20 722.94 836.73 808.03 193.93 360 86.40 82.08
21-31 976.34 1027.29 992.05 261.90 360 95.04 90.29
1-10 285.06 329.93 318.61 76.47 319 76.47 76.47
Aug-07 11-20 364.06 421.36 406.91 97.66 360 86.40 82.08
21-31 370.02 389.33 375.98 99.26 360 95.04 90.29
1-10 258.97 299.74 289.46 69.47 289 69.47 69.47
Sep-07 11-20 315.90 365.63 353.08 84.74 353 84.74 84.74
21-30 364.32 421.67 407.21 97.73 360 86.40 82.08
1-10 330.61 382.66 369.53 88.69 360 86.40 82.08
Oct-07 11-20 173.86 201.23 194.32 46.64 194 46.64 46.64
21-31 153.78 161.81 156.26 41.25 156 41.25 41.25
1-10 127.61 147.70 142.63 34.23 143 34.23 34.23
Nov-07 11-20 139.79 161.80 156.25 37.50 156 37.50 37.50
21-30 126.54 146.46 141.44 33.95 141 33.95 33.95
1-10 122.53 141.82 136.95 32.87 137 32.87 32.87
Dec-07 11-20 83.62 96.78 93.46 22.43 93 22.43 22.43
21-31 75.93 79.89 77.15 20.37 77 20.37 20.37
1-10 79.19 91.65 88.51 21.24 89 21.24 21.24
Jan-08 11-20 74.11 85.77 82.83 19.88 83 19.88 19.88
21-31 88.11 92.70 89.52 23.63 90 23.63 23.63
1-10 88.14 102.01 98.51 23.64 99 23.64 23.64
Feb-08 11-20 65.74 76.08 73.47 17.63 73 17.63 17.63
21-29 61.46 79.04 76.33 16.49 76 16.49 16.49
1-10 88.30 102.20 98.69 23.69 99 23.69 23.69
Mar-08 11-20 81.95 94.85 91.60 21.98 92 21.98 21.98
21-31 114.41 120.38 116.25 30.69 116 30.69 30.69
1-10 147.08 170.23 164.39 39.45 164 39.45 39.45
Apr-08 11-20 153.40 177.55 171.46 41.15 171 41.15 41.15
21-30 114.70 132.75 128.20 30.77 128 30.77 30.77
1-10 257.96 298.57 288.33 69.20 288 69.20 69.20
May-08 11-20 394.67 456.79 441.13 105.87 360 86.40 82.08
21-31 633.22 666.27 643.42 169.86 360 95.04 90.29
Total 8920.21 2392.84 1918.30 1873.80
Annual
L/F 60.83%
L/F monsoon
(March to Nov.)
72.40%
L/F non-monsoon (Dec
to Feb.)
25.49%
81

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
8-9
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
08
1-10
11-20
21-30
973.75
1217.35
1091.44
1127.03
1408.97
1263.24
1088.37
1360.64
1219.91
261.21
326.55
292.78
360
360
360
86.40
86.40
86.40
82.08
82.08
82.08
1-10 1274.10 1474.65 1424.06 341.78 360 86.40 82.08
July-08 11-20 1405.98 1627.29 1571.47 377.15 360 86.40 82.08
21-31 1947.98 2049.64 1979.33 522.54 360 95.04 90.29
1-10 557.98 645.81 623.65 149.68 360 86.40 82.08
Aug-08 11-20 629.78 728.91 703.90 168.94 360 86.40 82.08
21-31 759.15 798.77 771.37 203.64 360 95.04 90.29
1-10 576.15 666.84 643.96 154.55 360 86.40 82.08
Sep-08 11-20 412.24 477.13 460.76 110.58 360 86.40 82.08
21-30 574.53 664.97 642.16 154.12 360 86.40 82.08
1-10 463.19 536.10 517.71 124.25 360 86.40 82.08
Oct-08 11-20 499.56 578.19 558.36 134.01 360 86.40 82.08
21-31 249.63 262.65 253.64 66.96 254 66.96 66.96
1-10 225.06 260.49 251.55 60.37 252 60.37 60.37
Nov-08 11-20 192.67 223.00 215.35 51.68 215 51.68 51.68
21-30 126.89 146.87 141.83 34.04 142 34.04 34.04
1-10 80.33 92.97 89.78 21.55 90 21.55 21.55
Dec-08 11-20 85.01 98.39 95.01 22.80 95 22.80 22.80
21-31 83.66 88.03 85.01 22.44 85 22.44 22.44
1-10 69.12 80.00 77.26 18.54 77 18.54 18.54
Jan-09 11-20 55.17 63.86 61.67 14.80 62 14.80 14.80
21-31 57.15 60.14 58.07 15.33 58 15.33 15.33
1-10 46.40 53.70 51.86 12.45 52 12.45 12.45
Feb-09 11-20 43.03 49.80 48.09 11.54 48 11.54 11.54
21-28 35.90 51.94 50.16 9.63 50 9.63 9.63
1-10 81.67 94.52 91.28 21.91 91 21.91 21.91
Mar-09 11-20 85.34 98.77 95.38 22.89 95 22.89 22.89
21-31 82.21 86.50 83.53 22.05 84 22.05 22.05
1-10 89.32 103.38 99.83 23.96 100 23.96 23.96
Apr-09 11-20 156.58 181.23 175.01 42.00 175 42.00 42.00
21-30 168.32 194.81 188.13 45.15 188 45.15 45.15
1-10 189.37 219.17 211.66 50.80 212 50.80 50.80
May-09 11-20 134.51 155.68 150.34 36.08 150 36.08 36.08
21-31 236.28 248.61 240.08 63.38 240 63.38 63.38
Total 14956.79 4012.14 1917.25 1855.91
Annual
L/F 60.80%
L/F monsoon
(March to Nov.)
74.42%
L/F non-monsoon (Dec
to Feb.)
19.17%
82

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
9-10
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
09
1-10
11-20
21-30
175.10
166.84
268.98
202.66
193.10
311.32
195.71
186.48
300.64
46.97
44.76
72.15
196
186
301
46.97
44.76
72.15
46.97
44.76
72.15
1-10 769.87 891.05 860.48 206.52 360 86.40 82.08
July-09 11-20 600.32 694.81 670.98 161.03 360 86.40 82.08
21-31 946.46 995.86 961.70 253.89 360 95.04 90.29
1-10 737.47 853.55 824.27 197.83 360 86.40 82.08
Aug-09 11-20 942.18 1090.48 1053.07 252.74 360 86.40 82.08
21-31 767.41 807.46 779.76 205.86 360 95.04 90.29
1-10 522.95 605.27 584.50 140.28 360 86.40 82.08
Sep-09 11-20 471.25 545.42 526.71 126.41 360 86.40 82.08
21-30 509.41 589.60 569.37 136.65 360 86.40 82.08
1-10 563.99 652.76 630.37 151.29 360 86.40 82.08
Oct-09 11-20 241.09 279.04 269.47 64.67 269 64.67 64.67
21-31 276.48 290.91 280.93 74.17 281 74.17 74.17
1-10 141.13 163.35 157.75 37.86 158 37.86 37.86
Nov-09 11-20 147.64 170.88 165.01 39.60 165 39.60 39.60
21-30 92.08 106.57 102.92 24.70 103 24.70 24.70
1-10 63.68 73.71 71.18 17.08 71 17.08 17.08
Dec-09 11-20 66.19 76.61 73.98 17.76 74 17.76 17.76
21-31 60.40 63.55 61.37 16.20 61 16.20 16.20
1-10 43.95 50.86 49.12 11.79 49 11.79 11.79
Jan-10 11-20 41.20 47.68 46.05 11.05 46 11.05 11.05
21-31 47.57 50.06 48.34 12.76 48 12.76 12.76
1-10 52.90 61.23 59.13 14.19 59 14.19 14.19
Feb-10 11-20 66.93 77.47 74.81 17.95 75 17.95 17.95
21-28 51.67 74.76 72.19 13.86 72 13.86 13.86
1-10 106.86 123.68 119.44 28.66 119 28.66 28.66
Mar-10 11-20 84.28 97.55 94.20 22.61 94 22.61 22.61
21-31 94.29 99.21 95.81 25.29 96 25.29 25.29
1-10 106.08 122.78 118.57 28.46 119 28.46 28.46
Apr-10 11-20 126.39 146.29 141.27 33.91 141 33.91 33.91
21-30 128.56 148.80 143.69 34.49 144 34.49 34.49
1-10 166.70 192.94 186.32 44.72 186 44.72 44.72
May-10 11-20 123.27 142.68 137.78 33.07 138 33.07 33.07
21-31 157.32 165.53 159.85 42.20 160 42.20 42.20
Total 9928.91 2663.42 1712.21 1668.15
Annual
L/F 54.29%
L/F monsoon
(March to Nov.)
66.48%
L/F non-monsoon (Dec to
Feb.)
17.06%
83

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
11-12
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
11
1-10
11-20
21-30
221.01
250.59
233.15
255.80
290.04
269.85
247.02
280.09
260.60
59.29
67.22
62.54
247
280
261
59.29
67.22
62.54
59.29
67.22
62.54
1-10 357.16 413.38 399.20 95.81 360 86.40 82.08
July-11 11-20 616.60 713.66 689.18 165.40 360 86.40 82.08
21-31 495.59 521.46 503.57 132.94 360 95.04 90.29
1-10 459.73 532.10 513.84 123.32 360 86.40 82.08
Aug-11 11-20 502.93 582.10 562.13 134.91 360 86.40 82.08
21-31 912.93 960.57 927.62 244.89 360 95.04 90.29
1-10 783.91 907.31 876.18 210.28 360 86.40 82.08
Sep-11 11-20 858.30 993.40 959.33 230.24 360 86.40 82.08
21-30 687.12 795.28 768.00 184.32 360 86.40 82.08
1-10 575.35 665.92 643.07 154.34 360 86.40 82.08
Oct-11 11-20 218.28 252.64 243.97 58.55 244 58.55 58.55
21-31 225.50 237.27 229.13 60.49 229 60.49 60.49
1-10 148.05 171.35 165.47 39.71 165 39.71 39.71
Nov-11 11-20 126.92 146.90 141.86 34.05 142 34.05 34.05
21-30 115.11 133.23 128.66 30.88 129 30.88 30.88
1-10 77.84 90.09 87.00 20.88 87 20.88 20.88
Dec-11 11-20 91.18 105.53 101.91 24.46 102 24.46 24.46
21-31 88.55 93.17 89.98 23.75 90 23.75 23.75
1-10 92.71 107.30 103.62 24.87 104 24.87 24.87
Jan-12 11-20 93.36 108.06 104.35 25.04 104 25.04 25.04
21-31 97.11 102.18 98.67 26.05 99 26.05 26.05
1-10 79.97 92.55 89.38 21.45 89 21.45 21.45
Feb-12 11-20 80.80 93.52 90.31 21.68 90 21.68 21.68
21-29 66.75 85.84 82.89 17.91 83 17.91 17.91
1-10 85.45 98.90 95.51 22.92 96 22.92 22.92
Mar-12 11-20 76.69 88.76 85.72 20.57 86 20.57 20.57
21-31 96.85 101.90 98.41 25.98 98 25.98 25.98
1-10 137.77 159.46 153.99 36.96 154 36.96 36.96
Apr-12 11-20 158.86 183.86 177.56 42.61 178 42.61 42.61
21-30 158.45 183.40 177.10 42.51 177 42.51 42.51
1-10 279.37 323.34 312.25 74.94 312 74.94 74.94
May-12 11-20 240.07 277.86 268.33 64.40 268 64.40 64.40
21-31 148.22 155.95 150.60 39.76 151 39.76 39.76
Total 9938.23 2665.92 1870.74 1826.68
Annual
L/F 59.32%
L/F monsoon
(March to Nov.)
70.06%
L/F non-monsoon (Dec
to Feb.)
26.50%
84

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
12-13
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
12
1-10
11-20
21-30
296.72
360.90
515.65
343.43
417.71
596.81
331.65
403.38
576.34
79.60
96.81
138.32
332
360
360
79.60
86.40
86.40
79.60
82.08
82.08
1-10 611.79 708.09 683.80 164.11 360 86.40 82.08
July-12 11-20 488.16 565.00 545.62 130.95 360 86.40 82.08
21-31 879.69 925.59 893.84 235.97 360 95.04 90.29
1-10 371.34 429.79 415.05 99.61 360 86.40 82.08
Aug-12 11-20 504.43 583.84 563.81 135.31 360 86.40 82.08
21-31 981.52 1032.75 997.32 263.29 360 95.04 90.29
1-10 674.14 780.26 753.49 180.84 360 86.40 82.08
Sep-12 11-20 712.43 824.58 796.29 191.11 360 86.40 82.08
21-30 525.34 608.04 587.18 140.92 360 86.40 82.08
1-10 304.49 352.42 340.33 81.68 340 81.68 81.68
Oct-12 11-20 338.97 392.32 378.86 90.93 360 86.40 82.08
21-31 188.74 198.59 191.78 50.63 192 50.63 50.63
1-10 104.33 120.75 116.61 27.99 117 27.99 27.99
Nov-12 11-20 98.90 114.47 110.54 26.53 111 26.53 26.53
21-30 81.06 93.82 90.60 21.74 91 21.74 21.74
1-10 88.87 102.86 99.34 23.84 99 23.84 23.84
Dec-12 11-20 68.06 78.77 76.07 18.26 76 18.26 18.26
21-31 66.61 70.09 67.69 17.87 68 17.87 17.87
1-10 45.81 53.02 51.20 12.29 51 12.29 12.29
Jan-13 11-20 46.16 53.42 51.59 12.38 52 12.38 12.38
21-31 56.28 59.21 57.18 15.10 57 15.10 15.10
1-10 61.29 70.94 68.51 16.44 69 16.44 16.44
Feb-13 11-20 45.64 52.82 51.01 12.24 51 12.24 12.24
21-28 54.39 78.70 76.00 14.59 76 14.59 14.59
1-10 87.29 101.03 97.56 23.41 98 23.41 23.41
Mar-13 11-20 113.27 131.10 126.60 30.38 127 30.38 30.38
21-31 125.40 131.94 127.41 33.64 127 33.64 33.64
1-10 139.92 161.94 156.39 37.53 156 37.53 37.53
Apr-13 11-20 135.01 156.26 150.90 36.22 151 36.22 36.22
21-30 150.22 173.86 167.90 40.30 168 40.30 40.30
1-10 173.67 201.00 194.11 46.59 194 46.59 46.59
May-13 11-20 166.69 192.93 186.31 44.71 186 44.71 44.71
21-31 375.48 395.08 381.53 100.72 360 95.04 90.29
Total 10038.68 2692.86 1873.08 1815.62
Annual
L/F 59.39%
L/F monsoon
(March to Nov.)
72.81%
L/F non-monsoon (Dec
to Feb.)
18.39%
85

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
13-14
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
13
1-10
11-20
21-30
282.99
266.80
480.99
327.54
308.80
556.71
316.30
298.21
537.61
75.91
71.57
129.03
316
298
360
75.91
71.57
86.40
75.91
71.57
82.08
1-10 423.13 489.73 472.93 113.50 360 86.40 82.08
July-13 11-20 663.76 768.24 741.89 178.05 360 86.40 82.08
21-31 577.57 607.71 586.86 154.93 360 95.04 90.29
1-10 825.79 955.77 922.99 221.52 360 86.40 82.08
Aug-13 11-20 1078.15 1247.86 1205.06 289.21 360 86.40 82.08
21-31 755.37 794.79 767.53 202.63 360 95.04 90.29
1-10 350.19 405.31 391.41 93.94 360 86.40 82.08
Sep-13 11-20 327.45 379.00 365.99 87.84 360 86.40 82.08
21-30 261.09 302.19 291.82 70.04 292 70.04 70.04
1-10 493.28 570.93 551.34 132.32 360 86.40 82.08
Oct-13 11-20 214.30 248.04 239.53 57.49 240 57.49 57.49
21-31 195.34 205.54 198.49 52.40 198 52.40 52.40
1-10 143.43 166.01 160.31 38.48 160 38.48 38.48
Nov-13 11-20 136.28 157.73 152.32 36.56 152 36.56 36.56
21-30 100.61 116.45 112.45 26.99 112 26.99 26.99
1-10 67.98 78.68 75.98 18.24 76 18.24 18.24
Dec-13 11-20 70.47 81.56 78.76 18.90 79 18.90 18.90
21-31 75.31 79.24 76.52 20.20 77 20.20 20.20
1-10 55.28 63.98 61.78 14.83 62 14.83 14.83
Jan-14 11-20 45.21 52.32 50.53 12.13 51 12.13 12.13
21-31 47.22 49.68 47.98 12.67 48 12.67 12.67
1-10 56.98 65.95 63.69 15.29 64 15.29 15.29
Feb-14 11-20 44.81 51.86 50.08 12.02 50 12.02 12.02
21-28 45.45 65.75 63.50 12.19 63 12.19 12.19
1-10 85.23 98.65 95.26 22.86 95 22.86 22.86
Mar-14 11-20 115.83 134.06 129.46 31.07 129 31.07 31.07
21-31 109.25 114.95 111.00 29.31 111 29.31 29.31
1-10 130.92 151.52 146.33 35.12 146 35.12 35.12
Apr-14 11-20 175.02 202.57 195.62 46.95 196 46.95 46.95
21-30 149.22 172.71 166.78 40.03 167 40.03 40.03
1-10 188.13 217.75 210.28 50.47 210 50.47 50.47
May-14 11-20 186.74 216.13 208.72 50.09 209 50.09 50.09
21-31 201.51 212.03 204.75 54.05 205 54.05 54.05
Total 9427.09 2528.81 1807.11 1763.05
Annual
L/F 57.30%
L/F monsoon
(March to Nov.)
70.31%
L/F non-monsoon (Dec
to Feb.)
17.55%
86

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
14-15
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10 433.24 501.43 484.23 116.22 360 86.40 82.08
11-20 739.36 855.74 826.39 198.33 360 86.40 82.08
June-
14
July-14
Aug-14
Sep-14
Oct-14
Nov-14
Dec-14
Jan-15
Feb-15
Mar-15
Apr-15
May-15
21-30 988.73 1144.36 1105.10 265.23 360 86.40 82.08
1-10 615.75 712.68 688.23 165.18 360 86.40 82.08
11-20 727.23 841.70 812.83 195.08 360 86.40 82.08
21-31 979.13 1030.23 994.89 262.65 360 95.04 90.29
1-10 633.41 733.12 707.97 169.91 360 86.40 82.08
11-20 671.70 777.43 750.76 180.18 360 86.40 82.08
21-31 698.72 735.18 709.96 187.43 360 95.04 90.29
1-10 573.43 663.69 640.92 153.82 360 86.40 82.08
11-20 417.24 482.91 466.35 111.92 360 86.40 82.08
21-30 383.14 443.45 428.24 102.78 360 86.40 82.08
1-10 469.38 543.27 524.63 125.91 360 86.40 82.08
11-20 238.98 276.60 267.11 64.11 267 64.11 64.11
21-31 154.29 162.34 156.77 41.39 157 41.39 41.39
1-10 146.79 169.90 164.07 39.38 164 39.38 39.38
11-20 125.63 145.41 140.42 33.70 140 33.70 33.70
21-30 90.26 104.46 100.88 24.21 101 24.21 24.21
1-10 94.20 109.03 105.29 25.27 105 25.27 25.27
11-20 105.12 121.67 117.50 28.20 117 28.20 28.20
21-31 100.39 105.63 102.01 26.93 102 26.93 26.93
1-10 95.32 110.32 106.54 25.57 107 25.57 25.57
11-20 86.16 99.72 96.30 23.11 96 23.11 23.11
21-31 90.11 94.81 91.56 24.17 92 24.17 24.17
1-10 107.17 124.04 119.79 28.75 120 28.75 28.75
11-20 67.28 77.87 75.20 18.05 75 18.05 18.05
21-28 64.51 93.32 90.12 17.30 90 17.30 17.30
1-10 95.09 110.06 106.28 25.51 106 25.51 25.51
11-20 104.59 121.05 116.90 28.06 117 28.06 28.06
21-31 99.99 105.21 101.60 26.82 102 26.82 26.82
1-10 97.18 112.48 108.62 26.07 109 26.07 26.07
11-20 94.58 109.47 105.71 25.37 106 25.37 25.37
21-30 91.45 105.84 102.21 24.53 102 24.53 24.53
1-10 211.61 244.92 236.51 56.76 237 56.76 56.76
11-20 181.67 210.27 203.06 48.73 203 48.73 48.73
21-31 122.69 129.10 124.67 32.91 125 32.91 32.91
Total 10995.51 2949.53 1855.38 1798.35
Annual
L/F 58.83%
L/F monsoon
(March to Nov.)
68.94%
L/F non-monsoon (Dec
to Feb.)
27.95%
87

