Water resources data for the 1980 water year for Ohio consist of records of stage, discharge, and water quality of streams; stage and contents, and water quality of lakes and reservoirs; and water levels and water quality of groundwater wells. This report in two volumes and one appendix contains records for water discharge at 169 gaging stations; stage and contents at 39 lakes and reservoirs; water quality at 57 gaging stations and 83 wells; and water levels at 183 observation wells. Also included are data from 84 crest-stage partial-record stations; 91 low-flow partial-record stations, and 537 coal hydrology synoptic 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.