Feasibility Study Report_Main Report_Teliya

Teliya Khola Small Hydropower Project, Teliya and Parewadin VDC, Dhankuta Feasibility Study Report

FEASIBILITY STUDY REPORT OF

TELIYA KHOLA SMALL HYDROPOWER PROJECT

TELIYA &PAREWADIN VDC (DHANKUTA) & HAMARJUNG VDC (TERHATHUM)

(996 KW)

Prepared by : Epsom Engineering Consultancy Pvt. Ltd.

& Modern Hydropower and Energy Development Pvt. Ltd. JV

GPO Box No: 8973, NPC -585 New Baneshwor, Kathmandu, Nepal

Tel: 015546792 / 9851070202 E-mail: [email protected]

Submitted by :

Volcano Hydropower Pvt. Ltd. Kathmandu Metropolitan City: Ward No: 09

Gairigaun, Kathmandu Tel: 98421-56928

E-mail: [email protected]

September 2010

VOLUME 1 : MAIN REPORT


Salient Features

General Name of the Project: Teliya Khola Small Hydropower Project Name of the River: Teliya Khola Type of scheme Run of River Project location Teliya and Parewadin VDC of Dhankuta district and Hamarjung VDC of Terhathum district. Zone Koshi Development Region Eastern Latitude 8725'23" E to 8726'36" E Longitude 2700'00" N to 2702'40" N

Access Dhankuta-Jorpati 25 km Jorpati-Teliya 7 km (Earthen Road) Teliya-Project Site 3 kM

Hydrology Catchment Area 38 km2 Long term average flow 1.116 m3/s Minimum monthly flow 0.161 m3/s Design discharge (Q40) 0.85 m3/s Design flood at intake (1:20) 138.00 m3/s Design flood (1:100) 215.00 m3/s

Headworks Weir Type Concrete gravity type Length 30 m Crest Elevation of weir 763.00 m

Intake Type Orifice Type No. of Opening 1 Gallery width and depth 1.2 m x 1 m Design discharge 0.98 m3/s

Approach canal


Type Rectangular Length 16 m Size (Width and Depth) 2 m x 2 m Flow level at u/s 763.00 m Design discharge 0.978 m3/s

Desander Type Single Chambered No of units One Length 16.0 m Size (Width and Depth) 3.8 m x 3.9 m Design discharge 0.978 m3/s Transition length (inlet / outlet) 4.5 m / 3.25 m Particle size to be settled > 0.20 mm

Headrace Canal Type Rectangular lined stone masonry Length 1616 m including 25 m RCC crossing Size (Width x Depth) 1200 mm x 1000 mm Design discharge 0.935 m3/s Special Feature 25 m RCC Crossing (55 m-80 m)

Forebay Size 18 m x 3.5 m x 3.2 m FSL at forebay 760.00 m

Penstock Type Surface type, Steel Length 266 m Internal diameter 750 mm Thickness 5 to 8 mm Design discharge 0.85 m3/s Penstock bifurcation diameter 530 mm

Powerhouse Type Surface Size 18.40 m x 10.22 m Power house floor level 620.71 m FSL in tailrace at powerhouse 618.50 m

Turbine Type Pelton Turbine


Number of units 2 nos Turbine axis level 620.00 m Turbine rated capacity 2 x 0.498 MW Rated net head 138.94 m Rated turbine efficiency 91 %

Tailrace Canal Type Rectangular Size 1.5 m x 2.0 m Length 60 m Invert level of tailrace at powerhouse 620.00 m

Transmission line Transmission voltage 11 kV Line length 3.0 km Connection point Parewadin VDC, Dhankuta district

Transformer Number of unit 1 Rating 1250 kVA Type 3-phase, oil immersed Type of cooling ONAN Number of phase 3 Frequency 50 Hz Rated voltage Primary (l.V. side) 6.3 kV Secondary (H.V. side) 11 kV Vector group symbol as per IEC 60076 YND11 Tap changer off load at high voltage winding, + 5% in steps of + 2.5% X 4 Percentage impedance at rated MVA base 5%

Generator No. of units Two (2) Type 3-phase, synchronous, vertical shaft Rated Power 620 kVA Rated Voltage 6.3 kV Rated Frequency 50 Hz


Rated Power factor 0.8 (lagging) Rated Speed 750 rpm Rated Efficiency 96 % Stator and Rotor insulation class F Stator connection star with neutral earthed Direction of Rotation clock wise as viewed from the top at the unit Short Circuit Ratio not less than 1.1 Excitation system brushless

Power and Energy Installed Capacity 996 kW Dry Season Energy 1.02 GWh/year Wet Season Energy 4.338 GWh/year Total Energy 5.359 GWh/year

Construction Period 24 months

Economic and Financial Indicators Project cost NRs. 160.238 Million Cost per kW US$. 2145.00 Net present value (at 10% discount rate) NRs. 54.76 Million Internal rate of return (IRR) 14.26 % Debt equity ratio 75:25 Interest rate on loan 10 % Loan repayment period 10 Years


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TABLE OF CONTENTS Page No.

TABLE OF CONTENTS T-i LIST OF FIGS L-i

1. INTRODUCTION 1 1.1 BACKGROUND 1

1.2 APPROACH METHODOLOGY 1

1.3 PREVIOUS STUDIES 2

1.4 OBJECTIVES OF THE STUDY 2

2. DESCRIPTION OF THE PROJECT AREA 3 2.1 LOCATION 3

2.2 PHYSICAL FEATURES 3

2.3 ACCESSIBILITY 3

3. FIELD INVESTIGATION AND DATA COLLECTION 5 3.1 TOPOGRAPHICAL SURVEY 5

3.2 COLLECTION OF AVAILABLE HYDROLOGICAL DATA 5

3.3 STREAM FLOW DATA 5

3.4 SEDIMENTATION DATA 5

3.5 GEOLOGICAL INVESTIGATION 6

4. HYDROLOGICAL STUDIES 7 4.1 CATCHMENT CHARACTERISTICS 7

4.2 DRY FLOW MEASURMENT 8

4.3 REFERENCE HYDROLOGY AND STREAM FLOW DATA 8 4.3.1 Stream Gauging 8 4.3.2 Mean Monthly Flow 8 4.3.3 Adoption of Design Discharge 9

4.4 FLOW DURATION CURVE 10

4.5 FLOOD HYDROLOGY 12 4.5.1 Design High Floods 12 4.5.2 Low Flow Analysis 13

4.6 COMPENSATION FLOW 13

4.7 CONCLUSIONS AND RECOMMENDATIONS 13 4.7.1 Conclusions 13 4.7.2 Recommendations 13

5. SEDIMENTATION STUDY 14 5.1 SEDIMENTOLOGY 14


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5.1.1 Himalayan Sediment Yield Technique 14 5.1.2 Regional Studies 15

5.2 CONCLUSION AND RECOMMENDATION 15

6. GEOLOGICAL STUDIES 16 6.1 REGIONAL GEOLOGY 16

6.2 GEOLOGY OF PROJECT AREA 17 6.2.1 Lithology 17 6.2.2.1 Headworks Area 20 6.2.2.2 Desanding Basin Area 20 6.2.1.1 Fore Bay 21 6.2.2.3 Penstock Alignment 22 6.2.2.4 Powerhouse Site 22

6.3 SEISMICITY 23

6.4 CONCLUSIONS AND RECOMMENDATIONS 24

7. STUDY OF ALTERNATIVE LAYOUT 25 7.1 HYDROPOWER PROJECT ALTERNATIVES 25

8. PROJECT OPTIMIZATION 26

9. PROJECT DESCRIPTION AND DESIGN 35 9.1 GENERAL 35

9.2 SITE CONDITION AND PROJECT SETTINGS 35

9.3 DESCRIPTION OF PROJECT CIVIL COMPONENTS 35 9.3.1 Headworks 35 9.3.2 River Diversion 36 9.3.3 Overflow Weir 36 9.3.4 Intake 36 9.3.5 Gravel Trap cum Desander 36 9.3.6 Headrace Canal 37 9.3.7 Forebay 37 9.3.8 Penstock, Anchor Block and Saddle Support 38 9.3.9 Powerhouse Complex 38

9.4 POWER FACILITIES: MECHANICAL EQUIPMENT 39 9.4.1 Introduction 39 9.4.2 General Design Criteria 39 9.4.3 Cooling Water and Service Water System 43 9.4.4 Drainage and Dewatering System 43 9.4.5 Compressed Air System 43 9.4.6 Oil Handling System 44 9.4.7 Ventilation and Air Conditioning System 44 9.4.8 Powerhouse Crane 45 9.4.9 Mechanical Workshop 45 9.4.10 Fire protection system 45