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
15-16
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
15
1-10
11-20
21-30
134.70
252.30
384.61
155.90
292.02
445.15
150.55
282.00
429.88
36.13
67.68
103.17
151
282
360
36.13
67.68
86.40
36.13
67.68
82.08
1-10 842.98 975.67 942.20 226.13 360 86.40 82.08
July-15 11-20 788.99 913.19 881.86 211.65 360 86.40 82.08
21-31 761.68 801.43 773.94 204.32 360 95.04 90.29
1-10 692.20 801.15 773.67 185.68 360 86.40 82.08
Aug-15 11-20 623.46 721.60 696.84 167.24 360 86.40 82.08
21-31 600.37 631.70 610.03 161.05 360 95.04 90.29
1-10 298.59 345.59 333.73 80.10 334 80.10 80.10
Sep-15 11-20 329.33 381.17 368.09 88.34 360 86.40 82.08
21-30 316.83 366.70 354.12 84.99 354 84.99 84.99
1-10 259.75 300.63 290.32 69.68 290 69.68 69.68
Oct-15 11-20 194.57 225.20 217.47 52.19 217 52.19 52.19
21-31 188.38 198.21 191.41 50.53 191 50.53 50.53
1-10 188.34 217.98 210.51 50.52 211 50.52 50.52
Nov-15 11-20 154.97 179.36 173.21 41.57 173 41.57 41.57
21-30 107.23 124.11 119.85 28.76 120 28.76 28.76
1-10 116.10 134.37 129.76 31.14 130 31.14 31.14
Dec-15 11-20 82.43 95.40 92.13 22.11 92 22.11 22.11
21-31 76.57 80.57 77.80 20.54 78 20.54 20.54
1-10 53.23 61.61 59.50 14.28 59 14.28 14.28
Jan-16 11-20 58.44 67.64 65.32 15.68 65 15.68 15.68
21-31 70.63 74.32 71.77 18.95 72 18.95 18.95
1-10 85.57 99.04 95.64 22.95 96 22.95 22.95
Feb-16 11-20 83.45 96.59 93.27 22.39 93 22.39 22.39
21-29 81.04 104.22 100.65 21.74 101 21.74 21.74
1-10 101.07 116.98 112.96 27.11 113 27.11 27.11
Mar-16 11-20 79.37 91.86 88.71 21.29 89 21.29 21.29
21-31 85.10 89.54 86.47 22.83 86 22.83 22.83
1-10 141.28 163.52 157.91 37.90 158 37.90 37.90
Apr-16 11-20 117.21 135.66 131.00 31.44 131 31.44 31.44
21-30 180.00 208.33 201.19 48.28 201 48.28 48.28
1-10 218.72 253.14 244.46 58.67 244 58.67 58.67
May-16 11-20 162.90 188.54 182.07 43.70 182 43.70 43.70
21-31 242.41 255.06 246.31 65.03 246 65.03 65.03
Total 9154.77 2455.76 1816.66 1781.23
Annual
L/F 57.61%
L/F monsoon
(March to Nov.)
68.47%
L/F non-monsoon (Dec
to Feb.)
24.41%
88

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
16-17
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10 545.64 631.53 609.87 146.37 360 86.40 82.08
11-20 379.62 439.38 424.31 101.83 360 86.40 82.08
June-
16
July-16
Aug-16
Sep-16
Oct-16
Nov-16
Dec-16
Jan-17
Feb-17
Mar-17
Apr-17
May-17
21-30 382.89 443.16 427.96 102.71 360 86.40 82.08
1-10 333.12 385.55 372.33 89.36 360 86.40 82.08
11-20 276.51 320.03 309.06 74.17 309 74.17 74.17
21-31 339.47 357.19 344.94 91.06 345 91.06 91.06
1-10 485.44 561.85 542.58 130.22 360 86.40 82.08
11-20 745.67 863.04 833.44 200.02 360 86.40 82.08
21-31 895.15 941.86 909.55 240.12 360 95.04 90.29
1-10 602.19 696.98 673.08 161.54 360 86.40 82.08
11-20 471.06 545.20 526.50 126.36 360 86.40 82.08
21-30 623.14 721.23 696.49 167.16 360 86.40 82.08
1-10 370.91 429.30 414.57 99.50 360 86.40 82.08
11-20 227.52 263.33 254.30 61.03 254 61.03 61.03
21-31 177.31 186.56 180.16 47.56 180 47.56 47.56
1-10 165.68 191.76 185.18 44.44 185 44.44 44.44
11-20 148.98 172.43 166.52 39.96 167 39.96 39.96
21-30 113.04 130.83 126.34 30.32 126 30.32 30.32
1-10 77.17 89.32 86.26 20.70 86 20.70 20.70
11-20 62.93 72.83 70.33 16.88 70 16.88 16.88
21-31 71.48 75.21 72.63 19.17 73 19.17 19.17
1-10 50.35 58.28 56.28 13.51 56 13.51 13.51
11-20 39.96 46.25 44.66 10.72 45 10.72 10.72
21-31 48.92 51.48 49.71 13.12 50 13.12 13.12
1-10 56.88 65.83 63.57 15.26 64 15.26 15.26
11-20 62.99 72.91 70.41 16.90 70 16.90 16.90
21-28 50.53 73.11 70.60 13.56 71 13.56 13.56
1-10 68.29 79.04 76.33 18.32 76 18.32 18.32
11-20 75.96 87.91 84.90 20.37 85 20.37 20.37
21-31 119.25 125.47 121.17 31.99 121 31.99 31.99
1-10 195.56 226.34 218.58 52.46 219 52.46 52.46
11-20 164.69 190.61 184.07 44.18 184 44.18 44.18
21-30 212.31 245.73 237.30 56.95 237 56.95 56.95
1-10 218.36 252.73 244.06 58.57 244 58.57 58.57
11-20 170.91 197.81 191.02 45.85 191 45.85 45.85
21-31 143.37 150.85 145.68 38.46 146 38.46 38.46
Total 9173.26 2460.72 1854.57 1806.62
Annual
L/F 58.81%
L/F monsoon
(March to Nov.)
72.17%
L/F non-monsoon (Dec
to Feb.)
17.98%
89

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
17-18
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
17
1-10
11-20
21-30
126.29
161.87
241.65
146.16
187.34
279.69
141.15
180.92
270.09
33.88
43.42
64.82
141
181
270
33.88
43.42
64.82
33.88
43.42
64.82
1-10 273.86 316.97 306.09 73.46 306 73.46 73.46
July-17 11-20 530.15 613.60 592.55 142.21 360 86.40 82.08
21-31 725.58 763.45 737.26 194.64 360 95.04 90.29
1-10 729.16 843.94 814.99 195.60 360 86.40 82.08
Aug-17 11-20 968.00 1120.37 1081.94 259.67 360 86.40 82.08
21-31 1272.71 1339.13 1293.19 341.40 360 95.04 90.29
1-10 964.54 1116.37 1078.07 258.74 360 86.40 82.08
Sep-17 11-20 682.39 789.80 762.71 183.05 360 86.40 82.08
21-30 745.79 863.18 833.57 200.06 360 86.40 82.08
1-10 338.93 392.29 378.83 90.92 360 86.40 82.08
Oct-17 11-20 369.78 427.98 413.30 99.19 360 86.40 82.08
21-31 319.62 336.30 324.77 85.74 325 85.74 85.74
1-10 173.26 200.53 193.65 46.48 194 46.48 46.48
Nov-17 11-20 104.23 120.63 116.49 27.96 116 27.96 27.96
21-30 71.74 83.03 80.19 19.24 80 19.24 19.24
1-10 72.42 83.82 80.94 19.43 81 19.43 19.43
Dec-17 11-20 60.97 70.56 68.14 16.35 68 16.35 16.35
21-31 69.07 72.67 70.18 18.53 70 18.53 18.53
1-10 62.71 72.59 70.10 16.82 70 16.82 16.82
Jan-18 11-20 63.88 73.94 71.40 17.14 71 17.14 17.14
21-31 66.62 70.10 67.70 17.87 68 17.87 17.87
1-10 69.43 80.36 77.60 18.62 78 18.62 18.62
Feb-18 11-20 49.99 57.85 55.87 13.41 56 13.41 13.41
21-28 59.25 85.71 82.77 15.89 83 15.89 15.89
1-10 101.24 117.17 113.15 27.16 113 27.16 27.16
Mar-18 11-20 83.88 97.08 93.75 22.50 94 22.50 22.50
21-31 80.38 84.58 81.67 21.56 82 21.56 21.56
1-10 108.90 126.05 121.72 29.21 122 29.21 29.21
Apr-18 11-20 103.55 119.85 115.73 27.78 116 27.78 27.78
21-30 153.70 177.89 171.79 41.23 172 41.23 41.23
1-10 163.72 189.50 182.99 43.92 183 43.92 43.92
May-18 11-20 120.47 139.43 134.65 32.32 135 32.32 32.32
21-31 108.37 114.02 110.11 29.07 110 29.07 29.07
Total 10398.07 2789.27 1705.08 1661.02
Annual
L/F 54.07%
L/F monsoon
(March to Nov.)
65.28%
L/F non-monsoon (Dec
to Feb.)
19.81%
90

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
POWER POTENTIAL STUDY FOR YEAR
18-19
Installed
Capacity
360 Net Head 107 Efficiency 92%
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
June-
18
1-10
11-20
21-30
115.84
151.88
292.56
134.07
175.79
338.61
129.48
169.76
327.00
31.07
40.74
78.48
129
170
327
31.07
40.74
78.48
31.07
40.74
78.48
1-10 343.80 397.91 384.26 92.22 360 86.40 82.08
July-18 11-20 654.00 756.95 730.98 175.44 360 86.40 82.08
21-31 647.43 681.22 657.85 173.67 360 95.04 90.29
1-10 404.89 468.63 452.55 108.61 360 86.40 82.08
Aug-18 11-20 374.32 433.24 418.37 100.41 360 86.40 82.08
21-31 416.68 438.42 423.38 111.77 360 95.04 90.29
1-10 385.73 446.45 431.14 103.47 360 86.40 82.08
Sep-18 11-20 355.99 412.03 397.89 95.49 360 86.40 82.08
21-30 279.84 323.88 312.77 75.07 313 75.07 75.07
1-10 395.29 457.51 441.82 106.04 360 86.40 82.08
Oct-18 11-20 395.79 458.09 442.38 106.17 360 86.40 82.08
21-31 259.80 273.36 263.99 69.69 264 69.69 69.69
1-10 141.23 163.46 157.85 37.88 158 37.88 37.88
Nov-18 11-20 89.13 103.16 99.62 23.91 100 23.91 23.91
21-30 77.08 89.22 86.16 20.68 86 20.68 20.68
1-10 92.01 106.50 102.84 24.68 103 24.68 24.68
Dec-18 11-20 81.73 94.59 91.35 21.92 91 21.92 21.92
21-31 84.35 88.76 85.71 22.63 86 22.63 22.63
1-10 65.01 75.25 72.66 17.44 73 17.44 17.44
Jan-19 11-20 65.47 75.77 73.18 17.56 73 17.56 17.56
21-31 66.84 70.33 67.91 17.93 68 17.93 17.93
1-10 81.40 94.21 90.98 21.83 91 21.83 21.83
Feb-19 11-20 88.22 102.11 98.61 23.67 99 23.67 23.67
21-28 74.59 107.91 104.21 20.01 104 20.01 20.01
1-10 83.23 96.33 93.03 22.33 93 22.33 22.33
Mar-19 11-20 110.21 127.56 123.18 29.56 123 29.56 29.56
21-31 153.48 161.49 155.95 41.17 156 41.17 41.17
1-10 171.25 198.21 191.41 45.94 191 45.94 45.94
Apr-19 11-20 235.29 272.33 262.99 63.12 263 63.12 63.12
21-30 170.14 196.93 190.17 45.64 190 45.64 45.64
1-10 271.18 313.86 303.10 72.74 303 72.74 72.74
May-19 11-20 358.46 414.88 400.65 96.16 360 86.40 82.08
21-31 292.99 308.28 297.71 78.59 298 78.59 78.59
Total 8327.15 2233.75 1931.97 1883.59
Annual
L/F 61.26%
L/F monsoon
(March to Nov.)
73.41%
L/F non-monsoon (Dec
to Feb.)
24.13%
91

Installed
Capacity
POWER POTENTIAL STUDY FOR YEAR
19-20
360 Net Head 107 Efficiency 92%
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Month DISCHARGE
RESTRICTED RESTRICTED
DISCHARGE UNRESTRICTED UNRESTRICTED
95% m/c
POWER ENERGY
( MCum) ( Qmecs) POWER ( MW) ENERGY ( MU)
Availability
( 360MW) ( MU)
1-10 528.21 611.35 590.38 141.69 360 86.40 82.08
11-20 808.83 936.14 904.03 216.97 360 86.40 82.08
June-
19
July-19
Aug-19
Sep-19
Oct-19
Nov-19
Dec-19
Jan-20
Feb-20
Mar-20
Apr-20
May-20
21-30 819.88 948.94 916.39 219.93 360 86.40 82.08
1-10 965.63 1117.63 1079.29 259.03 360 86.40 82.08
11-20 1169.90 1354.05 1307.60 313.82 360 86.40 82.08
21-31 1694.17 1782.59 1721.44 454.46 360 95.04 90.29
1-10 485.71 562.16 542.88 130.29 360 86.40 82.08
11-20 543.17 628.67 607.10 145.70 360 86.40 82.08
21-31 960.97 1011.12 976.43 257.78 360 95.04 90.29
1-10 625.13 723.53 698.71 167.69 360 86.40 82.08
11-20 507.62 587.53 567.37 136.17 360 86.40 82.08
21-30 341.17 394.87 381.33 91.52 360 86.40 82.08
1-10 300.22 347.47 335.56 80.53 336 80.53 80.53
11-20 300.89 348.26 336.31 80.71 336 80.71 80.71
21-31 302.81 318.61 307.68 81.23 308 81.23 81.23
1-10 137.76 159.44 153.97 36.95 154 36.95 36.95
11-20 83.04 96.11 92.82 22.28 93 22.28 22.28
21-30 82.12 95.04 91.78 22.03 92 22.03 22.03
1-10 100.33 116.13 112.14 26.91 112 26.91 26.91
11-20 71.97 83.30 80.44 19.31 80 19.31 19.31
21-31 68.37 71.94 69.47 18.34 69 18.34 18.34
1-10 56.91 65.87 63.61 15.27 64 15.27 15.27
11-20 46.75 54.11 52.26 12.54 52 12.54 12.54
21-31 49.02 51.58 49.81 13.15 50 13.15 13.15
1-10 41.67 48.22 46.57 11.18 47 11.18 11.18
11-20 41.57 48.11 46.46 11.15 46 11.15 11.15
21-29 47.85 61.54 59.42 12.84 59 12.84 12.84
1-10 50.92 58.93 56.91 13.66 57 13.66 13.66
11-20 60.08 69.54 67.15 16.12 67 16.12 16.12
21-31 73.79 77.64 74.98 19.79 75 19.79 19.79
1-10 88.50 102.43 98.91 23.74 99 23.74 23.74
11-20 91.40 105.79 102.16 24.52 102 24.52 24.52
21-30 131.75 152.49 147.26 35.34 147 35.34 35.34
1-10 171.63 198.65 191.83 46.04 192 46.04 46.04
11-20 171.68 198.70 191.89 46.05 192 46.05 46.05
21-31 243.33 256.03 247.25 65.27 247 65.27 65.27
Total 12264.77 3290.01 1809.03 1756.33
Annual
L/F 57.36%
L/F monsoon
(March to Nov.)
70.22%
L/F non-monsoon (Dec
to Feb.)
18.09%
92

8.0 INTRODUCTION
CHAPTER - VIII
POWER EVACUATION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Nalo H.E. Project is envisaged for the installation of four generating
units of 90 MW each, operating under a rated net head of 107 m in
Surface type power house. The generation voltage is proposed to be
11 KV. This voltage will be stepped up to 400 KV voltage level through
single-phase Generator step-up transformers. The Generator step-up
transformers will be connected to 400 KV outdoor conventional switchyard
through overhead conductor. The power from Nalo H.E. Project would be
fed to the North-Eastern Grid to be ultimately connected to the National
Grid through EHV/HVDC transmission lines. Provision of two outgoing
bays has been kept in Switchyard for 360 MW power evacuation from this
project.
8.1 EXISTING POWER EVACUATION FACILITIES
Power system is controlled by the Electricity boards/
Departments/Corporations of the states of Assam, Meghalaya, Arunachal
Pradesh, Nagaland, Manipur, Mizoram and Tripura.
Power System Networks of PSUs located in the region are two 400KV line
going to Balipara from Dikrong (Ranga Nadi) power station and two
132KV line are also emanating from Dikrong Switchyard and feeding to
Along and Nirjuli areas.
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8.2 PROPOSED EVACUATION ARRANGEMENT
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
It is proposed to provide two outgoing bays for evacuating power at 400
KV level from Nalo H.E. Project. This power would be pooled to the
pooling point planned at Daporijo through one No. 400 KV Double circuit
transmission line with Twin moose conductor (Plate 8.1). The power from
Oju-I, Oju-II, Niare & Naba H. E. Projects would also be pooled at Daporijo
pooling point. The power from Daporijo pooling point would be ultimately
pooled directly through HVDC Link to the National Grid. Further, it is to
mention that the cost of the transmission network of 75 km distance from
Nalo H. E. Project to Daporijo pooling point & other end equipment at
Daporijo pooling point have been considered. The Power evacuation
system for Subansiri Basin is enclosed herewith for reference (Plate 8.2).
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9.0 INTRODUCTION
General
CHAPTER- IX
ENVIRONMENTAL ASPECTS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The height of the concrete gravity dam would be 125 m above the deepest
foundation level on river Subansiri/ Singit in Arunachal Pradesh. The
surface powerhouse will have a generation capacity of 360 MW.
Location
The dam site is proposed to be located 1.6 km u/s of Ledi Ishi Nallah of
Upper Subansiri district in Arunachal Pradesh. The nearest BG railhead is
Nagaon in Assam and the nearest airport is at Lilabari (North Lakhimpur).
9.1 PHYSICAL ENVIRONMENT
9.1.1 Climate/Meteorology
The climate in the entire region is humid and fairly uniform. Thick mist
formation is a feature during the early morning hours which completely
envelope the area and block the sun. Temperature variation is observed
with increasing altitude. It varies between 39.5° C and 11.5° C as observed
at Menga. The relative humidity ranges between 94% and 62%. Premonsoon
rains occur from mid-February. The average annual rainfall is
about 2810 mm.
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9.1.2 Topography
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
It is an enormous virgin terrain of rugged mountains, covered by insatiable
forests fed by copious rains. A number of hilly streams intersect the region
with gradual altitudinal variation.
9.1.3 Soil
The general and average soil character of cultivable land in the district is
mainly alluvial and composed of a mixture of sand (coarse to fine) and clay
in varying proportions. Soils in the area are results of degradation and
weathering of rocks as well as depositional features in the form of river
terraces. The soil on the slopes is mainly composed of silt and support
good vegetation. The clayey soils formed on river terrace due to river
deposits are fertile and has been developed into paddy fields by the local
inhabitants.
9.1.4 Geology
The entire project is located in broadly two rock types i.e Biotite gneiss and
Biotite Schist. The dam site has been chosen in a relatively straight stretch
of the river where rock is exposed on left bank as steep rocky escarpment
but right bank is covered under overburden and vegetation. From regional
geological assessment it is expected that dam, diversion tunnel & desilting
chambers will be housed in biotite gneiss of Gelensiniak Formation
whereas powerhouse complex and most of the part of HRT will be housed
in Biotite Schist of Nacho Formation.
96

