ADCP, Multi-frequency analysis for flow measurements in rivers

Abstract

Aim of the study Recently, the use of acoustic Doppler current profilers (ADCP) gains in popularity. Considering the use of various equipment, a question arises whether there are any differences in measuring with ADCP that works at different frequencies. The aim of this study was to compare and evaluate three ADCPs operating at different frequencies: 2,000 kHz, 1,500 kHz, and 600 kHz under field conditions. Material and methods Following parameters were applied for a transverse section of 100 m in width and 7 m in depth: (1) components of velocity flow, (2) depth, (3) transverse distance among vectors, (4) total distance and (5) geographic position of each vector. Results and conclusions The results showed that velocity magnitudes were low in margin areas, while high in the center. In comparison with other devices the 2,000 kHz ADCP keeps a homogeneous velocity distribution up to 5.0 m in depth. Also, the statistical and graphic analysis demonstrated that flow measurements did not differ by more than 5%. Nevertheless, the review of velocities showed significant differences between ADCPs. High frequency means more detailed data, but less deep range, particularity in zones with upper sediments concentration. Low frequency means less detailed data, but deeper range. Furthermore, our findings suggest that measurements performed in rivers provide results, which sometimes are entirely different from results obtained in laboratory.

Keywords

• ADCP
• depth measurement
• river discharge
• hydrodynamic
• acoustic techniques