IWA 33-2:2019

INTERNATIONAL IWA
WORKSHOP 33-2
AGREEMENT
First edition
2019-12
Technical guidelines for the
development of small hydropower
plants —
Part 2:
Site selection planning
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Planning principles . 1
5 Planning scope . 2
6 Planning methods and steps . 2
7 Basic data collection and analysis . 3
7.1 Data collection . 3
7.2 Data analysis . 4
8 Computation of river basin or sub-basin hydropower potential . 5
9 Preliminary planning of site . 7
9.1 Planning content and main considerations . 7
9.2 Types of SHP stations and applicable conditions for development . 7
9.2.1 Dam-type hydropower station . 7
9.2.2 Diversion-conduit-type hydropower station . 7
9.2.3 Reservoir-based, run-of-river hydropower station (hybrid) . 8
9.3 Utilization of several special geographical conditions of rivers . 8
9.3.1 Utilization of natural waterfalls . 8
9.3.2 Utilization of rapids or natural waterfalls . 8
9.3.3 Utilization of river bends . 8
9.3.4 Utilization of the fall on an irrigation channel . 8
9.3.5 Utilization of kinetic energy of flowing waters in a river or canal . 8
9.4 Estimation of the development scale of a hydropower station . 8
10 Site surveys and investigations. 9
10.1 Hydrological surveys . 9
10.2 Surveys on the planning site .10
10.2.1 Dam site surveys .10
10.2.2 Plant site surveys .10
10.2.3 Water conveyance line surveys .10
10.2.4 Reservoir survey .10
10.3 Preliminary determination of available water heads for the hydropower station .10
10.4 Other construction conditions for investigation .10
11 Preparation of site construction plan .11
11.1 Selection of installed capacity .11
11.2 Selection of turbine types .11
11.3 Number of units .11
11.4 Selection of dam type .11
11.5 Selection of spillway structures.12
11.6 Selection of water intake structures .12
11.7 Selection of diversion structures .12
11.8 Types of powerhouse .13
11.9 Location of switchyard .13
11.10 Location of tailrace .13
11.11 Layout of main structures .13
12 Preliminary assessment of social and environmental impacts .13
13 Assessment of power demand .14
14 Cost estimation and benefits assessments .14
15 Evaluation of planning site and development sequence recommendations.15
16 Preparation of site selection planning report .15
Annex A (informative) Computation of theoretical potential of river water energy,
estimation formula for installed capacity on a planned site .16
Annex B (informative) Schematic diagram of development types and special terrain
utilization of SHP stations.19
Annex C (informative) Outline of a site selection planning report .24
Annex D (informative) Workshop contributors .29
iv © ISO 2019 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
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expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
International Workshop Agreement IWA 33 was approved at a workshop hosted by the Standardization
Administration of China (SAC) and Austrian Standards International (ASI), in association with the
International Center on Small Hydro Power (ICSHP), held in Hangzhou, China, in June, 2019.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
A list of all parts in the IWA 33 series can be found on the ISO website.
Introduction
Small hydropower (SHP) is increasingly recognized as an important renewable energy solution to
the challenge of electrifying remote rural areas. However, while most countries in Europe, in North
and South America and in China have high degrees of installed capacity, the potential of SHP in many
developing countries remains untapped and is hindered by a number of factors including the lack of
globally agreed good practices or standards for SHP development.
The technical guidelines for the development of small hydropower plants contained in this document
address the current limitations of the regulations applied to technical guidelines for SHP plants by
applying the expertise and best practices that exist across the globe. It is intended for countries to
utilize this document to support their current policy, technology and ecosystems. Countries that have
limited institutional and technical capacities will be able to enhance their knowledge base in developing
SHP plants, thereby attracting more investment in SHP projects, encouraging favourable policies and
subsequently assisting in economic development at a national level. This document will be valuable for
all countries, but especially allow for the sharing of experience and best practices between countries
that have limited technical know-how.
This document is the result of a collaborative effort between the United Nations Industrial Development
Organization (UNIDO) and the International Network on Small Hydro Power (INSHP). About 80
international experts and 40 international agencies were involved in this document’s preparation
and peer review. This document can be used as the principles and basis for the planning, design,
construction and management of SHP plants up to 30 MW.
vi © ISO 2019 – All rights reserved

International Workshop Agreement IWA 33-2:2019(E)
Technical guidelines for the development of small
hydropower plants —
Part 2:
Site selection planning
1 Scope
This document specifies the general principles of site selection planning for small hydropower (SHP)
projects, and the methodologies, procedures and outcome requirements of SHP plant site selection.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
IWA 33-1, Technical guidelines for the development of small hydropower plants — Part 1: Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IWA 33-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Planning principles
4.1 Site selection shall be carried out in accordance with the laws and regulations of the relevant state/
provinces/country.
