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DEPARTMENT OF ENERGYENERGY UTILIZATION MANAGEMENT BUREAU

Manuals and Guidelines

for

Micro-hydropower Development

in Rural Electrification

Volume I

June 2009


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Through the Project on “Sustainability Improvement of Renewable EnergyDevelopment for Village Electrification in the Philippines” under technicalassistance of Japan International Cooperation Agency (JICA), this manual wasdeveloped by the Department of Energy (DOE) reviewing the “Manual for Micro-hydropower Development in March 2003.


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Manuals and Guidelinesfor

Micro-hydropower Development in Rural Electrification

Volume I

MHP-1 Manual for Design, Implementation and Managementfor Micro-hydropower

Volume II

MHP-2 Guideline for Selection of Potential Sites and Rehabilitation Sitesof Micro-hydropower

MHP-3 Project Evaluation Guideline for Micro-hydropower Development

MHP-4 Micro-hydropower Plant Site Completion Test Manual

MHP-5 Micro-hydropower Operator Training Manual

MHP-6 Training Manual for Micro-hydropower Technology


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１


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DEPARTMENT OF ENERGYENERGY UTILIZATION MANAGEMENT BUREAU

MANUAL

for

Design, Implementation and Management

For

Micro-hydropower Development

June 2009

MHP – 1


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Through the Project on “Sustainability Improvement of Renewable Energy

Development for Village Electrification in the Philippines” under technicalassistance of Japan International Cooperation Agency (JICA), this manual wasdeveloped by the Department of Energy (DOE) reviewing the “Manual for Micro-hydropower Development in March 2003.


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Manual for Micro-Hydro Power Development

Contents

- c-1 -


Table of Contents

EXECUTIVE SUMMARY

1 Background S-1

2 User of Manual S-1

3 Applicable Range of Micro-Hydropower S-1

4 How to use this Manual S-2

Chapter 1 INTRODUCTION 1-1

1.1 Purpose of the Manual for Micro-Hydro Development 1-1

1.2 Components of Micro-Hydro Power 1-2

1.3 Concept of Hydropower 1-5

1.4 The Water Cycle 1-7

Chapter 2 IDENTIFICATION OF THE POTENTIAL SITES 2-1

2.1 Basic Reference Materials 2-1

2.2 Radius of Site Identification 2-3

2.3 Calculation of River Flow 2-4

2.4 Identification of Potential Sites 2-5

2.4.1 Map Study 2-5

2.4.2 Identification Based on Local Information 2-6

2.4.3 Selection of Potential Development Sites 2-7

[Ref.2-1 Transmission and distribution line distance and voltage drop] 2-10

[Ref.2-2 Relationship between voltage drop and distribution line distance 2-11[Ref.2-3 Considerations in the indirect estimation of discharge at the project

site using data from gauging stations in the vicinity. 2-12

[Ref.2-4 Method of river flow calculation by water balance model of

drainage area] 2-14

[Ref.2-5 Example of Micro-hydro Development Scheme Using Natural

Topography and Various Man-made Structures] 2-21

Chapter 3 SITE RECONNAISSANCE 3-1


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3.1 Objective of Site Reconnaissance 3-1

3.2 Preparation for Site Reconnaissance 3-1

3.2.1 Information gathering and preparation 3-1

3.2.2 Planning of preliminary site reconnaissance 3-2

3.2.3 Necessary equipment for preliminary site reconnaissance 3-2

3.3 Survey for Outline the Project Site 3-3

3.4 Validation of Geological Conditions Affecting Stability

of Main Civil Structures 3-5

3.5 Survey on Locations of Civil Structures 3-6

3.6 Measurement of River Flow 3-7

3.7 Measurement of Head 3-9

3.8 Demand Survey 3-10

3.8.1 Demand survey 3-10

3.8.2 Factors to consider in the Demand survey items 3-10

3.9 Actual Field Survey 3-12

[Ref.3-1 Method of Stream Flow Measurement] 3-13

[Ref.3-2 Method of Head Measurement] 3-18

[Ref.3-3 Sample Form Sheet for Potential Site Survey] 3-22

[Ref.3-4 Questionnaire for households of non-electrified barangays] 3-26

Chapter 4 PLANNING 4-1

4.1 Scheme of Development Layout 4-1

4.2 Data and Reference to Consider for Planning 4-3

4.2.1 Hydrograph and Flow Duration Curve 4-3

4.2.2 Plant Factor and Load Factor 4-4

4.3 Selection of Locations for Main Civil Structures 4-64.3.1 Location of Intake 4-6

4.3.2 Headrace Route 4-8

4.3.3 Location of Head Tank 4-8

4.3.4 Penstock Route 4-9

4.3.5 Location of Powerhouse 4-12

4.3.6 Location of Tailrace 4-13

4.4 Supply and Demand Plan 4-14

4.4.1 Selection of Power Demand Facilities 4-14


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4.4.2 Scheme of Development based on Supply and Demand 4-15

4.4.3 Daily Supply and Demand Plan 4-22

Chapter 5 DESIGN FOR CIVIL STRUCTURES 5-1

5.1 Basic Equation for Civil Design 5-1

5.2 Intake Weir (Dam) 5-1

5.2.1 Types of Intake Weir 5-1

5.2.2 Weir Height Calculation 5-5

5.3 Intake 5-9

5.3.1 Types of Intake 5-9

5.3.2 Important Points for Intake Design (for Side-Intake) 5-12

5.4 Settling basin 5-14

5.5 Headrace 5-17

5.5.1 Types and Structures of Headrace 5-17

5.5.2 Determining the Cross Section and Longitudinal Slope 5-21

5.6 Headtank 5-24

5.6.1 Headtank Capacity 5-24

5.6.2 Important Points for Headtank Design 5-26

5.7 Penstock 5-30

5.7.1 Penstock Material 5-30

5.7.2 Calculation of Steel Pipe Thickness 5-30

5.7.3 Determining Diameter of Penstock 5-30

5.8 Foundation of Powerhouse 5-34

5.8.1 Foundation for Impulse Turbine 5-34

5.8.2 Foundation for Reaction Turbine 5-35

[Ref. 5-1 Simple Method for Determining the Cross Section] 5-37[Ref.5-2 Simple Method for Determining the Diameter of Penstock] 5-41

[Ref.5-3 Calculation of Head Loss] 5-42

Chapter 6 DESIGN FOR MECHANICAL AND ELECTRICAL STRUCTURES 6-1

6.1 Fundamental Equipment Components for Power Plant 6-1

6.2 Turbine (Water turbine) 6-5

6.2.1 Types and Output of Water Turbine 6-5

6.2.2 Specific Speed and Rotation Speed of Turbine 6-8


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6.2.3 Design of Crossflow Turbine 6-12

6.2.4 Design of Reverse Pump Type Turbine (Pump As Turbine) 6-13

6.3 Generator 6-14

6.3.1 Types of Generator 6-14

6.3.2 Output of Generator 6-16

6.3.3 Speed and Number of Poles of Generator 6-17

6.4 Power Transmission Facility (Speed Increaser) 6-19

6.5 Control Facility of Turbine and Generator 6-20

6.5.1 Speed Governor 6-20

6.5.2 Exciter of Generator 6-21

6.5.3 Single Line Diagram 6-23

6.6 Control, Instrumentation and Protection of Plant 6-24

6.6.1 Control Method of Plant 6-24

6.6.2 Instrumentation of Plant 6-24

6.6.3 Protection of Plant and 380/220V Distribution Line 6-25

6.6.4 Protection of 20kV Distribution Line 6-25

6.7 Inlet Valve 6-26

Annex 6.1 Brief Design of Cross Flow Turbine (SKAT T-12,13 & 14) 6-28

Annex 6.2 Brief Design of Reverse Pump Turbine (PAT) 6-33

Annex 6.3 Technical Application Sheet of Tender for

for Rural Electrification 6-46

Annex 6.4 Breif Design for Electro-mechanical Equipment of

Micro-hydropower Plant 6-49

Chapter 7 DESIGN OF DISTRIBUTION FACILITIES 7-1

7.1 Concept of Electricity 7-17.2 Selection for Distribution Route 7-3

7.3 Distribution Facilities 7-5

7.4 Pole 7-6

7.4.1 Span Length of Poles 7-6

7.4.2 Allowable Minimum Clearance of Conductors and Environment 7-7

7.4.3 Height of Poles 7-7

7.4.4 Size of Poles 7-8

7.5 Guy wire 7-9


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7.6 Conductors and Cables 7-12

