Long-term variations and long-range forecast of the runoff of the Neva River

Abstract

The time series of annual values of the Neva River runoff for 1859—2005 was analyzed by the methods of «Periodities». The time interval of 2006—2010 was used for the estimation of the results of training runoff forecasts for these years. The sinusoids with the periods of 29, 11, 8, 13, 149, 5 and 21 years were revealed in the time series of the Neva River runoff. Their values of relative correlation with the time series are larger than 15 %. When the revealed sinusoids were successively summed in order of reduction of their relative correlation with the time series, the relative correlation of their sums and time series was continuously increasing. The relative correlation of sum of all of these sinusoids and the runoff time series has exceeded 70 %. The training forecasts computed by each of these sinusoids, except the 8-year harmonic, are better than the mean value prediction. The results of forecast by the sinusoid with the period of 8-years are almost the same quality as ones made by the mean value. When these sinusoids had been successively summed the results of training forecasts became better. The forecasts computed by the sum of all sinusoids proved true for all years. Sum of their squared errors is more than ten times smaller than that of mean value forecast.