Water-resources data for the 1986 water year for Ohio consist of records of stage, discharge, and water quality of streams; stage and contents of lakes and reservoirs; and water levels and water quality of ground-water wells. This report, in two volumes, contains records for water discharge at 125 gaging stations, stage and contents at 4 lakes and reservoirs; water quality at 17 gaging stations, 100 wells, and 60 partial-record sites; and water levels at 948 observation wells. Also included are data from 59 crest-stage partial-record stations and 19 miscellaneous sites. 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 represent that part of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Ohio.