A turbine and method of operating a turbine includes a housing having an inlet, a volute and an outlet. The inlet is coupled to the volute through a primary fluid path and a secondary fluid path. The turbine further includes an impeller rotatably coupled to the housing and a hydraulically actuated valve assembly disposed within the secondary fluid path selectively communicating fluid from the inlet to the volute. The turbine includes a hydraulic actuator coupled to the valve assembly moving the valve assembly from a first position communicating fluid from the inlet into the volute to a second position blocking flow from the inlet to the volute.