FIGURE 6. Precipitation δ18O (average of the
12 antecedent days; triangles) and streamflow δ18O
(average of the morning and evening samples) measured at the Izas
gauging station (lines).
During the period April-June, the streamflow δ18O
values were noticeably more depleted (ranging from -8 to -12 ‰) than the
precipitation (mostly in liquid phase) δ18O values
(ranging from -4 to -10 ‰, with most of the values ranging between -6
and -8‰). In general, the evolution of the streamflow isotopy was
relatively steady, with slight day-to-day changes. The three years
analyzed showed some interannual differences in streamflow
δ18O values, likely driven by the snowpack magnitude
and duration. The lowest streamflow δ18O values were
observed in 2018 (a snow rich year). On the contrary, higher values were
found in 2019 and 2020 (low and very low snowpack years, respectively).
The differences in streamflow δ18O values remained
even weeks after snow cover was completely depleted from the catchment.