tailwater level.pdf

THE STUDY ON INTRODUCTION OF RENEWABLE ENERGIES
IN RURALAREAS IN MYANMAR
FINAL REPORT
Volume 4 Main Report
Manuals for Sustainable Small Hydros
Part 4-1 O&M Manual-Small Hydros
Part 4-2 Design Manual-Small Hydros
Part 4-3 Design Manual-Village Hydros
Part 4-4 Institutional and Financial Aspects

i
THE STUDY ON INTRODUCTION OF RENEWABLE ENERGIES
IN RURAL AREAS IN MYANMAR
Final Report
Volume 4 Manuals for Sustainable Small Hydros
Part 4-2 Design Manual - Small Hydros
TABLE OF CONTENTS
1 Investigation and Planning ...........................................................................................1
1.1 Estimate of Power Demand................................................................................1
1.2 Measurement of Discharge and Head.................................................................4
1.2 Measurement of Discharge and Head.................................................................5
1.3 Available Power Discharge...............................................................................10
1.4 Surveys for Topography and Geology..............................................................12
1.5 Layout of Power Facilities................................................................................15
1.6 Hydropower Planning.......................................................................................18
2 Design of Civil Structures ..........................................................................................22
2.1 Head Works ......................................................................................................22
2.2 De-silting Basin................................................................................................32
2.3 Power Canal......................................................................................................34
2.4 Head Tank.........................................................................................................40
2.5 Regulating Pond ...............................................................................................43
2.6 Penstock............................................................................................................47
2.7 Powerhouse.......................................................................................................53
3. Design of Generation Equipment ...............................................................................54
3.1 Turbine..............................................................................................................54
3.2 Generator ..........................................................................................................65
3.3 Control Unit......................................................................................................68
3.4 Inlet valve .........................................................................................................70

ii
LIST OF TABLES
Table 1.1.1 Sample of Power Demand Estimate................................................................4
Table 1.6.1 Minimum Turbine Discharge ..........................................................................19
Table 2.1.1 Various Types of Weir ....................................................................................24
Table 2.1.2 Various Types of Intake ..................................................................................28
Table 2.1.3 Hydraulic Requirements Applied to Side Intake ...........................................30
Table 2.3.1 Facilities for a Canal........................................................................................35
Table 2.3.2 Velocities for Unlined Canals .........................................................................36
Table 2.5.1 Sand Flushing Capacity of 'Saxophone' Suction Head....................................46
Table 3.1 Type of Turbines and Applicable Range............................................................55
LIST OF FIGURES
Figure 1.1.1 National Grid in Myanmar.............................................................................1
Figure 1.1.2 Power Demand Categories.............................................................................1
Figure 1.2.1 Example of Discharge Measurement .............................................................5
Figure 1.2.2 Discharge Measurement by Current Meter.................................................5
Figure 1.2.3 Velocity Measurement by Current Meter ......................................................6
Figure 1.2.4 Measurement of Sectional Area and Velocity ...............................................6
Figure 1.2.5 Velocity and Depth ........................................................................................6
Figure 1.2.6 Measurement by Float....................................................................................6
Figure 1.2.7 Discharge Measurement by Weir...................................................................7
Figure 1.2.8 Water Level Gauge ........................................................................................7
Figure 1.2.9 Example of Stage-Discharge Rating Curve ...................................................7
Figure 1.2.10 Form of Discharge Measurement.................................................................8

iii
Figure 1.2.11 Measurement of Discharge and Head ..........................................................9
Figure 1.2.12 Preliminary Planning of Layout Based an Q & H .......................................9
Figure 1.2.13 Measurement of Head Using Carpenter’s Level..........................................9
Figure 1.2.14 Measurement of Head Using Pressure Gauge..............................................9
Figure 1.2.15 Tools for Measurement of Head ..................................................................9
Figure 1.3.1 Use of Water ..................................................................................................10
Figure 1.3.2 Example of Available Power Discharge ........................................................11
Figure 1.4.1 Sample of GPS Mapping................................................................................13
Figure 1.4.2 Test Pit ...........................................................................................................14
Figure 1.4.3 Sample Log of Test Pit...................................................................................14
Figure 1.5.1 Relation between Length and Head ...............................................................15
Figure 1.5.2 Mini/Micro Hydro Utilizing Drops or Falls...................................................15
Figure 1.5.3 General Layout of Small Hydro.....................................................................16
Figure 1.5.4 General Profile of Open Waterway System...................................................16
Figure 1.5.5 Typical Profile of Waterway..........................................................................17
Figure 1.6.1 Small Hydro Development Pattern-1.............................................................18
Figure 1.6.2 Small Hydro Development Pattern-2.............................................................19
Figure 1.6.3 Effective Head for Impulse Turbines.............................................................20
Figure 1.6.4 Effective Head for Reaction Turbines............................................................20
Figure 1.6.5 Flow Duration Curve .....................................................................................21
Figure 2.1.1 Head Works....................................................................................................22
Figure 2.1.2 Location of Intake ..........................................................................................22
Figure 2.1.3 Tyrolean Intake ..............................................................................................23
Figure 2.1.4 Profile of Tyrolean Intake..............................................................................23
Figure 2.1.5 Sand Flush Gate .............................................................................................23
Figure 2.1.6 Weir Level......................................................................................................25
Figure 2.1.7 Weir Profile....................................................................................................25
Figure 2.1.8 Example of Rating Curve...............................................................................25
Figure 2.1.9 Flowchart to Estimate Inflow Discharge into Intake .....................................26

iv
Figure 2.1.10 Sample of Intake Plan ..................................................................................29
Figure 2.1.11 Schematic Profile of Intake Structures.........................................................29
Figure 2.1.12 Front Elevation of Skimmer Wall at Entrance.............................................31
Figure 2.1.13 Trash racks ...................................................................................................31
Figure 2.2.1 De-silting Basin..............................................................................................32
Figure 2.2.2 Side Spillway .................................................................................................32
Figure 2.2.3 Sand Drain Gate.............................................................................................32
Figure 2.2.4 Overflow Discharge and Water Surface Profile in Side Spillway.................33
Figure 2.3.1 Power Canal ...................................................................................................34
Figure 2.3.2 Canal and Slope Failure .................................................................................34
Figure 2.3.3 Side Spillway .................................................................................................34
Figure 2.3.4 Existing Footpath ...........................................................................................35
Figure 2.3.5 Structure without Canal..................................................................................36
Figure2.3.6 Stone Masonry Canal......................................................................................36
Figure 2.3.7 Canal Design..................................................................................................37
Figure 2.3.8 Side Channel Spillway...................................................................................37
Figure 2.3.9 Water Surface : Uniform Flow.......................................................................37
Figure 2.3.10 Discharge Calculation..................................................................................38
Figure 2.3.11 Type of Canal Lining ...................................................................................39
Figure 2.3.12 Cross Drain under Power Canal...................................................................39
Figure 2.3.13 Cross Drain over Power Canal.....................................................................39
Figure 2.4.1 Head Tank......................................................................................................40
Figure 2.4.2 Head Tank with Spillway...............................................................................40
Figure 2.4.3 Head Tank......................................................................................................41
Figure 2.5.1 Pondage Capacity...........................................................................................43
Figure 2.5.2 Inflow Estimation...........................................................................................44
Figure 2.5.3 'Saxophone' Sand Flushing ............................................................................45
Figure 2.6.1 Penstock .........................................................................................................47
Figure 2.6.2 Water Hammer Analysis................................................................................49

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Figure 2.6.3 Head Loss.......................................................................................................50
Figure 2.6.4 Head Loss of Trashrack .................................................................................50
Figure 2.6.5 Head Loss of Penstock Inlet...........................................................................51
Figure 2.6.6 Head Loss Coefficient for Reducer................................................................51
Figure 2.7.1 Powerhouse ....................................................................................................53
Figure 3.1 Structure of Pelton Turbine...................................................................................55
Figure 3.2 Water Flow in Turgo Impulse Turbine.................................................................57
Figure 3.3 Structure of Turgo Impulse Turbine .....................................................................57
Figure 3.4 Inner Shape of Turgo Impulse Turbine.................................................................57
Figure 3.5 Installation of Turgo Impulse Turbine and Tailrace.............................................58
Figure 3.6 Structure of Cross Flow Turbine ..........................................................................59
Figure 3.7 Water Flow in Cross Flow Turbine ......................................................................59
Figure 3.8 Characteristics of Cross Flow Turbine .................................................................59
Figure 3.9 Runner Diameter and Width.................................................................................60
Figure 3.10 Draft Head of Cross flow Turbine ......................................................................61
Figure 3.11 Spiral-type Francis Turbine with Horizontal Shaft, Single Runner and Single
Discharge....................................................................................................................62
Figure 3.12 Spiral-type Francis Turbine with Horizontal Shaft, Single Runner and Double
Discharge....................................................................................................................62
Figure 3.13 Structure of Package-type Bulb Turbine.............................................................63
Figure 3.14 Structure of S-shaped Tubular Turbine...............................................................64
Figure 3.15 Reversible Pump Turbine ...................................................................................64
Figure 3.16 Turbine Selection Diagram.................................................................................65
Figure 3.17 Concept Figure of Dummy Load Governor........................................................68
Figure 3.18 Excitating Circuit with AVR ..............................................................................70
Figure 3.19 Structure of Butterfly Valve................................................................................71
Figure 3.20 Structure of Through-flow Valve........................................................................72
Figure 3.21 Structure of Sluice Valve....................................................................................72

vi
LIST OF APENDICES (Presented in Part 6-2 of Volume 6)
Appendix 1 Nomograms
Appendix 2 Computer Programs
Appendix 3 Sample of Design Criteria
Appendix 4 Project Drawings
Appendix 5 Sample Specifications (included in Database)
Appendix 6 Sample of Cost Estimate for Nam Lan Hydropower Project
Appendix 7 Principal Dimensions of Turbines
Appendix 8 Principal Dimensions of Generators
Appendix 9 Unit Conversion Table of Weights and Measures
Appendix 10 Technical Terms

