The confluence area of rivers

as a key component of river systems

features complicated hydrodynamics and three-dimensional changes in bed morphology. This study conducts a laboratory water tank experiment of a river confluence and examines the distribution characteristics of its water flow under the condition of low sediment concentration. Four concentration conditions are tested

flow velocity is measured using an Acoustic Doppler Velocimeter (ADV)

and the data is denoised. Results show that with an increasing concentration

velocity zoning characteristics in the confluence vary significantly

and the ranges of the flow velocity gradient and the maximum-velocity-covered area are both expanded. This means the dynamic behaviors of fluid and the interactions between fluid layers are enhanced. We also found that in the concentration range of 4.2 to 7.4 kg/m3

the inhibitory effect of sediment on turbulence is insignificant. The results lay an important basis for a deeper understanding of the hydrodynamic process and sediment transport in a river confluence.