Part 11: Application of surface velocity methods for velocity and open channel discharge measurements NI GL 100.11–2021

Water Monitoring Standardisation Technical Committee - Bureau of Meteorology , 07 October, 2021



The purpose of this document is to provide guidelines for recommended practice to ensure that the collected measured streamflow data are:

  1. accurate;
  2. defendable; and
  3. consistent across water monitoring organisations operating under these guidelines.

This is the minimum guideline that shall be followed to allow the collected data to withstand independent validation and integrity checks. Additional field procedures may vary between organisations.


This document deals with the application of surface velocity methods for determining velocity and discharge in open channels. It specifies the required procedures and methods for collecting and processing of surface water velocity data using image velocimetry and radar systems.

This document does not include or rewrite instrument manufacturers’ operating instructions for their individual instruments. Nor does it detail Standard Operating Procedures (SOPs) of organisations using these instruments. However, it is expected that those SOPs are sufficiently robust to withstand independent scrutiny and alignment with this document.

This document contains images and examples sourced from instrument manufacturers or suppliers. Inclusion of these images, with reference to the source, is solely for the purpose of providing examples, additional information and context, and is not to be interpreted as endorsement of any particular proprietary products or services.

This guideline is an original attempt to operationalise new methodologies in image velocimetry. To capture advancements in these evolving techniques this guideline is considered a living document. Feedback can be supplied to