9.5 POWER FACILITIES: ELECTRICAL EQUIPMENT 45

9.6 INTRODUCTION 46 9.6.1 Scope 46


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9.6.2 General Design Criteria 46 9.6.3 Standards and Regulations 46 9.6.4 Generators and ancillaries 47 9.6.5 Transformer 49 9.6.6 Station auxiliary systems 49 9.6.7 Protection systems 51 9.6.8 Control System 51 9.6.9 Communication systems 52 9.6.10 High Voltage Switchgears 52

9.7 PROJECT DESCRIPTION AND DESIGN OF MECHANICAL AND ELECTRICAL COMPONENTS 52 9.7.1 TRANSMISSION LINE 53 9.7.2 Transmission Line Requirements 53 9.7.3 11 kV Switchyard/ Interconnection point Arrangement 54 9.7.4 Construction power 54

10. POWER EVACUATION STUDY 56 10.1 INTRODUCTION 56

10.1.1 Existing or Under Construction Substations around the Project Area 56 10.1.2 Selection of Voltage Level and Conductor Size 57 10.1.3 Spread Sheet Calculation for Conductor Selection and Voltage 57 10.1.4 Power Evacuation Schemes 58 10.1.5 Economic Analysis, Comparative Study for selected options 59 10.1.6 7.0 Conclusion and Recommendation 61

11. ENERGY AND PROJECT REVENUE 62 11.1 GENERAL 62

11.2 POWER GENERATION 62

11.3 ENERGY GENERATION 63

11.4 REVENUE 63

12. CONSTRUCTION PLANNING 65 12.1 GENERAL 65

12.2 ACCESS AND INFRASTRUCTURE 65

12.3 ACTIVITIES ON THE CRITICAL PATH 65

12.4 CONSTRUCTION MATERIALS 65

12.5 DISPOSAL OF EXCAVATED MATERIALS 66

12.6 CONTRACT PACKAGE 66

12.7 CONSTRUCTION POWER 66

12.8 CONSTRUCTION SCHEDULE 67

13. COST ESTIMATES 68 13.1 INTRODUCTION 68

13.2 CRITERIA, ASSUMPTIONS AND COMPONENTS 68

13.3 ESTIMATING METHODOLOGY 68


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13.4 ESTIMATING METHODOLOGY 69

13.5 ELECTRO MECHANICAL EQUIPMENTS 70

13.6 TRANSMISSION LINE AND SWITCHYARD 70

13.7 SITE FACILITIES, ACCESS ROAD AND ENVIRONMENTAL PROVISIONS 70

13.8 OTHERS 70

13.9 PROJECT COST 71

14. FINANCIAL ANALYSIS 72 14.1 INTRODUCTION 72

14.2 CRITERIA AND ASSUMPTIONS 72 14.2.1 Project Financial Cost 72 14.2.2 Project Financial Benefits 72 14.2.3 Discount Rate 72 14.2.4 Cost Datum 72 14.2.5 Planning Horizon 73 14.2.6 Currency Exchange Rate 73 14.2.7 Operation and Maintenance Cost 73 14.2.8 Taxes, Duties and VAT 73 14.2.9 Royalties 73 14.2.10 Debt Equity 73 14.2.11 Interest Rate 74 14.2.12 Loan repayment Period 74 14.2.13 Financing Structure 74

14.3 SENSITIVITY ANALYSIS 75

14.4 CONCLUSION AND RECOMMENDATION 77

CONCLUSION AND RECOMMENDATIOIN 78 14.5 CONCLUSION 78

14.6 RECOMMENDATION 78

14.2.1 GENERAL 78

14.2.2 DETAILED DESIGN 78 LIST OF REFERENCE

ANNEX A : COST ESTIMATE ANNEX B : CONSTRUCTION SCHEDULE ANNEX C : ENERGY CALCULATION ANNEX D : FINANCIAL ANALYSIS ANNEX E : DESIGN CALCULATIONS ANNEX F : POWER EVACUATION ANNEX G : SITE PHOTOGRAPHS


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LIST OF FIG

Page

Fig. 2.1 Project Location 4

Fig. 4.1 Catchments area of Teliya Khola at Proposed headworks sites 7

Fig. 4.2 Long- Term annual hydrograph of Teliya Khola by Various Methods 10

Fig. 4.3 Flow Duration Curves at headworks sites of Teliya Khola 11

Figure 6.1: Geological Map of Nepal Himalaya (After Dahal, R.K., Hasegawa, S., 20081 16

Fig. 6.2 Geological Map of Project Area 17

Fig 6.3: Triangulated Irregular Network of the project Site on the basis of Counter height 18

Fig 6.4:Slope Map of the project area 18

Fig 6.5.:Aspect Map of the project area 19

Fig 6.6:Landuse Map of the Project area 19

Fig 6.7 : Intake area 20

Fig 6.8.: Test Pit in Desanding Area 21

Fig 6.9: Location of Forebay showing pit during field survey 21

Fig 6.10: Penstock Alignment 22

Fig 6.11: Pit in Powerhouse Area 22

Fig 6.12: Simplified seismic risk map of Nepal after Bajracharya 1994 24

Fig 8.1: Variation of Specific Energy Cost with Installed Capacity 31

Fig 8.2: Variation of EIRR with Installed Capacity 32

Fig 8.4: Variation of Net Present Value with Installed Capacity 33

Fig 8.4: Variation of Net Present Value with Installed Capacity 33

Fig 9.1: Turbine selection 39

Fig 10.1 : Capital Cost versus different Schemes 60


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Fig 10.2 : Annual loss versus different Schemes 60

Fig 10.3 : Total Annuity versus different Schemes 61

Fig 11.1 Monthly variation of power generated 62

Fig 11.2: Monthly and average revenue generation 64

Fig .13.1 Variation of Net Present value for different alternatives 76

Fig. 13.2 Variation of Internal Rate of Return for different alternatives 77

Fig. 13.3 Variation of Benefit Cost Ratio for different alternatives 78


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LIST OF TABLES Page

Table 2.1: Geographical coordinates of the project 03

Table 4.1: Dry flow measurement of Teliya Khola 08

Table 4.2 Mean Monthly Discharge (m3/Sec) by MIP Method 9

Table 4.3 Mean Monthly Discharge (m3/Sec) by WECS/DHM Method 9

Table 4.4 Comparison of Long-Term mean Monthly Discharges 9

Table 45 Probability of exceedence and Discharges 11

Table 4.6 Estimated high floods for Tame Khola 12

Table 4.7 Low flood Frequency Analysis 13

Table 6.1: Output of Pit Analysis (Desanding Basin) 20

Table 6.2: Output of Pit Analysis (Forebay) 21

Table 6.3: Output of Pit Analysis (Powerhouse) 23 Table 8.1 Range of Options 27

Table 8.2 Average Monthly Flows 28

Table 8.3 Energy and Revenue Calculation 29

Table 8.4 Summary of Project Cost 29

Table 8.5 Result of Economic Analysis 31

Table 9.1 : Description of penstock thickness, length and weight 38 Table 9.2 : Specification of Pelton Turbine 40 Table 9.3: Specification of Generator 48

Table 9.4: Specification of Transformer 49

Table 10.1 : Alternative Power Evacuation Scheme: Teliya Khola SHP , Dhankuta (996 kW 59 Table 11.1 Power and Energy generated 63

Table 12.1 Unit Rate of Construction Materials 69

Table 12.2 Summary of Project Cost 71

Table14.1 Loan Repayment Schedule 74

Table 14.2 Source of Financing 75

Table 14.3 Financial Parameters fo different Scenarios 75


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1. INTRODUCTION 1.1 BACKGROUND The perennial nature of Nepalese rivers and the steep gradient of the country's topography provide ideal conditions for the development of some of the world's largest hydroelectric projects in Nepal. Nepal has about six thousand small and big rivers hurling from the Himalayas and high mountains towards the plain of Terai. The hydropower potential of these rivers is estimated to be about 83,000 MW of which 42,000 MW is technically and economically feasible. Nepal has generated 562.35 MW power from the hydropower plants, 55.13 MW from the thermal plants. Thus, the total installed capacity is about 700 MW in September 2010. The present power demand in the country is more than 1000 MW which is justified by the fact that load shedding is also happening in rainy season in the year 2010. The demand is increasing by more than 10 percent per annum; however, it is suppressed due to limited supply. With the adequate supply of power, the demand for industrial and commercial use is expected to grow rapidly. Rapid growth of industrial establishments and increasing electrification require more supply of power in future. Therefore, there is enough demand for hydropower energy and hence, there is ample scope of developing small hydropower projects in Nepal.

The Government of Nepal has adopted liberal policy to attract private investment for the development of small hydropower projects. Nepal Electricity Authority (NEA) has recently announced its open price for the projects with capacity up to 25 MW by the private developers. Nepal Electricity Authority will purchase the power at NRs. 4.00 for the wet months and NRs. 7.00 for the dry months. Poush to Chaitra (four months) are considered as dry months. There will be an annual increment of 3 percent in the price for first nine years. The energy price for the project having the capacity more than 25 MW will be fixed with the negotiation.

