The Sterkfontein Dam, located just outside the town of

Harrismith Harrismith is a large town in the Free State province of South Africa. It was named for Sir Harry Smith, a 19th-century British governor and high commissioner of the Cape Colony. It is situated by the Wilge River, alongside the N3 highway, ab ...

, in the Free State, province of

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

, is part of the Tugela-Vaal Water Project and the

Drakensberg Pumped Storage Scheme The Drakensberg Pumped Storage Scheme is an energy storage facility built in the South African provinces of Free State and KwaZulu-Natal starting in 1974 and completed by 1981. Four dams are involved in the scheme; the Driekloof Dam (''joined ...

, and located on the Nuwejaarspruit, a tributary of the Wilge River in the upper catchment area of the

Vaal River The Vaal River ( ; Khoemana: ) is the largest tributary of the Orange River in South Africa. The river has its source near Breyten in Mpumalanga province, east of Johannesburg and about north of Ermelo and only about from the Indian Ocean. ...

. It is the second highest dam wall in South Africa and its highest earth fill dam.

Background

History

The rapid economic expansion of the greater Johannesburg area in the 1960s and 70s put its water supply under long term threat and it was decided to redirect water from the large

Tugela River The Tugela River ( zu, Thukela; af, Tugelarivier) is the largest river in KwaZulu-Natal Province, South Africa. With a total length of , it is one of the most important rivers of the country. The river originates in Mont-aux-Sources of the D ...

which was going largely un-used into the sea and store it in large strategic water storage reservoir with very low evaporation. The initial site chosen for this project was in the adjacent valley to the west on the Elands River. This was the preferred option from an engineering aspect because it would involve a smaller dam wall. However shortly before construction was about to start the site on the Nuwejaarspruit was selected for political reasons because it avoided the partial flooding of the newly planned

Bantustan A Bantustan (also known as Bantu homeland, black homeland, black state or simply homeland; ) was a territory that the National Party administration of South Africa set aside for black inhabitants of South Africa and South West Africa (now ...

Qwaqwa QwaQwa was a bantustan ("homeland") in the central eastern part of South Africa. It encompassed a very small region of in the east of the former South African province of Orange Free State, bordering Lesotho. Its capital was Phuthaditjhaba. It ...

in Phuthadichaba. It could have meant this strategic national resource could have been located in a "foreign country" which would have been unacceptable as seen from the perspective of the current government in that time.

Construction

Construction began in 1969 and the first phase was commissioned in 1977 and comprised a high earthfill embankment long with no spillway. After completion of the first phase the decision was made to immediately continue with the final phase and it was subsequently raised in 1980 to its current height of with a crest length of and a full supply capacity of . At full supply, it has a surface area of no more than 70 km². The extended dam was commissioned in 1980, and has a capacity of , with a surface area of only , the dam wall is high. The total construction period was 11 years. The Sterkfontein Dam was designed and constructed by the Department of Water Affairs. The dam mainly serves for domestic and industrial use and its hazard potential has been ranked high (3).

Naming

The dam was named after one of the farms located in the vicinity of its construction. The temporary township for the construction workers was built on the Sterkfontein farm. The word ''sterkfontein'' means ''strong spring'' in

Afrikaans Afrikaans (, ) is a West Germanic language that evolved in the Dutch Cape Colony from the Dutch vernacular of Holland proper (i.e., the Hollandic dialect) used by Dutch, French, and German settlers and their enslaved people. Afrikaans gra ...

Characteristics

Earth Fill Dam Wall

The wall is an earth gravity type. The dam wall contains of material making it the largest dam wall in South Africa with regard to volume. The reservoir is impounded by two walls. The second wall is long and contains of material.

No spillway

The dam is unique as the majority of water is sourced by diverting flow from the upper reaches of the Tugela river. This water would otherwise be underutilised and flow into the ocean. The dam was not built on a river but instead, it is sited on what can at best be classed as a large stream in the upper reaches of a valley on the Nuwejaarspruit. The catchment area of the dam is less than three times the water surface area of the dam and therefore not risk to a flood. For this reason the main dam wall does not have the need for a spillway. Any excess rainwater can be safely ejected from its outlet valves. The advantage of this location is the Dam is a highly effective reservoir, since it has the depth to store a large amount of water, with very little loss to evaporation. The Vaal Dam lake (reservoir) by comparison has a large surface area and is relatively shallow, which results in a higher rate of evaporation. It would take 17 years of rainfall to fill the dam. But capturing rainfall was not an important intent behind this project. It was built to capture water from the Tugela river and deliver it into the Vaal system.

