ISO 2425:2010

Overview

ISO 2425:2010 - Hydrometry: Measurement of liquid flow in open channels under tidal conditions - summarizes recommended methods for determining flow in tidal channels. It addresses techniques that are unique to or particularly appropriate for tidal environments, including guidance on uncertainty estimation. ISO 2425:2010 specifies both single and continuous measurement approaches and cross-references other hydrometry standards where alternative methods are described.

Key topics and technical requirements

• Measurement categories
  • Single measurements: velocity–area methods (fixed or moving current meters, acoustic Doppler devices) and the cubature method (volume storage/area change calculations; see Annex A).
  • Continuous measurements: ultrasonic (ISO 6416), electromagnetic (ISO 9213) and acoustic Doppler velocity meters (ADVMs) mounted horizontally or vertically at fixed stations; unsteady flow models are also covered for continuous discharge computation.
• Instrumentation referenced
  • Current meters, ADVM/ADCP/ADP, ultrasonic transducers, electromagnetic gauges.
  • Annex D gives specific guidance on tidal flow measurement using acoustic Doppler velocity meters.
• Site selection and practical constraints
  • Requirements for gauging sites (accessibility, avoidance of vortices, vegetation, ice).
  • Consideration of channel geometry, width/depth variation, tidal range, and river traffic.
• Special tidal considerations
  • Flow reversal, backwater effects, spatial and temporal velocity gradients, stratification (salt–water wedge), phase differences between level and flow reversal.
  • Effects on acoustic and electromagnetic methods due to salinity, temperature, sound-speed and conductivity changes.
• Uncertainty treatment
  • Emphasis on higher uncertainties in tidal conditions vs unidirectional flow and the need for increased measurement frequency and careful error analysis (detailed in Clause 8).

Applications and users

ISO 2425:2010 is intended for professionals and organizations involved in tidal hydrometry and water-resources monitoring, including:

• Hydrologists and hydrographic survey teams
• Water-resources and coastal engineers
• Environmental agencies monitoring estuarine and tidal flows
• Port and harbour authorities, flood risk managers
• Research institutions studying estuarine dynamics and transport processes

Practical applications include tidal discharge estimation, salt-wedge and stratification studies, flow monitoring for ecological assessments, calibration of numerical unsteady flow models, and establishment/operation of tidal gauging stations.

Related standards

• ISO 748 - Velocity–area methods (current meters/floats)
• ISO 6416 - Ultrasonic (acoustic) method
• ISO 9213 - Electromagnetic method
• ISO 1100-1 - Establishment and operation of a gauging station
• ISO 772 - Hydrometry vocabulary and symbols

Keywords: ISO 2425:2010, hydrometry, tidal flow measurement, open channels, velocity-area, cubature method, ADVM, ADCP, ultrasonic, electromagnetic, tidal gauging, uncertainty.