5 Climate Change Impact on Hydrological Regimes …
101
by high inter-annual variability over Southern Africa. The insufficient data records
for southern Africa also make analysis challenging (Mazvimavi 2010a). These limitations render detection of rainfall changes due to climate change difficult. However,
as pointed out by Warburton and Schulze (2005a) changes in rainfall have important implications for the hydrological cycle and for water resources since rainfall
is the main driver of variability in the water balance, upon which humans and the
environment depend. A summary of the results of rainfall analysis is given in Table 2.
4 Occurrence of Water-Related Extreme Events
in Southern Africa
Several studies from southern Africa have shown that extreme hydrological events
are increasing in frequency and magnitude (e.g. Kabat et al. 2002; Reason and Keibel
2004; Kadomura 2005; Patt and Schröter 2008a; Yanda 2010; Goodess 2013). Several
studies show that the El Niño-Southern Oscillations are becoming more intense as
a result of climate change (e.g. McMichael et al. 2006; Collins et al. 2010; Manatsa
and Behera 2013). For example, in Southern Africa, the frequency of droughts is
projected to increase and will most likely increase the frequency of extreme low flows
and low storage episodes (Desanker and Magadza 2001). These will inevitably affect
aquatic ecosystems, water supply, irrigation, leisure, and hydro power generation.
On the other hand, Kusangaya et al. (2014) reported that some areas in southern
Africa have, and will, experience an increase in the frequency and magnitude of
heavy precipitation events which in most cases will result in flooding (and extreme
high flows) (Figs. 2 and 3).
Thus, from other reports (Field et al. 2012) it is observed that (a) Africa has the
second-highest number of extreme events after Asia, and, (b) Africa has the highest
number of hydrological extreme events. A significant number of these hydrological
(e.g. floods) and climatological (e.g. droughts) are occurring in Southern Africa. For
southern Africa countries, it can be seen that (a) the occurrence of natural disasters in
the last two decades (1991–2000 and 2001–2010) is by far higher than for the previous
decades, with the 2001–2010 decade having the highest occurrences (Fig. 2) and (b)
the occurrence of these water-related disasters has been increasing at an exponential
rate. The number of natural disasters in the last decade is in most cases equivalent
to the total number of disasters in the previous 3 decades (Fig. 3). It is therefore
concluded that there is an increasing trend of extreme events in southern Africa
(Kabat et al. 2002; Patt and Schröter 2008b). The classification of extreme waterrelated events used in this chapter was adopted from Centre for Research on the
Epidemiology of Disasters (CRED) (Table 3)
101
by high inter-annual variability over Southern Africa. The insufficient data records
for southern Africa also make analysis challenging (Mazvimavi 2010a). These limitations render detection of rainfall changes due to climate change difficult. However,
as pointed out by Warburton and Schulze (2005a) changes in rainfall have important implications for the hydrological cycle and for water resources since rainfall
is the main driver of variability in the water balance, upon which humans and the
environment depend. A summary of the results of rainfall analysis is given in Table 2.
4 Occurrence of Water-Related Extreme Events
in Southern Africa
Several studies from southern Africa have shown that extreme hydrological events
are increasing in frequency and magnitude (e.g. Kabat et al. 2002; Reason and Keibel
2004; Kadomura 2005; Patt and Schröter 2008a; Yanda 2010; Goodess 2013). Several
studies show that the El Niño-Southern Oscillations are becoming more intense as
a result of climate change (e.g. McMichael et al. 2006; Collins et al. 2010; Manatsa
and Behera 2013). For example, in Southern Africa, the frequency of droughts is
projected to increase and will most likely increase the frequency of extreme low flows
and low storage episodes (Desanker and Magadza 2001). These will inevitably affect
aquatic ecosystems, water supply, irrigation, leisure, and hydro power generation.
On the other hand, Kusangaya et al. (2014) reported that some areas in southern
Africa have, and will, experience an increase in the frequency and magnitude of
heavy precipitation events which in most cases will result in flooding (and extreme
high flows) (Figs. 2 and 3).
Thus, from other reports (Field et al. 2012) it is observed that (a) Africa has the
second-highest number of extreme events after Asia, and, (b) Africa has the highest
number of hydrological extreme events. A significant number of these hydrological
(e.g. floods) and climatological (e.g. droughts) are occurring in Southern Africa. For
southern Africa countries, it can be seen that (a) the occurrence of natural disasters in
the last two decades (1991–2000 and 2001–2010) is by far higher than for the previous
decades, with the 2001–2010 decade having the highest occurrences (Fig. 2) and (b)
the occurrence of these water-related disasters has been increasing at an exponential
rate. The number of natural disasters in the last decade is in most cases equivalent
to the total number of disasters in the previous 3 decades (Fig. 3). It is therefore
concluded that there is an increasing trend of extreme events in southern Africa
(Kabat et al. 2002; Patt and Schröter 2008b). The classification of extreme waterrelated events used in this chapter was adopted from Centre for Research on the
Epidemiology of Disasters (CRED) (Table 3)