Fast and Minimally Intrusive Method for Measuring Tidal-Stream Discharge

Abstract

The measurement and computation of discharge measurement in tidal streams using a fast and minimally intrusive method is developed. The discharge of tidal streams is highly unsteady because of influences from ocean tides and upstream river flow. Measurement of the discharge at a stream with such complex currents is limited by the efficiency and cost of conventional measurement instruments and methods. Thus, it is necessary to introduce new measurement approaches and instruments for measuring the discharge of tidal streams. This study installs high-precision Argonaut-SW under a sounding weight to be hung from a vertical line using a single-drum winch. The Argonaut-SW is modified to be a mobile device to measure the velocity distribution and water depth from the surface. This study also uses the observed data to establish an efficient discharge measurement method suitable for tidal streams, which utilizes the relationship between mean and maximum velocities for rapidly estimating discharge in the future. This method is applied on the tidal reach of the Keelung River. The results show that the discharge measurement method established by this study can not only greatly improve the accuracy of discharge measurement but also significantly reduce the time, labor, and cost required for measuring discharge in tidal streams.