Me. Rev. Stat. tit. 22, § 2641

As used in this subchapter, unless the context otherwise indicates, "public water source" means any natural or human-made impoundment, pond or lake or ground water aquifer whose waters are transported or delivered by a public water system, as defined in section 2601, subsection 8. Where the intake of a public water supply is on the outlet of any impoundment, pond or lake, the source of the public water supply is considered to be the impoundment, pond or lake itself.