The Nnywane Dam is a dam on the
Nnywane River in
Botswana
Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label= Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kalaha ...
.
The reservoir provides a water supply to
Lobatse
Lobatse is a town in south-eastern Botswana, 70 kilometres south of the capital Gaborone, situated in a valley running north towards Gaborone and close to the border with South Africa. Lobatse has a population of 29,772 as of 2022. The town is an ...
, a town south of
Gaborone
Gaborone ( , , ) is the capital and largest city of Botswana with a population of 246,325 based on the 2022 census, about 10% of the total population of Botswana. Its agglomeration is home to 421,907 inhabitants at the 2011 census.
Gaboron ...
.
Water from the reservoir may also be transferred to Gaborone if needed.
Construction
Nnywane Dam is the smallest of the reservoirs managed by the
Water Utilities Corporation.
The dam was built in 1970 with an earthcore fill structure.
It has a catchment area of .
The surface area of the reservoir is .
The reservoir has a capacity of .
It is fed by the ephemeral Nnywane River, which runs only in the rainy season.
Below the dam the Nnywane flows into the
Ngotwane River
The Notwane River (or Ngotwane River) is a river in southeastern Botswana.
Certain sections of its course form the international boundary with South Africa. Its mouth is at the head of the Limpopo River. It has a catchment area of 18,053 square k ...
, which flows into
Ngotwane Dam
Ngotwane Dam is an earth-fill type dam located on the Ngotwane River, near Lobathleng, North West, South Africa. It was established in 1982 and serves primarily for irrigation purposes. The hazard potential of the dam has been ranked significant ...
in South Africa. The Ngotwane then forms the border between Botswana and South Africa before flowing into the
Gaborone Dam
The Gaborone Dam is a dam on the Notwane River in Botswana with a capacity of .
The dam is operated by the Water Utilities Corporation, and supplies water to the capital city of Gaborone.
Location
The Gaborone Dam is located south of Gaborone ...
.
Supply fluctuations
Due to the hot, dry climate, about 2.3% of the stored water in Nnywane Dam is lost through evaporation in a typical year.
Rainfall is unreliable. The 1978–79 rainy season was the start of a dry spell. The reservoir was depleted in 1982 and the public water supply forced to shift to pumping groundwater.
Between 1998 and 2008 the percentage of the reservoir's capacity that was filled ranged from 39.1% in 2003 to 100% in 2006.
In June 2012, during an exceptionally dry winter, the dam fell to 52% capacity fill.
References
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{{Dams and reservoirs in Botswana
Reservoirs and dams in Botswana
Dams completed in 1970
Earth-filled dams
Dams in Botswana