ground water vs well water

ground water and well water both are nouns.

Word	Noun	Adjective	Verb	Adverb
ground water	Yes	No	No	No
well water	Yes	No	No	No

As nouns, ground water and well water are synonyms defined as:

ground water and well water: underground water that is held in the soil and in pervious rocks

Other synonyms of ground water include spring water.

ground water (noun)	well water (noun)
underground water that is held in the soil and in pervious rocks	underground water that is held in the soil and in pervious rocks