ISO 1438-2017 PDF

Full title and description

St ISO 1438-2017 — Hydrometry — Open channel flow measurement using thin-plate weirs. This International Standard (Edition 3, 2017) specifies requirements and guidance for using rectangular and triangular (V‑notch) thin‑plate weirs to measure flow of clear water in open channels under free‑flow conditions and provides requirements for full‑width rectangular thin‑plate weirs used in submerged (drowned) flow conditions.

Abstract

ISO 1438:2017 defines use, installation and measurement requirements for thin‑plate weirs (rectangular and V‑notch) for hydrometric discharge measurement in open channels. It covers free‑flow conditions and also addresses the application of full‑width rectangular thin‑plate weirs under submerged conditions, providing formulae, coefficients, and practical requirements for reliable measurement.

General information

• Status: Published (current; edition confirmed on review).
• Publication date: 2 May 2017 (Edition 3, 2017).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.120.20 (Flow in open channels).
• Edition / version: Edition 3 (2017).
• Number of pages: 60 pages.

Key bibliographic and lifecycle details above are taken from the ISO record for ISO 1438:2017 (technical committee ISO/TC 113/SC 2). The edition was published in 2017 and the standard was reviewed and confirmed in a subsequent ISO review cycle.

Scope

ISO 1438:2017 applies to the measurement of discharge in open channels using thin‑plate weirs. It defines acceptable weir geometries (rectangular sharp‑crested and triangular V‑notch), limits of applicability (free‑flow conditions and selected submerged full‑width rectangular cases), instrumentation and head‑measurement procedures, calibration/verification practices and installation requirements intended to ensure reproducible, accurate discharge determinations.

Key topics and requirements

• Defined weir types and geometries: rectangular (sharp‑crested) and triangular (V‑notch) thin‑plate weirs, including recommended notch angles and dimensional tolerances.
• Head–discharge relations and standard discharge coefficients for the specified geometries; required corrections and effective head definitions for use in calculation formulas.
• Distinction between free‑flow and submerged (drowned) conditions and procedures to determine / correct for submergence effects.
• Installation and approach‑channel requirements (approach flow uniformity, stilling wells or measuring arrangements, cleaning and maintenance) to minimise measurement bias and variability.
• Calibration, verification and testing procedures, plus guidance on assessing uncertainty and expected accuracy for routine measurements.
• Fabrication, surface finish and edge condition recommendations for thin‑plate weirs to ensure sharp crests and reduce clinging or capillary effects at low heads.

The points above summarise the principal technical content and requirements set out in ISO 1438:2017 and reflect standard hydrometry practice and installation guidance used by water measurement agencies.

Typical use and users

Typical users include hydrologists, water‑resources and irrigation engineers, environmental and regulatory agencies, field hydrographers, laboratories that calibrate gauging structures, and manufacturers/suppliers of gauging equipment. The standard is used to design, install, operate and validate thin‑plate weir installations for routine and research flow measurement in open channels. Practical installation and operational guidance aligns with broader hydrometry practice such as governmental water‑measurement manuals.

Related standards

ISO 1438 sits within the ISO hydrometry family (ICS 17.120.20). Commonly referenced related standards include ISO 9826:1992 (Measurement of liquid flow in open channels — Parshall and SANIIRI flumes) and ISO 748:2021 (Velocity‑area methods using point velocity measurements), among other hydrometry documents that cover alternative gauging structures, velocity methods and uncertainty guidance. Practitioners often consult these standards together when selecting measurement methods and performing uncertainty assessments.

Keywords

Thin‑plate weir, rectangular weir, V‑notch (triangular) weir, hydrometry, open channel flow, discharge measurement, free‑flow, submerged flow, weir coefficient, calibration, approach channel, flow gauging.

FAQ

Q: What is this standard?

A: ISO 1438:2017 is an international standard that specifies requirements and guidance for measuring discharge in open channels using thin‑plate (sharp‑crested) rectangular and triangular (V‑notch) weirs.

Q: What does it cover?

A: It covers acceptable weir geometries, head–discharge relationships and coefficients, installation and approach channel requirements, treatment of submerged conditions (for full‑width rectangular weirs), calibration and verification procedures, and guidance on fabrication and maintenance to ensure accurate measurements.

Q: Who typically uses it?

A: Hydrologists, water‑resources and irrigation engineers, hydrographic teams, environmental agencies, standards‑based laboratories, and manufacturers/suppliers of gauging structures use ISO 1438 for design, installation, operation and validation of weir‑based flow measurement.

Q: Is it current or superseded?

A: ISO 1438:2017 (Edition 3) is the current published edition; the ISO record indicates the 2017 edition was reviewed and its status confirmed in ISO’s review cycle. It replaced earlier versions (ISO 1438:2008 and its corrigenda). Users should check national adoption or later ISO review notices for any amendments.

Q: Is it part of a series?

A: Yes — ISO 1438 is part of the ISO hydrometry suite of standards (ICS 17.120.20). Related documents include standards for flumes (ISO 9826), velocity‑area methods (ISO 748) and other hydrometry guidance covering uncertainty and vocabulary. These documents are often used together when planning and performing open‑channel flow measurements.

Q: What are the key keywords?

A: Thin‑plate weir; rectangular weir; V‑notch; hydrometry; open channel; discharge; weir coefficient; submerged flow; calibration; approach channel.