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CR 26:113-129 (2004)
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Abstract
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Differential impacts of climate change on the hydrology of two alpine river basins
Karsten Jasper1,*, Pierluigi Calanca1, Dimitrios Gyalistras2, Jürg Fuhrer1
1Swiss Federal Research Station for Agroecology and Agriculture (FAL), Air Pollution/Climate Group, 8046 Zürich, Switzerland
2University of Bern, Institute of Geography, 3012 Berne, Switzerland
*Email: karsten.jasper@fal.admin.ch
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ABSTRACT: Earlier impact studies have suggested that climate change may severely alter the hydrological cycle in alpine terrain. However, these studies were based on the use of a single or a few climate scenarios only, so that the uncertainties of the
projections could not be quantified. The present study helps to remedy this deficiency. For 2 Alpine river basins, the Thur basin (1700 km2) and the Ticino basin (1515 km2), possible future changes in the natural water budget
relative to the 1981-2000 (Thur) and 1991-2000 (Ticino) baselines were investigated by driving the distributed catchment model WaSiM-ETH with a set of 23 regional climate scenarios for monthly mean temperature (T) and precipitation (P). The
scenarios referred to 2081-2100 and were constructed by applying a statistical-downscaling technique to outputs from 7 global climate models. The statistical-downscaling scenarios showed changes in annual mean T between +1.3 and +4.8°C and in
annual total P between -11 and +11%, with substantial variability between months and catchments. The simulated overall changes in the hydrological water cycle were qualitatively robust and independent of the choice of a particular scenario. In all
cases, the projections showed strongly decreased snowpack and shortened duration of snow cover, resulting in time-shifted and reduced runoff peaks. Substantial reductions were also found in summer flows and soil-water availability, in particular at lower
elevations. However, the magnitudes and certain aspects of the projected changes depended strongly on the choice of scenario. In particular, quantitative projections of soil moisture in the summer season and of the runoff in both the summer and autumn
seasons were found to be quite uncertain, mainly because of the uncertainty present in the scenarios for P. Our findings clearly demonstrate that quantitative assessments of hydrological changes in the Alps using only a small number of scenarios
may yield misleading results. This work strengthens our confidence in the overall results obtained in earlier studies and suggests distinct shifts in future Alpine hydrological regimes, with potentially dramatic implications for a wide range of sectors.
KEY WORDS: Climate change impact · Regional climate scenarios · Uncertainty analysis · Mountain hydrology · Distributed hydrological modeling · WaSiM-ETH
Full text in pdf format
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Published in CR Vol.
26, No. 2
(2004) on May 25
Print ISSN: 0936-577X; Online ISSN: 1616-1572.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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