Tracer-based analysis of spatial and temporal variations of water sources in a glacierized catchment

Abstract

Abstract. Snow-dominated and glacierized catchments are important sources of fresh water for biological communities and for populations living in mountain valleys. Gaining a better understanding of the runoff origin and of the hydrological interactions between meltwater, streamflow and groundwater is critical for natural risk assessment and mitigation as well as for effective water resource management in mountain regions. This study is based on the use of stable isotopes of water and electrical conductivity as tracers to identify the water sources for runoff and groundwater and their seasonal variability in a glacierized catchment in the Italian Alps. Samples were collected from rainfall, snow, snowmelt, ice melt, spring and stream water (from the main stream at different locations and from selected tributaries) in 2011, 2012 and 2013. The tracer-based mixing analysis revealed that, overall, snowmelt and glacier melt were the most important endmembers for stream runoff during late spring, summer and early fall. The temporal variability of the tracer concentration suggested that stream water was dominated by snowmelt at the beginning of the melting season (May-June), by a mixture of snowmelt and glacier melt during mid-summer (Julyearly August), and by glacier melt during the end of the summer (end of August-September). The same seasonal pattern observed in streamflow was also evident for groundwater, with the highest electrical conductivity and least negative isotopic values found during cold or relatively less warm periods, when the melt of snowpack and ice was limited. Particularly, the application of a two-component mixing model to data from different springs showed that the snowmelt contribution to groundwater recharge varied between 21 % (±3 %) and 93 % (±1 %) over the season, and the overall contribution during the three study years ranged between 58 % (±24 %) and 72 % (±19 %). These results provided new insights into the isotopic characterization of the study catchment presenting further understanding of the spatio-temporal variability of the main water sources contributing to runoff.

Spatial and temporal variability of bacterial communities in high alpine water spring sediments

“…The trend in isotopic depletion and geochemical enrichment in 2013 is in good agreement with spring monitoring since 2011 [38]. While isotopic depletion until August 2013 indicated increasing snowmelt contributions, isotopic enrichment revealed decreased snowmelt contributions in September.…”

“…However, isotopic variations at SPR4 suggested the maximum contribution of snowmelt in June, with a gradual decrease over the season. In contrast, the EC concentration showed gradually increasing concentrations, instead of following isotopic behavior that had occurred during the previous years [38]. Therefore, the highest dilution with snowmelt water containing less solutes was anticipated, and already took place in June.…”

The importance of snowmelt spatiotemporal variability for isotope-based hydrograph separation in a high-elevation catchment

“…Snowmelt is a major contributor to streamflow during the spring freshet period in alpine regions and large amounts of snowmelt water infiltrate into the soil and recharge groundwater (Penna et al, 2014). The hydrological response of the stream followed the variations of air temperature, as already observed by Braithwaite and Olesen (1989) (Fig.…”

Towards a tracer-based conceptualization of meltwater dynamics and streamflow response in a glacierized catchment

“…Penna et al (2014) showed a preliminary analysis on the highly complex EC and isotopic signature of different waters sampled in the catchment, identifying distinct tracer signals in snowmelt and glacier melt. These two end-members dominated the streamflow throughout the late spring and summer, whereas liquid precipitation played a secondary role, limited to rare intense rainfall events.…”