IS 15358: Liquid Flow Measurement in Open Channels - Flow Measurements Under Ice Conditions

16 Pages·2003·1.5 MB·English

by  Bureau of Indian Standards

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IS 15358 (2003): Liquid Flow Measurement in Open Channels -
Flow Measurements Under Ice Conditions [WRD 1: Hydrometry]
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IS 15358:2003
ISO 9196:1992
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3n-w13ihiwG?mm
Indian Standard
LIQUID FLOW MEASUREMENT IN OPEN
CHANNELS — FLOW MEASUREMENTS
UNDER ICE CONDITIONS
ICS 01.040.17; 17.120.20

@BIS 2003
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002
Ju/y 2003
Price Group 5
Fluid Flow Measurement Sectional Committee, WRD 01
NATIONAL FOREWORD
This Indian Standard which is identical with ISO 9196 : 1992 ‘Liquid flow measurement in open
channels — Flow measurements under ice conditions’ issued by the International Organization for
Standardization ( ISO ) was adopted by the Bureau of Indian Standards on the recommendations of
the Fluid Flow Measurement Sectional Committee and approval of the Water Resources Division
Council.
Inthe adopted standard, certain conventions are, however, not identical to those used in Indian Standards.
Attention is especially drawn to the following:
a) Wherever the words ‘International Standard’ appear referring to this standard, they should be
read as ‘Indian Standard’.
b) Comma ( ,) has been used as a decimal marker while in Indian Standards, the current practice
is to use a point ( .) as the decimal marker.
CROSS REFERENCES
Inthis adopted standard, the following International Standards have been referred. Read intheir respective
places, the following Indian Standards:
International Standard Corresponding Indian Standard Degree of Equivalence
1s0 555-1 : 1973 Liquid flow IS 9163 ( Part 1 ) : 1973 Dilution Technically equivalent
measurement in open channels — methods for measurement of steady
Dilution methods for measurement flow : Part 1 Constant-rate injection
of steady flow — Part 1 :Constant- method
rate injection method
ISO 555-2 : 1987 Liquid flow Nil —
measurement in open channels —
Dilution methods for the measure-
ment of steady flow — Part 2:

Integration method

ISO 748 : 1979 Liquid flow IS 1192:1981 Velocity area methods Technically equivalent
measurement in open channels — for measurement of flow of water in
Velocity-area methods open channels ( first revision)
ISO 772 : 1988 Liquid flow Is 1191 : 2003 Hydrometric Technically equivalent
measurement in open channels — determinations — Vocabulary and (Over95percentidentical
Vocabulary and symbols symbols ( second revision ) with ISO 772 : 1996
‘Hydrometric determina-
tions — Vocabulary and
symbok’)
1s0 1100-2 : 1982 Liquid flow IS 15119 ( Part 2 ) :2002 Measure- Identical ( with /S0 1100-
measurement in open channels — ment of liquid flow in open 2: 1998)
Part 2: Determination of the stage- channels : Part 2 Determination of
discharge relation the stage-discharge relation
ISO 1438-1 : 1980 Water flow IS 9108 : 1979 Liquid flow Technically equivalent
measurement in open channels measurement in open channels using
using weirs and Venturi flumes — thin-plate weirs
Part 1 :Thin-plate weirs

( Continued on third cover)
IS 15358:2003
ISO 9196:1992
standard
/ndian
LIQUID FLOW MEASUREMENT IN OPEN
CHANNELS — FLOW MEASUREMENTS
UNDER ICE CONDITIONS
1 Scope ISO 1438-1:1980, Water flow measurement in open
channels using weirs and Venturi flumes — Part 1:
Thin-plate weirs,
This International Standard deals with water dis-
charge measurements in rivers and channels under
ISO 3846:1989, Liquid flow measurement in open
ice conditions and provides information additional to
channels by weirs and flumes — Rectangular broad-
that published in previous International Standards,
crested weirs.
This International Standard does not specify meas-
uring instruments and equipment, which are dealt ISO 3847:1977, Liquid flow measurement in open
with in other International Standards. channels by weirs and flumes — End-depth method
for estimation of flow in rectangular channels with a
free overfall,
ISO 4359:1983, Liquid flow measurement in open
2 Normative references channe/s — Rectangular, trapezoidal and U-shaped
flumes,
The following standards contain provisions which,
ISO 4360:1984, Liquid flow measurement in open
through reference in this text, constitute provisions
channels by weirs and flumes — Triangular profile
of this International Standard. At the time of publi-
weirs.
cation, the editions indicated were valid. All stan-
dards are subject to revision, and parties to