9.1.5 Seismicity
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The entire northeast region has been classified in zone-V of the seismic
zoning map of India. Though MBT and MCT associated with the tectonic
activity are located at a far distance from the project area and the proposed
project area has not experienced any major earthquake shocks in the
recent past, adequate site specific seismic design parameter will have to be
determined for safe design of the civil structures.
9.1.6 Catchment Area
The Nalo basin lies between longitude 91° 45’E & 93° 49’E and between
latitude 27° 50’N & 29° 00’ N. The total catchment area upto the proposed
dam site is about 14500 sq km. The vast stretch of the catchment
possesses mainly sub-tropical forests, which is evergreen and dense in
nature. The permanent snow cover has been assumed above an elevation
of 4500 m.
9.1.7 Drainage Pattern
Subansiri is a major right bank tributary of river Brahmaputra. It originates
in Tibet beyond the Great Himalayan range (Central Himalaya) at an
altitude of around 5340 m. Several mountain streams or rather a big “Chu”
family of streams drains into the main valley. The principal stream
belonging to this “Chu” group is Nye Chu, which may be considered as the
main source of river Subansiri originating from the snow clad peaks of
Krakang, Shaota, Baru and Mata (EL 5389 m). Nye Chu is then joined by
another stream Laro Chu near Chayal thereby taking the name of Chayal
Chu.
After crossing the international boundary as the river approaches the Miri
Hills in Arunachal Pradesh, it runs in an unexplored valley. The course of
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
the main river and its tributaries are more or less marked on conjectural
lines rather than by accurate mapping. In its early reaches as the river
gathers more and more torrents in the Himalayas, it rushes through deep
gorges, far below the snow-tipped mountain peaks.
9.1.8 Land Use Pattern
About 740 ha of land are going to be acquired for the project out of which
about 285 ha are private land and 455 ha is falling under forestland. About
300 ha would come under submergence out of which 150 ha falls under
private land and another 150 ha under forest land category. The land use
pattern of the area is studied using satellite data. These studies have been
carried out through NRSA, Hyderabad who would use IRS 1C PAN + LISS
III merged satellite data.
Based on the analysis of satellite data and other available
ancillary information, the following outputs were generated by NRSA
(Annexure 9.1):
Map 1 (a) Shows IRS 1 C PAN + LISS III merged satellite image of 26 th
December, 2002 on 1:50,000 scale covering 7 km radius from the dam site
overlaid with FRL , location of dam site and power house.
Map 1(b) Shows satellite derived landuse- landcover map on 1:50,000
scale covering 7 km radius from the dam site overlaid with FRL , location of
dam site and power house. Land use /land cover map shows the following
categories: Forest (High and Medium Dense Forest), Agricultural Land,
Open Scrub, Barren and Rock Outcrop, Snow, River Course/ Dry River
Bed.
Map 1(c) Shows the landuse- landcover classes and their corresponding
area statistics in hectares within the submergence area on 1:25000 scale
overlaid with FRL , location of dam site and power house.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Map 1 (d) Shows the location of the National parks / Wildlife Sanctuaries
vis-à-vis the location of the dam/ Power House and 7 km radius area
around the dam site.
Following broad conclusion can be drawn from studies conducted by
NRSA
(i) Total area under submergence at proposed FRL of 765 m. (above
MSL) is estimated to be 283.80 ha ( Table.9.1).
(ii) It is observed that vegetation cover is mostly dominated by forest
category which is 146 ha ( 51% of the submergence area ). Entire
forest vegetation is classified as high and medium dense forest in the
submergence area.
Table 9.1
Landuse-landcover Information within the Submergence Area
S.No Landuse-landcover
Category
Area under
submergence (Ha)
% of the total
submergence area
1 High Dense Forest 118.36 41.71
2. Medium Dense Forest 27.49 9.69
3. Low Dense Forest Nil Nil
4. Open Scrub 56.78 20.01
5. Barren / Rock Outcrop 4.10 1.44
6. Snow Nil Nil
7. Agricultural Land 1.14 0.40
8. Human Settlement 0.49 0.17
9. River Course including dry
river bed
75.44 26.58
Total 283.80 100.00
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
(iii) Submergence of forest vegetation (High dense and Medium dense)
may be of some immediate concern which needs to be rehabilitated
with alternate afforestation measures within the vicinity of the dam
site when the project scheme is taken up for implementation.
(iv) There is very little 1.14 ha of (Insignificant) agricultural area present
within the proposed submergence area which is a positive sign to
develop the proposed hydropower site.
Table 9.2
Landuse-landcover Information within the 7 Km Radius from
the Dam site at Nalo
S.No Landuse-landcover
Category
Total Area ( ha)
% of the total
area
1 High Dense Forest 12523.73 81.35
2. Medium Dense Forest 1585.85 10.30
3. Low Dense Forest Nil Nil
4. Open Scrub 980.42 6.37
5. Barren / Rock Outcrop 80.17 0.52
6. Snow 7.24 0.05
7. Agricultural Land 33.39 0.22
8. Human Settlement 13.46 0.09
9. River Course including dry
river bed
169.74
1.10
Total area 15394.00 100.00
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
(v) Open scrub land is the next dominant land use – land cover category
after the forest and constitutes 20% of the submergence area. This is
followed by Barren / Rock outcrop land which is 1.44%.
(vi) There are no surface water bodies other than the river course. The
area under river course including dry river bed is estimated to be
75.44 ha, which constitutes 27% of the total submergence area.
(vii) It is also observed that the submergence area at EL + 765 m (FRL)
above MSL is likely to affect (Inundate) few isolated settlements.
Hence, a close look at the ground is required to assess the exact
impact.
(viii) Since 7 Km radius around the dam site was considered as the area
of study, efforts were made to check whether the geo-coordinates of
any Wildlife Sanctuary is falling within the area of study. The map
No. 1(d) (Annexure-9.1) explains the location of the Sanctuaries visà-vis
the dam site and the power house.
(ix) The nearest National park is Mouling which is about 93 Km from the
dam site. The nearest sanctuaries are Kane, Itanagar, Pakhui and
D’Ering memorial which are about at distance of 115 km, 145 km,
156 km and 169 km respectively. So it is observed that the dam site
is more than 90 km away from the National Park and Sanctuaries.
Hence, proposed development of the site is least likely to have
impact on them.
Further, results of Land use- Landcover study covering an area of 7 km
radius around the damsite are presented in Table 9.2.
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9.1.9 Water Quality
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Population density along the reservoir is not very high. Scattered huts
along the road have been observed. People are mostly engaged in
agriculture. Since there is no industrial unit in or around the proposed
project area and also the fact that the inhabitants are still following their
age-old methods of cultivation, it is assumed that there would be no such
chemical pollution in the river. However, a detailed water quality analysis
would be carried out during the environmental survey to ascertain the
quality of water and necessary measures would be adopted accordingly to
prevent its deterioration.
9.2 BIOTIC ENVIRONMENT
9.2.1 Flora
The predominant vegetation is sub-tropical type and is basically dense and
evergreen in nature. The floristic components observed in the area
dominated by tall trees like Oblongum, Actinodaphne obovata, Alnus
nepalnensis, Beilschemiedia roxburghiana, Bytineria grandiflora, Callicarpa
arborea, Castanopsis indica, Dichroa febrifuga, Kydia calycina, Magnolia
pterocarpa, Sauraria punduana, Schima wallichii, Sterculia hamiltonii, etc.
The next storey is composed of small trees like Lepisanthes senegalensis,
Capparis muliflora, Photinia integrifolia.etc.
Third storey is comprised of small trees and shrubs like Eurya acuminate,
Myrsina semiserrata, Camellia candata, etc. Comman climbers generally
occurring in the area are Clematis acuminate, holboelia latifolia, Tinospors
sinensis, etc.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The ground flora formed by the dense growth of shrubs and herbs is
represented by Cassia mimosoides, Drymaria diandra, Mahonia
acanthifolia, Plectranthus griffithii, Solanum erianthum, Sophora acuminate,
Tephrosia candida, Vernonia saligna, Viburnum foetidum, Begonia pocta,
Oxalis corniculata, O. corymbosa, Impatiens spp.Lobelia spp.,etc.
These forests shows good diversity of epiphytic flora including a variety of
ferns and a number of Orchid species of Cymbidium, Bulbophyllum,
Dedrobium, Oberonia etc.
The excerpts from preliminary report of Botanical Survey of India (BSI),
Itanagar, Arunachal Pradesh is placed at Annexure 9.2.
9.2.2 Fauna and Wildlife
The entire project area has fairly good forest coverage. It serves as a
habitat for many faunal species. But, with progress of time due to increases
in human interference, shifting cultivation and other activities, wildlife has
been affected. However some of the faunal species found in the area are as
follows:
Mammalia (Mammals)
Talpa micrura (Himalayan Mole), Suncus murinus (House Shrew), Pteropus
gigantcus (Indian Flying Fox), Macaca mulata (Rhesus Monkey), Canis
aureus (Golden Jackal), Vulpes vulpes (Red Fox), Viverra zibetha (Large
Indian Civet), Felis chaus (Jungle Cat), Prionailurus bengalensis (Leopard
Cat), Rotufa bicolor (Malayan Giant Squirrel).
Aves (Birds)
Acridotheres grandis (Great Myna), Picus canus (Grey- Headed
Woodpeeker), Upupa epops (Eurarsian Hoopoe), Ninox scutulata (Brown
Hawk-Owl), Venellus indicus (Red Wattled Lapwing), Gracula religiosa (Hill
Myna).
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Pisces (Fish)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Barilius vagra, Puntius chola, Puntius sophore, Tor putitora, Mystus
montanus, Psilorhynchus balitora, Channa striatus, Colisa fasciatus,
Mastacembelus pancalus.
Amphibia (Frogs)
Rana danielli, Amolops gerbillus, Microhyla rubra.
Reptilia (Snakes)
Bungarus fasciatus, Elaphe radiata, Ptys korros, Xenohrophis piscator,
Oligodon albocinectus.
Lepidoptera (Butterflies)
Phalanta phalantha (Common Leopard), Papilio helenus (Red Helen),
Papilio demoleus (Lime Butterfly), Eureuma hecabe (Common Grass
Yellow).
The species listed above are commonly distributed. However, the frog
species reported above are rarely found. Detail survey of the area in
different seasons of the year is likely to add more knowledge on the fauna
of the project area.
The preliminary report from Zoological Survey of India (ZSI), Itanagar and
from Department of Fishery, Arunachal Pradesh are enclosed as
Annexure 9.3 & Annexure 9.4 respectively.
Thus from the above list it is evident that the species found are generally
common fauna usually encountered in such ecological condition. There is
no endangered or threatened species observed or recorded from the
project area so far. However, a detailed survey of the area in different
seasons of the year may yield a different picture on the faunal diversity of
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
the area and which may be useful in preparation of the environmental
impact assessment for the proposed project
9.3 PREDICTION OF ENVIRONMENTAL IMPACTS
Based on above baseline data and project features, the potential impacts
that are expected as a result of the proposed project are summarized as
follows
9.3.1 Impacts on land environment
About 740 ha would be required for the proposed project out of which 300
ha would come under submergence. About 455 ha of forest land would get
affected in the process. With the acquisition of forestland, the local
population, dependent on these forests, might get affected. Most of the
environmental impacts resultant of construction work is temporary in nature
rarely lasting beyond the construction period. All these issues are to be
properly addressed so that the long-term effects, if any, can be minimized.
9.3.2 Impact on Water Environment
The construction of a reservoir will replace the riverine eco-system by a
lacustrine ecosystem. The vectors of various diseases breed in shallow
areas are not very far from reservoir margins. The breeding site for
mosquitoes and other vectors in impounded water is in direct proportion to
the length of the shoreline. The construction of the reservoir would increase
the shoreline many times as compared to the pre-project shoreline of
various rivers and tributaries under submergence. In the proposed project
area, malaria is the prominent vector borne disease. There are chances
that its incidence may increase as the proposed project is a storage
scheme. Because of the regulated flow of water some changes is also likely
in the aquatic environment in the downstream areas of the project. The
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
important changes that are likely to happen in this area are: reduction in
flow rate changes in water temperature, reduction in population of
stenothermal species (species adapted to small temperature range) and
increase in population of eurythermal species (species adopted to higher
temperature range).
9.3.3 Impacts on Air and Noise Environment
Impacts on the air environment are limited to the construction period of a
hydropower project. The major sources of air pollution during construction
phase are emission from crushers, DG sets, construction equipments etc.
Thus local air pollution (including dust and odour) will result from the
operation of plant machinery and traffic. Noise and vibration due to
construction activities (e.g. blasting, machinery and traffic) may disturb local
wildlife and human populations. However, there will be only short-term
increase in emissions like SO2 and Suspended Particulate Matters (SPM)
during the construction period of the project. The level of noise would also
decrease substantially once the construction phase is over. Hence no
major impact is anticipated on this account.
9.3.4 Impacts on flora and fauna
Due to construction of dam about 300 ha of land will be inundated out of
which 150 ha is falling under forest land category. The direct impact of
construction activity of a water resources project in a hilly terrain is
generally limited to the vicinity of the construction sites. This may alter the
local diversity of flora and also affect habitat available for fauna. Changes
to, or loss of habitat will affect areas used for mating, breeding, nursing,
moulting, feeding, and drinking for both resident and migratory wildlife.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The extent and severity of these effects will vary according to the existing
habitat and the particular species involved which would be known after
detailed study is done on flora and fauna during the comprehensive
EIA/EMP study and suitable mitigation measures would be formulated and
implemented in consultation with the State Forest Department of Arunachal
Pradesh.
9.3.5 Impacts on Avifauna
The construction of the proposed dam will lead to formation of a reservoir,
which will have a fluctuation in the water level, which precisely means the
reservoir bank will remain wet throughout the year. Due to such reasons,
some aquatic weeds / grasses may grow along the reservoir banks. Such
conditions are generally ideal for various kinds of birds, especially water
birds. However because of the presence of a good habitat it is quite likely
that water birds will flock in this area in a large number. The birds from cold
climatic areas could also use this area during the winter season.
9.3.6 Impacts on Fishes
A dam will fragment and isolate upstream resident fish. The resident
species may congregate in the tail water release site. Fish from upstream
will occasionally sweep downstream during the monsoon, stay in the tail
water or swim further downstream. A dam may obstruct the route of the
long and mid-distance migratory fish. There may be an impact on the fish
composition due to construction of dam. A detailed fishery study would be
conducted during the EIA/EMP study to determine the likely impacts and
suitable mitigatory measures would be adopted.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
9.3.7 Impacts on Socio-Economic Environment (Resettlement &
Rehabilitation)
Due to acquisition of 285 ha of private land, there is a possibility that some
families would get affected either partially or fully. To ascertain the extent
of impact due to this proposed project, a detailed socio-economic survey
would be carried out, as a part of the EIA/EMP study to ascertain the
degree and extent of impact and accordingly a suitable rehabilitation
package would be formulated. During the construction of the project the
basic problem relates to management of large population that migrate to the
area in search of jobs and other allied activities. Thus migration of a
population having different cultural, ethnic and social backgrounds has its
own advantages and disadvantages. Exchange of ideas, cultures between
various groups of people would result in a healthy bonding amongst the
population at large. A new culture having a distinct socio-economic status
with an entity of its own would develop. As a result of this project there
would be all-round development of the region.
9.3.8 Impact on Archaeological structures/Sanctuaries or National
Parks
As per the initial survey there is neither any archaeological structure nor
any Sanctuary or National Park that are likely to get affected due to the
project directly or indirectly.
9.4 ENVIRONMENTAL MANAGEMENT PLANS
The objective of the Environmental Management Plan (EMP) is to
ameliorate the negative impacts of a developmental project. The most
reliable way to ensure proper implementation of these management plans is
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
to integrate the same with various processes involved during project
planning, designing, construction and operation phases. Based on the
assessment of environmental impacts, following management plans will be
formulated:
Catchment Area Treatment
Compensatory Afforestation
Wildlife Conservation
Resettlement and Rehabilitation
Public Health Management System
Muck Disposal
Fishery Management
Restoration of Construction Area
Green Belt Development
Free Fuel Provision
Disaster Management
MOEF Restriction on Construction of dams in Subansiri Basin
It is stated that Ministry of Environment and Forest (MOEF) vide their letter
No: 6-I/2002 WL-I dated 27.05.2003 regarding diversion of 42 ha of land
falling within the Tale Wildlife Sanctuary for construction of Subansiri Lower
Project (SLP) has imposed a condition that there would be no construction
of dam upstream of the Subansiri river in future. As this project is located
upstream of Subansiri Lower Project in Subansiri river this condition is
required to be considered while considering the project for preparation of
DPR.
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10.0 INTRODUCTION
CHAPTER –X
INFRASTRUCTURE
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The project is located near Nalo village in Upper Subansiri District of
Arunachal Pradesh. The Dam site is proposed upstream of confluence of
Ledi Ishi nallah with Subansiri. The power house is proposed on the right
bank of Subansiri river at about 5 Km (along river course) downstream of
damsite. Dam site is easily accessible by all weather Daporijo –Limeking
road. Daporijo, the district headquarter of Upper Subansiri District is about
120 km from dam site. Project township and its headquarters can be
proposed at Nacho. Nacho is about 10 km (downstream) from dam site
and 5 km from powerhouse site. Itanagar, the state capital is about 460
km from dam site. Project is about 800 km from Guwahati and 400 km
from North Lakhimpur. The project site can be accessed from NH-52
which runs almost parallel to the river Brahmaputra on its North Bank
from Baihata Chariali (near Guwahati) to Murkongselek (Jonai) in Dhemaji
District.
Nearest MG Railhead is North Lakhimpur and Broad Gauge Railhead is at
Nagaon. Nearest Airport is at North Lakhimpur (Lilabari). Presently,
there is tri-weekly air service from Guwahati (Borjhar) to North
Lakhimpur (Lilabari). There are helipads at Daporijo, Nacho and
Limeking nearer to the project area.
Approximate distances and conditions of road from/to Project Site is given
in Table 10.1.
110

Sl
No.
Table10.1
Status of Road Network connecting Project site
Destination Approx
distance
1 Pahumara
(Take-off point
of Road from
NH-52) to
Daporijo
2 Daporijo to
Dengser
damsite
3 Dengser
damsite to
Nalo damsite
4 Approach
roads for adit
to
PH
HRT and
Condition of
Road.
284 Km Single lane black
topped road.
(Maintained by
BRO)
110 km Single lane black
topped road.
(Maintained by
BRO)
15 km Single lane black
topped road.
(Maintained by
BRO)
25 km New proposal.
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Remarks
Provision of widening
of road and
strengthening of
bridges has been kept
in FR/DPR of
Subansiri
Middle/Upper Projects
Provision of widening
of road and
strengthening of
bridges has been kept
in PFR of Dengser HE
Project.
Provision of widening
of road and
strengthening of
bridges has been kept
in PFR of Nalo HEP.
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Provision for widening of existing road from Pahumara/ Kimin to Daporijo
has been kept in cost estimates of Subansiri Middle /Upper Projects and
provision for widening and strengthening of roads & bridges from Daporijo
to Dengser dam site has been kept in cost estimates of Dengser HE
Project. As such, the same has not been considered in cost estimate of
this project. Nevertheless, cost of upgradation of road between Dengser
dam site and Nalo dam site is taken into account. In case, Nalo HE
Project, if decided to be taken for construction before construction of
Subansiri Middle/Upper/Dengser Projects, infrastructure requirement (R-
Communication) of Nalo HE Project shall need to be revised.
10.1 IDENTIFICATION OF BROAD INFRASTRUCTURE
REQUIREMENTS
In order to complete the project over a period of 6 years, broad
infrastructure requirements are identified as under:
10.1.1 Road Communication Network
Strengthening/ widening of existing road network (Table-10.1)
including bridges/culvert from Daporijo to project site measuring
about 125 km.
However, as mentioned in Table 10.1, provision for widening
/strengthening from Daporijo to Dengser damsite (110 km) is kept
in PFR of Dengser HE Project. In Nalo HE Project, provision of
widening /strengthening of road is kept for the stretch from Dengser
damsite to Nalo dam site alongwith some miscellaneous stretches
(25km).
Construction of approach roads for adit to power house and HRT.
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10.1.2 Project headquarter, Offices and Colonies
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The project township is planned to accommodate about 650
quarters and 200 single/ shared accommodation in Field Hostel and
Barracks.
Non-residential buildings, such as Administrative building, School,
Hospital, Bank, Post Office, Clubs, Auditorium, Shopping complex,
Canteen, Workshops, Stores, Diesel Power House, etc will be
required at project headquarter. It is estimated that the Nonresidential
buildings will be required about 30,000 sqm of plinth
area.
10.1.3 Miscellaneous
Arrangements for Power, Fuel station and Telecommunication system etc
will also be required.
113

CHAPTER – XI
CONSTRUCTION PLANNING & SCHEDULE
11.0 INTRODUCTION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Equipment Planning & Construction Methodology of Nalo H.E. Project
(4x90 MW), in Subansiri Basin has been developed on following
considerations , -
1. The project construction period has been considered as six years
after completion of Stage I & II activities.
2. Available Geological Data at PFR stage.
3. Requirement of Construction Equipment has been planned to handle
the quantities worked out on the basis of preliminary layout.
4. Five months rainy season has been considered while planning
surface works. However the time period indicated in the schedule for
various components includes rainy season.
The Construction Planning Schedule prepared for the project based on
above considerations is placed at Table 11.1.
11.1 CONSTRUCTION METHODOLOGY
11.1.1 Infrastructure Works
The main infrastructure development is proposed to be initiated
simultaneously with preparation of DPR (Stage II activity) for which a
provision of 18 months will be kept and completed in initial 12 months after
taking up construction activity (Stage-III activity). During infrastructure
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Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
development period Land Acquisition, construction of approach roads,
bridges & culverts, arrangement of construction power will be undertaken.
Critical components of project would be started from 7th month after
construction of approach roads. Platform to accommodate batching plant,
stores for construction material, site workshop, offices and other buildings
(residential/ non residential) colonies will also be developed in
infrastructure period. Crawler Dozer, Loader cum Excavator, Motor
Grader, Air compressor, Road Roller etc. are proposed for deployment
during infrastructure stage.
11.1.2 Diversion of River
The construction of 2 nos. 10.75 m finished diameter, Horse shoe shaped
650/800 m long diversion tunnels would be carried out by heading &
benching method. Excavation of Diversion Tunnels will be carried out with
2 Boom drill jumbo, Air Track/Wagon Drill, Jack hammer, 2.5 cum side
dump loader and 20/25T L P Dumpers. Diversion tunnel excavation,
erection of shutters & concreting and HM work would be completed in 24
months. The concreting of diversion tunnel would be catered by Batching
& Mixing plant, aggregate processing plant being proposed at dam,
Concrete pump, Transit mixer and shutters etc. U/s & D/s Coffer dams
would be constructed immediately after construction of diversion tunnel
within a period of 4 months to divert the river. However river bed
excavation would be taken up during the start of 3 rd month of construction
of coffer dams. Repair work of coffer dams would be done twice in two
months after each rainy season.
11.1.3 Concrete Dam and Plunge Pool
Dam abutment stripping would be done in 26 months. After diversion of
river, excavation of river bed & foundation treatment would be carried out
in 3 months. Excavated material will be handled by 2 nos. 2.0 cum Hyd.
115

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Excavator and 25 T Rear dumpers. Concreting of Dam & HM work would
be carried out in further 30 months. Concreting would be catered by
deploying 2x28T Cable ways with 3.0/6.0/9.0 cum buckets, 2 nos. 350
Cum/hr Batching & Mixing Plant and 1400TPH Aggregate Processing
plant which will cater the requirement of Diversion tunnel, intake structure,
Desilting chamber, part of HRT, plunge pool and Dam.
Excavation of plunge pool would be carried out in 6 months. The same
equipment as deployed at Dam for excavation would be used for plunge
pool excavation. Concreting of plunge pool would be done in 4 months
with the help of Concrete pump with placer boom, Concrete mixers ,
vibrator etc.
11.1.4 Intake Structure, Desilting Chamber Silt Flushing tunnel
2 Nos intake structures, intake tunnels and 4 Nos Desilting Chamber of
size 300m X17mX 25m would be excavated in 24 months. Excavation of 2
nos 8.5 m dia , 250 m and 350m long intake tunnels would be carried out
by heading and benching method. Excavation of Desilting Chamber would
be taken up from adits to desilting chamber. Initially tunnels of 6.0 m dia
would be excavated by full face method to the full length of Desilting
Chambers. Thereafter it will be expanded side wise to the full width of
desilting chambers resulting in desilting chamber dome. Mucking of
excavated material would be done through the adits of desilting chamber.
After the excavation of desilting chamber, concreting will be carried out.
Excavation of silt flushing tunnel & gate operation chamber would be a
parallel activity. The equipment to be deployed are two boom drill jumbo,
Jack hammers, wagon drills, air compressors, side dump loader, L.P.
dumpers, concrete pump, transit mixers etc. However concreting
requirement of intake tunnel & Desilting chamber would be catered by
Batching & Mixing Plant and aggregate processing plant installed at Dam.
116

