Reliable, low-NOx-emission operation of a gas turbine plant with hydrogen-rich fuel gas, and a gas turbine plant with a device for water injection into hydrogen-rich fuels in a gas turbine, involves suitable water injection (21), a water-fuel gas mist, i.e., a fuel gas in which fine water droplets are suspended, is created in the fuel gas feed line (15). This mist is introduced into the burners (20) of the gas turbine. As a result of the water-fuel gas mist, four effects are combined for ignition delay and reduction of the flame velocity of hydrogen-rich fuel gas. When using a water-fuel gas mist, the water, in a directed manner, reaches the region in the burner (20) in which it directly has the greatest possible effect upon the flame or the flame velocity.