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Volume 4
Manuals Part 2
The Study on Introduction of Renewable Energies
in Rural Areas in MYANMAR
1 Investigation and Planning
1.1 Estimate of Power Demand
(1) Need for Power Demand Survey
There are many villages scattered around the rural
areas of Myanmar, where by far the largest
percentage of the population lives, that do not have
electricity and where the electrification ratio has not
reached 8%. Any further extension of the
distribution lines from the national grid would be
difficult, even to areas near the grid system, because
of the shortage of generated power.
In order to advance rural electrification under such
circumstances, the development of isolated power
systems would be more practical than extension of
the power grid. Renewable energy such as small ~
micro-scale hydropower, for which the potential is
abundant in the mountainous regions, would be one
of the most effective sources for the areas, and the local technological expertise has
been developing to some extent recently.
It is essential to be able to estimate accurately the power demand for the target area
when a small hydropower scheme is launched. Because hydropower is a site-specific
energy, identification of hydro potentials to meet the required demand should be the
basis for the planning of rural electrification. For the power supply in an isolated
grid system, the power generated should be kept at a higher level than the load
incurred, otherwise the following measures are needed:
1) Backup power by other power sources such
as diesel generators
2) Adjustment of the power demand
(2) Survey for Power Demand
The power demand in the rural areas in
Myanmar can be classified into the following
categories according to a rural society survey
conducted by the JICA Study Team in June
2001.
Source: MEPE
Figure 1.1.1
National Grid in Myanmar
Demand
Center
Household
Population
Local
Industries
Public
Facilities
Source: JICA Study Team
Figure 1.1.2
Power Demand Categories

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Household use : light, TV, radio, refrigerator, rice cooker, etc.
Public use : streetlight, temple/pagoda, clinic/hospital, school, etc.
Industrial use : local industries, etc.
An investigation of the rural society needs to be carried out at the initial stage of the
planning to estimate the power demand, of which the main items are summarised as
follows:
a) Numbers of household and population in each village tract
b) Numbers, scales, and time zone of electric appliances in home use, public use, and
local industry use
c) Existing power facilities and existing electrification ratio
d) Future development
The general information required for the planning is as follows:
z Administration of the township that covers the demand centre
z Location, area, and accessibility of the demand centre
z Main industries
z Willingness to electrification
z Income and ability to pay for electricity
z Possibility for rehabilitation of the existing power facilities and extension of
distribution lines
z Land use in the river basin, and agricultural cropping patterns
z Land acquisition
z Sectional map showing the village tracts
The load curves for seasonal and time fluctuations of the power demand should be
estimated taking into account the usage patterns of electrical facilities/appliances, ratio
of concurrent use, etc. by reference to the existing records in neighbouring power
stations.
z Seasonal fluctuation : Agricultural processing, drying processing
in monsoon regions
z Time fluctuation : Lighting in night-time use, local industries
in daytime use

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Where electric motors are being operated, the gross power demand (Pd) for such
facilities should be within a suitable range due to the inrush current required at the
starting time.
z Pd < (Total power output – Other demand) x 40 %
The main electrification demands in home use are for lighting, TV, radio and
refrigerator in that order of priority, and the averaged household demand was
estimated at 120 W for lighting, and 160 W after introducing rice cookers, according
to the rural survey by JICA Study Team conducted in June 2002.
Local cottage industries may consist of the main demand during daytime and can be
an important factor for determining the electricity tariff system, local development,
and sustainable management of the VEC. An investigation is needed to determine the
number of units, power consumption, operating conditions, and diesel consumption
required to service the electricity powered machines being operated in existing local
cottage industries.
(3) Sample of Power Demand Estimate
A sample of the power demand estimate for a village with 2,082 household in the
Northern Shan State is shown below:

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Table 1.1.1 Sample of Power Demand Estimate
Customer Number Step Night Daytime
of Unit Con- Sim- Unit Con-Acce Estimat-Sub-totalUnit Con-Sim- Unit Con-Acce Estimat- Sub-total
Custo- sumption ulta- sumption ssibi ed Power sumption ulta- sumption ssibi ed Power
mer neou lity Demand neou lity Demand
Watt s % Watt % kW kW Watt s % Watt % kW kW
1.Household 2,082 1-1 130 90% 120 93 232.4 232.4 130 15% 20 93 38.7 38.7
1-2 220 70% 160 93 309.8 309.8 220 20% 50 93 96.8 96.8
2. Public
2.1 Street 16 400 50% 200 100 3.2 400 0 0 100 0.0
Light
2.2 Temple & 11 2,000 30% 600 100 6.6 2,000 40% 800 100 8.8
Pagoda
2.3 Hospital 1 230 70% 160 100 0.2 230 50% 120 100 0.1
2.4 Clinic 1 310 70% 220 100 0.2 310 50% 160 100 0.2
2.5.1 H.School 1 6,200 0 0 100 0.0 6,200 20% 1,240 100 1.2
2.5.2 M.School 0 1,640 0 0 100 0.0 1,640 20% 330 100 0.0
2.5.3 P.School 9 380 0 0 100 0.0 380 20% 80 100 0.7
Sub-total 10.2 11.0
3. Business
3.1 Restaurant 3 3,185 30% 960 100 2.9 3,185 30% 960 100 2.9
3.2 Guest House 2 4,905 50% 2,450 100 4.9 4,905 30% 1,470 100 2.9
Sub-total 7.8 5.8
4. Industry
4.1 Rice Mill 18 5,000 0 0 100 0.0 5,000 80% 4,000 100 72.0
4.2 Oil Mill 6 5,000 0 0 100 0.0 5,000 80% 4,000 100 24.0
4.3 Powder Mill 0 5,000 0 0 100 0.0 5,000 80% 4,000 100 0.0
4.4 Sugarcane 0 5,000 0 0 100 0.0 5,000 80% 4,000 100 0.0
Processing
4.5 Saw Mill 2 10,000 0 0 100 0.0 10,000 80% 8,000 100 16.0
4.6 Paper Mill 0 5,000 0 0 100 0.0 5,000 80% 4,000 100 0.0
4.7 Tofu Mf'g 3 4,000 0 0 100 0.0 4,000 80% 3,200 100 9.6
4.8 Noodle Mf'g 3 7,000 0 0 100 0.0 7,000 80% 5,600 100 16.8
4.9 Furniture 5 5,000 0 0 100 0.0 5,000 80% 4,000 100 20.0
4.10 Iron Work 5 4,000 0 0 100 0.0 4,000 80% 3,200 100 16.0
4.11 BCS 2 1,500 0 0 100 0.0 1,500 80% 1,200 100 2.4
4.12 Weaving 0 5,000 0 0 100 0.0 5,000 80% 4,000 100 0.0
4.13 Water Pump 25 200 0 0 100 0.0 200 80% 160 100 4.0
Sub-total 0.0 180.8
5. Total
5.1 1-1+2,3,4 250.3 236.4
5.2 1-2+2,3,4 327.8 294.5
6. Gross Total
6.1 1-1+2,3,4 Including 5% of transfer loss 270 Incl. 5% transfer loss 250
6.2 1-2+2,3,4 Including 5% of transfer loss 350 Incl. 5% transfer loss 310
z Population : 12,229
z Household : 2,082
z Existing electrification ratio : 13.6 %
z Willingness to pay for initial fee : K 23,000
z Willingness to pay for monthly fee:
K 680/month
(surveyed in June 2001)

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Figure 1.2.2 Discharge Measurement
by Current Meter
1.2 Measurement of Discharge and Head
(1) Measurement of Discharge
In the rural areas of Myanmar, the existence of either discharge records or water level
gauging station information is generally expected at the rivers where a small
hydropower station is planned. When a small hydropower site is identified, the
discharge measurement of the river through a year is preferable. It is indispensable
for the planning to carry out the following:
1) Discharge measurement more than 10 times within a proper range that enable
establishment of the stage-discharge rating curve at the intake site.
2) Establishment of the water level gauge, and as many as possible readings,
especially during the dry season. The task of gathering such information may be
sublet to the local inhabitants.
.
The river discharges are likely to decrease
significantly in the dry season in Myanmar as
compared with those in the rainy season. It
is, accordingly, essential to investigate
discharges, especially in the dry season, for
the planning of a small hydro station with an
isolated grid system to supply stable energy
throughout a year.
The following methods are available to
measure the river discharge:
3) Current Meter
Figure 1.2.1 Example of Discharge Measurement

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v0.6
0.6 d
Current Meter
Figure 1.2.3 Velocity Measurement by
Current Meter
① ② ③ ④ ⑤ ⑥ ⑦
b
v1 v2 v4 v5
v6
d1
d2
d3
d4
d5
d6
d7
d8
d9
d10 d11
v3
d11
b b b b b
Figure 1.2.4 Measurement of Sectional
Area and Velocity
vs
Float
vm
Figure 1.2.6 Measurement by Float
This is the most common method to measure velocities where the stream is not
irregular and turbulent. A location for the measurement should be selected in a
straight stretch of the river. Simple measurements as below may be sufficient for
streams where a small hydropower scheme is planned:
i) 2-point method Vm = 1/2 x (V0.2 + V0.8) for depth > 1 m
ii) 1-point method Vm = V0.6 for depth < 1 m
where, Vm : mean velocity, V0.6 : velocity at 60% depth from surface.
The discharge of flow can be derived using the
following equation:
A
V
Q ⋅
=
4) Float Method
This is the easiest method to measure
velocities in a stream without any special
equipment. However, the accuracy cannot be
expected where the stream is irregular, wide,
and shallow. The discharge of flow is given
by the following formula:
A
V
c
Q ⋅
⋅
=
Figure 1.2.5
Velocity and Depth
d
0.2d
0.6d
0.8d
V0.2
V0.6
V0.8
Vs
Where, Q : discharge (m3
/s)
V : mean velocity (m/s)
A : cross sectional area (m2
)

