Why is god punishing the Hebrews?

Exodus 7:19 says, "And the LORD spake unto Moses, Say unto Aaron, Take thy rod, and stretch out thine hand upon the waters of Egypt, upon their streams, upon their rivers, and upon their ponds, and upon all their pools of water, that they may become blood; and that there may be blood throughout all the land of Egypt, both in vessels of wood, and in vessels of stone." Don't the Hebrew’s have to drink the water turned blood too. It seems god is punishing the Hebrews as well as the Egyptians?  You would think an omnipotent being would come up with a way of torturing the Egyptians without hurting his chosen people.