11.1.5 Head Race Tunnel
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Initially excavation of approaches and adits for HRT would be carried out
in 4 months. Thereafter excavation of 2 nos. 7.5 m finished diameter
each, 2.5 km and 2.6 km long horse shoe shaped Head Race Tunnels
would be done by heading and benching method in 18 months through 1
number intermediate adit. Excavation would be carried out by deploying
two boom drill jumbo, 2.5 cum side dump loader and 20/25T L.P. dumper.
Concreting will be done by deploying concreting equipment i.e. Concrete
pump, Transit Mixer in 12 months. 1 no. 60 cum/hr Batching & mixing plant
and 100 TPH aggregate processing Plant is proposed at HRT.
11.1.6 Surge Shaft
Initially construction of approaches for surge shaft would be done in 4
months. Thereafter excavation of 2 nos 20 m diameter, 90 m high, Surge
shaft would be taken up from top of surge shaft. Excavation of Surge Shaft
would involve pilot hole drilling, reaming of pilot hole & enlargement of
reamed hole. Raise borer, Wagon Drill, 100 HP Dozer, 2.5 cum Side Dump
Loader & 20/25 t LP Dumpers etc will be deployed for excavation of Surge
shaft. Concreting would be completed employing 2 m shutter, concrete
pump. 120 cum/hr Batching &mixing plant and 250 TPH aggregate
processing Plant would be deployed to cater the requirement of surge
shaft, part of HRT and part of pressure shaft. Excavation and concreting of
surge shaft would be completed in 50 months.
11.1.7 Pressure Shaft
Before construction of Pressure shaft, approaches and adits would be
completed in 4 months. 2 nos. 6.25 m diameter, 82 m high each, vertical
pressure shafts will be excavated by deploying Raise Borer, 2.5 cum side
dump loader, 20 t LP dumper, Jack hammer etc. Steel liner erection &
117

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
concreting will be carried out by deploying 10/20 t winches, Slipform liner
etc. Excavation of Pressure shaft, erection of steel liners and concreting
would done in 50 months. Concreting of pressure shaft would be catered by
Batching & Mixing Plant and aggregate Processing Plant proposed to be
installed at surge shaft & Power House.
11.1.8 Power House
4 X 90MW (360 MW) surface power house would be excavated in 16
months. For excavation of Power House benches of suitable height will be
developed by cutting hill slopes. The equipment to be deployed for
excavation are Jack Hammers, wagon drills, air compressors, loaders,
excavators dumpers etc. Concreting of Power house would be carried out
in 36 months. Concreting of Power house would be carried out by
deploying 1 no. Tower Crane 6.9 T at 60 m radius, concrete pump, Transit
mixers, concrete vibrators etc. 80 cum/ hr Batching & Mixing Plant and 100
TPH aggregate processing Plant would be installed at Power House which
also cater the requirement of part of pressure shaft and Tail Race Channel.
Installation & Testing of Machine would be undertaken in such a manner
that Project get commissioned in 72nd month from the start of Project
construction.
11.1.9 Tail Race Channel
Excavation of Tail Race Channel having bed width of 60 m and side slope
of 1V: 1.5H would be carried out by deploying wagon drill, jack hammer, 1.0
cum hyd. Excavator, 20t Dumpers etc. in 4 months. Concreting & misc.
works of tail race channel would be started from 38th month and completed
in further 6 months. Concreting requirement of TRC would be catered by
concrete pump, transit Mixer, Batching & Mixing Plant and aggregate
processing Plant installed at Power House.
118

Sl.
No.
CCEA Clearance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72
1 INFRASTRUCTURE DEVELOPMENT
a Acquisition of private & forest land Ha 8
b Construction of roads & buildings LS 12
2 AWARD OF CONTRACTS
a Tendering & award LS 3
b Mobilization LS 3
3 DIVERSION TUNNELS( 2 nos., 10.75 m
dia, 650/800 m long horseshoe)
a Excavation m 3 4,21,000 16
b Erection of shutters & Conc. Lining m 3 1,04,000 10
c HM Works Job LS 6
d Plugging of tunnels Job LS 2
4 COFFER DAMS
( U/s of 28m height & D/s of 14m ht)
a Const.of Coffer Dams & River Diversion 3
m
U/s=4.50lacs
D/s=1.06 lacs
4
b Reconstruction of Coffer Dams 12,12,000 4
5 CONCRETE DAM (125 m High,
381 m Length at top) with Spillways
a Dam abutments stripping m 3 5,10,000 26
b Excavation and foundation treatment m 3 1,70,000 3
c Mass Concreting m 3 17,48,000 26
d HM and other misc. works Job LS 18
e Reservoir filling Job 2
6 PLUNGE POOL
a Excavation m 3 2,60,000 6
b Concreting Works m 3 52,000 4
7 HEAD RACE TUNNELS (2 nos. of 2.5/2.6 km
length & 7.5m dia horseshoe
a Excavation of approches and Adits Job LS 4
b Excavation m 3 4,30,000 18
c Concrete Lining m 3 1,58,000 12
d Grouting Job LS 6
e Adit pluggings, Cleanning etc. Job LS 3
f Water conductor charging Job LS 1
8 INTAKE STRUCTURES, INTAKE
TUNNELS AND DISILTING
CHAMBERS ( 4 nos. of size 300x17x25m)
a Excavation m 3 10,34,000 24
b Concrete Lining m 3 2,88,000 20
c HM Works Job LS 15
d Grouting and other misc. works Job LS 6
9 SURFACE POWER HOUSE
(Powerhouse cavern 103x22x47m )
CONSTRUCTION SCHEDULE OF NALO HE PROJECT IN SUBANSIRI BASIN (4X90=360 MW), ARUNACHAL PRADESH
Name of Work Unit Quantity Duration
(months) Ist year IInd year
a Const. of Approches Job LS 3
b Excavation of PH & TG m 3 5,35,000 16
c Concreting in sub & super structures m 3 1,24,000 36
d Erection of EOT crane Job LS 3
10 SURGE SHAFTS
(2 nos.of 20m dia. of 90m high)
a Const. of approches Job LS 4
b Excavation m 3 97,000 30
c Concreting & HM Works m 3 35,000 20
11 STEEL LINED PRESSURE SHAFTS
(2 nos. of 6.25 m dia, 82 m vertical height )
& Penstocks
a Const.of approaches & adit Job LS 4
b Excavation m 3 33,000 30
c Erection of steel liners & Concreting m 3 16,000 20
12 TAILRACE CHANNEL
( 60 m bed width & 50 m length )
a Excavation m 3 30,000 4
b Concreting & Misc.Works m 3 1,500 6
13 SWITCH YARD (Size 160x80m)
3
m
Exc.
2,95,000
15
14 ELECTRO-MECHANICAL WORKS
a
Erection, Testing & Commisioning
of all four units
Job 42
Note: Since the date of CCEA clearance cannot be anticipated at this stage, the time assumed for various activities is inclusive of the effect of monsoon.
Schedule of Constructiom
IIIrd year IVth year
-
V th year
VI th year
TABLE-11.1
119

12.0 COST ESTIMATE
CHAPTER –XII
COST ESTIMATE
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
12.1 PRELIMINARY COST ESTIMATE FOR CIVIL, HYDRO-
MECHANICAL, ELECTRO-MECHANICAL WORKS
The estimate has been prepared to arrive at the Capital Cost of Nalo H. E.
Project and is of Pre-feasibility level of accuracy. The base date of the
estimate is June 2003 and the Cost is expressed in Indian Rupees. The
Cost Estimate is divided into Civil, Electrical and Transmission Works. For
Civil Works, the sub heads are as under :
12.1.1 I-Works
Under this head, provision has been made for various components of the
Project as detailed hereunder :
12.1.2 A-Preliminary
Under A-Preliminary, provision has been made for all surveys and
investigations to be conducted to arrive at the optimum of the Project
Components.
12.1.3 B-Land
This covers the provision for acquisition of land for construction of the
Project, colonies, offices and stores and compensation for trees and
standing crops etc. This head also contains the provision for Rehabilitation
and Resettlement measures for Project Affected People.
120

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
12.1.4 C-Works
This covers the cost of Diversion Tunnel, Coffer dam, Concrete Dam with
associated Hydro-mechanical works.
12.1.5 J-Power Plant Civil Works
This covers the cost of project components viz. Intake Structure and Head
Race Tunnel, Desilting Basins, TRT, Power House and Transformer
Cavern, Pressure Shaft, Surge Shaft and other Appurtenant Works along
with associated Hydro-mechanical woks.
The quantities indicated in the estimates for C - Works & J-Power Plant Civil
Works (Civil & HM) are calculated from the preliminary Engineering
drawings and as per experience of other on-going or commissioned
projects.
The unit rates for various items are taken as per the Guidelines issued by
CEA for preparation of PFRs. It has been assumed that the quarry is
available at a distance of 10 Kms from the work site.
12.1.6 K-Buildings
Buildings, both residential and non-residential have been provided under
this head. Under the permanent category only those structures have been
included which shall be subsequently utilized during the operation and
maintenance of the project. The costs are worked out on plinth area basis
prevalent in the area for the type of construction involved.
12.1.7 O-Miscellaneous
Provision under this head has been made for the Capital & running cost of
Electrification, Water Supply, Sewage Disposal, Fire Fighting Equipments,
121

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Medical Assistance, Recreation, Post Office, Telephone and Telegraph
Office, etc. The Provisions have been made for the security arrangements,
inspection vehicles, schools, transport of labour, laboratory testing, R&M of
guest house and transit camps, community center, retrenchment
compensation, photographic instruments as well as R&M charges etc.
12.1.8 P-Maintenance During Construction and Y-Losses on Stock
A provision of 1% and 0.25% of C-Civil works, J-Power Plants, K-Buildings
& R-Communications has been made for maintenance of works during
construction period and losses on stock respectively.
12.1.9 Q-Special Tools and Plant
It is assumed that the work will be carried out through Contracts and not
through departmental construction. Accordingly, provision for general
purpose equipment and inspection vehicle only has been made as per CWC
guidelines.
12.1.10 R-Communication
Provision under this head covers the cost of new roads,
widening/improvement of roads and strengthening of bridges. The costs of
roads and bridges are based on the rate structure prevalent in the area of
the Project, for the type of construction involved.
12.1.11 X-Environment and Ecology
Provision under this head has been taken as 2% of I -Works towards biodiversity
Conservation, creation of Green Belt, Restoration of Construction
Area, Catchment Area Treatment, Compensatory Afforestation etc
122

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
12.1.12 II-Establishment
Provision for establishment has been made at 8% of I-works minus B-Land
for civil works.
12.1.13 III-Tools and Plants
This provision is distinct from that under Q-Special T&P and is meant to
cover cost of survey instruments, camp equipment and other small tools
and plants. The outlay is provided at 1% of cost of I-works.
12.1.14 IV-Suspense
No provision has been made under this head as all the outstanding
suspense are expected to be cleared by adjustment to appropriate heads at
completion of the project.
12.1.15 V-Receipts and Recoveries
Under this head, provision has been made for estimated recoveries by way
of resale or transfer of equipment used in infrastructure works.
12.1.16 Electrical Works and Generating Plant
The cost of Generating Plant and Equipment is based on indigenous
sources. The prices of auxiliary equipment and services are based on
prevailing market prices/costs incurred at other ongoing or commissioned
projects.
123

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
ABSTRACT OF COST OF WORKS
S.No Description Amount
(Rs. in Crores)
( June 2003 P.L.)
A CIVIL WORKS
1. DIRECT CHARGES
I – Works
A – Preliminary 30.29
B – Land 8.96
C – Works 990.41
J - Power Plant Civil Works 716.78
K – Buildings 55.86
O – Miscellaneous 80.57
P – Maintenance 18.26
Q-Special Tools & Plants 5.58
R – Communication 62.80
X - Environment & Ecology 40.29
Y - Losses on Stock 4.56
Total of I-Works 2014.37
II - Establishment @ 8% of cost of I-Works less B-Land 160.43
III - Tools and Plants @ 1% of cost of I-Works 20.14
IV – Suspense 0.00
V - Receipt & Recoveries (-) -2.78
TOTAL DIRECT CHARGES 2192.17
2. INDIRECT CHARGES
a) Capitalised Value of Abatement of Land Revenue 0.15
b) Audit and Account Charges @1% of cost of I-Works 20.14
TOTAL INDIRECT CHARGES 20.30
TOTAL OF DIRECT & INDIRECT CHARGES 2212.47
ABSTRACT :
A Civil Works 2212.47
B Electrical Works 334.89
C Transmission Works 62.31
TOTAL COST 2609.66
D IDC 312.48
E Total Cost With IDC 2922.14
124

S.
No.
A - PRELIMINARY
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Particulars Unit Qty Rates Amount Rs.
in Lakhs
1 Expenditure incurred on PFR stage investigation -- -- -- 14.00
2 Detailed Survey for final location L. S. -- -- 150.00
3 Aerial Survey, contour survey for reservoir basin
including establishment of permanent bench marks
L. S. -- -- 150.00
4 Geological surveys, Geophysical surveys and rock
mechanics tests
L. S. -- -- 150.00
5 Ground water studies L. S. -- -- 10.00
6 Hydrological and Meteorological Surveys including
establishment of rain gauges/river gauges and
discharge, sedimentation station and their running
L. S. -- -- 100.00
7 Investigation for foundation and rock testing.
Drilling - 3000m . Drifting - 700m
8 Investigation for availability of construction
materials
9 Construction of access roads & foot/ suspension
bridge to facilitate investigations
-- -- 350.00
L. S. -- -- 100.00
L. S. -- -- 75.00
10 Model Experiments L. S. -- -- 150.00
11 Computer & Telecommunication L. S. -- -- 50.00
12 Preparation & Printing of project report L. S. -- -- 35.00
13 Vehicles for inspecting officers for site
investigations
No. 10 5 50.00
14 Helicopter Support L. S. -- -- 100.00
15 Construction power for investigation and
infrastructure works
L. S. -- -- 100.00
16 Office and camp equipments L. S. -- -- 100.00
17 R & M of Office and Transit camps etc. L. S. -- -- 200.00
18 Preliminary soil test establishing soil testing
laboratory
L. S. -- -- 50.00
19 Consultant's fees including charges for preliminary
design work for advice
L. S. -- -- 1000.00
20 Training of engineers during investigation and L. S. -- -- 20.00
preparation of project reports.
21 Environmental & Ecological studies L. S. -- -- 75.00
Total 3029.00
125

B - LAND
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Particulars Area (ha) Rates (Rs Amount (Rs. in
1
Lakhs /ha) Lakhs)
A Forest/Govt. Land
a) Reservoir Area 150 0.65 97.50
b) Project features 80 0.65 52.00
c) Township, stores area and roads 100 0.65 65.00
d) quarry site 20 0.65 13.00
e) muck Disposable area 10 0.65 6.50
f) Transit Camp and Guest houses 5 0.65 3.25
g) Land for rehablitation purpose 90 0.65 58.50
Sub Total A 295.75
B Private Land
a) Reservoir Area 150 1.10 165.00
b) Project features 50 1.10 55.00
c) Township, stores area and roads 75 1.10 82.50
d) Transit Camp and Guest houses 10 1.10 11.00
Sub Total B 313.50
2 Rehabilitation & Resettlement (land
for rehablitation included)
3 Cost of Establishment for land
acquisition and Rehabilitation @
6.25% of Item 1&2
4 Solatium charges @ 30% of the cost
of Private Land
5 Interest charges on amount of award
for the period between taking over
possession of land and date of award
@ 12% per annum on 25% of cost of
total compensation for 2 years
6 Legal charges @ 1% of total
compensation
7 Labour and material required for
measurement & demarcation of
land/Properties @ 1% of cost of land
Acquisition
L. S. 100.00
44.33
94.05
36.56
6.09
6.09
Total 896.37
Note : 50% of rock quarries and all clay borrow areas fall in submergence area/ project area.
Hence provision for these has not been made
126

ABSTRACT OF COST OF C - WORKS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. N. Description Amount (Rs. In Lakhs)
CIVIL HM TOTAL
1. DIVERSION TUNNEL 9753.79 686.70 10440.49
2. COFFER DAMS 5373.63 5373.63
3. CONCRETE DAM INCLUDING SPILLWAY
AND PLUNGE POOL
73253.05 3668.18 76921.23
TOTAL 88380.48 4354.88 92735.35
ADD FOR WORKS TAX @ 6.8% 6009.87 296.13 6306.00
GRAND TOTAL 94390.35 4651.01 99041.36
127

DIVERSION TUNNEL
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1 Surface Excavation
1.1 Common excavation Cum 46,000 125 57.50
1.2 Rock excavation Cum 110,000 300 330.00
2 Underground excavation Cum 265,000 1000 2650.00
3 Support System
3.1 Rock bolts M 70,000 400 280.00
3.2 Steel Rib Supports MT 800 42000 336.00
3.3 Shotcrete Cum 11,000 4000 440.00
3.4 Concrete Lagging Cum 1,300 7000 91.00
4 Concrete
4.1 Concrete Lining M-20 Cum 45,000 4000 1800.00
4.2 Concrete in portals, backfill etc.
M-15 Cum 8,000 2930 234.40
M-20 Cum 29,000 3390 983.10
M-25 Cum 22,000 3610 794.20
5 Reinforcing steel MT 1,500 27000 405.00
Sub total A 8401.20
6 Miscellaneous and ancillary works @
7.5% of sub-total A
7.50% 630.09
Sub total B 9031.29
7 Instrumentation @ 1% of sub-total B 1.00% 90.31
8 Dewatering @ 2% of sub total B 2.00% 180.63
9 Contingency @ 3% of sub-total B 3.00% 270.94
10 Work Charged establishment @ 2% of
Sub-total –B
2.00% 180.63
Total civil works 9753.79
128

COFFER DAMS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Quantity Rate Amount
( Rs. in
Lakhs)
1 Surface Excavation
1.1 Common excavation Cum 18,000 125 22.50
2 Embankment Constrcution
2.1 Earth /Rock fill Cum1,100,000 342 3762.00
2.2 Impervious Core Cum 280,000 354 991.20
2.3 Filter Cum 17,000 901 153.17
3 Concrete
3.1 M-10 Cum 400 2560 10.24
3.2 M-15 Cum 400 2930 11.72
Sub Total(A) 4950.83
4 Miscellaneous and Ancillary
Works @ 0.5% of sub-total A
0.5% 24.75
Sub-Total(B) 4975.58
5 Dewatering @ 3% of sub total (B) 3% 149.27
6 Contingency @ 3% of sub-total B 3% 149.27
7 Work Charged establishment @
2% of Sub-total B
2% 99.51
Total civil works 5373.63
129

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
CONCRETE DAM INCLUDING SPILLWAY AND PLUNGE POOL
S. No. Description Unit Quantity Rate Amount
( Rs. in
Lakhs)
1 Surface Excavation
1.1 Common excavation Cum 410,000 125 512.50
1.2 Rock excavation Cum 530,000 300 1590.00
2 Support System
2.1 Rock bolts M 14,000 400 56.00
2.2 Shotcrete Cum 6,000 4000 240.00
3 Concrete
3.1 M-15 Cum 1,065,000 2930 31204.50
3.2 M-20 Cum 355,000 3390 12034.50
3.3 M-25 Cum 380,000 3610 13718.00
4 Reinforcing steel MT 23,000 27000 6210.00
5 Miscellaneous and Ancillary Works
@ 2.5% of sub-total A
2.5%
Sub Total(A) 65565.50
1639.14
Sub-Total(B) 67204.64
6 Instrumentation @ 1% of sub-total (B) 1% 672.05
7 Dewatering @ 3% of sub total (B) 3% 2016.14
8 Contingency @ 3% of sub-total B 3% 2016.14
9 Work Charged establishment @ 2%
of Sub-total B
2% 1344.09
Total civil works 73253.05
130

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
J -POWER PLANT APPURTENANCES (CIVIL WORKS)
S. Description Amount (Rs. in Lakhs)
NO. CIVIL HM TOTAL
1. INTAKE STRUCTURE INCLUDING INTAKE
TUNNEL UPTO DESILTING CHAMBERS
5054.61 725.55 5780.16
2. DESILTING CHAMBERS 22591.63 1162.77 23754.40
3. HEAD RACE TUNNEL 16029.11 16029.11
4. SURGE SHAFTS 3707.86 229.11 3936.97
5. PRESSURE SHAFT AND PENSTOCKS 1194.69 1470.00 2664.69
6. POWER HOUSE COMPLEX 10763.68 175.88 10939.56
7. TAIL RACE CHANNEL 189.80 0.00 189.80
8. SWITCH YARD 1665.88 1665.88
9. ADITS 2146.06 7.14 2153.20
Total 63343.33 3770.45 67113.78
ADD FOR WORKS TAX @ 6.8% 4307.35 256.39 4563.74
GRAND TOTAL 67650.68 4026.84 71677.51
131

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
INTAKE STRUCTURE INCLUDING INTAKE TUNNEL UPTO
DESILTING CHAMBERS
S. No. Description Unit Quantity Rate Amount
( Rs. in
Lakhs)
1 Surface excavation
1.1 Common excavation Cum 2,500 125 3.13
1.2 Rock excavation Cum 45,000 300 135.00
2 Underground excavation Cum 62,000 1000 620.00
3 Rock stabilisation and supports
3.1 Rock bolts M 31,000 400 124.00
3.2 Steel Rib Supports MT 300 42000 126.00
3.3 Shotcreting Cum 5,400 4000 216.00
3.4 Concrete lagging Cum 400 7000 28.00
4 Concrete
4.1 Concrete Lining M20 Cum 15,000 4000 600.00
4.2 Concrete M15 Cum 5,000 2930 146.50
4.3 Backfill Concrete M20 Cum 6,000 3390 203.40
4.4 M25 Cum 41,000 3610 1480.10
5 Reinforcing Steel MT 3,600 27000 972.00
Sub Total(A) 4654.13
6 Miscellaneous and ancillary works
@1.5% of sub-total A
1.5% 69.81
Sub Total(B) 4723.94
7 Instrumentation @ 1% of sub-total B 1% 47.24
8 Dewatering @ 1% of sub total B 1% 47.24
9 Contingency @ 3% of sub-total B 3% 141.72
10 Work Charged establishment @
2% of Sub-total B
2% 94.48
Total Civil Cost 5054.61
132