7.6.1 Advantages/Disadvantages of Conductors and Cables 7-12

7.6.2 Sizes of Conductors 7-12

7.6.3 Allowable Sag of Conductors 7-12

7.6.4 Allowable Load per Phase 7-12

7.6.5 Application of 3-Phase Line 7-12

7.7 Distribution Transformers 7-13

7.7.1 Types of Distribution Transformer 7-13

7.7.2 Necessity of Transformers 7-14

7.7.3 Application of Distribution Transformers 7-15

7.7.4 Selection of Unit Capacity 7-15

7.7.5 Location 7-15

7.8 House Connection (HC) 7-16

7.8.1 Application of House Connection 7-16

7.8.2 In-house Wiring 7-17

[Ref.7-1 Standard of Steel poles] 7-18

[Ref.7-2 Construction of house connection crossing village road] 7-19

Chapter 8 PROJECT COST ESTIMATION 8-1

8.1 Rough Cost Estimation During Planning Stage 8-1

8.2 Cost Estimation During Detail Design Stage 8-3

8.2.1 Items 8-3

8.2.2 Quantity 8-5

8.2.3 Unit Cost 8-6

[ Ref. 8-1 Cross-sectional method to calculate quantity] 8-11

[Ref.8-2 Example of Bill of Quantities] 8-13

Chapter 9 CONSTRUCTION MANAGEMENT 9-1

9.1 Construction Management for Civil Facilities 9-1

9.1.1 Purpose 9-1

9.1.2 Progress Control 9-1

9.1.3 Dimension Control 9-2

9.1.4 Quality Control 9-3


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9.2 Construction Management for Turbine, Generator and

their Associated Equipment 9-5

9.2.1 Installation 9-5

9.2.2 Adjustment during Test Run Operation 9-6

Chapter 10 OPERATION AND MAINTENANCE 10-1

10.1 Introduction 10-1

10.2 Operation 10-2

10.2.1 Basic Operation 10-2

10.2.2 Operation in case of Emergency 10-4

10.2.3 Others 10-5

10.3 Maintenance 10-6

10.3.1 Daily Patrol 10-6

10.3.2 Periodic Inspection 10-8

10.3.3 Special Inspection 10-8

10.4 Recording 10-9

Chapter 11 MANAGEMENT 11-1

11.1 Establishment of Organization 11-1

11.2 Management System 11-1

11.3 Reporting and Monitoring 11-2

11.4 Decision-Making System 11-2

11.5 Accounting System 11-3

11.6 Roles and Responsibilities of BAPA 11-3

11.6.1 BAPA Officials 11-3

11.6.2 Consumers 11-511.6.3 Local Government Unit (LGU) 11-5

11.6.4 Department of Energy (DOE) 11-5

11.7 Training 11-5

11.8 Collection of Electricity Charges and Financial management 11-6

11.8.1 Tariff Setting 11-6

11.8.2 Tariff Collection 11-6

11.8.3 Financial Management 11-7


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Executive Summary

- S-1 -

EXECUTIVE SUMMARY

1. Background

The first micro-hydropower plant was constructed in the 1930’s in San Pablo City,

Laguna Province. Although the Philippines has more than 60-year history in

micro-hydro development, most of the micro-hydropower plants, particularly those that

are recently installed, are not operational or have some problems in their operation.

Some identified issues or problems are the results of insufficient site assessment, poor

quality of power plant facilities and electro-mechanical equipment, and inadequate

operation and maintenance. In order to provide solution to these issues, as well as to

ensure sustainable development, it is required to use a guide and/or manual for

micro-hydro development.

This manual was provided as a technical supplement of the “Guide on Micro-hydro

Development for Rural Electrification” which was developed under JICA Expert

Dispatch Program for Rural Electrification utilizing Micro-hydro Technology.

2. User of Manual

This manual is intended to assist prospective micro-hydropower developers/proponents

for rural electrification in the off-grid and/or isolated barangays, such as local

government units (LGU’s), cooperatives and NGOs. This manual mainly deals with

technical aspects of micro-hydropower technology to facilitate the community based

micro-hydro development.

3. Applicable Range of Micro-Hydropower

The selection of best turbines depends on the site characteristics, the dominant factor on

the selection process being the head available and the power required. Selection also

depends on the speed at which it is desired to run the generator or other device loading

the turbine. It should be considered that whether or not the turbine will be expected to

produce power under part-flow conditions, also play an important role in the selection.

In the micro-hydropower scheme, turbines could be classified and grouped according to

operating principle as shown in the table below.


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Executive Summary

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Table S.1 Classification and applicability range of turbines

HEAD (pressure)Turbine Type

High < 40 m. Medium 20-40 m. Low 5-20 m.

Impulse Pelton

Turgo

Crossflow(Banki)

TurgoPelton

Crossflow(Banki)

Reaction Francis

Pump-as-turbine (PAT)Kaplan

Propeller

Propeller

Kaplan

4. How to use this manual

This manual is composed of eleven (11) chapters in relation with the “Project Cycle of

Sustainable Rural Electrification by Utilizing Micro-Hydro Technology”.

The conduct of site assessment and investigation in the study for a proposed

micro-hydropower development are necessary to upgrade its level of accuracy. However,

high precision survey or detailed investigation for preliminary design during the

planning stage is not recommended due to practical and economic reasons. Thedevelopment scale of micro-hydro is small and the cost of survey work is relatively

high.

The stages of mini-hydropower development project cycle are as follows.

Project Planning Stage

Project Implementation Stage

Project Operation Stage

In the first stage of the project cycle, termed as the “Project Planning Stage, the major

activities are “Selection of Potential Sites”, “Site Reconnaissance”, “Planning of the

Potential Sites” and “Formulation of the Project Development Plan” in the target area

utilizing decentralized power generation. Several potential sites will be considered in

this stage in order to formulate the electrification plan for the whole target area. Chapter

3 through Chapter 4, Chapter 8-1 and Chapter 11 of this manual will comprise the

pre-implementation stage.


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Executive Summary

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Figure S.1 Flowchart of Micro-hydropower Development (DOE’s BEP Projects)

Community

Dept of Energy

/ Other Donors

Proponent

(LGUs/NGOs)

List of

unenergized

sites identified

for NRE

P r o j e c t

O p e r a t i on

S t a g e

P r o j e c t I m pl e m e n t a t i on S t a g e

P r o j e c t

P l anni n g S t a g e

Site Reconnaissance

Layout and Design

Mobilization

House wiring/Construction/ Installation

O & M Training

Monitoring and

Technical advice

for the Project

Management and O & M of the project

LGU/NGO requestRequest for

consultant

Data Analysis

Commissioning

Data Collection

Technical

Assistance, if

necessary

Technical

BAPA Formulation Approval

Proposal preparation

Periodic


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Executive Summary

- S-4 -

The second stage is the “Project Implementation Stage”. This stage covers the “Detail

Design” and “Construction” of the particular site. Chapter 5 through Chapter 9 of thismanual will be used in the project implementation stage.

The final stage is the “Project Operation Stage”. In this stage, “Operation and

Maintenance” and “Management” will be discussed. These activities are described in

Chapter 10 through Chapter 11 of this manual.

The descriptions in each chapter are follows,

Chapter 1 Introduction

Introduces the concept of the micro-hydropower.

Chapter 2 Selection of Potential Sites

Deals with the technical aspects for site selection on the topographical map and

local information.

Chapter 3 Site Reconnaissance

Provides procedural activities on how to conduct the survey on social condition

as well as technical aspects of the potential site that were revealed in the above

activities. In site reconnaissance, it is important to consider the possibility and

capacity of the power generation and the demand in the area concerned.

Chapter 4 Planning

Shows the technical aspects for the planning of the project as shown in Figure

S.2.

Chapter 5 Design of Civil Structures The main problem for the development of a small-scale hydropower plant is the

high upfront cost. In this chapter, various techniques were described to possibly

reduce the construction cost of civil structures.

Chapter 6 Design of Mechanical and Electrical Structures

Provides the technical aspects for Mechanical and Electrical Structures such as

Inlet valve, Turbine and Generator.


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Executive Summary

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Figure S.2 Flowchart for the Planning of the Project

Chapter 7 Design of Distribution Facilities

Provides the technical aspects to be considered for Distribution Facilities such as

a pole, cable, and transformer.

Chapter 8 Project Cost Estimate

Shows example and formula of cost estimate per item of work. It also shows

Identification of System Layout

(refer to 4.1)

Confirmation of Design Discharge

(refer to 4.2)

Selection of the Civil Structures Location

(refer to 4.3)

Confirmation of the Head

(refer to Ref.5-3)

Selection of Power Demand Facilities

(refer to 4.4.1)

Selection of the Generating SystemCrossflow Turbine Syst em or Pumps as T urbine Syst em

Examination of Demand and Supply Balance

(Refer to 4.4.2)

Reconnaissance on Potential Site Reconnaissance on Demand Site

Site Reconnaissance

(Refer to Chapter 3)

Unbalanced Unbalanced

Rough Estimation of the Project Cost

(Refer to 8.1)

Balanced

Project Implementation Stage

:There are the description in Chapter 4


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Executive Summary

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how to calculate quantity per work item.

