Water resources data for Montana for the 2005 water year, volumes 1 and 2, consist of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels in wells. This volume contains discharge records for 120 streamflow-gaging stations; stage or content records for 22 lakes and reservoirs; water-quality records for 86 streamflow stations (32 ungaged), and 25 ground-water wells; water-level records for 25 observation wells; and precipitation records for 2 atmospheric-deposition stations. Additional water year 2005 data collected at crest-stage gage and miscellaneous-measurement sites were collected but are not published in this report. These data are stored within the District office files in Helena and are available on request. These data represent part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Montana.