MAPPING OF SNOW COVER AND GLACIERS WITH HIGH RESOLUTION REMOTE SENSING DATA FOR IMPROVED RUNOFF MODELLING

The study presents investigations of the runoff from snow and ice, carried out in the high alpine basin of the Rhone river at Sion (3371 km 2 , 491 -- 4634 m a.s.l.). Using satellite remote sensing data, features like the snow coverage in the whole basin, the gradually decreasing snow coverage on glaciers and the area of exposed ice have been mapped. The periodical monitoring of the basin is based on Landsat-TM data enabling snow and ice areas to be distinguished. The satellite imagery has been geocoded with high accuracy and interpreted using supervised classification techniques. The satellite derived snow and ice coverages were supplied to the snowmelt runoff model SRM+G allowing to compare the different runoff input components: seasonal snow cover, new snow, rain and glacier-ice. Due to the high part of glaciers in the basin (17% glaciered) special attention has been paid to the melt conditions of ice in comparison with the melt conditions of snow. Conditions for a norm year in terms of normalized daily values derived for the time period 1961 to 1990 for snow cover depletion, temperature and precipitation have been established. Based on norm year conditions the effect of climate change was evaluated for the scenarios 2030 and 2100, which are characterized by increasing temperatures during winter and summer and increased precipitation during winter. The results show the influence of increased summer icemelt in the basin Rhone-Sion.