IEC TS 62600-301:2019
(Main)Marine energy - Wave, tidal and other water current converters - Part 301: River energy resource assessment
Marine energy - Wave, tidal and other water current converters - Part 301: River energy resource assessment
IEC TS 62600-301:2019 provides:
· Methodologies that ensure consistency and accuracy in the determination of the theoretical river energy resource at sites that may be suitable for the installation of River Energy Converters (RECs);
· Methodologies for producing a standard current speed distribution based on measured, historical, or numerical data, or a combination thereof, to be used in conjunction with an appropriate river energy power performance assessment;
· Allowable data collection methods and/or modelling techniques; and
· A framework for reporting results.
The document explicitly excludes:
· Technical or practical resource assessments;
· Resource characterisation;
· Power performance assessment of river energy converters; and
· Environmental impact studies, assessments, or similar.
General Information
Standards Content (Sample)
IEC TS 62600-301 ®
Edition 1.0 2019-09
TECHNICAL
SPECIFICATION
Marine energy – Wave, tidal and other water current converters –
Part 301: River energy resource assessment
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IEC TS 62600-301 ®
Edition 1.0 2019-09
TECHNICAL
SPECIFICATION
Marine energy – Wave, tidal and other water current converters –
Part 301: River energy resource assessment
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-7273-2
– 2 – IEC TS 62600-301:2019 © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Symbols, units and abbreviated terms . 9
4.1 Symbols and units. 9
4.2 Abbreviated terms . 9
5 Methodology overview . 10
5.1 Study classification . 10
5.2 Project location identification . 10
5.3 Resource definition . 10
5.4 Methodology . 10
5.4.1 General . 10
5.4.2 Flow duration curves . 11
5.4.3 Velocity duration curves. 11
5.4.4 Energy production . 14
6 Flow Duration Curves . 14
6.1 General . 14
6.2 Measurement-based Flow Duration Curve . 14
6.3 Hydrologic modelling . 15
6.3.1 General . 15
6.3.2 Stochastic modelling . 15
6.3.3 Deterministic modelling . 16
6.4 Computing Flow Duration Curves . 17
7 Velocity Duration Curves . 19
7.1 General . 19
7.2 Measurement-based Velocity Duration Curve . 19
7.3 Hydrodynamic-model-based Velocity Duration Curve . 21
7.3.1 General . 21
7.3.2 Model selection . 21
7.3.3 Model domain . 22
7.3.4 Grid resolution . 22
7.3.5 Model inputs . 23
7.3.6 Boundary conditions and forcing . 24
7.3.7 Field-data requirements . 24
7.3.8 Velocity measurements . 25
7.3.9 Calibration . 25
7.3.10 Validation . 26
7.3.11 Energy extraction. 26
7.3.12 Computation of model-based velocities . 27
7.3.13 Calculating the Velocity Duration Curve . 28
8 Reporting requirements . 29
8.1 General . 29
8.2 Technical report . 30
8.2.1 General . 30
8.2.2 Development of the Flow Duration Curve . 30
8.2.3 Development of the Velocity Duration Curve . 31
8.2.4 AEP calculation . 31
8.2.5 Additional reporting . 31
8.3 Digital database . 32
8.4 Test equipment report . 32
8.5 Measurement procedure report . 32
8.6 Deviations from the procedure . 32
Annex A (normative) Guidelines for field data measurements . 33
Bathymetry . 33
Water level . 33
Discharge . 33
General . 33
Stage-discharge relationship . 34
Current profiler measurements . 34
General . 34
Fixed-location velocity profile . 34
Discharge and velocity transect survey . 35
Instrument configuration . 35
Correcting for clock drift . 36
Depth quality control . 36
Velocity quality control . 36
Turbulence . 36
Annex B (informative) Calculation of energy production . 37
General . 37
Energy production . 37
Annex C (normative) Evaluation of uncertainty . 39
General . 39
Uncertainty analysis . 39
Modelling uncertainty . 40
Bibliography . 41
Figure 1 – Flowchart outlining the methodology for a resource assessment . 12
Figure 2 – Types of hydrologic models for simulating discharge . 15
Figure 3 – Example FDC (curve) and assumed non-uniform discretisation (circles) . 18
Figure 4 – Example REC power-weighted speed versus discharge relationship using
discretised discharge values (circles) in Figure 3 . 28
Figure 5 – Example VDC using the transfer function derived from the curve fit shown