Mr. Madhav Prasad Lingthep , the developer first identified the site for Teliya Khola Small Hydropower Project in the year 2009. Then a team of experts has made extensive field study to arrive at this outcome. Epsom Engineering Consultancy Pvt. Ltd. and Modern Hydropower and Energy Development Pvt. Ltd. JV has carried out feasibility study in 2010. The project is about 10 km south north east from district headquarter of Dhankuta. The nearest local market is Dhankuta Bazar. Transportation facility is available from Dhankuta upto the Jorpati. There is about 7 kM earthen road upto Teliya VDC. Only 3 kM new road is required for the proposed site.

1.2 APPROACH METHODOLOGY To fulfil the above objectives of the project certain methodologies are adopted, which are: Desk Study, analyze of the previous study, field survey and investigation, and data analysis, project design, quantity and cost estimation, construction planning and scheduling and financial analysis.



1.3 PREVIOUS STUDIES The developer prepared the desk study report of Teliya Khola Small Hydropower Project by hiring technical experts, analyzed the previous studies and data related to the project. The analyses includes the desk study report on Feasibility Study report of Teliya Khola Small Hydropower Project by the developers , topographical maps, socio-economic, hydrological, stream flow data as well as other available published information.

1.4 OBJECTIVES OF THE STUDY The present study has the following activities:

i) Study and review of the available data and information on the Project;

ii) Topographical, geological and environmental field investigation of the Project site together with hydrological study and investigation of Teliya Khola;

iii) Assessment of the power potential of the Project site and optimization of the proposed plant with respect to the size of the plant, i.e. the installed capacity;

iv) Study of the Project with interconnection to the national power grid and evaluation of this concept with all relevant implications:

v) Layout, feasibility study level design and dimensioning of all the Project components;

vi) Tentative cost estimate of the transmission line in the Project area including interconnection to the national power grid;

vii) Preparation of the bill of quantities and estimation of the Project cost;

viii) Financial and economic evaluation of the Project;

ix) Preparation of report including all drawings and details essential for the feasibility study.

Besides, the outputs of the current study are manifold. Some of the main outcomes of this study are:

i) Establishment of the main technical parameters of the Project;

ii) Determination of the optimum Project layout;

iii) Fairly accurate estimation of the Project cost;

iv) Determination of the financial indicators of the Project;

v) Establishment of a strong base for further studies and detailed design of the Project.



2. DESCRIPTION OF THE PROJECT AREA 2.1 LOCATION Teliya Khola Small Hydropower Project is located in Teliya and Parewadin VDC of Dhankuta district and Hamarjung VDC of Terhathum district. The project site lies in Eastern Development Region of Nepal. It is located in between latitude 27o 00' 00" and 27o 02' 40" North and between longitudes 87o 25' 23" and 87o 26' 36" East. The project boundaries are also presented in table 2.1 below. The catchment area of the project site at headworks is about 38 km2. The high mountain peaks ranging in elevation upto 2700 m surround the basin.

Table 2.1: Geographical coordinates of the project

Particulars Latitude, N Longiture, E

Project Area Boundary 2700'00" to 2702'40" 8725'23" to 8726'36"

The basin is characterized by steep gradient and surrounding mountains are characterized by mild

sloped landscape, alluvial terrace varies with elevation. Settlements and mixed forests are found in the catchment. The snowfall is experienced seasonally in higher mountains.

2.2 PHYSICAL FEATURES Most part of both Teliya and Parewadin VDC have been electrified by National Grid. The project area in other aspect is back in development.



2.3 ACCESSIBILITY

Fig 2.1: Project Location

All weather roadhead for this scheme is Jorpati of Dhankuta district. Gravel road is available upto Chulachuli. Seasonal road is available upto Teliya. Only 3 kM access road is required to implement this project.



3. FIELD INVESTIGATION AND DATA COLLECTION 3.1 TOPOGRAPHICAL SURVEY Topographical survey of project site had been carried out in March 2010 by Total station. Topographical mapping for about 10 hectors of project area i.e. head works site, headrace canal alignment site , fore bay site, penstock site and powerhouse site were prepared for 1:10000 and 1:1000 scale for general layout of the project site and at other scales for showing the plan of various structures as shown in drawing section.

The present status of topographic maps prepared is as follows:

1. Weir and intake site area, scale 1:200 with contour lines of 1m intervals.

2. Powerhouse area, scale 1:100 with contour lines of 1m intervals.

3. Project area (General Layout Plan), scale 1:10000 with contour line of 5 m intervals.

4. Waterways alignment, scale 1:1000 with contour lines of 1 m intervals.

5. Cross section survey in weir site areas, Powerhouse and tailrace area.

All these maps are prepared in digital format. The relevant design drawings are presented in Volume II of this report.

3.2 COLLECTION OF AVAILABLE HYDROLOGICAL DATA The Teliya Khola does not have any permanent flow gauging station so the long term flow data are not available. The ungauged hydrological models are used for the hydrological analysis of the project. More details are presented in hydrological report section of this report.

3.3 STREAM FLOW DATA

The discharge of the stream was measured in March 23, 2010 by salt dilution method and is found to be 206 lps. There are no gauging stations installed in this stream basin and the only reliable means of flow analysis is MIP analysis with spot flow measurement for short interval of time. Since the catchment area of the scheme is very small, i.e, 38 km2 , MIP method is used for hydrological analysis.

3.4 SEDIMENTATION DATA Sediment size distribution and the particle size distribution are required for the design of the desanding basin. There is no data available on Teliya Khola and its adjacent basins. Therefore the data had to be estimated based on the Himalayan Sediment Technique.



3.5 GEOLOGICAL INVESTIGATION Geological investigation of proposed Teliya Khola Small Hydroelectric Project was carried out in the month of March 2010 by the technical team of the consultants. The results and description of the findings are given in geological section of this report.

During this study, previous literatures and information related to the project site were collected and field study data were analyzed. During the field visit, additional information were collected, analyzed and reviewed.



4. HYDROLOGICAL STUDIES

4.1 CATCHMENT CHARACTERISTICS The Teliya Khola is a tributary of Tamor River. The Tamor River is a major tributary of Arun River. Arun River is a major tributary of Koshi River. The Teliya Khola lies in between Dhankuta and Terhathum District. The total catchment area of the Teliya Khola at the proposed headworks site of the Teliya Khola Small Hydropower Project is about 38.00 km2. The Teliya Khola is a perennial river. The water of Teliya Khola originates from Mahabharata hills with the highest peak (Sukrabare Dada) at elevation 2702 m.

The boundary line of the project is 27 00' 48" N to 27 02' 28" N as latitudes and 87 25' 23" E to 87 26' 37" E as longitudes. The proposed headworks site of the Teliya Khola Small Hydropower Project lies at about elevation of 763.00 m. It is about 5 km upstream from the confluence with Tamor River. The proposed powerhouse site of the Teliya Khola Small Hydropower Project lies at about elevation of 620.00 m and located at about 3 km upstream of the confluence with the Tamor Khola.

The average gradient of the river in between the dam site and powerhouse site is about 4.5 %. The Teliya Khola basin drains towards north-south direction. Based on the topographical maps, there are no lakes within the Teliya Khola basin. The Teliya Khola basin is mainly covered with scattered settlement and mixed forest around the streams in the catchments. Agricultural fields on terraces and scattered settlements dominate the area below 2,200 m. The information regarding the Teliya Khola drainage area has been obtained based on the topographical maps of 1:25,000 scale compiled from aerial photography of 1996 by the Survey Department of the Government of Nepal. The catchment area of the Teliya Khola at headworks site of the project is shown in Fig 4.1 below.

Fig 4.1: Catchment area of Teliya Khola at proposed headworks site



4.2 DRY FLOW MEASURMENT Since the catchment area of the project is small, i.e, 38 km2, the hydrological analysis is based mainly on spot flow measurement at site. The flow measured in March 23, 2010 is taken as the reference for the hydrological forecast base on Medium Irrigation Project (MIP) Method. The field measurements are given in the table below.

Table 4.1: Dry flow measurement of Teliya Khola

4.3 REFERENCE HYDROLOGY AND STREAM FLOW DATA

4.3.1 Stream Gauging The Teliya Khola, being an ungauged river, a field measurement of river discharge was made at the proposed headworks site of the Project on March 23, 2010. The discharge of the river was measured as 0.206 m3/s by salt dilution method.

4.3.2 Mean Monthly Flow There are mainly three methods to derive the long term mean monthly flow. They are MIP and Hydest (WECS/DHM) models and data generation from similar catchment. The catchment area of the Teliya Khola Small Hydropower Project is very small and the nearby catchment area with gauged river is not available. Therefore the data generation from similar catchment is not used in this project. The other two methods which are used are briefly described below. MIP Method Using the field discharge measurement on March 23, 2010 and the MIP method of generating long-term mean monthly flow data, the results are presented below in Table 4.2. The Teliya Khola lies in region 4 according to MIP methodology.



