Assessment of localized seasonal precipitation variability
in the upper middle catchment of the Olifants River basin
German K. Nkhonjera, Megersa O. Dinka and Yali E. Woyessa
ABSTRACT
This study used the Soil and Water Assessment Tool (SWAT) model together with regional climate
downscaled (RCD) data from the CORDEX (Africa project), to assess the local seasonal precipitation
variability in the upper middle catchment (UMC) of the Olifants River basin. The study results, based
on two scenarios (RCP4.5 and RCP8.5), showed a wider monthly and seasonal variability of
precipitation. The study also indicated a strong decreasing trend of east-to-west direction of spatial
precipitation, with most precipitation concentrated in the eastern part of the study area. Within the
western part of the UMC, we also noted another decreasing trend of precipitation from south-to-
north with northern areas of the study area receiving the least amount of precipitation. This study
has also revealed a considerable general reduction of future seasonal precipitation especially in the
mid-term period (2021–2050). The general reduction in future seasonal precipitation, combined with
the increasing temperatures in the area, may exacerbate the drought conditions and reduction in
streamflow of the main river (Olifants) and its tributaries, consequently having a negative impact on
the economic activities in the basin.
German K. Nkhonjera (corresponding author)
Megersa O. Dinka
School of Civil Engineering and Built Environment,
Civil Engineering Department,
University of Johannesburg,
P.O. Box 524, Auckland Park, 2006,
South Africa
E-mail: germann@uj.ac.za
Yali E. Woyessa
Department of Civil Engineering,
Central University of Technology,
Free State,
South Africa
Key words | Africa, climate change, Olifants River basin, precipitation variability
INTRODUCTION
Climate variability coupled with the understanding of cli-
mate change is vitally important as such changes have the
potential to exacerbate the existing threats to human secur-
ity including water, food, health, and economic insecurity,
all of which are of particular concern for the continent of
Africa. The impact of climate change on different sectors
of life on the continent have been studied and documented
rather extensively in the last few decades. Most studies
(Vermuelen et al. ; Ziervogel et al. ; Davies et al.
; Madzwamuse ; Schilling et al. ; Niang et al.
; Warnatzsch & Reay ) identify Africa as one of
the most vulnerable regions to future climate change due
to its high exposure and low adaptive capacity. In fact,
Moges () argues that, many areas in Africa are already
recognized as vulnerably exposed to climate change impacts
also because of having climates that are among the most
variable in the world both on seasonal and decadal time
scales. Although most scientists say single weather events
cannot be attributed to climate change, they, however,
agree on the fact that climate change is responsible for
most of these extreme rainfalls and storms, frequent heat-
waves, shrinking harvests, and worsening water shortages
in Africa and around the world (Reuters ).
The woes of climate change are that while one part of
the continent is suffering from extreme floods, like the
recent Mozambican floods (Cyclone Idai), other parts are
languishing at the other extreme of these weather events,
such as extreme droughts (UNFCCC ). According to
the same report, one-third of people in Africa are already
living in drought-prone areas while 220 million are being
1 © IWA Publishing 2020 Journal of Water and Climate Change | in press | 2020
doi: 10.2166/wcc.2020.187
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