TOPOGRAPHY AND THE WATER CYCLE IN A TEMPERATE MIDDLE MOUNTAIN ENVIRONMENT - THE NEED FOR INTERDISCIPLINARY EXPERIMENTS

Two main characteristics of mountainous regions are the large topography-driven lateral redistributions of water and energy, and the considerable topography-related heterogeneities on all scales, These features are difficult to estimate, to incorporate into hydrologic models and to aggregate on the general circulation model grid scale. On the local scale, the topography controls the spatial patterns of water and energy inputs, soil water properties and soil moisture. On the massif scale, the topography induces climatic and ecological gradients that influence the patterns of parameters and fluxes. This is illustrated by results obtained in the Ringelbach and Fecht research catchments of the Vosges massif, France. A better understanding of the water cycle in mountains requires specific interdisciplinary field experiments, as part of international programmes such as WCRP-GEWEX, IGBP-BAHC and UNESCO-IHP, using a combination of altitudinal transects and nested catchments, and including a long-term component, which is necessary for model validation. Some of the specific scientific and methodological problems that remain to be solved for these regions are given. A west-east transect across the southern part of the Vosges massif and the Rhine graben could provide a convenient site for such an experiment in a temperate middle mountain environment.