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54
Zambezi River runo
Source: SARDC (2008) Southern African Environment Outlook,
SADC, SARDC, IUCN, UNEP, Gaborone/Harare/Nairobi.
1939
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
5
0
10
15
20
25
30
Thousand cubic metres per second
Figure 2.8
Flow Reduction in the Zambezi River Basin due to dam construction.
Reduced Runoff
A major impact of the construction of the Kariba
and Cahora Bassa dams from 1950–1970 was
the reduction in the Zambezi River runoff. Before
the dam construction, the Zambezi River was
torrential with high flows during the wet season
from November to March and relatively low
flows in the dry season from April to October. On
average, the river discharged 60 to 80 per cent
of its mean annual flow during wet season. Since
the dams were built, the wet season runoffs have
been reduced by about 40 per cent, whereas the
After 28 years of aridity, the Savute Channel is flowing again,
bringing an explosive growth of vegetation and drawing
wildlife. The channel flowed from the 1850s to the 1880s, then
stopped flowing and remained dry until it began flowing
again in 1958. It stopped flowing in 1965, started again in 1967
then stopped in 1982, remaining dry for 28 years, until 2010
when water filled the channel again (Pfotenhauer 2011). This
irregular flow of water explains the numerous dead trees that
line the channel, as they have germinated and grown when
the channel was dry and been drowned when it flowed again.
Savute River in Botswana flowing again
The exceedingly high rainfall in the Angolan Highlands
in the 2009-10 rainy season, along with the good
floods of the year before, caused phenomenal
flooding of the Okavango Delta in the winter of
2010, the highest ever recorded. Small tributaries of
the Okavango River flow into the Selinda Spillway,
now also flowing after many dry years. The spillway
connects with the Kwando/Linyanti river system
which, further north and east, flows into the Chobe
River and eventually meets the Zambezi.
dry season runoffs have increased by about
60 per cent (SADC and SARDC 2008).
Changing River Flows
The generally arid southwestern part of the
basin has produced some river flow regimes
that are not consistent with the seasonality of
the rainy and dry seasons. For example, the
Savute River is uncharacteristically dry for long
periods before flowing again, while the Lake
Liambezi almost disappeared between 1985
and 2000 before in began filling up again.
Elephants drinking from the Savute River.
© Candice Bate,
WWF