IS 15122: Measurement of Liquid Flow in Open Channels Under Tidal Conditions

31 Pages·2002·2.7 MB·English

by  Bureau of Indian Standards

इंटरनेट मानक
Disclosure to Promote the Right To Information
Whereas the Parliament of India has set out to provide a practical regime of right to
information for citizens to secure access to information under the control of public authorities,
in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
to the public, particularly disadvantaged communities and those engaged in the pursuit of
education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
“जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ”
Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru
“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 15122 (2002): Measurement of Liquid Flow in Open
Channels Under Tidal Conditions [WRD 1: Hydrometry]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 15122 : 2002
ISO 2425 : 1999

~ liFtCf}
~ ~Ei~i -q em
MCiI • llTtr=r
Indian Standard
MEASUREMENT OF LIQUID FLOW IN OPEN
CHANNELS UNDER TIDAL CONDITIONS
ICS 17.120.20
OBIS 2002
BUREAU OF INDIAN STANDARDS-
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW 'DELHI 110002
April- 2002
IS 1&122: 2002
ISO ~426: 1999
AMENDMENTl
Page2,Subclause4.3.1
Add the following textat the end ofthe subclause:
"Thisvalue, whenusedin conjunctionwiththe cross-sectional~will pro~deanestimateofthe flow
in the channel.
Page2,Subclause4.3.2
Replace the last sentence withthe following:
"Aftercalibration, measurementsofelectricalparametersand waterdq)th provide a meansofestimating
the discharge".
PageJ, Subclause5.Jc)
In the first line, replace "usually" with "could".
Page3, Subclause5.2.1
Replacethe penultimate sentencewith the following:
"Under variable or unsteady conditioas, the frequency of measurement, although affecting the
operationalcost ofeach gaugingstationand importanteconomically,maynotbecompromised".
Page3, Subclause5.2.2a)
Replace"tidalrange" with "tidal rangeincludinglevel,flow,and velocity"
Page4, Subclause5.2.2f)
Replacethis subclause withthe following:
"f) change in flow direction duringa tidal cycle includingflowreversalor backwatereffects"
Fluid Flow Measurement Sectional Committee, WRD 01
NATIONAL FOREWORD
This Indian Standard which is identical with ISO 2425 : 1999 'Measurement of liquid flow in open
channels under tidal conditions' issued by the International Organization for Standardization ( ISO )
was adoptedby theBureauof IndianStandardsonthe recommendationsofthe Fluid FlowMeasurement
Sectional Committee ( WRD 01 ) and approval"of the Water Resources Division Council.
Inthe adoptedstandard,certainconventionsare, however. notidenticaltothose usedin IndianStandards.
Attention is especi~lIy drawn to the following: .
a) Whereverthe words 'International Standard' appear referring to this standard, they should be
read as 'Indian Standard'.
b) Comma( ,) has been usedas a decimal markerwhile in IndianStandards,thecurrentpractice
is to use a point ( . ) as the decimal marker.
Amendment No.1 to the above International Standard has been printed at the end.
CROSS REFERENCES
In thls adopted standard, the following International Standards have been referred. Read in their
respective places, the follOWing Indian Standards:
International Standard Corresponding Indian Standard Degree of Equivalence
ISO 748 : 1997 Measurement IS 1192 : 1981 Velocity-area Identicalwith elucidation in Indian
of liquid flow in open methods for measurement of Standard ( IS 1192: 1981 isunder
channels - Velocity-area flow of water in open channels revision basedon ISO 748: 1997
methods ( first revision ) 'Measurementofliquidflowinopen
channels Velocity-area
metnods' )
ISO 772 : 1996 Hydrometric IS 1191 : 1971 Glo~sary of Technically equivalent ( IS 1191 :
determinations - Vocabulary terms and symbols used in 1971 is underrevision based on
and symbols connection with the measure ISO 772 : 1996 'Hydrometric
ment of liquid flow with a free determinations- Vocabularyand
surface ( first revision ) symbols' )
REFERENCES TO ERRORS AND CLARIFICATIONS IN TEXT
The TechnicalCommitteewhileadoptingthe textof this InternationalStandard identifiedcertaintextual
errors to the following clauses and felt necessary to correct/clarify these in the Indian context:
Clause Reference Corrections/Clarification
6.1.1.3.1(I) Where oblique flow is unavoidable, the angle between the direction of flow
and the line normal to the cross-section shall be measured and the measured
velocitycorrected. Special instrumentsare availableformeasuring b9th angle
and velocity at a point simultaneously.
IS 15'12-2-: 2002
ISO 2425-: 1999-
Indian Standard
.MEASUREMENT OF LIQUID FLOW IN OPEN
CHANNELS UNDER TIDAL CONDITIONS
1 -Scope
This Intemational Standard provides a summary of a selection of recommended methods available for the
measurement of liquid flow in tidal channels. special consideration being given to those techniques that are either
uniqueto or particularly appropriatefor measurement undertidal conditions, includingtreatmentof errors.
Reference is also made, where appropriate, to methods developed for measurement in non-tidal channels, but in
such cases attention is drawnto theirlimitationswith respectto practicalityand/oraccuracy.
This Intemational Standard does not describe altemative-methods, such as weirs, flumes, dilution gauging, salt
velocity and floats, although they may be suitable undercertain conditions, es~iallywhere the effect of tides only
impedes and does not stop or reverse the passage of stream flow. These methods are described in detail in other
International Standards.
The standardcomprisestwo parts:
a) techniquesforsingle measurements of tidal flow;
b) techniques appropriatefor continuous measurementof tidal flow.
The cubature method of measurement, although currently not used, is included in annex A. Annex B presents
methods suifable for measurement for tidal conditions, and annex C gives an example of the computation for a
single vertical. Similarcomputations may be made for otherverticals.
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 Intemational 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 lEe
rnai·ntain registers-ofcurrenttyvalid"lntemational Standards.
ISO 748:1997, Measurementofliquidflow inopenchannels- Velocity-area methods.
ISO 772:1996, Hydrometricdeterminations - Vocabularyandsymbols.
3 Terms_and defin:tions
Forthepurpos-es-of!hi.s-InIem-&"·U~J"IC'Il-Standard,etherrtnsand ~;.,;._"._---_::::..~:_-_.:.:: :"':~;-'--".-:":' "';:-;;".::j'.

