November 2013
60
Focus on water and energy
Continued from page 59
Figure 3: Rainfall deciles for the six month period of October 2012 to March 2013.
Namibia and south western Angola fell within the lowest 20% (shown in
red) experienced during October - March since 1983.
The areas indicated to have been negatively affected during the 2013
summer are very much reliant on the activity of the so-called Angola Low
for precipitation. This system provides ample amounts of tropical mois-
ture to much of southern Africa during wet mid- to late summers, but
from the rainfall experienced during the summer 2012/2013 it is evident
that the Angola Low may have been weakened or displaced somewhat
from its normal position over southern Angola.
While there was no strong El Niño event during 2012/2013, circulation pat-
terns over southern Africa and the Indian Ocean during January - March
were less favourable for precipitation over the sub-continent than on
average during the preceding 15 years.
Average pressures towards the east of the subcontinent were some-
what lower than normal, resulting in weaker subtropical easterlies into
southern Africa and less moisture moving into the interior. While a single
tropical low pressure system was responsible for widespread rain and
flooding over the north eastern parts of South Africa during mid-January,
significant rain was generally confined to areas to the north of the North
West Province.
The persistence of the drought conditions has had impacts ranging
across the agricultural and hydrological sectors of the North West Prov-
ince. Financial losses in the agricultural sector are in the order of billions
of rands.
Maize, groundnut and soybean total production during 2012/2013 were
all down between 40% - 50% year-on-year since 2011/2012, which was
already a summer during which production was negatively impacted by
dry conditions.
Producers have been forced to lower their prices and sell off livestock.
The levels of medium to large reservoirs have dropped to only 10% - 50%
over the central and western parts of the North West Province, with the
levels of small dams reaching critical values, indicating that further com-
plications will develop over the next few months – at least until wide-
spread significant rain can alleviate the situation.
The drought over the North West Province and surrounding area has
highlighted several key points (also in the South African context):
Drought is a creeping phenomenon. Its development over the North
West Province during the past two years happened without any sig-
nificant events announcing the worsening conditions. Operational
monitoring of rainfall and vegetation conditions play a key role in
the early identification of potential disaster areas. Collecting and
archiving such data must remain a priority, whilst communication of
derived products to decision-makers needs to happen on a regular
basis.
South Africa is a drought prone country. It has been many years since
the last big multi-year droughts of the 1960s, 1980s and 1990s. Agri-
cultural resources (such as grazing) need to be utilised sustainably,
while resilience needs to be built up to cope with conditions even
worse than in the current drought. The relatively wet conditions over
the last couple of years have set the scene for a large-scale disaster
should there be a recurrence of the droughts that happened during
earlier decades. Furthermore, drought relief schemes need to remain
sensitive to management practices and encourage the correct utilisa-
tion of resources, whilst discouraging unsustainable practices, such
as high stocking rates.
The science of seasonal forecasting is continually being improved.
While ENSO plays an important role in the context of South African
climate variability, research into other factors influencing rainfall over
the sub-continent at seasonal to decadal scale, can still contribute
positively and increase potential benefits for agriculture.
For more information, contact Johan Malherbe at 012 310 2577 or
johan@
arc.agric.za.
Reference
McKee, T.B., Doesken, N.J., Kliest, J. 1993. The relationship of drought frequency and dura-
tion to time scales. In: Proceedings of the 8th Conference on Applied Climatology, 17 - 22
January, Anaheim, CA. American Meteorological Society: Boston, MA; 179 - 184.
Monitoring the drought
in the North West Province
