Abstract
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.
Highlights
A large variety of discharge gauging techniques is applied in the field of hydrological measurements
To address the potential of the rising bubble technique as a modern and usable method, we introduce the application of image processing techniques
From our laboratory measurements of the rising velocity, we concluded that a nozzle opening of 1 mm in diameter together with an air pressure just above the water pressure around the nozzle produced air bubbles that are most likely within the range of 2 to 4 mm
Summary
A large variety of discharge gauging techniques is applied in the field of hydrological measurements. The integrating float method, one of these techniques, best resembles the frequently applied method using a float at the water surface. With the latter method, hydrologists measure stream flow by releasing a float at the water surface and calculating the velocity from its displacement over time. Hydrologists measure stream flow by releasing a float at the water surface and calculating the velocity from its displacement over time This method is easy and quick but is considered relatively inaccurate, for an uncertain correction factor is applied to estimate the depthaveraged velocity from the measured surface velocity. This article discusses the merit of modern computational and photogrammetric techniques for applying the integrating float method and the rising bubble technique to measure river discharge (Sargent, 1981; Shaw, 1994)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
