Variations of mean daily discharge of Danube river at 16 stations

The river discharge is the main source of freshwater for large surface areas. Its deep minima are connected with drought events, while its maxima – with floods. The time series of river discharge consist of significant seasonal variations, modulated by long-term oscillations. The seasonal, interannual and decadal cycles of Danube river discharge are studied by time series of mean daily data from 16 stations. The data from Orsova station started in 1840. Three stations started in 1900, and the rest – in 20s of the last century. Time series of maximal discharge and seasonal amplitude are created. Their variations in narrow frequency bands are analyzed by the Method of Partial Fourier Approximation (PFA) and compared with the corresponding cycles of the solar activity. The amplitudes of seasonal harmonics from the PFA are compared for all stations. The time delay of the 11-year solar signals to the reaction of river discharge at used stations, are determined from the phase differences. Possible forecast of periods with maximal river discharge on the base of solar cycles is discussed.