Articles | Volume 16, issue 2
Hydrol. Earth Syst. Sci., 16, 345–356, 2012
https://doi.org/10.5194/hess-16-345-2012
Hydrol. Earth Syst. Sci., 16, 345–356, 2012
https://doi.org/10.5194/hess-16-345-2012

Technical note 06 Feb 2012

Technical note | 06 Feb 2012

Technical Note: How image processing facilitates the rising bubble technique for discharge measurement

K. P. Hilgersom and W. M. J. Luxemburg K. P. Hilgersom and W. M. J. Luxemburg
  • Water Resources Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands

Abstract. In this article, we rehabilitate the integrating rising bubble technique as an effective means of obtaining discharge measurements. Since Sargent (1981, 1982a), the technique has not been applied widely, mainly as a result of practical difficulties. We hypothesize that modern image processing techniques can greatly improve the rising bubble technique. We applied the technique in both a laboratory setup and a field study, after determining the bubble rising velocity for our nozzles in the specific case. During our measurements, we captured digital photographs of the bubble envelope at the water surface, each picture being a single measurement of the discharge. The photographs were corrected for lens distortion and reprojected so that accurate distances on water surface level could be obtained. This easy digital procedure resulted in accurate discharge measurements, even when turbulence was involved and the averages of multiple image analyses yielded good results. The study shows that the rising bubble technique can be a preferable discharge gauging technique in some situations. Recent developments in image processing facilitate the method substantially.

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