Nnywane Dam
{{Use dmy dates|date=April 2022}}
{{Infobox dam
| name = Nnywane Dam
| name_official =
| image =
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| location_map = Botswana
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| coordinates = {{coord|-25.115399|25.689567|type:landmark|display=inline,title}}
| country = Botswana
| location = South-East District
| purpose = Urban water supply
| status =
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| opening = 1970
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| res_name =
| res_capacity_total = {{convert|2300000|m3}}
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| res_catchment = {{convert|238|km2}}
| res_surface = {{convert|1.65|km2}}
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The Nnywane Dam is a dam on the Nnywane River in Botswana.
The reservoir provides a water supply to Lobatse, a town {{convert|70|km}} south of Gaborone.{{sfn|Mwakikagile|2009|p=65}}
Water from the reservoir may also be transferred to Gaborone if needed.{{sfn|Prommer|2001|p=11}}
Construction
Nnywane Dam is the smallest of the reservoirs managed by the Water Utilities Corporation.{{sfn|Department of Environmental Affairs|2006|p=27}}
The dam was built in 1970 with an earthcore fill structure.
It has a catchment area of {{convert|238|km2}}.
The surface area of the reservoir is {{convert|1.65|km2}}.{{sfn|Water Utilities Corporation|2010}}
The reservoir has a capacity of {{convert|2300000|m3}}.{{sfn|Central Statistics Office|2009|p=3}}
It is fed by the ephemeral Nnywane River, which runs only in the rainy season.{{sfn|De Vrces|Gieske|1990|p=84}}
Below the dam the Nnywane flows into the Ngotwane River, which flows into Ngotwane Dam in South Africa. The Ngotwane then forms the border between Botswana and South Africa before flowing into the Gaborone Dam.{{sfn|Ngwanaamotho|2011}}
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.{{sfn|Department of Environmental Affairs|2006|p=26}}
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.{{sfn|De Vrces|Gieske|1990|p=86}}
Between 1998 and 2008 the percentage of the reservoir's capacity that was filled ranged from 39.1% in 2003 to 100% in 2006.{{sfn|Central Statistics Office|2009|p=4}}
In June 2012, during an exceptionally dry winter, the dam fell to 52% capacity fill.{{sfn|Morewagae|2012}}
References
Citations
{{reflist |colwidth=30em}}
Sources
{{refbegin}}
- {{cite web
|url=http://www.cso.gov.bw/images/stories/Enviro/botswanawater_statisticsreport.pdf
|title=BOTSWANA WATER STATISTICS
|author=Central Statistics Office
|date=October 2009
|access-date=2012-09-18
|url-status=unfit
|archive-url=https://www.webcitation.org/5r28HPAkm?url=http://www.cso.gov.bw/images/stories/Enviro/botswanawater_statisticsreport.pdf
|archive-date=July 7, 2010
}}
- {{cite web |url=http://www.car.org.bw/Documents/Report%20Water%20Accounts%20Botswana.pdf
|title=Water accounts of Botswana (1992-2003)
|author=Department of Environmental Affairs
|date=July 2006
|access-date=2012-09-19}}
- {{cite web |url=http://iahs.info/redbooks/a191/iahs_191_0081.pdf
|work=Regionalization in Hydrology (Proceedings of the Ljubljana Symposium, April 1990).
|publisher=IAHS |year=1990
|title=A simple chloride balance routing method to regionalize groundwater recharge: a case study in semiarid Botswana
|last1=De Vrces|first1=J. J. |last2=Gieske |first2=A.
|access-date=2012-09-18}}
- {{cite journal |url=http://www.mmegi.bw/index.php?sid=31&aid=961&dir=2012/June/Tuesday12
|journal=Mmegi Online
|date=12 June 2012
|title=Severe water shortage looms
|last=Morewagae|first=Isiah
|access-date=2012-09-18}}
- {{cite book |last=Mwakikagile|first=Godfrey|title=Botswana Since Independence
|url=https://books.google.com/books?id=lnJ9cbY9cLEC&pg=PA65|access-date=2012-09-18
|date=2009-10-31|publisher=Godfrey Mwakikagile|isbn=978-0-9802587-8-3}}
- {{cite web |url=http://www.mmegi.bw/index.php?sid=1&aid=350&dir=2011/January/Thursday20
|title=Floods cause chaos
|last=Ngwanaamotho|first=Maranyane |date=20 January 2011
|access-date=2012-09-19 |work=Mmegi Online}}
- {{cite web |url=http://webarchive.iiasa.ac.at/Research/POP/pde/docs/manual.pdf
|title=Botswana, Mozambique, Namibia: Modeling Population and Sustainable Development Challenges in the Era of HIV/AIDS
|last=Prommer|first=Isolde |date=March 2001 |publisher=International Institute for Applied Systems Analysis
|access-date=2012-09-19}}
- {{cite web |url=http://www.wuc.bw/wuc-content.php?cid=107
|title=Dam Parameters
|author=Water Utilities Corporation |year=2010
|access-date=2012-09-19}}
{{refend}}
{{Dams and reservoirs in Botswana}}