ISO 24578:2021

Overview

ISO 24578:2021 - Hydrometry - Acoustic Doppler profiler - Method and application for measurement of flow in open channels from a moving boat provides authoritative guidelines for boat‑mounted Acoustic Doppler Current Profilers (ADCPs) used to determine single measurements of discharge in open channels. The document is generic (not equipment‑brand specific) and covers principles, deployment methods, data quality checks and uncertainty considerations for measuring current, velocity profiles and channel bathymetry from a moving boat.

Key topics and technical requirements

• Principles of ADCP operation: Doppler fundamentals, ADCP modes (pulse‑incoherent, pulse‑to‑pulse coherent, broadband) and speed‑of‑sound considerations.
• Velocity measurement: Methods to measure velocity profiles, relative velocity and boat velocity; handling near‑boundary data and bin definitions.
• Flow determination methods: General procedures for single discharge determinations and specific approaches for moving‑bed conditions without GNSS, including: stationary moving‑bed, azimuth, subsection correction, loop and mid‑section methods.
• Deployment and operation: Site selection criteria; deployment techniques (manned boat, tethered boat, remote‑control craft); recommended boat paths and speeds; field setup, data retrieval modes and ancillary equipment (GNSS, GNSS compass, etc.).
• Quality assurance: Built‑in diagnostics, beam‑alignment tests, periodic maintenance, training requirements and example checklists/field sheets.
• Uncertainty and data treatment: Sources of measurement uncertainty, methods to evaluate and minimize uncertainty, and guidance on extrapolating velocity near boundaries (informative annexes).
• Sediment and bathymetry: Guidance on using bottom‑track velocity for bedload indications and acoustic backscatter + the sonar equation for suspended sediment estimates.

Practical applications

• River gauging and flood monitoring: Rapid, reliable single measurements of discharge for stage‑discharge relationships and emergency assessments.
• Hydraulic and environmental studies: Flow mapping, velocity field surveys and channel bathymetry for modeling, restoration and habitat assessment.
• Sediment transport estimation: Qualitative/quantitative indicators of bedload and suspended sediment using bottom‑track and backscatter techniques.
• Operational monitoring: Routine gauging programs where boat‑mounted ADCPs provide faster coverage than traditional point gauges.

Who should use this standard

• Hydrologists, river/gauging station operators, water resource engineers, environmental consultants, ADCP equipment users and organizations responsible for hydrometry quality assurance and instrumentation deployment.

Related standards

• ISO 772 - Hydrometry: vocabulary and symbols (normative reference).
• ISO 24578:2021 replaces the previous technical report ISO/TR 24578 and is the primary reference for ADCP boat‑mounted flow measurement procedures.