Distributed Mapping of Snow and Glaciers
for Improved Runoff Modeling
Jesko Schaper1, Jaroslaw Martinec1, and Klaus Seidel1
Runoff in glacierized alpine basins results largely from glacier ice and from seasonal snowcover. In
general, snowmelt starts with melting the upper snow layers; the main runoff does not results until
the whole snowpack is saturated with moisture. Glacier ice shows a completely different behavior:
as soon as bare ice becomes exposed, runoff results. Considering time and behavior of melting, we
aim at a separate simulation of snowmelt and glaciermelt runoff.
The condition in our approach for distributed runoff calculation is a distributed mapping of snow-
and ice-covered areas. Due to high resolution satellite sensors, it was possible to map snow-covered
and ice-covered areas in the basin of Massa-Blatten, 196 km (14474191 m a.s.l.). Depletion curves
of snow-covered areas were derived in six elevation zones. In addition, the date was determined
when the glaciers' ice became exposed. Melt depths were computed separately based on experimen-
tal 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 hitherto snow-free area, rain, and glacier ice. In order to evaluate the effect of the
refined snow and glacier mapping on detailed melt computations, the runoff was computed resulting
from i) the conventional runoff simulation based on integral snow and glacier areas and from ii) an
advanced simulation taking into account the individual contributions from snow cover and glacier
melt. A significant improvement of the accuracy of the runoff simulation was achieved.
1 Communication Technology Lab, Image Science Group, Swiss Federal Institute of Technology ETH, Glori-
astrasse 35, 8092 Zurich, Switzerland