Answer
The water narrows as it falls.
Work Step by Step
The continuity equation for an incompressible fluid such as water, equation 12.10, states that the product of flow speed and cross-sectional area remains constant: $v_1A_1=v_2A_2$.
As the water falls, it speeds up, so the cross-sectional area of the stream decreases, i.e., the stream narrows.