Table 4.2: Mean monthly discharge (m3/s) by MIP method

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0.417 0.303 0.222 0.161 0.353 0.604 1.110 4.393 3.368 1.110 0.805 0.554

The long-term mean annual discharge at the headworks site is about 1.116 m3/s from the above MIP method.

WECS/DHM Method A study on 'Methodologies for Estimating Hydrologic Characteristics of Ungauged Locations in Nepal' was published out by WECS and DHM in July 1990. This method is also called Hydest Method. This study uses the approach of multiple regression equations relating the physiographic and climatologic characteristics of the selected basins to the average monthly flow values. Altogether twelve individual monthly regression equations were developed.

The results of this study are used as an alternate approach for estimation of mean monthly discharges at the headworks site of Teliya Khola. The mean monthly discharges from WECS/DHM method are shown in Table 4.3.

Table 4.3: Mean monthly discharge by WECS/DHM method

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0.511 0.436 0.382 0.365 0.457 1.759 5.422 6.661 5.162 2.272 1.011 0.667

4.3.3 Adoption of Design Discharge The comparison of the derived long-term mean monthly flows at the proposed intake site by various methods is shown in Table 4.4.

Table 4.4: Comparison of long-term mean monthly discharges

Month Design

Discharge (lps) MIP Method (lps) WECS/DHM Method (lps) Feb 850 303.00 436.35 Mar 850 222.00 382.18 Apr 850 161.00 364.71 May 850 353.00 457.06 Jun 850 604.00 1758.88 Jul 850 1110.00 5421.75 Aug 850 4393.00 6660.59 Sep 850 3368.00 5161.92 Oct 850 1110.00 2271.85 Nov 850 805.00 1010.99 Dec 850 554.20 666.54

Average 850.00 1116.68 2092.02



The above table shows that the derived long-term mean monthly flows at the intake site are quite comparable. In most of the cases, the WECS/DHM method gives higher estimates whereas MIP method gives lower estimates. Since the MIP method uses local data to adjust the regional hydrograph, it should give reasonably accurate estimates through the dry season months, which are critical in assessing the power and energy during the dry season. Hence, the derived mean monthly flows from the MIP method have been adopted for this feasibility study purpose.

The long-term annual hydrographs of Teliya Khola based on average monthly flows carried out by different methods at the proposed headworks site are shown below in Chart 4.1 and Fig 4.2. The horizontal straight line that gives an idea of availability of water for hydropower generation represents the design discharge.

Comparison of MIP and Hydest Flow

0

1000

2000

3000

4000

5000

6000

7000

Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Time in Months

Dis

char

ge in

lps

Design Discharge (lps)MIP Method (lps)WECS/DHM Method (lps)Design Discharge (lps)MIP Method (lps)WECS/DHM Method (lps)

Fig 4.2: Long-term annual hydrograph of Teliya Khola by various methods

4.4 FLOW DURATION CURVE A flow duration curve (FDC) is a probability discharge curve that shows percentage of time a particular flow is equaled or exceeded. Since MIP method is adopted for hydrological analysis, FDC is also prepared based on this method. The probability of exceedance and the corresponding discharge are shown in Table 4.5 below.



Table 4.5: Probability of exceedence and discharges

S.N. Probability of Exceedence Discharge (lps) 1 8.33% 4393.00 2 16.67% 3368.00 3 25.00% 1110.00 4 30.00% 1094.00 5 33.33% 1110.00 6 40.00% 850.00 7 41.67% 805.00 8 50.00% 604.00 9 58.33% 554.20 10 60.00% 511.00 11 66.67% 417.00 12 70.00% 375.00 13 75.00% 353.00 14 83.33% 303.00 15 91.67% 222.00 16 100.00% 161.00

The flow duration curve of Teliya Khola at proposed headworks site is shown below in Fig 4.3 based on the Hydest method. The design discharge 0.85 m3/s is the 40% probability of exceedance.

Flow Duration Curve

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

8.33% 16.67% 25.00% 30.00% 33.33% 40.00% 41.67% 50.00% 58.33% 60.00% 66.67% 70.00% 75.00% 83.33% 91.67% 100.00%

Probability of Exceedence

Flow

in lp

s

FDC-Teliya Khola Intake

Fig 4.3: Flow duration curve at headworks site of Teliya Khola (Note: The curve for 25% 6o 33.33% probability of exceedence seems straight-line since for region 4 , MIP has same unit flow for july and October. )



4.5 FLOOD HYDROLOGY In the hydropower projects, high floods are required to be computed for designing the headworks structures as well as the powerhouse complex. It has been a common practice to analyze the flood events that might occur during the driest periods for the purpose of the construction of diversion headworks structures. Flood hydrology has been analyzed in two parts- design high floods for the design of headworks, powerhouse, and other hydraulic structures and dry season floods for the construction of river diversion structures.

4.5.1 Design High Floods The study on 'Methodologies for Estimating Hydrologic Characteristics of Ungauged Locations in Nepal (July 1990)' published by WECS/DHM uses the approach of regional flood frequency analysis. The results of this study are used for estimation of flood discharges at the proposed headworks site as well as the powerhouse site.

The study shows the results from the frequency distribution parameter prediction method, which is a variation of the multiple regression method. The independent variable that is found to be the most significant in all of the regression analyses is the area of the basin below 3000 m elevation. This area represents the portion of the basin that is influenced by the monsoon precipitation. In addition, Hydrological Studies of Nepal (1982) published by WECS uses the same parameter.

The catchment area below 3000 m elevation at headworks site of the Teliya Khola Small Hydropower Project is 38 km2. The results of the flood estimates from the Hydest method are presented in Table 4.7 below.

Table 4.6: Estimated high floods for Teliya Khola

Return Period (yrs) Daily (m3/s) Instantaneous (m3/s) 2 27 47 5 42 81

10 53 109 20 64 138 50 79 180 100 92 215 200 104 254 500 123 309 1000 137 356 5000 174 478 10000 191 537

As a general practice, instantaneous peak flood with a return period of 100-year is adopted as the design flood. Hence, for the hydraulic design of headworks structures and tailrace structures, the corresponding adopted design flood is 215 m3/s.



4.5.2 Low Flow Analysis The duration curve of long-term inflow series predicts the flow duration for an average hydrological year. Individual dry and wet years would display different flow duration characteristics. For a hydroelectric plant, sustained low flows experienced in dry years are critical to the operation resulting in nil energy generation when the flow decreases below the minimum permissible limit. The low flow discharge values, in hydropower projects, not only decide the design flow to be diverted but also serve for environmental purposes as to how much water must be left in the river system for the survival of the downstream aquatic flora and fauna. In order to predict the likelihood of this occurring, a probabilistic low flow analysis is carried out using the methodology by WECS/DHM for ungauged river basins. The results of the low flow analysis are given in Table 4.7 below. Table 4.7: Low flow frequency analysis

Return Period (Years) Daily Low Flow (m3/s)

2 0.27 10 0.09 20 0.06

4.6 COMPENSATION FLOW The long-term mean monthly flow for the driest month, April, at the intake site is 0.161 m3/sec from the MIP method. A flow equivalent to 10% of the driest flow, i.e., 0.0161 m3/sec will be released downstream as the compensation flow for downstream habitants in the river for fulfilling environmental protection requirements.

4.7 CONCLUSIONS AND RECOMMENDATIONS

4.7.1 Conclusions The following conclusions have been drawn at the end of the hydrological studies performed under this chapter:

The adopted design discharge is 0.85 m3/s corresponding to 40 % dependable flow. The 100-year design flood is 215 m3/s at the proposed headworks site. The mandatory compensation flow in Teliya Khola downstream of the proposed

diversion weir is 0.0161 m3/s.

4.7.2 Recommendations Based on the conclusions drawn above, it is recommended that frequent discharge measurements of Teliya Khola shall be made before the implementation of the project to verify the long term mean annual flows.



5. SEDIMENTATION STUDY 5.1 SEDIMENTOLOGY The sediment transportation by rivers originating from the Himalayas is found quite high in Nepal especially during peak monsoon floods. The sediment concentration and particle size of sediments are very important to design the desanding basin and hydraulic structures. The sediment yield in Teliya Khola is found due to the river gradient, landslides, gully erosion in upper reaches, bank erosion, fragile geological conditions, etc. Teliya Khola carries sediments ranging from silt to huge boulders by cutting both of its banks as well as those transported into it by its tributaries. It is essential to remove the sediment loads not to cause severe abrasion to the runner and other parts of the turbine.

In the absence of sediment data of Teliya Khola at proposed project area, analysis of sediment load is carried out by prevailing empirical methods- Himalayan Sediment Yield Technique, and Regional Studies.

