Overview
ISO 9196:1992 - Liquid flow measurement in open channels: Flow measurements under ice conditions - provides guidance for measuring water discharge and stage in rivers and channels subject to ice and slush. The standard describes four water discharge measurement methods and two water stage measurement methods, illustrates principles with figures, and gives practical details for winter gauging that supplement other open‑channel flow standards. Keywords: ISO 9196, flow measurement, open channels, ice conditions, winter gauging.
Key topics and technical requirements
- Scope and purpose: Guidance for reliable discharge measurement when channels are partially or fully ice‑covered, including special problems arising from slush, ice layers and flow above or below the ice.
- Methods of discharge measurement: The text explains methods such as the velocity–area method, representative‑vertical approaches, use of notches, weirs and flumes, and dilution/tracer techniques (referencing ISO 555‑1/2).
- Site selection and limitations: Criteria for acceptable gauging sites under ice (avoid sites with >25% slush filling, dead zones >10% of cross‑section, multilayered ice, or substantial braided channels that change flow distribution).
- Ice and slush measurement: Procedures for measuring ice cover thickness, slush depth and determining effective depth (water depth beneath ice/slush) using sticks, rods, drilled holes and sounding weights.
- Velocity measurement under ice: Use of current meters lowered through drilled holes or specialized arm‑rotating installations; guidance on vertical selection, minimum number of holes (typical practice: ~20 holes to represent profile), and point sampling schemes (one‑point, two‑point, three‑point, or six‑point) with appropriate velocity coefficients.
- Computation rules: Compute discharge using effective depth and standard open‑channel calculation rules (as per ISO 748), treat flows above and below ice separately, and avoid sites with multilayered ice.
- Safety and operational notes: Ice strength testing, safe working limits, flotation/airborne methods for drifting ice, and practical tips to prevent instrument freezing.
Applications and users
ISO 9196 is intended for:
- Hydrologists and field gauging teams performing winter river measurements
- Water resource and flood forecasting agencies
- Hydropower operators and environmental monitoring programs
- Engineers conducting river discharge studies where ice cover affects flow
Use cases include seasonal discharge records, calibration of stage–discharge relations under ice, winter water balance studies, and emergency gauging during ice jams or spring melt.
Related standards (normative references)
The standard references and supplements other ISO documents, for example:
For reliable winter gauging, combine ISO 9196 procedures with the relevant open‑channel and instrumentation standards.
