AS 3778411-1991 (R2009) Measurement of water flow in open channels Measurement using flow gauging structure by SAIGlobalAPAC

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									                                                                                                                                        AS 3778.4.11—1991
                                                                                                                                        ISO 4371:1984
                                                                                                                                        (Reconfirmed 2009)
                                                                                           AS 3778.4.11—1991




                                                                                                               Australian Standard®
This is a free 6 page sample. Access the full version at http://infostore.saiglobal.com.




                                                                                                               Measurement of water flow in open
                                                                                                               channels

                                                                                                               Method 4.11: Measurement using flow
                                                                                                               gauging structures—End-depth method
                                                                                                               for estimation of flow in non-rectangular
                                                                                                               channels with a free overfall
                                                                                                               (approximate method)
                                                                                           This Australian Standard® was prepared by Committee CE-024, Measurement of Water Flow
                                                                                           in Open Channels and Closed Conduits. It was approved on behalf of the Council of
                                                                                           Standards Australia on 12 July 1991.
                                                                                           This Standard was published on 23 September 1991.




                                                                                           The following are represented on Committee CE-024:

                                                                                               •    Association of Consulting Engineers, Australia
                                                                                               •    Australian Water and Wastewater Association
                                                                                               •    Board of Works, Melbourne
                                                                                               •    Department of Water Resources, N.S.W.
                                                                                               •    Engineering and Water Supply Department of South Australia
                                                                                               •    Forestry Commission, N.S.W.
                                                                                               •
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                                                                                                    Institute of Instrumentation and Control
                                                                                               •    Monash University
                                                                                               •    Snowy Mountains Engineering Corporation
                                                                                               •    University of New South Wales
                                                                                               •    University of Queensland
                                                                                               •    Water Authority of Western Australia
                                                                                               •    Water Board, Sydney—Illawarra—Blue Mountains
                                                                                               •    Water Resources Commission, Queensland




                                                                                           Standards Australia wishes to acknowledge the participation of the expert individuals that
                                                                                           contributed to the development of this Standard through their representation on the
                                                                                           Committee.




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                                                                                                                                                    AS 3778.4.11—1991
                                                                                                                                                    (Reconfirmed 2009)




                                                                                           Australian Standard®
This is a free 6 page sample. Access the full version at http://infostore.saiglobal.com.




                                                                                           Measurement of water flow in open
                                                                                           channels

                                                                                           Method 4.11: Measurement using flow
                                                                                           gauging structures—End-depth method
                                                                                           for estimation of flow in non-rectangular
                                                                                           channels with a free overfall
                                                                                           (approximate method)

                                                                                           First published as AS 3778.4.11—1991.
                                                                                           Reconfirmed 2009.




                                                                                           COPYRIGHT
                                                                                           © Standards Australia
                                                                                           All rights are reserved. No part of this work may be reproduced or copied in any form or by
                                                                                           any means, electronic or mechanical, including photocopying, without the written
                                                                                           permission of the publisher.
                                                                                           Published by Standards Australia GPO Box 476, Sydney, NSW 2001, Australia
                                                                                           ISBN 0 7262 7068 7
                                                                                                                                             2


                                                                                                                                       PREFACE

                                                                                           This Stand ard was prepared by the Standa rds Australia Committee on Measurement of Water Flow
                                                                                           in Open Chann els and Closed Condui ts. It is identical with and has been reproduced from
                                                                                           ISO 437 1:198 4, Measurement of liquid flow in open chan nels by weirs and flumes—End-depth
                                                                                           method for estimation of flow in non-rectangula rchanne ls with a free overfall (approximate method).
                                                                                           Under arrangements made between Stand ards Australi a and the International Stand ards Bodi es,
                                                                                           ISO and IEC, as well as certain other Standa rdsorganization s, users of this Australian Stand ard are
                                                                                           advised of the following:
                                                                                           (a) Copyrigh t is vested in Standa rds Australia.
                                                                                           (b) The number of this Standard is not reproduced on each page; its identity is shown only on the
                                                                                               cover and title pag es.
                                                                                           (c) There may be occasion al dual langu age sections, but English is always one of the lang uag es
                                                                                               reproduced.
                                                                                           (d) Where any cross-references to page numbers appea r within the text, these rela te to pag e
This is a free 6 page sample. Access the full version at http://infostore.saiglobal.com.




