ISO 14139:2000

INTERNATIONAL ISO
STANDARD 14139
First edition
2000-06-15
Hydrometric determinations — Flow
measurements in open channels using
structures — Compound gauging
structures
Déterminations hydrométriques — Mesure de débit des liquides dans les
canaux découverts au moyen de structures — Structures de jaugeage
hybrides
Reference number
©
ISO 2000
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ii © ISO 2000 – All rights reserved

Contents Page
Foreword.iv
1 Scope .1
2 Normative references .1
3 Terms, definitions and symbols.2
4 Characteristics of compound gauging structures .3
5 Installation.4
5.1 Selection of site .4
5.2 Installation conditions.5
6 Maintenance .6
7 Measurement of head.7
7.1 General.7
7.2 Stilling well .7
7.3 Zero setting .8
7.4 Location of head measurement section(s) .8
8 Computation of discharge .8
8.1 Modular flow conditions .8
8.2 Non-modular (drowned) flow conditions .9
9 Errors in flow measurement .9
9.1 General.9
9.2 Sources of error.9
9.3 Kinds of error .9
9.4 Errors in coefficient values and errors in measurement.10
9.5 Combinations of uncertainties to give overall uncertainty in total discharge .10
9.6 Presentation of results.11
Annex A (normative) Velocity distribution .12
Annex B (normative) Non-modular (drowned) flow.14
Annex C (normative) Methods of calculations.24
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 14139 was prepared by Technical Committee ISO/TC 113, Hydrometric determinations,
Subcommittee SC 2, Notches, weirs and flumes.
Annexes A to C form a normative part of this International Standard.
iv © ISO 2000 – All rights reserved

INTERNATIONAL STANDARD ISO 14139:2000(E)
Hydrometric determinations — Flow measurements in open
channels using structures — Compound gauging structures
1 Scope
This International Standard specifies the methods of measurement of flow in rivers and artificial channels, using
any combination of standard weirs and/or flumes in a compound structure. For guidance on the selection of weirs
and/or flumes, refer to ISO 8368. All structures can be operated in the modular flow range, but only a limited
number of structures can be used in the drowned (non-modular) flow range (see clause 4). Compound weirs
improve the quality of discharge measurements at low stages.
The characteristics of velocity distribution are described annex A.
Structures standardized for operation in the drowned (non-modular) flow range and the method of computation of
flow are described in annex B.
Methods and examples of flow measurement calculations are given in annex C.
Compound flow-measuring structures without divide piers need in situ or model calibrations and are not covered by
this International Standard.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 772:1996, Hydrometric determinations — Vocabulary and symbols.
ISO 1438-1:1980, Water flow measurement in open channels using weirs and Venturi flumes — Part 1: Thin-plate
weirs.
ISO 3846:1989, Liquid flow measurement in open channels by weirs and flumes — Rectangular broad-crested
weirs.
ISO 4359:1983, Liquid flow measurement in open channels — Rectangular, trapezoidal and U-shaped flumes.
ISO 4360:1984, Liquid flow measurement in open channels by weirs and flumes — Triangular profile weirs.
ISO 4362:1999, Hydrometric determinations — Flow measurement in open channels using structures —
Trapezoidal broad-crested weirs.
ISO 4374:1990, Liquid flow measurement in open channels — Round-nose horizontal broad-crested weirs.
ISO 4377:1990, Liquid flow measurement in open channels — Flat-V weirs.
ISO/TR 5168:1998, Measurement of fluid flow — Evaluation of uncertainties.
ISO 8333:1985, Liquid flow measurement in open channels by weirs and flumes — V-shaped broad-crested weirs.
ISO 8368:1999, Hydrometric determinations — Flow measurements in open channels using structures —
Guidelines for selection of structure.
ISO 9826:1992, Measurement of liquid flow in open channels — Parshall and SANIIRI flumes.
ISO 9827:1994, Measurement of liquid flow in open channels by weirs and flumes — Streamlined triangular profile
weirs.
3 Terms, definitions and symbols
For the purposes of this International Standard, the terms and definitions given in ISO 772 apply. A full list of
symbols with the corresponding units of measurement is given below.
Symbol Units of
measurement
A area of cross-section of flow m
b crest width m
B width of approach channel m
C coefficient of discharge non-dimensional
D
C drowned-flow reduction factor non-dimensional
dr
C coefficient of approach velocity non-dimensional
v
e uncertainty in absolute magnitude non-dimensional
g acceleration due to gravity m/s
h gauged head m
H total head m
h crest-tapping pressure head m
p
h velocity approach head m
v
L length of flume throat or weir crest in direction of flow m
n number of measurements in a set non-dimensional
p height of flume invert or weir crest above mean bed level m
Q total discharge m /s
Q , Q , Q individual section discharges (in general Q)m /s
1 2 3 n
Q total modular discharge m /s
mod
q discharge per unit width m /s
s standard deviation of a set of measurements of quantity y m
y
s estimated standard deviation of the mean of several readings m
y
of quantity y
v mean velocity at cross-section m/s
v mean velocity in approach channel m/s
a
X percentage uncertainty in total discharge non-dimensional
Q
2 © ISO 2000 – All rights reserved

1)
X , X , X percentage uncertainty in individual section discharges non-dimensional
Q,1 Q,2 Q,3
X percentage uncertainty in estimating upstream water levels or non-dimensional
tu
upstream total head levels
X percentage uncertainty in estimating downstream water non-dimensional
td
levels or downstream total head levels
X percentage uncertainty in quantity y non-dimensional
y
� Coriolis energy coefficient non-dimensional
� difference in weir-crest levels m
� boundary layer displacement thickness m
Suffixes
1 denotes upstream value
2 denotes downstream value
Superscripts
G refers to gauging section
T refers to crest-tapping section
S refers to any other section
4 Characteristics of compound gauging structures
A compound gauging structure as covered by this International Standard comprises two or more individual
structures, operated in parallel and separated by divide piers.
The individual structures, which can be used in a compound gauging weir, are specified in ISO 1438-1, ISO 3846,
ISO 4359, ISO 4360, ISO 4362, ISO 4374, ISO 4377, ISO 8333, ISO 9826 and ISO 9827. The structures described
in ISO 4360, ISO 4362, ISO 4377, ISO 8333, ISO 9826 and ISO 9827 may be used in the drowned flow range (see
annex B.1).
In the modular flow range, discharges depend solely on upstream water levels, and a single measurement of
upstream head is required. In the drowned flow range, discharges depend on both upstream and downstream
water levels, and two independent head measurements are required. These are:
a) the upstream head; and either
b) the head measured in the crest-tapping for a triangular profile weir (two dimensional or flat-V forms);
c) the head measured within the throat of a Parshall flume; or
d) the head measured in the tailwater for the other structures.
1) In cases where the subscript of a symbol also contains a subscript, it is house style to write the second subscript on the
same line, after a comma.
Thus X is written X .
Q Q,1
The flow conditions considered are limited to steady or slowly changing flows. The essentially parallel flow through
the compound structure is ensured by the use of divide piers. The flow is separated by the divide piers into each
individual weir or flume. The discharge can be determined through each individual section by a single upstream
head measurement, at one section only, in the case of modular flow or by two independent head measurements, at
one section only, as required for drowned flow conditions. The summation of the discharges through each of the
sections prov
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