Chapter 9 Construction Management Refers to the purpose of Construction Management. It also includes progress

control, dimension control and quality control.

Chapter 10 Operation and Maintenance

Shows the necessity of a manual for operation and maintenance and the

importance of daily and periodic inspection.

Chapter 11 Management

In this chapter, the importance of establishing an association in the barangay for

smooth performance in the management of the Micro-hydropower system was

clarified.


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Chapter 1

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Chapter 1 INTRODUCTION

1.1 Purpose of the Manual for Micro-Hydro Development

Usually, Micro-Hydroelectric Power, or Micro-Hydro, are used in the rural

electrification and does not necessarily supply electricity to the national grid. They are

utilized in isolated and off-grid barangays for decentralized electrification.

There is an increasing need in many developing countries for rural electrification

purposely to provide illumination at night and to support livelihood projects. Also, the

government is faced with the high costs of extending electricity grids. Often,

Micro-Hydro system offers an economical option or alternative to grid extension. The

high cost of transmission lines and the very low load factor in the rural areas contributes

to the non-viability of the grid extension scheme. On the contrary, Micro-Hydro

schemes can be designed and built by the local people and smaller organizations

following less strict regulations and using local technology like traditional irrigation

facilities or locally fabricated turbines. This approach is termed as the Localized

Approach. Fig 1.1.1 illustrates the significance of this approach in lowering the

development cost of Micro-Hydro systems. It is hoped that this Manual will help to

promote the Localized Approach.

Fig 1.1.1 Micro-Hydro’s Economy of Scale ( based on 1985 data)


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Chapter 1

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1.2 Components of Micro-Hydro Power

Figure1.2.1 shows the major components of a typical micro-hydro development scheme.

Fig. 1.2.1 Major components of a micro-hydro scheme

- Diversion Weir and Intake

The diversion weir – a barrier built across the river used to divert water through an

opening in the riverside (the ‘Intake’ opening) into a settling basin.

- Settling Basin

The settling basin is used to trap sand or suspended silt from the water before

entering the penstock. It may be built at the intake or at the forebay.

eadtank

eadrace


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Chapter 1

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- Headrace

A channel leading water to a forebay or turbine. The headrace follows the contour of

the hillside so as to preserve the elevation of the diverted water.

- Headtank

Pond at the top of a penstock or pipeline; serves as final settling basin, provides

submergence of penstock inlet and accommodation of trash rack and

overflow/spillway arrangement.


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Chapter 1

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- Penstock

A close conduit or pressure pipe for supplying water under pressure to a turbine.

- Water Turbine and Generator

A water turbine is a machine to directly convert the kinetic energy of the flowing

water into a useful rotational energy while a generator is a device used to convert

mechanical energy into electrical energy.

There are of course many variations on the design layout of the system. As an

example, the water is entered directly to the turbine from a channel without a

penstock. This type is the simplest method to get the waterpower. Another variation is

that the channel could be eliminated, and the penstock will run directly to the turbine.

Variations like this will depend on the characteristics of the particular site and the

requirements of the user of system.


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Chapter 1

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1.3 Concept of Hydro Power

A hydro scheme requires both water flow and a drop in height (referred to as ‘Head’) to produce useful power. The power conversion absorbs power in the form of head and

flow, and delivering power in the form of electricity or mechanical shaft power. No

power conversion system can deliver as much useful power as it absorbs –some power

is lost by the system itself in the form of friction, heating, noise, etc.

The power conversion equation is :

Power input = Power output + Loss

or Power output = Power input × Conversion Efficiency

The power input, or total power absorbed by the hydro scheme, is the gross power,

(Pgross). The power output is the net power (Pnet). The overall efficiency of the scheme

(Fig.1.3.2) is termed Eo.

Pnet = Pgross ×Eo in kW

The gross power is the product of the gross head (Hgross), the design flow (Q) and a

coefficient factor (g = 9.8), so the fundamental hydropower equation is:

Fig. 1.3.1 Head is the vertical height through which the water drops


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Chapter 1

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Pnet = g ×Hgross × Q ×Eo kW (g=9.8)

where the gross head is in meters and the design flow is in cubic meter per second. Eo is

derived as follows:

Eo = Ecivil work ×E penstock × Eturbine × Egenerator × Edrive system× Eline × Etransformer

Usually Ecivil work : 1.0 - (Channel length × 0.002 ～ 0.005)/ Hgross

E penstock : 0.90 ～ 0.95 (it’s depends on length)

Eturbine : 0.70 ～ 0.85 (it’s depends on the type of turbine)

Egenerator : 0.80 ～ 0.95 (it’s depends on the capacity of generator)

Edrive system : 0.97

Eline : 0.90 ～ 0.98 (it’s depends on the transmission length)

Etransformer : 0.98

Ecivil work and E penstock are usually computed as ‘Head Loss (Hloss)’. In this case, the

hydropower equation becomes:

Pnet= g ×(Hgross-Hloss) ×Q ×(Eo - Ecivil work - E penstock ) kW

This simple equation should be memorized: it is the heart and soul of hydro power

design work.

Fig 1.3.2 Typical system efficiencies for a scheme running at full design flow.





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Chapter 1

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1.4 The Water Cycle

The volume of the river flow or discharge depends on the catchment area and thevolume of rainfall. Figure 1.4.1 shows how the rainfall is divided on both sides (A and

B) of the watershed. For example, there is an existing Hydropower Plant at A-side, the

rainfall at B-side cannot be used for power generation at this Hydropower Plant.

Therefore, the catchment area of a proposed hydropower plant should be known at the

first step of the study of hydro scheme.

Fig 1.4.1 The hydrological cycle

The broken lines in Fig 1.4.2 indicate the watershed of Point-A and Point-B. The

catchment area is the area enclosed by broken lines.

Fig 1.4.2 The catchment area and the watershed


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Chapter 2

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Chapter 2 IDENTIFICATION OF POTENTIAL SITES

It is necessary to roughly examine (i) whether or not the construction of a small-scale

hydropower plant near the power demand area is feasible and (ii) how much power

capacity can be generated sufficiently and where, and then (iii) how to select a potential

site among the candidate sites.

The initial examination is basically a desk study using available reference materials and

information and the procedure involved and important issues to be addressed are

explained below.

2.1 Basic Reference Materials

The basic reference materials required are the following:

1) Topographical map: scale: 1/50,000

Topographical map provides important information, such as landform, location of

communities, slope of the river, catchment area of proposed sites, access road, etc.

In the Philippines, topographical maps of scale 1/50,000 are available at the

National Mapping & Resources Information Authority (NAMRIA)

2) Rainfall data: isohyetal map and others (cf. Fig 2.1.1)

Although it is unnecessary to gather detailed rainfall data at this stage, it is

necessary to have a clear understanding of the rainfall characteristics of the project

area using an isohyetal map for the region and existing rainfall data for the

adjacent area. Isohyetal map provides the interpolation and averaging will give an

approximate indication of rainfall.


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Chapter 2

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Figure 2.1.1 (a)

Fig 2.1.1(b) An example of isohyetal map for micro-hydro scheme


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Chapter 2

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2.2 Radius of Site Identification

As most of the electric energy generated by a small-scale hydropower plant is basically

intended for the consumption of the target area, it is important to consider that the plant

site should be as nearer as possible to the load center. In the case of highly dispersed

communities, which are distributed over a relatively large area, it may be more

advantageous to construct individual micro-hydropower plants, rather than to supply

power to all groups by a single plant, due to lower transmission cost, easier operation

and maintenance and fewer impacts due to unexpected plant stoppage, etc. To be more

efficient in planning individual-type micro-hydropower plants, it is recommended to

gradually widen the scope of the survey, starting from the geographical area of each

group.

The transmission distance from the potential site to the target site should depend on

various parameters, the power output, demand level, topography, accessibility

conditions, transmission voltage and cost of transmission lines. In Japan, the

transmission distance to the demand site is set to ensure a voltage drop rate which does

not exceed 7%. [Reference 2-1: Transmission and distribution line distance and voltage

drop]

In case of Micro-hydro Scheme in the Philippines, the rough estimate for the maximum

allowable transmission distance is 1.5 kilometers (km) from the load center. This

distance is based on the premise that the voltage at the end of distribution line should be

kept at not less than 205 volts (V) or the permissible voltage drop is only 15V on the

regulated voltage of 220V, without using a transformer. [Reference 2-2 Relationship

between voltage drop and distribution line distance]

If a good potential site is not found within the above distance, the radius ofidentification should be expanded over a larger area with the provision that the

transformer should be installed.


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Chapter 2

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2.3 Calculation of River Flow

Among the river flow data mentioned earlier, historical records of flow data in thearea surrounding the project site should be used to estimate the river flow, taking the

rainfall distribution characteristics into consideration.

