CONCLUSIONS
The combined study of meteorological, snowpack characteristics,
piezometric levels, streamflow and streamwater isotopic values and other
physical properties have permitted to deepen the understanding of the
hydrological cycle of the Izas catchment during the melting period in
years of contrasted snow duration and thickness. During spring, the
hydrological timing and magnitude is mainly controlled by snow melting.
Liquid precipitation during the melting period, however, strongly shapes
the hydrographs and contributes to the highest spring peak flows. Once
snow disappears from the ground, the piezometric levels quickly decline,
and the streamflow values rapidly decrease. The increase of streamwater
temperature, electrical conductivity and δ18O isotopic
values in combination with the strong diel variability of the
δ18O isotopic values during the snow cover period,
which is linked to daily cycle of dominant snowmelt or baseflow in
runoff generation, suggest a short transit time of the water in the
catchment during snowmelt, and therefore a limited role of groundwater
supply to the streamflow. Thus, the interannual variability of the
snowpack has a limited role in the summer runoff evolution. Hence, snow
rich years might not increase the catchment resilience to summer
droughts. Streamwater isotopy has responded clearly to snow cover
evolution over the catchment However, its strong interannual variability
represents challenges to properly make a hydrograph separation and to
infer quantitatively the contribution of snowmelt to total runoff.
ACKNOWLEDGEMENTS. This study was funded by the project
HIDROIBERNIEVE (CGL2017-82216K), MARGISNOW (PID2021-124220OB-100) and
SNOWDUST (TED-2021-130114B-I00), both funded by the Spanish Ministry of
Science and Innovation. E. Izagirre was supported by the Consolidated
Research Group IT1029-16 (Basque Country Government).