EFFECTS OF CLIMATE-CHANGE ON SNOW ACCUMULATION AND MELTING IN THE BROYE CATCHMENT (SWITZERLAND)

The study used a daily step conceptual hydrological model to examine t he effects of climate change on snowfall accumulation and on snow cove r melting in the Broye catchment (moderate relief - altitude from 400 to 1500 m a.s.l.). Five elevation bands representing a range of climat ic conditions were used together with three realistic climate change s cenarios based loosely on GCM's predictions and which reflect feasible changes by extending time periods. For a very moderate climate change (rise in air temperature of ca 1 degrees C), possibly in a near futur e, the reduction of snow cover duration, mean water equivalent and mon thly maximum water equivalent is the most sensitive in the lower part of the catchment and during the first and last months of the snow seas on. In the higher part of the basin and during the colder months Janua ry and February, similar reduction rates can be expected in case of la rger climate changes. The floods due to the melting of snow cover are lower. Sometimes rainfall, considered as snow in the present day condi tions, generates additional floods during the winter season. For winte r sports resorts below 1500 m a.s.l., even the very moderate climatic change scenario (temperature rise around 1 degrees C) leads to economi cally very difficult conditions. Finally, a climatic change detection index based on snow cover duration is proposed.