Qp = Rr ×Qo／Ao

Where,

Qp : river flow per unit catchment area in project area (m3/s／km2)

Rr : rainfall ratio between catchment area of the proposed site for micro-hydro

project and of existing gauging station

Qo : observed river flow at existing gauging station or existing hydro-power station

(m3/s)

Ao : catchment area of existing gauging station (km2)

[See Reference 2-3: Considerations when estimating river flow at the project site

(indirectly from existing data of vicinity gauging stations) for the important points to

note for river flow based on the existing gauging station nearby.]

Particularly in the micro-hydro scheme, it is important to note that the firm discharge,

which is the flow during the driest time of the year, should be estimated accurately.

If no flow data is available, it is possible to estimate the rough flow duration curve

referring to “Reference 2-3: Simple calculating method of river flow by the water

balance model of drainage area”.


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Chapter 2

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2.4 Identification of Potential Sites

2.4.1 Map Study

Potential sites are identified on the topographical map with a scale of 1/50,000 by

interpreting the head.

The following parameters should be considered in the map study:

(1) Site identification considering river gradient and catchment area

Sites with high head, shortest waterway and high discharge level are naturally

advantageous for hydropower generation.

The information on the river gradient (elevation difference and river length) and the

drainage area could be obtained in the map study. While some experience is required to

identify potential sites from a topographical map, if the diagrams shown Fig 2.4.1 are

prepared in advance for the subject river, the identification of potential sites is much

easier.

(2) Identification based on waterway construction conditions

As far as the basic layout of a micro-hydro scheme is concerned, most civil structures

are planned to have an exposed structure. Because of this, the topography at any

potential site must be able to accommodate such exposed civil structures. (Refer to

Chapter 4, 4.1 System Layout )


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Chapter 2

- 2-6 -

Fig 2.4.1 River Profile and Changes in Drainage Area of River to consider in the

Identification of Promising Sites for Hydropower Development

2.4.2 Identification Based on Local Information

In cases where potential sites cannot be interpreted on the topographical map because of

the small usable head or the presence of a fall or pool, etc. as well as existing

infrastructures like intake facilities for irrigation and forest roads, potential sites areidentified on the basis of information provided by a local public body and/or local

residents’ organization. [Reference 2-5: Example of Natural Topography and Various

Infrastructures]

Confluence

Suitable section for power

E l e v a t i o n

C a t c h m e n t A r e a

River

Change in Catchment Area

Distance


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Chapter 2

- 2-7 -

2.4.3 Selection of Potential Development Sites

The potential sites identified in the previously described study are then examined fortheir suitability in hydropower development.

(1) Level of firm discharge

While it is difficult to judge the suitability for development based on the absolute

volume of firm discharge, a potential site with a relatively high level of firm discharge

is more favourable site for a micro-hydro plant designed to supply power throughout the

year.

Figure 2.4.2 shows the relation of specific firm discharge and the ratio of firm discharge

to maximum discharge (Qmax/QF: refer to the figure below) in existing small-scale

hydropower plants. Generally, the Qmax/QF values of micro hydropower plant for rural

electrification are shown about 1.0. This is meaning that the maximum discharges of

micro hydropower plants are the same as the firm discharge. This is because constant

electric power through a year is required to the micro hydropower plant for the rural

electrification program. And the specific firm discharge in the Qmax/QF range are

0.8~2.0 m3/s／100km2. The difference of vegetation of the catchment area and the

annual precipitation cause this difference. For the initial identification of potential site,

the maximum discharge/firm discharge will be set as 1.0 m3/s／100km2 . However,

the discharge set up in here should be reviewed at the time of site reconnaissance.

Qmax

Duration Curve

QF R i v e r f l o w

( m 3

/ s

)

Days


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Chapter 2

- 2-8 -

Fig 2.4.2 Relationship between firm discharge/maximum discharge ratio

and specific firm discharge

(2) L/H [ratio between waterway length (L) and total head (H)]

A site with a smaller L/H value is more advantageous for small-scale hydropower.

Figure 2.4.3 shows the relation of the ratio between the total head (H) and the waterway

length (L) (L/H) among existing small-scale hydropower sites where the total head is

not less than 10 m (the minimum head which can be interpreted on an existingtopographical map). As clearly indicated in the figure, the L/H of existing sites is

generally not higher than 40 or is an average of 25.

Figure 2.4.4 shows the relation of firm discharge and L/H, the sites with smaller firm

discharge has smaller L/H. The L/H of sites with less than 0.2m3/s firm discharge is

approximately below 15.

Maximum and Firm Discharge in Hydropower Plant

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

0 10 20 30 40 50 60 70 80 90 100 110

Percentage of Firm/Maximum Discharge (%)

U n i t F i r m D

i s c h a r g e

( m 3

/ s / 1 0 0 k m

2 )

Large

SmallMini

Micro


34/268


Chapter 2

- 2-9 -

Fig2.4.3 Relation between head and waterway length

Fig2.4.4 Relation between firm discharge and L/H

0

0.1

0.2

0.3

0.4

0.5

0 10 20 30 40 50

Waterway length / Head

F i r m

d i s c h a

r e

( m 3 / s )

Head and Waterway Length

0

10

20

30

40

50

60

70

80

90

100

0 2 00 4 00 6 00 8 00 1 00 0 12 00 1 40 0 16 00 1 80 0 20 00 2 20 0 24 00 2 60 0 28 00 3 00 0

Waterway Length (m) L

H e a d ( m ) H

Micro L/H


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Chapter 2 (Reference)

- 2-10 -

[Ref. 2-1 Relationship between transmission line distance and voltage drop]

P e r m

i s s i b l e v o l t a g e d r o p

r a t i o

Voltage drop ratio (%)


P e r m i s s i b l e v o l t a g e

d r o p r a t i o

D i s t a n c e ( k m )

D i s t a n c e ( k m )

R

e l a t i o n o f t r a n s m i s s i o n l i n e

d i s t a n c e a n d v o l t a g e d r o p I

1

1 k V ,

3 0 0 k W

A l u m i n u m C o n d u c t o r

R e l a t i o n o f t r a n s m i s s i o n l i n e

d i s

t a n c e a n d v o l t a g e d r o p I I

6 . 6 k

V ,

3 0 0 k W


D i a m e t e r o f l i n e



36/268



- 2-11 -

[Ref. 2-2 Relationship between distribution line distance and voltage drop]

D i s t a n c e ( m )


P e r m i s s i b l e v o l t a

g e

d r o p r a t i o

R

e l a t i o n o f t r a n s m i s s i o n l i n e

d

i s t a n c e a n d v o l t a g e d r o p I I I

4

0 0 V ,

5 0 k W




37/268



- 2-12 -

Ref. 2-3 Considerations in the estimation of discharge at the project site using data from gauging stations in the

vicinity.

If there are multiple gauging stations near the project site, the following parameters should be considered in

selecting the gauging station to be used.

1. Drainage Area Ratio

In estimating the discharge based on data of existing gauging stations, the drainage area should be taken into

consideration. From the discharge characteristic curve, as shown in the following figure, and drainage area

ratio between existing gauging station and project site is large, the flow duration curves may be crossing

each other which will make the discharge computation is unreliable.

2. Rainfall

The flow-duration and the rainfall characteristic in the upper portion of the river that has close correlation

with the long term discharge must be regarded as close correlation between rainfall and discharge. The

available rainfall data from gauging stations in both small and large drainage areas are useful information to

evaluate the discharge at the project site.

The simplest method in estimating the rainfall around the project site is to use the isohyetal maps. This map

shows contour lines of average rainfall, and can be compared to the amount of rainfall in the project site and

the gauging station.

Large drainage area

Day

S p e c i f i c d r a i n a g e a r e a

Small drainage area

Big amount of rainfall

Small amount of rainfall

Day



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- 2-13 -

3. Geological conditions

The evaluation of the discharge in the project site based on the presence of gauging stations in the area is not

enough to establish the correlation of flow duration curves. Geological condition also influenced the

similarity of flow duration curves aside from the drainage areas such as the existence of quaternary volcanic

rock area.

A quaternary volcanic rock is considered to have high water retention capability. Flow duration curves

influenced by this type of geology is relatively flat, wherein the discharge in wet season is only slightly

higher during the dry season, as compared with the flow duration curves of those that are not influenced by

this type of rocks, as shown in the figure below:

It is possible to know the distribution of quaternary volcanic rocks from existing geological map, however, it

is difficult to analyze quantitatively its share in the drainage area and the characteristic or general pattern of

discharge. Therefore, when quaternary volcanic rocks in the project area exists, it is recommended to select

gauging stations with equivalent geological characteristic.

Aside from the quaternary volcanic rock, limestone also affects the runoff and the river discharge. It is also

very difficult to measure its influence qualitatively and quantitatively. Generally the river with limestone

shows irregular discharge. Therefore, in case the drainage or catchment area is characterized with limestone

formation, it is suggested to conduct the stream flow measurement at the intake point of the project site.

