NOVELTY - Operation of fuel cell power plant, comprises transporting reactant streams through low pressure side, and by transporting reformate supply stream through high pressure side; and transporting the reactor oxidant stream, the reformate supply stream, and the cathode oxidant supply stream though the low pressure side, and by transporting one or both of the effluent streams through the high pressure side.    USE - For operating a fuel cell power plant used in the production of electricity from the electrochemical reaction of hydrogen and an oxidant.    ADVANTAGE - The method has the ability to maintain true water balance over a wide range of operating conditions, improved reliability, and decreased system energy requirements, and potential safety.    DETAILED DESCRIPTION - Operation of fuel cell power plant comprising reactor for production of reformate supply stream using reactant stream comprising reactor oxidant stream and reactor hydrocarbon fuel stream, where the reformate supply stream comprises water; and a fuel cell comprising an anode input for reformate supply stream, cathode input for cathode oxidant supply stream, anode output for anode effluent stream, cathode output for cathode effluent stream, where either or both of anode effluent and cathode effluent comprise water produced by fuel cell. The method comprises:    (1) transferring water from reformate supply stream to one or both of reactant streams in first water transfer device that has high pressure side and low pressure side, by transporting the reactant streams through low pressure side, and by transporting reformate supply stream through high pressure side; and    (2) transferring water from one or more of reaction oxidant stream, the reformate supply stream, and the cathode oxidant supply stream in a second water transfer device that has a high pressure side and a low pressure side, by transporting the reactor oxidant stream, the reformate supply stream, and the cathode oxidant supply stream though the low pressure side, and by transporting one or both of the effluent streams through the high pressure side.    DESCRIPTION OF DRAWING(S) - The figure is a diagram comprising reactor, water transfer device for transferring water vapor from reformate output of reactor to air input of reactor, fuel cell, and water transfer device.