A distributed mass-balance modeling approach is required to assess the impact of future climate scenarios on water availability in glaciated basins. Accurate estimation of water stored within the snow, firn and ice of such basins requires knowledge of the distributed snow and ice mass balance throughout the year. In this study, we estimate the annual mass balance and runoff for Haut Glacier d′Arolla, Switzerland, from 2000 to 2006. Our estimations are based on observed elevation changes from three digital elevation models (DEMs) derived from aerial photographs in September 1999 and 2005, and October 2006. In addition to these estimations, we implement a combined field observation and a distributed mass-balance modeling approach. An energy-balance model driven by meteorological variables from automatic weather stations inside the catchment area, including gravitational snow transport, is run for the period 2005–06. The model results are validated with direct snow water equivalent measurements as well as with runoff measurements. Combining the mass-balance measurements, energy-balance calculations and measured runoff, we estimate the contribution from ice melt to the runoff for this period to be 25–30%, the contribution from snowmelt 50–60% and the contribution from rain 15–25%. Our model results also show that the snow distribution affects both snow and ice melt. It is therefore important for water resources management to understand the distribution of snow in alpine catchments, as it seems to be the controlling factor for the timing of streamflow throughout the year as well as for the total availability of water.