  We use some fractal analysis methods to study river flow fluctuations.
  The result of the Multifractal Detrended Fluctuation Analysis (MF-DFA) shows
that there are two crossover timescales at $s_{1\times}\sim12$ and
$s_{2\times}\sim130$ months in the fluctuation function. We discuss how the
existence of the crossover timescales are related to a sinusoidal trend. The
first crossover is due to the seasonal trend and the value of second ones is
approximately equal to the well known cycle of sun activity. Using Fourier
detrended fluctuation analysis, the sinusoidal trend is eliminated. The value
of Hurst exponent of the runoff water of rivers without the sinusoidal trend
shows a long range correlation behavior. For the Daugava river the value of
Hurst exponent is $0.52\pm0.01$ and also we find that these fluctuations have
multifractal nature. Comparing the MF-DFA results for the remaining data set of
Daugava river to those for shuffled and surrogate series, we conclude that its
multifractal nature is almost entirely due to the broadness of probability
density function.
