Water stable isotope ratios (2H and 18O) from the Willamette River Basin in Oregon, USA. Isotope values in the Willamette River are from both Portland and Corvallis Oregon, and were collected once or twice a month for 13 years (2011 - 2013). Isotope data are provided for small spatially distributed watersheds across the basin and samples were collected once a year during summer lowflow, and used to test the temporal stability of the Willamette River Basin Isoscape developed in the following paper: Brooks, J. R., Wigington, P. J., Phillips, D. L., Comeleo, R., & Coulombe, R. (2012). Willamette River Basin surface water isoscape (d18O and d2H): temporal changes of source water within the river. Ecosphere, 3(5), 39. doi: http://dx.doi.org/10.1890/ES11-00338.1 In addition, precipitation isotopes from Corvallis and Newport were collected weekly.