A turbine blade for use in a gas turbine engine that requires internal cooling for the blade. The blade includes a leading edge cooling supply cavity and a trailing edge cooling supply cavity to supply pressurized cooling air from an external source to the internal cooling circuit of the blade. The leading edge cooling supply cavity is connected to a leading edge impingement cavity through metering and impingement holes to provide metering and impingement cooling air to the leading edge region of the blade and to the showerhead film cooling holes. Both the leading edge and the trailing edge cooling supply cavities also supply cooling air through metering and impingement holes to respective pressure side and suction side impingement cavities located between the two supply cavities for impingement cooling. Each impingement cavity is connected to the blade external surface through a row of film cooling holes to discharge the spent impingement cooling air.