Hydrologic and climatologic data are being collected in a 19-square-mile (49-square-kilometer) basin in southeastern Montana to provide a base for development, calibration, and verification of a precipitation-runoff model. The study area and data-collection stations within the area are shown on a map. A summary of data collected at each station during the first year, beginning in October 1978, is provided in tables. The data include precipitation, snow depth and water content, air temperature, relative humidity, wind run, solar radiation, soil temperature and moisture, stream discharge, chemical analyses of water, and sediment content.