Meltwater from rock glaciers, frozen landforms of debris and ice, has gained attention in dry mountain regions. We estimated how much ice melts in Murtèl rock glacier (Swiss Alps) based on belowground heat flow measurements and observations of the rising and falling ground-ice table. We found seasonal aggradation and melt of 150–300 mm w.e. (20 %–40 % of the snowpack). The ice (largely sourced from refrozen snowmelt) melts in hot summer periods, infiltrates, and recharges groundwater.