ISO 4377:1990, Liquid flow measurement in open
agreements based on this Internationa l Standard
channels —F/af-V weirs.
are encouraged to investigate the possibility of ap-
plying the most recent editions of the standards in-
ISO 5168:1978, Measurement of ffuid flow – Esti-
dicated below, Members of IEC and ISO maintain
mation of uncertainty of a f70w-rate measurement.
registers of currently valid International Standards.
WMO (World Meteorological Organisation) Technical
ISO 555-1:1973, Liquid flow measurement in open
Note No, 117 (WMO No, 280), Use of weirs and flumes
channels — Dilution methods for measurement of
in stream gauging.
steady flow — Part ?: Constanf-rate injection
method.
3 Definitions
ISO 555-2:1987, Liquid flow measurement in open
channels — Dilution methods for the measurement
For the purposes of this International Standard, the
of steady flow —Part 2: integration method,
definitions given in ISO 772 apply.
ISO 748:1979, Liquid flow measurement in open
channels —Ve/ocity-area methods.
4 Methods of water discharge
ISO 772:1988, Liquid flow measurement in open measurement under ice conditions
channels — Vocabulary and symbols.
Discharges of water can be measured under ice
ISO 1100-2:1982, Liquid flow measurement in open conditions using velocity-area methods, represen-
channels — Part 2.’ Determination of the stage- tative vertical methods, dilution gauging methods
discharge relation. and by means of notches, weirs and flumes.

