Distributed mapping of snow and glaciers for improved runoff modelling

Runoff in glacierized alpine basins results from both seasonal snow cover and glacier melt. In this paper we present a case study for an improved runoff modelling of the basin Massa-Blatten, 196 km 2 , 1447-4191 m a.s.l. Using high resolution satellite sensors, it is possible to separately map snow cover and glacier areas. From the satellite data we derive depletion curves of snow covered areas in six elevation zones and determine when the glacier ice becomes exposed. We compute melt depths based on experimental measurements with regard to snow and ice. With the use of the snowmelt runoff model SRM-ETH, the following input components to runoff were determined: seasonal snow cover, including new snow falling on the snow covered areas; new snow falling on the snow-free area; rain; and glacier-ice. In order to evaluate the effect of the refined snow and glacier mapping on detailed melt computations, we compute the runoff resulting from i) the conventional runoff simulation based on integral snow and glacier areas, and ii) and advanced simulation taking into account the individual contributions from snow cover and glacier melt. We achieve a significant improvement of the accuracy of the runoff simulation.