4.2 Site selection shall follow the principles of localized planning, subject to overall national integrated
water resources planning and to comprehensive river basin planning with the systematic prospection of
potential sites.
4.3 Site selection shall meet the requirements of the environmental needs of the river and surrounding
areas and also have preliminary plans to mitigate the negative impacts likely to be caused by the SHP
projects to the river and its surrounding environment.
4.4 Site selection shall be determined based on the water resources and topography with the purpose
of sustainable development, utilization, and along with comprehensive consideration of all other factors.
4.5 Site selection shall consider comprehensively the correlation of hydropower resource development
over the entire length of the river, with due attention to the interrelationship of upstream and downstream
cascade development, so that the layout of upstream and downstream sites are properly coordinated.
For multipurpose requirements for water supply, flood control, irrigation, ecology, tourism, navigation
and community development, the SHP projects shall be planned in accordance with the primary and
secondary development purposes.
4.6 Site selection shall take into account the long-term electricity demand projection based on the
social and economic development of the area. Where indirect selling of electricity to other region(s) is
foreseen through the power grid, the current status and development plan of the grid shall be considered,
and the growth potential of the external power market shall be evaluated. According to the development
needs of the power market, planning should be carried out accordingly to meet the relevant short-,
medium- and long-term development goals.
4.7 Site selection shall make a justification of the selection of SHP in relation to other possible rural
electrification technologies.
4.8 Site selection shall take into account relevant local, regional and international integrated
development plans relevant to the area under study.
4.9 Site selection shall be coordinated with other relevant development plans of the area under study,
including planning indicators, terminology, units of quantities and values, implementation plans, and
shall be consistent and avoid conflicts.
5 Planning scope
5.1 The planning scope for site selection of SHP development shall be based on the level (local/state/
national) of the planning organization of the country.
5.2 If the SHP resource development plan is part of the comprehensive planning of the administrative
area (local/state/provinces), the scope of the site selection planning shall be defined in accordance with
the administrative divisional plan.
5.3 SHP development planning shall be based on the detailed and homogeneous definition of the river
network and catchments in the river basins.
5.4 Within exclusive economic development zone and nature reserve areas, site selection planning of
SHP development shall consider the multipurpose needs.
6 Planning methods and steps
The methods and steps described in Clauses 7 to 16 shall be taken according to the actual process of
site selection planning of SHP resource development (see Figure 1).
2 © ISO 2019 – All rights reserved

Figure 1 — Flow chart of activities for SHP site selection planning
7 Basic data collection and analysis
7.1 Data collection
7.1.1 Adequate basic data shall be collected and analysed. Consideration shall be given to the use
of digital natural resource databases and geomatics technology (remote sensing and Geographical
Information System [GIS]). The authenticity, accuracy, timeliness and applicability of the collected data
shall be tested and confirmed.
7.1.2 The following basic data shall be included.
a) Hydrometeorological data, including series of measured data, such as precipitation, flow in rivers,
evaporation, water level, sediment and ice. For the locations lacking the measured data, relevant
data on adjacent river basins and hydrological maps issued by the national or regional authority
should be collected.
b) Data of natural geography of river basin and river characteristics, including the topographic map
of the river basin (scale not less than 1:50 000), road map of administrative area, longitudinal and
cross-sections of river. Data on digital elevation/terrain models are available at 30 m, and better
resolution may also be used. If the hydro-meteorological data of adjacent river basins needs to be
utilized, the topographic maps of adjacent river basins shall also be collected.
c) Geological data, including regional geological, tectonic, seismic zoning maps, geological reports,
and records of major geological events such as earthquakes in the planning area.
d) Resource information, including land use, minerals, energy, forestry, tourism, rare animals and plants.
e) Power system data, including power source, power demand, annual power supply, load structure,
load curve, power grid structure, power markets, regulations and power-development planning in
the area.
f) Existing facilities data, including as-built design documents of existing hydropower stations,
irrigation, water supply, rafting, navigation and other projects within the planning river reach.
g) Socio-economic data, including the demography, industrial and agricultural production, road
network, gross national product, per capita income, and national economic development plans in
the area.
h) Other data, including natural disaster records, legal requirements, archaeology, historic sites,
protected areas and natural heritage.
