Jamieson, Fausset and Brown on Isaiah 19:7

7. paper-reeds--rather, pastures, literally, "places naked" of wood, and famed for rich herbage, on the banks of the Nile [Gesenius]. Compare Ge 13:10; De 11:10. Horsley translates, "nakedness upon the river," descriptive of the appearance of a river when its bottom is bare and its banks stripped of verdure by long drought: so Vulgate.

the brooks--the river.

mouth--rather, "the source" [Vulgate]. "Even close to the river's side vegetation shall be so withered as to be scattered in the shape of powder by the wind" (English Version, "driven away") [Horsley].