A gas turbine unit as well as a method for operating a gas turbine with high-pressure turbine and a low-pressure turbine unit are disclosed. A very quick and at the same time easily controllable augmentation or reduction of the shaft power of the gas turbine unit can be achieved by providing at least one liquid droplet injection device on the upstream side of said compressor for injecting liquid into the stream of intake air in order to increase the shaft power generated by the gas turbine unit. The amount of water mass flow corresponding to the desired increase or decrease of shaft power output of the gas turbine unit is added or reduced in the form of liquid droplets in a substantially stepless manner and immediately within a time interval that is determined by the design characteristics of the liquid droplet injection device.