Study of surfaces water hydrology with application to river nile natural flows forecasting via spectrum analysis

The River Nile natural flows time series (monthly aswell as annual ) at main nine gauging stations are analysedusing both the discrete and the continuous spectrum analysis.In the case of the continuous spectrum analysis, twosmoothing filters (Hanning and Tukey) are used. Not only thestructure of the series but also the hidden periodicities areinvestigated. The periodicities of the natural flows seriesare found to be of complex nature. The main periodicities arefound to be the same in many series in both cases of thediscrete and the continuous spectrum analysis. Thecontributions of the trend, the periodic and the stochasticcomponents of the entire series of the nine stations to thetotal explained variance are calculated. The explainedvariance are found to be dominant during the flood periods,while the contribution of the trend is very small compared toother months.Also, the logrithmic transformed data at Aswan stationare analysed using both techniques. The main periodicitiesare found to be the same as that of the original data in caseof discrete spectrum and differ slightly, especially in itsorder, in case of the continuous spectrum.