Cape Town gets most of its water from a group of dams in the mountains east of the city, linked by tunnels and pipes. Together they are called the Western Cape Water Supply System [IC]. The largest of these dams, Theewaterskloof, lies near Villiersdorp in Theewaterskloof Municipality, the same municipality as Ward 2 [IC]. Below the dam, the Riviersonderend flows east past Greyton and Genadendal, and the valley’s own rivers join it [IC]. This page explains how the system works, who gets its water, and why it matters to the valley.
What the letters in square brackets mean
Facts on this page are followed by a tag that shows where they come from.
- [IC] Independently Corroborated. Confirmed by an official record, or by at least two sources that do not depend on each other.
- [MS] Mission-Sourced. Comes from the statements of the organisation the sentence names. It has not been checked against sources that do not depend on it.
- [TBV] To Be Verified. Seems likely, but nobody has confirmed it from a reliable source yet.
Sentences about what the system could mean for the valley carry no tag. They are the Forum’s reading.
The big dams
Six large dams hold almost all the system’s water. Together they store about 898 million cubic metres when full [IC]. Some belong to the national Department of Water and Sanitation and some to the City of Cape Town [IC].
| Dam | Holds when full (million cubic metres) | Where | Owner |
|---|---|---|---|
| Theewaterskloof | 480 [IC] | On the Riviersonderend, near Villiersdorp | Department of Water and Sanitation [IC] |
| Voëlvlei | About 160 to 170 [IC] | Near Gouda, filled by canals from the Klein Berg, Leeu and Vier-en-Twintig rivers [TBV] | Department of Water and Sanitation [IC] |
| Berg River | 130 [TBV] | On the Berg River, near Franschhoek. Finished in 2009 [TBV] | Not confirmed |
| Wemmershoek | 59 [IC] | On the Wemmershoek River, near Franschhoek | City of Cape Town [IC] |
| Steenbras Lower | 34 [IC] | On the Steenbras River, above Gordon’s Bay | City of Cape Town [IC] |
| Steenbras Upper | 32 [IC] | Upstream of Steenbras Lower | City of Cape Town [IC] |
Sources give slightly different sizes for some dams. Voëlvlei differs most: 159, 164 and 172 million cubic metres in three sources [IC].
Theewaterskloof alone holds about half the water of the six big dams: 480 of 898 million cubic metres, or 53% [IC]. One source gives 41% [TBV]. Its earth wall is about 37.5 metres high [IC].
The City also owns eight small dams on Table Mountain, near Simon’s Town and in the Helderberg [IC]. Together they hold less than 5 million cubic metres [IC]. The largest, Kleinplaats Dam near Simon’s Town, holds about 1.4 million [IC].
How Theewaterskloof’s water reaches Cape Town
Theewaterskloof is the heart of the Riviersonderend-Berg River Government Water Scheme, the largest part of the system [IC]. The scheme joins three river basins that run in different directions: the Riviersonderend flows east, the Berg flows north, and the Eerste flows into False Bay [IC].
The scheme has three parts [IC]:
- Theewaterskloof Dam, filled by its own catchment and by winter water brought through the tunnels from rivers near Franschhoek and Stellenbosch.
- A tunnel system through the mountains, including the Franschhoekberg tunnel (12 kilometres) and the Stellenboschberg tunnel (5 kilometres).
- Kleinplaas Dam, a small dam on the Eerste River that controls the flow through the tunnels. It is a different dam from Kleinplaats Dam near Simon’s Town.
In winter, water flows through the tunnels into Theewaterskloof. In summer, water is released back through the tunnels to farmers in the Berg and Eerste valleys, to towns such as Stellenbosch, and to Cape Town [IC]. The Department of Water and Sanitation runs the scheme and plans maintenance on it with the City [MS].
Who gets the water
Theewaterskloof’s water goes two ways [IC]:
- West, through the tunnels, to Cape Town, Stellenbosch and the Helderberg, and to farmers along the Berg and Eerste rivers.
- East, down the Riviersonderend, to farmers along the river and to the Overberg Water Board, which supplies Caledon and other towns.
Two documents give yearly shares of the scheme’s water. An older planning document, written before the Berg River Dam was built, gives rounded figures [IC]. The newest Department of Water and Sanitation report on the system, its Annual Status Report of November 2018, gives what each user was receiving at that time [IC].
| User | Older document (million cubic metres a year) | Department, 2018 (million cubic metres a year) |
|---|---|---|
| Farmers along the Berg River | 49 | 48.6 |
| Farmers along the Riviersonderend (Riviersonderend Irrigation Board) | 31 | 30.8 |
| Paarl and Wellington | 16 | Not listed |
| Vyeboom Irrigation Board (also spelled Vygeboom) and farmers who pump from the dam | 15 | 14.7 (13.2 and 1.5) |
| Stellenbosch Irrigation Board | 10 | 9.7 |
| Helderberg Irrigation Board | 8 | 7.8 |
| Overberg Water Board | 4 | Named, with no figure |
| Farmers along the Eerste River | 3 | 2.8 |
| Banhoek Irrigation Board | 2 | 1.8 |
| Stellenbosch Municipality | Not listed | 3 |
| City of Cape Town | The rest | 118 to the Faure and Blackheath treatment works, and 0 to 23 through a pipeline to Wemmershoek |
The 2018 report takes its diagram of the scheme from a 2006 Department document [IC]. Several of its figures differ very little from the older ones, so some may have been carried over without being measured again.
The same report also lists allocations, the volumes users are entitled to. These can differ from what users receive [IC].
- City of Cape Town: 118 million cubic metres a year from Theewaterskloof. Of this, 90 is a fixed allocation and 28 a temporary one, first lent to the City in 1989 from farming’s share while farmers were not using it [IC]. Since 2003, 10.86 million of farming’s unused share has been licensed to farming projects the report describes as 100% black economic empowerment (BEE) projects [IC].
