CASE STUDY
Contribution of glacier melt to river runoff in a medium sized Alpine catchment Gernot Koboltschnig, Dept. for Water Management Amt der Kaerntner Landesregierung, Provincial Government of Carinthia, Austria
The contribution of glacier melt was investigated for the 5% glacierized Upper Salzach catchment area (593 km²) in the eastern European Alps. The basin is situated in the north of the Hohe Tauern region in the central Alps of Austria (Fig. 6). The land cover of the Upper Salzach watershed is dominated by coniferous forests as well as grassland and rocky areas. Settle- ments can mainly be found in the valleys, whereas Mittersill is the largest village with a population of about 5500 inhabitants.
For this study the hydrological model PREVAH was applied us- ing an advanced temperature-index approach on an hourly time basis and driven by air temperature and precipitation observa- tions from in and around the basin (Koboltschnig et al., 2008).
The model was calibrated in a 3 year period and validated in anoth- er 3 year period based on a two-step procedure using observed dis- charge and satellite derived snow-cover distribution. Nash-Sutcliffe Efficiency Criteria (R²) of the hourly discharge simulations were be- tween 0.83 and 0.89 with the exception of the extreme summer of 2003 which had an R² of 0.74. The reliability of model results was good as the model simulated all components of the hydrologic cy- cle considering the water balance. By applying a multi-criteria result validation approach, not only the discharge at the basin outlet was used for validation purposes, but the simulated snow cover area (SCA) was also compared to satellite observations of SCA. Addi- tionally, simulated glacier mass balances were compared to nearby observed glaciers. In contrast with other studies where an excess
Figure 6: Upper Salzach catchment with the outlet at Mittersill (MI) at 780 m a.s.l. Mount Großvenediger (GV) at 3666 m a.s.l. is the highest peak in that area. Dark grey areas indicate glaciers. Rings, dots and crosses show meteo- rological stations within and outside the basin. Arrows show glaciers with mass balance observations.
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