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Figure 1.2.8 Water Level
Gauge
L > 3h > 2h
> 2h
h
> 4h
h
> 2h
Figure 1.2.7 Discharge Measurement
by Weir
5) Weir Method
This method requires construction of a weir
across the stream to measure discharge directly in
the stream. The discharge of flow is given by
the following formula:
5
.
1
)
2
.
0
(
84
.
1 h
h
L
Q ⋅
⋅
−
⋅
=
6) Stage-Discharge Method
This method consists of the following procedures:
(i) Discharge measurement more than 10 times
within the range required to establish a
stage-discharge rating curve
(ii) Water level gauge reading
The relation between water level and
discharge can be expressed by a quadratic
equation. It is noted that the
stage-discharge rating curve should be
reviewed periodically for calibration,
especially after the flood season that may
result in erosion or sedimentation on the
riverbed.
A form for discharge measurement is
shown below:
Where, c =0.85 for concrete channel
0.80 for smooth stream
0.65 for shallow stream
Where, Q : discharge (m3
/s)
L : length of weir (m)
h : overflow depth (m)
Example of Stage-Discharge Rating Curve
0.00
0.25
0.50
0.75
1.00
1.25
1.50
0 5 10 15
Discharge (m3
/s)
WL
Gauge
Reading
(m)
Q = 5.15H2
+ 4.19H + 0.98
Figure 1.2.9 Example of Stage-Discharge
Rating Curve

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Volume 4
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Velocit
rig
ban
lef
ban
1s 2n Av
1
Sta
En
Av
Gau Recor
Sta
En
Av
Calc'
Check
DISCHARGE
Measure
Are
(m
2
)
Tota
(m
2
)
1s
Note
Area 2
)
V=
Rod / Wire /
Boat / Bridge /
Outside
Dischar
(m
3
)
Inside
Avera
dischar
(m/s
Are
Avera
depth
Widt
(m)
Distance
fro
Recorded
Observ
Dat
Measuremen
Calcualte
Curre
mete
Typ
Conditi
Water level
Tim
Discharge3
/s)
Coefficie
Measure
Cal
Resu
6
5
4
3
10
9
8
7
13
12
11
Weath
Wind
Wind
Ave velocity
No
2
Depth
Velocity
Velocit
Measure
depth
Av
2n
Figure 1.2.10 Form of Discharge Measurement

-9- The Study on Introduction of Renewable Energies
Nippon Koei / IEEJ
Volume 4
Manuals Part 2
Head (m)
Discharge (m
3
/s)
Figure 1.2.11 Measurement of Discharge
and Head
Intake
Power canal
Head Tank
Penstock Powerhouse
Tailrace
Head
H (m)
Discharge Q (m3
/s)
Power (kW) = 9.8・Q・H・η
Efficiency
η = 0.5~0.7
Figure 1.2.12 Preliminary Planning of
Layout Based on Q & H
(2) Measurement of Head
The detailed planning and design are to be made based on a topographic map with a
scale of 1/500 or more, but in the preliminary planning stage, much quicker and less
costly methods can be used for measurement of the head.
The following tools are available to measure a head for the preliminary planning.
X
Y
Hg
Measurement of Head
Using Pressure Gauge
Presure
Gauge
Plastic Tube
filled with water
Figure 1.2.14 Measurement of Head Using
Pressure Gauge
X
Y
h
h
X1
X2
Xn
hn
Hg
Level
Measurement of Head
Using Carpenter's Level
Figure 1.2.13 Measurement of Head Using
Carpenter’s Level
Distance Meter Clinometer
Figure 1.2.15 Tools for Measurement of Head
Portable
Compass
GPS to measure
coordinates &
altitude
Source:
(Figure 1.2.11~1.2.15)
JICA Study Team

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Irrigated
Area
Irrigation
Canal
Powerhouse
Intake
Figure 1.3.1 Use of Water
1.3 Available Power Discharge
If paddy fields with single-cropping are developed in a river basin whose water is
utilised for power generation, the irrigation water supply usually starts in May when
the river discharge is at the minimum level in the end of the dry season. Therefore,
the available discharge in May is likely to become the lowest under such
circumstances.
The first priority for water utilisation is generally given to the irrigation supply in rural
areas in Myanmar. It is therefore required to investigate not only the river discharge,
but also the existing water utilisation, irrigation system, and rainfall patterns to
estimate the available power discharge. The following items need to be surveyed at the
planning stage:
z Land utilisation in the areas affected by a hydropower station
z Irrigation area, the cropping patterns, and the irrigation supply discharge
z Future development plan for irrigation
z Basic stance of local inhabitants for the water utilisation
When the water use produces a conflict between
irrigation and power generation demands, the
following needs to be considered:
1) The location of the power generation facilities
should be carefully selected to minimise the
conflict between irrigation water use and power
discharge in the area where the river flow is
utilised for the irrigation in the river stretch
between the intake and the tailrace.
2) The river discharge and the irrigation demand in
the areas affected by the hydropower plant should
be investigated throughout one year to estimate the
available power discharge, taking into account the existing irrigation practices.
3) Irrigation water for paddy fields is approximately 1.0 m3
/s for 1,000 ha in general.
Areas, cropping patterns, irrigation canal systems, return flow into the river,
rainfall and supplemental discharge from the river are major factors to estimate the
irrigation demand.

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Discharge at Hosang Chaung in 2001 - 2002
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
5 6 7 8 9 10 11 12 1 2 3
Q (m3
/s)
4
Irrigation Requirement
River Discharge
Available discharge for
power generation
4 5
2001 2002
Source: Measurement and Assumption of JICA Study Team
Figure 1.3.2 Example of Available Power Discharge

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1.4 Surveys for Topography and Geology
(1) Topography
An Inch-mile map (1:63,360) is suitable to identify a hydropower scheme site for the
initial planning and to determine accessibility from the demand centre.
The use of a portable GPS may be a powerful tool to position easily and accurately the
specific points in and around the project area at the initial planning stage. A sample
mapping by GPS is shown figure in the next page.
It is essential for the detailed design and construction to map the topography of the
anticipated construction areas that will cover the open civil structures such as intake,
de-silting basin, head tank, and powerhouse at a 1:500 scale or larger, based on a
topographic survey. As for power canals, the profile and cross sectional surveys may
be enough for the design, but further mapping of the areas around the related
structures such as cross drains, side spillways, siphons, etc. will be required.

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Namlan Mini-Hydro Development Plan
15.4
15.6
15.8
16.0
16.2
16.4
16.6
16.8
17.0
23.0 23.2 23.4 23.6 23.8 24.0 24.2
E (97deg xx min)
N
(22deg
xx
min)
about
370
m
about 344 m
Kyutaw Bridge
to Hsipaw
to Nam Lan
Kyutaw Chaung
Nam Pankan Chaung
Hosang Chaung
Hosang Intake Site
Cart Track
No.2 Diversion Channel
from Nam Pankan to Hosang
No.1 Diversion Channel
from Kyutaw to Nam Pankan
No.1 Branch point
No.2 Branch point
No.3 Branch point
No.4 Branch point
Sink Hole
Head Pond
Powerhouse
Hosang
Village
Kyutaw Chaung Branch
Irrigation canal from
Kyutaw Chaung
No.2
Diversion
about
650
m
Nam
Pankan
about
1,100
m
No.1
Diversion
about
750
m
Nam Pankan Bridge
Kyutaw
Village
Source: Field Study of JICA Study Team
Figure 1.4.1 Sample of GPS Mapping

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Figure 1.4.2 Test Pit
(2) Geology
Test pitting is enough to confirm the foundation
geology of the key structures for small hydropower
schemes. A practical pit size is 1.8 m long x 1.2 m
wide x 5.0 m deep. It can be manually dug with
scoops and picks, using a rope and bucket to lift up
the excavated soil without the use of any further
heavy lifting equipment.
A pit log should be prepared for every test pit, as a
report of the test pitting, and should contain the pit
number, its location, boundaries and depths,
description of soil, groundwater table and bedrock
surface, if any, and all other relevant information.
Figure 1.4.3 Sample Log of Test Pit

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Figure 1.5.2 Mini/Micro Hydro Utilizing
Drops or Falls
Tributary
Potential Site-1
Potential Site-2
L1
L2
H1
H2
L / H < 40 General outline
L / H < 20 Advantageous sheme
L / H < 15 Excellent scheme
where L : length of waterway
H : head
Main stream
Figure 1.5.1
Relation between Length and Head
1.5 Layout of Power Facilities
Selection of Site
Attention should be paid to the
following points to identify the
potential for a small hydropower
scheme with an isolated grid system:
1) Discharges are stable even in the
dry season.
2) Specific discharge (m3
/sec / 100
km2
) is big.
3) (L/H) rate is small
4) Distance from demand centre is
short.
Basic Layout
The main components of the civil facilities
are weir, intake, de-silting basin, power
canal, head tank, pondage, penstock,
powerhouse, and tailrace. It is rare for
dam type power generation or tunnel
waterway types to be adopted in a small
hydropower facility. However, existing
irrigation dams may be utilised for
small/mini hydropower in a re-development
plan.
The existing irrigation canals with drops
may be utilised for mini/micro hydropower.
Penstock pipes can be connected to the intake or the de-silting basin without provision
of a power canal. In such a case, since all or part of the irrigation water is to be used
for power generation, the discharge fluctuation during irrigation and non-irrigation
periods needs to be confirmed.
Depending on the nature of the work and the design conditions involved, the
combination of facilities may be varied. As have been experienced in many small
hydropower plants constructed, the major issues relating to the civil components are i)
sedimentation, and ii) hydraulic characteristics during floods. Therefore, suitable
combinations and layouts responding to the specific site conditions need to be

