Towards a tracer-based conceptualization of meltwater dynamics and streamflow response in a glacierized catchment (original) (raw)
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Tracer-based analysis of spatial and temporal variations of water sources in a glacierized catchment
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.
Tracer-based analysis of spatial and temporal variation of water sources in a glacierized catchment
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.
Studying the dynamic of a high alpine catchment based on multiple natural tracers
2022
Hydrological processes in high elevation catchments are largely influenced by snow accumulation and melt, as well as summer rainfall input. The use of the stable isotopes of water as a natural tracer has become popular over recent years to characterize water flow paths and storage in such environments, in conjunction with electric conductivity (EC) and water temperature measurements. In this work, we analyzed in detail the potential of year round samples of these natural tracers to characterize hydrological processes in a snow-dominated Alpine catchment. Our results underline that water temperature measurements in springs, groundwater and in-stream are promising to trace flow path depth and relative flow rates. The stable isotopes of water are shown here to be particularly valuable to get insights into the interplay of subsurface flow and direct snowmelt input to the stream during winter and early snow melt periods. Our results underline the critical role of subsurface flow during all melt periods and the presence of snowmelt even during winter base flow. We furthermore discuss why reliably detecting the role of subsurface flow requires year-round water sampling in such environments. A key conclusion of our work is the added value of soil and water temperature measurements to interpret EC and isotope analyses, by giving additional information on snowfree periods and on flow path depths.
2018
Understanding the hydrological and hydrochemical functioning of glacierized catchments requires the knowledge of the different controlling factors and their mutual interplay. For this purpose, the present study was carried out in two sub-catchments of the glacierized Sulden River catchment (130 km 2 ; eastern Italian Alps) in 2014 and 2015, characterized by a similarly sized but contrasting geological setting. Samples were taken at different space and timescales for analysis of stable isotopes in water, electrical conductivity, and major, minor and trace elements. At the monthly sampling scale, complex spatial and temporal dynamics for different spatial scales (0.05-130 km 2) were found, such as contrasting electrical conductivity gradients in both sub-catchments. For the entire Sulden catchment, the relationship between discharge and electrical conductivity showed a monthly hysteretic pattern. Hydrometric and geochemical dynamics were controlled by interplay of meteorological conditions, topography and geological heterogeneity. A principal component analysis revealed that the largest variance (36.3 %) was explained by heavy metal concentrations (such as Al, V, Cr, Ni, Zn, Cd and Pb) during the melting period, while the remaining variance (16.3 %) resulted from the bedrock type in the upper Sulden subcatchment (inferred from electrical conductivity, Ca, K, As and Sr concentrations). Thus, high concentrations of As and Sr in rock glacier outflow may more likely result from bedrock weathering. Furthermore, nivo-meteorological indicators such as daily maximum air temperature and daily maximum global solar radiation represented important meteorological controls, with a significant snowmelt contribution when exceeding 5 • C or 1000 W m −2 , respectively. These insights may help in better understanding and predicting hydrochemical catchment responses linked to meteorological and geological controls and in guiding future classifications of glacierized catchments according to their hydrochemical characteristics. 1 Introduction Runoff from glacierized catchments is an important fresh water resource to downstream areas (Kaser et al., 2010; Viviroli et al., 2011). High-elevation environments face rapid and extensive changes through retreating glaciers, reduced snow cover and permafrost thawing (
Annals of Glaciology, 2005
Measurements of electrical conductivity (EC) and deuterium isotopes in glacier run-off provide the basis for the application of simple mixing models that separate hydrographs into four constitutive components: subglacial, englacial, melt and rainfall-derived waters. Volumes of these components are determined from the models in two adjacent drainage basins within the glacier. Peak arrival times of both EC and isotopes during discharge events on short-term time-scales (days to weeks) differ in each terminus stream by as much as a factor of 5. Englacial water storage determined from the model varied greatly (98%) between neighboring basins within the glacier. Estimates of basal water volumes expressed as a layer thickness at the bed of the glacier differed by 50% (5 and 10mm each). Other results suggest that a greater percentage of water is stored at the glacier bed during rainfall events, and exceeds the storage capacity found within the seasonal snow and englacial zones combined.
Identifying runoff contributions during melt-induced runoff events in a glacierized Alpine catchment
Hydrological Processes
We analysed contributions to run-off using hourly stream water samples from seven individual melt-induced run-off events (plus one rainfall event) during 2011, 2012 and 2013 in two nested glacierized catchments in the Eastern Italian Alps. Electrical conductivity and stable isotopes of water were used for mixing analysis and two-component and three-component hydrograph separation.
Annals of Glaciology, 2016
ABSTRACTVirkisjökull is a rapidly retreating outlet glacier draining the western flanks of Öræfajökull in SE Iceland. Since 2011 there have been continuous measurements of flow in the proglacial meltwater channel and regular campaigns to sample stable isotopes δ2H and δ18O from the river, ice, moraine springs and groundwater. The stable isotopes provide reliable end members for glacial ice and shallow groundwater. Analysis of data from 2011 to 2014 indicates that although ice and snowmelt dominate summer riverflow (mean 5.3–7.9 m3 s−1), significant flow is also observed in winter (mean 1.6–2.4 m3 s−1) due primarily to ongoing glacier icemelt. The stable isotope data demonstrate that the influence of groundwater discharge from moraines and the sandur aquifer increases during winter and forms a small (15–20%) consistent source of baseflow to the river. The similarity of hydrological response across seasons reflects a highly efficient glacial drainage system, which makes use of a serie...
Water, 2020
Glaciers are shrinking due to global warming, resulting in a diminishing contribution of ice and snowmelt to headwaters and subsequent consequences to freshwater ecosystems. Within this context, we tested whether water-stable isotopes are spatio-temporal tracers of (i) water in high altitude periglacial environments, being the isotopic signature of surface water inherited from the snow/icemelt, groundwater, and rainfall; and (ii) regional (year-specific) meteorological conditions, being the isotopic signature of precipitations affected by air temperature, humidity and aqueous vapour origin, ascribing stable isotopes to the list of "essential climate variables″ (ECVs). To this end, we investigated the ionic and isotopic composition (δ 18 O and δ 2 H) of six high-altitude streams and one pond in the Italian Alps (Noce and Sarca basins) during the ablation season in 2018. Differences between habitat types (pond, kryal, rhithral, krenal) were detected. More negative values of δ 18 O and δ 2 H were recorded in the kryal and glacio-rhithral sites, dominated by ice and snowmelt, in early summer. Less negative values were recorded in these sites in late summer, as well as in the krenal sites, which were dominated by groundwater and rainfall inputs. The isotopic results also show that the complex alpine orography influences air masses and moisture, ultimately resulting in isotopic differences in the precipitations of neighboring but distinct catchments (Sarca and Noce basins). On average, less negative values were recorded in the Sarca basin, characterized by a higher contribution of precipitation of Mediterranean origin. In general, isotopic results of the entire water population appeared to be strongly influenced by the regional climatic anomaly of 2018, which was anomalously warm. Therefore, the study will provide additional information for the climate change debate, proposing water isotopes as ECVs for assessing change in a warmer future.