Method for operating a gas turbine

The method involves partially reforming the fuel gas (B) supplied to a gas turbine (2) before addition of water vapor to the gas turbine, where the reforming takes place in a tubular reactor (60). The tube reactor is heated by the exhaust gases of the gas turbine, where the fuel gas is passed into a heat exchanger (62) before being fed into the gas turbine and after reforming. The addition of water vapor is performed by a jet pump, where the water vapor is taken to a heat recovery steam generator (14) associated with the gas turbine.