1
IS 15358:2003
ISO 9196:1992
4.1 Velocity-area method water period, are unsuitable for the measurement
of discharge owing to the multiplicity of channels,
The principle of this method is described in ISO 748. may be suitable under winter conditions since the
For channels in which a surface layer of ice exists, shallower channels may become blocked by slush
the cross-sectional area of water flowing is taken as or ice, leaving the main channel unblocked and
the area bounded by the bed line (or wetted per- tlowing,
imeter) and the lower edge of the ice cover or slush.
When flow is between layers of ice, the cross- 4,1.2 Frequency of water discharge measurements
sectional area also includes the area bounded by
the lower ice layer and the lower surface of the ice The frequency of water discharge measurements
cover or slush. during the winter period shall be such as to ensure
a reliable estimation of the discharge. If conditions
of stable ice cover exist, methods of hydraulic in-
4,1.1 Selection of site
terpolation of winter flow may be used. However,
under difficult conditions (such as those of unstable
Discharge measurements under ice conditions are
ice cover and incomplete freezing) measurements
usually conducted at the same sites used for open
shall be taken as frequently as possible, since in this
channel measurements. The site may be unsuitable
case the discharge is computed by the interpolation
UU3CI VCILIU II=II
of the observed discharges. The time at which the
daily discharge measurement shall be made shall
a) more than 25 0/0 of the cross-section is filled with
be determined from experimental data to ensure
slush, which is distributed unevenly over the
that a discharge measurement as close as possible
cross-section;
to the daily mean value, in rivers with considerable
daily variations in discharge, is obtained.
b) dead zones occupy more than 10 Y. of the
cross-section;
4.1.3 Measurements of ice cover thickness
c) there are large areas with very low stream vel-
ocities (less than 0,3 m/s) which cannot be The ice cover thickness shall be measured using
measured using current meters; ice-measuring sticks which are lowered into holes
drilled by hand or using mechanical drills. A zero
d) it is located in the backwater zone downstream reading may also be obtained.
of an ice gorge or ice jam;
4.1,4 Measurements of slush depth
e) there is a large open water area that remains
unfrozen throughout the winter (but see 4.1.7); For small depths of slush, measurements may be
made using an ice-measuring stick. The slush depth
9 it is liable to ice up owing to the f r eezing of water is indicated by a change in the resistance to clock-
flowing through cracks on the surface of the ice wise and anticlockwise rotation of the stick during its
cover indicating a possible breakup of the ice. rise, i.e. the resistance to rotation increases when
the slush layer is reached. For thicker depths of
During the open water period, i.e. the period when
slush, measurements may be made in a similar
there is no ice cover, sites additional to those
manner using a special rod with a stop plate or a
normally used for water discharge measurements
perforated disc attached to its end. In addition, cur-
should be selected and marked on the banks. After
rent meters are frequently used for slush depth
the ice cover at the river reach selected for
measurements. The current meter is lowered below
measurements has stabilized, a preliminary survey
the slush layers and is then gradually lifted until a
shall be made to select a longitudinal profile with a
zero reading is obtained. it should be borne in mind,
length equal to several widths and an appropriate
however, that the actual slush depth may be some-
number of holes shall be drilled along the profile to
what smaller than that obtained by measurement,
determine the occurence of slush and its distri-
because a zero reading will also be obtained when
bution. In channels in which slush is found to be
the flow velocity decreases to 0,03 m/s to 0,04 m/s.
present, and when it is impossible to select another
measurement reach, the measurement site shall be
located at the centre of a uniform river reach. 4,1.5 Determination of the effective depth
Following the preliminary choice of the site, four or In an ice-covered channel, the effective depth is
five holes shall be drilled across the river at equal computed by subtracting the distance between the
distances to determine whether a regular velocity water surface and the bottom of the ice layer or
distribution exists and to establish the slu,sh and ice slush from the total depth. The total water depth in
thickness over the cross-section. Sites in,. which the channel is measured using a rod or a cable-
slush divides the river Into separate streams shall suspended sounding weight which is lowered using
be avoided. Braided channels which, in the open a winch; the latter method is similar to the depth
2
IS 15358:2003
ISO 9196:1992
measurements made from a boat under open chan- contain substantially equal proportions of the
nel conditions. total water discharge.
4.1.6 Flow velocity measurements b) The location of the vertical shall be such as to
reflect the flow structure and the cross-section
4.1.6.1 Use of current meters under winter of the river bottom in the best possible way.
conditions
c) The distance between each vertical shall exceed
Flow velocity measurements are carried out using the propeller diameter of the current meter;
current meters which are lowered into holes drilled therefore, in very small rivers (brooks) there may
in the ice cover. Special equipment has been devel- be a small number of verticals.
oped (e.g. the arm-rotating installation, see tigure 1)
The profile of the bottom at the gauging station shall
to enable a current meter to be lowered vertically
be determined and the location of the verticals shall
into a hole and then for it to be rotated into a hori-
be selected prior to the formation of ice cover. When
zontal position. When a sufficiently deep and wide
this is not feasible, approximately 20 holes shall be
hole is available, a standard current meter with a
drilled along the cross-section at equal distances.
suspended weight or a current meter on a rod may
(From hydrometric practice it has been found that
be lowered directly in a horizontal position. The
20 is the minimum number of holes required to re-
current meter can be lowered using a suspension
produce the channel profile with sufficient accuracy.)
rod, a hand-operated cable (for small depths) or ca-
Additional holes shall then be drilled to ensure suf-
ble suspension equipment (for depths exceeding
ficient accuracy of discharge measurements. The
3 m to 4 m). During velocity measurements, the de-
location of the edges of the channel cross-section
vice by which the current meter is held shall be lo-
shall be determined after all other necessary holes
cated near the upstream side of the hole and shall
have been drilled, since it is easy to blunt the tip of
be held rigidly at the. upper edge of the hole to avoid
the drill during this procedure.
the influence of vertical stage pulsation.
To prevent the current meter from freezing up when 4.1.6.3 Velocity measurements on a vertical
it is carried between one measurement site and an-
other, it may be placed in a bucket containing Owing to roughness of the lower surface of the ice
heated water, or in a hot-air chamber. In measure- sheet, the vertical velocity curve for the winter pe-
ment sites with shallow water depth, when the cur- riod differs from that under open-channel conditions,
rent meter is lowered on a rod without a tailpiece, At the lower surface of the ice cover, the velocity
care shall be taken to ensure the correct position of distribution is very similar to that found in a pipe.
the current meter with regard to direction of flow at The degree of reduction in velocity varies with the
the site. In measurement sites where slush is pres- roughness of the lower surface of the ice.
\
ent, vane current meters may be u s ed in preference
If depth permits, the distance from the current meter
to cup-type meters which are liable to become