in Figure 4 and the full FDC shown in Figure 3 . 29
Figure B.1 –Power exceedance probabilities . 37
Table 1 – Outline of measurements. 13
Table C.1 − List of uncertainty components . 40
– 4 – IEC TS 62600-301:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARINE ENERGY – WAVE, TIDAL AND OTHER WATER CURRENT
CONVERTERS –
Part 301: River energy resource assessment
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62600-301, which is a technical specification, has been prepared by IEC technical
committee 114: Marine energy – Wave, tidal and other water current converters.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
114/285/DTS 114/301/RVDTS
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
A list of all parts in the IEC 62600 series, published under the general title Marine energy -
Wave, tidal and other water current converters, can be found on the IEC website.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be:
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
– 6 – IEC TS 62600-301:2019 © IEC 2019
INTRODUCTION
The extraction of energy from flowing water in rivers and canals is gaining acceptance around
the world as a means of generating electricity without the use of conventional hydropower
dams. The purpose of this document is to provide a uniform methodology that will ensure
consistency and accuracy in the estimation, measurement, characterisation, and analysis of
the river-velocity resource at sites that could be suitable for the installation of an individual or
array of River Energy Converters (RECs), together with defining a standardised methodology
with which this resource can be described and reported. Application of the estimation,
measurement, and analysis techniques recommended in this document will ensure that
resource assessment is undertaken in a consistent and equitable manner. This document
presents techniques that are expected to provide fair and suitably accurate results that can be
replicated by others. This document is intended to be updated as understanding of the
resource and its response to power extraction improves.
The overall goal of the methodology is to enable calculation of the Annual Energy Production
(AEP) for the proposed individual or array of river energy converters either as part of a
feasibility study (generic river energy converter) or a full study. For the full study, this
methodology is employed in conjunction with IEC TS 62600-300 applied at each river energy
converter location. Consistency is also maintained with IEC TS 62600-201 wherever possible.
In this document, the river energy resource (undisturbed or disturbed by power extraction) is
defined by the velocity duration curve. This document describes only the aspects of the
resource required to calculate the velocity duration curve and it does not describe aspects of
the resource required to evaluate design loads or to satisfy environmental regulations.
Furthermore, this document is not intended to cover every eventuality that may be relevant for
a particular project. Therefore, this document assumes that the user has access to, and
reviews, other relevant IEC documentation before undertaking work (e.g., surveys and
modelling), which could also satisfy other requirements.
MARINE ENERGY – WAVE, TIDAL AND OTHER WATER CURRENT
CONVERTERS –
Part 301: River energy resource assessment
1 Scope
This part of IEC 62600 provides:
• Methodologies that ensure consistency and accuracy in the determination of the
theoretical river energy resource at sites that may be suitable for the installation of River
Energy Converters (RECs);
• Methodologies for producing a standard current speed distribution based on measured,
historical, or numerical data, or a combination thereof, to be used in conjunction with an
appropriate river energy power performance assessment;
• Allowable data collection methods and/or modelling techniques; and
• A framework for reporting results.
The document explicitly excludes:
• Technical or practical resource assessments;
• Resource characterisation;
• Power performance assessment of river energy converters; and
• Environmental impact studies, assessments, or similar.
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.
