ISO/TR 8363:1997
(Main)Measurement of liquid flow in open channels — General guidelines for selection of method
Measurement of liquid flow in open channels — General guidelines for selection of method
Mesure de débit des liquides dans les canaux découverts — Lignes directrices générales pour la sélection de la méthode
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Standards Content (Sample)
ISOITR
TECHNICAL
8363
REPORT
First edition
1997-09-01
Measurement of liquid flow in open
channels - General guidelines for
selection of method
Mesure de d&bit des liquides dans /es canaux d6couverfs - Lignes
directrices g&n&ales pour la &lection de la m6thode
Reference number
ISODR 8363:1997(E)
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lSO/TR 8363:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 technical
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Commission (IEC) on all matters of electrotechnical standardization.
in exceptional circumstances a
The main task of technical committees is to prepare International Standards, but
following types:
technical committee may propose the publication of a Technical Report of one of the
cannot obtained for the publication of an International
1, when the required support Standard, despite
- type
repeated
efforts;
- type 2, when developmen t or where for any other reason there is the future
the subject is still under technical
International Standard;
but not immediate possibility of an agreement on an
type 3, when a technical committee has collected data of a different kind from that which is normally published
I”, for example)
as a ,n Internationa .I Standard ( “state of the art
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they
can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or useful.
ISOKR 8363, which is a Technical Report of type 2, was prepared by Technical Committee ISO/TC 113,
Hydrometric measurements, Subcommittee SC 1, Velocity area methods.
This document is being issued in the type 2 Technical Report series of publications (according to subclause G.6.2.2
of part 1 of the IEC/ISO Directives) as a “prospective standard for provisional application” in the field of hydrometric
measurements because there is an urgent need for guidance on how standards in this field should be used to meet
an identified need.
This document is not to be regarded as an “International Standard ”. It is proposed for provisional application so that
information and experience of its use in practice may be gathered. Comments on the content of this document
should be sent to the IS0 Central Secretariat.
Technical Report will be carried
A review of this type 2 out not later than th ree years after its publicati on with the
options of: extension fo r another three years; conversion into an International Standard; or withd
rawal.
This first edition cancels and replaces the first edition of IS0 8363:1986, which has been technically revised.
Annex A of this Technical Report is for information only.
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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Printed in Switzerland
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ISO/TR 8363: 1997(E)
TECHNICAL REPORT 0 Iso
Measurement of liquid flow in open channels - General guidelines
for selection of method
II Scope
This Technical Report gives general guidelines for the selection of a suitable method for measurements of liquid
flow in open channels. More specific guidelines are contained in International Standards relevant to each method.
2 Methods of measurement
Methods which are suitable for measurements of liquid flow in open channels and which form the subjects of
International Standards11 are as follows:
1) Velocity-area method by wading.
2) Velocity-area method from a bridge.
3) Velocity-area method using a cableway.
4) Velocity-area method using a static boat.
5) Velocity-area method using a moving boat.
6) Velocity-area method using floats.
7) Slope-area method.
8) Ultrasonic method.
9) Electromagnetic method.
10) Dilution method with a chemical tracer.
11) Dilution method with a radioactive tracer.
12) Dilution method with a fluorescent tracer.
13) Cubature method.
14) Thin-plate weirs (sharp crest, V-notch).
Thin-plate weirs (sharp crest, rectangular, with suppressed side contractions).
15)
16) Thin-plate weirs (sharp crest, rectangular, with side contractions).
1) See annex A for a list of these International Standards.
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ISO/TR 8363: 1997(E)
17) Weirs (broad-crested with sharp upstream edge).
18) Weirs (broad-crested with rounded upstream edge).
19) Weirs (triangular profile).
20) Weirs (streamlined triangular profile).
21) Weirs (triangular profile, flat-v).
22) Weirs (V-shaped, broad-crested).
23) Weirs (trapezoidal profile).
24) Flumes (rectangular-throated).
25) Flumes (trapezoidal-throated).
26) Flumes (U-shaped throat).
27) Flumes (Parshall and SANIIRI).