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properly reflected in the design. A typical layout and profile of a small hydropower
station is shown below together with technical notes:
Weir
River Outlet / SandFlush Gate
Spillway
Power Canal HeadTank
SandDrain Gate
Spillway
Trashracks
Intake
Intake Gate
Trashracks
SandDrain Gate
De-silting Basin
Side Spillway
Figure 1.5.4 General Profile of Open Waterway System
De-silting basin
z velocity < 0.3 m/s
z slope steeper than 1/30
Power canal
slope 1/500 ~ 1/2,000
Power Canal
De-silting Basin
Intake
Head Tank Penstock
Powerhouse
Figure 1.5.3 General Layout of Small Hydro
z De-silting basin to be located next to intake
z Low velocity to regulate excessive flow & sand
z Steep slope enough to wash out sediment to river
z Intake to be located in a straight river stretch
z Side intake with weir or Tyrolean intake
z Sand flushing gate to be provided beside the weir
Slope protection
or box culver
Cross drain
at valley
Nearby
demand center

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Penstock
TWL
Anchor Block
Spillway
HeadTank
SandDrain Gate
Trashracks
Powerhouse Tailrace
Figure 1.5.5 Typical Profile of Waterway
Penstock
z to avoid potential land slide area
z to be located on stable ridge
z to be located below hydraulic grade line
z slope protection & drain along penstock
z penstock directly from de-silting basin
may be possible according to topography
Powerhouse
z to be built on firm foundation
z to be located above FWL
z drainage around
Head Tank
z to be located on stable ridge
z capacity against load change
z spillway & sand drain

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1.6 Hydropower Planning
(1) Design Discharge
For a small hydropower station with an isolated grid system, the power generated
should be above the load demanded when a backup power system cannot be provided.
The main points for planning of such a small hydro plant are summarised as follows:
1) determination of the minimum power discharge based on the available minimum
discharge for power generation ( 90 ~ 95% dependable discharge is a general
target)
2) determination of the maximum power discharge depending on the peak load
demand and the available discharge during the rainy season.
Min. Discharge
10
8 9 11 12
1 2 3 4 5 6 7
Non - Operation Period
Firm Power Output
Output
(kW)
Demand Qmin
Potential (Q min ) > Demand
Spill
out
Irrigation
Discharge
Q
(m
3
/s)
Figure 1.6.1 Small Hydro Development Pattern-1

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Ratios of (minimum turbine discharge)/(maximum turbine discharge) and (minimum
efficiency)/(maximum efficiency) are given for typical turbines below:
The numbers of turbines for a small hydropower plant are preferably 1 unit, or 2 units
to cover the wide range of discharge fluctuation. When turbines without discharge
control such as Reverse Type are adopted, several units may be installed to respond to
available discharges in the rainy and dry seasons. The number of units required is
closely related to the selection of turbine type as explained later.
（2） Effective Head
Effective head can be calculated by deducting the head losses from the gross head
between the intake and the tailrace. However, the effective head for impulse turbines
Table 1.6.1 Minimum Turbine Discharge
Type (Qmin / Qmax) (η min / η max)
Francis with horizontal shaft 30 ~ 40% 0.70
Pelton with horizontal shaft 15% 0.75 2-nozzle
Pelton with horizontal shaft 30% 0.90 1-nozzle
Cross flow 15% 0.75 guidevane divided
Cross flow 40% 0.75 guidevane not divided
Turgo impulse 10% 0.75 2-nozzle
Turgo impulse 20% 0.75 1-nozzle
Reversed Pump 100%
Source: Estimation by JICA Study Team
Min. Discharge
1 2 3 4 10 11
5 6 7 8 9 12
Discharge
Q
(m
3
/s)
Output
(kW)
Qmax
Qmin
Non - Operation Period
Spill
out
Max. Power Output
Min. Power Output
Potential (Q min ) < Demand
Demand Peak power operation
or Demand Control
Max. Power Output
for 24-hour
① 24 hours Supply with Min. Power
or
② Peak Power Operation
Irrigation
Figure 1.6.2 Small Hydro Development Pattern-2

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(Pelton, Turgo Impulse, Cross Flow) and that for reaction type turbines (Francis,
Propeller, Tubular) are calculated differently as shown below:
Detailed calculation method for head losses are shown in Chapter 2.6 and Appendix
2-3 of Part 6-2 in Volume 6.
h1
h3
Hg
He
h2
FSWL
TWL
v1
v1
2
/2
v2
2
/2
v2
Head Tank
Penstock
Powerhouse
Tailrace
Hg : gross head (m)
He : effective head (m)
h1 : head loss between Intake & head tank
h2 : head loss between head tank & tailrace
h3 : head between draft tube WL and TWL
Intake
3
2
2
2
1
2
h
g
v
h
h
H
H g
e −
−
−
−
=
Figure 1.6.4 Effective Head for Reaction Turbines
v1
2
/2
v1
h1
h3
Hg
He
h2
FSWL
TWL
Hg : gross head (m)
He : effective head (m)
h1 : head loss between Intake & head tank
h2 : head loss between head tank & tailrace
h3 : head between mean pitch level and TWL
Intake
Penstock
Powerhouse
Tailrace
Head Tank
3
2
1 h
h
h
H
H g
e −
−
−
=
Figure 1.6.3 Effective Head for Impulse Turbines

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Figure 1.6.5 Flow Duration Curve
（3） Power Output and Annual Energy
Power output is given by the following
formula:
H
Q
P ⋅
⋅
⋅
= η
8
.
9
where,
P :Power output (kW)
η :combined efficiency for
turbine and generator
Q :power discharge (m3
/s)
H :effective head (m)
If a run-of-river scheme requires a flow of more than the minimum river discharge, a
flow duration curve is useful to estimate the approximate annual energy as follows:
For maximum discharge Q1 :
Annual Energy E1 = ξ1 · P · 8,760
Where, E1 : Annual energy (kWh)
P : Max. power output (kW)
For maximum discharge Q2 :
Annual Energy E2 = ξ2 · P · 8,760
When a bigger discharge (Q1) is selected, a larger scale of power facility with a lower
plant factor is required, while a smaller discharge (Q2) gives a smaller plant facility
with a higher plant factor. The optimum maximum design discharge to be finally
selected should take into account the revenue generated and the cost incurred in
principle, bearing in mind that the power tariff needs to be properly established.
)
'
'
(
)
'
'
(
)
( 1
BGI
A
area
BCDF
A
area
r
PlantFacto =
ξ
)
(
)
(
)
( 2
ABGI
area
ABCDF
area
r
PlantFacto =
ξ

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Sandbar
River
× Intake (C)
○ Intake (A)
× Intake (B)
Figure 2.1.2
Location of Intake
2 Design of Civil Structures
2.1 Head Works
Site Selection
z This section deals with run-of-river schemes that do not require dam construction,
but employ a diversion structure or weir across the river.
z One of the most common problems affecting a
small/mini/micro hydropower scheme is the
damage to the intake caused by floods, and another
is sedimentation deposited upstream of the intake
or flowing into the waterway. The following points
are to be considered in locating the intake
structures:
1) Intake (A): The best location for an intake is to
locate it along a relatively straight stretch of the
stream
2) Intake (B): Susceptible to severe damage from
floods, debris, and erosion
3) Intake (C): Sediments tend to accumulate in front of the intake and can enter and/or
block the intake
Weir
SandFlush Gate
Spillway
SandDrain Gate
Spillway
Trashracks
Intake
Intake Gate
Trashracks
SandDrain Gate
De-silting Basin
Side Spillway
Figure 2.1.1 Head Works

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Figure 2.1.4 Profile of
Tyrolean Intake
Figure 2.1.3
Tyrolean Intake
Countermeasures against Sedimentation
z The Tyrolean intake is applicable to mini/micro
hydropower stations located on steep rivers
containing boulders and pebbles. The
characteristics of Tyrolean type intake are as
follows:
1) Intake facilities can be minimised.
2) Relatively large amounts of sediment will enter
the intake especially during a flood, so a sand
drain facility with enough hydraulic gradient and
capacity to drain out the sediment is
indispensable. Periodical sand draining operations are
required.
3) Cleaning work for driftwood or leaves trapped on the
screen is necessary.
4) An intake discharge of 0.1 ~ 0.3 m3
/s/m2
, a
screen slope gentler than 30° and a screen
bar interval of 20 ~ 30 mm is generally
practised.
z A sand flush gate should be located to one
side of the weir to release sediments
deposited upstream of the weir. The
intake is located at a side of the river just
upstream of the weir and to minimise
sand volume entering the intake. The
sill level of a sand flush gate is generally
set at 0.5 ~ 1.0 m higher than the original
riverbed level and 1.0 ~ 1.5 m lower than
the intake floor level.
z The skimmer wall at the entrance of the
inlet may be effective to prevent
driftwood or an excessive flood flow from
entering the intake.
z If slope failures or sediment yield are
confirmed in the upstream basin,
Weir
Intake
De-silting
Sand Flush Gate
Flow
Intake
Flood Water Level
Weir Crest
Weir
Sand Flush Gate
Intake
Int
Ga
EL.2
EL.3
Trashracks
Skimmar Wall
1.0 ~
1.5 m
Sand Flush Gate
Figure 2.1.5 Sand Flush Gate

