Blood (symbolic meaning in prophecy)

War, carnage, slaughter.  To “turn water into blood” is to embroil nations in war.  See Isa. 9:5, 15:9, 34:3, 34:6, 34:7, 49:26.  See Ezek. 9:9, 14:19, “…pour out my fury on it in blood, and cut off from it man and beast”; Joel. 2:30-31; Rev. 14:20.