(1) The numbering or index system used to identify specific waters of New York State was adapted from that used by the New York State Conservation Department in its biological survey series of reports on watersheds of the State. The primary waters of a drainage area, such as a river, large lake, bay or sound, is usually referred to by name or an abbreviation. Tributaries of primary river waters are consecutively numbered progressing upstream from the mouth. Tributaries of primary lake, bay or sound waters are consecutively numbered in a clockwise order from a defined point, usually the outlet of the primary waters. Subtributaries are numbered as encountered along the tributary proceeding from its mouth to the source, and in like manner all of its other stream courses are so numbered. Ponds and lakes are numbered in the order they are encountered within the system. Tributaries of such lakes and ponds are numbered consecutively as they enter, progressing clockwise around the lake or pond from its outlet or mouth. The numbers assigned to such lakes and ponds are prefixed by the letter P. When isolated lakes and ponds are referenced by a waters index number, it is merely for convenience of their identification and location within a subdrainage basin, and it is not necessarily indicative of their being tributary to any waters to which no surface connection is shown on the reference maps.

(2) This system was applied to the basin under consideration by the Conservation Department in its report, A Biological Survey of the Fresh Waters of Long Island—1938, and has been closely followed in connection with the identification of the waters with the following exceptions: Some of the stream numbers do not run consecutively due to the omission of streams originally shown on the older maps employed by the Conservation Department at the time of its survey but not shown on newer maps reproduced herein. Conversely, a few streams not shown on the older maps but appearing on the newer maps are designated by the letters a, b, c, etc.

(3) There are several primary indices used to identify the designated waters. Those waters that drain Long Island proper are identified by waters index numbers prefixed by the abbreviation LIS. Those waters that drain Shelter Island Sound proper are identified by waters index numbers prefixed by the abbreviation SIS. Those waters draining Gardiners Island and Fishers Island are identified by waters index numbers prefixed with either “Gardiners Island” or “Fishers Island”, as the case may be.

(4) The system as applied to the identification of waters in the drainage basin of Eastern Suffolk County may be illustrated as follows: