Zambezi River Basin

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

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.

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