Jamieson, Fausset and Brown on Jeremiah 48:34

34. From the cry of Heshbon, &c.--Those who fly from Heshbon on its capture shall continue the cry even as far as Elealeh ... . There will be continued cries in all quarters, from one end to the other, everywhere slaughter and wasting.

as an heifer of three years old--Moab heretofore not having known foreign yoke, and in its full strength, is compared to an heifer of three years old, never yet yoked, nor as yet worn out with many birth-givings (compare Note, see on Is 15:5).

waters ... of Nimrim--that is, the well-watered and therefore luxuriant pastures of Nimrim.

desolate--The Hebrew is stronger: not merely shall be "desolate," but desolation itself multiplied: plural, "desolations." The most fertile tracts shall be dried up.