IEC TS 62600-1, Marine energy – Wave, tidal and other water current converters – Part 1:
Terminology
IEC TS 62600-201, Marine energy – Wave, tidal and other water current converters –
Part 201: Tidal energy resource assessment and characterization
IEC TS 62600-300, Marine energy – Wave, tidal and other water current converters –
Part 300: Electricity producing river energy converters – Power performance assessment
ISO 1100-2:2010, Hydrometry – Measurement of liquid flow in open channels – Part 2:
Determination of the stage-discharge relationship
ISO 9825:2005, Hydrometry – Field measurement of discharge in large rivers and rivers in
flood
ISO 15769:2010, Hydrometry – Guidelines for the application of acoustic velocity meters
using the Doppler and echo correlation methods
ISO 18365:2013, Hydrometry – Selection, establishment and operation of a gauging station
– 8 – IEC TS 62600-301:2019 © IEC 2019
ISO TS 19130-2:2014, Geographic information – Imagery sensor models for geopositioning –
Part 2: SAR, InSAR, lidar and sonar
ISO TR 24578:2012 Hydrometry – Acoustic Doppler profiler – Method and application for
measurement of flow in open channels
ISO/IEC 98-1;2009, Uncertainty of measurement – Part 1: Introduction to the expression of
uncertainty in measurement
ISO/IEC 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM: 1995)
IHO (International Hydrographic Organisation), 2008, Standards for Hydrographic Surveys.
Special Publication No. 44. 5th Edition
ICES, 2006, Guidelines for Multibeam Echosounder Data
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 62600-1 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
equivalent diameter
diameter of a circle with area equal to the device projected
capture area
3.2
power-weighted speed
mean current speed derived with the weighted function of the
cube of the speed across the projected capture area
3.3
principal flow direction
primary orientation or heading of the river current
3.4
project blockage ratio
ratio of the sum total of the flow-facing area of the moving and
non-moving parts of all river energy converters divided by the average channel cross-
sectional area
Note 1 to entry: The average cross-sectional area is calculated by dividing the volume of the fluid in the river
energy converter site, determined from bathymetry subject to the lowest operational flow, by the length of the
project site along the direction of flow.
3.5
project site
portion of the river within which river energy converters and
their entire supporting infrastructure are located
3.6
projected capture area
frontal area perpendicular to the principal flow direction of
river energy converter components hydrodynamically utilised in energy conversion
4 Symbols, units and abbreviated terms
4.1 Symbols and units
a, b Linear fit coefficients for index rating (–)
A Projected capture area of the REC (m )
A Area of current speed bin i,k (m )
i,k
A(h) Cross-sectional area of the river as a function of water level, h (m )
B Number of current speed bins (–)
th
B Width of the i bin for the VDC (–)
i
d River depth (m)
D Equivalent diameter (m)
E
EP Energy production (kW)
F Exceedance probability (%)
Fr Froude number (−)
h River water level (stage) (m)
i Rank (–)
I Turbulence intensity (–)
k Index number across the vertical dimension of current speed bins (–)
n Number of discharge (or velocity) measurements (–)
N Number of velocity bins for the VDC (–)
B
N Number of hours in the month or year of interest (–)
h
P (U ) Power according to the REC power curve (kW)
i i
Q Discharge (m /s)
S Total number of current speed bins (–)
th
U Speed of the i bin from the VDC (m/s)
i
�
𝑉𝑉 REC power-weighted speed
V Average velocity for a river cross section (m/s)
avg
V Index velocity (m/s)
i
V Speed of the river velocity at current speed bin i,k (m/s)
i,k
4.2 Abbreviated terms
ADV Acoustic Doppler velocimeter
AEP Annual energy production
CP Current profiler
EP Energy production
FDC Flow duration curve
GPS Global positioning system
IEC International Electrotechnical Commission
– 10 – IEC TS 62600-301:2019 © IEC 2019
IHO International Hydrographic Organization
ISO International Organization for Standardization
MEP Monthly energy production
MV Moving vessel
NTP Network time protocol
PST Phase space thresholding
REC River energy converter
RTK Real time kinetic
TS Technical specification
VDC Velocity duration curve
5 Methodology overview
5.1 Study classification
Two types of studies are covered in this document: a full study and a feasibility study. The
distinction between the two is based on the amount of information available for the RECs to
be employed (i.e., whether it is a generic REC or has been extensively characterised with
regard to its performance). To complete the analysis, the following details of the REC shall be
available:
• REC dimensions including position in the water column and swept area;
• REC power curve with specified freestream measurement location;
• REC operational range; and
• REC thrust coefficient (for projects that include modelling energy extraction by the REC).
For the full study, REC data are supplied by the manufacturer following IEC TS 62600-300.
For the feasibility study, a generic REC is chosen and all supporting device data shall be
presented with justification in the report. The power and thrust coefficient shall be defined as
a range and therefore the feasibility study will result in an AEP range.
