Geoscience Reference
In-Depth Information
Table 1.
Most severe drought periods for Masindi and Rakai.
Year
Months
Duration
Magnitude
Return period
Rakai
1966
May-Oct.
6
7.778
186
1970-1971
May-Jan.
9
7.417
93
1956
Mar-Nov.
9
6.866
62
1980
Jun-Dec.
7
6.503
47
1948-1949
Sept-Mar.
7
6.288
37
Masindi
1987-1988
Nov-Jul.
9
7.856
159
1986-1987
Jul-Feb.
8
7.013
80
1956
Feb-Nov.
10
6.959
53
1966-1967
Oct-May
8
6.446
40
1963
May-Oct.
6
6.416
32
SPI Drought Plot for Rakai
9
8
7
y = 1.6211Ln(x) + 0.0779
6
5
4
3
2
1
0
1
10
100
1000
Return Period (years)
Fig. 2.
SPI drought plot for Rakai.
The drought volumes were assumed to be from a population of random
events forming a series,
V
1
,
V
2
,
V
3
,...,V
n
,where
n
is the number of drought
occurrences in the study period in order to apply probability concepts to
drought volume analysis. Then a probability distribution was chosen using
the Kolmogorov-Smirnov (KS) goodness of fit test. The KS test confirmed
that the data best fits to the Log normal distribution. This result is similar
to previous drought studies in Uganda.
8
-
10
Since the drought volumes best fitted to the Log normal distribution,
Eq. (8) was used to estimate the return periods. When log-log plots of
drought volumes against return periods where plotted, the relationship in
Fig. 5 was obtained.
