A combined water-wash and wet compression system for a gas turbine includes a compressor (44) having an inlet (40) defining a flow direction; and a plurality of manifolds (38, 40, 42, 52, 54, 56) arranged in proximity to the inlet and arranged transversely of the flow direction; a plurality of dual function nozzles (46, 48, 50) connected to the manifolds. each dual function nozzle is adapted to supply, selectively, either relatively small droplets for introduction into the compressor for intercooling, or relatively large droplets for impingement on components of the compressor for cleaning the components. a method of introducing a liquid into a compressor inlet for providing water wash for cleaning components of the compressor, and for providing wet compression for intercooling is also disclosed.