Water resources data for the 1986 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 2, includes records from the Susquehanna and Potomac River basins. Specifically, it contains: (1) Discharge records for 93 continuous record stream-flow-gaging stations and 12 crest-stage partial-record stations; (2) elevation and contents records for 13 lakes and reservoirs; (3) water-quality records for 22 streamflow-gaging stations, for 8 ungaged streamsites, and for 30 wells or springs; and (4) water-level records for 41 observation wells. Locations of these sites are shown on figures 7-10. Additional water data were collected at various sites not involved in the systematic data-collection program and are published as miscellaneous measurements and analyses and represent 3 special study and miscellaneous streamflow sites and 22 ground-water quality sites. 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 and cooperating State, local, and Federal agencies in Pennsylvania.