Volume 4 of the water resources data for the 1980 water year for California consists of records of stage, discharge, and water quality of streams; stage, contents, and water quality in lakes and reservoirs; and water levels in wells. This report contains discharge records for 199 gaging stations; stage and contents for 34 lakes and reservoirs; precipitation data for stations; water quality for stations; water levels for 54 observation wells, and water quality for 26 wells. Also included are 16 crest-stage partial-record stations, 7 low-flow partial-record stations. Additional water data were collected at various sites, not part of the systematic data collection program, and are published as special investigations. These data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in California.