Seasonal variations of water temperature and discharge in rivers draining ice-free and partially-glacierized Alpine basins

Records of discharge and temperature of water in rivers draining from 3 Alpine basins between ice-free and 66% glacier-covered, in the upper Aare and Rhone catchments, Switzerland, were examined in order to assess the impacts of percentage glacierisation of large basins on runoff regime and seasonal pattern of river water temperature. The month with maximum runoff is delayed from May for the ice-free Allenbach to July and August for the ice-melt dominated Lonza and Massa. Ice-melt contributions to runoff suppressed water temperatures in summer in the two glacier-fed rivers, but a distinctive seasonal temperature regime was observed only in the Massa, draining the most highly-glacierised basin. Maximum water temperature in the Massa occurred at low flow in April. Subsequently as icemelt discharge increased, water temperature decreased and mean monthly temperature was maintained at about the same level between July and September.