Long-term changes in river temperature and the influence of climatic and hydrological factors

River temperature is an important physical characteristic of water quality, and long-term monitoring in Austria has provided a unique perspective on river temperature changes during the 20th century. Significant rises in annual mean values were apparent and broadly followed changes in air temperature. However, especially in relation to seasonal mean values, trends were influenced by catchment characteristics and contrasts were evident between sites located in a headwater tributary, at the outlet of a catchment with a sizeable lake area, and on the mainstream of the Danube. There is evidence that inter-annual variations in water temperature were influenced by the climate pattern of the North Atlantic Oscillation, especially in the winter months.