Turbine blade airfoils, showerhead film cooling systems thereof, and methods for cooling the turbine blade airfoils using the same are provided. The airfoil has a leading edge and a trailing edge, a pressure sidewall and a suction sidewall both extending between the leading and the trailing edges, and an internal cavity for supplying cooling air. A showerhead of film cooling holes is connected to the internal cavity. Each film cooling hole has an inlet connected to the internal cavity and an outlet opening onto an external wall surface at the leading edge of the airfoil. A plurality of surface connectors is formed in the external wall surface. Each surface connector of the plurality of surface connectors interconnects the outlets of at least one selected pair of the film cooling holes.