In the paper results of numerical modelling of water flow conditions in fishladers close to nature which are bypass channels designed as a natural stream and with habitat elements were presented. The simulations results were compared with laboratory measurements of vertical distributions of velocity at different habitats which occur in natural streams: from pool to fast run and riffle. There were measured three components of velocity v_x, v_y i v_z at characteristic points of longitudinal profile and cross-section: (1) at rapids, (2) inside and (3) outside turbulence zone for different bed configurations and size of bed material. The measured values were used to calculate velocity profiles, average velocities and characteristics of local flow conditions. This is an attempt to calculate a water flow parameters in nature base on laboratory measurements using similitude concept.

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