Smith's Bible Dictionary (1863)
(limpid, pure), The waters of, a stream or brook within the country of Moab, which is mentioned in the denunciations of that nation by Isaiah. (Isaiah 15:6) and Jeremiah. e. on the southeastern shoulder of the Dead Sea.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
NIM'RIM (limpid, pure). " "The waters of Nimrim " was a stream or brook in the territory of Moab, referred to by Isaiah and Jeremiah. Isa 15:6; Jer 48:34; comp. Num 32:3, Eze 23:36. There are copious springs near Nimrah, and Porter, Conder, and Baedeker would locate the waters of Nimrim in its vicinity. Dr. Merrill regards it as the largest stream east of the Jordan and south of the Zerka, Wady N'mirah, at the southeast corner of the Dead Sea, has been claimed as the "waters of Nimrim," but the stream is small and the name has a different signification.
Perhaps the "brook of the willows," Isa 15:7, may be in that region.