Jamieson, Fausset and Brown on Isaiah 19:6

6. they shall turn the rivers--rather, "the streams shall become putrid"; that is, the artificial streams made for irrigation shall become stagnant and offensive when the waters fail [Maurer]. Horsley, with the Septuagint, translates, "And waters from the sea shall be drunk"; by the failure of the river water they shall be reduced to sea water.

brooks of defence--rather, "canals of Egypt"; "canals," literally, "Niles," Nile canals, the plural of the Egyptian term for the great river. The same Hebrew word, Matzor, whence comes Mitzraim, expresses Egypt, and a place of "defense." Horsley, as English Version translates it, "embanked canals,"

reeds ... flags--the papyrus. "Reed and rush"; utter withering.