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Over the years, the Zambezi River Basin has slightly
become warmer, while the frequency of floods
and droughts has increased. These environmental
changes are partly blamed for land degradation,
habitat changes and drying or inundation of
important ecosystems such as wetlands.
Temperature
The Fourth Assessment Report of the IPCC states
that global greenhouse gas emissions due to
human activities grew by 70 per cent between
1970 and 2004 (IPCC 2009). The emission of
greenhouse gases in one regionmay result in
a temperature rise, with associated effects, in
another region. Thus the high rate of greenhouse
gas emissions across the world is partly the
cause of the temperature rise of at least 0.5
°
C in
southern Africa over the past century. Partly as a
result of this temperature increase, the 1990s were
the warmest and driest years in the Zambezi basin
in recent times (SARDC and HBS 2010).
Floods
Over the last two decades, the Zambezi River Basin
has experienced extreme floods and droughts
(SARDC and HBS 2010). Most of the flooding in
the basin is associated with active cyclones that
develop in the Indian Ocean. The IPCC predicted
that tropical cyclones will become more intense,
with higher peak wind speeds and heavier
precipitation associated with increases in tropical
sea surface temperature (IPCC 2009). Major floods
were recorded in parts of the Zambezi basin
during the rainfall seasons of 1999-2000, 2005-06
and 2007 (SARDC and HBS 2010).
While flooding in some areas, such as the
Barotse plains, is a regular event providing vital
water for irrigation and replenishing soil fertility,
the frequency, timing, intensity and duration
of floods are changing in the basin (SARDC and
HBS 2010). The extent of flooding has intensfied
due to poorly maintained embankments and
structural measures, while in urban areas poor
land use planning and inadequate drainage
worsen flooding. In addition to destruction of
homes and infrastructure, and loss of crops
and livestock, flooding also inundates land,
decreases soil fertility and destroys fodder
resources, limiting agricutural production.
NAMIBIA
ANGOLA
BOTSWANA
ZAMBIA
ZIMBABWE
MOZAMBIQUE
TANZANIA
MALAWI
DEMOCRATIC REPUBLIC
OF CONGO
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Zambezi River Basin flood areas
Area flooded between 1997 and 2007
Sources: SADC and ZRA 2007. Rapid Assessment Report: IntegratedWater Resources
Management Strategy for the Zambezi River Basin. SADCWater Division. Gaborone
Figure 2.5
Figure 2.4
23.0
24.0
25.0
26.0
27.0
28.0
29.0
30.0
Percentage of total land mass
Source:SARDCandHBS2010
Annual Mean Temperature Changes for Kariba
1970 1975 1980 1985 1990 1995 2000 2005 2008
Environmental Dynamics
© Ara Zambeze