Effects of Climatic Fluctuations on Runoff Production and Water Resources Management in highly glacierized Alpine Basins

 

Several approaches characterised by different level of complexity have been developed to simulate the dynamics of snow accumulation and ablation phenomena. Similarly, attention has been devoted to the analysis and simulation of runoff produced by melting in high-glacierised areas. Most of the recent studies introduced distributed approaches for modelling ablation, so achieving fair advances in forecast reliability, although they are still affected by a number of limitations, mainly the lack of observations and parameterisation problems. Our aim is to develop and test an ice- and snowmelt model and a routing model, which allow simulating runoff generation from alpine catchments at the basin scale and for predicting the effects of a potential climate change on water resources originating from glacierised areas. The melting model is based on a degree-day approach and tries to improve the basic formulation including spatial variability by means of a spatially variable degree factor and/or an additional albedo index besides temperature. A suitable approach to route the melt water through the glacier internal drainage system up to the outlet will be explored as well. The ice- and snowmelt model will be used coupled to a glacier evolution model to produce a realistic scenario of the mass evolution of the glacier. Both models will be driven by climatic scenarios that describe present and future climate - as historically observed and as predicted by the last generation of Global Circulation Models (GCMs) - in order to estimate the impact of climatic variability on water resources availability. Stochastic downscaling techniques will be used to derive basin scale climatic scenarios from the large-scale predictions of GCMs. The glacier investigated is Haut Glacier d'Arolla, in Valais, Switzerland, a small alpine glacier with an area of approximately 7 km². The data necessary for the development of the models are provided by extensive field campaigns. A meteo station has been installed November 2000 in the proximity of the snout of the glacier, measuring temperature and relative humidity, wind speed and direction, short and long wave, incoming and outgoing, radiation, albedo and precipitation. For model calibration and validation satellite images of the last generation (TERRA / ASTER) will also be used.