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The objective of this contribution is to assess the applicability of an Acoustic Doppler Current Profilers (ADCP) system for open-channel velocity measurements through validation against Stereoscopic Particle Image Velocimetry (Stereo-PIV) data. Stereo-PIV provides high spatial resolution and detailed insight into flow structures in laboratory open-channel hydraulics, delivering three-dimensional velocity components. ADCPs are widely used for velocity and discharge measurements, offering robust data collection even in sediment-laden and optically challenging environments. Their performance depends on acoustic frequency, flow conditions, and the size and concentration of suspended particles. To evaluate both systems under identical conditions, we conducted simultaneous Stereo-PIV and ADCP measurements in a laboratory flume, with emphasis on acoustically challenging regions.In this contribution, we present results from measurements conducted in a 16 m open-channel flume with a rectangular cross-section at the Laboratory for Hydraulic Engineering and Hydromechanics at Bochum University of Applied Sciences. The experiments covered Reynolds numbers between Re = 4.6 × 10⁴ and 1.6 × 10⁵ and Froude numbers between Fr = 0.04 and 0.1. The stereoscopic PIV setup consists of two CMOS double-frame cameras with macro lenses and Scheimpflug adapters. Polyamide (PA12) particles with a mean size of 20 µm were used as tracers and were illuminated by a Nd:YAG double-pulse laser. Stereo-PIV measurements were performed in a cross-sectional plane oriented orthogonal to the side walls. Measurements at multiple streamwise positions were obtained by translating the plane in several equidistant increments, enabling the assessment of spatial variations along a defined channel segment. For the ADCP measurements a Sontek RS5 profiler was used under clear-water conditions to capture velocity profiles in the fully developed flow region. The analysis accounts for near-boundary limitations by focusing on ADCP blanking zones and their impact on mean velocities and turbulence proxies.Results show a high accuracy of the Stereo-PIV and ADCP measurement in the core region of the channel flow with slight deviations in the measurement results and to theory. Closer to the boundaries the ADCP results deviate stronger from the Stereo-PIV results, indicating the need to optimize the ADCP evaluation methods for near-boundary applications.