Artificial islands and viewing pavilions can act as barriers in slow-flow water bodies such as lakes and can be used together with water diversion projects to improve the water quality. In this study, based on the particle image velocimetry system, we carried out flume experiments to study the influence of the location and shape of barriers on the purification capacity of a slow-flow water body. We analyzed the velocity composition based on the information entropy H and the vector distributions, average velocity and water exchange rate η. The results reveal that the hydrodynamic characteristics are significantly optimized by barrier structures. η doubles if the barrier structure is reasonably designed, and it is positively correlated with the average velocity. In all cases, the highest η is recorded for a barrier shaped as a rectangular column and increases with the interaction area between the flow and structure. The water purification capacity and flow velocity gradually increase with increasing flow rate. The influence of the relative distance l between the inlet and the structure on η is non-monotonic. To achieve a higher η, the l for the rectangular column, triangular prism, and semi-cylinder should be 0.2–0.3, 0.2–0.3, and 0.3–0.55, respectively. The deflection angles and the ratio of lateral velocity to streamwise velocity of the deflection mainstream decrease with increasing l. H for the rectangular column is higher than that for other shapes. The results are of guiding significance for the layout of barrier structures and for the optimization of water landscapes in practical applications.

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