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protection work such as a gabion wall may be effective to control the sediment
outflow.
z Flow velocity at the intake should be limited to 0.5 ~ 1.0 m/s to avoid sediment
flowing into the waterway.
Weir
z Types of weir are summarised as follows:
Table 2.1.1 Various Types of Weir
Type of Weir Specific Features Typical Figure
Concrete
gravity
z Applicable on rock
foundations
z Most commonly used
z Durable and impervious
z Relatively high cost
Floating
concrete weir
z Applicable on gravel
foundations
z Need an enough seepage path
z Durable
z Relatively high cost
Gabion covered
with concrete
z Applicable on gravel
foundation
z Surface protection by concrete
z Relatively low cost
Gabion z Applicable on gravel
foundation
z Flexible
z Low cost and easy
maintenance
Stone masonry z Applicable on gravel
foundation
z Low cost and easy
maintenance

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WL - Discharge Curve for
Spillway Discharge & Inflow into
Intake
691.2
691.4
691.6
691.8
692.0
692.2
692.4
692.6
692.8
693.0
0.0 2.0 4.0 6.0 8.0 10.0
Discharge (m3
/s)
WL. (m)
Inflow into
Intake
Flow over
Spillway
Figure 2.1.8
Example of Rating Curve
It should be noted that type of weir to be applied should be determined according to
the power scale, importance, flood discharge, foundation condition, and maintenance
requirements. The use of high quality materials and construction techniques will
result in less maintenance and repair work over the life of the scheme.
z The weir crest level of is normally designed equal to the Full Supply Water Level
(FSWL) under the maximum design
discharge.
z The hydraulic design of weir and intake
should be made appropriately to take the
proper discharge into the waterway. Since
the flow taken from a river is not regulated
in a run-of-river scheme, any excessive
water above the maximum design discharge
should be released safely from spillways.
When a weir crest is set equal to the FSWL at
the maximum design discharge, the inflow into
the intake can be divided into the following
cases:
1) (River flow) < (Maximum design discharge)
¾ Whole flow enters the intake.
¾ The water level varies between FSWL (EL.1)
and the intake floor level (EL.2)
¾ The maximum design discharge flows into
the intake at FSWL.
¾ The minimum flow to the downstream
basin shall be released from the river
outlet at any conditions if need be.
2) (River flow) > (Maximum design discharge)
¾ A water level is above FSWL (EL.1),
when a part discharge is spilt over the
weir and the remainder, that exceeds the
maximum design discharge, enters the
waterway.
¾ Any excessive discharge taken from the
intake should be released from a side
spillway , which needs to be provided at
a suitable location of the waterway.
B
H FSWL
FWL
SandFlush Gate EL.3
Spillway
Weir
EL. 2
EL. 1
Figure 2.1.6 Weir Level
EL. 3
Intake EL. 4
H SpillwayEL.1
FWL
Weir Profile
Intake
Figure 2.1.7 Weir Profile

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¾ The intake gate should be closed during a flood to avoid excessive sediment
inflow into the waterway.
z If a river water level is known from readings of a water level gauge provided at
the forebay, a discharge entering the waterway can be estimated by the following
sequences. Then, a rating curve (WL-Q) at the forebay can be prepared.
z Overflow discharge from spillway and outflow discharge through sand flush gate
can be calculated by the following formulas:
Discharge from a weir spillway where, Qspill : discharge from spillway (m3
/s)
B : width of spillway (m)
H = WL - Crest Level (m)
Discharge from a sand flush gate
1) For orifice flow Q : discharge through the gate (m3
/s)
A : Flow area (m2
)
H = WL – Centre level of orifice (m)
5
.
1
84
.
1 H
B
Qspill ⋅
⋅
=
H
g
A
Q ⋅
⋅
⋅
⋅
= 2
6
.
0
WLforebay is known
WL > FSWL
Overflow Discharge fromWeir
Qweir = C B (WL - FSWL)
1.5
Sequence to Estimate InflowDischarge into Intake
Whole flow enters the Intake
Yes No
Assume Discharge Qintake
Non-uniformflow analysis
fromHead Tank to Intake
WL > Spillway Crest
Yes
No
Calculation for Overflow
Discharge fromSide Spillway
No Overflow from
Side Spillway
WLintake = WLforebay
Assumption Qintake is correct
Yes
No
Figure 2.1.9 Flowchart to Estimate Inflow Discharge into Intake

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2) For pipe flow
fe : loss coefficient for entrance (0.1 ~ 0.5)
f : loss coefficient for friction = 124.5n2
L/D(4/3)
z In order to carry out the peak power generation in the dry season without
providing a regulating pond, a river channel storage may be effective if gates are
provided on the weir. The gates should be open in the rainy season and be
closed in the dry season if floods are not anticipated.
Intake
z Types of intake are summaried as follows:
f
f
H
g
A
Q
e +
+
⋅
⋅
⋅
=
1
2

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Table 2.1.2 Various Types of Intake
Type of
Intake
Specific Features Typical Figure
Side
Intake
with Weir
z Most commonly used for
run-of-river type power schemes
z Sand flush gate is located aside
the weir to release sediments
deposited upstream of the weir.
z Intake is located at a side of the
river just upstream of the
weir/sand flush gate.
z Intake gate is provided at
upstream section of de-silting
basin to close during sand drain
operation or maintenance of the
waterway.
Tyrolean
Type
Intake
z Suitable for steep rivers
containing boulders
z Weir is not necessary
z Necessary to remove drift
woods or leaves on the screen
z Necessary to remove fine sands
entered the intake
Intake to
Utilise
Pondage
z Applied to natural/artificial
ponds to utilise the water for
power generation
z The site selected for the headworks should be stable and suitable for reliable
foundations. All excess water and debris taken from the river needs to be
minimised in the design of headworks, and those entering during a flood flow
need to return to the river before entering the canal or penstock.
Weir
SandFlush Gate
Intake
Weir
Intake
De-silting Basin
Sand Flush Gate
Side Spillway
Waterway
Flow
Intake Gate

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Hydraulic requirements generally applied to side intake with concrete weir are
summarised as follows:
Flood Water Level
Weir Crest EL.5
Weir
Sand Flush Gate
Intake
De-silting Basin
Side Spillway
Power Canal
Sand Drain Gate
Intake
Gate
Schematic Profile of Intake Structures
EL.2
EL.3
1 : n1
EL.6
EL.7 1 : n2
Trashracks
Skimmer Wall
Figure 2.1.11 Schematic Profile of Intake Structures
Sample of Intake Plan
Weir
Sand FlushGate
De-silting Basin
Side Spillway
Power Canal
Sand Drain Gate
Intake Gate
Intake
Flow
Source: JICA Study Team, arranged from DHP drawing.
Figure 2.1.10 Sample of Intake Plan

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Table 2.1.3 Hydraulic Requirements Applied to Side Intake
Item General Application Symbol
Crest Level of Intake Weir = Full Supply Water Level EL. 1
Sill Level of Sand Flush
Gate
= Original River Bed + (0.5m ~ 1.0m) EL. 2
Floor Level of Intake = EL.2 + (1.0m ~ 1.5m) EL. 3
Velocity at Intake 0.5 ~ 1.0 m/sec approximately
Top of Intake Deck = Flood Water Level + freeboard ( > 1.0m) EL. 4
Top of Intake Gate = FSWL
Velocity at Intake Gate 1.0 ~1.5 m/sec approximately
Crest of Side Spillway = FSWL - (0 ~ 10 cm) EL. 5
Slope of De-silting Basin 1:10 ~ 1:30
Velocity in De-silting Basin < 0.3 m/sec
Length of De-silting Basin (2 ~ 3) x depth x velocity / sedimentation rate
= (2 ~ 3) x depth x 0.3 / 0.1 = (6 ~ 9) x depth
EL. of Sand Drain (Sand drain outlet level) > (Water level of the
river)
EL. 5
Floor Level of Power Canal = EL. 3 EL. 7
Slope of Power Canal 1:1,000 ~ 1:2,000
Velocity in Power Canal < 2 m/s maximum for lined canal

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FSWL
FWL
Skimmer Wall
v = 0.5 ~ 1.0 m/s
Figure 2.1.12
Front Elevation of
Skimmer Wall at Entrance
Flow
θ
b b
t
Thickness t = 5 ~ 9 mm
Width w = 50 ~ 120 mm
Interval b = 100 ~ 150 mm
Inclination θ = 60 ~ 70º
w
Figure 2.1.13 Trashracks
A skimmer wall at the entrance of the intake will be
effective not only to avoid driftwood entering or debris
floating into the intake, but also to restrict an excessive
inflow by making an orifice flow when the river water
level is higher than the Full Supply Water Level
(FSWL) during a flood.
An intake gate is provided at the upstream section of the
de-silting basin that can be closed during the sand drain
operation or maintenance of the waterway. The gate is
to be closed during floods to avoid excessive sediment
inflow. The velocity through the intake gate opening
should be limited to about 1.0 m/s.
Trashracks are provided at the entrance of the intake to
prevent trash, leaves, and floating debris from entering the
waterway. The screen bars are generally arranged with 5
~ 9 mm thick, 50 ~ 120 mm bar wide, 100 ~ 150 mm
intervals, and 60 ~ 70ºangle to the horizontal.