                                                                                               numbering in the International Stand ard and are to be disregarded.
                                                                                           This Standard is one of a series which deal s with methods of measurement of water flow in open
                                                                                           chann els. The series when complete will consist of the following parts:
                                                                                           Part 1:        Vocabula ry and symbols
                                                                                           Part 2.1:      General—Guide lin es for the selection of method s of measurement
                                                                                           Part 2.2:      General—Establishment and operation of a gaugin g station
                                                                                           Part 2.3:      General—Determination of the stage-discharge relation
                                                                                           Part 2.4:      General—Estimation of uncertain ty of a flow-rate measurement
                                                                                           Part 2.5:      General—Guide lin es for the selection of flow gaugin g structures
                                                                                           Part 3:        Velocity-area methods
                                                                                           Method 3.1: Measurement by current-meters and floats
                                                                                           Method 3.2: Measurement by moving-boa t method
                                                                                           Method 3.3: Measurement by slope -area method
                                                                                           Method 3.4: Colle ction and processing of data for determination of errors in measurement
                                                                                           Method 3.5: Investigation of total error
                                                                                           Method 3.6: Measurement of flow in tida l channel s
                                                                                           Method 3.7: Measurement by ultrasonic (acoustic) method
                                                                                           Method 3.8: Electromagnetic method using a full-channel-width coil
                                                                                           Part 4:        Measurement using flow gaugi ng structures
                                                                                           Method 4.1: Thin-pla te weirs
                                                                                           Method 4.2: Rectangu lar broad-crested weirs
                                                                                           Method 4.3: Round -nose horizontal broad-crested weirs
                                                                                           Method 4.4: V-shaped broad-crested weirs
                                                                                           Method 4.5: Trian gul ar profile weirs
                                                                                           Method 4.6: Flat-V weirs
                                                                                           Method 4.7: Rectangu lar, trapezoidal and U-shaped flumes
                                                                                           Method 4.8: Trape zoidal profile weirs
                                                                                           Method 4.9: Parshall and Saniiri flumes
                                                                                           Method 4.10: End-depth method for estimation of flow in rectang ula r chan nels with a free overfall
                                                                                           Method 4.11: End-depth method for estimation of flow in non -rectang ular chan nels with a free
                                                                                                          overfall (approximate method) (this Standard)
                                                                                           Part 5:        Dilution methods
                                                                                           Method 5.1: Constant-rate inj ection method for the measurement of steady flow
                                                                                           Method 5.2: Integration method for the measurement of steady flow
                                                                                           Part 6.1:      Measuring devices, instruments and equipment—Rotating ele ment current-meters
                                                                                           Part 6.2:      Measuring devices, instruments and equ ipment—Direct depth sound ing and
                                                                                                          suspension equi pment
                                                                                           Part 6.3:      Measuring devices, instruments and equipment—Cali bration of rotating ele ment
                                                                                                          current-meters in straight ope n tanks
                                                                                           Part 6.4:      Measuring devices, instruments and equipment—Echo sounde rs for water dep th
                                                                                                          measurements
                                                                                           Part 6.5:      Measuring devices, instruments and equipment—Waterlevel measuring devices
                                                                                           Part 6.6:      Measuring devices, instruments and equipment—Cable way system for stream
                                                                                                          gaugi ng
                                                                                           Part 6.7:      Measuring devices, instruments and equipment— Ultrasonic(acoustic) velocity meters
                                                                                           Part 6.8:      Measuring devices, instruments and equipment—Position fixing equipment for
                                                                                                          hydrometric boa ts
                                                                                                                                                           3

                                                                                           For the purposes of this Australian Stand ard, the ISO text shou ld be modified as foll ows:
                                                                                           (i) Wherever the words ‘International Standa rd’ appe ar, referring to this Standard, they should be
                                                                                                 read as ‘Australian Stand ard’.
                                                                                           (ii) Wherever the word ‘fluid ’ appea rs, it shou ld be read as ‘water’.
                                                                                           (iii) Substitute a full poi nt (.) for a comma (,) as a decimal marker.
                                                                                           (iv) The references to other pub lication sshould be repl aced by references to Australi an Standards
                                                                                                 as follows:
                                                                                                 Reference to International Standard                 Australian Standard
                                                                                                 ISO                                                 AS
                                                                                                                                                     3778        Measurement of water flow in open
                                                                                                                                                                 channels
                                                                                                 772     Liquid flow measurement in open             3778.1      Part 1: Vocabulary and symbols
                                                                                                         channels—Vocabulary and symbols
                                                                                                 1438 Water flow measurement in open                 3778.4.1 Part 4: Measurement using flow
                                                                                                         channels using weirs and venturi                        gauging structures
                                                                                                         flumes
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                                                                                                 1438-1 Part 1: Thin-plate weirs                                 Method 4.1: Thin-plate weirs
                                                                                                 3846 Liquid flow measurement in open                3778.4.2 Part 4: Measurement using flow
                                                                                                         channels by weirs and flumes—                           gauging structures
                                                                                                         Rectangular broad-crested weirs                         Method 4.2: Rectangular broad-
                                                                                                                                                                 crested weirs
                                                                                                 3847 Liquid flow measurement in open                3778.4.10 Part 4: Measurement using flow
                                                                                                         channels by weirs and flumes—End-                       gauging structures
                                                                                                         depth method for estimation of flow in                  Method 4.10: End-depth method for
                                                                                                         rectangular channels with a free                        estimation of flow in rectangular
                                                                                                         overfall                                                channels with a free overfall




