N.Y.C. Admin. Code § 24-306: § 24-306 Trespass on water supply property.

It shall be unlawful to enter or remain on any part of the embankment of a water supply reservoir within the city without the permission of the commissioner of environmental protection, or to fail or refuse to comply with the rules and regulations of the commissioner as to when citizens shall leave such embankment, or the grounds or buildings attached thereto.