SIST EN ISO 772:2022

SLOVENSKI STANDARD
oSIST prEN ISO 772:2020
01-december-2020
Hidrometrija - Slovar in simboli (ISO/DIS 772:2020)
Hydrometry - Vocabulary and symbols (ISO/DIS 772:2020)
Hydrometrie - Begriffe und Symbole (ISO/DIS 772:2020)
Hydrométrie - Vocabulaire et symboles (ISO/DIS 772:2020)
Ta slovenski standard je istoveten z: prEN ISO 772
ICS:
01.040.17 Meroslovje in merjenje. Metrology and measurement.
Fizikalni pojavi (Slovarji) Physical phenomena
(Vocabularies)
17.120.20 Pretok v odprtih kanalih Flow in open channels
oSIST prEN ISO 772:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 772:2020

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oSIST prEN ISO 772:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 772
ISO/TC 113 Secretariat: BIS
Voting begins on: Voting terminates on:
2020-10-13 2021-01-05
Hydrometry — Vocabulary and symbols
Hydrométrie — Vocabulaire et symboles
ICS: 17.120.20; 01.040.17
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
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WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 772:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020

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COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2020 – All rights reserved

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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Structure of the vocabulary . 1
3 Terms and definitions - General terms . 1
4 Terms related to Velocity-area methods .12
5 Terms related to Flow measurement structures .17
6 Terms related to Dilution Method .28
7 Terms related to Instruments and equipment .30
8 Terms related to Sediment transport .36
9 Terms related to Snow .41
10 Terms related to Groundwater .46
11 Terms related to Uncertainties in hydrometric determinations .57
Annex A (normative) Symbols used in hydrometry .65
Bibliography .68
Index .69
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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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee [iso/tc113, Hydrometry]
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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Introduction
In the preparation of this International Standard, the following principles were adopted wherever
possible:
a) to standardize suitable terms and symbols without perpetuating unsuitable ones;
b) to discard any term or symbol with differing meanings in different countries, or for different
people, or for the same person at different times, and to replace that term or symbol by one which
has an unequivocal meaning;
c) to exclude terms which are self-evident.
As far as possible terms in existing International Standards have been included; however, these terms
may be the subject of future amendments.
NOTE that similar or identical terms may have separate definitions under the different categories.
It is recognized that it is not possible to produce a complete set of definitions which will be universally
acceptable, but it is hoped that the definitions provided and the symbols used will find widespread
acceptance and that their use will lead to better by understanding of the hydrometric practices.
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oSIST prEN ISO 772:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 772:2020(E)
Hydrometry — Vocabulary and symbols
1 Scope
This International Standard gives terms, definitions and symbols used in standards in the field of
hydrometry.
2 Structure of the vocabulary
The terminology entries are presented in systematic order, grouped into sections according to
particular methods of determination or in relation to particular subjects. Annex A lists the symbols
used in this International Standard.
The structure of each entry is in accordance with ISO 10241. Country codes are in accordance with
ISO 3166-1.
3 Terms and definitions - General terms
3.1
hydrometry
science and practice of measuring the components of the hydrological cycle, including rainfall, water
level, flow and sediment transport of surface waters, and groundwater characteristics
3.2
hydrology
science that deals with the waters above and below the land surfaces of the Earth, their occurrence,
circulation and distribution, their properties and their reaction with environment
3.3
flow
water flowing on or below the land surface under gravitational influence
3.4
runoff
volume of water flowing through a given channel cross section in unit time related to a given
catchment area
3.5
discharge
Q
Volume of water flowing through a given channel cross section in unit time
3.6
current
directed movement of water
3.7
steady flow
condition in which the discharge does not change in magnitude with respect to time
3.8
unsteady flow
condition in which the discharge changes in magnitude with respect to time
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3.9
uniform flow
flow, in an open channel, in which the depth and velocity remain constant along the open channel
Note 1 to entry: For uniform flow, the velocity vector is constant along every stream line. Uniform flow is possible
only in an open channel of constant slope and cross section.
3.10
non-uniform flow
flow, in an open channel, in which depth and/or velocity change along the open channel
3.11
critical flow
flow, in an open channel, in which the specific energy is a minimum for a given discharge
Note 1 to entry: Under this condition, the Froude number is equal to unity and small surface disturbances cannot
travel upstream.
3.12
subcritical flow
flow in an open channel at less than critical velocity, that has a Froude number of less than unity, and in
which small surface disturbances can travel upstream
3.13
supercritical flow
flow in an open channel at more than critical velocity, that has a Froude number of greater than unity,
and in which small surface disturbances cannot travel upstream
3.14
transverse flow
lateral flow
flow horizontally perpendicular to the main direction of flow
Note 1 to entry: Transverse (lateral) flow is frequently associated with secondary flow.