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                                                                                           AUSTRALIAN STANDARD                                             4

                                                                                           Measurement of water flow in open channels

                                                                                           Part 4:
                                                                                           Measurement using flow gauging structures

                                                                                           Method 4.11:
                                                                                           End-depth method for estimation of flow in
                                                                                           non-rectangular channels with a free overfall
                                                                                           (approximate method)
This is a free 6 page sample. Access the full version at http://infostore.saiglobal.com.




                                                                                           0 Introduction                                                      ISO 3846, Liquid flow measurements in open channels by
                                                                                                                                                               weirs and flumes — Free overfall weirs of finite crest width
                                                                                           Free overfall occurs in many hydraulic structures when the          (rectangular broad-crested weirs).
                                                                                           bottom of a horizontal channel (or gently sloping channel)
                                                                                           is abruptly discontinued. Such an overfall forms a control          ISO 3847, Liquid flow measurement in open channels by
                                                                                           section and offers an approximate means for the                     weirs and flumes — End-depth method for estimation of
                                                                                           estimation of flow. The flow at the brink is curvilinear and,       flow in rectangular channels with a free overfall.
                                                                                           therefore, the depth at the drop is not equal to the critical
                                                                                           depth as computed by the principle based on assumption
                                                                                           of parallel flow. However, the ratio between the end depth          3 Definitions
                                                                                           and the critical depth (as in the case of the assumption of
                                                                                           parallel flow) has an almost constant value. Therefore,             For the purpose of this International Standard, in addition
                                                                                           from the depth measured at the drop, the discharge can              to the definitions given in ISO 772, the following definition
                                                                                           be estimated.                                                       shall apply:

                                                                                                                                                               unconfined nappe: The jet formed by the flow where the
                                                                                           1 Scope and field of application                                    guide walls of the structure end at the crest (or edge) and
                                                                                                                                                               permit free lateral expansion of flow and where the nappe
                                                                                           This International Standard specifies a method for the              is sufficiently ventilated to ensure atmospheric pressure
                                                                                           estimation of subcritical flow of clear water in smooth,            below the nappe.
                                                                                           essentially horizontal, straight open channels with a
                                                                                           vertical drop and discharging freely. Gentle positive slopes
                                                                                           not greater than 1 in 2 000 are admissible. This Inter-             4 Units of measurement
                                                                                           national Standard covers channels with the following types
                                                                                           of cross-section, the nappe being unconfined:                       The units of measurement used in this International
                                                                                                                                                               Standard are SI units.
                                                                                             a)   trapezoidal;

                                                                                             b)   triangular;                                                  5 Selection of site
                                                                                             c)   parabolic;
                                                                                                                                                               A preliminary survey shall be made of the physical and
                                                                                             d)   circular.                                                    hydraulic features of the proposed site to check that it
                                                                                                                                                               conforms (or may be made to conform) to the require-
                                                                                           Using the measured depth at the end, the flow can be                ments necessary for measurement by the end depth
                                                                                           estimated.                                                          method.

                                                                                                                                                               Particular attention should be paid to the following features
                                                                                           2 References                                                        in selecting the site and ensuring the necessary flow
                                                                                                                                                               conditions:
                                                                                           ISO 772, Liquid flow measurement in open channels —
                                                                                           Vocabulary and symbols.                                                a) an adequate straight length (at least 20 h e where h e
                                                                                                                                                                  is the end depth corresponding to the maximum
                                                                                           ISO 1438/1, Water flow measurement in open channels                    discharge anticipated) of channel of regular cross-
                                                                                           using weirs and venturi flumes — Part 1: Thin-plate weirs.             section should be available upstream of the drop;



                                                                                                                                                    COPYRIGHT
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                                                                                                             AS 3778.4.11-1991 (R2009), Measurement of water
                                                                                                             flow in open channels Measurement using flow
                                                                                                             gauging structures - End-depth method for
This is a free 6 page sample. Access the full version at http://infostore.saiglobal.com.




                                                                                                             estimation of flow in non-rectangular channels
                                                                                                             with a free overfall (approximate method)




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