Civil Engineering June 2022 | Vol 30 No 5

54 June 2022 Civil Engineering Thereafter, the dam proceeded to completion in 1977 which, together with the 240 MW power turbines providing electricity generation into the national grid, the right bank canal providing ir- rigation downstream for 81 km towards Hopetown, and further enhanced management of the Orange River flooding potential, brought this phase of the pro- ject to a conclusion. Key characteristics of Vanderkloof Dam include: Q Q Height of 108 m Q Q Crest length of 756 m Q Q Storage capacity of 3 187 million m 3 Q Q Reservoir surface area of 133 km 2 when full. BENEFITS OF THE SCHEME In a restatement of the original objectives, the project was intended to embrace the irrigation of available arable land, urban water supply, industrial water supply, lim- ited hydro-electric power development, and flood control for the entire region comprising the Northern and Eastern Cape and southern Free State. Regarding irrigation of arable land, the entire Great Fish River has become a perennial stream, serving the needs of agriculture throughout its reach to the Indian Ocean. By way of the Cookhouse Tunnel and associated canals constructed by DWA in a subsequent phase, sustained irrigation has been extended into the lower Sundays River, serving the needs of highly-profitable agriculture in this catchment. Subsequent expansion of the scheme downstream from Vanderkloof Dam by DWA, including a pumping station and canal systems, has provided sustainable agriculture for the previously constrained Riet River Irrigation Scheme and along the middle reaches of the Orange River. As regards domestic and industrial water supply, the cities of Gceberha and Kariega (previously Port Elizabeth and Uitenhage) have been adequately sustained by Orange River water during recent years of severe drought and constrained supply from their sur- rounding Eastern Cape dams. A small town such as Steynsburg in the upper Great Fish catchment, sorely constrained by drought, has been relieved by direct pumping from the underground facilities at Teebus. In respect of power generation, the contribution to the national grid has been a small but important component, in addition to use of the machines as synchronous condensers to stabilise the operation of the long 400 kV power line that feeds the Western Cape from the Highveld, thereby reducing the power losses in transmission. Enhanced management of the Gariep and Vanderkloof Dams has finally had a significant impact on flood control through the entire Orange River and will continue to play an important function in water resources management in the coming years of potentially negative impacts of climate change. While much can be said about the benefits of the scheme, it can also be concluded that, where later phases of the great 1960s vision were not imple- mented, notably the Conway Canal and Wapadsberg Tunnel from the Teebus sur- face distribution works to feed the Upper Sundays River and Graaff-Reinet, great hardship has been and will continue to be sorely felt for decades to come and place those communities at great and continual risk of ongoing distress.  Figure 5 Vanderkloof Dam in November 2021 on the brink of spilling