PURPOSE: To prevent the generation of a swirl current, vibration, noise, damage, etc., by projecting a drift preventing projection having a clash face on the outside in the direction of the width around a boundary curve section between a diagonal section and an introducing section with respect to a river to the inside in the direction of the width.

CONSTITUTION: Flowing water W of a river 1 is taken from an inlet 5 to change the flow as indicated by arrow A, and it is drifted toward the outside in the direction of of the width of a diagonal section 2. After that, the drift clashes with a clash face 9A of a drift preventing projection 9 around a boundary curve section 6 between the diagonal section 2 and an introducing section 3, as indicated by arrow B. Then, the clashed drift is directed toward the the downstream side of the river along the vertical axis CL of the introducing section 3 by the clash face 9A, as indicated by arrow C, and it is converted into the straight stream having uniform distribution of flow. Successively, it flows in water absorbing tanks 4, and the generation of an air suction whirls around pumps D and P is controlled. According to the constitution, the generation of vibration and noises is prevented, and a pump operation functional obstacle and damage in the foundation and a building can be prevented.