DESILTING CHAMBERS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1 Surface excavation
1.1 Common excavation Cum 10,000 125 12.50
1.2 Rock excavation Cum 25,000 300 75.00
2 Underground excavation Cum 890,000 1000 8900.00
3 Rock stabilisation and supports
3.1 Rock bolts M 225,000 400 900.00
3.2 Steel Rib Supports MT 1,900 42000 798.00
3.3 Shotcreting Cum 33,000 4000 1320.00
3.4 Concrete lagging Cum 350 7000 24.50
4 Concrete
4.1 Concrete Lining M 20 Cum 85,000 4000 3400.00
4.2 Concrete Lining M 25 Cum 10,000 4500 450.00
4.3 Concrete in portals, backfill etc.
M15/A40 Cum 6,000 2930 175.80
M20 Cum 105,000 3390 3559.50
M25 Cum 15,000 3610 541.50
5 Reinforcing Steel MT 200 27000 54.00
Sub Total(A) 20210.80
6 Miscellaneous and ancillary works @
3.5% of sub-total A
3.5% 707.38
Sub Total(B) 20918.18
7 Instrumentation @ 1% of sub-total B 1% 209.18
8 Dewatering @ 2% of sub total B 2% 418.36
9 Contingency @ 3% of sub-total B 3% 627.55
10 Work Charged establishment @ 2%
of Sub-total B
2% 418.36
Total Civil Cost 22591.63
133

HEAD RACE TUNNEL
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1. Underground excavation Cum 430,000 1000 4300.00
2. Support System
2.1 Rockbolts m 210,000 400 840.00
2.2 Steel Rib Supports MT 2,200 42000 924.00
2.3 Shotcrete Cum 33,000 4000 1320.00
2.4 Concrete lagging Cum 2,800 7000 196.00
3 Concrete
3.1 Concrete Lining M-20 Cum 115,000 4000 4600.00
3.2 Concrete in portals, backfill etc.
3.3 M-15 Cum 5,000 2930 146.50
3.4 M-20 Cum 38,000 3610 1371.80
5 Reinforcing Steel MT 400 27000 108.00
6 Miscellaneous and ancillary works @
7.5% of sub-total A
7.5%
Sub-Total(A) 13806.30
1035.47
Sub-Total(B) 14841.77
7 Instrumentation @ 1% of sub-total B 1% 148.42
8 Dewatering @ 2% of sub total B 2% 296.84
9 Contingency @ 3% of sub-total B 3% 445.25
10 Work Charged establishment @ 2% of
Sub-total B
2% 296.84
Total civil works 16029.11
134

SURGE SHAFTS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Quantity Rate Amount
( Rs. in
Lakhs)
1 Surface Excavation
1.1 Common excavation Cum 3,000 125 3.75
1.2 Rock excavation Cum 9,000 300 27.00
2 Underground excavation
2.1 Surge Shaft Excavation Cum 85,000 1200 1020.00
2.2 Surge Shaft Excavation with raise borer Cum 814 1500 12.21
2.3 Concrete Lagging Cum 250 7000 17.50
3 Rock stabilisation & Supports
3.1 Rock bolts / anchors 25mm dia M 22,000 400 88.00
3.2 Shotcrete Cum 3,300 4000 132.00
3.3 Structural steel Rib MT 17542000 73.50
4 Concrete
4.1 Concrete M20 Cum 5,000 3390 169.50
4.2 M25 Cum 30,000 3610 1083.00
5 Reinforcing steel MT 2,80027000 756.00
Sub Total(A) 3382.46
6 Miscellaneous and ancillary works @
1.5% of sub-total A
1.5% 50.74
Sub Total(B) 3433.20
7 Instrumentation @ 1% of sub-total B 1% 34.33
8 Dewatering @ 2% of sub total B 2% 68.66
9 Contingency @ 3% of sub-total B 3% 103.00
10 Work Charged establishment @ 2% of
Sub-total B
2% 68.66
Total Civil Cost 3707.86
135

PRESSURE SHAFT AND PENSTOCKS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1 Underground excavation 33,000 1200 396.00
2 Rock stabilisation & Supports
2.1 Rock bolts / anchors 25mm dia M 17,000 400 68.00
2.2 Shotcrete Cum 2,600 4000 104.00
2.3 Structural steel Rib MT 125 42000 52.50
3 Concrete
3.1 Backfill concrete M 15 Cum 16,000 2930 468.80
Sub Total (A) 1089.30
4 Miscellaneous and ancillary
works @ 2.5% sub-total A
2.5% 27.23
Sub Total (B) 1116.53
5 Instrumentation @ 1% of sub-total B 1% 11.17
6 Dewatering @ 1% of sub total B 1% 11.17
7 Contingency @ 3% of sub-total
3% 33.50
B
8 Work Charged establishment @
2% of Sub-total B
2% 22.33
Total Civil Cost 1194.69
136

POWER HOUSE COMPLEX
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Quantity Rate Amount
( Rs. in
Lakhs)
1 Surface Excavation
1.1 Common Excavation Cum 135,000 125 168.75
1.2 Rock Excavation Cum 400,000 300 1200.00
2 Rock stabilization and Supports including accessories
2.1 Rockbolts M 20,000 400 80.00
2.2 Shotcrete Cum 6,000 4000 240.00
3 Concrete including formwork
3.1 M-15 Cum 4,000 2930 117.20
3.2 M-20 Cum 80,000 3390 2712.00
3.3 M-25 Cum 40,000 3610 1444.00
4 Reinforcing Steel MT 12,500 27000 3375.00
5 Structural Steel MT 400 42000 168.00
6 Masonry Work
Stone Cum 500 2000 10.00
Brick Cum 800 2000 16.00
Stone pitching Cum 800 781 6.25
Sub Total(A) 9537.20
7 Miscellaneous and ancillary works @
4.5% of sub-total A
4.5% 429.17
Sub Total(B) 9966.37
8 Instrumentation @ 1% of sub-total B 1% 99.66
9 Dewatering @ 2% of sub total B 2% 199.33
10 Contingency @ 3% of sub-total B 3% 298.99
11 Work Charged establishment @ 2% of
Sub-total B
2% 199.33
Total Civil Cost 10763.68
137

TAIL RACE CHANNEL
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1 Surface excavation
1.1 Common excavation Cum 15,000 125 18.75
1.2 Rock excavation Cum 15,000 300 45.00
1.3 Embankment Construction Cum 3,000 518 15.54
2 Concrete including formwork
2.1 M20 Cum 1,500 3390 50.85
3 Reinforcing Steel MT 100 27000 27.00
4 Masonry Work
Stone Cum 100 2000 2.00
Brick Cum 100 2000 2.00
Stone pitching Cum 300 781 2.34
Sub-Total(A) 163.48
5 Miscellaneous and ancillary works @
7.5% of sub-total A
7.5% 12.26
Sub-Total(B) 175.74
6 Instrumentation @ 1% of sub-total B 1% 1.76
7 Dewatering @ 2% of sub total B 2% 3.51
8 Contingency @ 3% of sub-total B 3% 5.27
9 Work Charged establishment @ 2% of
Sub-total B
2% 3.51
Total civil works 189.80
138

SWITCH YARD
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description Unit Qty. Rate Amount
( Rs. in
Lakhs)
1 Surface excavation
1.1 Common excavation Cum 55,000 125 68.75
1.2 Rock excavation Cum 55,000 300 165.00
1.3 Backfilling Cum 185,000 356 658.60
2 Concrete including form work
2.1 M-15 Cum 1,000 2930 29.30
2.2 M-20 Cum 4,000 3390 135.60
2.3 M-25 Cum 6,000 3610 216.60
3 Reinforcing Steel MT 600 27000 162.00
4 Structural steel MT 100 42000 42.00
5 Stone / Brick Masonry Cum 600 2000 12.00
Sub Total(A) 1489.85
6 Miscellaneous and ancillary
works @ 4.5% of sub-total A
4.5% 67.04
Sub Total(B) 1556.89
7 Dewatering @ 2% of sub total B 2% 31.14
8 Contingency @ 3% of sub-total B 3% 46.71
9 Work Charged establishment @
2% of Sub-total B
2% 31.14
Total Civil Cost 1665.88
139

ADITS
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. Description Unit Quantity Rate Amount
No.
( Rs. in
Lakhs)
1 Surface Excavation at Portals
1.1 Common excavation Cum 7,000 125 8.75
1.2 Rock excavation Cum 24,000 300 72.00
2 Underground excavation Cum 80,000 1000 800.00
3 Rock stabilisation and supports
3.1 Rockbolts/Rock anchor 25 mm dia M 60,000 400 240.00
3.2 Shotcrete Cum 6,500 4000 260.00
3.3 Structural steel Rib MT 400 42000 168.00
4 Concrete
4.1 Concrete in portals, backfill etc.
M-15 Cum 2,500 2930 73.25
M-20 Cum 6,000 3390 203.40
5 Reinforcing steel MT 350 27000 94.50
Sub Total (A) 1919.90
6 Miscellaneous and ancillary works @ 3.5%
of sub-total A
3.5% 67.20
Sub-Total(B) 1987.10
7 Instrumentation @ 1% of sub-total (B) 1% 19.87
8 Dewatering @ 2% of sub total (B) 2% 39.74
9 Contingency @ 3% of sub-total (B) 3% 59.61
10 Work Charged establishment @ 2% of
Sub-total B
2% 39.74
Total Civil Cost 2146.06
140

S.
No.
HYDRO MECHANICAL EQUIPMENT
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Detail of Items UnitQuantity Rate
(Rs.)
Amount
in Lacs
1 Diversion tunnel gate & hoist
Gate (Fixed wheel type) (4.5m x 10.75m)- 4 No. Ton 300 60000 180.00
Embedded Parts - 4 Set Ton 108 50000 54.00
Ropedrum hoist 200 T Capacity - 4 Set Ton 280 100000 280.00
Hoist Supporting structure and trestle - 4 Set Ton 280 50000 140.00
2 Spillway structure
a) Lower spillway Radial Gates (9.75m x 11.5m) - 5 Nos. Ton 950 100000 950.00
Embedded Parts (including anchorages, hoist
structure) including breast wall liners - 5 Set
Ton 600 50000 300.00
Hydraulic Hoist (One power pack + Two cylinders of Set
220T Cap. each)
5 18500000 925.00
b) Bulkhead Gate( Fixed Wheel type) 9.75m x 13.5m - 1 Ton
No.
210 60000 126.00
Embedded Parts - 5Set Ton 325 50000 162.50
Lifting Beam Ton 50 50000 25.00
Gantry crane 490 T capacity with cross travel
arrangement
Set 1 54000000 540.00
Portable oil filter unit along with Contamination
checking kit & Low vacuum dehydration and
degassification unit
Set 1 1000000 10.00
Portable trolley mounted gasoline engine operated
power pack
Set 1 1500000 15.00
c) Upper Spillway Radial Gates (9.75m x 11.5m) - 2
Nos.
Ton 124 100000 124.00
Embedded Parts (including anchorages, hoist
structure) including breast wall liner - 2 Set
Ton 90 50000 45.00
Hydraulic Hoist (One power pack + Two cylinder of
70T Cap.each)
d) Spillway Bulkhead (Lower spillway bulkhead to be
used)
Set 2 6500000 130.00
Embedded Parts - 2 Set Ton 32 50000 16.00
3 Intake structure
a) TrashRacks and Embedded parts (18m x 20m) - 2 Set Ton 204 50000 102.00
Trash rack cleaning machine Set 1 10000000 100.00
b) Intake gate(fixed wheel type) including ballast (7.5m Ton 300 60000 180.00
x 8.5m) - 2 No.
Embedded Parts -2 Set Ton 90 50000 45.00
Rope drum hoist 250T Cap.- 2 Sets Ton 176 100000 176.00
Hoist platform and trestle - 2 Sets Ton 176 50000 88.00
141

4 Desilting Chamber Gates
Inlet Gates
Gate (Fixed Wheel Type) including ballast 6.0m
x6.0m - 4No.
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Ton 240 60000 144.00
Embedded parts - 4 Set Ton 80 50000 40.00
Rope drum hoist 120T Capacity- 4 Sets Ton 168 100000 168.00
Hoist platform and Trestles - 4 Sets Ton 168 50000 84.00
Outlet Gates
Gate (Slide Type) 5.3m x5.3m - 2No. Ton 64 60000 38.40
Embedded parts - 4 Set Ton 40 50000 20.00
Lifting Beam Ton 6 50000 3.00
EOT Crane 60T Cap. Set 1 5400000 54.00
5 Silt Flushing Gates (Slide Type)
Gates (Service & Emergency) 2.5m x2.0m - 8
Nos.
Embedded parts (including bonnet, bonnet
cover,gate body liner etc.)-2Set
Hydraulic Hoist ( Two Double acting cylindres
of 300T Cap. each + one common power pack )
Ton 64 100000 64.00
Ton 144 50000 72.00
Set 4 10500000 420.00
6 Surge shaft gate & hoist
Gate (Slide Type) 6.25m x8.25m - 2 No. Ton 132 60000 79.20
Embedded parts - 2 Set Ton 56 50000 28.00
Rope drum hoist 105T Cap.- 2 Set Ton 74 100000 74.00
Hoist platform and trestle - 2 Set Ton 74 50000 37.00
7 Draft Tube gates & hoist
Gate (Fixed Wheel type) 5.0m x4.3m - 8 No. Ton 160 60000 96.00
Embedded Parts - 8 Set Ton 56 50000 28.00
Lifting Beam Ton 3 50000 1.50
Gantry Crane 35T Cap. Set 1 4200000 42.00
8 Pressure shaft steel Liner
Steel Liner including transition and bifurcations -
2 No. (IS 2002 Gr. 3)
Ton 2000 70000 1400.00
9 Adit Gates
Adit gates (2.5m x2.5m) - 1 Nos. Ton 8 60000 4.80
Embedded Parts - 1 Set Ton 4 50000 2.00
10 Instruments and Remote Control Set 1 10000000 100.00
11 D G Set 500 KVA Set 1 2500000 25.00
7738.40
Add 5% for contingencies, spares and bypass
Valves
5% 386.92
Grand Total 8125.32
142

S.
No.
K - BUILDINGS
Description Unit Total
Plinth
Area
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Rate (Rs.) Amount
(Rs. in
Lakhs)
1. Residential Building
C/o Permanent residential buildings Sqm 35000 7000 2450.00
Service charges @ 31% 759.50
Total Residential Buildings
2. Non-Residential Building
C/o Permanent non-residential buildingsSqm. 30000 5500 1650.00
Service charges @ 22.50% 371.25
Total Non-Residential Buildings
(Residential + Non-Residential)
Add for Works Tax @ 6.8% 355.69
Grand Total 5586.44
143

Q-Spl T&P for Infrastructure Development
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Description of equipment Quantity Rate Amount
(Nos.) (Rs in Lacs)
1 Hydraulic Excavator, 1.0 cum. 1 50.00 50.00
2 Loader cum Excavator, 1.0/0.25 cum. 2 18.00 36.00
3 Crawler Dozer, 200 FHP with ripper 1 85.00 85.00
4 Crawler Dozer, 100 FHP 1 55.00 55.00
5 Wheel Dozer, 300 FHP 1 95.00 95.00
6 Motor Grader, 145 FHP 1 60.00 60.00
7 Air Track/Wagon Drill 2 15.00 30.00
8 Jack Hammer/Pavement Breaker 5 0.35 1.75
9 Diamond Core Drill (Mechanical) 1 15.00 15.00
10 Diamond Core Drill (Hyd) 1 60.00 60.00
11 Compressed Air(cfm) 2000 0.0125 25.00
12 Rock splitter 1 10.00 10.00
13 Hyd. Rock breaker 1 60.00 60.00
14 Mobile Crane, 10 t Pick & Carry 1 10.00 10.00
15 Mobile Crane, 20 t (Rough terrain) 1 60.00 60.00
16 Fork Lift, 5t 1 15.00 15.00
17 Fork Lift, 8t/10T 1 25.00 25.00
18 Road Roller, 8/10 t 2 10.00 20.00
19 Concrete Mixer, 14/10 cft 1 1.50 1.50
20 Concrete Mixer, 28 NT 1 4.00 4.00
21 Dewatering Pump L.S 20.00 20.00
22 Submersible cutter pump 1 100.00 100.00
23 Tipper 4.5/6.0 cum. 8 9.00 72.00
24 Truck, 10 t 8 8.00 64.00
25 Low Bed Tractor Trailor, 30 t 1 45.00 45.00
26 Explosive Van, 10 t 1 10.00 10.00
27 Water Tanker/Sprinkler, 10 KL 4 12.00 48.00
28 Petrol/Diesel Tanker, 10 KL 2 12.00 24.00
29 Bus/Mini Bus 6 8.00 48.00
30 Car/MUV 6 4.50 27.00
31 Jeep (Petrol/Diesel) 30 4.50 135.00
32 Ambulance 2 8.00 16.00
33 Workshop Equipment L.S 20.00 20.00
34 Fire Tender 2 15.00 30.00
35 Recovery Van 1 5.00 5.00
36 Pick up Van/L.C.V 4 5.50 22.00
37 Motor boat 2 5.00 10.00
38 Barges with travwlers 2 10.00 20.00
39 Motorised winch 100 HP 2 5.00 10.00
40 Motorised winch 200 HP 2 10.00 20.00
1464.25
144

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
DISTRIBUTION OF COST UNDER HEAD Q - SPECIAL T & P AND V -
RECEIPT & RECOVERIES
Cost Q R&R
(Rs. In lakhs)
Cost of equipments excluding inspection vehicles 1208.25 302.06 226.55
Cost of inspection vehicles 256.00 256.00 51.20
Provision under head Q - Spl. T&P 1464.25 558.06
Recoveries to be shown under V- Receipt and
Recoveries
277.75
145

S.
No.
R- COMMUNICATION
Description Length
(km)
A New Road
1Approach road connecting
Dam Site , PH site, Adits etc
on right bank & quarry site/
muck disposal etc on left
bank of river Singit
2Road for Township and
Store area
Rate (Rs. In
lakhs)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
Amount
(Rs. in
Lakhs)
25 90.00 2250.00
a)Township area
i) Two lane 5 120.00 600.00
ii) Single lane 10 90.00 900.00
b)Store area
i) Two lane 1 120.00 120.00
ii) Single lane 4 90.00 360.00
Subtotal "A" 4230.00
B 1 Widening and strengthening
of existing Road from
Dengser damsite to Nalo
damsite and miscellaneous
stretches
2 Bridge on river Singit
Bailey Bridge Near Damsite
and Power House
25 50 1250.00
2 X 0.12 L.S. 400.00
Total (A+B) 5880.00
Add for Works Tax @ 6.8% 399.84
Grand Total 6279.84
146

V - RECEIPT & RECOVERIES
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
S. No. Item Amount
(Rs. In Lakhs)
1. Recovery from the Sale of Equipments 277.75
Total 277.75
147

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
148

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
149

13.0 ECONOMIC EVALUATION
CHAPTER – XIII
ECONOMIC EVALUATION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The Project has been contemplated as a run-off the river scheme on
river Subansiri/Si Ngit. The project is estimated to cost Rs. 2609.66
crores excluding IDC at June 2003 Price Level. Sale price of energy
generated at powerhouse bus bars has been worked out as Rs. 3.71
per unit with free power to home state (Table 13.2) and Rs. 3.27 per
unit without free power to home state (Table 13.2-A).
13.1 ECONOMIC JUSTIFICATION
The energy generation of the project with an installed capacity of
(4 x 90) MW has been estimated at 1732.99 MU in a 90% dependable
year.
13.2 COST ESTIMATES AND PHASING OF EXPENDITURES
The cost of construction of the project has been estimated at June 2003
price level with a construction schedule of 7.5 years including 1.5 years for
Infrastructure works during stage-II activity.
The estimated Present Day Cost of the project is Rs. 2609.66 Crores
without IDC at June 2003 Price level.
13.3 PHASING OF EXPENDITURE
The phasing of expenditure has been worked out on the basis of
anticipated construction programme.
150

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The phasing of expenditure without IDC for the present cost is shown as
below:
Year Estimated Cost at June 2003 P.L.
(Rs. in Crores)
1 st 104.39
2 nd 208.77
3 rd
234.87
4 th 339.26
5 th 391.45
6 th 574.13
7 th 469.74
7.5 th 287.06
Net Cost 2609.67
13.4 INTEREST DURING CONSTRUCTION (IDC)
Based upon above phasing of expenditure the interest during construction
(IDC) have been calculated with 70:30 debt equity ratio and 10.0% interest
on loan. (Table 13.1)
The estimated IDC with estimated present cost is Rs 312.48 Crores
151

13.5 COST OF ENERGY GENERATION
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
The cost of energy generation has been calculated for the annual energy
generation in a 90% dependable year based upon following assumptions.
1. Debt-equity ratio 70 : 30
2. Annual interest rate on loan 10.0%
3. Return on equity 16%
4. Annual interest rate on working capital 10.0%
5. O&M Charges 1.5% of Project Cost
6. Free power to Home State 12% of the energy available
after losses
7. Depreciation considered 1/12 th of loan amount during
loan repayment period.
The levellised tariff of the Project at present day cost works out to be
Rs.3.01 Per Unit with free power to home state (Table 13.3) and Rs. 2.65
per unit without free power to home state (Table 13.3-A).
152