7.2 Data analysis
7.2.1 Analysis of hydrometeorological data shall include the following.
a) Qualitative analysis
1) The data series shall be accurate, reliable and have no data gaps as far as possible.
2) The data shall be applicable to the river basins under study.
3) The accuracy of the data shall meet the analysis requirements. The precipitation/rainfall data
should be, as far as possible, “daily rainfall”. The measured data of flow shall be as precise as
“average daily flow”.
4) Appropriate analytical methods shall be used for quality control.
5) A reliable long-term daily discharge series specific to every river reach in the network should
be determined, based on distributed hydrologic modelling that is appropriately calibrated.
b) Quantitative analysis
1) Frequency analysis: The measured flow data series should be analysed and calculated
according to the probability formula of statistics, and the frequency curve should be drawn
according to the analytical results.
2) Correlation analysis: Correlation analysis shall be done when the measured flow data are not
on the location of the selected site for SHP development.
3) Average flow duration curve: Based on the data of frequency computation, select the flows
corresponding to the frequency of high flow, median flow and low flow. Then select a similar
4 © ISO 2019 – All rights reserved

year from the flow series for annual distribution, if available, and distribute the average daily
flow within the next three years, plotted as an "average flow duration curve ".
7.2.2 Topographic map data analysis shall include the following.
a) Scope analysis: The topographic map shall include the drainage area of the river basin under study.
If rainfall or flow data of adjacent river basins are utilized, the topographic map shall also provide
the drainage area of the adjacent river basin.
b) Accuracy analysis: The scale of the topographic map used for the site selection should be no less than
1:50 000. If the scale of the collected topographic map is smaller than the specified requirements,
encryption measures shall be taken to improve the accuracy of contours. Global geometric data of
30 m or better resolution may also be used.
7.2.3 Geological data analysis shall meet the following requirements.
a) Incorporating the conclusions of the regional geological structural stability assessment, major fault
lines and the ground motion parameters determined for the project area.
b) It can reflect regional topography and geomorphology, stratigraphic lithology, geological structure,
hydrogeological conditions and physical geological phenomena.
7.2.4 Power system data analysis shall include the following.
a) Present status of the power grid and analysis of the power grid plan: including power grid structure,
geographical distribution, voltage levels and the relationship with, and impact on, proposed and
planned SHP development.
b) Power source and demand (load) status and planning analysis: including power source and demand
(load) structure, annual maximum power demand (load), annual minimum power demand (load),
annual demand (load) distribution, annual power supply, power growth rate, power markets,
regulations, impact of integration with other renewable energy such as wind and solar.
7.2.5 Other data analysis shall include a comprehensive assessment on the authenticity, timeliness and
relevance of the data.
8 Computation of river basin or sub-basin hydropower potential
8.1 The theoretical water energy potential of the river (reach) shall be expressed in terms of average
annual output (power) (kW) or average annual energy (kWh). The average annual output and the average
annual energy shall be mutually converted by the means of Formula (A.1).
8.2 The theoretical water energy potential of the river (reach) shall be calculated in segments. The
river shall be segmented in accordance with the following criteria.
a) A larger tributary entry point should be used as a segmentation point for river water energy
computation. Taking the tributary entry point as the interface, the adjacent section upstream is
the lower section of the upper reach, and the adjacent section downstream of the entry point is the
upper section of the lower reach.
b) The reach with a large change in the longitudinal slope of the riverbed shall be regarded as a
segment.
c) The reach having particularly advantageous development conditions shall be regarded as a
segment.
8.3 The annual average flow at each analysis segment of the river shall be calculated, with their area
ratios based on the collected hydrologic data series of the river and the catchment areas of each analysis
segment of the river. If the flow data of the river basin is inadequate or unavailable, the information
should be obtained by the following methods.
a) If there is rainfall data on this river basin, the appropriate runoff coefficient should be converted
to the runoff in the same period with reference to Formula (A.2) or any other suitable formula or
methods.
b) If there is hydrological flow data on an adjacent river basin, the correlation with the river basin
shall be analysed, and the relevant data after revision may be used for water energy computation.
c) The hydrological flow parameters of the river basin can be obtained by using the hydrological
contours or effective charts issued by the hydrological or relevant department.
d) On-site measurement method.