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Side Spillway
Intake
Gate
1 : 10 ~ 1 : 30
Trashracks
h
Ls
L
v < 0.3m/s
u
Slope 1 : 10 ~ 1 : 30
Side Spillway
Figure 2.2.1 De-silting Basin
2.2 De-silting Basin
z The de-silting basin is designed
to settle sands bigger than 0.5 ~
1.0 mm diameter of which the
settling velocity corresponds to
0.1 m/s. Average flow
velocity in a de-silting basin is
generally 0.3 m/s, and the
channel slope is 1/10 ~ 1/30.
The length of de-silting basin
is given by the following
empirical formula:
where, L : length of de-silting basin (m)
hs : depth of de-silting basin (m)
v : average velocity in de-silting basin (m/s) = Q / (B x hs) = 0.3 m/s
u : settling velocity for target sand particle (m/s) = 0.1 m/s for sand grains of
0.5 ~ 1.0 mm
A side spillway should be provided at the de-silting basin to release an excessive
inflow during a flood. The length required to overflow the excessive discharge and
the water surface profile can be computed by the following De-Marchi’s equations:
s
h
u
v
L ⋅
= )
3
~
2
(
Sand Drain
SandDrain Gate
Side Spillway
Figure 2.2.2 Side Spillway
Figure 2.2.3 Sand Drain Gate

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It is noted that the outflow path needs to be protected against scouring.
Figure 2.2.4 Overflow Discharge and Water Surface Profile in Side Spillway
)}
(
)
(
{
84
.
1
2 0
1
H
h
H
h
B
g
L φ
φ −
⋅
=
2
/
1
1
2
/
1
)
(
tan
3
)
(
3
2
w
h
h
H
w
h
h
H
w
H
w
H
−
−
−
−
−
−
−
= −
φ
2
/
3
)
(
84
.
1 w
h
q −
⋅
−
=
Where q : unit overflow discharge (m
3
/s/m)
h : depth of flow (m)
B : width of channel
w : height of weir (m)
h 0 : depth at downstreamsection (m)
h 1 : depth at upstreamsection (m)
H = h + Q
2
/{2g (B h )
2
} (m)
L
Flow h0
h1
h
w
x
0
B
OverflowDischarge & Water Surface Profile in Side Spillway

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2.3 Power Canal
Route Selection
z This section deals with open canals only, which are
most commonly applied to small/mini/micro
hydropower schemes, especially in Myanmar.
z A route for the power canal needs to be selected
after consideration of the topographic features along
the canal for the following points:
1) Stability against slope above and/or below the canal
2) Specific conditions such as streams, roads, and the
existing structures to be crossed
z Selection of the canal route and the design of canals
should be made in consideration of the fact that
the water level in a canal may rise for any of
several possible reasons:
1) When the canal flow is obstructed by a landslide or
closure of a gate at the downstream facilities
2) When excessive water enters the intake during a
flood.
3) When excessive running water is drained into the
canal during heavy rain
.
Weir
SandFlush Gate
Spillway
SandDrain
Spillway
Trashracks
Intake
Intake
Trashrack
SandDrain
De-silting Basin
Side Spillway
FSWL
B
Figure 2.3.1 Power Canal
Debris
Sliding of slope
by overflow
Sliding may be induced by overflow
from a canal in which debris enters
the canal.
Figure 2.3.2
Canal and Slope Failure
Side spillway to overflow excessive
inflow
Figure 2.3.3 Side Spillway

Nippon Koei / IEEJ
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z The following facilities for a canal may need to be designed for the above
conditions:
Table 2.3.1 Facilities for a Canal
Potential Landslide (a) Box culvert or canal cover (concrete/wood)
(b) Slope protection by structural reinforcement of the slope,
excavation in a gentler slope, and vegetation such as sodding or
planting
Crossing of stream
or valley
(a) Aqueduct to by-pass the flows from a flood or debris flow
(b) Siphon to path under the stream
(c) Drainage facilities to collect the running water in the catchment
basin and to release it safely to protect the canal from being
attacked or eroded by the drained flow or debris
Crossing of roads or
existing structures
(a) Box culvert or bridge to connect the existing road.
(b) Steel pipe or concrete conduit embedded under the existing
structures.
Excessive inflow (a) Side spillway to overflow the excessive flow over the max.
design discharge. An appropriate protection work against
scouring by the overflow is indispensable
(b) Drainage facilities to avoid excessive inflow into the canal
z When selecting the canal route, the existing
structures such as foot pass and irrigation channel
can be utilised to minimise the construction cost of
the canal as well as ease of access.
z Depending on the topographic conditions, it may be
possible to omit the power canal and the penstock
may be connected directly to the de-silting basin or
the head tank.
Existing footpath or irrigation canal
may be utilized for power canal
Figure 2.3.4 Existing Footpath

Nippon Koei / IEEJ
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Vmin = 0.3 m/s for sedimentation for flow carrying silty water
Vmin = 0.3 ~ 0.5 m/s for sedimentation for flow carrying fine sand
Vmin = 0.7 m/s to prevent aquatic plants
Canal Dimensions
z Power canals are to be designed in consideration of
1) flow capacity, 2) velocity, 3) roughness, 4) slope,
5) sectional shape, 6) lining (with or without,
material), and 5) maintenance.
z The velocity in a canal should be low enough to
prevent erosion of the canal, especially if it is
unlined, and to keep effective head as high as
possible.
z The velocity in a canal should be high enough to
prevent sedimentation and to avoid the growth of
aquatic plants especially in unlined earth canals.
z Maximum permissible velocities for unlined canals to avoid erosion are given as
follows:
Table 2.3.2 Velocities for Unlined Canals
Material n Vmax
(m/s)
Permeability
(x 10-6
m3
/s/m2
)
Fine sand 0.020 - 0.025 0.3 – 0.4 > 8.3
Sandy loam 0.020 - 0.025 0.4 – 0.6 2.8 – 8.3
Clayey loam 0.020 - 0.025 0.6 – 0.8 1.4 – 2.8
Clay 0.020 - 0.025 0.8 – 2.0 0.3 – 1.4
z For a lined canal, wear of abrasion sets the upper limit on velocity. Velocities
above 10 m/s will not damage a concrete lined canal when the water is clear, but
velocities above 4 m/s containing sand and
gravel may scour the lining.
z The steeper the slope of the canal, the
smaller the sectional area required; however
the effective head is decreased. The best
combination of a canal size and a slope
should be examined within a suitable range
of flow velocity.
z The maximum velocity in a lined canal is
normally smaller than 2.0 m/s.
Omission of canal, and utilization of
existing structures
Figure 2.3.5
Structure without Canal
Figure2.3.6
Stone Masonry Canal
Stone-masonry canal with screen

Nippon Koei / IEEJ
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B
Figure 2.3.8
Side Channel Spillway
z A canal slope, depending on the topographic conditions, is generally as follows:
1/500 ~ 1/1,000 : to minimise the canal size in
high head plant
1/1,000 ~ 1/1,500 : general application
1/1,500 ~ 1/2,000 : to minimise a head drawdown
in low head plant
z Roughness coefficient “n” is an empirical
measure of surface roughness of a waterway.
The following values are usually applied :
Steel : 0.012 ~ 0.013
Concrete : 0.014 ± 0.001
Stone-masonry : 0.016 ~ 0.020
z For unlined canals, a trapezoid cross-section is the
most common. Side slopes of a canal are 1.0
(V):0.5 (H) for rock foundation, and 1.0(V):2.0(H)
for sandy loam foundation.
z For lined canals, a rectangular or a trapezoid
cross-section is commonly used for stone masonry
lining, and a rectangular section for concrete
lining.
z A side channel spillway is generally provided at
the de-silting basin and the head tank; however, it
may be necessary to be designed in a suitable
section of the power canal depending on the design
conditions. The outflow path needs to be protected
against scouring.
Water Surface Profile
z The canal floor elevation at the downstream end
(EL.4 in the figure) is commonly fixed to provide
a uniform flow depth for the maximum design
discharge when the water level in the head tank or
the regulating pond is at the Full Supply Water
Level (FSWL). In this condition, the flow depth
in the canal is uniform over the whole stretch if the canal slope is uniform.
EL. 4
FSWL
Uniform depth for
design discharge
Uniform flow state at the downstream
end of the canal at FSWL
Figure 2.3.9 Water
Surface : Uniform Flow
Properly designed lined canal reduces
the canal size and the excavation
volume to convey the same discharge
Figure 2.3.7 Canal Design

Nippon Koei / IEEJ
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z A non-uniform flow analysis should be carried out in the full section of the
waterway starting from the head tank or the regulating pond up to the intake,
varying parameters such as discharge, roughness coefficient, and the initial water
level at the head tank. The wall height of the canal is to be designed so that the
energy line for the maximum inflow into the canal should be lower than the wall
crest.
z Uniform flow depth in a canal can be calculated by Manning’s Formula:
Uniform flow analyses can be made by the computer programs attached in
Appendix 2-1.
z Non-uniform flow analysis involves solving the following differential equation:
Non-uniform flow analysis can be made by the computer programs attached in
Appendix 2-2.
Lining Types
z The lining type of earth canal has the following characteristics: (a) easy for
construction and maintenance, (b) low cost, (c) not applicable to pervious and
erosive foundation, (c) velocity < 0.3 m/s, (d) roughness coefficient n = 0.014 on
an average, seepage loss = 1.0 (clay) ~ 8.0 (sand) x 10-6
m3
/s/m2
z The lining type of stone masonry canal has the following characteristics:(a) easy
for construction and maintenance, (b) velocity <1.5 m/s (dry stone masonry) and
velocity <2.0 m/s (wet stone masonry), (c) roughness coefficient n = 0.032 (dry
stone masonry) and roughness coefficient n = 0.025 (wet stone masonry)
h
A
gA
Q
A
Q
R
n
x
b
b
A
gA
Q
i
dx
dh
∂
−
−
∂
∂
∂
∂
+
=
α
α
α
3
2
2
3
4
2
3
2
1
)
(
For a rectangular section
For a triangular section
where, Q : discharge (m
3
/s), n : roughness coefficient, b : width of canal (m)
h : depth of flow (m), R : hydraulic radius (m), I : slope of canal
2
1
3
2
I
R
n
A
Q = A
V
Q ⋅
=
h
b
A ⋅
=
b
h
h
R
2
1+
=
)
( mh
b
h
A +
= 2
1
2
)
(
m
h
b
mh
b
h
R
+
+
+
=
h
b
h
1
m
b
Figure 2.3.10 Discharge Calculation