Note 2 to entry: Transverse (lateral) flow in open channels with a curved plan form causes superelevation of the
water surface at the outside of the bend.
3.15
stratification
state of a water body that consists of two or more layers arranged according to their density, the lightest
layer being on top and the heaviest at the bottom
3.16
critical depth
depth of flow at which critical flow occurs
3.17
critical velocity
velocity at critical flow
3.18
channel
course of a river, stream, or other watercourse
3.19
open channel
longitudinal boundary surface consisting of the bed and banks or sides within which water flows with
a free surface
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3.20
canal
man-made channel, usually of regular cross-sectional shape
3.21
stable channel
open channel in which the bed and the sides remain essentially stable over a substantial period of time
in the reach under consideration, and in which the scour and deposition during the rising and falling
stages are negligible
3.22
unstable channel
open channel that changes frequently and significantly in its plan-form and/or cross-sectional form for
the reach under consideration
3.23
tidal channel
open channel in which the flow is subject to tidal influence
3.24
tide
periodic rise and fall of water due principally to the gravitational attraction of the sun and the moon
3.25
estuary
lower tidal reaches of a river that is freely connected with the sea which receives fresh water supplies
from upland drainage areas
3.26
stream
water course water flowing in an open channel
3.27
river
large natural water course
3.28
large river
major river
large natural water course that generally flows into the sea
3.29
creek
brook
small natural water course
3.30
torrent
small natural water course that is characterized by steep slopes and significant rapid changes in
discharge and that can transport considerable volumes of solid material
3.31
alluvial river
river which flows through alluvium formed from its own deposits
3.32
incised river
river which has formed its channel by a process of erosion
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3.33
braided river
river characterized by a wide and shallow open channel in which flow passes through a number of small
interlaced channels
3.34
reach
length of open channel between two defined cross sections
3.35
meandering channel
water course formed by natural flow processes and movement of sediments following generally an
alternating regular sinuous path
3.36
thalweg
line joining the lowest points of successive cross sections of a water course
3.37
unit discharge
discharge per unit width
q
u
discharge through a unit width of a given vertical section
3.38
yield specific discharge
q
discharge per unit area of catchment or aquifer
3.39
stream gauging
discharge measurement
flow measurement
stream flow measurement
river gauging
all of the operations necessary for the measurement of discharge of a stream
3.40
gauge
device installed at a gauging station for measuring the level of the surface of water relative to a datum
3.41
left bank
bank to the left of an observer looking downstream
3.42
right bank
bank to the right of an observer looking downstream
3.43
invert
stream bed
stream bottom
channel bed
channel bottom
lower part of the stream channel situated between the banks
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3.44
bed slope
bottom slope
S
o
difference in elevation of the bed per unit horizontal distance, measured in the direction of flow
Note 1 to entry: The slope is usually mathematically negative in the direction of flow
3.45
bed profile
shape of the bed in a vertical plane
3.46
side slope
difference in elevation between the bottom and top of bank per unit horizontal distance
3.47
surface slope
S
w
inclination of the surface of the stream in a reach measured in the direction of flow
3.48
fall
difference in elevation of the water surface between the extremities of a defined reach at a given instant
of time, for example as recorded at a twin-gauge station
3.49
top width
width of the open channel measured across the stream at the water surface normal to the direction of
flow
3.50
wetted perimeter
P
w
contact length between a stream of flowing water and its containing open channel, measured in a
direction normal to the flow
3.51
cross section
section normal to the mean direction of flow bounded by the free surface and wetted
perimeter
3.52
gauging section
measuring section
section at which discharge measurements are taken
3.53
high water mark
flood mark
mark left on a structure or any other object indicating exceptional stages of flood
3.54
debris line
trash line
traces of any kind left on the banks or obstacles or flood plain by a flood
Note 1 to entry: The debris line may be used to determine the highest level attained by the water surface during
a flood.
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3.55
surface velocity
flow velocity at the surface at a given point
3.56
mean velocity
flow velocity at a given cross section of a stream, obtained by dividing the discharge
by the cross-sectional area
3.57
slush ice
mass of loosely packed anchor ice that is released from the bottom, or frazil ice that floats or accumulates
under surface ice
3.58
velocity head
theoretical vertical height to which a liquid particles can be elevated by its kinetic energyIt is expressed
as the square of the velocity divided by twice the acceleration due to gravity
3.59
gauged head
elevation of the free surface above the horizontal datum of a section
3.60
total head
energy head
H
sum of the elevation of the free surface above the horizontal datum of a section plus the velocity head
based on the mean velocity at that section
Note 1 to entry: The total head, H, is given by the following equation:
2
v
Hh=+α
2g
where
H is the gauged head of water level;
v
is the mean velocity of the water;
Α is the Coriolis coefficient;
G is the acceleration due to gravity.
