ISO 748:2021
Hydrometry — Measurement of liquid flow in open channels — Velocity area methods using point velocity measurements
This document specifies methods for determining the velocity and cross-sectional area of water flowing in open channels and for calculating the discharge employing point velocity measurement devices.
It is applicable to methods using rotating-element current meters, acoustic doppler velocimeters (ADVs), acoustic doppler current profiler (ADCP) stationary method, surface velocity measurement including floats and other surface velocity systems.
Although some general procedures are discussed, this document does not describe in detail how to use or deploy these systems.
NOTE For detailed procedures, refer to guidelines from instrument manufacturers and the appropriate public agencies.
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Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Principle of the methods of measurements
5 Site selection
5.1 Selection of site
5.2 Demarcation of site
6 Measurement of cross-sectional area
6.1 General
6.2 Measurement of width
6.3 Measurement of depth
7 Measurement of mean velocity
7.1 Determination of mean velocity using point velocity measurements
7.1.1 General
7.1.2 Measurement procedure
7.1.3 Oblique flow
7.1.4 Determination of the mean velocity in a vertical
7.1.5 Integration method
7.1.6 Errors and limitations
7.2 Determination of mean velocity from surface velocity
7.2.1 General
7.2.2 Non-contact systems
7.2.3 Surface one-point method by current meter
7.2.4 Measurement of velocity using floats
7.2.5 Exceptions
7.2.6 Main sources of error
8 Computation of discharge
8.1 Arithmetic methods
8.1.1 General
8.1.2 Mean-section method
8.1.3 Mid-section method
8.1.4 Bathymetric verticals
8.2 Independent vertical method
8.3 Mean-section method — Horizontal planes
9 Uncertainties in flow measurement
9.1 General
9.2 Method of calculating the uncertainty in discharge by measurement of velocity by current meter
9.2.1 General
9.2.2 Contributory uncertainties
9.3 Method of calculating the uncertainty in discharge by measurement of velocity using floats
9.3.1 General
9.3.2 Contributory uncertainties
9.3.3 Combined uncertainty in discharge
9.4 Limitations
9.5 Interpolated variance estimator (IVE)
9.6 Q+
9.7 Flaure
Annex A (informative) Use of point velocity current meters
Annex B (informative) Surface velocity measurement using floats
Annex C (informative) Example surface velocity systems
Annex D (informative) Uncertainties in the velocity-area measurement
Annex E (informative) Velocity measurement under ice conditions
Annex F (informative) Corrections for wetted length of wire when measuring depths with wire not normal to surface
Bibliography
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Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Principle of the methods of measurements
5 Site selection
5.1 Selection of site
5.2 Demarcation of site
6 Measurement of cross-sectional area
6.1 General
6.2 Measurement of width
6.3 Measurement of depth
7 Measurement of mean velocity
7.1 Determination of mean velocity using point velocity measurements
7.1.1 General
7.1.2 Measurement procedure
7.1.3 Oblique flow
7.1.4 Determination of the mean velocity in a vertical
7.1.5 Integration method
7.1.6 Errors and limitations
7.2 Determination of mean velocity from surface velocity
7.2.1 General
7.2.2 Non-contact systems
7.2.3 Surface one-point method by current meter
7.2.4 Measurement of velocity using floats
7.2.5 Exceptions
7.2.6 Main sources of error
8 Computation of discharge
8.1 Arithmetic methods
8.1.1 General
8.1.2 Mean-section method
8.1.3 Mid-section method
8.1.4 Bathymetric verticals
8.2 Independent vertical method
8.3 Mean-section method — Horizontal planes
9 Uncertainties in flow measurement
9.1 General
9.2 Method of calculating the uncertainty in discharge by measurement of velocity by current meter
9.2.1 General
9.2.2 Contributory uncertainties
9.3 Method of calculating the uncertainty in discharge by measurement of velocity using floats
9.3.1 General
9.3.2 Contributory uncertainties
9.3.3 Combined uncertainty in discharge
9.4 Limitations
9.5 Interpolated variance estimator (IVE)
9.6 Q+
9.7 Flaure
Annex A (informative) Use of point velocity current meters
Annex B (informative) Surface velocity measurement using floats
Annex C (informative) Example surface velocity systems
Annex D (informative) Uncertainties in the velocity-area measurement
Annex E (informative) Velocity measurement under ice conditions
Annex F (informative) Corrections for wetted length of wire when measuring depths with wire not normal to surface
Bibliography