Natural precipitation cycles were delineated using a natural
breaks classification method, where precipitation data were grouped
visually and logically in a heuristic manner. The most important aspect
of the heuristic natural breaks classification was to minimize
value differences between data within the same class and to maximize
the value differences between the classes (Slocum, 1999). Natural
breaks were assigned by examining the visible troughs or breaks
in the precipitation time series. The main disadvantage of this method
is its subjectivity; class thresholds may vary from one researcher
to the other due to the subjective nature of the classification
(Slocum, 1999). Slight troughs in the precipitation time series can
be ambiguous and may produce poorly defined class boundaries.
Natural breaks were identified in the precipitation accumulation
data by identifying the peak precipitation accumulation and the
trough of the attenuation stage (Fig. 3).