4. Geographical condition

Geographical condition is also considered to have a significant influence in the estimation of discharge.

Generally, it is recognized that the amount of rainfall is larger at higher altitude and steeper mountain. Hence,

selection of gauging stations with similar geographical conditions, such as altitude, features, and direction of

drainage area is considered as one of the methods that raise the accuracy of discharge estimation.

In case no dissecting plain exist in the drainage area of the project site and its outline falls down, the runoff

may flow out of the drainage area through seepage.

Existence of Quaternaryvolcanic rock in the

drainage area

Day


Not existence ofQuaternary volcanic rock


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- 2-14 -

[Ref. 2-4 Method of river flow by the water balance model of drainage area]

If there are no discharge observation data and only rainfall data is available, it is possible to estimate river

discharge from the water balance data of the drainage area.

1.

Calculation method

(1) Water balance of the drainage area

The relation of rainfall, runoff (direct runoff, base runoff), and evaporation is indicated by the viewpoint of

annual water balance as shown in the formula below. In this case, pooling of drainage area and inflow and

runoff from/to other drainage area are not necessary.

P = R + Et

= Rd + Rb + Et

where,

P : Annual rainfall (mm)

R : Annual runoff (mm)

Rd : Annual direct runoff (mm)

Rb : Annual base runoff (mm)

Et : Annual evaporation (mm)

Runoff (R) is obtained from calculated evaporation (Et) by the presumption formula and observed rainfall

(P).

A pattern figure of the relation of rainfall (R), possible evaporation (Etp), and real evaporation (Et) is shown

Figure 1-1. Indicated as diagonal line is real evaporation, and area above line b-c is river runoff including

sub-surface water. Possible evaporation (a-b-c-d) is obtained by presumption formula.

(2) Direct runoff and base runoff

A pattern of annual runoff is shown Figure 1-2. The runoff is provided from sub-surface water, and it

contained base runoff with less seasonal fluctuation and direct runoff wherein the rainfall immediately

becomes the runoff. The ratio of sub-surface water to annual runoff (R) is shown in Table 1-1. Where, Rg = Rb,

Rb / R = 0.25 constant, and the base runoff is taken as constant.


40/268



- 2-15 -

Figure 1-1 Pattern figure of amount of rainfall and evaporation

Figure 1-2 Pattern figure of runoff

Amount of rainfall

Amount of realevaporation (Et)

Possible evaporation(Etp)

Runoff (R)

A m o u n t o f r a i n f a l l , e v a p o r a t i o n ( m m )

Month

A m o u n

t o f r u n o f f ( m 3 / s )

Month

Amount of direct runoff

Amount of base runoff


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- 2-16 -

Table 1-1 World water balance model

(Note) Source: Lvovich 1973

Data of Japan from Ministry of Land, Infrastructure and Transport

(3) Calculation of possible evaporation

The calculation formulas are Blaney-Criddle formula, Penman formula, and Thornthwaite formula etc. Herein,

Blaney-Criddle formula was used which is the simplest method using the longitude and temperature of the

project site. The observed value of evaporation from free water surface was also considered.

(a) Calculation method

① Blaney-Criddle formula

where,

u : Monthly evaporation (mm)

K : Monthly coefficient of vegetation

P : Monthly rate of annual sunshine (%)

t : Monthly average temperature (℃)

② Monthly average temperature and monthly rate of annual sunshine

・Monthly average temperature ; Using temperature at the drainage area of dam site

・Monthly rate of annual sunshine ; Obtained by the latitude at the drainage area of dam site

In the northern hemisphere, use Table 1-2, and in the southern hemisphere, use Table 1-3.

③ K value depends on the vegetation condition. Herein, a constant of 0.6 was used.

(b) Example of calculation

① Conditions : Position of drainage area lat. 16 ゚N

② Calculation of possible evaporation : Table 1-4

u = K ・P・ 100

( 45.7t + 813 )

Area Asia Africa North America South America Europe Australia JapanRainfall(P) 726 686 670 1648 734 736 1788Runoff

(R) 293 139 287 583 319 226 1197 Direct runoff (Rd) 217 91 203 373 210 172 - Subsoilwater 76 48 84 210 109 54 -Evaporation(Et) 433 547 383 1065 415 510 597

Rg / R 26 35 32 36 34 24 -


42/268



- 2-17 -

(4) Calculation of evaporation

It is shown in Table 1-4, the monthly evaporations are obtained by lower value of rainfall or possible

evaporation.

(5) Computation of monthly runoff data

a) Computation by the procedure shown in Table 1-5.

b) Derivation of the monthly mean discharge data at the dam site by the following formula.

where,

Q (i) : Monthly mean discharge at dam site in ‘i (month)’ (m3/s)

CA : Drainage area (km2)

n : Number of days in the month

The discharge for the drainage area of 300 km2 is shown in Table 1-5.

In addition, the ratio of the base runoff to the total runoff (25%) and the monthly distribution of base

runoff (constant) can be analyzed with regards to the characteristic of runoff at the area.

Q (i) = ×CA×106×

1000 86,400×n

Monthly runoff (④of Table 1-5 ) 1


43/268



- 2-18 -

Table 1-2 Monthly rate of annual sunshine (Northern Hemisphere) (%)

North Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.Latitude

65 3.52 5.13 7.96 9.97 12.72 14.15 13.59 11.18 8.55 6.53 4.08 2.62

64 3.81 5.27 8.00 9.92 12.50 13.63 13.26 11.08 8.56 6.63 4.32 3.0263 4.07 5.39 8.04 9.86 12.29 13.24 12.97 10.97 8.56 6.73 4.52 3.3662 4.31 5.49 8.07 9.80 12.11 12.92 12.73 10.87 8.55 6.80 4.70 3.6561 4.51 5.58 8.09 9.74 11.94 12.66 12.51 10.77 8.55 6.88 4.86 3.91

60 4.70 5.67 8.11 9.69 11.78 12.41 12.31 10.68 8.54 6.95 5.02 4.1459 4.86 5.76 8.13 9.64 11.64 12.19 12.13 10.60 8.53 7.00 5.17 4.3558 5.02 5.84 8.14 9.59 11.50 12.00 11.96 10.52 8.53 7.06 5.30 4.5457 5.17 5.91 8.15 9.53 11.38 11.83 11.81 10.44 8.52 7.13 5.42 4.7156 5.31 5.98 8.17 9.48 11.26 11.68 11.67 10.36 8.52 7.18 5.52 4.87

55 5.44 6.04 8.18 9.44 11.15 11.53 11.54 10.29 8.51 7.23 5.63 5.0254 5.56 6.10 8.19 9.40 11.04 11.39 11.42 10.22 8.50 7.28 5.74 5.1653 5.68 6.16 8.20 9.36 10.94 11.26 11.30 10.16 8.49 7.32 5.83 5.3052 5.79 6.22 8.21 9.32 10.85 11.14 11.19 10.10 8.48 7.36 5.92 5.4251 5.89 6.27 8.23 9.28 10.76 11.02 11.09 10.05 8.47 7.40 6.00 5.54

50 5.99 6.32 8.24 9.24 10.68 10.92 10.99 9.99 8.46 7.44 6.08 5.6548 6.17 6.41 8.26 9.17 10.52 10.72 10.81 9.89 8.45 7.51 6.24 5.8546 6.33 6.50 8.28 9.11 10.38 10.53 10.65 9.79 8.43 7.58 6.37 6.0544 6.48 6.57 8.29 9.05 10.25 10.39 10.49 9.71 8.41 7.64 6.50 6.2242 6.61 6.65 8.30 8.99 10.13 10.24 10.35 9.62 8.40 7.70 6.62 6.39

40 6.75 6.72 8.32 8.93 10.01 10.09 10.22 9.55 8.39 7.75 6.73 6.5438 6.87 6.79 8.33 8.89 9.90 9.96 10.11 9.47 8.37 7.80 6.83 6.6836 6.98 6.85 8.35 8.85 9.80 9.82 9.99 9.41 8.36 7.85 6.93 6.8134 7.10 6.91 8.35 8.80 9.71 9.71 9.88 9.34 8.35 7.90 7.02 6.93

32 7.20 6.97 8.36 8.75 9.62 9.60 9.77 9.28 8.34 7.95 7.11 7.05

30 7.31 7.02 8.37 8.71 9.54 9.49 9.67 9.21 8.33 7.99 7.20 7.1628 7.40 7.07 8.37 8.67 9.46 9.39 9.58 9.17 8.32 8.02 7.28 7.2726 7.49 7.12 8.38 8.64 9.37 9.29 9.49 9.11 8.32 8.06 7.36 7.3724 7.58 7.16 8.39 8.60 9.30 9.19 9.40 9.06 8.31 8.10 7.44 7.4722 7.67 7.21 8.40 8.56 9.22 9.11 9.32 9.01 8.30 8.13 7.51 7.56

