River discharge monitoring using a vertically moving side-looking acoustic Doppler profiler

This paper presents an innovative river discharge monitoring system which uses a horizontal acoustic Doppler current profiler (H-ADCP) attached to a mechatronic system that provides vertical motion to different depths. Also, an extended index velocity method is developed which utilises velocity measurements from different depths to achieve more accurate discharge calculation under complex flow conditions. The prototype system was developed and installed near the estuaries of a river where backwater and tidal motion was known to be present due to small distance and altitude difference from the sea. Five experiments were performed, and in two experiments the proposed method performed roughly the same as the standard index velocity method. In the other three experiments the proposed method performed much better and the difference between the discharges was as large as 10%. The results indicate that a vertically moving H-ADCP can be used to calculate river discharge more accurately in complex flow environments.