Origin of surface and subsurface waters in a periglacial catchment analysed by means of environmental tracers (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.
Hydrology and Earth System Sciences Discussions, 2016
Multiple water sources and the physiographic heterogeneity of glacierized catchments hamper a complete conceptualization of runoff response to meltwater dynamics. In this study, we used environmental tracers (stable isotopes of water and electrical conductivity) to obtain new insight into the hydrology of glacierized catchments, using the Saldur River catchment, Italian Alps, as a pilot site. We analysed the controls on the spatial and temporal patterns of the tracer signature in the main stream, its selected tributaries, shallow groundwater, snowmelt and glacier melt over a three-year period. We found that stream water electrical conductivity and isotopic composition showed consistent patterns in snowmelt-dominated periods whereas the streamflow contribution of glacier melt altered the correlations between the two tracers. By applying two- and three-component mixing models we quantified the seasonally-variable proportion of groundwater, snowmelt and glacier melt at different locati...
Contrasting physical and chemical conditions of two springs fed by active rock glaciers
2020
Rock glaciers are increasingly influencing the hydrology and water chemistry of Alpine catchments, with important implications for drinking water quality and ecosystem health under a changing climate. During summers of 2017 - 2019, we monitored the physical and chemical conditions of springs emerging from two active rock glaciers (ZRG and SRG) with distinct geomorphological settings in the Eastern Italian Alps (Solda/Sulden catchment). Both springs had constantly cold waters (1.4 ± 0.1 °C), and their ionic composition was dominated by SO42-, HCO3-, Ca2+ and Mg2+. Concentrations of major ions and trace elements, and values of water isotopes (δ18O, δ2H), increased towards autumn with an asymptotic trend at SRG, and a positive unimodal pattern at ZRG, where concentrations peaked 60 - 80 days after the end of the snowmelt. Wavelet analysis on electrical conductivity (EC) and water temperature records revealed daily cycles only at SRG, and significant weekly/biweekly fluctuations at both...
Spatial and temporal variability of stable water isotopes in snow related hydrological processes
Stable water isotopes (18O, 2H) have been measured and applied in snow hydrology since the 1970s. They are used to identify water sources, separate hydrograph components and estimate the mean transit time of water in a catchment or an aquifer (e.g. DÓŠA et al., 2011). Recent technological progress in laser spectroscopy has paved the road for cheaper and simultaneous analyses of both 18O and 2H. The hydrological community has thus the possibility to obtain longer data series with higher resolution that could lead to an improved understanding of water movement in the hydrological cycle (LYON et al., 2009). The objective of this article is to report the main results of detailed monitoring of the variability of stable water isotopes in the snow-related part of hydrological cycle. We studied the isotopic composition of snowfall, snow cover, snowmelt, soil, groundand stream waters in the mountain environment of northern Slovakia in the two contrasting winters of 2011 and 2012.
Active rock glaciers as shallow groundwater reservoirs, Austrian Alps
Grundwasser
Rock glaciers are the most prominent landforms of alpine permafrost and comprise complex shallow aquifer systems in (high) alpine catchments. Recession analyses of groundwater discharge of four active rock glaciers that contain permafrost ground ice show that they have a base flow component of the order of a few liters per second, similar to that of a relict rock glacier in which permafrost ground ice is absent. This is related to an unfrozen (fine-grained) base layer with a thickness of about 10 m. Based on a threshold analysis of precipitation events and event water discharge, depressions atop the bedrock or the permafrost table seem to play only a minor role in storing groundwater. This important finding has rarely been documented, but is highly relevant for optimal groundwater resources management in sensitive (high) alpine catchments and ecosystems. All the rock glaciers analyzed here are located in the Austrian Alps and represent the nationwide sites where suitable discharge d...
Contrasting physical and chemical conditions of two rock glacier springs
Hydrological Processes, 2021
Rock glaciers are increasingly influencing the hydrology and water chemistry of Alpine catchments. During three consecutive summers (2017-2019), we monitored by recording probes and fortnightly/monthly field campaigns the physical and chemical conditions of two rock glacier springs (ZRG, SRG) in the Zay and Solda/Sulden catchments (Eastern Italian Alps). The springs have contrasting hydrological conditions with ZRG emerging with evident
Groundwater in catchments headed by temperate glaciers: A review
Earth-Science Reviews, 2018
Catchments headed by temperate glaciers are severely impacted by climate change, and extensively studied from glaciological and surface hydrology perspectives. However groundwater in the same catchments is much more seldom mentioned, and even less studied. The few available studies found in the scientific literature tend to show a particularly high recharge of aquifers by glacial meltwater, a strong connection between surface and ground waters, and quite high hydraulic permeability in moraines and tills aquifers. New and more systematic studies could confirm and details these results. Such characteristics suggest that groundwater in coastal catchments headed by temperate glaciers could feed offshore fresh groundwater stocks. The role of potential deeper aquifers in fractured bedrock remains completely unknown. The numerous examples of natural hazards and of the sensitivity of water resources to the water cycle in catchments headed by temperate glaciers underline the importance of the study of hydrogeology, and of socioeconomic aspects, in these catchments where population is glacier-dependant. The study of groundwater in catchments headed by temperate glaciers is just at the start and there is much to be studied.