Challenges of alpine catchment management under changing climatic and anthropogenic pressures

Water resources in mountain areas are particularly important with respect to new and increasing pressures in the headwater areas of catchments. Climate change has resulted in a decrease in precipitation and decrease in groundwater recharge in the western and southern Alps over the last few decades. This is coupled with changing anthropogenic pressures such as an increase in water abstraction for tourism and artificial snow in addition to the water demands of agriculture and hydroelectricity. Water consumption by tourism in winter is several times higher than that of the permanent population. To avoid the development of water shortages with relation to other users, a clear quantification of parameters within the water cycle is necessary. However, measurements of classical hydrological and biological components for model validation are often missing and terrestrial photogrammetry is not yet purposefully applied. An integrated hydrological model is applied to the ski resort of Les Arcs, Bourg-St-Maurice in Savoy, France, taking into account the impacts of artificial snow on torrent discharge under different climatological and anthropogenic scenarios with relation to interbasin water transfer. The classical arguments for the expansion of artificial snow are the necessity of winter tourism to maintain the local and regional economy but no empirical relation exists between snow production and ski frequentation. If the clear trend of increasing temperatures in the mountains continues, less and less reliable snowmaking days will be available and some regions may gradually turn into unprofitable zones depending on wind (e.g. foehn conditions), evaporation, aspect and altitude. New adaptation strategies for diversification of tourism in mountain areas, e.g. through a four seasons approach, have to be developed. Since mountain areas are highly fragile, powerful decision support systems are required to control hydrological modifications and prevent water conflicts. Scientists cooperating with stakeholders will be increasingly confronted with issues such as economical benefits versus environmental impacts. Even before the stage of developing decision support tools with the stakeholders concerned, important work is necessary to develop an interdisciplinary and intersectorial problem consciousness and acceptance. There is an urgent need for sub-scale catchment management plans that take into account local hydrological and economical requirements and conflicts that are linked to, but not overshadowed by large-scale catchment plans.