8.4 The topographic map with a scale of 1:50 000 or higher should be used to verify and calculate the
elevation difference between the upper and lower sections of the reach by appropriate interpretation.
Use of Digital Elevation Model (DEM)/Digital Terrain Model (DTM) is encouraged.
8.5 Based on the flow rate of the upper and lower sections of the river reach and the elevation difference
between the upper and lower sections, the average annual output N (kW) of the reach shall be calculated
i
by the means of Formula (A.3). The average annual energy E (kWh) is calculated by Formula (A.1).
i
8.6 With the average annual output of water energy in each reach being accumulated, N , and the
∑
i
average annual power energy in each reach being accumulated, E , the theoretical water energy
∑
i
potential of the river (reach) may be obtained.
8.7 According to the above computation results, the theoretical potential of river water energy can be
calculated:
a) The relation curve between river elevation Z (m) and river length L (km): Z = f(L). Calculate the Z
and L values and draw the Z = f(L) curve on the rectangular coordinates. The curve shall show the
gradient of river water surface (or thalweg) along the river length.
b) The relation curve between river flow Q (m /s) and river length L (km): Q = f(L). According to the
flow rate Q calculated in 8.3, the value L is verified and calculated by using a topographic map or
DEM/DTM. Draw Q = f(L) curve on rectangular coordinates. This curve reflects the variation of
river flow along the river length.
c) Accumulation curve of river water energy potential NL=f() ; The N (kW) value may be
∑ ∑
i i
obtained by directly using the computation result in 8.6, the value L is verified and calculated by
using topographic map/DEM/DTM. Draw NL=f() curve on rectangular coordinates. The
∑
i
ordinate value of a certain point on the curve indicates the total potential of water energy from the
upstream starting point (for example, from the river source) to the section.
d) Curve of unit potential of river: N = f(L). That is, the distribution of the energy value N (kW/km)
d d
of the unit river length of the reach along the river length L (km). This curve reflects the energy
density of the reach. N is calculated by the Formula (A.4). The diagram of theoretical water energy
d
potential is shown in Figure A.1.
6 © ISO 2019 – All rights reserved

9 Preliminary planning of site
9.1 Planning content and main considerations
9.1.1 Preliminary planning of the SHP development scheme shall include selection of the site,
development type and construction scale of the SHP plant.
9.1.2 The preliminary planning of the hydropower station site shall involve the following
considerations.
a) The topography and geology shall be suitable for planning the relevant structures of the hydropower
station.
b) The hydropower potential should be relatively concentrated, and the hydro energy density of the
river reach be relatively higher.
c) Power evacuation/transmission: the hydropower station is close to the load areas or close to the
power grid.
d) Access and transportation with different options shall be evaluated and available.
e) Minimal inundation of farmland, villages or towns, forests and other natural and social resources.
f) Avoiding natural resources, protected areas, heritage areas and cultural heritage sites.
g) The electricity market demand and the additional requirements of the power system for utilization
of power from the proposed SHP plant.
h) Comprehensive integration of water supply, irrigation, tourism and navigation.
i) Avoid conflicts with existing national and local water related existing schemes and future plans
and manage the conflicts between different plans in accordance with the local/state/national
planning principles.
9.2 Types of SHP stations and applicable conditions for development
9.2.1 Dam-type hydropower station
Dam-type hydropower stations may be classified into two types, namely in-stream hydropower
stations or dam-toe hydropower stations.
a) The in-stream hydropower station (along river channel) mostly applies to the river reach in
relatively plain areas with relatively small head (less than 15 m), where the river is relatively
wide; it is also used for irrigation channels or water supply with a certain drop. See Figure B.1 and
Figure B.2 for schematic diagrams.
b) The hydropower station at a dam toe applies to a wide range of water heads, ranging from a few
metres to more than 100 metres. See Figure B.3 for a schematic diagram.
9.2.2 Diversion-conduit-type hydropower station
The diversion-conduit-type hydropower station is suitable for river sections where the river channel is
relatively narrow, the slope of the river section is relatively steep, and the geological conditions of the
riverbank slopes are favourable. Applicable heads range from a few metres to a few hundred metres.
See Figure B.4 for a schematic diagram.
