If your copper water pipe is less than 10 feet, then it does not qualify as a grounding electrode, and does not need to be bonded. Regardless, supplemental ground rods need to be installed. I understand the origional reason for requiring supplemental ground rods when the only GE on the job is a metal water pipe is this scenario you have just described. One cannot rely upon the metal water pipe to be in contact with the earth for 10 feet, nor can it be relied on to stay metal.
