tidal river vs tidewater river

tidal river and tidewater river both are nouns.

Word	Noun	Adjective	Verb	Adverb
tidal river	Yes	No	No	No
tidewater river	Yes	No	No	No

As nouns, tidal river and tidewater river are synonyms defined as:

tidal river and tidewater river: a stream in which the effects of the tide extend far upstream

Other synonyms of tidal river include tidal stream, tidewater stream.

tidal river (noun)	tidewater river (noun)
a stream in which the effects of the tide extend far upstream	a stream in which the effects of the tide extend far upstream