20 7.75 7.26 8.41 8.53 9.15 9.02 9.24 8.95 8.29 8.17 7.58 7.6518 7.83 7.31 8.41 8.50 9.08 8.93 9.16 8.90 8.29 8.20 7.65 7.7416 7.91 7.35 8.42 8.47 9.01 8.85 9.08 8.85 8.28 8.23 7.72 7.8314 7.98 7.39 8.43 8.43 8.94 8.77 9.00 8.80 8.27 8.27 7.79 7.9312 8.06 7.43 8.44 8.40 8.87 8.69 8.92 8.76 8.26 8.31 7.85 8.01

10 8.14 7.47 8.45 8.37 8.81 8.61 8.85 8.71 8.25 8.34 7.91 8.098 8.21 7.51 8.45 8.34 8.74 8.53 8.78 8.66 8.25 8.37 7.98 8.186 8.28 7.55 8.46 8.31 8.68 8.45 8.71 8.62 8.24 8.40 8.04 8.264 8.36 7.59 8.47 8.28 8.62 8.37 8.64 8.58 8.23 8.43 8.10 8.342 8.43 7.63 8.49 8.25 8.55 8.29 8.57 8.53 8.22 8.46 8.16 8.42

0 8.50 7.67 8.49 8.22 8.49 8.22 8.50 8.49 8.21 8.49 8.22 8.50


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- 2-19 -

Table 1-3 Monthly rate of annual sunshine (Southern Hemisphere) (%)

(Note) Southern part more than lat. 50°S will be calculated using example from Table 1-2. Concretely,

the monthly rate of southern latitude is corresponding to below showing months of northern

latitude.

Southern lat. - Northern lat. Southern lat. - Northern lat.

January - July July - January

February - August August - February

March - September September - March

April - October October - April

May - November November - May

June - December December - June

South Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.Latitude

0 8.50 7.67 8.49 8.22 8.49 8.22 8.50 8.49 8.21 8.49 8.22 8.50

2 8.55 7.71 8.49 8.19 8.44 8.17 8.43 8.44 8.20 8.52 8.27 8.554 8.64 7.76 8.50 8.17 8.39 8.08 8.20 8.41 8.19 8.56 8.33 8.656 8.71 7.81 8.50 8.12 8.30 8.00 8.19 8.37 8.18 8.59 8.38 8.748 8.79 7.84 8.51 8.11 8.24 7.91 8.13 8.12 8.18 8.62 8.47 8.84

10 8.85 7.86 8.52 8.09 8.18 7.84 8.11 8.28 8.18 8.65 8.52 8.9012 8.91 7.91 8.53 8.06 8.15 7.79 8.08 8.23 8.17 8.67 8.58 8.9514 8.97 7.97 8.54 8.03 8.07 7.70 7.08 8.19 8.16 8.69 8.65 9.0116 9.09 8.02 8.56 7.98 7.96 7.57 7.94 8.14 8.14 8.78 8.72 9.1718 9.18 8.06 8.57 7.93 7.89 7.50 7.88 8.10 8.14 8.80 8.80 9.24

20 9.25 8.09 8.58 7.92 7.83 7.41 7.73 8.05 8.13 8.83 8.85 9.3222 9.36 8.12 8.58 7.89 7.74 7.30 7.76 8.00 8.13 8.86 8.90 9.3824 9.44 8.17 8.59 7.87 7.65 7.24 7.68 7.95 8.12 8.89 8.96 9.4726 9.52 8.28 8.60 7.81 7.56 7.07 7.49 7.90 8.11 8.94 9.10 9.6128 9.61 8.31 8.61 7.79 7.49 6.99 7.40 7.85 8.10 8.97 9.19 9.74

30 9.69 8.33 8.63 7.75 7.43 6.94 7.30 7.80 8.09 9.00 9.24 9.8032 9.76 8.36 8.64 7.70 7.34 6.85 7.20 7.73 8.08 9.04 9.31 9.8734 9.88 8.41 8.65 7.68 7.25 6.73 7.10 7.69 8.06 9.07 9.38 9.9936 10.06 8.53 8.67 7.61 7.16 6.59 6.99 7.59 8.06 9.15 9.51 10.2138 10.14 8.61 8.68 7.59 7.07 6.46 6.87 7.51 8.05 9.19 9.60 10.34

40 10.24 8.65 8.70 7.54 6.96 6.33 6.73 7.46 8.04 9.23 9.69 10.4242 10.39 8.72 8.71 7.49 6.85 6.20 6.60 7.39 8.01 9.27 9.79 10.5744 10.52 8.81 8.72 7.44 6.73 6.04 6.45 7.30 8.00 9.34 9.91 10.7246 10.68 8.88 8.73 7.39 6.61 5.87 6.30 7.21 7.98 9.41 10.03 10.90

48 10.85 8.98 8.76 7.32 6.45 5.69 6.13 7.12 7.96 9.47 10.17 11.09

50 11.03 9.06 8.77 7.25 6.31 5.48 5.98 7.03 7.95 9.53 10.32 11.30


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- 2-20 -

Table 1-4 Calculation example of possible evaporation and real evaporation

(Note) ①: obtained data ②: from Table 1-2 ③: parenthetic numbers are observed evaporation value

from water surface

Table 1-5 Calculation example of river flow

(Note) ③Base runoff: distribute uniformity 434.3×0.25 = 108.6 mm to each month

①Temperature ②Monthly rate of annual sunshine

④Rainfall ⑤Realevaporation

Month t psmaller valueof ③ and ④

(℃) (%) (mm) (mm)

Jan. 22.1 7.91 86.4 ( 91.0 ) 8.5 8.5Feb. 24.7 7.35 85.6 ( 106.4 ) 16.8 16.8Mar. 27.2 8.42 103.8 ( 129.7 ) 38.3 38.3Apr. 28.9 8.47 108.4 ( 138.2 ) 62.3 62.3May 28.4 9.01 114.2 ( 116.3 ) 170.0 114.2Jun. 27.7 8.85 110.4 ( 91.1 ) 180.3 110.4Jul. 27.1 9.08 111.8 ( 81.2 ) 202.9 111.8Aug. 27.0 8.85 108.7 ( 72.7 ) 197.7 108.7Sep. 27.1 8.28 101.9 ( 74.6 ) 207.7 101.9Oct. 26.5 8.23 100.0 ( 79.7 ) 123.0 100.0Nov. 24.1 7.72 88.6 ( 73.4 ) 30.2 30.2Dec. 22.0 7.83 85.4 ( 80.2 ) 17.9 17.9

Total 1,205.2 ( 1,134.5 ) 1,255.6 821.0

③Possible evaporation

from Blaney-Criddleformula

(mm)

①Runoff ②Direct runoff ③Base runoff ④Monthly runoff

Month④-⑤of Chart 1-4 ①×0.75 (Note) ②+③

(mm) (mm) (mm) (mm) (m3/s)

Jan. 0 0 9.2 9.2 1.03Feb. 0 0 8.3 8.3 1.03Mar. 0 0 9.2 9.2 1.03Apr. 0 0 8.9 8.9 1.03May 55.8 41.9 9.2 51.1 5.72Jun. 69.6 52.2 8.9 61.1 7.07Jul. 91.1 68.3 9.2 77.5 8.69Aug. 89.0 66.8 9.2 76.0 8.51Sep. 105.8 79.4 8.9 88.3 10.22Oct. 23.0 17.3 9.2 26.5 2.96

Nov. 0 0 8.9 8.9 1.03Dec. 0 0 9.2 9.2 1.03

Total 434.3 325.7 108.6 434.3

Monthlymean

discharge


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- 2-21 -

[Ref. 2-5 Example of Micro-hydro Development Scheme Using Natural Topography and Various Man-Made

Structures]

1. Using existing irrigation channel and naturally formed pool downstream of fall

River

Headrace

River

Power house

PenstockSpillway

Irrigation channelHeadtank

Screen

Intake weir

Water fall


47/268



- 2-22 -

2. Intake water from two rivers

Ⅱ-2-5入る

Headrace

Intake weir

River

Intake weir

Headtank

Screen

Penstock

Power house

Tailrace

River


48/268



- 2-23 -

3. Using a head drop structure of existing irrigation channel

Ⅱ-2-6入るIntake

Headtank

Irrigationchannel

Head dropstructure

Penstock

Power house


49/268



- 2-24 -

4. Using a head drop structure of existing irrigation channel

Ⅱ-2-7入る

River

Intake

Headrace

RoadIrrigation

channel

Headtank

Penstock

Power house

Tailrace


50/268


Chapter 3

- 3-1 -

CHAPTER 3 SITE RECONNAISSANCE

3.1 Objective of Site Reconnaissance

The objective of site reconnaissance for micro-hydro is to investigate potential sites and

supply area in order to evaluate the feasibility of projects and get information for

electrification planning. One of the most important activities in site reconnaissance is to

measure water discharge and head that could be utilized for micro-hydropower

generation. Investigations of intake site, waterway route, powerhouse site and

transmission route etc. are also conducted to assess the feasibility of project sites.