1
IS.-: ~:t.122 ~" 2002~:~;
ISO··.··242&.1;~189~'~
.: -_ '._' ~•. _~._:~~..c•._._r-'.Jo,..........
4 Principles of methods of.meaurement
4.1 General
Tidal-flow rneasur~~ntcan be an instantaneous rate of.flow or a total.volume of flow during a flood or ebb tide.
The unsteady natUrJI·arld..~C~ ~iRr~~ioft ~f·ftoW:~.ui1der tidal 'c~difl9"S'~te..pr~· of measurement
additional to those ~..~~.~~ ,.measurement 01_ the discha,ge of unidirectional streams. The methods
specified in ISO 748,~·lSO'1.100•.ISO;,4S69,ISO 9123;.J8O 9823and ISO .9825 cannot-therefore always be applied
to tidal channels. Anychange in waterquality brought aboutby tidal conditions may affect the methods specified in
ISO 6416and ISO 9213. .
Forvarious reasons, dlr.measurements of velocityin tidal channels are more liableto large errors than are those
madeunderconditionsof unidirectionalflow. .
The methods of measu'rement included in this International Standard may be grouped into either single or
continuousmeasurementS.
measurement
4.2 Single methods
4.2.1 Velocltj-a....methOd
At a chosen gauging site, the velocity of flow and the area of cross-section of the channel are measured. The
productofthese measureme~at·anyinstant is the rate of flow ordischargepastthe gauging site at thatinstant. It
is referredto'astheVelocity-Areamethodandincludesthefollowing techniques:
a) eurrentmeterfrom a fixed station;
b) Current meterfrom a moving station (movingboat).
4.2.2 Cubaturemethod
In an areawhich includesa stretchof riverchannel and its flood plain, surfaceareas and rise in waterlevel of stored
waterare measured at known time intervals. Volumes of stored waterare computed, and the flow into the upstream
stretch of riverisestimated, fromwhichthe average rate of flow is determined (see annexA).
4.3 Continuous measurementmethods
4.3.1 UltrasonicmethOd (ISO6416)
Transducers are positioned on each bank of the river channel, such that the flight path is at an oblique angle to the
direction of flow. The time taken for a pulse of sound to travel in both directions is measured andcompared. From
thesetwotimes, the meanvelocitycan becomput~d.
4.3.2 .~omagnetlc method (ISO 9213)
A ~ontal.-coil.is'constructed" above.or.below a riv~r channel. A magnetic fieJd is generated by an alternating
curret:'! and··voltages are induced in the fJowi~g water which acts as an'electrical conductor. After. calibration,
rne~urementsofelectricalparametersand'waterdepthprovidea meansof measuringthedischarge.
4.3.3 Unateady-flowmodels
Unsteady-flow modelsmay be used for computi~g contin.~ou~ recoros of discharge in open c~a~nelsin bot~ tidal
and non-tidal conditions. These models, however, are not appncable where'aIongitudiilal density gradient. such as
a salt-waterwedge, ispresent.
Unsteady...fIow ~ are.·based on the numerical solution ofnon-linear partial differential equation$ that describe
one
gradually varied unsteady flow in open channels. The available models enlploy or:"moM of·SeVeral·rlumerical
computation techniques. Data requirements, which can be substa.ntiaf,·.depend on the..nUmerical techniques
employedby the moderseleCted.·It'·is·A8C8$eary-that·t8e~·fOr-the·appticatioA~Qf-unsteady-ftow·modets andthe
datarequire~~be.clearty definedandunderstood·f orsuccessfullycomputingdischarges.
-~is ---'.15-122 : 2002
''SO' 2425-: 1999
5 Special considerations and choice of method---
5.1 Special considerations
·Changes in waterlevel at the mouth of a riverdueto tidal actioncause backwatereffects in thechannel. These may
alterwater level only, orboth water level and direction of flow. The whole flow may be reversed in direction, oronly
someof theflow maybe reversed dueto differences in density.
Most flow-gauging techniques are generally best suited to condinons closely approximating steady flow, but
unsteadyflowcauses additional difficulties as follows.
a) At anysection, waterlevelscontinuouslychange;
b) at anypointon a vertical, velocities continuouslychange eitherwith orwithoutchange in direction;
c) in any vertical, the continuously changing velocities usually create greater velocity gradients than in channels
with steady uniformflow;