5.1.1 Himalayan Sediment Yield Technique In accordance with Himalayan Sediment Yield Technique, the physiographic zones are divided into five regions with probable range of sediment yields. The Zone Specific Sediment Yield (ZSSY) has been given below:

Physiographic Regions Range of yield (t/km2/year)

Tibetan Plateau 500-1000

High Himalayan 300-1000

High Mountain 1000-4000

Middle Mountain 3000-8000

Siwalik 5000-15000

The Himalayan Sediment Yield Technique involves estimating sediment yields for various physiographic zones multiplying the sediment yields by corresponding catchment areas. The equation is:

Sediment Yield (t/km2/year) = Zone Specific Yield x Zone Catchment Area

In this technique, the catchment boundary is divided into different physiographic zones depending upon geological conditions, rainfall and slope of catchment areas. The major area of the catchment basin is dominated by settlements and contributes less volume of sediments. The Teliya Khola Basin falls in middle mountain region and corresponding specific sediment yields is considered as 5000 t/km2/year. The catchment area of Teliya Khola Small Hydropower Project is



38 km2. Hence, the estimated sediment yield of Teliya Khola at proposed headworks site is about 0.190 million tons per year.

5.1.2 Regional Studies This method was developed by K. P. Sharma and S. R. Kansakar (1992) after studying the sediment data of 12 river catchments of Nepal. It is based on regression equations to compute the sediment transport. This regression equation is applicable to the Middle Mountains and Siwaliks. The equation is:

Asy = - 2.20992 + 0.05439(Arock)0.5 + 0.0748(A2000)0.5 + 0.05097(MWI)0.5

Where,

Asy = Total annual suspended sediment yield in million tons

Arock = Area of rocky catchment = 20 km2

A2000 = Catchment area below 2000 m = 25 km2

MWI = Monsoon Wetness Index in mm = 1500 mm

The above equation gives the annual suspended sediment yield of 0.325 million tons per year. Assuming 20% bed load of the suspended yield, total annual sediment is estimated to be about 0.389 millions tons per year at headworks site.

5.2 CONCLUSION AND RECOMMENDATION The recommended mean annual sediment concentration at the intake site is 0.389 millions ton per year. It is also strongly recommended that the measurements of suspended sediment be carried out in the future on a daily basis covering the principal months of the monsoon period and including discharge measurements so that a sufficient data base is available for a reliable and representative assessment of suspended sediment transport in the Teliya Khola at the proposed headworks site.



6. GEOLOGICAL STUDIES 6.1 REGIONAL GEOLOGY The Himalaya is a part of the great arcuate orogenic belt in central Asia extending from east to west, about 2500 km length with width of 230 to 350 km. The Himalaya was evolved as a result of repeated deformation of the sedimentary successions that accumulated in the Tethys sea lying between the Indian continent in the south and the Eurasian continent in the north. It lies in a unique geological position i.e. the Indian subcontinent with normal thickness (35 km) to the south and the Tibetan plateau the highest plateau in the world, with a double crustal thickness (70 km), to the north (Thakur 2001). The origin of the Himalaya was attributed to the continent-continent collision of the Indian and the Eurasian plate around 55 million years ago. Due to the continued movement of the Indian plate, the northern margin of the Indian continent was sliced into slivers along the three principal intracrustal thrusts: the Main Central Thrust (MCT), the Main Boundary Thrust (MBT), and the Himlayan Frontal Thrust (HFT) from north to south respectively (Gansser 1964; Schelling and Arita 1991). The Higher Himalayan Crystalline (HHC) thrust sheet consists of amphibolite to granulite facies metamorphic rocks and is separated by a normal fault, the South Tibetan Detachment Fault (STDF) from the overlying Cambro- Ordovician to Eocene Tethys Sedimentary Series (TSS) (Burg et al. 1984; Pecher 1991).Further south the HHC over thrust to the low grade (greenschist to lower amphibolites facies) metasedimentary rocks of the Lesser Himalayan Sequence (LHS). Similarly the MBT carries the LHS on to the Mio-Pleistocene Siwalik rocks. The Himalayan Frontal Thrust (HFT) is the youngest thrust and forms the boundary between the Siwaliks and Quaternary sediments of the Indo-Gangetic plain.

Fig 6.1: Geological Map of Nepal Himalaya (After Dahal, R.K., Hasegawa, S., 2008



Auden (1935), Lombard (1952, 1958), Bordet and Latreille (1955) Bordet (1961), Hagen (1969), Kyastha (1969), Hashimoto et al. (1973), Schelling (1989), Schelling (1992), Upreti et al. (2000) Chamlagain (2000) and Rai et al. (2001) studied the geology of the eastern Nepal. The extensive thrust sheet covering the most of eastern Nepal represents the HHC zone in the eastern Nepal. The area has been well mapped by Schelling and Arita (1991). The deep erosion of this thrust sheet has produced large window e.g. Taplejung and Arun window in the eastern Nepal. The LHS is characterized by low-grade metamorphic rocks of greenschist to lower amphibolite facies metamorphic rocks (Rai, 2001). 6.2 GEOLOGY OF PROJECT AREA 6.2.1 Lithology Geologically the project area lies in Himal Gneiss, Panglema Quartzite of Himal Group and Sarung Khola Formation of Kathmandu Group whose geological age is Precambrian. The project area is characterized by medium to coarse grained quartz muscovite biotite schist, banded gneisses, gneiss and schist.

Fig 6.2: Geological Map of Project Area 6.2.1.1 Slope and Aspect

Triangulated Irregular Network (TIN) is a list of points with their coordinates that are stored into a file that also contains information about the topology. TIN objects contain four element types: nodes, edges, triangles, and hulls. Nodes are the most fundamental element of a TIN and the only element type that references spatial coordinates (x,y,z). An edge is an oriented line segment that connects two nodes. Three edges connect three nodes to form a triangle that satisfies the Delaunay criterion. Triangles represent elementary areas of the surface that describe topological relationships between all other elements of the TIN data. A hull represents the area covered by a TIN structure. Interpolation of z-values is only valid



within a hull region. With the help of topographic coverage map TIN of the area is prepared and is shown below.

Fig 6.3: Triangulated Irregular Network of the project Site on the basis of Counter height

Slope is computed by dividing a line's vertical rise or fall by the distance the line travels on the surface (the "rise over the run") - usually expressed as a degree. The slope map shows that headwork area has slope of 20-30 degree and penstock alignment manly passes through slope of 30 to 50 degree where as powerhouse area has slope of 0 to 10 degree which is shown below.

Fig 6.4:Slope Map of the project area



The compass direction towards which a slope faces, measured in degrees from North in a clockwise direction is the aspect. Most of the projects areas have east to Northeast face aspect.

Fig 6.5.:Aspect Map of the project area

6.2.2 Geological and Geotechnical Investigation

Fig 6.6:Landuse Map of the Project area



6.2.2.1 Headworks Area The proposed Headworks area lies around 20m upstream from the confluence of the Chhak Khola and Teliya Khola in the Left bank of Teliya Khola. The bedrock is characterized by grey color fine to medium grained strong Gnesiss rock having RQD more than 60% and weathering grade of II degree

Fig 6.7 : Intake area

6.2.2.2 Desanding Basin Area

The desanding basin lies in right bank of Tame Khola on the cultivated terrace. The test pit of 1mX1m was dug to understand the subsurface condition of the area and the result is shown in the table. The cultivated terrace is characterized by Gravely Clay SAND. The examination reveals that the materials are alluvial deposits.

Table 6.1: Output of Pit Analysis (Desanding Basin) Type of Material Content

Boulder 10%

Gravel 15%

Sand 70%

Fines 5%

Total 100%



Fig 6.8.: Test Pit in Desanding Area

6.2.1.1 Fore Bay The penstock alignment passes through moderately strong gneiss rock with weathering grade of III to IV degree. And reached to the cultivated area near to the channage 1+ 635 .This area is suitable for the construction of the Forbay.

Fig 6.9: Location of Forebay showing pit during field survey

1mX1m test pits was dug to understand the subsurface geological condition of the area and the result is shown in table.

Table 6.2: Output of Pit Analysis (Forebay) Type of Material Content

Cobbles, gravel 30%

Sand 40%

Fines 30%

Total 100%



6.2.2.3 Penstock Alignment In most of the section the penstock alignment passes through forest area. At the beginning the penstock alignment passes through the left bank of Teliya Khola but after 70m from the intake it crosses the Khola and runs toward right bank of Teliya Khola to reach the fore bay. The area is characterized by medium to strong strength, medium to coarse grained quartz muscovite biotite schist, banded gneisses with weathering grade of II to III degree.

Fig 6.10: Penstock Alignment

6.2.2.4 Powerhouse Site The proposed powerhouse lies in the right bank of Teliya Khola. The powerhouse area is characterized by cultivated terrace of alluvial deposits.

Fig 6.11: Pit in Powerhouse Area



1mX1m test pits was dug to understand the subsurface geological condition of the area and the result is shown in table.

