Snow hydrological research in partly glacierized watersheds
Alpine regions change continuously. Retreating
glaciers provide an excellent opportunity to study the development of pristine
landmasses. The processes causing these changes work over relatively short time-scales,
and research on glacier forefields is therefore very important.
We are studying hydrological processes of the
forefield to the Damma glacier in Canton Uri within two interdisciplinary
research projects dealing with development of soils and ecosystems: BigLink and SoilTrec. Our specific focus is on
the linkage between climatic factors, snow melt, ice melt, discharge and soil
moisture. A central question is also to assess the consequences of climate
change and further glacier retreat on the water resources in the region (Fig. 1).
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Fig. 1: The water budget of the forefield downstream of the Damma glacier in
canton Uri is dominated by snow and glacier melt processes. The water feeds the
Göschernalpsee, which is utilized for hydropower production.
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Snow and ice melt in mountain
torrents
The discharge varies
strongly during the season in the study watershed (Fig. 2). Despite that the
catchment is 50% glacierized, snow melt is the greatest contributor to runoff. Only
later in the year, ice melt dominates the runoff regime, as a larger portion of
the glacier surface becomes snow free. Under current climatic conditions rain
only contributes to a small fraction of the total discharge. However, our
simulations indicate that the water sources contributing to discharge will
change in future due to climate change.
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Fig. 2: Runoff in partly glacierized watersheds varies largely during the season
(upper panel). Model simulations show that snow melt has the largest
contribution to total discharge. Only later in the year, ice melt presents a
greater influence on the discharge regime (lower panel).
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Diurnal variations
similar to tidal regions
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Fig. 3: Melt processes display strong diurnal cycles. The snow depth retreat
shows a stair-shaped pattern (upper panel). These diurnal variations propagate
and can be found in the measured soil moisture (middle panel) and in the runoff
(lower panel).
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Due to the meteorological forcing, many hydrological processes occurring
in the study watershed display a large diurnal cycle. Therefore, snow depth displays
a ‘stair-shaped’ pattern during the melting season (Fig. 3). Correspondingly we
also find clear diurnal patterns in soil moisture and discharge measurements. Diurnal
stage fluctuations in the glacial streams show similar behavior as tidally influenced
rivers. These relationships allowed groundwater models originally developed for
coastal regions to be applied across our study watershed with only small
adaptations.
Groundwater influence of glacier forefield development
Groundwater in glacier forefields transport chemical
solutes created by weathering processes. Those weathering products constitutes
an important boundary condition for plants, and influences the ongoing
ecosystem succession on the forefield. Thus, the subsurface hydrology largely
influences how the newly exposed land from glacial retreat may develop.
However, knowledge about hydrological processes in high alpine topography is limited.
Our research is able to contribute to not only a better understanding of
hydrological processes in mountainous regions but also develop new methods with
which those ecosystems may be analyzed and modeled (Fig. 4).
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Fig. 4: Snow and glacier melt influences the groundwater stage on proglacial
fields. Numerical models allow us to simulate how stage variations in the
stream propagate into the groundwater of the nearby riparian zone.
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Further
information
Project
participants
- Florian Kobierska
- Jan Magnusson
- Tobias Jonas
- Bruno Fritschi
- Manfred Stähli
Contact