The Coriolis coefficient (α ≥ 1), also known as energy coefficient or energy correction factor, takes into
account the non-uniform velocity distribution. In many cases, αis assumed to equal unity
3.61
total head line
energy head line
plot of the total head in the direction of flow
3.62
energy gradient
difference in total head per unit horizontal distance, measured in the direction of flow
3.63
energy loss
head loss
difference in total head between two cross sections in the direction of flow
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3.64
stage
gauge height
water level
elevation of the free surface of a stream, lake or reservoir relative to a specified datum
3.65
reference gauge
stage gauge that discharge is normally linked to
3.66
stage-discharge relation
rating curve
rating table
equation, curve or table that expresses the relation between the stage and the discharge in an open
channel at a given cross section
3.67
hydrograph
graphical representation of changes of hydrometric parameters with respect to time
Note 1 to entry: Typically, stage and discharge hydrographs are used for open channel flows.
3.68
cumulative volume curve
curve in which the cumulative value of a hydrometric parameter is plotted against time
Note 1 to entry: Integral of the hydrograph, e.g. cumulative discharge curve
3.69
storage curve
table
curve depicting the volume of stored water plotted against stage
3.70
gauging station
site on a stream, river or lake at which systematic measurements of stage, velocity or discharge or any
combination of the three are made
3.71
slope station
twin-gauge station
gauging station at which two water-level gauges define a reach for measurement of water-surface slope
as an essential parameter for establishing a stage-discharge relation
3.72
control
physical properties of a cross section or a reach of an open channel, either natural or artificial, that
govern the relation between stage and discharge at a location in the open channel
3.73
rating
relation between discharge and other variables, or the taking of observations and making of calculations
needed to establish the relation
3.74
unit-fall rating
relation between stage and discharge when the fall is equal to one
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3.75
afflux
rise in water level immediately upstream of, and due to, an obstruction
3.76
backwater curve
profile of water surface, along an open channel, from the raised surface at an obstruction or confluence
to the point upstream at which the flow is at normal depth
Note 1 to entry: The term is also used to denote all liquid surface profiles that are non-uniform with respect to
distance upstream or downstream. However, this usage is deprecated
3.77
drawdown curve
profile of the liquid surface when its surface slope (S ) exceeds the bed slope(S )
w o
Note 1 to entry: From the point at which the bed slope increases, or drops abruptly, to the point at which normal
depth occurs, the profile along an open channel is convex upwards in an upstream direction and concave upwards
in a downstream direction.
3.78
depth
D
linear dimension measured in the vertical direction from the water surface to the bed
3.79
peak stage
maximum instantaneous stage during a given period
3.80
friction
drag
boundary shear resistance that opposes the flow of a liquid
3.81
conveyance
K
carrying capacity of a channel
Note 1 to entry: The term “conveyance factor” is used also in the form
−12/
KQ= S
where
K is the conveyance factor;
Q is the total discharge;
S is the energy gradient.
3.82
hydraulic jump
sudden transition from supercritical flow to subcritical flow
Note 1 to entry: Immediately upstream of the hydraulic jump, the velocity and the depth are respectively greater
and less than their critical values; beyond the jump, the velocity and the depth are respectively less and greater
than their critical values.
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3.83
hydraulic mean depth
mean depth
D
m
area of the cross section of water flowing in an open channel divided by the width of the open channel
at the water surface
3.84
hydraulic radius
r
h
cross-sectional area of water flowing in an open channel divided by the length of the wetted perimeter
at that cross section
3.85
gauge datum
elevation of the zero of the gauge to which the level of the liquid surface is referred
Note 1 to entry: The gauge datum is related to a benchmark.
3.86
benchmark
permanent mark, the elevation of which should be related, where practicable, to a national datum
3.87
gauge/float well
stilling well/tube
chamber open to the atmosphere and connected with the stream in such a way as to permit the
measurement of the stage in relatively still water
3.88
roughness coefficient
coefficient that characterizes the roughness of the channel cross section and which is taken into account
when computing the resistance to flow or the energy gradient
Note 1 to entry: The common types are the Manning’s/Stricklern, ChezyC or an element roughness height, k.
3.89
Froude number
Fr
mean velocity divided by the square root of the product of the hydraulic mean depth and the acceleration
due to gravity
v
Fr=
12/
gD
()
m
where
v
is the mean velocity of the liquid;
g is the acceleration due to gravity;
D is the hydraulic mean depth of the cross section.
m
Note 1 to entry: The Froude number is dimensionless.
