ISO/TR 11330:1997

TECHNICAL ISOKR
REPORT 11330
First edition
1997-09-01
Determination of volume of water and water
level in lakes and reservoirs
Dhtermination du volume et du niveau d’eaux dans /es lacs et r&en/oh
Reference number
ISO/TR 11330: 1997(E)

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lSO/TR 11330:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical 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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International
Standards, but in exceptional circumstances a technical committee may
propose the publication of a Technical Report of one of the following types:
- type 1, when the required support cannot be obtained for the
publication of an International Standard, despite repeated eff or%;
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility of
an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International Standard
(“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they can be transformed into International
Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or
useful.
ISO/TR 11330, which is a Technical Report of type 2, was prepared by
Technical Committee ISO/TC 113, Hydrometric determinations, Subcom-
mittee SC 1, Velocity-area methods.
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
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Printed in Switzerland
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@IS0 ISO/TR 11330: 1997(E)
This document is being issued in the Technical Report (type 2) series of
publications (according to subclause G.3.2.2 of part 1 of the ISO/IEC
Directives, 1995) as a “prospective standard for provisional application” in
the field of hydrometric determinations because there is an urgent need for
guidance on how standards in this field should be used to meet an
identified need.
This document is not to be regarded as an “International Standard”. It is
proposed for provisional application so that information and experience of
its use in practice may be gathered. Comments on the content of this
document should be sent to the IS0 Central Secretariat.
A review of this Technical Report (type 2) will be carried out not later than
three years after its publication with the options of: extension for another
three years; conversion into an International Standard; or withdrawal.
Annexes A and B of this Technical Report are for information only.

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lSO/TR 11330: 1997(E)
TECHNICAL REPORT o ~so
Determination of volume of water and water level in lakes
and reservoirs
1 Scope
This Technical Report deals with the survey of the topography of lakes and reservoirs for the determination of
volume of line storage and the determination of water level, the objective being to establish a relation between water
level and volume. Both conventional surveying methods and electronic distance measurement (EDM) and Global
Positioning System (GPS) total station methods are included.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
Technical Report. At the time of publication, the editions indicated were valid. All standards are subject to revision,
and parties to agreements based on this Technical Report are encouraged to investigate the possibility of applying
the most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently
valid International Standards.
IS0 772:1996, Hydrometric determinations - Vocabu!aty and symbols.
IS0 4366:1979, Echo sounders for water depth measurements.
IS0 4373: 1995, Measurement of liquid flow in open channels - Water-level measuring devices.
IS0 6420: 1984, Liquid flow measurement in open channels - Position fixing equipment for hydrometric boats.
3 Definitions and symbols
For the purpose of this Technical Report, the definitions and symbols given in IS0 772 and the following definitions
apply.
3.1 live storage: Storage which can be drawn off from the reservoir to downstream users.
3.2 total storage: Storage between the lowest bed level and top water level.
3.3 flood storage: Volume held above top water level during a flood event.
NOTE - Flood storage is not retained in the reservoir but is discharged until the normal top water level is reached.
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@ IS0
ISOITR 11330: 1997(E)
4 Topography survey and analysis
4.1 Procedure
The procedure adopted requires:
a) three-dimensional coordinates of points on the bed of the reservoir;
b) contoured bathymetric plans and topographic survey above top water level;
c) water level : volume curves or tables or both.
5 Volume determination by conventional surveying methods
5.1 Survey below water level
The sun/ey of that part of the lake or reservoir below the water surface requires a launch equipped with an echo
sounder. The position of the launch is fixed during echo sounder runs by means of a sextant or theodolite. Targets
are located at both ends of each section line in accordance with IS0 4366.
5.2 Choice of cross-sections
The chosen cross-sections should take into account the size and shape of the water body and should generally be
close enough for accurate calculation but not greater than 1 km apart. In general, the rule is to select range
locations such that the volumes computed by the average end-area method (the average cross-sectional area at
both ends of each lake reach multiplied by the length of the reach) reasonably represents the volume of the valley
between ranges.
5.3 Location of ranges
Ranges should be located such that the area of the polygon enclosed by the range end-points accurately
reproduces the area of the water body between adjacent ranges. This rule neglects errors arising from irregular
channel bottoms, but in most topography, the lake or reservoir bottom irregularity is frequently correlated with shore
irregularity. Where possible, cross-sections should be located near the mouths and heads of tributary arms.
5.4 Plotting contours
Contours should be plotted using all measured levels on the cross-sections, both below and above the water
surface. The scale of the plot will depend on the size of the water body, but a scale of I:200 or I:20000 should be
appropriate in most cases, with a vertical scale of 20 cm to 30 cm.
5.5 Calculation of volume
The plan area , enclosed by each contiguous contour should be calculated with a constant vertical interval between
each contour. The total volume can then be determined by a prismoidal end-area or other suitable method.
5.6 Water level during survey
When the survey is in progress, the opportunity should be taken to read the reference staff gauge(s) if available.
5.7 Use of conventional surveying
The conventional surveying method is now seldom used for volume determination of lakes or reservoirs whose
surface areas are greater than 500 km* and whose smallest linear dimension at top water level exceeds 10 km.
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@ IS0 lSO/TR 11330: 1997(E)
6 Volume determination by modern surveying methods
6.1 General
The advent of electromagnetic distance measurement (EDM) and computer software facilities in surveying, together
with the Global Positioning System (GPS), has virtually revolutionized land surveying.
6.2 The EDM Total Station method
A fully integrated survey system, consisting of a combination of theodolite, EDM equipment, data processor and
dedicated software gives X, y and z coordinates directly and encompasses everything from field observations to the
production of the final plans. This integrated system is known as the Total Station.
6.2.1 Water depth : volume curves
All survey data are transferred from the total station to an electronic notepad which allows input in the form of three-
dimensional coordinates. All data from topographic and sonar surveys are inserted into a computer with a dedicated
software package to produce contour plans and water depth : volume curves.
6.2.2 Range of EDM Total Station
The major advantage of EDM, apart from speed and accuracy, is that greater dist
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