November 2013
58
Monitoring the drought
in the North West Province
Focus on water and energy
JOHAN MALHERBE, ARC-INSTITUTE FOR SOIL, CLIMATE AND WATER
The North West Province has recently been declared as drought stricken
under the Disaster Management Act. Emergency relief interventions in-
clude financial assistance to commercial and subsistence producers and
the provision of water to communities where water scarcity is becoming
a critical health factor.
Following several wet years from 2008 to 2011 over the South African
interior, it is becoming apparent that adverse weather conditions during
a period of at least two years are starting to have significant agricultural
and hydrological impacts over the central parts of the country.
The ARC-Institute for Soil, Climate and Water (ARC-ISCW) monitors
climatic conditions and vegetation responses operationally over South
Africa. It provides processed near real time monitoring information,
packaged for agricultural applications, to the Department of Agriculture,
Forestry and Fisheries (DAFF) through the National Agro Meteorological
Committee and the Crop Estimates Committee.
It also disseminates information to a wider range of interested parties
through a monthly
Umlindi
newsletter, workshops and on an ad hoc basis
at specific requests from clients. Monitoring for agriculture is made
possible firstly by the timely acquisition of meteorological data from a
network of automatic weather stations operated by the ARC-ISCW, spe-
cifically located to support the needs of the agricultural community.
Data from the network is used at near real time in a Geographical Infor-
mation System (GIS) environment towards monitoring at a wide range
of scales. Secondly, an archive of remotely sensed data from a range of
satellites, updated routinely, provides valuable information regarding the
responses of vegetation to climatic conditions as well as conditions rela-
tive to other periods or a long-term mean. The intensity and extent of the
current drought conditions are well captured by the dataset.
While the 2012/2013 drought over the North West Province will certainly
not count as one of the most extensive droughts over South Africa during
the last century, the persistence of relatively dry conditions over at least a
two-year period has led to severe impacts, as noted from the declaration
of the province as drought stricken.
It was especially during the January 2013 to March 2013 period, that hot
and dry spells had a devastating effect on crop cultivation. While the
eastern parts of the country recorded high rainfall totals during much of
the early to middle part of the summer rainfall season, significant rainfall
events over the central to western parts of the North West Province were
few and far between.
The result was a large negative impact not only on crop cultivation, but
also on grazing. Another exacerbating factor is the persistence of the dry
conditions. The 2011/2012 summer was also dry over much of central
South Africa and the cumulative effect of two dry summer seasons in a
row, has resulted in a large negative impact on both the levels of reser-
voirs and groundwater.
Even though more rain occurred over some parts of the western
Free State and North West during the summer of 2012/2013 than in
2011/2012, the effects of the dry conditions during late summer 2011/2012
were, to some extent, alleviated by residual moisture from the multi-year
wet period of 2008 - 2011.
The Standardised Precipitation Index (SPI - McKee
et al
., 1993) was
developed to quantify precipitation deficits on different time scales.
Apart from providing 1 km resolution indications of wet and dry condi-
tions across South Africa, the rainfall grids created operationally at the
ARC-ISCW are also summarised to quaternary river catchments and the
Figure 1: Drought severity according to the Standardised Precipitation
Index (SPI). From top to bottom, the index was calculated for one, three, six,
twelve and 24 month periods ending in March (one, three and six month SPI)
or June (twelve and 24 month SPI) 2013.