Pumped Hydro Storage Scheme

The dam receives its water via the Tugela-Vaal Water Project later renamed the

which is a 1,000 MW pumped hydro storage scheme involving the net transfer of up to of water from KwaZulu-Natal. This is stored in the Sterkfontein Dam and released to the

Vaal Dam The Vaal Dam in South Africa was constructed in 1938 and lies 77 km south of OR Tambo International Airport. The lake behind the dam wall has a surface area of about and is 47 meters deep. The Vaal Dam lies on the Vaal River, which is one ...

via the Wilge River when needed.

A dam within a dam

The Driekloof Dam which is inside the Sterkfontein Dam, is regarded as a separated dam and reservoir, and is not included in the above figures. It is essentially a dam within a dam. Driekloof Dam is the upper storage reservoir of the

. If the Sterkfontein Dam were to be empty the Driekloof reservoir would retain the water for the pumped storage scheme to operate unimpeded. When Sterkfontein Dam is at full capacity the Driekloof Dam is submerged up to the top of its spillway.

Third largest dam in South Africa

This is the 3rd largest dam in South Africa in terms of water capacity and it is slightly larger than Vaal Dam. * Gariep Dam 5,340,600 MegaL * Vanderkloof Dam 3,171,300 MegaL * Sterkfontein Dam 2,616,900 MegaL * Vaal Dam 2,603,400 MegaL

Protected areas

The Sterkfontein Dam Nature Reserve is a protected area located by the dam.Free State Tourism - Sterkfontein Dam Nature Reserve
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Photo gallery

File:Sterkfontein Dam 1st phase artist impression.jpg, Artist's impression of the 1st phase of the Sterkfontein Dam. The final wall was raised to the level of the valve control room at the top of the concrete tower. File:Sterkfontein Dam basin.jpg, A view of the dam basin prior to being covered by water. File:Sterkfonteindaminfo1.JPG, The first of three information boards posted at a vehicle rest area overlooking the reservoir just off the R74. File:Sterkfonteindaminfo2.JPG, The second information board. File:Sterkfonteindaminfo3.JPG, The third information board. File:Sterkfonteindamcampsite.JPG, A campsite with chalets at the water's edge. Note the dry conditions (conducive to bush fires) in the wintertime. File:Sterkfontein Dam camping area.JPG, Camping area at the water's edge. File:Sterkfontein Dam Earth Wall.jpg, The earth wall on the eastern side of the Sterkfontein Dam. File:Earth fill loading D5 Aug 72.jpg, Earth moving equipment dumping fill from the borrow pits for the wall of Sterkfontein Dam. Aug 1972 File:Sterkfontein Dam workshops.jpg, The site workshops for Sterkfontein Dam. The area below the site office is now underwater. File:Sterkfontein Dam construction village.jpg, The construction village at Sterkfontein Dam 1973 File:Sterkfontein Dam site office.jpg, The Department of Water Affairs site office. Sterkfontein Dam 1972 File:Sterkfontein Dam wall construction.jpg, A view of the dam wall of Sterkfontein Dam during construction. In the foreground is resident Engineer David Bell. File:Sterkfontein Dam RE.jpg, David Bell the Resident Engineer of Sterkfontein Dam explaining the works to a journalist. Circa 1974

References

External links

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The weir separating the Driekloof Dam reservoir from the Sterkfontein Dam reservoir.
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Rand Water Rand Water, previously known as the Rand Water Board, is a South African water utility that supplies potable water to the Gauteng province and other areas of the country and is the largest water utility in Africa. The water is drawn from numerous s ...

Department of Water Affairs and Forestry
Dams in South Africa Vaal River Dams completed in 1977 Maluti-a-Phofung