In Bible times “rivers and fountains of waters” were primarily useful for such everyday requirements as drinking, bathing, and irrigation. Whereas the second plague would doubtless result in great inconvenience and perhaps interruption of travel (see on v. 3) the effects of the third would be immediate and serious. Compare the first plague on the land of Egypt (see on Ex. 7:17, 19). Like the first and second plagues, the third is not universal (see GC 628).