N.Y.C. Admin. Code § 4-102: § 4-102 Loss of certain lands; by reversion.

The lands situate in the county of Westchester which were taken by the city, by virtue of the act entitled "An act to provide for supplying the city of New York with pure and wholesome water" passed May second, eighteen hundred thirty-four, shall be held and appropriated by the city for the use and purpose of introducing water into the city, and for purposes necessarily incident thereto, and for no other uses or purposes whatever. In case the city should use any of such lands situate in the county of Westchester for purposes other than in this section permitted, or in case such land should not be required for the purpose of introducing water into the city, such lands so improperly used, or not so required, shall become vested in the individual from whom such city obtained it, as full and perfectly as though such act had never been enacted, upon repaying to the city the amount originally paid for the same, after deducting from such amount the damages sustained by such individual by reason of any alteration or work which the city may have made upon such land.