Runoff generation in mountain catchments: long-term hydrological monitoring in the Rio Vauz Catchment, Italy

Self Cite

The spatial and temporal characterization of geochemical tracers over Alpine glacierized catchments is particularly difficult, but fundamental to quantify groundwater, glacier melt, and rain water contribution to stream runoff. In this study, we analysed the spatial and temporal variability of δ2H and electrical conductivity (EC) in various water sources during three ablation seasons in an 8.4‐km2 glacierized catchment in the Italian Alps, in relation to snow cover and hydro‐meteorological conditions. Variations in the daily streamflow range due to melt‐induced runoff events were controlled by maximum daily air temperature and snow covered area in the catchment. Maximum daily streamflow decreased with increasing snow cover, and a threshold relation was found between maximum daily temperature and daily streamflow range. During melt‐induced runoff events, stream water EC decreased due to the contribution of glacier melt water to stream runoff. In this catchment, EC could be used to distinguish the contribution of subglacial flow (identified as an end member, enriched in EC) from glacier melt water to stream runoff, whereas spring water in the study area could not be considered as an end member. The isotopic composition of snow, glacier ice, and melt water was not significantly correlated with the sampling point elevation, and the spatial variability was more likely affected by postdepositional processes. The high spatial and temporal variability in the tracer signature of the end members (subglacial flow, rain water, glacier melt water, and residual winter snow), together with small daily variability in stream water δ2H dynamics, are problematic for the quantification of the contribution of the identified end members to stream runoff, and call for further research, possibly integrated with other natural or artificial tracers.

Section: Conclusion and Future Researchmentioning

confidence: 99%

Understanding hydrological processes in glacierized catchments: Evidence and implications of highly variable isotopic and electrical conductivity data

Zuecco

Carturan

Blasi

et al. 2019

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“…We employed ground‐based TIR imagery in an analogous approach to Pfister et al () and Glaser et al (; 2016; i.e., to detect temperature differences between the water at the ground surface—saturated areas—and the surrounding environment—unsaturated areas), to obtain a unique dataset of 2 years of biweekly observations of different riparian surface saturated areas within the Weierbach catchment in Luxembourg. This long‐term studied headwater catchment (0.42 km 2 ) is a reference site for rainfall‐dominated mountainous catchments (Zuecco, Penna, & Borga, ). The Weierbach is characterized by homogeneous pedology and geology and exhibits a hydrological response that is highly influenced by the wetness state of the system.…”

Section: Introductionmentioning

confidence: 99%

Saturated areas through the lens: 1. Spatio‐temporal variability of surface saturation documented through thermal infrared imagery

Antonelli

Glaser

Teuling

et al. 2020

Surface saturated areas are key features in generating run‐off. A detailed characterization of the expansion and contraction of surface saturation in riparian zones and its connectivity to the stream is fundamental to improve our understanding of the spatial and temporal variability of streamflow generation processes. In this first contribution of a series of two papers, we used ground‐based thermal infrared imagery for characterizing riparian surface saturation seasonal dynamics of seven different riparian areas in the Weierbach catchment (0.42 km2), a small forested catchment in Luxembourg. We collected biweekly panoramic images of the seven areas over a period of 2 years. We identified the extension of saturation in each collected panoramic image (i.e., percentage of pixels corresponding to saturated surfaces in each riparian area) to generate time series of surface saturation. Riparian surface saturation in all areas was seasonally variable, and its dynamics were in accordance with lower hillslope groundwater level fluctuations. Surface saturation in the different areas related to catchment outlet discharge through power law relationships. Differences in these relationships for different areas could be associated with the location of the areas along the stream network and to a possible influence of local riparian morphology on the development of surface saturation, suggesting a certain degree of intracatchment heterogeneity. This study paves the way for a subsequent investigation of the spatio‐temporal variability of streamflow generation in the catchment, presented in our second contribution.

“…Here, we investigate the link between surface saturation dynamics (read as both riparian surface saturation and dynamics of expansion and contraction of the active portion of the stream network) and streamflow generation in the Weierbach catchment in Luxembourg. The Weierbach catchment is a long‐term studied catchment, nowadays considered as a reference catchment for rainfall‐dominated mountainous catchments (Zuecco, Penna, & Borga, ). The catchment's hydrological response is influenced by a storage threshold (Martínez‐Carreras et al, ), and it is characterized by a single spiky peak in case of dry antecedent conditions and by a first spiky peak followed by a broader peak of longer duration in case of wet antecedent conditions (Martínez‐Carreras et al, ; Wrede et al, ).…”

Section: Introductionmentioning

confidence: 99%

Saturated areas through the lens: 2. Spatio‐temporal variability of streamflow generation and its relationship with surface saturation

Antonelli

Glaser

Teuling

et al. 2019

Investigating the spatio‐temporal variability of streamflow generation is fundamental to interpret the hydrological and biochemical functioning of catchments. In humid temperate environments, streamflow generation is often linked to the occurrence of near stream surface saturated areas, which mediate hydrological connectivity between hillslopes and streams. In this second contribution of a series of two papers, we used salt dilution gauging to investigate the spatio‐temporal variability of streamflow in different subcatchments and for different reaches in the Weierbach catchment (0.42 km2) and explored the topographical controls on streamflow variability. Moreover, we mapped stream network expansion and contraction dynamics. Finally, we combined the information on the spatio‐temporal variability of streamflow with the characterization of riparian surface saturation dynamics of seven different areas within the catchment (mapped with thermal infrared imagery, as presented in our first manuscript). We found heterogeneities in the streamflow contribution from different portions of the catchment. Although the size of the contributing area could explain differences in subcatchments' and reaches' net discharge, no clear topographic controls could be found when considering the area‐normalized discharge. This suggests that some local conditions exert control on the variability of specific discharge (e.g., local bedrock characteristics and occurrence of perennial springs). Stream network dynamics were found not to be very responsive to changes in catchment's discharge (i.e., total active stream length vs. stream outlet discharge relationship could be described through a power law function with exponent = 0.0195). On the contrary, surface saturation dynamics were found to be in agreement with the level of streamflow contribution from the correspondent reach in some of the investigated riparian areas. This study represents an example of how the combination of different techniques can be used to characterize the internal heterogeneity of the catchment and thus improve our understanding of how hydrological connectivity is established and streamflow is generated.