Water resources data for the 2005 water year for Long Island New York consist of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; stage and water quality of estuaries; and water levels and water quality of ground-water wells. This volume contains records for water discharge at 15 gaging stations; lake stage at 7 gaging stations; tide stage at 6 gaging stations; and water levels at 478 observation wells. Also included are data for 10 low-flow partial record stations. Additional water data were collected at various sites not involved in the systematic data-collection program, and are published as miscellaneous measurements and analyses. These data, together with the data in volumes 1 and 3 represent that part of the National Water Data System operated by the U.S. Geological Survey in cooperation with State, Federal, and other agencies in New York.