ISO TR 11656-1993 PDF

Full title and description

St ISO TR 11656-1993 — Measurement of liquid flow in open channels — Mixing length of a tracer. A Technical Report that investigates cross‑channel mixing characteristics of solutes (tracers) injected into streams and the implications for dilution‑based discharge measurement methods.

Abstract

Examines methods for defining the degree of mixing, compares methods to estimate the mixing length of a tracer in open channels, quantifies errors in dilution discharge measurements caused by incomplete mixing, and discusses procedures to reduce those errors. Includes statistical data from field studies and annexes comparing observed and calculated mixing distances.

General information

• Status: Withdrawn.
• Publication date: June 1993 (published 2 June 1993).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.120.20 — Flow in open channels.
• Edition / version: Edition 1 (1993-06).
• Number of pages: 41.

Scope

Provides guidance and recommendations on how to define and estimate the mixing length of tracers in open channels for use in dilution‑based discharge measurements. The report addresses measurement errors arising from incomplete lateral and vertical mixing, compares different quantitative definitions of mixing, presents calculation and observational methods for estimating mixing distance, and suggests procedures to reduce bias and uncertainty in dilution methods. It is focused on hydrometric applications where tracers are used to determine discharge in rivers, streams and artificial open channels.

Key topics and requirements

• Definitions and metrics for the degree of mixing (cross‑sectional and lateral mixing measures).
• Methods to estimate mixing length from field observations and theoretical relations.
• Analysis of errors in dilution discharge measurements resulting from incomplete mixing.
• Recommendations to reduce measurement bias (e.g., injection procedures, sampling locations, tracer selection, and required downstream distances before sampling).
• Statistical summaries and comparison of observed versus calculated mixing distances (annex data and worked examples).

Typical use and users

Hydrometric engineers and technicians, river and water resources researchers, environmental monitoring teams, consultants performing dilution‑based discharge measurements, and governmental water agencies. The report is intended as a practical reference for planning tracer injections, locating sampling stations, estimating uncertainty of dilution methods, and interpreting tracer concentration data in open‑channel flow studies.

Related standards

Part of the hydrometry/flow‑in‑open‑channels family of ISO documents. Relevant related standards and technical reports include ISO standards and TRs on hydrometry and dilution/flow measurement methods (for example the ISO 1100 series (measurement of liquid flow in open channels), ISO 9196 (flow measurements under ice conditions), ISO 9825 (field measurement of discharge in large rivers) and earlier ISO documents on dilution methods such as the ISO 555 series). These documents are produced under ISO/TC 113 (Hydrometry) and provide complementary guidance on discharge measurement techniques and gauging‑station practice.

Keywords

mixing length, tracer, dilution method, open channel, hydrometry, discharge measurement, incomplete mixing, tracer injection, uncertainty, gauging

FAQ

Q: What is this standard?

A: ISO/TR 11656:1993 is a Technical Report that documents methods for defining and estimating the mixing length of a tracer in open channels and discusses the impact of incomplete mixing on dilution‑based discharge measurements.

Q: What does it cover?

A: It covers comparison of mixing‑definition methods, estimation procedures for mixing length, quantification of errors in dilution measurements when mixing is incomplete, and practical recommendations to reduce those errors; it also includes annexed field data and comparison tables.

Q: Who typically uses it?

A: Hydrometric practitioners, water resource engineers, environmental scientists, consultants and agencies performing tracer/dilution discharge measurements or researching mixing in open channels.

Q: Is it current or superseded?

A: The document is recorded as Withdrawn by ISO. Users should check current ISO hydrometry publications and the ISO/TC 113 work programme for up‑to‑date standards covering dilution methods and open‑channel discharge measurement.

Q: Is it part of a series?

A: It sits within the ISO hydrometry portfolio (ISO/TC 113) and is related to other ISO standards and technical reports on open‑channel flow measurement (for example ISO 1100 series, ISO 9196, ISO 9825 and documents addressing dilution methods).

Q: What are the key keywords?

A: Mixing length, tracer, dilution method, open channel, discharge measurement, hydrometry, incomplete mixing, uncertainty.