Long-term trends and runoff fluctuations of European rivers. climate variability and change—hydrological impacts

Abstract In this paper the occurrence of dry and wet periods for 18 major European rivers during the period 1850–1997 is analysed. Annual discharge series were standardized for three regions: West/Central Europe, East Europe and North Europe, and for the whole of Europe. The statistical analysis of these series did not confirm any long-term increase or decrease in discharge during the last 150 years. Dry cycles of about 13.5 years and 28–29 years were identified. In East Europe the occurrence of the wet and dry cycles are shifted compared to North and West/Central Europe by a few years. Similar periods have been reported in other world rivers (Amazon, Congo) as well as in the Southern Oscillation, North Atlantic Oscillation and Pacific Decadal Oscillation phenomena. The time shift of cycles in different regions is the regularity related to general oceanic and atmospheric circulation. Key words long-term trends; discharge; Europe; natural fluctuation; wet and dry cycle