Abstract
Abstract. 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 3-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 locations along the stream. We provided four model scenarios based on different tracer signatures of the end-members; the highest contributions of snowmelt to streamflow occurred in late spring–early summer and ranged between 70 and 79 %, according to different scenarios, whereas the largest inputs by glacier melt were observed in mid-summer, and ranged between 57 and 69 %. In addition to the identification of the main sources of uncertainty, we demonstrated how a careful sampling design is critical in order to avoid underestimation of the meltwater component in streamflow. The results of this study supported the development of a conceptual model of streamflow response to meltwater dynamics in the Saldur catchment, which is likely valid for other glacierized catchments worldwide.
Highlights
Glacierized catchments are highly dynamic systems characterized by large complexity and heterogeneity due to the interplay of several geomorphic, ecological, climatic and hydrological processes
We provided four model scenarios based on different tracer signatures of the end-members; the highest contributions of snowmelt to streamflow occurred in late spring–early summer and ranged between 70 and 79 %, according to different scenarios, whereas the largest inputs by glacier melt were observed in mid-summer, and ranged between 57 and 69 %
The Saldur catchment was characterized by a marked variability of tracer signature within the same water compartment both in time and in space (Table 6, Figs. 2 and 3)
Summary
Glacierized catchments are highly dynamic systems characterized by large complexity and heterogeneity due to the interplay of several geomorphic, ecological, climatic and hydrological processes. Water seasonally melting from snowpack and glacier bodies can constitute a larger contribution to annual streamflow than rain (Cable et al, 2011; Jost et al, 2012), and is widely used, especially in Alpine valleys, for irrigation and hydropower production (Schaefli et al, 2007; Beniston, 2012) It is pivotal for an effective adoption of water resources strategies to understand the origin of water and to quantify the proportion of snowmelt and glacier melt in streamflow (Finger et al, 2013; Fan et al, 2015). To achieve this goal it is critical to gain a more detailed understanding of the hydrological functioning of glacierized catchments through the analysis of the spatial and temporal variability of water sources and the spatial and seasonal meltwater (snowmelt plus glacier melt) dynamics.
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