5.2 Project location identification
There is no required methodology for identifying particular project locations. This document
assumes that a project location has already been identified; however, some or all of the
methods outlined herein may be used to assist with project-location identification.
In this document, projects are considered small when the project blockage ratio is less than
5 %. Projects with blockage ratios greater than 5 % are considered large.
5.3 Resource definition
This document describes the methodology for the resource assessment, which consists of the
determination of the VDCs required for computing the AEP for individual or arrays of RECs.
5.4 Methodology
5.4.1 General
The resource assessment requirements are defined depending on the scale of the project
relative to the scale of the resource at the project location as well as the availability of
measurement data of sufficient quality and duration relative to the annual hydraulic cycle. The
resource assessment may be undertaken based upon exclusive use of site data or upon
numerical-model simulations used in conjunction with direct measurements for model
calibration and validation. A combination of measurements and numerical models may be
used to generate the required data for different parts of the resource assessment.
The following assumptions are made:
• The turbines are operating, therefore excluding impact of maintenance or technical issues
on the resource assessment;
• The turbines are operating in steady flow. Transient flow conditions due to flooding or due
to human impact such as filling or draining of a reservoir are excluded; and
• The turbines are operating in subcritical flow, i.e. with a Froude number smaller than 1:
𝑉𝑉
avg
𝐹𝐹𝐹𝐹 = < 1 (1)
�𝑔𝑔𝑔𝑔
where
V is the average velocity,
avg
g is the gravitational acceleration, and
d is the water depth.
NOTE While installation in supercritical flow, such as at rapids may be feasible, this type of installation would
most likely be small scale due to the nature (shallow, highly localised, high-velocity flow) of such flow systems.
Further, a turbine-triggered hydraulic jump is likely, however, capturing this effect in a model is challenging, and
could lead to significant error in the resource assessment.
The flowchart in Figure 1 outlines the methodology for performing the resource assessment.
The flowchart maps the multiple viable pathways through the methodology (centre of
flowchart) and includes all requirements (left and right sides of the flowchart). The rectangles
represent the required goals of the resource assessment, the ovals represent the different
paths to achieve these goals, and the rounded rectangles represent the measurements
required to support each step of the process. Table 1 outlines the various measurements,
their purpose, the minimum quantity, and the standardised collection method.
5.4.2 Flow duration curves
A flow duration curve (FDC) quantifies the percentage of time that the discharge in a river
exceeds a particular magnitude typically compiled on a monthly or annual basis. To produce
the FDC, at least 10 out of the previous 15 years of discharge and water-level field data for
the project site shall be used. If the specified minimum duration of field data is not available,
regional hydrological modelling shall be performed to develop at least 10 years of data,
validated with at least one year of discharge measurements. This document describes the
acceptable methodology for collecting the necessary field data, performing the model
simulations, and creating the FDC based on measured (6.2) or modelled (6.3) data.
5.4.3 Velocity duration curves
5.4.3.1 General
A VDC quantifies the percentage of time that REC power-weighted speed at a REC location
exceeds a particular value. The relationship between the river discharge and the
corresponding speed at each REC location needs to be ascertained to develop the VDC. For
small projects (project blockage ratio less than 5 %) where each REC has at least 10 D
E
downstream spacing, and where no flow modification for enhancing the power is incorporated,
the VDC may be estimated from direct hydrodynamic measurements as described in 7.2.
For all other projects, the VDC shall be assessed by hydrodynamic modelling including the
effect of energy extraction with appropriate verification by measurements. Of course, even
– 12 – IEC TS 62600-301:2019 © IEC 2019
small projects may implement the hydrodynamic modelling required for larger projects. If the
resource assessment reveals that RECs should be deployed in different locations where field
data have not been collected, then a combined data-collection and modelling effort focused
on the new REC locations shall be implemented.
