5th Swiss Geoscience Meeting, Geneva 2007
Impact of glacier retreat in the Glacier de Zinal
catchment on future runoff
Daniel Farinotti, Matthias Huss, Andreas Bauder and Martin Funk
Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW), ETH Zürich,
8092 Zürich, Switzerland. E-mail: farinotti@vaw.baug.ethz.ch
Glaciers in the Alps play an important role for water resource management (e.g.
freshwater, irrigation, hydropower production). Climate change will alter the
runoff characteristics of high alpine catchment basins significantly and have
impacts on the management of the water resources. In the uppermost valley of
Zinal, Valais, Switzerland, water intakes are planned to capture the runoff from
three drainage basins glaciated to more than 50%. In this applied project we
make predictions of seasonal runoff volumes until 2100. The modelling study
includes glacier volume determination, climate scenarios, snow and ice melt
and the reduction of glacier coverage.
Detailed knowledge of the ice thickness distribution is the essential information
for an accurate future prediction. We improved the approach for the spatial ice
volume determination based on direct measurements by radio-echo soundings
and glacier-dynamic considerations.
Glacier mass balance and runoff is calculated using a distributed temperatureindex melt model (Hock, 1999) with an accumulation scheme. Required input
variables are temperature and precipitation in daily time steps and a digital
elevation model (DEM). The model is calibrated and validated using decadal ice
volume changes derived from 4 DEMs between 1961 and 2006, observed end
of summer snow lines (1969-1981) and measured monthly runoff at a gauging
station 7 km downvalley. A glacier retreat model is coupled to the mass
balance-runoff model including evaporation in order to account for the reduction
of the glaciated area. It is based on mass conservation and reproduces 3D
spatial changes of the glacier surface geometry.
Using a probabilistic distribution of different climate scenarios (Frei, 2005) for
the seasonal change in temperature and precipitation, we calculate the runoff at
the water intakes. A stochastic internal climate variability is superimposed and
provides estimates of the uncertainty in modelled runoff due to year-to-year
fluctuations of the climate variables. Annual discharge from the catchment
basins shows an initial increase which is due to the release of water from glacial
storage. After some decades (depending on catchment characteristics and the
applied climate change scenario) runoff starts to decrease and drops below the
current level. In all climate projections the glacial area decreases dramatically.
Less than 5% of the glaciers will be left by 2100. The fraction of discharge
during spring and early summer increases whereas the runoff in July and
August decreases significantly.
5th Swiss Geoscience Meeting, Geneva 2007
Figure 1. Ice-thickness distribution in the study-area.
Figure 2. Mean daily discharge stacked over three 10-year time-snapshots in
the future.
REFERENCES
Frei, C. (2005). Die Klimazukunft der Schweiz - Eine probabilistische Projektion.
Available at http://www.occc.ch, 8pp.
Hock, R. (1999). A distributed temperature-index ice- and snowmelt model
including potential direct solar radiation. Journal of Glaciology, 45(149): 101111.