Abstract

Gauging rivers has always presented the hydrographer with a variety of challenges, but at the end of the day high quality measurements taken over a wide range of stage heights has always been the goal. The relatively recent introduction of ADCP devices to determine discharge has, in general, improved measurement accuracy and reduced the time required to make these measurements, however the fundamentals of “taking a good gauging” haven’t changed.

DPIPWE set about designing deployment systems to improve ADCP boat control. Improving boat control has a number of major benefits. A repeatable track greatly improves the reproducibility of results, and reduces the extent of data post-processing as the positioning and orientation of the instrument is more accurately controlled. For stationary boat measurements, improved boat control also allows for rapid and accurate re-positioning of the instrument, greatly reducing the time required to make each measurement. Our aim has been to position the instrument on a straight transect and to reduce the transverse and rotational movement of the boat. The other issue we have tried to address is providing the instrument with a stable vessel that is “sea worthy” at velocities greater than 2.0 ms^-1 and in waters with large standing waves. While our proprietary vessels provided a satisfactory instrument platform in relatively flat water conditions, in faster and more turbulent conditions these vessels were less competent due to their design characteristics.