Western Cape Water Supply System

The Western Cape Water Supply System (WCWSS) is a complex water supply system in the Western Cape region of South Africa comprising an inter-linked system of six dams, pipelines, tunnels and distribution networks. Some elements of the system are owned and operated by the Department (Ministry) of Water Affairs and Forestry and some by the City of Cape Town.[1] The principal dams are all located in the Cape Fold Mountains to the east of Cape Town. They are:

In 2009, 63% of the water in the system was being used for domestic and industrial purposes in the city of Cape Town, 5% in smaller towns and 32% in agriculture.[2]

Components

The largest component of the WCWSS is the Riviersonderend Government Water Scheme, which is a large inter-basin water transfer scheme that regulates the flow of the Sonderend River flowing South towards the Indian Ocean, the Berg River flowing North towards the Atlantic Ocean and Eerste River that flows into False Bay.

Its centerpiece is the Theewaterskloof Dam on the Sonderend River, the largest dam in the system with a storage capacity of 480 million cubic meter. It is linked to the Berg River via a tunnel system through the Franschhoek Mountains. During winter, when water requirements are lower, this tunnel system conveys surplus flows from the Berg River Dam and the tributaries of the Berg River to the Theewaterskloof Dam, where the water is stored. In summer, when water requirements are high, water can be released back via the tunnel system into the catchments of the Berg and Eerste River.[2]

Other storage dams of the WCWSS are the Voëlvlei Dam (159 million cubic meters), the Wemmershoek Dam (59 million cubic meter) in the Berg River basin, the Upper and Lower Steenbras Dams on the Steenbras River as well as the Palmiet Pumped Storage Scheme dams on the Palmiet River, from which water can be transferred to the Steenbras dams.[2]

In 2009 storage capacity in the system was increased by 17% from 768 to 898 million cubic metres through the completion of the Berg River Dam.[3]

Agricultural Use

The system also provides water to irrigate about 15,000ha of farmland, where high-value fruit and vegetables are grown. From the early 1970s until the mid-2000s water consumption in Cape Town increased by about 300%, increasing the competition for water with irrigated agriculture. This has been exacerbated by several unusually dry years, such as in 1994-1995 when storage in the system was only one third of average storage. Farmers have adapted by significantly improving irrigation efficiency and shifting even more land into the production of high-value crops.[4]

The system also generates hydropower using an installed capacity of 200 Megawatt (MW) on the Palmiet River and 160MW on the Steenbras River.

Future Developments

It is expected that demand in the area served by the system will exceed supply by 2019, and possibly even earlier if water availability diminishes because of climate change and if water conservation measures in Cape Town should not be as successful as envisaged. A number of additions to the system, such as the heightening of dams, are considered as well as seawater desalination in order to cope with rising demand.[2]

See also

References

  1. ↑ Address by Mr Ronnie Kasrils, MP, minister of Water Affairs and Forestry, at the Berg Water Project signing ceremony on 15 April 2003, in Cape Town, accessed on 11 December 2009
  2. 1 2 3 4 Department of Water Affairs and Forestry:Western Cape Water Reconciliation Strategy, Newsletter 5, March 2009, accessed on 11 December 2009
  3. ↑ City of Cape Town:Cape Town’s water supply boosted, 17 March 2009, accessed on 12 December 2009
  4. ↑ John M. Callaway, Daniel B. Louw and Molly Hellmuth:Benefits and Costs of Measures for Coping with Water and Climate Change:Berg River Basin, South Africa, in: Fulco Ludwig, Pavel Kabat, Henk van Schaik and Michael van der Valk: Climate change adaptation in the water sector, London 2009, p. 205-226
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