This data release provides a set of Hydrological Simulation Program--Fortran (HSPF) model files representing 5 EPA-selected future climate change scenarios for the Upper Charles River Basin in Massachusetts. Output from these models are intended for use as input to EPA Watershed Management Optimization Support Tool (WMOST) modeling. Climate scenarios, based on 2036-2065 changes from 1975-2004 for Representative Concentration Pathways (RCP) 4.5 and 8.5, model the effects of air temperature and precipitation changes (in degrees F for air temperature, in percent for precipitation) made to the input historical meteorological time series for 1975-2004. Meteorological data are from Boston Airport (Boston, MA), T.F. Green Airport (Providence, RI), and Worcester Regional Airport (Worcester, MA). Each set of climate scenario model files are derived from the original calibrated model files created by the Charles River Watershed Association to develop Total Maximum Daily Loads (TMDLs) for nutrients, and modified by USGS to support WMOST modeling (refer to Source Input fields in this metadata file).