Comparison of Modeled Water Input and Measured Discharge Prior to a Release Event: Unteraargletscher, Bernese Alps, Switzerland

A distributed temperature index melt model including potential clear-sky solar radiation was applied to Unteraargletscher, Bernese Alps, Switzerland, to quantify water input to the glacial hydrological system during the ablation season 1999. Model parameters were determined by calibrating calculated melt with ablation measurements. Discharge was measured in the proglacial stream for 18 days until the station was destroyed by an outburst flood. Comparison of modeled melt and measured discharge reveals that routing processes of water through the glacier vary with time as the water is transferred through a dynamic drainage system. Furthermore, an imbalance of water input and output suggests that water was stored in or beneath the glacier during this period. The culminating outburst flood presumably released this en– or subglacially stored water and may be related to a change in the configuration of the glacial drainage system as inferred from measurements of subglacial water pressure.