water levelwas only 40 cm deep. On the evening of August 23, 2011,
a rainstorm of approximately 20e30 mm occurred before this
profilewas sampled the next morning. After several rainfalls (about
30e50 mm) in one week, the moisture content of the upper
0e20 cm approached 10%, and at a depth of 20e40 cm it increased
from 10% to 25% and finally became saturated (Fig. 8a) close to the
groundwater. Three rainwater samples and two well water samples
near this profile were collected at the same time. The depths of the
two wells were 0.8 m and 1.5 m, respectively. The H and O stable
isotopes of the rainwater, well water and unsaturated zone water
samples were analyzed. The isotope curves (Fig. 8a) illustrated that
the d2H and d18O of the water in the sand layer below 20 cm were
lower than was the rainwater and that the two types of water
mixed in the layer 20e40 cm in depth. The d2H and d18O of the