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Flow & Debris
Power Canal
Figure 2.3.12
Cross Drain under Power Canal
Power Canal
Figure 2.3.13
Cross Drain over Power Canal
z The lining type of concrete lining canal has the following characteristics: (a)
durable, (b) relatively high cost, (c) velocity < 3.0 m/s, (d) roughness coefficient n
= 0.015 on an average.
Cross Drain
If a power canal passes through valleys with catchment areas, drain facilities that cross
under or over the power canal should be provided to protect the canal structure from
attack from running water with containing debris during rainfall. Box culverts,
concrete pipes, polyethylene pipes, etc. are used as under drains, and open chutes as
over drains. Under drains need adequate flow area, since they are likely to be
clogged with debris, soil, etc. A minimum inner space of 60 cm is preferable for
manual cleaning.
z Slope steeper than 1/50
z Size bigger than φ 60cm
z Enough flow area not to be clogged
z Maintenance for clogging
Stone Masonry Canal Concrete Canal
Earth Canal
Figure 2.3.11 Type of Canal Lining

Nippon Koei / IEEJ
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Figure 2.4.2
Head Tank with Spillway
2.4 Head Tank
Site Selection
z A head tank is provided between a power canal
and a penstock pipe to adjust a turbine discharge
corresponding to the load fluctuation, while a
surge tank is required when a pressure tunnel or
conduit is applied as headrace. When a penstock
pipe is connected directly to a de-silting basin, a
de-silting basin may be designed to have functions
of a head tank.
z The location of a head tank is selected generally to
be on a ridge with firm foundations, depending on the topographical and
geological conditions.
z A spillway and a sand drain gate should be considered and incorporated into the
head tank.
z When a spillway is provided (it may be omitted under some conditions), the route
of the spillway should be properly designed so as to not cause sliding or erosion
of the slope.
Hydraulic Design
z The capacity of the head tank is determined according to the responsive
characteristics of the governors installed in the power plant.
1) Mechanical governors and manual operation
Where,
V : capacity of tank (m3
)
A : surface area of tank (m2
)
Qmax : max.design discharge (m3
/s)
V > (Qmax) x (120 ~ 180)
Weir
SandFlush Gate
Spillway
SandDrain
Spillway
Trashracks
Intake
Intake
Trashrack
SandDrain
De-silting Basin
Side Spillway
FSWL
B
Figure 2.4.1 Head Tank

Nippon Koei / IEEJ
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Where, Q : spill-out discharge (m3
/s)
Bs : length of spillway (m)
H : overflow depth (m)
2) Electric governor, computer governor and dummy load governor
z Spillway discharge can be calculated as follows:
z A discharge capacity of sand drain gate is calculated by the following formulas:
1) For orifice flow
Where,
Q : discharge through the gate (m3
/s)
A : Flow area (m2
)
H = WL – Centre level of orifice (m)
2) For pipe flow
fe : loss coefficient for entrance (0.1 ~ 0.5)
fb : loss coefficient for bend
={0.131+0.1632(D/R)3.5
} (θ/90)0.5
D : pipe diameter (m)
R : radius of curvature (m)
θ : bend angle (º)
f : loss coefficient for friction = 124.5n2
L/D(4/3)
L : length of pipe
z Water depth between the Minimum Operational Level (MOL) and the centre level
of the penstock inlet is given by the following:
Power Canal Head Tank
Sand Drain Gate
Spillway
Trashracks
φ
Bs h
FSWL
MOL
30 ~ 50 cm
Uniform flow
depth at Qdesign
Penstock Gate
Air Vent Pipe
Figure 2.4.3 Head Tank
V > (Qmax) x 20 sec +A x 0.8
5
.
1
84
.
1 H
Bs
Q ⋅
⋅
=
H
g
A
Q ⋅
⋅
⋅
⋅
= 2
6
.
0
f
f
f
H
g
A
Q
b
e +
+
+
⋅
⋅
⋅
=
1
2

Nippon Koei / IEEJ
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Where, h : depth between MOL and pipe centre (m)
φ : diameter of penstock pipe (m)
z An air vent pipe is required when the inlet gate is provided on the inlet of the
penstock. The diameter of the air vent pipe is given by the following empirical
formula:
Where, φ : diameter of air vent pipe (m)
P : power output (kW)
L : length of air vent pipe (m)
H : head of penstock (m)
z The sectional shapes of head tank should be designed to avoid any abrupt changes
that can cause the occurrence of a vortex.
z An average slope of head tank is 1/15 ~ 1/50 in order to drain the sediment
deposited in the tank through a sand drain gate.
Omission of Spillway
z The spillway of the head tank can be omitted when the discharge is regulated in
the intake and the following conditions are applied:
1) Deflectors are attached for Pelton or Turgo Impulse type turbines.
2) An outlet valve, branched from the penstock pipe, is provided to release the
discharge during load rejection. The valve opening is connected with the closure of
the guide vane.
3) A dummy load governor, which is applied to mini/micro hydropower schemes
smaller than 300 kW, is provided to respond to load rejection.
h > φ (φ < 1.0 m)
h > φ2
(φ > 1.0 m)
273
.
0
2
)
(
0068
.
0
H
L
P
=
φ

Nippon Koei / IEEJ
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Manuals Part 2
1 2 3 4 5 6 7 8 9 10 11 12
River Discharge
Irrigation water
Max. turbine discharge
with pondage
Max. turbine discharge
without pondage
Required pond
capacity
Q
(m3
/s)
Available power
Discharge
Figure 2.5.1 Pondage Capacity
2.5 Regulating Pond
z A regulating pond is provided
for daily peak power
generation, of which the
location is selected at a flat
area to accommodate the
required pond capacity, which
needs to be enough to meet a
power demand, especially
during a dry season.
z The pondage capacity should
be determined to allow supply,
with a supplementary discharge
during a target operation period of time when the available discharge is
insufficient for the power demand, while reserving the available water during the
rest of the day.
z The peak power operation can be made by monitoring the water level gauge to be
equipped in the pondage. Inflow discharges can be estimated by the following
equations:
z The following is an example of inflow estimate:
600
,
3
)
(
)
( ⋅
−
=
⋅
=
⋅
= out
in Q
Q
dt
dH
H
S
dt
dH
dH
dV
dt
dV
)
(
600
,
3
)
(
H
S
Q
Q
dt
dH out
in ⋅
−
=
out
in Q
H
S
dt
dH
Q +
⋅
=
600
,
3
)
(
Where, H : Water level in the pond (m)
dH/dt : Fluctuation of water level in
the pond in one hour (m/hour)
Qin : Inflow into the pond (m3
/s)
Qout : Turbine discharge (m3
/s)
S(H) : Surface area of the pond at
water level of H (m2
), which
is expressed as (aH2
+ bH + c)

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Nomogram for Inflow Estimation
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
2-unit operation
1-unit operation
dH/hour : fluctuation of water level in 1 hour
Average water level : EL.687.000
Qin (m3
/s)
dH/hour (m/hour)
z The opening degree of the guide-vanes are to be kept constant during the time on
peak.
Sand Flushing through the ‘Saxophone’ Suction Head
z To utilise a head between the pondage and outlet without using other energy such
as electricity or diesel.
z Sand flushing can be made under power generation, therefore it is not necessary
to stop power generation during a sand flushing operation.
z There is a experimental data reported that about 10% of the sand volume density
can be flushed. However, it is noted that such a flushing percentage is subject to
the nature of sediment deposit.
z It is reported that this metod is suitable to flush sediment in a pondage or a
de-silting basin where sediment is light and particle size small. Consequently,
simple and small-scale flushing facilities are needed for such a pondage or a
de-silting basin.
1) Power operation with 2-unit (320 kW,
Qout=0.65 m3
/s)
2) 2) Reading of water level in the pond by
pressure gauge
3) 3) When fluctuation of water level during 1.0
hour is -0.35m , and average water level is
687.000m under 2-unit operation
Qin = -0.35 x (687.000 - 661.000) x (687.000 -
586.000) / 3,600 + 0.65 = 0.395 m3
/s
Figure 2.5.2 Inflow Estimation

Nippon Koei / IEEJ
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Example:
z Pipe φ = 15 cm, L = 20 m
f
f
N
f
H
g
V
b
e +
⋅
+
+
⋅
=
1
2
fe = 1.00 (inlet loss), N·fb = 0.40 (bend loss), f = fr(L/D)=4.5 (friction loss)
fr = 12.7g・n2
・D1/3
= 0.03373 and n = 0.012 (roughness coefficient)
When H (head) = 1.5 m, V (velocity) = 2.06 m/s,
z Pipe φ = 15 cm, L = 20 m, H = 1.5 m, V = 2.06 m/s
Q = 0.036 m3
/s (= 2.19 m3
/min = 131 m3
/hr) : discharge flushed
Sand= 131 m3
/hr x 10%*1
= 13.1 m3
/hr (= 315 m3
/day*2
): sand volume flushed
Note:
*1
: In reference to the experimental data as a calculation example.
*2
: In application of 24 hours as a calculation example for the daily working
hours of the sand flushing device.
Head
Open Slots
Sediments
Source: D.K.Lysne, New Norwegian Institute of Technology
Figure 2.5.3 'Saxophone' Sand Flushing

