The objectives of a 3-year study of urban runoff in the Rapid City area of South Dakota were to characterize the effects of urban runoff from rainfall on the water quality of Rapid Creek, and to evaluate the effects of the runoff on the existing cold-water fishery. In order to meet these objectives, it was necessary to obtain detailed data pertaining to land use, rainfall, dryfall, stream discharge, and storm runoff. This report describes the rationale behind the data collection program, describes the methods used to collect and analyze the data, and presents the data collected and summarized during the study. Six watersheds were investigated, ranging in size from 1 ,610 to 20,990 acres. Water quality data from 6 sites for about 30 rainstorms that occurred between June 1980 and July 1982 are presented. (USGS)