ISO 1088:2007 PDF

Overview

ISO 1088:2007 - Hydrometry: Velocity-area methods using current‑meters provides a standardized basis for collecting and processing data to determine uncertainties in discharge measurements for open channels using point‑velocity (current‑meter) velocity‑area techniques. The standard defines how component measurements (velocity, depth, breadth) are combined, how their individual uncertainties are estimated, and how those component uncertainties are combined to give the total uncertainty in computed discharge. It adopts the statistical approach of the ISO/IEC Guide 98 (GUM) and is intended for discrete point‑velocity methods as described in ISO 748 (not for ADVP or continuous profiling systems).

Key topics and requirements

• Scope and intent: Applies to velocity‑area methods with point velocities at discrete depths and transverse positions; excludes Acoustic Doppler Velocity Profilers (ADVP) and continuous profilers.
• Component measurements: Procedures and uncertainty considerations for velocity, depth, and width (breadth) measurements.
• Types of error: Structured treatment of error types (notably Error‑type i, ii, iii) addressing issues such as time trends/responsiveness, approximation of mean velocity in verticals, and limited number of verticals.
• Statistical treatment: Use of standard uncertainties (standard deviations), combination rules and expanded uncertainty (coverage factor k = 2 ≈ 95% confidence) consistent with GUM.
• Data collection & reporting: Standardized procedures and report forms for local point velocities, average velocities, velocity‑area method data, calibration curves, distance and depth measurements.
• Data processing: Methods for estimating component uncertainties (type A evaluations), integration methods, and treatment of autocorrelation and measurement time effects.
• Supporting material: Annexes provide river data examples, measurement-report templates, examination of error types, and worked guidance for uncertainty calculation.

Applications

• River and stream gauging for hydrology and water resources management
• Flood forecasting and modelling where reliable discharge uncertainty is required
• Calibration and validation of gauging stations and rating curves
• Environmental assessments (sediment transport, habitat flow studies) needing quantified flow accuracy
• Regulatory compliance, water allocation and engineering design where documented measurement uncertainty is required

Who should use it

• Hydrologists and water resources engineers
• Gauging station operators and national hydrometric services
• Instrument manufacturers, calibration laboratories and metrology specialists
• Researchers performing field discharge measurements and uncertainty analysis

Related standards

• ISO 748 - Measurement of liquid flow in open channels: velocity‑area methods (measurement procedures)
• ISO/IEC Guide 98 (GUM) - Guide to the expression of uncertainty in measurement
• ISO 4363 / ISO 4364 - Related open‑channel sampling standards (suspended sediment and bed material)

Keywords: ISO 1088:2007, hydrometry, velocity-area methods, current-meter, discharge uncertainty, open channels, flow measurement.