Abstract: A control system for synchronous condensing operation of a hydroelectric turbine-generator wherein the draft tube water level for the turbine is controlled through the use of that generator's power or current consumption. Either parameter may be used in the process. Water impacting the turbine will increase both of these parameters above an optimum minimum value. Either a generator power or current device provides a signal to a control circuit. When the signal from either device exceeds a preset value, the control circuit injects compressed air into the turbine cavity until the signal returns to its optimum value.