Figure 1 – Flowchart outlining the methodology for a resource assessment
Table 1 – Outline of measurements
Number of
Types of measurements Purpose Method Clause
measurements
10 years of daily field
Measurement FDC A.3
data
1 year of daily field
Hydrology model FDC
data for validation
ISO 1100-2,
Discharge
3 different ISO 18365
discharges for each
Boundary conditions
calibration (i.e., high-
for hydrodynamic
flow, median-flow,
model validation
and low-flow
calibrations)
Upstream and
downstream
Boundary condition
boundaries and ISO 18365:
*
Water level and calibration of the A.2
within the project site 2013
hydrodynamic model
during discharge
measurements
At least 1 set (more if
Cross-sectional data
river morphology is
IHO, S-44:
Bathymetry seasonal and A.1
Field data for the
multiple model grids
hydrodynamic model
are used)
*
4 transects for each
Cross-section velocity
river cross-section, Vessel or in
contour
Calibration of the
for each discharge situ, A.4.2
hydrodynamic model
*
Cross-channel transects of used in the ISO 15769
flow velocity
calibration
2 REC locations for
A.4.1
*Validation of
each of the 3
hydrodynamic model
discharge conditions
Vertical distribution of Vessel or
velocity at REC location in situ
5 velocity/discharge
Computation of VDC
measurements from
from measurements
each REC location
Optional for the Vessel or
*
Each discharge A.5
Turbulence
hydrodynamic model in situ
*
Only needed for projects using hydrodynamic models to compute the VDC as defined in 7.3.
5.4.3.2 Direct measurement method
This document describes the acceptable methodology for collecting velocity and water-level
data in 7.2. Velocity data shall be collected at each REC location, but the water-level data
(stage) may be obtained anywhere within the project site. Total-discharge data shall be
collected simultaneously with the water-level and velocity field data to determine the
relationship between the current speed, water level, and discharge, which is then used to
develop the VDC.
5.4.3.3 Numerical modelling method
This document describes the acceptable methodology for determining the current
speed/discharge relationship based on numerical-model simulations in 7.3. First, the required
hydrodynamic model features are described, then the model inputs and required field data are
stipulated. The model shall have sufficient grid resolution to resolve individual REC locations.
Calibration field data consist of water-level measurements within the project region and cross-
channel transect measurements of current velocities. The model may have separate
calibration parameters (e.g., horizontal and vertical momentum diffusivities, eddy viscosities,
etc.) for different flow conditions; however, the model shall be validated for each set of
calibrated parameters with independent direct measurements of the vertical profile of velocity
at an individual REC location for three different discharges. Verification field data consists of
– 14 – IEC TS 62600-301:2019 © IEC 2019
velocity data at two or more REC locations for three different discharges. The validated
hydrodynamic model shall be run for at least 15 different discharge conditions spanning the
FDC to develop the corresponding VDC at each REC location. If required, the effects of REC
emplacement and operation shall be included in the model simulations used to develop the
VDC.
5.4.4 Energy production
The methodologies for computing the expected energy production (EP) for each month along
with the expected AEP are described in Annex B.
6 Flow Duration Curves
6.1 General
To estimate the hydrokinetic resource of a river segment with adequate reliability, a significant
quantity of measured or model-generated discharge data shall be compiled. Although an FDC
can be developed for any period of time, at least 10 years of data are required to ensure a
stationary curve because hydrologic and climatic variability can lead to substantially different
flow regimes over the course of just a few decades. Stationarity means that hydrological
variables fluctuate randomly and have time-invariant probability density functions, whose
properties can be estimated from an available record. For example, 10 years of data would
take into account the impact of large-scale atmospheric circulation phenomena, for example
the El Niño Southern Oscillation (ENSO), on basin-scale hydrology. If consecutive field data
are not available, 10 out of the last 15 years are acceptable, but all available field data shall
be used. Shorter than 10 years of field data sets can be augmented using outputs from a
hydrologic model.
NOTE In all FDCs, low flows are exceeded most of the time while high flows are infrequently exceeded. The x
axis (abscissa) indicates the percentage of time (or probability/frequency of occurrence) that a particular discharge
exceeds the corresponding discharge on the y axis (ordinate). On the FDC, the highest discharge in the record
(i.e., the period-of-record flood) is found close to 0 on the x axis and the lowest recorded discharge, which may be
zero, is found closer to 100 %.
