a
a
a
I
I
1981/82
\A AlII
1982/83
A AfuA A
1983/84
~ ~ ~ A M~
1984/85
A ~ AMII
MJ A'9~;S6 j
99
1986/87
1988/89
~ ~ ~
1987/88
1989/90
1990/91
~
52
!\ Af
I (
!\11 A A
WEEKS (JULY YO JUNE)
Fig. 8. Pattern of rainfall at Bloemfontein over ten seasons from 1981 to 1991.
20
1
n • 36
Mar.
Oct
1St
Oct.
t
Apr.
/
o
I
/
Dec.
~ I
I
Jan ./
~ 51 /. Oct
0 1
I
I
I
I
0
50
100
150
200
Rainfall episode (mm)
Fig. 9. The relationship between period of inundation resulting and rainfall episode during a continuous period in 1985 and 1986, marked by
points and a line fitted by eye. The months label the positive inundations.
of evaporation, unless reinundation was sufficient to
extend this period. The predicted inundation derived
from this graph for the 198511986 rain year agreed satisfactorily with the actual inundation (Fig. 10) and was
consequently used to calibrate the model for predicting inundation pattern in Bain's Vlei pan over ten rain
seasons. Subsequent verification of this model, using
incomplete data (i.e. from only some of the season's
inundations) from the 198911990 rain season (Fig. 11),
suggests that the model might underestimate period
of inundation, but this was not sufficiently convincing
evidence to necessitate modification of the model.