Table 13.1
STATEMENT SHOWING IDC CALCULATION AT PRESENT DAY COST (JUNE 2003 LEVEL)
PRESENT DAY COST 2609.66 Crs. Transmission Works 62.31 Crores
Civil Works 2212.47 Crs. Electrical Works 334.89Crs.
INTEREST RATE PER ANNUM 10% Transmission cost 62.31 Crs.
(Rs. in Crs.)
Present Day Amount Receivable I.D.C Loan Outstanding Amount Receivable
Year Cost Equity Loan at the end of Equity Loan
year (for the year)
1 2 3 4 5 6 7 8
1 104.39 104.39 104.39
2 208.77 208.77 208.77
3 234.87 234.87 234.87
4 339.26 328.61 10.64 0.02 10.66 328.61 10.66
5 391.45 391.45 20.64 422.75 412.09
6 574.13 574.13 70.98 1067.85 645.11
7 469.74 469.74 130.27 1667.87 600.01
7.5 287.06 287.06 90.57 2045.50 377.63
Total 2609.66 876.64 1733.02 312.48 876.64 2045.50
IDC 312.48 Crs. Equity 876.64 Crs.
Net cost of the project 2922.14 Crs. Loan 2045.50 Crs.
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
153

TABLE-13.2
UNIT COST OF ENERGY AT BUS BAR AT CURRENT PRICE LEVEL
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
(June 2003 P.L.) With 12% Free Power to Home State
(Based on 16% return on equity & 10% interest on loan, 10% interest on working
1 Installed capacity 360 MW
2 Cost of the Project (Net) Rs. 2609.66 Crores
3 Interest During Construction Rs. 312.48 Crores
4 Total Cost of Project Rs. 2922.14 Crores
(Including IDC)
a) Equity 30% Rs. 876.64 Crores
b) Loan 70% Rs. 2045.50 Crores
5 Annual Energy Generation 1732.99 MU
6 0.7% As Auxiliary Consumption of No. 5 0.50% 8.66 MU
7 Energy Available After Auxiliary Consumption 1724.33 MU
8 0.5% As Transformer Loss of No. 7 0.50% 8.62 MU
9 Energy Available After Transformer Loss 1715.70 MU
10 Free Power to Home State 12% 205.88 MU
11 Energy Available After Allowing Free Power 1509.82 MU
12 Fixed and Running Charges
A) Capacity Charges
a) Interest on Loan 10.00% 196.03 Crores
b) Depreciation Charges 170.46 Crores
(Limited to 1/12 th of Loan Amount)
SUB-TOTAL 366.49 Crores
B) Energy Charges
a) O&M Charges 1.50% 43.83 Crores
b) Return on Equity 16.00% 140.26 Crores
SUB-TOTAL 184.09 Crores
c) Interest on Working Capital 10.00% 9.70 Crores
I) O&M Charges for 1 month 3.65
II) 2 Months Average Billing 93.38
TOTAL Rs. 560.29 Crores
13 Sale Price at Bus Bar/Unit 3.71 Rs.
14 Cost of Generation at Bus Bar/Unit 2.45 Rs.
(Without Allowing Free Power to Home State and Return on Equity)
Note : This unit rate is excluding water cess, income tax incentive, penalties etc.
154

TABLE-13.2 A
UNIT COST OF ENERGY AT BUS BAR AT CURRENT PRICE LEVEL
(June 2003 P.L.) WITHOUT FREE POWER TO HOME STATE
(Based on 16% return on equity & 10% interest on loan, 10% interest on working capital)
Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
1 Installed capacity 360 MW
2 Cost of the Project (Net) Rs. 2609.66 Crores
3 Interest During Construction Rs. 312.48 Crores
4 Total Cost of Project Rs. 2922.14 Crores
(Including IDC)
a) Equity 30% Rs. 876.64 Crores
b) Loan 70% Rs. 2045.50 Crores
5 Annual Energy Generation 1732.99 MU
6 0.7% As Auxiliary Consumption of No. 5 0.50% 8.66 MU
7 Energy Available After Auxiliary
1724.33 MU
C i
8 0.5% As Transformer Loss of No. 7 0.50% 8.62 MU
9 Energy Available After Transformer Loss 1715.70 MU
10 Free Power to Home State 0% 0.00 MU
11 Energy Available After Allowing Free Power 1715.70 MU
12 Fixed and Running Charges
A) Capacity Charges
a) Interest on Loan 10.00% 196.03 Crores
b) Depreciation Charges 170.46 Crores
(Limited to 1/12 th of Loan Amount)
SUB-TOTAL 366.49 Crores
B) Energy Charges
a) O&M Charges 1.50% 43.83 Crores
b) Return on Equity 16.00% 140.26 Crores
SUB-TOTAL 184.09 Crores
c) Interest on Working Capital 10.00% 9.70 Crores
I) O&M Charges for 1 month 3.65
II) 2 Months Average Billing 93.38
TOTAL Rs. 560.29 Crores
13 Sale Price at Bus Bar/Unit 3.27 Rs.
14 Cost of Generation at Bus Bar/Unit 2.45 Rs.
(Without Allowing Free Power to Home State and Return on Equity)
Note : This unit rate is excluding water cess, income tax incentive, penalties etc.
155

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
156

Preliminary Feasibility Report
Nalo HE Project (4 x 90 MW)
157

SALIENT FEATURES
1 LOCATION
State : Arunachal Pradesh
District : Upper Subansiri
River : Subansiri/Singit
Dam site : 1.6 km u/s of
Ledi Ishi Nallah
Nearest BG rail head : Nagaon
Nearest airport : Lilabari(North Lakhimpur)
2 HYDROLOGY
Catchment area : 14500 sq.km.
Location of catchment :
Latitude 27 o 50’ N to 29 o 00’ N
Longitude 91 o 45' E to 93 o 49' E
Average annual rainfall : 2810 mm
3 RESERVOIR
Full reservoir level
(FRL)
: EL 765 m
Min.Draw Down Level
(MDDL)
Gross storage
: EL 745 m
-at FRL : 163.37 mcm
-at MDDL
Area under
: 113 mcm
submergence at FRL : 283.8 ha
4 DIVERSIONTUNNEL
Number : 2
Size : 10.75 m
Shape : Horse shoe
Length : 650/800 m
Diversion capacity
(assumed)
: 2600 cumec
U/s coffer dam : 28 m
D/s coffer dam : 14 m
Annexure 1.1
1-4
174

5 DAM
Type : Concrete
Top elevation of dam
Height of dam above
: EL 770 m
deepest foundation level : 125 m
Length of dam at top : 366 m
River Bed level EL 660 m
SPILLWAY
Design flood
Lower spillway
: 12300 cumec
Crest elevation EL 715 m
Type : Orifice
Number 5
Size of opening
Upper spillway
9.75 x 11.5 m
Crest elevation EL 753.5 m
Type : Crest
Number 2
Size of opening 9.75 x 11.5 m
Energy dissipation : Ski jump with preformed
plunge pool
Length of spillway : 120 m
6 INTAKE
Invert level : EL 725 m
Number : 2
Size of gate opening : 7.5 x 8.5 m
Trash rack : 18 x 20 m
Intake tunnel 8.5 m
Intake tunnel length 250/350 m
7 DESILTING CHAMBERS
Number : 4
Size : 17 x 25 m
Length : 300 m
Design discharge
per chamber
: 111.8 cum
Particle size to be removed : 0.2 mm and above
8 HEAD RACE TUNNEL
Number : 2
Size : 7.5 m
Shape : Horse shoe
Length : 2.5 /2.6 km
Design discharge
per tunnel
: 186.4 cumec
Annexure 1.1
2-3
175

9 SURGE SHAFT
Number : 2
Size : 20 m
Height : 90 m
10 PRESSURE SHAFT
Number 2
Size 6.25 m
Vertical height 82 m
11 POWER HOUSE
Type : Surface
Installed capacity : 360 MW
Number of units : 4 (90MW each)
Power house size
(machine hall + service bay)
: 103 (L)x 22 (W) x 47 (H)
Type of turbine : Vertical Shaft Francis
C.L of turbine : EL 633 m
Draft tube opening for :
each unit 2 nos, 5 m (W) X 4.3m(H)
12 TAIL RACE CHANNEL
Bed Width 60 m
Side Slope 1V:1.5H
Design discharge : 372.8 cumec
River Bed level EL 635 m
Maximum TWL EL 645 m
13 SWITCH YARD
Size : 80m (W) X160m(L)
14 POWER GENERATED
Installed capacity
Annual energy generation
: 360 MW
in 90% dependable year : 1732.99 MU
Annexure 1.1
3-3
176

Reply to the comments of HP&I Division, CEA vide letter No.
7/9/NHPC/HP&I/2004/695 dt.6.2.2004
Nalo H.E Project (4×90 MW)
Annexure-2.3
3-5
Comments Reply
General Comments
1 It may be ensured that the Initial Initial Environmental studies have been
Environmental studies incorporated in the carried out through National Remote
PFR are as per scope of the work for PFR. Sensing Agency (NRSA), Hyderabad as
per scope of work and same are
incorporated in PFR.
2. It may be ensured that the Financial
Parameters are taken as per guidelines sent
vide our Lr. No. 7/9/HP&I-2003/1118-
1123, dated 21 st October, 2003.
3. It may be ensured that the Cost Estimates
prepared are as per the guidelines sent
vide our Lr. No. 7/9/HP&I/2003/1163-
1172, dated 24.10.2003
4. NHPC may indicate recommendations for
further studies required wherever
necessary in the relevant chapters of PFRs
for consideration during FR/DPR stage.
5. It may be ensured that the Installed
Capacities & Assessment of power
benefits takes into account various
comments and advise given in this regard.
Guidelines have been followed.
Cost estimates have been prepared as
per the guidelines.
Recommendations for further studies
have been incorporated in the relevant
chapters of PFR.
Installed capacity and assessment of
power benefits have been vetted by CEA
and comments have been taken into
account. (Annexure 7.1)
183

6. It may be ensured that the hydrology
adopted is approved by CWC.
.
7. The layout planning of project
components may take into account the
views & advice of CWC.
8. The power evacuation arrangements
considered in the PFR should take into
account views and suggestions of SP &
PA Division of CEA.
9. An Executive Summary may be prepared
as per general guidance sent vide our Lr.
No. 7/9/HPI-2003/1412-1419 dated 2 nd
December, 2003.
Power Potential Studies
1. Utilization of 5m drop between TWL (770)
of upstream Naba HEP& proposed FRL
(765m) of Nalo HEP may be kept in view
at FR/DPR stage.
2. The TWL (645m) has been fixed
considering river bed level (635m) of the
proposed power house. The TWL would
have to be reviewed at FR/DPR stage.
Annexure-2.3
4-5
Hydrology chapter submitted to CWC.
Replies to comments received are
appended with PFR.
Comments of CWC on project
components received. Replies to
comments received are appended with
PFR.
Comments on power evacuation
arrangements by CEA have been taken
into account while finalizing PFR.
Executive summary (chapter-I) has been
prepared as per CEA’s guidelines.
Noted
Noted
184

3. It is presumed that the selection of unit size
of 130 MW takes into account
transportation constraints etc.
4. NHPC may indicate recommendations for
further studies required for preparation of
FR/DPR.
Annexure-2.3
5-5
The unit size is 90 MW instead of 130
MW as mentioned in the comments of
CEA. The unit size of 90 MW has been
taken considering transport constraints
of this project.
Recommendations for further studies
required for preparation of FR/DPR are
given in PFR.
185

SUBANSIRI BASIN PROJECTS
Annexure-5.1A
MONTHLY RAINFALL (MM) AT TALIHA
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Annual
1968 83.0 167.9 183.4 169.1 353.1 258.0 530.1 346.6 113.0 128.0 3.0 2335.2
1969 75.0 164.1 348.1 221.3 347.2 333.6 488.2 41.3 2018.8
1976 99.1 181.9 215.7 417.7 504.0 341.2 211.8 220.1 124.2 128.0 2443.7
1977 58.9 124.4 141.1 450.1 357.7 357.4 344.2 319.2 310.6 165.3 60.0 49.5 2738.4
1978 37.3 71.1 174.4 458.1 318.8 437.0 342.1 161.2 422.4 108.4 76.6 2607.4
1979 40.8 144.1 182.4 272.4 155.7 333.0 471.4 339.3 315.4 145.8 36.8 184.7 2621.8
1980 139.5 219.9 241.8 251.4 69.7 287.4 268.0 29.6 20.7 1528.0
1981 128.4 126.5 189.2 127.5 569.7 488.7 724.4 130.7 65.7 68.7 45.6 51.7 2716.8
1982 0.5 93.2 167.5 34.0 36.5 49.6 110.9 113.4 265.1 26.2 33.3 0.0 930.2
1983 0.0 241.7 419.7 247.7 582.9 521.7 2013.7
1985 157.5 263.3 74.0 7.3 52.6 554.7
1986 75.1 147.9 223.0
1997 36.7 170.0 99.8 293.4 280.4 146.8 269.6 118.2 126.8 123.2 1664.9
2000 498.4 400.0 161.4 96.8 5.0 1161.6
2001 38.2 83.6 141.0 610.0 275.8 358.2 305.5 376.0 486.7 245.7 132.9 20.0 3073.6
2002 184.5 69.5 184.0 464.6 98.6 270.7 475.8 363.3 335.0 46.6 34.0 26.6 2553.2
2003 40.8 104.2 171.6 267.1 279.8 417.0 1280.5
AVG 62.5 116.1 186.2 283.7 286.5 315.5 373.3 281.0 294.3 123.7 66.7 49.3 2438.8
195

SUBANSIRI BASIN PROJECTS
MONTHLY RAINFALL(MM) AT SIYUM
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL
1966 11.4 122.0 200.0 293.0 217.0 604.0 372.0 356.0 129.4 2304.8
1968 69.0 90.1 187.0 188.0 383.0 511.0 615.0 284.1 406.0 319.0 80.0 3132.2
1969 37.0 193.0 216.0 292.0 604.0 567.0 418.0 132.0 4.0 88.0 2551.0
2001 381.0 475.3 540.7 244.2 93.4 20.0 1754.6
2002 92.2 44.0 281.6 316.7 391.1 495.0 766.7 354.3 333.5 95.5 15.0 28.3 3213.9
AVG 40.2 83.0 193.3 232.3 297.3 573.0 483.8 392.5 358.7 189.1 97.7 20.0 2960.9
196
Annexure-5.1B

SUBANSIRI BASIN PROJECTS
MONTHLY RAINFALL(MM) AT LIMEKING
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL
1966 169.6 209.0 516.6 558.6 385.2 1839.0
1968 25.0 69.0 149.0 98.0 332.0 448.1 449.0 399.0 362.0 134.0 2465.1
1969 48.2 100.0 166.1 330.0 503.1 502.0 394.5 331.0 2374.9
1977 55.7 519.8 458.0 334.1 134.3 1501.9
1978 19.1 55.7 33.8 111.4 381.6 548.6 461.4 206.0 456.3 139.0 67.7 21.8 2502.4
1979 296.9 140.2 227.2 325.3 540.2 733.0 511.6 599.2 525.0 380.6 64.0 58.6 4401.8
1980 183.9 123.0 416.0 464.2 588.6 955.3 663.8 548.1 339.0 153.2 18.2 4453.3
2001 241.4 503.0 345.7 177.8 28.6 1296.5
2002 33.9 37.9 120.7 64.8 306.6 563.9
AVG 111.8 79.0 174.5 199.9 384.0 537.2 488.5 444.0 384.8 186.5 44.6 40.2 3074.8
197
Annexure-5.1C

SUBANSIRI BASIN PROJECTS
MONTHLY RAINFALL(MM) AT NACHO
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL
2001 6.5 62.4 117.3 239.9 340.2 504.6 427.0 694.1 573.5 204.1 72.9 13.3 3255.8
2002 45.6 57.7 149.4 153.0 279.7 492.2 389.5 239.4 242.9 63.2 21.0 28.2 2161.8
2003 15.3 57.7 149.4 126.3 230.9 750.5 460.2 487.1 458.6 86.1 42.2 11.8 2876.1
Average 22.5 59.3 138.7 173.1 283.6 582.4 425.6 473.5 425.0 117.8 45.4 17.8 2764.6
198
Annexure-5.1D

SUBANSIRI UPPER PROJECT
SYNTHETIC 10-DAILY FLOW SERIES AT MENGA (NHPC)
Annexure-5.2
1-2
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC AVG
I 123.66 154.30 206.02 307.57 451.79 939.71 1225.37 1887.91 1096.25 481.27 295.36 152.72
1 II 137.62 171.89 252.37 273.85 303.63 1634.30 1923.30 1842.40 1383.00 848.96 214.49 153.68 699.69
III 144.25 187.98 224.34 466.39 679.70 2488.75 1669.53 1191.39 834.66 463.75 231.60 145.23
I 157.69 141.97 137.83 236.77 458.14 1080.84 1426.26 953.11 700.89 515.48 426.81 194.40
2 II 125.49 159.86 155.05 305.37 733.33 1383.18 1435.49 1043.84 1177.66 494.41 361.80 154.85 587.76
III 129.38 151.64 139.60 369.15 569.91 1665.93 1164.20 1199.76 1023.01 450.75 208.86 126.69
I 133.55 135.09 182.34 364.76 361.59 520.42 1021.56 896.36 2714.33 1123.44 339.75 231.30
3 II 146.66 153.94 219.07 292.58 460.99 828.84 1001.09 933.62 2447.16 771.73 205.22 195.34 642.13
III 131.13 135.92 254.14 354.79 343.50 870.63 796.39 1719.52 1875.50 558.47 228.92 166.86
I 158.00 137.23 164.07 308.23 671.79 511.40 1527.47 1489.72 696.41 556.04 245.99 150.51
4 II 151.80 132.98 218.75 437.73 786.19 962.93 2481.76 1179.78 616.18 781.38 201.08 163.78 611.58
III 138.01 144.06 278.59 576.70 446.16 1271.38 1882.74 967.55 803.65 431.11 185.94 159.96
I 127.68 106.96 127.04 261.34 460.92 909.43 2072.20 1373.69 909.59 1196.20 292.01 206.39
5 II 101.66 97.14 130.18 311.29 569.13 1423.40 1858.70 1205.15 760.40 1192.55 232.82 150.61 670.96
III 95.81 133.23 144.61 333.65 1024.53 1610.08 1486.31 1462.35 850.13 580.24 199.44 157.54
I 133.17 167.23 230.61 325.96 360.82 398.94 1027.24 1329.81 1056.48 1073.63 390.16 154.77
6 II 139.44 171.90 221.23 313.84 507.00 436.35 822.48 1476.93 815.43 972.77 226.81 158.47 519.03
III 140.28 180.86 181.02 274.83 325.35 540.80 1286.16 1351.53 662.26 502.89 196.54 130.97
I 98.02 143.82 158.56 221.11 593.53 564.16 1107.43 629.07 571.51 729.61 281.62 270.40
7 II 117.08 133.57 144.93 284.39 544.95 661.80 1595.40 803.41 697.14 383.68 308.50 184.53 494.06
III 129.85 125.95 138.29 352.33 620.69 945.70 1958.74 742.34 804.00 308.52 279.26 152.33
I 174.75 194.50 194.86 324.57 569.28 2148.90 2811.71 1231.36 1271.46 1022.18 496.67 177.27
8 II 163.54 145.07 180.85 338.53 870.97 2686.49 3102.75 1389.81 909.74 1102.44 425.20 187.60 951.59
III 176.76 150.71 229.53 253.12 1270.38 2408.62 3908.05 1523.02 1267.89 500.80 280.03 167.84
I 152.54 102.39 180.23 197.11 417.90 386.42 1698.96 1627.47 1154.06 1244.62 311.46 140.54
9 II 121.76 94.96 188.32 345.55 296.84 368.19 1324.80 2079.22 1039.96 532.05 325.81 146.07 603.79
III 114.66 99.03 164.93 371.45 474.02 593.60 1898.80 1539.58 1124.19 554.68 203.20 121.18
I 96.98 116.74 235.82 234.11 367.88 273.10 1158.67 749.35 733.23 964.53 221.50 157.20
10 II 90.92 147.71 186.00 278.93 272.04 568.06 893.53 1149.74 1366.95 513.73 258.84 127.91 490.48
III 95.44 142.54 189.17 283.71 315.61 703.30 1422.52 1025.41 1717.59 300.81 182.91 114.91
199

