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Abstract:The acquisition of reliable discharge estimates is crucial in hydrological studies. This study demonstrates a promising acoustic method for measuring streamflow at high sampling rate for a long period using the fluvial acoustic tomography system (FATS). The FATS recently emerged as an innovative technique for continuous measurements of streamflow. In contrast to the traditional point/transect measurements of discharge, the FATS enables the depth-averaged and range-averaged flow velocity along the ray path to be measured in a fraction of a second. The field test was conducted in a shallow gravel-bed river (0.9 m deep under lowflow conditions, 115 m wide) for 1 month. The parameters (stream direction and bottom elevation) required for calculating the streamflow were deduced by a nonlinear regression to the discharge data from the well-established rating curve. The crosssectional average velocities were automatically calculated from the acoustic data, which were collected on both riverbanks every 30 s. The FATS was connected to the internet so that the real-time flow data could be obtained. The FATS captured discharge variations at a cut-off frequency of approximately 70 day À1 . The stream exhibited temporal discharge changes at multiple time scales ranging from a few tens of minutes to days.

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