4.2 Hydrological response
The comparison between the hydrological (streamflow, water temperature
and electrical conductivity of the stream water, Figure 4) and the snow
and meteorological conditions (Figures 2 and 3, and the Supplementary
Figures 1 to 4 for an easier comparison) reveal that the spring
streamflow was determined by a mixed influence of snowmelt and
precipitation (mostly as rain) events. In 2017 and 2019 a double
streamflow peak was observed, caused by 2 melting periods in April and
May, interrupted by a period of low flows due to low temperatures and
snowfall events. The highest spring streamflow peak recorded during the
whole studied period occurred in 2017, triggered by the fast melting of
a shallow snowpack related to a heavy rain on snow event (Figures 2 and
3). The streamflow in 2020 also showed two small peaks, in response to a
mix of melt and frequent precipitation events in late April and mid-May,
interrupted by a period of low temperatures. The three years analyzed
show that the streamflow evolution in late May and June was mostly
determined by the persistence and the melting of snow cover in the
catchment during these months. Thus, the streamflow in 2019 remained in
late May and June higher than in 2017 and 2020, due to the longer
persistence of the snow cover in 2019. In 2017 and 2020, runoff already
decreased markedly by the end of May. However, the streamflow in 2017
continued decreasing along June due to limited rain events, whereas in
June 2020 the streamflow increased again and showed a fluctuating
behavior in accordance to the frequent rain events. The three years
analysis suggest that the streamflow is controlled by rain events after
mid-June, independently of the snowpack accumulation and its duration in
spring.