water birch vs Western birch

water birch and Western birch both are nouns.

Word	Noun	Adjective	Verb	Adverb
water birch	Yes	No	No	No
Western birch	Yes	No	No	No

As nouns, water birch and Western birch are synonyms defined as:

water birch and Western birch: birch of western United States resembling the paper birch but having brownish bark

Other synonyms of water birch include Betula fontinalis, mountain birch, swamp birch, Western paper birch.

water birch (noun)	Western birch (noun)
birch of western United States resembling the paper birch but having brownish bark	birch of western United States resembling the paper birch but having brownish bark