Fig. 8. Stable isotope profiles at the beginning of the dry season for pulsed infiltration models. The time-dependent input rates of winter infiltration of 16.7, 58.3, and 150 mm yr^–1 result in calculated (Eq. [19]) steady-state net infiltration rates of 14.3, 55.0, and 147 mm yr^–1, respectively. Water input (input water ¹⁸O of –16.5) occurs such that annually all of the infiltration comes during the first 0.3-yr wet period and is followed by a 0.7-yr dry period. The soil type is silty sand, and atmospheric conditions (h = 40% and ¹⁸O_a = –21) are the same as those for Fig. 3, 5, and 7. Model results are compared with data collected as part of an ongoing study of the VZFS300N lysimeter in March 2003, shortly after the wet season (diamonds). The lysimeter has a measured drainage rate of 55 ± 10 mm yr^–1 (Sisson et al., 2002).