Quicker, easier, more versatile
Acoustic Doppler current profilers (ADCPs) are transforming the way we gauge the flow of rivers.
Essentially, ADCPS are very sophisticated echo-sounders that measure not just depth, but the water velocities and the velocity at which the instrument itself moves across the bed.
All the paraphernalia of the past – width measurement lines, current meters, sounding weights – are redundant, and the difficulties of working from bridges are history. Now the readings from the ADCP are displayed on a laptop screen as we travel across the river.
By using an ADCP, we can gauge rivers like the Waikato, which had peaks of over 1000 m3/s and a width of 300 metres in 2004, more accurately than with a current meter. Much less time is required, and we can cope with variations in flow much better. This opens up the possibilities of measuring tidal flows in estuaries, and in other situations that would previously have been difficult or impossible, such as flood flows with river debris as recently occurred in the Bay of Plenty.
Although it is used mainly on larger rivers, advances in the technology are enabling smaller versions to be used in streams.