Nippon Koei / IEEJ
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Table 2.5.1 Sand Flushing Capacity of 'Saxophone' Suction Head
Dia. L H V Q Q Sand Sand
(m) (m) (m) (m/s) (m3
/s) (m3
/hr) (m3
/hr) (m3
/day)
0.1 10 1.5 2.17 0.017 61 6.1 146
0.1 10 3 3.06 0.024 86 8.6 206
0.1 20 1.5 1.7 0.013 47 4.7 113
0.1 20 3 2.41 0.019 68 6.8 163
0.1 30 1.5 1.45 0.011 40 4 96
0.1 30 3 2.05 0.016 58 5.8 139
0.1 40 1.5 1.28 0.01 36 3.6 86
0.1 40 3 1.82 0.014 50 5 120
0.1 50 1.5 1.16 0.009 32 3.2 77
0.1 50 3 1.65 0.013 47 4.7 113
0.1 60 1.5 1.07 0.008 29 2.9 70
0.1 60 3 1.52 0.012 43 4.3 103
0.15 10 1.5 2.51 0.044 158 15.8 379
0.15 10 3 3.56 0.063 227 22.7 545
0.15 20 1.5 2.06 0.036 130 13 312
0.15 20 3 2.92 0.052 187 18.7 449
0.15 30 1.5 1.79 0.032 115 11.5 276
0.15 30 3 2.54 0.045 162 16.2 389
0.15 40 1.5 1.61 0.028 101 10.1 242
0.15 40 3 2.27 0.04 144 14.4 346
0.15 50 1.5 1.47 0.026 94 9.4 226
0.15 50 3 2.08 0.037 133 13.3 319
0.15 60 1.5 1.36 0.024 86 8.6 206
0.15 60 3 1.92 0.034 122 12.2 293

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2.6 Penstock
z Alignment of the penstock should be designed to be located below the minimum
hydraulic grade line during the load rejection to avoid negative pressure.
Penstock Powerhouse
TWL
Static Head
Anchor Block
Spillway
HeadTank
SandDrain Gate
Trashracks
FSWL
MOL
Hydraulic Grade Lines
Max. Pressure Rise
Min. Pressure Drawdown >
Penstock Elevation
50 ~ 100 m max.
Max. velocity
2.5 m/s (inlet) ~
5.0 m/s (outlet)
55º max.
Figure 2.6.1 Penstock
Negtive pressure occurs
Hydraulic Grade
Line

Nippon Koei / IEEJ
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z Types of Penstock are summarised as follows:
Table 2.6.1 Types and Features of Penstock
Type Features
Open type
z Most commonly applied to small hydro schemes
z Anchor blocks are provided at bend portions, which should be founded
on firm foundations enough to support the blocks with penstock pipes
against sliding, over turning and bearing.
z Interval of each anchor block should be less than 100 m generally.
z Saddle piers are provided at 6 m interval.
z Maximum angle of pipe inclination should be 55°
z Drainage and slope protection should be considered for the open
excavated areas.
z Expansion joints just below the head tank and between each anchor.
z Bitumen between pipes and anchors/saddles to avoid corrosion.
Buried type z Applicable to the following conditions:
(a) soft foundations not to support the anchor blocks
(b) areas susceptible to attack of landslides or running water
(c) gentle slopes to keep the stability of backfill materials
z Steel pipes should be galvanised, and double coated with either bitumen
or high zinc content paint.
Tunnel type z Generally not applied in small/mini hydropower schemes.
x
y
α2
α1
L1
l1
l2
L2
φ1
φ2
O
O
ψ
O2
O4
Anchor Block
Saddle
w
b
b
Fille
60°

Nippon Koei / IEEJ
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Water hammer analysis
Water hammer can be computed by the Allievi’s Equations for simple penstock
pipes without branches. The computer programs and the example are attached in
Appendix 2-7 of Part 6-2 in Volume 6..
Wave Velocity of Water Hammer
Equivalent Sectional Area
Equivalent Wave Velocity
Allievi's Equations
(1) 1st phase
(2) after 2nd phase
]
1
1
[
1
0
t
D
E
K
g
w
a
⋅
+
=
∑
∑
=
)
( i
i
i
m
A
L
L
A
∑
∑
=
)
( i
i
i
m
a
L
L
a
)
1
(
2
1 '
1
1
'
1 H
H ψ
ρ −
⋅
=
−
0
0
2 H
g
V
a
⋅
⋅
=
ρ
µ
⋅
−
+
= )
1
(
1 i
t
ti
T
i
i
µ
ψ
⋅
−
= 1
a
L
2
=
µ
0
0
'
H
H
h
H i
i
+
=
0
0
2 H
g
V
a
⋅
⋅
=
ρ
0
)
2
1
(
)
4
4
2
( 2
'
1
2
1
2
2
'
1 =
+
+
+
+
− ρ
ψ
ρ
ρ H
H
)
(
2
2 '
'
1
1
'
'
1 i
i
i
i
i
i H
H
H
H ψ
ψ
ρ −
⋅
=
−
+ −
−
−
0
)
2
( 2
'
2
'
=
+
⋅
−
− A
H
A
B
H i
i
'
1
1
'
1 2
2 −
−
− −
−
= i
i
i H
H
A ρψ
2
)
2
( i
B ρψ
=
r
t
Penstock Powerhouse
TWL
HeadTank
FSWL Max. Pressure Rise
Static Head
Water Hammer at Turbine
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0 2 4 6 8 10 12 14
Time (sec)
H/H0
Figure 2.6.2 Water Hammer Analysis

Nippon Koei / IEEJ
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Head loss
An effective head to be used for the estimate of power output can be obtained
from a head difference between Full Supply Water Level (FSWL) at the head
tank and Tail Water Level (TWL) at the powerhouse after deducting head losses.
The head losses between the head tank and the powerhouse are expressed as
follows:
(1) Velocity Head in Head Tank
(2) Head Loss at Trashracks
V1
θ
b b
t
g
v
f
h r
2
2
1
2 ⋅
=
g
v
h in
2
2
1 = Vin : velocity in head tank
3
4
)
)(
(sin
34
.
2
b
t
fr θ
=
h2 : head loss of trashracks (m)
fr : head loss coefficient
V1 : velocity before trashracks (m/s)
θ : inclination of trashracks (º) θ = 60 ~ 70º
t : width of bar (mm) t = 5 ~ 9 mm
b : space between bars (mm) b = 100 ~
h2 : head loss of trashracks (m)
fr : head loss coefficient
V1 : velocity before trashracks (m/s)
θ : inclination of trashracks (º) θ = 60 ~ 70º
t : width of bar (mm) t = 5 ~ 9 mm
b : space between bars (mm) b = 100 ~ 150 mm
Penstock
TWL
Anchor Block
HeadTank
Trashracks
Powerhouse
FSWL vin
2
/2g
vin
vout
vout
2
/2g
FSWL
Figure 2.6.3 Head Loss
Figure 2.6.4 Head Loss of Trashrack

Nippon Koei / IEEJ
Volume 4
Manuals Part 2
(3) Head Loss at Penstock Inlet
(4) Head Loss due to Friction in Pipe
(5) Head Loss due to Bend
(6) Head Loss due to Pipe Reducer
(7) Head Loss due to Branch
g
v
f
h e
2
2
2
3 ⋅
=
fe = 0.25 fe = 0.2
fe = 0.5
v2 v2 v2
h3 : head loss at entrance (m)
fe : head loss coefficient of entrance
v2 : velocity after entrance (m/s)
g
v
L
D
n
h
2
5
.
124 2
3
4
2
4 =
h4 : head loss due to friction (m)
n : roughness coefficient of pipe
≈ 0.012
L : pipe length (m)
v : velocity in pipe (m/s)
g
v
R
D
h
2
)
90
(
}
)
(
1632
.
0
131
.
0
{
2
5
.
0
5
.
3
5 ⋅
⋅
⋅
+
=
θ
h5 : head loss due to bend (m)
R : bend radius (m)
θ : bend angle (º)
v : velocity in pipe (m/s)
θ
R
D
v
g
v
f
h gc
2
2
2
6 =
h6 : head loss due to pipe reducer (m)
fgc : head loss coefficient of reducer
θ : reducer angle (º)
L : reducer length (m)
v1 : velocity before reducer (m/s)
v2 : velocity after reducer (m/s)
v1
v2
A1 A2
θ
L
Figure 2.6.5 Head Loss of Penstock Inlet
θ º
fgc
Source: Hatsuen Suiryoku Ensyuu
Figure 2.6.6
Head Loss Coefficient for Reducer

Nippon Koei / IEEJ
Volume 4
Manuals Part 2
(8) Head Loss due to Inlet Valve
(9) Enlargement at Outlet
A sample calculation sheet for head losses is attached in Appendix 2-3 of Part
6-2 in Volume 6.
g
v
f
h v
2
2
8 ⋅
=
g
v
f
h b
2
2
1
7 ⋅
=
h7 : head loss due to branch (m)
fb : head loss coefficient of branch
v1 : velocity before branch (m/s)
(a) : fb = 0.75
(b) : fb = 0.50
h8 : head loss due to inlet valve (m)
fv : head loss coefficient of valve
v : velocity at inlet valve (m/s)
Sluice valve (full open) : fv = 0
Butterfly valve: fv = t/d
t: Thickness of valve circle end
d: Diameter of valve circle
g
v
A
A
h
2
)}
(
1
{
2
1
2
2
1
9 ⋅
−
= v1 v2 A2
A1
h9 : head loss due to enlargement (m)
A1 : flow area before enlargement (m2
)
A2 : flow area after enlargement (m2
)
v1 : velocity before enlargement (m/s)
(a) (b)

Nippon Koei / IEEJ
Volume 4
Manuals Part 2
TWL FWL
Freeboard
Drainage
System
Access Road
Slope
protection
Firm Foundation
Figure 2.7.1 Powerhouse
2.7 Powerhouse
Site Selection
z The location of the powerhouse
should be selected taking into
account the following conditions:
(1)Access
Easy access is required for the operation
and maintenance after completion.
(2)Foundation
Rock foundations are preferable but a
well consolidated foundation to support the equipment load of 5 ton/m2
will be
acceptable.
(3)Safety against flooding and land sliding
The floor elevation of the powerhouse should be higher than the flood water
level of the river downstream, and the slopes surrounding the powerhouse should
be stabilised if required.
(4)Drainage
The drainage facilities around the powerhouse should be properly designed to
protect the powerhouse from attack from of water rush flow from the slopes and
inundation during heavy rain.
z Tail Water Level (TWL) at the powerhouse should be determined so that it
will not be affected by the backwater from the river during a flood.

tailwater level.pdf

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