3.90
Reynolds number
Re
ratio of the forces of inertia to forces of viscosity
Note 1 to entry: For open channels,
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vr
h
Re=
η
where
v
is the mean velocity of the liquid;
r is the hydraulic radius of the cross section;
h
η is the kinematic viscosity of the liquid.
Note 2 to entry: The Reynolds number is dimensionless.
3.91
free surface flow
flow within a closed or open conduit, under gravity and having a free surface
Note 1 to entry: Where the flow exceeds the free surface capacity of the conduit, the flow will become surcharged
with the consequent disappearance of the free surface. Instances of surcharging of short duration do not normally
affect the overall concept of free surface flow in closed conduits.
3.92
hydrological cycle
constant movement of water in all states of its form, above, on and below the earth’s surface
3.93
hydrogeology
study of subsurface water in its geological context
3.94
live storage
reservoir storage which can be drawn off for users downstream
3.95
total storage
reservoir storage between the lowest bed level and the top water level
3.96
flood storage
volume of water temporarily held above the top water level of a reservoir during a flood event
Note 1 to entry: Flood storage is not retained in the reservoir but is discharged through an overflow until the
normal top water level is reached.
3.97
standing wave
stationary wave
curved symmetrically shaped wave on the water surface and on the channel bed, that are virtually
stationary
Note 1 to entry: When standing waves form, the water surface and the bed surfaces are roughly parallel and
in phase.
3.98
tributary
surface or underground stream which contributes its water, continuously or intermittently, to another
large or larger stream
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3.99
river delta
reach of a river when it approaches a body of quieter water with very gradual bed slope (S ) and surface
o
slope (S ), and, at low velocity, deposits its sediment and divides out into channels on either side of the
w
deposits, resulting in the formation of deltas
3.100
annual flood
highest momentary peak discharge, recorded at the respective point of observation, which is equaled
or exceeded once every year
3.101
annual storage within-the-year storage
difference between the maximum and minimum volumes in storage over a year of reservoir operation
3.102
base flow
sustained flow of stream resulting from outflow of groundwater and from drainage of large lakes
and swamps
Note 1 to entry: Base flow includes water sustained in glaciers, snow and other sources, not a result of direct runoff.
3.103
drainage basin
catchment
part of the land area enclosed by a topographic divide from which direct surface runoff from
precipitation drains by gravity into a stream or other water body
3.104
frazil ice
fine spicules, plates or discoids of ice suspended in water that are generally formed by the supercooling
of turbulent water
Note 1 to entry: Frazil ice may float or accumulate under ice cover or adhere to the stream bed as anchor ice.
3.105
anchor ice
submerged ice found attached to the bed, irrespective of the nature of its formation
3.106
rime ice
white mass of tiny ice crystals or granular ice tufts formed on exposed objects due to atmospheric
moisture
3.107
surface ice
ice cover
ice sheet
layer of ice formed on the surface of a lake or river
3.108
flow regime
state of flow in alluvial streams characterized by a bed configuration of ripples, dunes (lower regime),
plane bed (transition), standing waves and antidunes (upper regime)
Note 1 to entry: The lower-regime flow is subcritical; the upper-regime flow is supercritical.
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3.109
dune
large bed form having a triangular profile, a gentle upstream slope and a steep downstream slope.
Note 1 to entry: Dunes are formed in quiet flow and thus are out of phase with any water surface disturbance that
they may produce. They travel slowly downstream as sand is moved across their comparatively gentle upstream
slopes and deposited on their steeper downstream slopes
3.110
antidune
bed form of a curved symmetrically shaped sand wave that may move upstream, remain stationary or
move downstream
Note 1 to entry: Antidunes are curved in a wave train but they are in phase and interact strongly with gravity
water surface waves.
3.111
ripple
small triangular-shaped bed form similar to a dune
Note 1 to entry: Ripples have much smaller and more uniform amplitudes and lengths than dunes. Ripple
wavelengths are less than 0,6 m and wave heights are less than 0,06 m.
3.112
transition
crossover
inflection reach between two meander loops in which the main flow crosses from one side of the
channel to the other
Note 1 to entry: The depth of flow in a transition is usually reduced from normal depth and is more uniform than
in the curved reach.
3.113
velocity
speed of flow past a point in a specified direction
3.114
gauge height of zero flow
highest point on the thalweg downstream from the gauge in a natural or artificial channel
3.115
shift adjustment
correction made to the recorded stage to compensate for vertical movement of the bed or for shifting of
the control
...