9.2.3 Reservoir-based, run-of-river hydropower station (hybrid)
The commonly known as run-of-river with diversion or storage dam hydropower station is suitable for
river sections where the upstream of the dam site can easily form storage capacity (diurnal, seasonal
or annual), and the downstream of the dam site has a relatively concentrated drop. See Figure B.5 for a
schematic diagram.
9.3 Utilization of several special geographical conditions of rivers
9.3.1 Utilization of natural waterfalls
The natural waterfall has a relatively concentrated drop. The barrage may be built at the appropriate
location on the steep slope of the waterfall and then the water is diverted by the conduit into the
turbine generator unit in the powerhouse to generate electricity. See Figure B.6 for a schematic
diagram. However, such schemes shall be carefully planned in coordination with the relevant tourism
department, including scheduling of flow for waterfalls and power generation.
9.3.2 Utilization of rapids or natural waterfalls
Rapids or natural waterfalls are easily formed in river courses in mountainous areas. For such river
sections, low-height weirs may be built depending on the actual situation, and, by rational use of the
terrain, water may be diverted into the powerhouse through a diversion canal to generate electricity.
However, for such hydropower stations, special attention shall be paid to flood control issues. See
Figure B.7 for a schematic diagram.
9.3.3 Utilization of river bends
In mountainous areas, the river channels are mostly curved, and the curve distance is relatively small.
A low-height dam may be built upstream of the curve, to connect the curves by using a diversion canal
(or tunnel); cut-off the curved river channel and obtain the river bend drop, and the powerhouse may
be built on a suitable location on the diversion canal (or tunnel). See Figure B.8 for a schematic diagram.
9.3.4 Utilization of the fall on an irrigation channel
The waterfall on an irrigation channel may be used to build a hydropower station in the channel. For
diversion-channel-type hydropower stations, the tail water after power generation shall return to the
original irrigation channel. See Figure B.2 for a schematic diagram.
9.3.5 Utilization of kinetic energy of flowing waters in a river or canal
The kinetic energy of flowing waters in a river or canal may be used to produce electrical power.
Because this is powered by kinetic energy instead of potential energy, it is known as "velocity" power
generation. See Figure B.9 for a schematic diagram.
9.4 Estimation of the development scale of a hydropower station
9.4.1 The mean annual flow at the planning site may be found by using the curve in the diagram of
theoretical water energy potential Q = f(L).
9.4.2 The usable drop at the planning site may be checked and calculated.
9.4.3 The mean annual output of the hydropower station at the planning site may be calculated by
using Formula (A.5). The minimum ecological flow shall be maintained in accordance with the regulations
of the state/country; if there is no specific regulation in the country, it may be calculated as 10 % of the
mean annual flow.
8 © ISO 2019 – All rights reserved

9.4.4 The annual energy of hydropower station may be preliminarily determined by the annual
utilization hours:
a) Select the expected annual utilization hours for the hydropower station. The following selection
principles shall be followed.
1) A small value is taken if the difference in precipitation between the wet and dry seasons is
obvious; a medium to large value is taken if the difference in flow between the wet and dry
seasons is not obvious.
2) A small to medium value is taken for the hydropower station operating in a network connected
to the grid; for an isolated power station, a large value is taken.
3) A medium to large value is taken for a hydropower station without regulation function; a
median value is taken for a hydropower station with regulation function.
4) Installed capacity of the SHP plant shall be based on optimization studies, taking into account
flow duration and the energy market.
b) After selecting the desired number of annual utilization hours, the installed capacity shall be
estimated in accordance with Formula (A.6).
10 Site surveys and investigations
10.1 Hydrological surveys
Hydrological surveys shall include surveys of rainfall consistency, field investigation of runoffs,
investigations of historical floods, and investigations of historical dry flows. The survey content is
generally as follows.
a) Survey of rainfall consistency: For areas with short historical data, especially those sites lacking
records, the survey may be carried out by visiting the site and talking to the residents along the
river to understand qualitatively the rainfall pattern over the years, the distribution consistency
within the year and the duration of rise and fall of the river.
b) Runoff measurement: An approximate measurement of the flow of the river section may be studied
by a portable flowmeter, or a simple float flow measurement method, to compare it with the
historical record in the same period.
c) Historical flood surveys:
1) Preparation for surveys: It is necessary to make full use of basic data collected in the previous
work, such as vertical and horizontal sections of the river, including highest flood levels; the
historical data should be considered in advance to understand the number, magnitude and
timings of the occurrence of historical floods.
