Fig. 2. Soil water ¹⁸O values with depth in the Hanford vadose zone. Pore waters in the upper 2 m are most strongly affected by evaporation (Fig. 2) and have ¹⁸O values up to –3.8. Below the evaporation zone, soil water ¹⁸O values are shifted by approximately +2 (dashed line) higher than typical winter precipitation (–16.5). Pore water stable isotope data from DePaolo et al. (2004) and unpublished data from ongoing studies are shown as blue diamonds.