Power demand survey is also important in the planning of the electrification system.

Socio-economic data such as number of households and public facilities in supply area,

availability of local industries which will use electricity, solvency of local people for

electricity and the acceptability of local people to the electrification scheme are

gathered during the reconnaissance survey.

3.2 Preparation for Site Reconnaissance

To achieve effective and fruitful site reconnaissance, it is important to prepare for site

reconnaissance such as gathering of available information, devise sufficient plan and

schedule of survey activities in advance.

3.2.1 Information gathering and preparation

As advance information, 1/50,000 topographic maps are prepared to check thetopography of the target site and villages, the catchment area, village’s distribution and

access road. More accurate information on site accessibility could be collected by

contacting local people concerned.

Copies of 1/50,000 topographic maps and route maps enlarged by 200 to 400% are

prepared for the fieldwork.

Check list and interview sheet are also prepared for each site reconnaissance.


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Chapter 3

- 3-2 -

3.2.2 Planning of preliminary site reconnaissance

Although it may be required to deviate from original plan and schedule in accordancewith site condition, it is important to make sufficient plan and schedule for site

reconnaissance activities in advance. It is also necessary to coordinate with local

officials concerned to insure safety and successful conduct of the reconnaissance

activities. Since most of micro-hydro sites are located in mountainous and isolated areas,

it requires longer time to conduct site reconnaissance activities. Therefore, sufficient

schedule should be considered to have enough time for the fieldwork. Also,

measurement and other activities for site reconnaissance should be taken into account. A

check list or interview sheet should be prepared beforehand to efficiently perform

necessary activities of site reconnaissance.

3.2.3 Necessary equipment for preliminary site reconnaissance

Necessary equipment for preliminary site reconnaissance depends on purpose and

accuracy and site condition. Basic equipment is as follows:

Table 3.2.1 Check sheet of basic equipment for site reconnaissance as an example

Equipment Equipment

○ Route map ○ Altimeter

○ Topographic map ○ GPS (portable type)

○ Reconnaissance schedule ○ Camera, Film

○ Check list ○ Current meter

○ Interview sheet ○ Distance meter, measuring tape

Geological map ○ Hand level

Aerial photograph ○ Convex scale (2-3m)

Related reports Hammer

M a p ,

S h e e t

Clinometer

○ Field notebook Knife○ Scale Scoop

○ Pencil ○ Torch, Flashlight

○ Eraser Sampling baggage

○ Color pencil Label

Section paper ○ Compass

Stop watch

S t a t i o n a r y

E q u i p m e n t

Battery

Notes: ○: necessary equipment for preliminary site reconnaissance


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3.3 Survey to Outline the Project Site

During the reconnaissance at the proposed site of power generating facilities and aroundthe power demand area, a survey is conducted on the following items:

(1) Access conditions

The equipment and machinery used for the construction and operation of a micro-

hydropower plant are smaller and lighter than those used for an ordinary hydropower

plant and it may be possible in some cases that such equipment and machinery can be

brought to the site either manually or using simple vehicles.

Given the smaller capacity of the power generated by a micro-hydropower plant, careful

consideration is required in the use of transportation method and access other than the

use of an existing road or vehicle since the construction of a new access road could be a

factor that would considerably reduces the economy of a project. In the case of a

mountainous area, there may be an abandoned road (previously used for the hauling of

cut trees, etc.) which is difficult to find because it has been covered by vegetation and it

is important to interview local residents on the existence of such a road.

(2) Situation of existing system and future plan

Even for a project site in which the development of an individual system is assumed, a

survey should be conducted on the tail end location, route and voltage, etc. of the

existing system and also on the availability of extension and rehabilitation plans for the

said system.

(3) Situation of river water utilization

The existence of facilities utilizing the river flow, the flow volume and any relevant

future plans regarding the river from which a planned micro-hydropower plant will

draw water should also be surveyed. At the project formulation stage, the situation of

the portion or section of the river for water utilization should be surveyed taking into

consideration the assumed recession section and the possibility of changes in the

position of the intake and the waterway route.

When a fall or steep valley is to be used for power generation, local information on the

use of such a fall or valley should be obtained together with a survey on the relevant

legal regulations.


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(4) Existence of other development plans/projects

A survey should be conducted on the existence of other development plans/projects in

terms of roads, farmland, housing and tourism, etc. which may affect the planned

project site and/or its surrounding area.

(5) Civil structures in adjacent area and materials used

Most civil structures of a small-scale hydropower plant are similar to those of irrigation

facilities and road drainage facilities. The materials used for these structurers are often

available or can be obtained near the planned project site.

The use of constructors, human resources and local materials involved in these civil

structures is important from the viewpoint of reducing the construction cost,

contribution to the local economy and ensuring easy maintenance and repair. Hence, a

survey should be conducted on similar civil structures in the adjacent area of a project

site to obtain useful reference materials for project planning and design.

(6) Presence of natural topographical features and existing structures usable for power

generation

When an existing irrigation channel or similar is used (including widening and/or

reinforcement) as a waterway for power station, it is necessary to check the

cross-section, gradient and current water conveyance volume, etc. of such a channel.

(7) Existence of important ground features and vegetation

Even a small-scale hydropower plant necessitates some alteration of the localtopography. When important ground features and/or vegetation exist along the planned

route of the waterway, they must be carefully dealt with. For this purpose, their

locations and conditions, etc. should be duly noted for discussions with concerned

parties such as the landowner(s) and representatives of the local government.


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Chapter 3

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3.4 Validation of Geological Conditions Affecting Stability for Main Civil

Structures

The survey on the ground stability, especially that of the surface layer, is required for

the construction of a small-scale hydropower plant due to (i) the exposed structure of

most of the main civil structures and (ii) the rooting of the waterway on a sloping

hillside. The results of investigation should be presented in the form of sketch drawings

(refer to Fig 3.4.1) for reference purposes when determining the basic structures for

civil works.

Fig.3.4.1 A geological sketch based on site observations


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3.5 Survey on Locations of Civil Structures

Field reconnaissance by the hydropower specialist is important to establish a waterwayroute based on an existing topographical map and other relevant information for the

planning of a micro-hydropower plant. The results of the reconnaissance survey will

determine if the project will proceed or not.

The items to be checked during this survey are listed below. It is necessary to repeat the

field reconnaissance in line with the progress of the planning and design. When

uncertainties emerge, particularly at the design stage, field verification is necessary.

Moreover, there is a need to keep the expected demand in mind. Therefore, this survey

should be conducted in parallel with the demand survey.

It is important not only to select suitable locations for such individual facilities as the

intake weir and waterway, etc. but also to carefully examine the locations of their tie-in

sites.

For the development of micro-hydro, the maximum use of natural topographical

features is important from the viewpoint of cost reduction. It is, therefore, necessary to

conduct the survey based on a full understanding of the items discussed in “Chapter

4,4.3 Selection of Location for Main Civil Structures”.


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Chapter 3

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3.6 Measurement of River Flow

(1)

Necessity of Measurement of River Flow(2)

The estimated river flow at a project site is considered reasonably reliable if it is based

on data from a nearby gauging station. As such, it may not be necessary to conduct

actual discharge measurement at the project site.

However, when river flow data is difficult to obtain, it is preferable to measure the river

discharge in the dry season, by means of simple method, to confirm the appropriateness

of the estimated flow duration. Any stoppage of power generation due to a reduced

water flow volume significantly affects the generation of a micro-hydropower plant,

thus it is essential to check the discharge at dry season. Although it is necessary to

record the river flow for at least one year in mini hydropower development, the river

flow during the dry season should be checked even for micro hydropower development.

Fig.3.4.2 shows the Flowchart to check Minimum Flow/ Duration Curve.

Should there be a need to measure the discharge, the observation period must be

carefully determined based on past rainfall records and information relative to the

climate.

It is also necessary to check and evaluate the observation results in connection with the

characteristics (for example, drought year or wet year) of the year of observation based

on past rainfall records, etc.

The stream flow measuring method, frequency and water level observation unit can be

simplified in the following manner to reduce the survey cost.


