Water resources data for the 2004 water year for Pennsylvania consist of records of discharge and water quality of streams; contents and elevations of lakes and reservoirs; and water levels and water quality of ground-water wells. This report, Volume 3 contains (1) discharge records for 60 continuous-record streamflow-gaging stations, 6 partial-record stations and 13 special study and miscellaneous streamflow sites; (2) elevation and contents records for 11 lakes and reservoirs; (3) water-quality records for 4 lakes and reservoirs; (4) water-quality records for 23 gaging stations and 26 ungaged streamsites; (5) water-level records for 23 ground-water network observation wells; (6) ground-water-quality records for 19 miscellaneous wells. Site locations are shown in figures throughout the report. Additional water data collected at various sites not involved in the systematic data-collection program are also presented. These data together with the data in Volumes 1 and 2, represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State, local, and Federal agencies in Pennsylvania.