Annexure-5.2
2-2
I 87.90 119.60 158.37 219.11 569.68 487.73 788.20 1014.55 1729.96 1269.70 326.71 171.77
11 II 86.23 93.71 225.98 219.58 689.52 553.01 1360.74 1109.88 1894.12 481.71 280.09 201.21 590.27
III 89.75 147.28 209.78 270.14 653.10 514.53 994.26 1831.52 1516.36 452.40 254.03 177.65
I 204.59 176.47 188.58 304.04 616.52 654.82 1350.12 819.48 1487.72 671.95 230.24 196.13
12 II 206.03 178.32 169.24 350.57 529.79 796.45 1077.28 1113.20 1572.22 748.04 218.26 150.20 609.24
III 194.82 163.67 194.30 349.68 297.35 1137.94 1764.83 1969.14 1159.34 378.65 178.89 133.64
I 101.10 135.26 192.63 308.78 383.25 624.52 933.77 1822.37 772.81 1088.59 316.53 150.02
13 II 101.86 100.72 249.97 297.95 367.85 588.79 1464.80 2379.30 722.63 472.93 300.75 155.51 575.25
III 112.90 150.05 251.57 331.50 753.30 1061.47 1158.72 1515.43 576.18 391.90 222.03 151.09
I 121.99 125.75 188.09 288.91 415.18 956.08 1358.86 1397.83 1265.46 1035.85 323.94 207.88
14 II 99.76 98.88 255.61 386.24 412.10 1631.64 1604.87 1482.32 920.77 527.39 277.25 231.99 663.64
III 94.73 125.37 219.17 329.30 404.27 2181.95 1964.34 1401.77 845.52 309.53 199.18 201.41
I 210.35 236.51 209.85 214.46 466.98 297.26 1860.31 1527.56 658.93 573.22 415.63 256.21
15 II 190.14 148.47 230.81 208.72 400.92 556.79 1741.17 1375.87 726.77 429.38 341.99 181.90 542.12
III 180.77 177.94 200.61 201.81 246.15 848.77 1528.09 1204.47 699.18 377.92 236.64 153.62
I 117.47 188.83 223.04 311.78 482.67 1204.14 735.13 1071.28 1328.94 818.54 365.63 170.31
16 II 128.96 184.16 175.15 258.66 359.49 837.76 610.21 1645.56 1039.54 502.10 328.78 138.87 557.43
III 141.70 198.72 170.73 397.23 486.32 844.98 681.05 1795.85 1375.16 355.72 249.45 143.40
I 111.12 125.52 150.71 431.57 481.88 278.69 604.36 1609.13 2128.58 747.97 382.35 159.82
17 II 88.18 139.01 167.62 363.44 377.16 357.21 1169.95 2136.21 1505.91 816.03 230.01 134.54 640.45
III 98.15 139.40 239.24 468.54 287.63 533.28 1455.66 2553.31 1645.83 641.23 158.32 138.56
I 138.40 153.22 223.41 240.33 361.31 255.64 758.70 893.53 851.25 872.34 311.66 203.06
18 II 140.98 110.31 185.10 228.51 265.86 335.18 1443.27 826.05 785.61 873.44 196.70 180.36 447.44
III 133.66 163.43 161.26 339.18 217.41 645.63 1298.88 835.94 617.55 521.22 170.11 169.23
I 143.47 179.63 183.68 377.92 598.44 1165.66 2130.98 1071.87 1379.56 662.53 304.01 221.42
19 II 144.48 194.69 243.21 519.25 791.05 1784.94 2581.77 1198.68 1120.24 664.02 183.26 158.83 789.71
III 134.09 205.76 307.92 375.48 587.80 1809.34 3398.86 1927.90 752.90 607.50 181.22 137.17
I 125.59 91.95 112.37 195.30 378.76 603.21 1619.12 1182.85 1156.89 485.50 236.36 144.43
20 II 103.18 91.74 132.59 201.71 378.87 1112.78 2207.89 1459.76 1396.46 518.88 149.31 129.07 605.06
III 98.34 117.33 148.04 290.76 488.17 1113.56 2788.79 1129.60 774.37 328.84 165.53 124.32
I 135.90 146.65 182.41 283.69 473.42 713.05 1360.82 1228.92 1183.22 856.66 325.72 185.83
AVG II 129.29 137.45 196.60 310.83 495.88 975.40 1585.06 1391.54 1144.89 681.38 263.35 164.27 614.58
III 128.72 152.04 202.34 349.49 524.57 1189.51 1725.35 1444.37 1046.26 450.85 210.61 148.68
Note : All Discharges are in cumec.
200

NALO H.E. PROJECT
SYNTHETIC AVERAGE 10-DAILY DISCHARGE SERIES AT DAM SITE
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
I 64.86 80.93 108.05 161.31 236.95 492.85 642.67 990.15 574.95 252.41 154.91 80.10
1 II 72.18 90.15 132.36 143.63 159.24 857.14 1008.71 966.28 725.34 445.25 112.49 80.60
III 75.65 98.59 117.66 244.61 356.48 1305.27 875.61 624.84 437.75 243.22 121.47 76.17
I 82.70 74.46 72.29 124.18 240.28 566.86 748.03 499.87 367.59 270.35 223.85 101.96
2 II 65.82 83.84 81.32 160.16 384.61 725.43 752.87 547.46 617.64 259.30 189.75 81.21
III 67.86 79.53 73.22 193.61 298.90 873.72 610.58 629.23 536.53 236.40 109.54 66.44
I 70.04 70.85 95.63 191.30 189.64 272.94 535.77 470.11 1423.58 589.21 178.19 121.31
3 II 76.92 80.74 114.89 153.45 241.77 434.70 525.04 489.65 1283.45 404.75 107.63 102.45
III 68.77 71.29 133.29 186.08 180.15 456.62 417.68 901.83 983.64 292.90 120.06 87.51
I 82.87 71.97 86.05 161.66 352.33 268.21 801.11 781.31 365.24 291.62 129.01 78.94
4 II 79.61 69.74 114.73 229.57 412.33 505.02 1301.60 618.76 323.17 409.81 105.46 85.90
III 72.38 75.55 146.11 302.46 234.00 666.80 987.43 507.45 421.49 226.10 97.52 83.89
I 66.96 56.10 66.63 137.06 241.74 476.97 1086.80 720.45 477.05 627.37 153.15 108.24
5 II 53.32 50.95 68.28 163.26 298.49 746.53 974.83 632.06 398.80 625.45 122.11 78.99
III 50.25 69.87 75.84 174.99 537.33 844.43 779.52 766.95 445.86 304.32 104.60 82.62
I 69.84 87.71 120.95 170.96 189.24 209.23 538.75 697.44 554.09 563.08 204.63 81.17
6 II 73.13 90.16 116.03 164.60 265.90 228.85 431.36 774.60 427.67 510.19 118.95 83.11
III 73.57 94.86 94.94 144.14 170.64 283.63 674.55 708.83 347.33 263.75 103.08 68.69
I 51.41 75.43 83.16 115.96 311.29 295.88 580.81 329.93 299.74 382.66 147.70 141.82
7 II 61.40 70.05 76.01 149.15 285.81 347.09 836.73 421.36 365.63 201.23 161.80 96.78
III 68.10 66.06 72.53 184.79 325.53 495.99 1027.29 389.33 421.67 161.81 146.46 79.89
I 91.65 102.01 102.20 170.23 298.57 1127.03 1474.65 645.81 666.84 536.10 260.49 92.97
8 II 85.77 76.08 94.85 177.55 456.79 1408.97 1627.29 728.91 477.13 578.19 223.00 98.39
III 92.70 79.04 120.38 132.75 666.27 1263.24 2049.64 798.77 664.97 262.65 146.87 88.03
I 80.00 53.70 94.52 103.38 219.17 202.66 891.05 853.55 605.27 652.76 163.35 73.71
9 II 63.86 49.80 98.77 181.23 155.68 193.10 694.81 1090.48 545.42 279.04 170.88 76.61
III 60.14 51.94 86.50 194.81 248.61 311.32 995.86 807.46 589.60 290.91 106.57 63.55
I 50.86 61.23 123.68 122.78 192.94 143.23 607.68 393.01 384.55 505.86 116.17 82.45
10 II 47.68 77.47 97.55 146.29 142.68 297.93 468.63 603.00 716.92 269.43 135.75 67.08
III 50.06 74.76 99.21 148.80 165.53 368.86 746.06 537.79 900.82 157.76 95.93 60.27
I 46.10 62.73 83.06 114.92 298.78 255.80 413.38 532.10 907.31 665.92 171.35 90.09
11 II 45.22 49.15 118.52 115.16 361.63 290.04 713.66 582.10 993.40 252.64 146.90 105.53
III 47.07 77.24 110.02 141.68 342.53 269.85 521.46 960.57 795.28 237.27 133.23 93.17
201
Annexure-5.3
1-2

NALO H.E. PROJECT
SYNTHETIC AVERAGE 10-DAILY DISCHARGE SERIES AT DAM SITE
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
I 107.30 92.55 98.90 159.46 323.34 343.43 708.09 429.79 780.26 352.42 120.75 102.86
12 II 108.06 93.52 88.76 183.86 277.86 417.71 565.00 583.84 824.58 392.32 114.47 78.77
III 102.18 85.84 101.90 183.40 155.95 596.81 925.59 1032.75 608.04 198.59 93.82 70.09
I 53.02 70.94 101.03 161.94 201.00 327.54 489.73 955.77 405.31 570.93 166.01 78.68
13 II 53.42 52.82 131.10 156.26 192.93 308.80 768.24 1247.86 379.00 248.04 157.73 81.56
III 59.21 78.70 131.94 173.86 395.08 556.71 607.71 794.79 302.19 205.54 116.45 79.24
I 63.98 65.95 98.65 151.52 217.75 501.43 712.68 733.12 663.69 543.27 169.90 109.03
14 II 52.32 51.86 134.06 202.57 216.13 855.74 841.70 777.43 482.91 276.60 145.41 121.67
III 49.68 65.75 114.95 172.71 212.03 1144.36 1030.23 735.18 443.45 162.34 104.46 105.63
I 110.32 124.04 110.06 112.48 244.92 155.90 975.67 801.15 345.59 300.63 217.98 134.37
15 II 99.72 77.87 121.05 109.47 210.27 292.02 913.19 721.60 381.17 225.20 179.36 95.40
III 94.81 93.32 105.21 105.84 129.10 445.15 801.43 631.70 366.70 198.21 124.11 80.57
I 61.61 99.04 116.98 163.52 253.14 631.53 385.55 561.85 696.98 429.30 191.76 89.32
16 II 67.64 96.59 91.86 135.66 188.54 439.38 320.03 863.04 545.20 263.33 172.43 72.83
III 74.32 104.22 89.54 208.33 255.06 443.16 357.19 941.86 721.23 186.56 130.83 75.21
I 58.28 65.83 79.04 226.34 252.73 146.16 316.97 843.94 1116.37 392.29 200.53 83.82
17 II 46.25 72.91 87.91 190.61 197.81 187.34 613.60 1120.37 789.80 427.98 120.63 70.56
III 51.48 73.11 125.47 245.73 150.85 279.69 763.45 1339.13 863.18 336.30 83.03 72.67
I 72.59 80.36 117.17 126.05 189.50 134.07 397.91 468.63 446.45 457.51 163.46 106.50
18 II 73.94 57.85 97.08 119.85 139.43 175.79 756.95 433.24 412.03 458.09 103.16 94.59
III 70.10 85.71 84.58 177.89 114.02 338.61 681.22 438.42 323.88 273.36 89.22 88.76
I 75.25 94.21 96.33 198.21 313.86 611.35 1117.63 562.16 723.53 347.47 159.44 116.13
19 II 75.77 102.11 127.56 272.33 414.88 936.14 1354.05 628.67 587.53 348.26 96.11 83.30
III 70.33 107.91 161.49 196.93 308.28 948.94 1782.59 1011.12 394.87 318.61 95.04 71.94
I 65.87 48.22 58.93 102.43 198.65 316.36 849.17 620.37 606.75 254.63 123.96 75.75
20 II 54.11 48.11 69.54 105.79 198.70 583.62 1157.96 765.60 732.40 272.14 78.31 67.69
III 51.58 61.54 77.64 152.49 256.03 584.03 1462.63 592.44 406.13 172.47 86.81 65.20
I 71.28 76.91 95.67 148.78 248.29 373.97 713.71 644.53 620.56 449.29 170.83 97.46
AVG II 67.81 72.09 103.11 163.02 260.07 511.57 831.31 729.81 600.46 357.36 138.12 86.15
III 67.51 79.74 106.12 183.29 275.12 623.86 904.89 757.52 548.73 236.45 110.46 77.98
Note : All Discharges are in cumec.
202
Annexure-5.3
2-2

Reply to the Comments of CWC on Hydrology chapter
Vide letter No. 7/9/NHPC/HP&I/1014 dated 13.05.2004.
Nalo H.E.Project (4×90 MW)
Annexure-5.4
5-7
SL.NO HEADING CWC COMMENTS NHPC REPLY
1 Consistency of
data
2 Water availability
studies
The methodology and the
detailed analysis done to
generate the synthetic
series is not available in the
report.
1. The methodology and the
detailed analysis done to
generate the synthetic
series is not available in the
report. The series of Upper
Subansiri is not yet
approved
2. NHPC is observing the
discharge data at Menga
site since June 2000. An
inter comparison of
observed and generated
series at Menga site for
concurrent period can throw
light on acceptability of the
generated series.
3. Alternatively, available
observed discharge record
since 2000 may be used for
time series analysis for
generation of a series of
desired length and the
same series after transfer to
Nalo dam site can be used
for power potential studies.
20% reduction may be
applied to the series so
generated to account for
inaccuracies in discharge
observation for the purpose
of PFR
3 Design flood a) The design flood
computation done by NHPC
are too empirical to be
relied upon.
b) In the absence of short
interval concurrent rainfall
runoff data the design flood
Kindly refer feasibility
report of Upper Subansiri
project submitted by
NHPC.
1. Kindly refer water
availability study of
Hydrology Chapter of
Feasibility report of
Subansiri Upper Project,
submitted in August 2002,
to CEA/CWC and CEA has
accorded the commercial
viability of the same.
2. A plot between average 10daily
discharge based on
observed and generated
series is enclosed (page
no-209). The series
generated at Subansiri
Upper is a synthetic series
therefore inter comparison
of observed and generated
series at Menga site for
concurrent period is not
possible.
3. Since only 3 years data is
available and so it would not
be logical to generate series
based on such short-term
record. The flow series
generated in a synthetic
series based on available
data of the entire basin of
Subansiri, for methodology
refer F.R. of Upper
Subansiri Project.
It is worth mentioning here that
although deterministic
approach of design flood
computation has not been
used directly in the present
study for Nalo sub basin,
however, this approach has
207

4
Sedimentation
may be calculated using
relevant sub zonal report of
CWC superimposing PMP
values from IMD.
c) The results may be
incorporated in the
comparative study to adopt
a realistic value of design
flood.
1. The sedimentation rate for
the region is about 0.1765
Ham/sqkm/year as per
CWC publication named
Compendium on Silting of
Reservoirs in India. Hence it
would be prudent to re-look
to the sediment rate figures
to be adopted.
2. An approximate sediment
study may also be carried
out to decide the sill level of
outlet and live storage
available.
The hydrological studies for
the PFR may be revised
incorporating the above
observations.
5 General The agency taking detailed
investigations/DPR must
review the hydrological and
hydro-meteorological
network and the other
recommendations given in
the report in consultation
with HSO, CWC.
The possibility of making
the project multipurpose
may be studied in detail at
DPR stage.
Annexure-5.4
6-7
been used indirectly along with
Empirical method, as the
design flood at Subansiri
Upper dam site had been
computed by deterministic
approach only. The details of
design flood study may be
referred in feasibility report of
Subansiri Upper Project,
August 2002.
1. We are aware of the findings
of CWC studies published
in the Compendium on
silting of reservoirs in India.
As per that report, the
sediment rate varies from
0.05658 to 0.2785
Ham/Sq.km /year for Indus,
Ganga and Brahmaputra
basin. But the silt rate
adopted for this particular
project has been adopted
on the basis of observed
data at Chouldhowaghat in
Subansiri basin and is
more region specific than
that given in “Compendium
on silting of reservoirs in
India”.
2. Detailed reservoir
sedimentation study need
be done during feasibility
stage with more observed
data at the proposed site
using a suitable method.
Agreed, the observation
network and analysis needs to
be done at the time of DPR.
208

Annexure-6.1
4-5
Reply to the comments of CMDD Division, CWC vide letter
No.7/9/NHPC/2004/HPI/872 dated 21.04.2004
Nalo H.E.Project (4 x 90 MW).
Comments Reply
1. The report should indicate Various alternative locations of dam axis
alternate locations of dam axis as examined during PFR preparation have
examined during the preparation been indicated in para 6.1 of PFR. The
of PFR to bring out the merits &
demerits of each including that
finally adopted in PFR.
same have also been shown in Plate - 6.1.
2. As per clause no. 5.2 of IS :
12966 (Part-I)- 1992 inspection
galleries at higher levels above the
foundations gallery may be
provided. Also instrumentation
gallery may be incorporated in the
drawings. As per codal provision
one more foundation gallery
should be provided.
3. It should be mentioned in the
report that the PMF has been
vetted by Hydrology Directorate
(NE) of the Central Water
Commission.
4. Justification for assuming non
monsoon diversion discharge as
2600 cumecs should be provided.
5. The down stream slope of nonoverflow
section seems to be on
the higher side, which may be
Location and alignment of galleries are
finalized during detailed design.
However, as desired galleries have been
indicatively shown in cross section of
dam (Plate-6.5)
For reply to observations of Hydrology
(NE) Dte. of CWC regarding PMF,
Annexure - 5.4 may be referred.
No G&D data is available for river
Subansiri at proposed dam site. Based on
the hydrological studies as carried out for
Subansiri Upper HE Project located on
d/s, value of diversion flood has been
assumed (Refer para 6.2.1).
Keeping in view high value of seismic
coefficient being recommended for
adoption, a flatter d/s slope of NOF has

educed considering the stability
criteria. Moreover the down
stream profile of the overflow
section should be furnished.
6. The TRT outlet of Naba HE
project is at EL 770.00 m and the
MWL of Nalo HE Project has
been proposed at EL 770.00 m.
But at least a difference of 5.0 m
may be kept.
7. The overflow section through
low-level orifice, needs to be
revised.
8. In the layout drawing, the position
of spillway needs to be shifted
towards right side.
9. The Water head above the crest is
likely to generate a high exit
velocity of the bucket end.
However, in case of lean
discharge there is a likelihood of
scour of the portion immediately
below the bucket lip. A suitable
provision in the form of concrete
apron needs to be worked out.
Annexure-6.1
5-5
been adopted. The same needs to be
reviewed during DPR stage. Further,
downstream profile of the overflow
section shall be finalized at DPR stage.
It may be clarified that for Nalo HE
Project, FRL has already been proposed at
EL 765m i.e. 5m below the TRT outfall of
Naba HE Project. Further in PFR dam top
elevation has been specified as EL 770m
and not the MWL.
Reasons for CWC observations are not
clear.
Needful done.
Concrete apron is normally provided on
downstream below the bucket lip.
However, such detailing is done only
during detailed design. Needless to
mention that provision of d/s concrete
apron stands already made in BOQ.

Annexure-6.2
2-3
Reply to the comments of HCD (E&NE) Division, CWC vide letter
No.3/5/2000-HCD (E&NE)/875 dated 08.04.2004
Nalo H.E Project (4 x 90 MW)
Comments Reply
1. Documents furnished alongwith
CEA letter No.
7/9/NHPC/03/HPI/160-2 dated
29 th March 04 does not indicate
design discharge and as such it is
not possible to comment on the
sizing of different components.
2. Specific comments cannot be
made on the general layout of the
scheme due to non-availability of
the contours u/s of the intake and
further d/s of the powerhouse.
3. Provision/design of desilting
chamber needs to be reviewed with
the more observed data.
4. Sizing, shape, type & location of
surge shaft needs to be reviewed
with detailed transient studies.
NHPC has submitted complete draft PFR
and the same clearly indicates the design
discharge. It is understood that copy of
complete draft PFR was forwarded to CWC
by CEA for comments.
Contours of area about 600m u/s of
proposed intake and upto 800m d/s of
proposed power house stands already
included in the layout plan (Plate - 6.1)
In the absence of observed sediment data,
desilting chamber has been proposed in
order to provide adequate provision in cost
estimate. Requirement/provision of desilting
chamber needs to be reviewed based on
sedimentation studies at DPR stage.
As already indicated in para 6.3 of PFR,
transient analysis/studies needs to be carried
out during DPR stage. Based on transient
studies size, type and location of surge shaft
needs to be finalised.

5. Efficacy of silt flushing through
low level spillway on the live
storage and also at the power
intake vicinity needs to be
examined.
Annexure-6.2
3-3
It is a standard practice to undertake model
studies to check efficacy of spillway for silt
removal from reservoir and from the power
intake vicinity. However, such model
studies are taken up after detailed
topographical and geotechnical
investigations leading to firming up of
design at DPR stage.

