Long Range Streamflow and World Continental Runoff Fluctuations Since the Beginning of this Century

Abstract

Fifty major rivers, distributed all around the world, have been selected and since the beginning of this century their mean annual discharge fluctuations have been studied by filtering methods. The great hydroclimatic periods which have affected the different drainage basins were determined. The succession of dry and humid periods were compared at both regional and continental scales. Lags, oppositions, attenuations or correspondences between the hydroclimatic periods in the different drainage basins are distinguished. The runoff fluctuations of each continent were reconstituted using the discharge fluctuations of some selected and representative rivers. Thus, the world continental runoff fluctuations were calculated by summing the fluctuations of the different continent runoffs. The world continental runoff is greatly influenced by the Asiatic Continent. Furthermore, North American and European runoffs fluctuate in opposition while South American and African runoffs present synchronous fluctuations. The global runoff has been fluctuating but as an average has only increased about 3% during the last 65 years (1910-1975). The humid years seem to be centered around 1915, 1927, 1950, 1960 and 1972. On the contrary , the dry periods seem to be located around 1920, 1940, 1955 and 1965