Abstract: A turbine, particularly for a sprinkler system, comprises a rotor mounted on a shaft so as to be rotatable about a rotor axis and having a plurality of curved vanes attached to the wheel rim, a variable nozzle and a control device for control of the flow of water through the turbine. The control device is mounted in a ring shaped space, is a part of the nozzle and a part of the wall of the ring shaped space and the control device controls the size of both an annular clearance between the turbine wheel and the control device and the cross section of the nozzle so that the cross section of the nozzle and the annular clearance are correlated with each other. Advantageously the control device may be a broad surface curved plate mounted on a pivot shaft so as to be pivotable partly between two parallel walls of a fixed part of the nozzle formed by the turbine housing and shaped to follow the radius of curvature of the outer periphery of the rotor.