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Discharge Rates of the Danube River
Ducic, V.  2005.  Reconstruction of the Danube discharge on hydrological station Orsova in pre-instrumental period: Possible causes of fluctuations.  Edition Physical Geography of Serbia 2: 79-100.

What was done
Several researchers have studied the precipitation histories of regions along the Danube River in western Europe and the effects they have on river discharge, with some of them suggesting that an anthropogenic signal is present in the latter decades of the 20th century and is responsible for that period's drier conditions.  In the present study, the author examines these claims by analyzing observed and reconstructed river discharge rates near Orsova, Serbia over the period 1731-1990.

What was learned
Ducic notes that the lowest 5-year discharge value in the pre-instrumental era (period of occurrence: 1831-1835) was practically equal to the lowest 5-year discharge value in the instrumental era (period of occurrence: 1946-1950), and that the driest decade of the entire 260-year period was 1831-1840.  Similarly, the highest 5-year discharge value for the pre-instrumental era (period of occurrence: 1736-1740) was nearly equal to the 5-year maximum discharge value for the instrumental era (period of occurrence: 1876-1880), differing by only 0.7%.  What is more, the discharge rate for the last decade of the record (1981-1990), which prior researchers had claimed was anthropogenically-influenced, was found to be "completely inside the limits of the whole series," in Ducic's words, and only slightly (38 m3s-1 or 0.7%) less than the 260-year mean of 5356 m3s-1.

What it means
Ducic concludes that "modern discharge fluctuations do not point to [a] dominant anthropogenic influence."  In fact, Ducic's correlative analysis suggests that the detected cyclicity in the record could "point to the domination of the influence of solar activity."

Reviewed 3 August 2005