Table 6.3: Output of Pit Analysis (Powerhouse)

Type of Material Content

Cobbles, gravel 10%

Sand 50%

Fines 40%

Total 100%

6.3 SEISMICITY Interseismic monitoring of deformation with the help of the GPS geodesy indicates that Main Himalayan Thrust is locked along the Himalaya of Nepal and the stress build up at the tip of locked zone is responsible for the belt of micro seismic activity that runs along the front of the high range. Motion along the Main Himalayan Thrust is thus probably stick slip and must produce recurring large earthquakes similar to 1934 Nepal Bihar event. The moderate magnitude earthquake is generated from thrust fault which originate within the microseismic belt in front of the high Himalaya in the ramp. The belt of microseismicity at the front of higher Himalaya is continuous and makes a straight trend from 87E to 82 E. west of 82E the seismicity belt is much wider and diffused. This feature is well correlated with proposed imbrications of thrusts in geological section (DeCelles et al 1998). Thus Nepal Himalaya can be broadly divided into two distinct section Eastern and Western seismic belt along transverse feature passing near 82E longitude.

The generation of earthquakes is confined to the crystal depth of about 20 km. In this region it is generated as a result of release in stresses that are accumulated in the geodynamic under- thrusting process of the Indian plate against the Eurasian plate. The shallow depth earthquakes of the depth up to 6-Km are the result of strike slip dislocation. Earthquakes of greater magnitudes are recorded from the south of the seismicity belt and small and medium earthquakes have been recorded along the Himalayas seismic zone. The seismic zone seems to run through middle part of country sub parallel to the Himalayan chain confining between two major tectonic features MCT and MBT. There has not been any large earthquake since 1934. According to Bajracharya (1994), the project area lies in the medium risk zone.



Fig6.12: Simplified seismic risk map of Nepal after Bajracharya 1994 6.4 CONCLUSIONS AND RECOMMENDATIONS

Teliya Khola Hydropower project lies in Teliya VDC of Dhankuta and Parewadin VDC of Terhathum in Eastern Development Region of Nepal. Geologically the project area lies in Himal Gneiss, Panglema Quartzite of Himal Group and Sarung Khola Formation of Kathmandu Group whose geological age is Precambrian. The project area is characterized by medium to coarse grained quartz muscovite biotite schist, banded gneisses, gneiss and schist. The project is of run-of river type and all major structures will be constructed on surface. Only small protection work is required in some part for slope stabilization. The present geological studies show that the area is suitable for the construction of Hydropower project.



7. STUDY OF ALTERNATIVE LAYOUT 7.1 HYDROPOWER PROJECT ALTERNATIVES

Alternative sites were studied before finalizing the proposed site. The studied site was the only feasible site as per the available site conditions like design head and flow. The length of headrace for this scheme is about 1616 m long with penstock length of 266 m. Apart from the site, the two distinct alternatives are as following:

All Penstock Pipe (Alternative I) Headrace Canal Plus Penstock Pipe (Alternative II)

Option I : All penstock Pipe

Option I was studied in detail and this site is not recommended because of the following reasons.

The length of headrace is very long for available flow and head conditions. The penstock pipe should be exposed in possible cases and in such case , it might

create problem in paddy field.

It is very difficult to install the penstock pipe in rounded terrain where there are a number of bends in the alignment. The civil structures will be complex and it may also increase the project cycle.

The major cost of buying and installing penstock pipe goes out of the project area thus this option minimizes local employment.

Additional access road may be required to lift huge penstock pipes which increases the project cost.

Option I : Headrace Canal Plus Penstock

This option is the only feasible option for this project site. This option is chosen because of the following reasons.

It is easier to construct headrace canal. Construction materials like stone, sand and aggregate are easily available around the

project area.

Both local skilled and unskilled people can get longer employment by this option. Construction period will be minimum as compared to penstock option is such

topographical conditions.

Hence, option II with headrace canal plus penstock pipe is chosen for this project.



8. PROJECT OPTIMIZATION 8.1 Range of Options 8.1.1 General The optimization of the design discharge and thereby the installed capacity has been carried out for the selected layout of combined canal and penstock pipe option. The present study is based on the river hydrology, project layout with intake, desanding basin, conveyance system (consisting of crossing, headrace canal and penstock) and powerhouse. The prevailing topography of the project site is suitable for a simple run of river plant. The principle objective of the optimization study was to optimize the following:

The plant capacity and corresponding plant discharge, The diameter of the penstock pipe of the water conveyance system for each plant

capacity option. The optimization of the plant capacity is carried out with the optimization of design discharge. In case of simple run-of river scheme, height of the weir, minimum operating level and high flood level have insignificant impact on the design discharge. These elements are more influenced by the general topography of the diversion weir site, design flood magnitude and the river characteristics, which are common to all installed capacity options. Therefore, all the options are based on the respective discharge and subsequent hydraulic design of the water conveyance system from the river intake to the powerhouse. 8.1.2 Assumptions The optimization of the plant-installed capacity is based on the following assumptions:

A compensation flow of 0.016 m3/s is required to be released downstream of the headworks. This flow corresponds to the 10% of the minimum monthly flow as per the prevailing practice.

Self consumption, losses and outage has been assumed to be 10 % of the total annual energy.

The combined efficiencies of turbine, generator and transformer have been assumed as 86 % respectively.

The optimization of the installed capacity of the plant or the design discharge of the plant was undertaken by economic analyses with results expressed as economic internal rate of return (EIRR), benefit cost ratios and specific energy costs. Five different installed capacities/discharges have been considered for the optimization process. Dimensioning and cost estimates for each option were prepared. The power benefits were determined for each option and compared with the costs. The objective was to determine the element size, which minimizes the specific energy cost (levellized cost of generation) and maximizes the benefits of power supply described by the discounted benefit/cost ratios and EIRR. 8.1.3 Approach and Methodology The optimization procedure in this study follows the general approach outlined below:



1. To establish a series of discharge options based on the hydrology, 2. To estimate the minimum operating level based on the diversion requirement and flushing

requirement of the desanding basin and the location of the proposed surface desanding basin. This will be the same for all options.

3. To estimate the size of free flow spillway and undersluice to pass the design flood of 1:100 year. This too will be common for all options.

4. To prepare preliminary design of intake, approach canal, desanding basins, flushing structure, forebay water conveyance system, powerhouse and the tailrace for each capacity option.

5. To optimize the diameter of the surface steel penstock pipe for each capacity option.

6. To estimate the costs of the individual structures for each capacity option and determine the total project cost of each option.

7. To determine the quantum of monthly and annual energy generation and estimate the corresponding benefits.

8. To conduct the economic analysis for each option. 8.1.4 Optimal Installed Capacity In order to determine the optimal installed capacity, it was necessary to study a range of capacities within which the optimal option can be found. The following range of plant capacities (Table 8.1) was selected in order to adequately define the trend of the benefit cost analysis. The plant capacities were adopted as given below, within which the optimum capacity is expected to lie. Then the corresponding discharges were derived for each capacity assuming an overall efficiency of turbine, generator and transformer as 86%. The gross head is calculated from normal water level at the forebay to the center of turbine. The head loss in the penstock pipe has been estimated for each option. Table 8.1: Range of Options

S.N. Options Percentage of flow exceedance

Design Flow (m3/s) Net Head (m)

Installed Capacity (kW)

1 Option A 30 1.094 138.97 1283 2 Option B 40 0.85 138.94 996 3 Option C 50 0.588 138.97 689 4 Option D 60 0.511 138.87 599 5 Option E 70 0.375 138.81 444

The capacity and energy potential of a particular option is dependent on the river flows. The long-term monthly river flows (Table-8.2) generated at the intake site of the project has been used in the computation of the energy. To maintain aquatic life in the dewatered reach of the river, 10% of the minimum monthly average flow i.e, 0.016 m3/s is released from the headworks. This has been deducted from the river flows while assessing the energy potential of the different options.



Table No. 8.2: Average Monthly Flows S.N. Month Available Mean Monthly Flows (lps)

1 January 417 2 February 303 3 March 222 4 April 161 5 May 353 6 June 604 7 July 1110 8 August 4393 9 September 3368 10 October 1110 11 November 806 12 December 554

8.2 Conceptual Layout and Dimensioning The proposed project is conceived as a simple run of river type plant. The main civil components of the project are: diversion weir, sluice structure, intake structure, crossing, gravel trap, connecting canal, desanding basin, forebay, penstock, and powerhouse and tailrace conduit respectively.

