A rotatable apparatus for a water monitor. A flange assembly has a stationary portion, a rotatable portion disposed in the stationary portion, and a duct extending through the stationary and rotatable portions. A water-driven turbine has a rotatable water wheel in communication with the duct and an output shaft coupled to the water wheel. Fluid flowing through the duct causes the water wheel to rotate, the rotation of the water wheel causing the output shaft to rotate. An output crank, a first linkage, a rocker arm, and a second linkage comprising a first linkage member and a second linkage member are operable by the output shaft to convert the rotating motion of the output shaft to an oscillatory motion. Fluid exiting the duct is distributed by the rotatable portion in a determinable oscillatory pattern.