Water resources in mountain regions:: a methodological approach to assess the water balance in a highland-lowland-system

Mountains and highlands are typically areas that provide considerable quantities of water, the latter being an important resource for the lowlands. These run-off quantities remain discernible in the superior-scale river systems and significantly contribute to the global water resources. Therefore, mountain regions ought to be given specific consideration with regard to management endeavours. Although well known in principle, details of water resources originating from mountains remain under discussion. A new approach has been introduced, which depicts the water balance of Switzerland in a spatially distributed manner, based on catchments of about 150 km(2). The main feature of this approach is the areal precipitation, which is calculated using run-off, evaporation and storage change of glaciers, instead of being derived from gauged precipitation values. This methodology was selected because measurement and regionalization of precipitation remain subject to large uncertainties in mountainous areas. Subsequently, the view is widened to the European Alps, which, as compared with the surrounding lowlands, contribute considerably higher annual discharge, especially in the summer months. Finally, the focus is put on the hydrological significance of mountains in general. In dry regions, mountains, in particular, are indispensable contributors to the water resources downstream. Copyright (c) 2006 John Wiley & Sons, Ltd.