Nonstationarity of the hydrologic regime, such as climate change and human intervention in
the river basin, is a complicating factor. Existing climate models and trend analysis from short
hydrological records are often not reliable and detailed enough to project changes in flows. It
is difficult to predict how the climate change will affect the watershed and such changes
cannot be estimated with a sufficient accuracy from short hydrologic records.
6.2 Measurement-based Flow Duration Curve
Continuous daily stage-discharge measurements for at least 10 years (for each month of the
year) shall have been collected over the most recent 15 years. Intermittencies (sporadic
outages) are acceptable so long as these omissions do not exceed 5 % of the data set;
measurement years are not required to coincide with calendar years. These stage-discharge
data shall be available on a daily basis. Higher frequency (e.g., 15 min) data can be used, but
they should be converted to daily-average stage-discharge data.
Any modifications to the river near the project site (e.g., diversions, reservoirs, vegetation
removal, land-cover or land-use changes, pumping, etc.) including natural modifications
(e.g., landslides, forest fires, etc.) need to be taken into account when reviewing the suitability
of available field data. Data collected prior to permanent (e.g., dams) or during temporary
significant changes (e.g., landslide) in the river shall be excluded.
In general, obtaining direct continuous measurements at the project site is the preferred
approach because this facilitates the most accurate analysis. In some cases, long-term field
data may be available at the project site. However, if long-term field data are available at a
nearby (surrogate) site, they may be used if the FDC derived from the project site (so long as
it is composed of at least one year of data) is within 10 % of the FDC at the surrogate site.
This implies that the flow at the two sites is not altered by dams/weirs or through
merging/forking of tributaries.
Long-term data will usually be in the form of stage-discharge data (i.e., water-level
measurements and corresponding discharge). For these data to be viable for resource
assessment, an accurate stage-discharge relationship needs to be established (see
Clause A.4).
6.3 Hydrologic modelling
6.3.1 General
When only limited measurement data are available at a project site, hydrologic modelling can
be used to develop the FDC. Hydrologic modelling can help avoid expensive long-term field
data collection campaigns. However, to validate the hydrologic model, a minimum of one year
of discharge data will need to be collected at the project site.
There are two general categories of hydrologic models: deterministic and stochastic as
conceptualised in Figure 2. Recently, hybrid models that combine elements of both types of
modelling approaches have also been suggested [Corzo Perez, 2010]. Any type of hydrologic
model that satisfies the specified accuracy requirements may be used for simulating flows and
then computing the corresponding FDC and VDC. The following subclause details the desired
requirements and accuracies when applying models in this context.
Figure 2 – Types of hydrologic models for simulating discharge
6.3.2 Stochastic modelling
Statistical regionalisation approaches are sometimes used to estimate FDCs at sites where
limited or no discharge measurements are available. Compared to regional flood-frequency
analyses commonly used in hydrology, regionalisation of FDCs is performed less often.
Despite numerous advantages to the regionalisation approach, appropriate validation of
estimated FDCs at ungauged sites remains a challenge. The selected modelling approach
and associated field data shall be justified.
When estimating FDCs for ungauged watersheds, the following steps should be considered:
a) Identify gauged watersheds similar to the target, ungauged watershed within the
surrounding large geographic/hydrologic/climatic region and/or within the attribute space.
In hydrology, this process is called neighbourhood selection (i.e., identification of a
homogeneous region). A neighbourhood shall be selected from within the same
geographic/hydrologic/climatic region where the ungauged site is located. There are
several ways of accomplishing this task such as using the region-of-influence approach,
canonical correlation analysis, cluster analysis, or variants of these approaches [Burn,
1990; GREHY, 1996; Hosking and Wallis, 1997; Zrinji and Burn, 1994].
b) Develop regional relationships of FDC characteristics and watershed attributes from
locations with available field data and transfer those relationships to ungauged locations.
Some of the techniques used for this purpose include the index-flood method, drainage-
area-ratio methods, parametric characterisation of FDCs, statistical characterisation of
FDCs, graphical characterisation of FDCs, nonlinear spatial-interpolation techniques,
– 16 – IEC TS 62600-301:2019 © IEC 2019
regression-based logarithmic interpolation, multiple linear/nonlinear regression methods,
etc.
c) Select representative FDCs (i
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