In an apparatus for measuring a parameter of a wet gas flow, a gamma densitometer is provided and configured to non-intrusively measure the density of the wet gas flow. A sonar based flow meter is also provided and configured to non-intrusively determine a flow rate of the gas flow of the wet gas flow. A processing device is in communication with at least one of the gamma densitometer and the sonar based flow meter, the processing device being configured to determine the flow rate of the gas portion and/or liquid portion of the wet gas flow using the measured density and flow rate of the wet gas flow.