Precise ISO 748:2021 flow measurement of surface water bodies made easy

NIVUS’ patented cross correlation technology was included in the 2021 edition of ISO 748 (Hydrometry — Measurement of liquid flow in open channels — Velocity area methods using point velocity measurements) within the category of accepted Acoustic Echo Correlation Velocimeters (AECVs). This enables environmental agencies, responsible for conducting water discharge measurements to monitor velocity and the cross-section area in open channels with confidence.

The NivuFlow Stick acoustic echo correlation velocimeter is simple to operate, dependable, precise and conforms to ISO 748 criteria. NIVUS’ state-of-the-art multipoint-measurement, acoustic echo correlation velocimeter measures the water’s full flow velocity profile, with automatic velocity measurements taken from the floor of the channel to the surface. The multipoint measurements provide a considerably more precise discharge and velocity profile and save time by eliminating the need to take several measurements at different sampling depths by repositioning the instrument. 

This instrument provides simultaneous measurement of up to 32 velocity ‘windows’ within each vertical section measurement provides the user with a full understanding of the velocity curve and greater information and understanding of how the average velocity is calculated within the vertical section.

Each vertical surface to bottom measurement consists of data obtained from simultaneous measurements of up to 32 ‘velocity windows’. This data provides the operator with a comprehensive profile of velocity curves and average flow velocity. The unit display indicates single velocity measurements as well as the flow velocity curve, the individual measurements are collated to show a complete channel velocity profile for the whole location being monitored. A built-in hydrostatic level monitor measures the depth and a profile of the riverbed is also determined and displayed to the operator.

The NivuFlow Stick automatically computes the total discharge according to both the mean-section and mid-section methods, once all of the vertical measurements have been completed. Finally, a complete PDF measurement report is generated by the instrument; this includes data on the cross-sectional area, discharge levels in each section, average velocity and water depth calculated from the vertical measurements and a graphic display representing the flow profile.