Reply to the comments of SP&PA Division, CEA vide letter No.
7/9/NHPC/2004/HP&I/892 dt.22.4.2004.
Nalo H.E. Project (4×90 MW)
Comments Reply
A. Technical Aspects:
1. Location:
Nalo HE project is one of the new
schemes identified by CEA in Subansiri basin.
Nalo HEP, a run-of-river scheme is proposed
on Subansiri river (a major tributary of
Brahmaputra river), near Nalo village in Upper
Subansiri District of Arunachal Pradesh. The
Project is located in upper reaches of Subansiri
River around 1.6km upstream of confluence of
Ledi Ishi with Subansiri River. Dam site is
about 10km upstream of Nacho and Power
House is located on right bank of the river near
Jiba-Aying village about 5km downstream of
dam site. The project is located about 120km
upstream of Daporijo town.
Three schemes viz. Subansiri lower (2000
MW), Subansiri Middle (1600 MW) and
Subansiri Upper (2000 MW) have been
planned to harness power potential of river
Subansiri.
CEA has identified eight additional projects in
the Subansiri basin, which are Oju-I (700
MW), Oju-II (1000 MW), Niare (800 MW),
Naba (1000MW), Kurung-I & Kurung-II (330
MW), Heigo and Duimukh (90 MW). Kurung I
& II projects have been clubbed and named as
Kurung HE Project. Further, Heigo project has
It is a statement.
Annexure-7.2
5-9

een found to be located within submergence
of proposed Subansiri Middle Project. As such,
in lieu of these two projects (Kurung HEP and
Heigo HEP), two schemes namely Nalo (360
MW) & Dengser (552 MW) located in between
of Naba HE Project and Subansiri Upper
Project have been identified for preparation of
PFR.
2. Cost of the Project:
The project is estimated to cost Rs. 2903.76
crores including IDC of Rs. 310.51cr. at June
2003 price level. The levellised tariff of the
project at present day cost works out to be Rs.
2.99 per unit. However, levellised tariff at
present day cost without any free power to
home state works out to be Rs. 2.63 per unit.
3. Power house:
Nalo power house which would be a surface
power house envisages installation of 4 units of
90 MW each. Power is proposed to be
generated at 11 kV and stepped upto 400kV
through 13 nos. (including one spare), 34 MVA
single phase, 11/400 kV step up generator
transformer as given on page 63 and 92 of the
PFR. However, in the SLD, generation voltage
Annexure-7.2
6-9
It is a statement. However,
project cost is revised as Rs.
2922.14 Crores including IDC of
Rs. 312.48 Crores at June 2003
price level due to change in
certain parameters of the project.
Revised levellised tariff of the
project at present day cost works
out to be Rs. 3.01 per unit.
However, levellised tariff at
present day cost without free
power to home state is Rs. 2.65
per unit.
Generation voltage shown as
13.8 kV in SLD is a
typographical error. Generation
voltage is at 11kV only.
Accordingly, corrected SLD is
enclosed.

has been shown as 13.8 kV. This needs
clarification. The generator transformers will
be further connected to 400kV outdoor
conventional switchyard through overhead
conductor.
4. Power evacuation:
In order to evacuate 360 MW of power from
Nalo HEP, a 400kV D/C transmission line with
Quad Moose conductor, 70 km in length from
Nalo HEP to Daporijo pooling point is
proposed as stated on page 8 and 93 of the
PFR. This is not correct. Instead of Quad
Moose conductor, it is suggested to use Twin
Moose conductor as mentioned in plate 8.2 of
the PFR. Accordingly, provision of 2 Nos.
400 kV outgoing bays has been kept in the
switchyard for 360 MW power evacuation
from this project. This is in order.
5. Daporijo Pooling Point:
It has been shown on plate 8.2 of the PFR that
the power from Oju-I (700 MW), Oju-II (1000
MW), Niare (800 MW), Naba (1000 MW),
Nalo (360 MW) and Dengser (552 MW) HE
Projects would be pooled at Daporijo pooling
point. Also, the power from Subansiri Upper
HEP – 2000 MW has been planned to be
pooled at Daporijo pooling point, from where
the total power (6412 MW) from 7 projects
would be ultimately transmitted directly
through HVDC link to the National Grid. This
is in order.
Annexure-7.2
7-9
The length of 400 kV D/C
transmission line with Twin
Moose Conductor from Nalo
HEP to Daporijo pooling point is
75 kms. The same has been
corrected as 75 kms instead of
70kms. Accordingly, the chapter
of power evacuation has been
revised.
It is a statement.

6. Switchyard
The switchyard of Nalo HEP would thus It is a statement.
comprise of the following bays as given in
plate 8.1. This is in order.
a) Generator transformer bays - 4 Nos.
b) 400 kV line bays - 2 Nos
c) 400 kV bus coupler - 1 Nos
Works covered at Daporijo pooling point
a) 400 kV line bays at Daporijo pooling point
7. Construction Power:
- 2 Nos.
Source of construction power for the project
has not been stated in the PFR. This may please
be furnished.
8. Cost of transmission works:
It has been stated on page 93 of the PFR that
the cost of 400kV D/C 70km. long
transmission line from Nalo HEP to Daporijo
pooling point and other end equipment at Nalo
pooling point has been considered. The cost of
transmission works has been given as Rs 62.31
crores under the abstract of cost of works on
page 118 and page 143 of the PFR. Details of
transmission works may be furnished. The
length of line has been given as 75 km on page
143 of PFR.
9. General Comments:
a) It may be stated that the benefits from these
projects may not be fully absorbed from NE
region and needs to be exported to other
Annexure-7.2
8-9
Requirements of construction
power for this project would be
met by suitable capacity of D.G.
Sets.
Cost for 75 km long transmission
line from Nalo HEP to Daporijo
pooling point has been
considered. The details of the
cost of transmission work will be
provided at FR/DPR stage.
Noted

egions. In long term perspective for
evacuating bulk power from we may need to
adopt a combination of HVDC/EHVAC
transmission system which requires least
transmission corridor, because of limited
corridor in the chicken –neck area taking into
account the various power projects likely to be
developed in NER in foreseeable future. We
may need to plan an integrated transmission
system from the pooling points in NER and
phase out the implementation schedule
suitably.
b) The transmission system as proposed for above
schemes is tentative. The final transmission
system would be determined by detailed power
system studies on the basis of total power to be
transmitted from NER, which may require a
change in the voltage levels or configuration of
the transmission system taking into
consideration the mountainous terrain, thick
forest area and right of way problems.
c) Beneficiaries States / Regions along with their
tentative shares from these projects have not
been identified so far.
B.Cost Aspects:
Comments on cost aspects shall be forwarded
in due course.
Noted
It is a statement.
Annexure-7.2
9-9
Comments on cost aspects have
been received vide letter
No.7/1/2004/SP&PA(C)/239
dated 13.05.2004. Replies are
appended as Annexure 7.3.

Annexure-7.3
3-4
Reply to the comments of SP&PA Division on Cost Aspects, CEA vide letter
No. 7/1//2004/SP&PA(C)/239 dated.13.05.2004
Nalo H.E. Project (4x90 MW)
Switchyard Cost Estimates:
Comments Reply
1. As per single line diagram power from
Nalo HE Project ( 4×90 MW) would be
stepped up to 400 kV and evacuated
over 2 no 400kV lines to Daporijo.
Accordingly, provision for 7 bays has
been made in the switchyard (4GT bays
+2 line bay +1BC)
2. The average basic equipment cost of
400 kV bay for open switchyard in
double main bus arrangement has been
estimated at the rate of Rs. 2.50 crores
per bay. Over and above this ED @
16%, CST @ 4%, Spares @ 2 %,
Transportation & Insurance @ 6%,
Erection and Commissioning @ 8% has
been taken. This is generally in order.
3. Establishment and Contingency has
been taken as 8%. This is in order.
4. Detailed break up of switchyard
equipment cost has not been included
in the PFR. It may be noted that
detailed break up of cost for switchyard
equipment and works need to be
included at the time of preparation of
feasibility report.
Transmission line Cost:
1. The cost of 400kV D/C transmission
line with twin moose conductor has
been taken as Rs. 50 lakhs/Km. Over
and above this cost ED @ 16%, CST @
4%, Transportation and Insurance @
6%, Erection and Commissioning @
8% has been taken. For a hilly terrain
It is a statement.
It is a statement.
It is a statement.
It is a statement. However, the detail breakup
of cost for the switchyard equipment
will be provided at the DPR stage.
It is statement. However, the detail break-
up of cost for the 400kV transmission line
components will be provided at the DPR
stage.

of Arunachal Pradesh these estimates
are on lower side. An estimate of Rs.
60 lakh per km for 400kV D/C line
may be taken against Rs. 50 lakh per
km taken in the PFR. Detailed break up
of transmission line cost alongwith
details of tower, conductor and
insulators etc needs to be included at
the time of preparation of feasibility
report.
2. The rate for 400 kV D/C line bay at the
terminating station has been taken as
Rs. 2.5 lakhs per bay. Over and above
this ED @ 16% , CST @ 4%, Spares @
2%, Transportation & Insurance @ 6%
Erection and Commissioning @ 8% has
been taken. This is generally in order.
However, detailed breakup of cost
needs to be included at the time of
preparation of feasibility report.
Annexure-7.3
4-4
It is a statement. However, the detail breakup
of cost for 400kV line layout at
terminating station will be provided at the
DPR stage.

Annexure-9.1
Final Report
Satellite Remote Sensing Based Inputs for Initial
Environmental Study in respect of 10 Proposed Hydro-Power
Sites in Subansiri Basin in Arunachal Pradesh
Name of the Hydro-Power Site : NALO
Prepared for
National Hydroelectric Power Corporation Ltd.
Subansiri Basin Projects
Hapoli (Ziro)
Arunachal Pradesh – 791 120
Water Resource Division
Water Resource & Oceanography Group
Remote Sensing & GIS Applications Area
National Remote Sensing Agency
Dept. of Space, Govt. of India
Balanagar, Hyderabad- 500037
April, 2004

1. Study Background
2. Objective
CONTENTS
3. Salient Features of the Nalo Hydro-Power Site
4. Satellite data Used
5. Brief Methodology of Satellite Data Analysis
6. Outputs provided
7. Critical Analysis of Satellite based Initial Environmental Study
8. Conclusion & Recommendation
List of Maps
1.a. IRS 1C PAN + LISS III merged satellite image of 26th December
2002
1.b. Satellite derived landuse-land cover map of surroundings of
proposed hydro power site at Nalo, Arunachal Pradesh
1.c. Landuse-Landcover map of immediate surroundings upstream
of proposed Dam site at Nalo.
1.d. Map of National Parks/ Sanctuaries and the location of Nalo
hydro power site and 7 Km radius circle from the dam site
List of Tables
Table 1. Land use – land cover Information within the Submergence
Area
Table 2. Landuse-landcover Information within the 7 Km radius from
the dam site at Nalo
234

Satellite Remote Sensing Based Inputs for Initial environmental study in respect of 8 Proposed Hydro-Power Sites in Arunachal Pradesh –
Nalo Hydro-power Site
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
1. Study Background
Annexure-9.1
Central Electricity Authority (CEA) under Ministry of Power, Govt. of India
has earlier identified 399 potential hydroelectric sites in the country with an
installed capacity of 1,07,000 Megawatt (MW). With a view to preparing an
action plan to develop this hydroelectric potential and prioritizing the
implementation of hydro-electric projects, a Ranking Study was taken up by the
CEA in 2001. This Ranking Study identified 162 most potential sites with a total
installed capacity of 50,560 MW for development.
Preparation of Pre-Feasibility Reports (PFR) of these 162 sites has been
initiated by the CEA in 2002 with works entrusted to a number of Consultants,
namely, National Hydroelectric Power Corporation (NHPC), North Eastern
Electric Power Corporation (NEEPCO), Water And Power Consultancy Services
India Limited (WAPCOS), Satluj Jal Vidut Nigam Limited ( SVJNL) , Himachal
Pradesh State Electricity Board ( HPSEB), Uttaranchal Jal Vidut Nigam Limited (
UJVNL) and Kerala Power Corporation Limited ( KPCL) with time target of
completion of the whole exercise by September 2003. To oversee the progress
of the PFRs preparation in time and with full cooperation of the Central
Government agencies, a Central Coordination Committee consisting of Central
Electricity Authority (CEA), Central Water Commission (CWC), India
Meteorological Department (IMD), Ministry of Environment & Forest, Survey of
India, Geological Survey of India (GSI) and National Remote Sensing Agency
(NRSA) was constituted by the CEA with Member (Hydro-power) as its
Chairman. The Committee is sitting periodically in presence of the
representatives of the Consultants to take stock of the completion of the studies.
One of the mandates of PFR preparation is “Initial Environmental Study” with
respect to each of the 162 proposed sites using satellite remote sensing data.
------------------------------------------------------------------------------------------------------------------
Prepared for National Hydroelectric Power Corporation Ltd , Regional Office at Hapoli (Ziro)
by National Remote Sensing Agency (NRSA), Dept of Space, Govt. of India, Hyderabad
235

Annexure-9.1
Satellite Remote Sensing Based Inputs for Initial environmental study in respect of 8 Proposed Hydro-Power Sites in Arunachal Pradesh –
Nalo Hydro-power Site
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
As is well known in India and elsewhere in the world, space technology
plays a very important role in terrain mapping and scientific assessment of the
ground condition at speed, and is ideally suitable for inaccessible mountainous
regions where majority of these hydroelectric dam/diversion sites are located.
Computer processing of satellite digital data of the dam / diversion sites and their
immediate environ provides wealth of information for preparation of the Pre-
Feasibility Reports. The Potential of this technology was amply demonstrated in
the preliminary ranking study of the 81 proposed hydro-electric sites in Indus
Basin completed by NRSA in October 2001 on behalf of CEA. In view of this,
NRSA has been approached by a number of consultants, namely, NHPC and
HPSEB to take up Initial Environmental Studies in respect of 42 proposed hydro-
power sites located in the States of Arunachal Pradesh, Himachal Pradesh,
Jammu & Kashmir and Madhya Pradesh using most recent satellite remote
sensing data.
Regional Office of NHPC, Subansiri projects at Hapoli ( Ziro) with
responsibility of survey and investigation in Subansiri river basin in Arunachal
Pradesh, has approached NRSA for satellite remote sensing based inputs for
initial environmental study of 10 hydro-power sites located in Subansiri Basin.
This Report deals with Nalo hydro-power site.
2. Objective
Principal objective of the satellite based study is to acquire Indian Remote
Sensing satellites (IRS 1C/1D) LISS-III and PAN sensor digital data of the hydro-
power sites and to make quick analysis of these data in terms of estimation of the
submergence area at proposed Full Reservoir Level (FRL) and mapping of land
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use - land cover information within and in immediate surrounding of the proposed
submergence area as inputs for Initial Environmental Study (IES) of the Pre-
Feasibility Report.
The specific objectives and scope of the study are:
• To estimate the area of submergence at proposed FRL of the proposed
hydro-power sites
• To analyse the satellite data for identifying broad landuse – land cover
categories like agricultural land, forest land, barren land, scrub land, water
bodies, settlements, infrastructural features (roads and bridges) and to
estimate the area under each of the categories within and in immediate
surrounding of the proposed submergence area at FRL.
• To prepare land use - land cover map at 1:50,000 scale and/or 1:25,000 scale
of the submergence area and its immediate surrounding for each hydro-
power site.
3. Salient Features of the Nalo Hydro-Power Site
Proposed hydro-power site is located at Nalo in Subansiri Basin in
Arunachal Pradesh falling in Survey of India topo sheet No.82 H/15. The proposed
project scheme at Nalo envisages construction of a Dam on on Subansiri river,
and a power house with a installed capacity of 360MW. FRL is proposed to be 765
metre above MSL. The Head-Race Tunnel from the dam to the power house is
proposed to be 3.75 km in length. The river water will be stored in the reservoir
which will be diverted through the Head-Race Tunnel to the Power House for
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Nalo Hydro-power Site
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hydro-power generation and subsequent power evacuation to areas in Arunachal
Pradesh and other areas
The geographic location of Dam and Power House for this hydro-power site is
given below :
Dam Power House
Latitude : 28° 24’ 26.68” N 28° 24’ 29.63” N
Longitude: 93° 46’ 53.71” E 93° 48’ 42.98” E
4. Satellite data Used
Indian Remote Sensing Satellite, IRS-IC LISS III and PAN sensors data of
26 th December, 2002 covering the study site were procured from the NRSA Data
Centre (NDC) after intensive browsing of the available satellite data for cloud-free
and radiometric suitability. IRS-1C covers the study site by satellite geo-
reference number Path 112 and Row 51. These data are geometrically and
radiometrically corrected digital data products which can be used readily in
Window based image analysis platform.
5. Brief Methodology of Satellite Data Analysis
Image processing and analysis was done using ERDAS Imagine image
analysis software in Windows platform. Satellite data of IRS 1C LISS III sensor
provides 23.5 m spatial resolution and PAN sensor provides 5.8m spatial
resolution. The two sensor data were geocoded and digitally merged using IHS
transformation technique . Baseline information layers (like rivers/ streams) and
infrastructural features (like roads and bridges), settlements / villages were
initially interpreted on the digital image scene. Subsequently, image
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Nalo Hydro-power Site
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classification technique was performed to obtain the land use-land cover
categories of the study area.
Output maps were composed in the image processing system which
provide the landuse / land cover information along with other interpreted
information such as roads, settlements etc., within the 7 Km radius from the dam
site. The Full Reservoir Level (FRL) boundary, provided by the NHPC, Regional
Office at Hapoli, was superimposed on the satellite data as well as on the land
use - land cover map. Area statistics of different landuse-landcover categories
were generated within the submergence area at FRL and within the 7 km radius
circle from the dam site.
6. Outputs provided
Based on the analysis of satellite data and other available ancillary
information, the following outputs were generated :
• Map 1 (a) Shows IRS 1 C PAN + LISS III merged satellite image of 26 th
December, 2002on 1:50,000 scale covering 7 km radius from
the dam site overlaid with FRL , location of dam site and
power house.
• Map 1(b) Shows satellite derived landuse-landcover map on 1:50,000
scale covering 7 km radius from the dam site overlaid with
FRL , location of dam site and power house. Land use /land
cover map shows the following categories : Forest (High and
Medium Dense Forest), Agricultural Land, Open Scrub,
Barren and Rock Outcrop, Snow, River Course/ Dry River
Bed.
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• Map 1(c) Shows the landuse- landcover classes and their corresponding
area statistics in hectares within the submergence area on
1:25000 scale overlaid with FRL , location of dam site and
power house.
• Map 1 (d) Shows the location of the National parks / Wildlife Sanctuaries
vis-à-vis the location of the dam/ Power House and 7 km
radius area around the dam site.
• Table.1 Landuse-landcover Information within the Submergence Area
S.No Landuse-landcover
Category
Area under
submergence (Ha)
% of the total
submergence area
1 High Dense Forest 118.36 41.71
2. Medium Dense Forest 27.49 9.69
3. Low Dense Forest Nil Nil
4. Open Scrub 56.78 20.01
5. Barren / Rock Outcrop 4.10 1.44
6. Snow Nil Nil
7. Agricultural Land 1.14 0.40
8. Human Settlement 0.49 0.17
9. River Course including
dry river bed
75.44 26.58
Total 283.80 100.00
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• Table.2 Landuse-landcover Information within the 7 Km Radius from
the Dam site at Nalo
S.No Landuse-landcover
Category
Total Area ( ha)
% of the total
area
1 High Dense Forest 12523.73 81.35
2. Medium Dense Forest 1585.85 10.30
3. Low Dense Forest Nil Nil
4. Open Scrub 980.42 6.37
5. Barren / Rock Outcrop 80.17 0.52
6. Snow 7.24 0.05
7. Agricultural Land 33.39 0.22
8. Human Settlement 13.46 0.09
9. River Course including
dry river bed
169.74
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Total area 15394.00 100.00
7. Critical Analysis of Satellite based Initial Environmental Study
• Total area under submergence at proposed FRL of 765 m. (above MSL) is
estimated to be 283.80 ha ( Table.1).
• It is observed that vegetation cover is mostly dominated by forest category
which is 146 ha ( 51% of the submergence area ). Entire forest vegetation is
classified as high and medium dense forest in the submergence area.
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• Submergence of forest vegetation ( High dense and Medium dense) may be
of some immediate concern which needs to be rehabilitated with alternate
afforestation measures within the vicinity of the dam site when the project
scheme is taken up for implementation.
• There is very little 1.14 ha. Of (Insignificant) agricultural area present within
the proposed submergence area which is positive sign to develop the
proposed hydropower site.
• Open scrub land is the next dominant land use – land cover category after the
forest and constitutes 20% of the submergence area. This is followed by
Barren / Rock outcrop land which is 1.44%.
• There are no surface water bodies other than the river course. The area under
river course including dry river bed is estimated to be 75.44 ha., which
constitutes 27% of the total submergence area.
• It is also observed that the submergence area at EL + 765 m. above MSL
(FRL) is likely to affect (Inundate) few isolated settlements. Hence, a close
look at the ground is required to assess the exact impact.
• In the absence of available information from other sources about the
existence and spatial extent of national parks and wildlife sanctuaries, best
efforts were made to collect information from the Internet. The information
available in website of United Nations Environment programme World
Conservation Monitoring Center (http://www.unep-wcmc.org), National
Informatics Centre, www.wildarunachal.org and www.arunachalbhawan.com
regarding Arunachal Pradesh State and its National Parks / Wild
Sanctuaries, were browsed through. The information at hand is made use in
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Nalo Hydro-power Site
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preparing map 1(d) which depicts the latitude and longitude of dam site and
the sanctuaries/national parks. 7 km radius circle around the dam is plotted
and the radial distance to the various national park/ sanctuary were estimated
around the nearest national park/ sanctuary which are of significant only are
measured on the map 1(d). The following points are observed from the map
1(d).
- The nearest National park is Mouling which is about 93 Km from the dam
site. The nearest sanctuaries are Kane, Itanagar, Pakhui and D’Ering
memorial which are about at distance of 115 Km, 145 km, 156 km and
169 Km . So it is observed that the dam site is more than 93 Km away from
the National park and sanctuaries. Hence, proposed development of the
site is least likely to have impact on them.
- Since 7 Km radius around the dam site was considered as the area of
study, efforts were made to check whether the geo-coordinates of this
Wildlife Sanctuary is falling within the area of study. The map No. 1(d)
explains the location of the sanctuary vis-à-vis the dam site and the power
house.
8. Conclusion & Recommendation
1. Satellite based study has provided insight into the landuse-landcover
pattern and their spatial extent within the submergence area at FRL and
within the 7 Km radius vicinity of the proposed dam site. Such detail
information on a scale of 1:25,000 are not available from any other sources
at present.
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2. There is practically no agricultural land ( 1.14 ha., very insignificant) within
the submergence area. The environmental cost on this score is therefore
nil.
3. Few isolated settlements are likely to be affected by the submergence area
at the proposed FRL. This has to be verified on the ground for detailed
information.
4. The proposed dam site and the power house locale is endowed with rich
forest vegetation. However, since the submergence area at FRL is
confined within the river gorge, forest vegetation of the spatial extent of
146 hectares will be affected due to submergence. Species types of
these forest vegetation need to be identified from local Forest Department
and by field visit to the area. These forest vegetation needs to be
rehabilitated with alternate afforestation measures. Within the vicinity of
the hydro-electric project. Alternate lands in the form of open scrub
(980 ha) is available within the 7 Km radius of the dam site for
rehabilitation of this forest vegetation loss in the submergence area.
5. Mouling Natinal park is at a radial distance of 93 Km from the proposed
dam site, and Kane, Itanagar, Pakhui and D’Ering memorial Sancturies
are at a distance of 115 km, 145 km, 156 km and 169 km respectively
away from the dam site according to the information collected from several
websites. The location and wildlife of this sanctuary will in no way be
affected by the hydro-electric project, since the fetch distance of the
reservoir submergence will be around 10 Km .
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