Volumes 1 and 2 of the water resources data for the 2004 water year for Oklahoma consists of record of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes or reservoirs; and water levels of ground-water wells. This report contains discharge records for 138 gaging stations; stage and contents for 18 lakes or reservoirs and 2 gage height stations; water quality for 55 gaging stations; 38 partial-record or miscellaneous streamflow stations and 4 ground-water sites. Also included are lists of discontinued surface-water discharge and water-quality sites. 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 Oklahoma.