Investigating variations between old and new school flow measurement techniques, and the potential to combine the two

James Newett - Hydro Tasmania , 31 March, 2021

Hydro Tasmania has frequently found using Acoustic Doppler Current Profiling (ADCP) technology for flow gauging to be inconsistent and inaccurate within concrete rectangular canals when compared to traditional Current Meter (CM) measurements.

By directly comparing ADCP and CM gaugings using the same discharge calculation techniques at two monitoring stations, it was found that ADCP and CM measurement techniques produced results more consistent than previously observed. Both techniques were then combined to form a hybrid gauging where CM velocity measurements were supplemented into those measurements captured by the ADCP.

Although this process requires further investigation, initial observations suggest ADCP velocity cells, measured using the stationary method within canals, closely resemble those of the CM. Information also suggests historical discrepancies may have been due to compass errors and the incorrect operation of the ADCP. Tests highlighted the potential to blend measurement styles, however simply adjusting the ADCP’s coordinate system where compass errors occur appeared the more time effective strategy for the accurate measurement of  flow at the study locations.