The diversion weir has its spilling length of 30 m. Sluice structure has been placed on the right bank of the river. A divide wall is provided in between the diversion weir and sluice structure parallel to the watercourse. Intake structure is aligned at about 970 with the weir axis. The crest level of the diversion weir is fixed at an elevation of 763 m above mean sea level (msl). By such layout of the Intake structure, negligible bed load (sand and gravel) will enter into the canal through the trash rack. The side intake having single opening of size 1.2 m x 1 m to be constructed at the intake to trap water from the river. There is a 20 m long rectangular canal, just after the canal gate at the intake. A gravel trap is associated in the intake structure near the undersluice. A desanding basin is placed on the alluvial deposited bushy area on the right bank of the river. The desanding basin is 3 m above the existing riverbed so that the flood level in the river will not damage the structure. There is also flushing system to flush the sediments. The discharge during the closure of the machine and overflow of water passes to the Teliya Khola through the spillway.

The penstock pipe of about 266 m (upto bifurcation point) in length is aligned on the slope between the desanding basin and the powerhouse on the right bank of Teliya Khola.

The powerhouse and the tailrace structures are placed in the forest area on the right bank of the Teliya Khola. A powerhouse of 18.4 m * 10.27 m size will be constructed in the plain area at an elevation of 720 m from the mean sea level. The location of the powerhouse is designed in such a way that the discharge to the units can be delivered by a single penstock bifurcated just before the powerhouse. Pelton turbines will be used. Discharge coming out of the turbine is delivered by two separate channels which afterwards are combined to a single covered rectangular type tailrace conduit of 1.5 m *2.0 m size and thereby the discharge passes to the Teliya Khola. The centre line of turbine will be at 720 m.

8.3 Estimate of Energy Production



The calculation of energy is made considering the 10% outage. The dry energy cost is taken as NRs 7/kWh and the wet energy cost is NRs 4/kWh. The energy production and revenue of the different options are shown in the Table 8.3 Table 8.3: Energy and revenue calculation

S.N. Options Percentage

of flow exceedance

Design Flow (m3/s)

Installed Capacity

(kW)

Annual Energy (GWh)

Minimum Annual Revenue (NRs

000)

1 Option A 30 1.094 1283 5.917 26,506

2 Option B 40 0.85 996 5.359 24,495

3 Option C 50 0.588 689 4.195 19,622

4 Option D 60 0.511 599 3.815 18,068

5 Option E 70 0.375 444 3.091 14,975

8.4 Cost Estimates The cost estimates for the optimization study are preliminary one. Out of the five options, the cost calculation for one option is made in detail and then the costs of others are calculated based on the changed structures. Based on the preliminary layout and the design of the individual structures of different capacity option, the cost estimation is prepared. Summaries of the cost for each option are shown in Table 8.4. Table 8.4: Summary of Project Cost (000)

SN Particulars Option

AOption

BOption

COption

D Option

EA Discharge availability (%) 30 40 50 60 70 B Design Discharge (m3/s) 1.094 0.85 0.588 0.511 0.375 C Capacity in kW 1283 996 689 599 444 1 Civil Works 77897 66605 53517 49594 41535 2 Electromechanical Equipments 53766 40903 32259 30109 25808 3 Transmission Line 4500 4500 4500 4500 4500 4 Road and Site Facilities 14030 8798 11040 8625 8050 5 Environmental Cost 4140 2645 2415 2415 1898

6 Engineeerring and Administration Cost

12347 9876 8298 7619 6543

7 Miscellaneous Cost 15433 12345 10373 9524 8179 8 Interest During Construction 18211 14567 12240 11239 9651 9 Total Project Cost 200,324 160,238 134,643 123,625 106,164 10 Cost per kW 2,082 2,145 2,606 2,752 3,188

8.5 Economic Analysis



8.5.1 Economic Parameters Optimization study for this project used an annual energy price provided by NEA for calculating the benefits. According to new policy, NEA will buy the power at NRs 7/unit for dry season and NRs 4/unit for wet season. Poush, Magh, Falgun and Chaitra, four months are taken as the dry months and remaining eight months are taken as wet months. This buying rate is only for the first year after completion of the project. There are 9 yearly increments with 3 percents. This increment is not considered in the optimization study. In order to estimate the capacity and energy potential of the different options, a spreadsheet model was developed. In determining the capacity and energy potential of each plant capacity option, the model takes into account the following:

Average energy based on annual flow duration curve at the dam site. The net head has been calculated for each option. The reduction in available flow due to the requirement of compensation flow release. For

the purpose of the plant capacity optimization a release of 0.016 m3/s was adopted. This flow corresponds to the 10% of the minimum monthly flow.

Scheduled and unscheduled outage, losses and self consumption is taken as 10% for this study.

8.5.2 Economic Results

Economic analysis has been performed to find the capacity at which the cost per kilowatt and specific energy cost is the lowest and the capacity at which the net present value will be the maximum. For the purpose of economic analysis the replacement costs of electro-mechanical equipment and transmission line have also been taken into account. Analysis was conducted by including all the costs to construct, operate and maintain the project. Costs and energy benefit streams were assessed at present value at 10% discount rate in order to arrive at present day energy cost. In order to compare the different options on the basis of specific energy cost, EIRR and benefit cost ratio, the present value of the costs and benefits of all the options were determined to the year before construction. Economic analysis of all capacity options were carried out. These analyses were based on the following assumptions:

The construction period is assumed to be 2 years for all options. Economic Life of the Project : 50 years Economic Life of Electromechanical equipment: 25 years Economic Life of transmission line: 25 years Discount Rate : 10 % The exchange rate of 1 US$ is equal to 75.00 NRs Annual cost of operation and maintenance is taken as 1.5 % of the project cost.

The various economic indicators like the specific energy cost, benefit cost ratio, net present value (NPV) and the economical internal rate of return (EIRR) were calculated for all of the cases of the different capacity options. The summary of the results of the economic analysis for all the cases are shown in Tables 8.5.



Table 8.5: Results of Economic Analysis

S.N. Options


Project Cost (106 NRs)

Cost per kW in US $

Specific Energy Cost (NRs/kWh)

IRR (%)

B/C Ratio

NPV (106 NRs)

1 Option A 1283 200.32 2,082 3.66 12.10% 1.17 32.49 2 Option B 996 160.24 2,145 3.04 14.26% 1.35 54.76 3 Option C 689 134.64 2,606 3.47 13.55% 1.29 37.91 4 Option D 599 123.63 2,752 3.50 13.59% 1.29 35.33 5 Option E 444 106.16 3,188 3.71 13.07% 1.25 25.75

Specific Energy Cost Vs Installed Capacity

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

1283 996 689 599 444

Installed Capacity in kW

Spec

ific

Ener

gy C

ost (

Rs.

/kW

h)

Fig 8.1: Variation of Specific Energy Cost with Installed Capacity



IRR (%) vs Installed Capacity (kW)

11.00%

11.50%

12.00%

12.50%

13.00%

13.50%

14.00%

14.50%

1283 996 689 599 444

Installed Capacity in kW

IRR

(%)

Fig 8.2: Variation of EIRR with Installed Capacity

B/C Ratio VS Intsalled Capacity (kW)

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1283 996 689 599 444


B/C

Rat

io

Fig 8.3: Variation of Benefit/Cost with Installed Capacity



NPV VS Installed Capacity (kW)

0.00

10.00

20.00

30.00

40.00

50.00

60.00

1283 996 689 599 444


NPV

in M

illio

n R

s.

Fig 8.4: Variation of Net Present Value with Installed Capacity

Cost Per kW VS Installed Capacity (kW)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1283 996 689 599 444


Cos

t per

kW

(US$

)

Fig 8.5: Variation of Cost per kW with Installed Capacity



8.6 Recommendation of Installed Capacity All the options show benefit cost ratio more than 1.0, internal rate of return more than 10% and a positive NPV. The analysis shows that the project is economically viable for all the options. With reference to the maximum net present value and specific energy cost, 40% exceedance flow option i-e Option B of 996 kW is recommended for the detailed study and construction. This option has the least cost per kW (US$ 2145). The EIRR, B/C ratio and NPV of this option are 14.25%, 1.35 and NRs 54.76 millions respectively.



9. PROJECT DESCRIPTION AND DESIGN 9.1 GENERAL The Teliya Khola Small Hydropower Project is ROR project on Teliya Khola. The main structures of the project are overflow weir, intake, gravel trap cum desanding basin, headrace canal, RCC crossing, penstock pipe, anchor blocks, saddle supports, powerhouse and tailrace conduit respectively. The feasibility study has concluded its installed capacity as 996 kW.

9.2 SITE CONDITION AND PROJECT SETTINGS The project site is stable and almost passes across the left bank of Teliya Khola for about 100 m length and a simple RCC crossing crosses Teliya. Simple structures are sufficient for controlling the flow at intake and naturally the intake site is very suitable and even during high floods the velocity of flow in weir site is stable. Though the high flood level is calculated to be about 3.94 m above normal water level , in actual this height does not extends above 2 m as per physical study of the site.

