Spatial and Temporal Variability Analysis in Rainfall Using Standardized Precipitation Index for the Fuhe Basin, China - Intelligent Computing for Sustainable Energy and Environment - page 457

Fig. 8. Daily average drought and flood frequency fluctuations by using the SPI-10
days with a total of 39 years average from Jan. 1, 1970-Dec. 31, 2008 in the Fuhe basin
compared to the average year precipitation and the difference may be caused by
the maximum rainfall season in the months of April-June. During these periods,
the water leads to a strong water surface and uplifts the Fu river level. However,
when the month of July arrived, the river basin water is close to its saturation,
although the precipitation has sharply dropped. Moreover, if the rainfall slightly
increases, then flood occurs and the phenomenon would lead to a number of
floods that is more than that of droughts in the following several months.
4.3 Days Trends and Analysis
The precipitation information of temporal and spatial can further be refined
to specific days. In fact, the daily time and spatial rainfall distributions can
be regarded as a map of the rain of the Fuhe basin, which can guide other
production activities. Fig. 7 shows the average daily rainfall distribution. It can
be seen that the overall daily rainfall distribution is quite uneven, and the largest
daily rainfall exists in the 167-th day of 16.082 mm , whereas at the beginning
and at the end of the year, the precipitation has reached its lowest point close
to 0.5 mm . On the other hand, the amount of rainfall is not proportional to the
precipitation spatial fluctuations.
Fig. 8 depicts the spatial average daily rainfall changes relative to the rain-
fall mean. The frequency of the abnormal rainfall is fluctuating around 30%.
However, the rainfall fluctuations around the 146-th day show a downward slope
which reaches the normal frequency at its lowest point as shown in Fig. 8B.
Note that the normal precipitation frequency is only about 60% and the flood
and the drought appear continuously during the period and the extreme droughts
and floods outbreak frequently. These phenomena can be also found during the
300th-330th days, as shown in Fig. 8C. In addition, one can observe that the
extremely dry and the wet occur frequently in the 10th-200th days, namely the