2) Site surveys: Importance shall be attached to selecting a straight river section, focusing on
bridges, ancient monuments, bends, and river meandering, to check the traces of flood marks.
3) Investigation and visit: Visit the older residents along the river to determine the year and
month of historical floods, the traces/high flood marks left and the flooding process.
4) Field measurements: The elevation of the flood trace/high flood marks, and the vertical and
horizontal sectional map of the nearby river section, shall be included.
d) Investigation of the historical dry season: The survey process is similar to the flood survey.
10.2 Surveys on the planning site
10.2.1 Dam site surveys
The specific location shall be verified on site in line with the dam/diversion structures site selected on
the topographic map. According to the basic principles of dam site selection, the left and right banks
and the surrounding terrain of the dam site, the subsurface strata and rock structure of the dam site
shall be initially evaluated to determine its suitability as the best location for the construction of a
dam/diversion structure.
10.2.2 Plant site surveys
The location of the powerhouse selected on the topographic map shall be verified to make sure it meets
the basic requirements from topographical and geological considerations. At the same time, the relative
positional relationship between the powerhouse and the dam shall be studied to justify whether the
water head utilization level in the preliminary plan is met.
10.2.3 Water conveyance line surveys
The topographical and geological conditions along the water conveyance line shall be surveyed.
Unfavourable landforms such as landslides, collapse and large spans of aqueducts shall be specifically
evaluated.
10.2.4 Reservoir survey
The geological structure of the bed of the reservoir area shall be investigated and attention shall be
paid to whether there are buried channels, river deposits, fossil valleys, karst caves, fractures and
faults. Basic assessment of reservoir rim slope stability shall be ensured.
10.3 Preliminary determination of available water heads for the hydropower station
10.3.1 The water surface upstream of the dam site and the surface downstream of the powerhouse
shall be used as measuring points, and the natural drop at the planning site shall be measured by using
elevation instruments such as a hand-held GPS instrument, a level gauge or total station.
10.3.2 The natural drop plus the storage height of planned water retaining structure may be adopted as
the gross head of the hydropower station. The characteristic water level upstream of the water-retaining
structure shall be determined after the scheme comparison and evaluation in the design stage.
10.4 Other construction conditions for investigation
10.4.1 Assess the transportation conditions of the planned site and the feasibility of new road
construction or other options such as rope ways.
10.4.2 Verify that the rare animal and plant species near the planning site are consistent with the data.
10.4.3 Visit the historical sites and their distribution according to the records.
10.4.4 Investigate the population density and distribution, land use and ownership near the planning
site and within the reservoir area.
10.4.5 Investigate important buildings and other public facilities in the planning area.
10.4.6 Investigate other relevant plans for the river basin.
10 © ISO 2019 – All rights reserved

10.4.7 Investigate the availability of construction materials.
11 Preparation of site construction plan
11.1 Selection of installed capacity
The installed capacity of the SHP plant shall be selected according to the hydrologic data survey and the
measurement of the usable drop at the site.
11.2 Selection of turbine types
The appropriate turbine type shall be initially selected in the turbine type table or utilization range
chart based on the water head and discharge of the hydropower station.
11.3 Number of units
According to the revised installed capacity of the power station, the number of units is selected and
shall meet the following requirements.
a) In order to facilitate maintenance and management, units with the same capacity shall be selected.
b) Considering the reliability requirements of the power supply, two or more units should be used.
c) When the distribution of runoff is severely unbalanced in wet and dry seasons, units of two
different capacities should be selected.
d) When selecting the capacity of a single unit, the convenience of manufacturing, transportation and
adequacy of utilization shall be taken into account.
11.4 Selection of dam type
The type of dam shall be selected according to the topography, geology, hydrology and construction
materials, as well as the preliminary planning results of the selected sites, including mainly the
following.
a) Gravity dam: This should be built on a rock foundation, but a gravity weir may be built on a soft
foundation.
b) Arch dam: This should be built on dam sites with narrow river gorges, symmetrical and continuous
hills on both banks, and good geological conditions.
c) Earth/rock fill dam: This is suitable for local dam construction where there are abundant materials
that are convenient for construction and transportation; it has relatively low requirements for
foundation geological conditions.
d) Sluice dam/barrage: This is applicable to low water head hydropower projects in river channels
or pl
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