The length of weir is 30 m and the normal water level at weir is at an elevation of 763.00 m. The height of the overflow weir is 2.00 m. The flow to the desanding basin will be by intake and the flow inlet structure to headrace will be located at an right angle to weir axis. The desanding basin is located 16 m far from intake. Sediment larger than 0.2 mm settled at the desanding basin and flushed out. The size of desanding basin is 16 m x 3.8 m x 3.9 m and is located on the left bank of the Teliya Khola. A flushing channel is arranged at the end of the basin to clean out the deposited sediment as when required. The dimension of headrace canal is 1.2x1.0 m designed to carry the required discharge up to the forebay. The penstock pipe of variable thickness and 0.75 m internal diameter will carry the design discharge from forebay to all the way to the turbine for the power generation, installed in the powerhouse.

9.3 DESCRIPTION OF PROJECT CIVIL COMPONENTS

9.3.1 Headworks The headwork consists of about 30 long gravity type of overflow weir, intake, intake gate and 16 m long single chambered desanding basin with proper flushing arrangement and the 10 m long side spillway. The intake is capable of passing the discharge of 0.98 m3/s. The intake is provided with the trash rack, intake gate and stop log. The gravel trap cum desanding basin is located on the right bank of the Teliya Khola on the flat area 16 m after the approach canal. Head Work General Layout Plan is shown in drawing section in Volume II. Design calculation is given in the Annex E.



9.3.2 River Diversion Since the dry flow of the stream is only about 161 lps, the discharge of the stream can be by passed easily by temporary means and hence no permanent structures are proposed for river diversion during construction.

9.3.3 Overflow Weir The weir axis is located at Teliya Khola about 763.00 m and its length is 30 m. The weir is designed to pass the 1 in 100 year of flood 215 m3/s. The weir crest has been fixed at EL. 763.00 m to maintain the full supply level (FSL). The maximum height of the weir from the bottom of the foundation is 2.00 m. Apron of sufficient length has been provided at upstream and downstream of weir. Downstream of weir has been fixed at elevation of EL 761.00 m. The weir has been checked for stability against sliding and overturning during critical condition, creep length, bearing capacity.

The main features of the weir are listed below:

Design flood = 215 m3/s (1 in 100 year flood)

High flood level = 766.94 m

Level of weir crest = 763.00 m

More details are given in Annex E for design calculations.

9.3.4 Intake The flow in the canal will be controlled by single sluice gate proposed ahead of desanding basin. The velocity of low at intake is assumed to be 0.85 m. During the overflow as well the flow will be controlled by these gates. More details are given in the Annex for detail design calculation in Annex E.

9.3.5 Gravel Trap cum Desander In order to reduce the erosion of the guide vanes and runners of the turbines by suspended sediments, a desanding basin is required. The dimensions of the desanding basin depend on the characteristics of the river, the design discharge, and the particle size to be removed. The de-sander plan and cross section is shown in drawing section in volume II of this report. The design calculation is presented in Annex F.

Water shall preferably be supplied continuously to the plant during flushing of the settling basins in order to obtain a reliable power production during the monsoon. The maximum size of sediment particles that can be accepted in the flow is dependent on the characteristics of the turbines. Due to the uncertainty regarding the rating formulas for the suspended sediment, the trap



efficiency of 90 % of all particles with a fall diameter of 0.2 mm and the factor of safety of 65 % is considered to avoid damage of the turbines.

The desanding basin lies on the right bank of the Teliya Khola. The desanding basin is designed for the design discharge of 0.978 m3/s including 15 % for flushing purpose. The desanding basin is designed to trap 90% of the critical grain size of 0.2 mm diameter. The settling velocity for the critical grain size is 0.02 m/sec. The size of forebay tank is 18 m x 3.5 m and its active water depth is 3.2 m. This gives the flow through velocity of 0.12 m/sec. The basin will be 18 m long with an additional 7.7 m extra length for the inclined transition at the beginning and end.

A gate (1500 mm x 1500 mm) is provided at the end of the desander basin pool, which will control the water level in the desander basin, and this gate will also be used during the flushing of the desander basin. Then headrace canal of 1.2 m x 1.0 m passes for upto forebay. The flushing channel is provided at the end of the purging channel. The sections of the basin are shown in drawing section in volume II of this report. More details are given in the Annex F for detail design calculations.

9.3.6 Headrace Canal The length of headrace canal is 1616 m which excludes the length of gravel trap cum desanding basin. Headrace alignment passes across rocky land at left bank for upto 70 m length. It crosses Teliya khola at this chainage. Then it passes along kharbari for remaining length. The size of the canal is 1.20 m x 1.00 m. The canal would be constructed of 200 mm RCC (1:2:4). Technical details of canal are as following. Design discharge (Q) = 0.935 m3/s ( with 10% extra allocation) Longitudinal Slope of Canal = 1 in 520 Manning's Coefficient (n) = 0.015 Width of Canal (m) = 1.2 m Water Depth (m) =0.6 m Freeboard (m) =0.4 m

9.3.7 Forebay Forebay tank is located at a chainage of 1616 m from intake. Forebay tank is located at the sloppy ridge and cutting of sloppy land is proposed for the entire structural bed. The size of the tank is 18 m x 3.5 m x 3.2 m. In order to reduce the erosion of the guide vanes and runners of the turbines by suspended sediments and controlling the flow in penstock , a forebay basin is required. The dimensions of the forebay basin depends on the characteristics of the river, the design discharge, and the particle size to be removed. The tank is designed for the retention time of 3 minutes , the trap efficiency of 90% with a particle falling diameter of 0.2 mm and the factor safety of 65%.The forebay plan and cross section is shown in drawing section in Volume II. The overflow will be



passed to Chhak Khola from 150 m long spillway canal. More details about design is given in the Annex E for design calculation.

9.3.8 Penstock, Anchor Block and Saddle Support Total length of penstock pipe upto bifurcation point is 266 m. The optimum diameter is found to be 750 mm by the analysis of penstock cost versus lost of revue from head loss for different diameters. The thickness of bifurcation pipe will be 530 mm with thickness of 8 mm. The thickness of penstock varies from 5 mm to 8 mm. Table 9.1 : Description of penstock thickness, length and weight

S.N. Description of

work No Length (m)

Breadth (m)

Height/ Dep. (m)

Quantity kg. Unit Remarks

1 5 mm thick Pipe 1 50 103.4 5170

Unit Wt/m=103.4 kg

2 6 mm thick Pipe 1 80 123.2 9856

Unit Wt/m=123.2 kg

3 7 mm thick Pipe 1 50 144.1 7205

Unit Wt/m=144.1 kg

4 8 mm thick Pipe 1 86 165 14190

Unit Wt/m=165 kg

5

Bifurcation Pipe (530 mm dia.) 1 20 117.7 2354

Unit Wt/m=117.7 kg

Total Weight of Penstock Pipe 38775 A number of anchor blocks have been proposed to anchor the penstock pipe. Anchor blocks have been proposed for every horizontal and vertical bends. Total number of anchor blocks and support piers is 12 and 41 respectively. Support piers are placed at an average spacing of 5 m. Bothe anchor block and support piers would be constructed of PCC (1:3:6) with 40% plums. The bases of the structures would be constructed of PCC(1:2:4). More details are given in drawing section.

9.3.9 Powerhouse Complex The powerhouse will contain two units of 620 kW turbine/ generator units, associated electrical and mechanical equipment, a service bay and a control room. The powerhouse is surface type and is on the bank of Teliya Khola in paddy field. It contains two units of pelton turbines coupled with generators in horizontal axis with an installed capacity of 996 kW. The dimension of the powerhouse is 18.40 x 10.22 and the height is variable for equipment room and operator / office room. The Space of the powerhouse is designed for housing two generating unit of 620 kW, repair bay and workshop room. The powerhouse plan and sections are shown in drawing section in Volume II of this report.



9.4 POWER FACILITIES: MECHANICAL EQUIPMENT 9.4.1 Introduction The optimization study has shown that the optimal plant discharge capacity will be 0.85 m3/s and the total installed capacity will be 996 kW with a net head of 138.94 m. Additional investigations reveal that installation of two (2) number of power units is more economical and practical. Main reason behind this selection is the operational consideration. Although a single unit would reduce cost, higher number of units would increase energy generation capability compared to a single unit option in case a unit got damaged. Based on the available head and discharge, considering two units, horizontal shaft Pelton Turbine appears as the most feasible option. The powerhouse mechanical equipment comprises:

Turbines Governors Turbine inlet valve Cooling water system Drainage water and dewatering system Compressed air system Oil handling system Ventilation and air conditioning system Powerhouse crane Mechanical workshop equipments

9.4.2 General Design Criteria General design and performance specification for the mechanical equipments are as per the current standards issued by the International Electro-technical Commission (IEC). Turbines Both turbines are sized to operate at a design discharge and gross head of 0.425 m3/s and 138.94 m respectively, when the reservoir is at normal ope

Documents

Feasibility Study Report_Main Report_Teliya