FAQs & Top Tech Issues
SonTek-SL: Using beam velocity data for QA/QC
The individual beam velocities should mirror each other (Figure 1) if the measurement site and installation complies with the specified requirements. It is expected that the beam velocities will not mirror each other exactly and it is acceptable if there are small variations between the two beams.
When using the beam velocities to analyze the data it is recommended that the data is evaluated over an extended period to identify a change in the data trend between the two beams. Evaluating a short period (couple of days) could be misleading. There are number of factors that can result in a difference between the beam velocities (Figure 2),
a) Vegetation or debris impacting the measurement volume of one of the beams,
b) Sediment deposition or sand bars moving downs stream that is impacting the measurement volume,
c) Algae or Biological growth on one of the transducers,
d) One beam interacting with water surface or channel bed
e) Fish presence in measurement volume.
It is important to note that Beam Velocities should not be used independently to review the data quality and that it should be used in conjunction with Standard Deviation of Velocity, Stage (Vertical Beam \ Pressure Sensor) versus Flow and BeamChecks data.