A large and highly twisted and tapered turbine rotor blade with a low flow cooling circuit that includes a first serpentine flow circuit in a forward section of the lower span of the blade, a second serpentine cooling circuit in the aft region of the lower span, a third serpentine cooling circuit in the forward region of the upper span, and a fourth serpentine cooling circuit in the aft region of the upper span to provide cooling for the entire blade. Cooling air from the first serpentine flows into the third serpentine cooling circuit and cooling air from the second serpentine flows into the fourth serpentine cooling circuit so that the lower span of the blade is cooled first using fresh and relatively cooler cooling air.