Vanderkloof Dam is the second largest dam in South Africa, boasting the highest dam wall in the country at 108m with a crest length of 765m. When the dam is full, it stretches a 100km long. Similar to Gariep Dam , it is a composite gravity arch dam containing 1.1 million m3/s of concrete and has a central arch which transitions into a gravity flank on the left bank. Vanderkloof Dam has a capacity of 3171 million cubic metres. The highest peak inflow of 6700 cumec was first experienced during February 1988.
Vanderkloof Dam was originally scheduled to commence at the same time as the Gariep Dam (formally known as the Hendrik Verwoerd Dam), but in October 1967, construction was postponed in accordance with government measures to curb inflation in the national economy.
During 1969, the Cabinet decided to proceed with the project and in 1970 tenders were requested for a second time. The tenders were however considerately higher than had been expected and during March 1971 it was decided that the Department of Water Affairs should undertake the construction work itself. The Vanderkloof Dam was designed by a consortium of local and overseas consultants.
During July 1971 the first construction teams arrived at the site and two years later the first concrete was placed. During August 1973 the river was diverted through a temporary opening in the right flank of the wall and it was then possible to start with the foundation excavations of the river section.
The delay in the construction of the dam meant that the flow of the Orange River could now be controlled by the completed Hendrik Verwoerd Dam. Although this reduced the risk, flooding of the works still occurred during February 1974. This resulted in some 100 000m3/s of silt and sand being deposited in the cofferdam, but no appreciable damage was caused. Further flooding’s occurred later but the works was not delayed.
The dam was finally commissioned in September 1977 and originally named the P.K. le Roux Dam, after a former Minister of Water Affairs who for many years campaigned for the development of the Orange River. Look at the gallery section for more pictures taken during construction.
The Eskom Hydroelectric Power Station, one of only two Hydro Power Stations in South Africa that generates electricity into the Eskom network is situated within the dam wall. Exploratory works and economic considerations indicated that the best position for the machine hall of the power station, where two turbo generators are housed, is in an underground cavern below the dam wall on the left bank of the river. Just over 97 300m3/s of solid rock was removed to create this vast cavern 91.2m long, 24.0m wide and 48.6m high. Staff and services access to the cavern is by way of a tunnel, 164.0m long which surfaces just below the power station’s high-voltage yard. There is also a passenger lift which links the machine hall with the surface ancillary building situated just below the dam wall.
Four gates installed in the wall can discharge up to 8 500 m3/s in total through the flood sluices which are positioned on the left flank of the dam. Water released from the Gariep Dam flows into Vanderkloof Dam where it is either transferred through the Orange/Riet Canal to the Riet River basin or released downstream through two hydro-power generators. The generators can each produce 120 MW of electricity at a discharge of approximately 200 m3/s . The hydro-power plant can therefore provide up to 240 MW of electricity at a flow rate of 400 m3/s .
The power station at Vanderkloof Dam together with the power station at Gariep Dam are coupled to a interconnected distribution network, which means that the plant can be used for supplying peak power demands or act as a standby in the event of sudden failures in other power stations.
The Vanderkloof Dam play a important role in providing water for irrigation to more than 100 000 hectares of productive agricultural land. The dam is also perfect for angling and water related sports including sailing, skiing and windsurfing. Building the dam gave birth to the beautiful town Vanderkloof , popular with holiday makers and travelers.