Ice Reservoir

Abstract

In the alpine regions of the Danube drainage basin, glaciers play a key role in the water balance of the headwater regions. They not only contain an important reservoir of freshwater, but they also have a regulating effect on run-off in alpine rivers. To calculate ice melt in a numerical model, information about surface topography and ice thickness must be provided at the highest possible resolution. Ninety-two percent of the glaciers within the Upper Danube have surface areas that are smaller than the 1 × 1 km²-grid (proxel) used for DANUBIA, and these glacial areas’ basin can be subdivided into 556 subareas, which are distributed over 1,196 proxels within the limits of the DANUBIA model.

For each proxel, an area-altitude distribution was prepared using the available digital glacial boundaries and a high-resolution digital elevation model from the glacial inventory of Austria, the Swiss glacier inventory and the Bavarian Glacier project. Additional for each partial area value for the thickness of the ice in the year 2000 was determined either by measurements or by estimation.

In Map 12.1, the water equivalent of the entire ice mass is calculated for the area of a proxel and distributed evenly across the area. The values are thus directly comparable to other hydrological variables such as the total annual precipitation or discharge rate. The value for the potential meltwater contribution distributed across the entire drainage basin of 213 mm is approximately comparable to the precipitation in the basin for the two summer months.