The Seasonal Snow Cover in a Small Alpine Catchment (Austria)
Ulrike Nickus1 and Hansjrg Thies2
From December 1996 to June 1997 the snow cover in the catchment of a small high mountain lake in
the Austrian Alps was intensively investigated. Concentration and load of atmospheric trace sub-
stances in the snowpack, their temporal variability in the course of a winter, and local differences in
snow and substance deposition within the watershed were the main topics of interest. The study was
related to the EU project MOLAR, which investigates the dynamic response of remote mountain
lake ecosystems to environmental change, and in the framework of which the input of atmospheric
trace substances to the catchment (0.2-km2 size) of Lake Gossenklle should be determined.
Measurements were performed weekly at three selected sites between 2420 and 2510 m a.s.l. A
detailed recording of snow stratigraphy, density, and temperature accomplished the snow sampling
program. Snow was collected along vertical profiles at increments of 10 cm from the top of the
snowpack down to the rocky bottom of the catchment. Chemical analysis comprised the determina-
tion of major ions by ion exchange chromatography, pH, conductivity, and alkalinity by Gran's
titration.
Although only at horizontal distances of some 200 m, the snowpack at the three sites differed consid-
erably in water equivalent, stratigraphy, and ion concentrations. Local differences of the water
equivalent up to a factor of three by the end of the accumulation period were influenced by varying
wind drift and aspect rather than by the effect of altitude. Due to the enhanced vertical mixing of the
atmosphere, mean ion concentrations were about three times higher in spring than in midwinter.
Peak values in April ranged from 5 to 7 eq/L for sulfate, 11 to 17 eq/L for nitrate, and 6 to 9 eq/L
for ammonium. However, considerably higher concentrations were found in distinct layers of March
and April snow.
The poster will focus on the seasonal development of the snow cover at three sites of the catch-
ment. It will show vertical profiles of snow temperature and ion concentrations covering both the
accumulation and melting period. Effects of snowmelt on small brooks and on the lake water
chemistry are considered, revealing a temporary dilution of most ions in brook and lake water.
The investigation also clearly demonstrated that the selection of both date and site of sampling
may strongly influence the result in respect to the measured input of atmospheric trace substances
into a catchment.
1
Institute of Meteorology and Geophysics, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria
2
Institute of Zoology and Limnology, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck,
Austria
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