reservoir vs water supply

reservoir and water supply both are nouns.

Word	Noun	Adjective	Verb	Adverb
reservoir	Yes	No	No	No
water supply	Yes	No	No	No

reservoir (noun)	water supply (noun)
tank used for collecting and storing a liquid (as water or oil)	a facility that provides a source of water
lake used to store water for community use; a lake (natural or artificial) used to store water and used as a source of water
anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies
a large or extra supply of something