- Zonderend Irrigation Board, the farmers along the Riviersonderend: 36.1 allocated, against a need of 41.5 [IC].
- Vyeboom Irrigation Board and farmers who pump from the dam: 29.5 allocated [IC].
- Overberg Water Board: 4.0, the figure used in the Department’s planning model [IC].
- All farming in the system: about 198.6 allocated in 2018, up from 162 set in the 2003 agreement for the Berg River Dam [IC].
Across the whole system, farms used about a third of the water and smaller towns about 5% in 2009 [TBV]. The system irrigates about 15,000 hectares of farmland [TBV].
The system is short of water. Provincial and national officials say it is over-allocated: even with full dams there may not be enough for every user [MS]. In the 2018 drought, the farmers along the Riviersonderend received only 60% of their allocation [IC].
Each year the Department reviews the water in the system at an annual operating analysis and decides whether restrictions are needed [MS]. The 2026 review was set for 2 November 2026 [MS].
A new dam planned in the Overberg
The Western Cape Government lists a proposed Overberg Dam among its priority infrastructure projects [IC]. It would hold about 123 million cubic metres on the Breede River near Swellendam, with feasibility studies planned for 2027 and 2028 [MS]. It is planned as a water project for the Overberg District, and nothing published so far links it to Cape Town’s supply [TBV]. See Provincial Pipeline.
Why it matters to the valley
The dam is in our municipality
The dam shares its name with the municipality, and it belongs to the national government [IC]. Decisions about how its water is shared are made by the Department of Water and Sanitation and the Breede-Olifants Catchment Management Agency [MS].
The valley lives downstream
The Gobos River from Greyton and the Baviaans River from Genadendal join the Riviersonderend below the dam [IC]. The water that farmers along the river receive is a mix of what the dam releases and what streams like these add [IC]. The river below the dam also has its own needs, set in law as the Reserve (see National Water Act) [IC].
Cape Town pays for healthy catchments
Since 2018 the Greater Cape Town Water Fund has cleared invasive plants from the mountains that feed Cape Town’s dams [MS]. Since April 2026 the Cape Water bond has paid for part of that work, with a bonus to lenders only when the clearing is checked [IC]. See How the Cape Water Bond Works.
A place-based economy
The Forum reads the system as part of what a place-based economy for the valley could be built on. Cape Town and the farms of the Berg and Overberg depend on water that falls on the same mountains as the valley. Water the valley’s land gives, measured and proved, is something the system already needs. Three ideas tabled at the Forum build on this: From Water Access to Water Agency, Restoring the River, and Ridge to River to Table.
Following the dam levels
- The Department of Water and Sanitation publishes a weekly report on the state of the country’s dams [IC].
- The City of Cape Town publishes its dam levels daily, and a weekly water dashboard [MS].
- Cape Town Dam Levels gathers these figures in one place. Its operator describes it as a personal side project [MS].
What is still open
- Current shares. The newest Department of Water and Sanitation report with yearly shares is from November 2018. No later report with shares has been found, including from the annual operating analysis.
- Overberg Water Board’s share. The 2018 report names the Overberg Water Board as a user below the dam, but gives no current volume for it.
- Sizes and owners. Who owns the Berg River Dam, and which size for Voëlvlei is current.
- Releases for the river. Whether Theewaterskloof releases water to meet the Reserve below the dam today.
- The Overberg Dam. Whether it would ever be joined to this system.
- Maintenance. How often the tunnels are shut for maintenance, and how that affects releases down the Riviersonderend.
Have your say
To correct or add to this page, see How to Submit.
Related
- Department of Water and Sanitation
- City of Cape Town
- Overberg Water Board
- Breede-Olifants Catchment Management Agency
- Greater Cape Town Water Fund
- How the Cape Water Bond Works
- Theewaterskloof Municipality
- Provincial Pipeline
- Greyton’s Leiwater
- Organisations Outside the Valley
References
- Saldanha Bay Municipality. Description and layout of the Western Cape Water Supply System. The parts of the Riviersonderend-Berg River scheme, the users it supplies, their shares, and the size, height and owner of each major dam.
- Department of Water and Sanitation. Support for the Implementation and Maintenance of the Water Reconciliation Strategy for the Western Cape Water Supply System: Annual Status Report (November 2018). Prepared by NFM Multi Consulting/Tlou Consulting with Aurecon. What each user of the scheme received (section 2.1.1), the City of Cape Town’s allocations (Table 4-1) and farming allocations (Table 4-13).
- Department of Water and Sanitation. Reconciliation Strategy for the Western Cape Water Supply System: Reports and Documents. The list of the Department’s status reports on the system, of which November 2018 is the latest.
- Wikipedia. Western Cape Water Supply System. The dams and their sizes, total storage, the share used by farms and towns, and the area irrigated.
- Cape Town Dam Levels. Data sources. Total storage of the six big dams, Theewaterskloof’s share, and where dam level figures come from.
- South African History Online. Theewaterskloof Dam, Villiersdorp. The dam and the tunnel system.
- Department of Water and Sanitation. Misinformation about water from Theewaterskloof Dam (January 2018). Releases down the Riviersonderend and the 60% cut in the drought.
- Eyewitness News. WC DWS to continue monitoring dam levels ahead of key water assessment (14 October 2026). The Department’s annual operating analysis on 2 November 2026.
- Daily Maverick. Water crisis: Western Cape’s declining inland water resources pose challenge (10 November 2024). Officials on over-allocation.
- Western Cape Government. Overberg Dam: Potential Water Security Project in the Overberg District. The proposed Overberg Dam.