Overview
ISO 9555-3:1992 - "Measurement of liquid flow in open channels - Tracer dilution methods for the measurement of steady flow - Part 3: Chemical tracers" - specifies the use of chemical tracers (for example iodide, lithium, chloride, chromium) for discharge measurement in open channels using tracer-dilution methods. It complements ISO 9555-1 (general principles) and addresses tracer selection, field and laboratory measurement techniques, sampling, injection methods, environmental influences and sources of error for steady (and slowly varying) flows.
Key topics
- Tracers covered: common chemical tracers (iodide, lithium, chloride, chromium) and notes on other possible tracers (bromide, fluoride, manganese sulfate, nitrate).
- Measurement principles: constant-rate injection and integration (sudden injection) approaches as applied to chemical tracers (reference ISO 9555-1 for general procedures).
- Analytical methods:
- Catalytic spectrophotometry and ion-selective electrodes for iodide.
- Flame atomic absorption/emission techniques and other laboratory analyses for lithium and chromium; calorimetric methods for hexavalent chromium with options for sample reconcentration to improve detection limits.
- Conductivity method commonly used for chloride (sodium chloride) in the field.
- Field vs laboratory: guidance on in-situ measurement (e.g., ion-selective electrodes, conductivity meters) and laboratory assays that may require dilution or reconcentration of samples.
- Environmental factors: chemical (interferences), physical (mixing, solubility, density segregation), and biological influences that affect tracer behaviour and measurement accuracy.
- Injection & sampling techniques: recommended approaches to ensure homogeneous mixing and representative sampling.
- Error sources & quality control: background concentrations, matrix effects (colour, turbidity), electrode interferences, calibration needs and steps to minimise contamination and analytical bias.
- Special requirements: handling, toxicity and storage considerations for specific tracers.
Applications and users
- Practical for hydrologists, environmental engineers, water resource managers, field technicians and analytical laboratories conducting discharge measurements of rivers, streams, canals and industrial effluents.
- Useful where conventional flow metering is impractical (complex cross-sections, turbulent or unsteady conditions, flood events) or where non-invasive tracer dilution yields safer, reliable estimates.
- Applicable to studies requiring trace-level detection, budgeted tracer use, or when site-specific background conductivity/chemistry requires custom calibration.
Related standards
- ISO 9555-1: General principles (constant-rate and sudden injection methods)
- ISO 9555-2: Radioactive tracers
- ISO 9555-4: Fluorescent tracers
- ISO 772: Vocabulary and symbols for liquid flow measurement in open channels
Keywords: ISO 9555-3:1992, tracer dilution methods, chemical tracers, open-channel flow measurement, iodide, lithium, chloride, chromium, conductivity method, ion-selective electrode, sample reconcentration, discharge measurement.
Open preview (PDF)Measurement of liquid flow in open channels — Tracer dilution methods for the measurement of steady flow — Part 3: Chemical tracers