Identifying run‐off contributions during melt‐induced run‐off events in a glacierized alpine catchment

Abstract

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. High‐elevation snowmelt, glacier melt and autumn groundwater were identified as major end‐members. Discharge and tracers in the stream followed the diurnal variations of air temperature but markedly reacted to rainfall inputs. Hysteresis patterns between discharge and electrical conductivity during the melt‐induced run‐off events revealed contrasting loop directions at the two monitored stream sections. Snowmelt contribution to run‐off was highest in June and July (up to 33%), whereas the maximum contribution of glacier melt was reached in August (up to 65%). The maximum groundwater and rainfall contributions were 62% and 11%, respectively. Run‐off events were generally characterized by decreasing snowmelt and increasing glacier melt fractions from the beginning to the end of the summer 2012, while run‐off events in 2013 showed less variable snowmelt and lower glacier melt contributions than in 2012. The results provided essential insights into the complex dynamics of melt‐induced run‐off events and may be of further use in the context of water resource management in alpine catchments. Copyright © 2015 John Wiley & Sons, Ltd.

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

“…The increase in discharge coincides with decreasing streamflow δ 18 O during the early melt event (Fig. 4a and c) and confirms the earlier findings of Engel et al (2016), who identified inverse relationships between streamflow δ 18 O and discharge during several 24 h events in an adjacent valley on the southern side of the main Alpine ridge, although their findings rely on streamflow contributions from snow and glacier melt. The lower stream water isotopic composition during peak melt suggests a remarkable contribution of more depleted snowmelt to streamflow and therefore confirms the results of the IHS.…”

“…At the event-scale comparable studies are rare. Engel et al (2016) report a maximum daily snowmelt contribution estimated with a three-component hydrograph separation of 33 % for an 11 km 2 southwest of the Rofen valley with similar physiographic characteristics, but on the southern side of the main Alpine ridge. It should be mentioned that in their study, runoff was fed by three components (snowmelt, glacier melt, and groundwater) and lower snowmelt contributions were prevalent because most of the catchment area (69 %) was snow free.…”

“…These scenarios (NORTH/SOUTH) are theoretical and it is obvious that it is not recommended to conduct a IHS analysis by using only samples from either north-or south-facing slopes in catchments with complex terrain. Similar to the VWE method, snowmelt isotopic data were not volume weighted in other studies (e.g., Engel et al, 2016) where snowmelt data were not available. This has a more distinct effect on IHS during the early melt season because of the higher spatiotemporal variability in snowmelt (and its isotopic composition) compared to the peak melt season and led to a deviation in the snowmelt fraction in streamflow of 2 and 3 % compared to the VWS and VWO approaches, respectively.…”

“…The observed time lags (Fig. 3b and c) between maximum daily air temperature and daily peak flow are common in mountain catchments (Engel et al, 2016;Schuler, 2002). During peak melt, the flashy hydrograph revealed less variation in the timing of peak discharge of 7-day data (Fig.…”

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

“…For consistency, sampling was carried out during the same time interval defined from 12 am to 4 pm. Previous measurements showed that the main melt water contribution was from snow in June and July (recent and old snowmelt, respectively), from glacier ice in August and from rainfall in September [25]. Therefore, the assumption that a single day is representative of the monthly scale is legitimate.…”