28) Free over-falls, end-depth method (rectangular and non-rectangular channels).
3 Principles of measurement
3.1 Velocity-area methods
3.1.1 Methods using stationary meters
The cross-section of an open channel is divided into several segments. The width of each segment and the depth
and mean velocity at a vertical in each segment are measured. The total discharge through the cross-section is
then the sum of the products of velocity, width and depth of each segment.
l
3.1.2 Moving boat method
The moving boat method is a modification of the velocity-area method using a stationary current meter. A current
meter is suspended from a boat at a constant depth below the water surface while the boat crosses the river on a
chosen transit line. During the crossing, the current meter reading, depth, distance from bank and time of
observation are recorded at intervals. The velocities near the surface are adjusted to give the mean velocity
perpendicular to the transit line at each position across the channel. The total discharge through the channel at the
transit line is the sum of the products of the mean velocity, width and depth of each segment in which a velocity was
recorded.
3.1.3 Method using floats
When measurements using current meters are not feasible, the velocity can be estimated by noting the time taken
for a float to travel a known distance.
3.1.4 Ultrasonic method
The velocity of sound in water is measured by simultaneously transmitting pulses in both directions through the
water from transducers located in the bank on each side of the river. Alternatively, the two transducers can be on
the same bank with a reflector or transponder on the other. The transducers are located so that the pulses in one
direction travel against the flow and in the other direction with the flow. The difference between the velocities of the
ultrasonic waves is related to the speed of the flowing water at the elevation of the transducers. This velocity can be
related to the average velocity of flow over the whole cross-section, and by relating the cross-sectional area and
water level, the discharge may be deduced from measurements of water velocity and stage.
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ISO/TR 8363:1997(E)
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3.1.5 Electromagnetic method using a full channel width coil
Small electrical potentials are set up between opposite banks of a river by means of electromagnetic induction as
the water flows through a vertical magnetic field. The field is set up by a coil buried below the bed or bridged across
the river. The potential generated is proportional to the width of the river, the magnetic field and the mean velocity in
the cross-section. The discharge is then obtained by multiplying this mean velocity of the cross-sectional area of
flow.
3.2 Measuring structures
3.2.1 Weirs
A relation between head over the crest of the weir and the discharge is established, usually in a laboratory and
applied to the field installation. The head over the weir is measured and this value inserted in the appropriate
formula to obtain a value of discharge. If the flow is non-modular (the water level downstream is sufficiently high to
influence the water level upstream of the weir and the discharge), the head over the weir and the head at the crest
or downstream are measured to determine discharge.
3.2.2 Flumes
A relation between the head upstream of the throat of the flume and the discharge is established. Thereafter, as
with weirs, the discharge is determined from the measurement of the upstream water level. If the flow is non-
modular, measurements of head both upstream and downstream are necessary.
3.2.3 Free overfalls (end-depth method)
In a device creating abrupt drop in the flow, the channel depth at the brink of the drop and the flow area of the
channel at the brink section are measured. The discharge is then determined using the appropriate equation.
3.3 Dilution methods
A tracer liquid is injected into a stream, and at a point further downstream, where turbulence has mixed the tracer
uniformly throughout the cross-section, the water is sampled. The ratio of the concentrations between the solution
injected and the water at the sampling station is a measure of the discharge.
3.4 Other methods
3.4.1 Slope-area method
The cross-section of a channel is measured at several sections along a reach which is as straight and as uniform as
practicable. The roughness of the channel is estimated after examination of the channel or measurement of the bed
features. The discharge is determined by measuring the water level at two or three sections a known distance apart
and inserting the slope, breadth, depth and roughness in an open channel flow equation (for example that of Chezy
or Manning).
3.4.2 Cubature method
This method is restricted to situations where flow causes a change in water level and the volume of stored water.
The water level and surface area of the stored water are measured on two occasions at a known time interval. The
mean discharge is obtained by dividing the volume of water stored, or released from storage, by the time interval.
4 Applicable conditions for selection of method
The selection of the most suitable method for measuring discharge should be based on the applicable conditions
indicated in table 1. If the releva
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