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Manual

- 3-8 -

Water Level Discharg

H Q

(m) (m3/s)

XXX 0.230 0.1

YYY 0.550 1.7

ZZZ 0.300 0.2

WWW 0.380 0.6

Date

Installation of Staff Gauge

(Base Point)

Selection of Measurement

Point

Measuring of Cross Section

Measuring of Cross Sectional

Area

(A)

Measuring of Velocity /Speed

(V)

Calculation of Discharge

(Q=A x V)

Record the water level

on Staff gauge (H)

A n o t h e r d a y

a t l e a s t 3 t i m e s

r e p e a t

Daily

Record

(Hd)

Calculation o f Rating Curve

Calculation of Daily

Discharge

Calculation of Duration

Curve

1

2

3

4

5

Staff Gauge

Fig.3.4.2 Flowchart to check Minimum Flow/ Duration Curve


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(2) Flow measuring method

A stream flow measuring method which is appropriate for the river conditions can be

adopted. [Reference 3-1: Simple method of stream flow measuring]

(3) Frequency of stream flow measuring

In principle, stream flow measuring should be conducted at least three times a year to

analyze the relation between the water level and the discharge in the range below the

assumed maximum discharge.

(4) Water level observation unit

A staff gauge should be set up at a point near the flow observation point where visual

water level observation can be easily carried out.

3.7 Measurement of Head

The head between the intake point and the headtank and the head between the headtank

and the outlet point should be measured. At the initial planning stage, however, it may

be sufficient to measure the head between the planned headtank location and the outlet

level.

While a surveying level can be used for the purpose of measuring, a more simple head

measuring method may be sufficient. [Reference 3-2: Simple methods of head

measuring]


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Chapter 3

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3.8 Demand Survey

3.8.1 Demand survey method

There can be many types of power demand facilities for small-scale hydropower

generation to respond to the conditions of the subject area for development. In the

preparation of development plan, accurate understanding of the power demand facilities

in the subject area for development is essential.

What is important is to ensure the efficiency and practicality of a demand survey. It is

necessary to estimate a slightly higher demand level than the assumed scale of power

generation so that it would adequately respond to the scale of development as well as to

the seasonal fluctuations of the power demand.

3.8.2 Factors to consider in demand survey

The demand survey items are described below. When there is more than one power

demand facility, each facility should be survey.

(1) Location

The suitable route and distance, etc. to each power demand facility should be surveyed

to examine the optimal transmission and distribution lines.

(2) Owners

The opinions and intentions of the owners of power demand facilities regarding the

introduction of a new power supply source should be clarified.

(3) Types and required quality of equipment

The situation of power use by equipment (for power, heating, lighting and electrical

control, etc.) and the required level of accuracy (in terms of the allowable voltage

fluctuation and frequency fluctuation) should be surveyed.

(4) Equipment capacity, etc.

The equipment capacity, power consumption level and electricity tariff (or estimated

electricity tariff in the case of planning) should be surveyed.


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Chapter 3

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(5) Period of use

Any seasonal or daily fluctuation of power use and the range of fluctuation should be

surveyed.

(6) Year of installation and service life

The year (date) of installation of each power demand equipment and its service life or

planned period of use should be surveyed.

(7) Likely problems associated with power cut

The likely problems and financial losses associated with a power cut to power demand

facilities should be surveyed.


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3.9 Actual Field Survey

Actual field survey for the design of structures for micro-hydropower system should be

conducted after the identification of their location and route. The following should be

done if necessary:

(1) A proper understanding of the local topography is important for the planning of a

small-scale hydropower plant like the main exposed structure civil structures.

Topographical surveying is particularly required for such structures as the intake

facility, headtank and generating station, etc., each of which covers a wide area, to

improve their design accuracy. In general, the accuracy of the topographical

surveying around civil structures tends to be in the range of 1/100 – 1/200 for small

to medium-scale hydropower plants. However, topographical surveying accuracy in

the region of 1/500 should be sufficient for independent micro-hydro scheme

because an error in topographical surveying hardly affects the work volume for

small structures.

(2) During the implementation stage: For the waterway and access road, etc., route

surveying (center line and cross-section surveying) may be sufficient for planning

and design purposes and should be effective from the viewpoint of cost reduction,

particularly when the required surveying length is long. These routes must, however,

be carefully determined based on the results of the field reconnaissance conducted

by the planner(s).


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- 3-13 -

[Ref. 3-1 Method of stream flow measurement]

1. Using electromagnetic current meter

Generally, the current meter used for the measurement of river flow is screw type. But nowadays, an

electromagnetic current meter that doesn’t have rotating parts is available in the market. This is suitable for

measurement of river flow in a small-scale hydro site. It is lightweight, and can be measured even in shallow

river.

In case of survey for small-scale hydropower development, a simple method like the following are sufficient

for discharge measurement using electromagnetic current meter.

(1) Three-points measuring method ・・・・Vm = 0.25×( V0.2 + 2V0.6 + V0.8 )

(2) Two-points measuring method ・・・・Vm = 0.50×( V0.2 + V0.8 )

(3) One-point measuring method ・・・・・Vm = V0.6

(4) Surface measuring method ・・・・・・Vm = 0.8×Vs

where, Vm: Mean velocity Vs: Surface velocity

V0.2: Velocity at the depth of 20% below the water surface



Following should be considered when selecting the point of measurement in the stream .

(1) No irregular wave and whirlpools at the surface.

(2) No subsurface flow, back-flow, and stagnation.

(3) No irregular change of water level.

(4) No crossing-over of stream line.

During measurement, the riverbed should be cleaned, if necessary.


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- 3-14 -

2. Float measuring method

Basically, float measuring method is applied during floods when measurement with current meter is not

possible. But, it is applicable during the stage where development sites are not decided yet or the current meter

is not available.

(1) Measuring method

1) Measurement should be made at the place where the axis of streambed is straight and the cross section

of the river is almost uniform.

2) Flowing distance of floats should be more than the width of river.

3)Setting transverse lines at the upstream and downstream perpendicular to the axis of streambed.

Flow-down distance (upstream and downstream lines) = L

4) Measuring the cross sectional areas at the upper and lower transverse lines to get the average value of

the cross sectional areas of flow (Amean).

Additional measurement should be made at the middle section of two lines if the cross

section of river is not uniform.

5) Floats are dropped at upstream of the upper transverse line, the time required from upper to lower

transverse line is measured.

6) Measurement should be done several times at different divisions of the river cross-section in the

transverse direction. (more than three divisions)

(2) Stream flow calculation formula

Vm = C×Vmean

C: (1) Concrete channel which cross section is uniform = 0.85

(2) Small stream where a riverbed is smooth = 0.65

(3) Shallow flow (about 0.5ｍ) = 0.45

(4) Shallow and riverbed is not flat = 0.25

(1) (2)

Vm = 0.85×Vmean Vm = 0.65×Vmean

(3) (4)

0.5 m

Vmean

Vmean Vmean

Vm = 0.45×Vmean Vm = 0.25×Vmean

Vmean


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- 3-15 -

3. Weir measuring method

The discharge is small and the use of current meter or float measuring method is impossible, the weir as shown

below is built and discharge is measured by measuring the overflow depth at the river.

Upstream line

Downstream line

F

l o w i n g d i s t a n c e o f f l o a t s ( L )

Drop line of floats

A – A’ Cross section

B – B’ Cross section

C – C’ Cross section

A – A’

C – C’ Mean Cross section


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In this method, the stream flow can be obtained by following formula.

Q = C・L・h1.5

Q：Discharge (m3/s) C：Discharge coefficient L：Opening width of weir (m)

h：Overflow depth (m)

4. Others

It is applicable to use the following method to measure smaller stream flow.

C = 1.838 ( 1 + ) ( 1 - )h 10

0.0012 ( h／L )1/2


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- 3-17 -

Place of survey date time : water level

No. Remarks

Distance from left bankDepth of riverArea of flow section

Waterdepth Discharge





Average of Veloc ity (cm/s )

dischage(l/s)

Survey sheet of discharge

1 2 3 4 5 6 7 8 9 10 11

50.0

40.0

30.0

20.0

10.0

Depth at point and velocity(cm, cm/s)

60.0

Cross Section of river

0.0


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- 3-18 -

[Ref. 3-2 Method of head measurement]

1. Using clear hose method

The figure below shows this method. The method is useful for low head sites, since it is cheap and reasonably

accurate. To get the head of two points, measuring the difference of water level of the water-filled clear hose at

two points. Even a man who does not have a skill of survey work can apply this method.

H1

H3

H4

H5

H6

H2

Head

H1

H3

H4

H5

H6

H2

Head

Head = H1+H2+H3+H4+H5+H6

H1 = B1-A1

B1

H1

A1

Date :

No. Hi=Bi-Ai(meters)

1 0.85

2 0.86

3 0.86

4 0.91

5 0.99

6 0.75

7 0.30

8 0.90

9 0.7010 0.74

11 2.30

12 0.66

10.82

Location :

0.70 1.36

Total Height (meters)=

1.00 1.74

0.20 2.50

1.00 1.90

1.00 1.70

1.00 1.75

1.00 1.30

1.00 1.91

1.00 1.99

1.00 1.86

1.00 1.86

Ai(meters)

Bi(meters)

1.00 1.85

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