d) during the period of transition in flow direction (flood to ebb or ebb to flood), zero velocity occurs at a
succession of points oyerthe changing velocity profile;
e) high waterand low watermaynottake placeat the sametime as the reversal in flowdirection;
f) the change in direction of flow does nottake place at the same time throughoutthewettedcross-section;
g) when the direction of flow changes, the characteristics of the approach conditions from the upstream and the
downstream maybe differentand may result in divergence (whenthe angle between the flood andthe ebbflow
is otherthan 180°) between theflood and ebbflow;
h) flow maybe stratified, with liquids of different densities in each layer. While the liquid in the upperstratum may
flow in one direction, the more dense liquid in the lower stratum may flow at a different speed in the same or
opposite direction. When such density difference due to a salt water wedge occurs, the maximum velocity in
each layermayoccurat differenttimes;
i) at anysection in a channel, variations in waterlevel maycausechanges in width andcross-section of flow;
j) anincrease in the numberof measurements required to make an estimateof discharge;
k)' during atidalcyclethere maybe'vananons in salinityleadingtochanges in thespeed of sound andconductivity
of thewater, andthese mayadverselyaffect ultrasonic and electromagneticmethods.
5.2 Choice of method
5.2.1 General
In channels with steady flow, one of the main factors affecting the choice of gauging method is the frequency of
measurements of discharge in the channel. Observations may be repeated over months or years (continual or
repeatedmeasurements)-, oroccasionally, often once only--(occasionalmeasurements). Undervariable or unsteady
conditions, the frequency of measurement.--afthough affectingthe cost ofeach gauging and importanteconomically,
may notbecompromised. Thephysical-conditionsofflowand waterwa·y dominatethe choice. -
5.2.2 Physicalconditions
Thephysicalconditions whichaffectthechoice of gauging method are:
a) ..~al ~ng_e;,
b) -_width of channel;
-.
~:.;_~.··1.',a;~;::2102
.-.~.:~ a.2~.:.'~-
c) .variationinwidth·aIong.. channelandwith time; .
d) depthofchannel;
e) shapeofchannel;
f) changeinflow directionduringebbtide·orfIood··tide;
g) densityofrivertraffic;
h) the numberof·experiencedstaffavailable;
i) the numberofboatsand gaugingequipmentavailable;
j) environmentalconsiderations;
k) the intNsion of asalt-waterwedge;
I) a temperaturegradientin the water;
m) theincidenceofseichesandwind-induced·waves;
n) health andsafetyofpersonnel (includingtheavailabilityof lightingduring hoursof darkness);
0) the number of observatio". to be made, e.g. the velocity-area method requires a considerable number of
~tionsatonecross-section;
p) flow reversal oronlya backwatereffect.
Theprincipal methodsof measurementandthe effectofphysicalconditionson.the selection of the gauging method
aresummarizedin annexB,table B.2.
5.2.3 SelectIonanddemarcationofsite
5.2.3.1 General
Thesiteshouldcontain all stagesof flowwhichoccurorwhich needto bemeasured.
Ideally,sitesshould conformto thefoll.owing requirement•.
a) Sites where weeds grow should be avoided or kept free from weeds to ensure there is no obstruction to the
gaugingopenltion, unlessthemethodis tolerantto the presenceofweeds, e.g. el!Ctromagnetic method;
b) Thereshould beno vortices,deadwaterorstrongcross-currents;
c) Siteswhereice accumulatesshould be avoided;
d) Thesiteshouldbeaccessibleforstaffandequipmentatall stagesofflow.
6.2.3.2 PreIImInIHyreconni......aurvey.
A p,.ait:ni..-ry~surveyofall.~~ sites should be-_~.to eliminate.those which~are ·unsuitable,
and to ~ure .f!lat. ~.tIyd~ulic and topog~icf~t~F88of the remainder.conform to the requirements·of the
InternationalStandardspertainiogto~ methodof measurement-to·beused.···
Inspectionsunderdifferentflow conditionsmaybe necessaryto ensurethatconditionsunsuitableforthe .~.pf .
measurementdo notoccurwhenobservationsarebeingmade.
-.
A permanent benchmark should be established and reIa~ to·a··standard dat~ in ~ u~ :in the area.All .
subeequentlevellingsurveysshould~reducedtothe.standa~·da~. - .

4·