axis to the river bed and that from the current meter
blocked by slush ice.
axis to the lower ice surface should be no less than
Before the current meter is lowered, it is advisable twice the diameter of the vane propeller.
to clean a passage in the slush by means of a steel
Proceeding from the above criterion, the one-point
or wooden pole with discs or by using an elliptical
method can be applied where the effective depth is
(round-shaped) weight suspended on a cable.
about 0,30 m to 1,0 m; in this case, the current meter
is located at 0,5 times the effective depth. To com-
4.1.6.2 Selection of verticals for velocity
pute the mean velocity, a coefficient of 0,88 to 0,90
measurements
shall be applied (see ISO 748).
The principles governing the location of velocity When the effective depth is equal to or exceeds
verticals under ice conditions are similar to those 1,0 m, the two-point method is preferable (at 0,2, 0,6
governing the location of velocity verticals under and 0,8 times the effective depth). For greater effec-
open channel conditions. These principles are as tive depths, velocities may be measured at three
follows. points (at 0,15, 0,5 and 0,85 times the effective
depth). However, to ensure a high accuracy of w~r
a) The minimum number of velocity verticals shall discharge measurements, current velocities should
be 20, to ensure sufficient accuracy in velocity be measured at six points, i.e. at 0,2, 0,4,0,6 and 0,8
interpolation with respect to the channel width. times the effective depth, and at the lower surface
Sections between successive verticals shall of the ice and the bottom of the river.

3’
IS 15358:2003
ISO 9196: 1992
4.1.6.4 Computation of mean velocity onavetilcal The flow velocities above the ice shall be measured
using procedures similar to those for ice-free chan-
When the two-point or three-point method is used, nel discharge measurements.
the mean velocity on a vertical shall be computed
as the arithmetic mean of the measured values. For If the channel freezes to the bottom in winter and is
six-point measurements, the following equation (see filled with ice and snow, it is advisable to make, be-
ISO 748) shall be used to compute the mean velocity fore the start of the spring flood, a ditch in the snow
on a vertical: 0,5 m to 1,0 m wide and no less than 20 m long to
contain the first stream of water.
; = O,l(v~UfiaC~+ 2vo,z+ 2vo,d+ 2v0,Li+ 2}’0,6+ ‘M)
4.1.10 Safety practice for measurements from ice
cover
4.1.7 Discharge measurements under partial ice
cover conditions As a general rule, to ensure the safety of personnel
taking discharge measurements from ice cover, the
If the water at the gauging station is not completely ice thickness shall not be less than 0,1 m and the
frozen over, discharge measurements in ice- air temperature shall be below O“C.
covered sections can be carried out by using the
methods specified in 4.1.6. In an ice-free part of the The strength of the ice cover shall be tested using
stream, open channel methods are applied using a an ice chisel before a river is crossed. The speed
gauging footbridge, cableway or a boat. If current of a vehicle crossing the ice cover shall be low (es-
meters cannot be used in the open water section of pecially near the river banks) to prevent wave for-
the stream, velocity measurements shall be made mation which could increase the pressure on the
using floats; special floats or floating ice can be ice, Stricter precautions shall be taken where water
used to this end. During the period of ice drift on flows above the ice, or when new ice layers are
large rivers, the airborne method of velocity formed, since the ice cover is likely to be thin.
measurement is practically the only safe method to
Operators taking measurements of discharge from
use. “When drifting ice is distributed evenly over the
river, the ice floes may be photographed to deter- the ice cover may use crampons to prevent slipping
mine the flow discharge in the same way that flow on the ice. In addition, a means of rescue shall be
discharge measurements are made using floats. available.
Where there is an uneven distribution of ice over the
river width, special floats shall be dropped from an 4.1.11 Discharge computation
aircraft into the open water part of the stream and
The computation of the discharge under ice cover
additional photographs shall be taken to supplement
shall be made in accordance with the rules for open
the data.
channel discharge computations (see ISO 748), the

only difference being that the effective rather than

4.1.8 Discharge measurements un der multilayered the total depth is used.
ice conditions
The cross-sectional area of flowing water is thus
computed from the effective depths at the verticals
When there are two or more ice layers at the
and the distance between them. The total area of
measurement site, this site shall not be used and
submerged ice and slush at the measuring points
another site shall be selected for the discharge
and the distance between them. During the
measurements. The discharges determined at this
freezing-over period in rivers, when the total river
alternative site shall be correlated with the water
width differs considerably from the actual width of
levels at the permanent gauging station,
the cross-section of flow, two width values are
needed: one width value is determined with respect
4.1.9 Discharge measurements under conditions of to the water level in the ice holes and the other is
water flow above ice determined with respect to the cross-section of flow.
If water flows over the ice surface as well as below, 4.2 Representative vertical method
the discharges above and below the ice cover shall
be obtained separately. The discharge below the ice 4.2.1 Principle of the method
cover shall be determined before water appears
above the ice using the method described in 4.1,6. There is a close relationship between the mean flow
The cross-sectional area of the water flowing below velocity in the cross-section and the flow velocity at
the ice is determined using the data obtained in the a given vertical. The discharge Q may thus be ob-
preliminary measurements. However, the distance tained from the values of flow velocity measured at
between the water surface and the upper surface of a representative vertical in a cross-section using the
the submerged ice shall be measured. following equation:

4
IS 15358:2003
ISO 9196: 1992
Q=CFA mined. The dilution methods are dealt with in
1S0555-1 and 1S0555-2.
where
Tracer mixing may be unsatisfactory in ice-covered
A is the cross-sectional area at the given streams, owing to an increase in the area of low
water level; velocity currents. Therefore a greater length of
measuring reach may be required. Before the
v is the mean or unit velccity at the rep-
fluorometer tests are performed, all the samples of
resentative vertical;
cold river water shall be heated to the same tem-
c is a correction coefficient. perature to avoid temperature corrections. Heating
can also be helpful to prevent the accumulation on
the cuvette side walls of oxygen bubbles which pose
4.2.2 Selection of the vertical and determination of
difficulties for fluorometric measurements, es-
the correction coefficient
pecially where sdmples are taken from streams with
a high concentration of dissolved oxygen.
As a rule, for stable ice cover and in the absence of
slush and other ice formations dividing the flow into
separate jets, the correlation stated above, between 4.4 Discharge measurements by notches,
the mean velocity of flow and the velocity at a rep- weirs and flumes during the winter period
resentative vertical, is valid,
4,4.1 Design and construction
To obtain sufficiently accurate results, the choice of
the vertical and the establishment of the relationship
Details on the selection of the best possible type of
which is usually linear is made on the basis of 40
structure for a given stream, and on the specifi-
or 50 discharge measurements obtained using a
cations, calibration and operational procedures are
multi-po”int or two-point method. Measurements
given in ISO 1438-1, ISO 3846, ISO 3847, ISO 4359,
shall be carried out under stable conditions and
ISO 4360, ISO 4377 and WMO Technical Note No. 117
shall cover uniformly the total range of levels,
(WMO No. 280).
The measured discharge is plotted versus either the
product of the cross-sectional area and the mean 4.4.2 Protection under ice conditions
velocity of flow F, on the given vertical, or the prod-
uct of the cross-sectional area and the velocity flow Discharge measuring structures shall be heated by
YO* at 0,2 of the effective depth where the flow vel- enclosing the structure and the adjacent channel
ocity, according to the field data, is closest to the section in an insulated shelter and by installing
mean flow velocity. For practical purposes, the various heating sources (e.g. electric radiant heat-
graph which gives the best curve shall be chosen. ers, oil stoves and propane radiant heaters) inside
the hood of the shelter. Insulating shelters may be
The correction coefficient is obtained a s the tangent made on the basis of a number of designs. The hood
of the curve as it crosses the origin of coordinates, of the shelter may be made of thin round timber,
single or double pitched, which rests on the el-
4.2.3 Limits of application ements of the discharge measuring structure or on
posts. The hood may be covered with spruce or fir
The location of a representative vertical in the twigs, straw or reeds. When snow falls begin, snow
cross-section of a stream shall be stable throughout may serve as an additional means of insulation. in-
the year within the total range of stage. The mean side the shelter there shall be enough space to
square deviation of the relation between the dis- accommodate heaters and to provide free access to
charge obtained on the basis of the representative measuring devices. Either the roof or the walls shall
vertical method and the discharges actually meas- be equipped with one or two manholes with heat-
ured shall not exceed 5 0/0 to 10 O/O. The method is insulating doors.
not applicable for slush, intermittent backwater and
oblique current conditions. When measuring discharges under ice conditions,
ice upstream of the discharge measuring device
shall be removed to a distance of about four times
4.2.4 Discharge measurement procedure
the maximum head at the gauging section and ice
in the throat section of the measuring device shall
The usual procedure, as described in 4.1, shall be
be removed during the discharge measurement.
followed for measuring the discharge by means of
the representative vertical method.
To avoid large accumulations of slush (which may
block the intakes and stilling wells) upstream of the
-4.3 Dilution gauging method measuring device, the slush should be pushed
through the cross-section of the flowmeter by hand
To obtain the discharge using dilution methods, the or special slush-directing booms upstream of the
degree of trace mixing in the stream shall be deter- flowmeter should be installed. These booms are