Abstract: A hydroelectric turbine installation includes a turbine, a water passage located upstream, a draft tube, a controller that controls operation conditions, a device for introducing oxygen-containing gas into water passing through the installation, a device for injecting water into the draft tube, and a device for controlling a flowrate of the water injected into the draft tube. The device for controlling the flowrate includes a control unit and a valve. The control-unit is configured to control the flowrate of the water injected into the draft tube in a way that the flowrate is a function of the operation conditions of the turbine. The flowrate set by the control unit at an operation condition of the turbine corresponding to an optimal efficiency point of the turbine is higher than a flowrate set by the control-unit at one or more other operation conditions of the turbine that do not correspond to an optimal efficiency point.