---
title: cape town drinks six dams
canonical_url: https://ensurance.app/guide/what-cape-town-depends-on
markdown_url: https://ensurance.app/guide/what-cape-town-depends-on.md
subtitle: the tap is a winter-rainfall catchment. the city is the door
category: ecosystem-services
---

# cape town drinks six dams

*the tap is a winter-rainfall catchment. the city is the door*

Someone searching for Cape Town water is usually asking a practical question: what comes out of the tap, and will it keep coming. The answer is not a plant inside the city. It is six dams east of the municipal boundary, filled by winter rain that falls on fynbos catchments. The city is the door into that system. The living system is the shrubland under the rain.

The City of Cape Town says the Western Cape Water Supply System supplies more than 95% of the water it provides. That sentence is from the June 2026 water outlook, not from a slogan. Census 2022 counted 4,772,846 people and 1,452,845 households in the metro. The City's own IDP still prints a 4.68 million figure, and that figure is the 2021 mid-year estimate. The two numbers are not interchangeable. The people who drink this system are the census count.

## where cape town water comes from

Mediterranean winter rainfall is the supply. The hydrological year in the City's outlook runs to about the end of October. Summer is the drawdown. A dry run of winters is what emptied the dams in 2015–2017. A wet week is what can fill them again, and the same wet week is what floods houses on the Cape Flats. Those are one climate, not two products.

The dams sit outside the city because that is where the mountains catch the rain. Theewaterskloof stores the Riviersonderend. Voëlvlei and Berg River Dam sit on the Berg system. Wemmershoek and the two Steenbras dams are closer in, and the City owns those three. Department of Water and Sanitation owns and operates Theewaterskloof and Voëlvlei. The Trans-Caledon Tunnel Authority owns Berg River Dam, and the national department operates it. Cape Town drinks a system it does not fully own. That split matters when someone asks who should pay for the slopes above a dam wall.

Groundwater is not the replacement. The June 2026 outlook says the Cape Flats aquifer had no abstraction for use because the treatment plant was not complete. The Table Mountain Group wellfield at Steenbras and the Atlantis scheme are supplements running below their licences. Do not read them as a new bulk source. The tap is still the surface system.

A second engineered project, the Berg River–Voëlvlei Augmentation Scheme, would move surplus winter water from the Berg into Voëlvlei, about 23 million cubic metres a year. The June 2026 outlook says delivery is later than the 2019 Water Strategy planned. The number of years of slip was not cleanly stated. Desalination, the other leg of the New Water Programme, has slipped far enough that the same outlook pushes a conservative operating stance out toward 2036. A plant can make gallons. This city's existing supply is a landscape that already makes winter rain. That distinction is the subject of [a plant makes gallons. a landscape makes rain](/guide/a-plant-makes-gallons-a-landscape-makes-rain?from=guide). It is not retold here.

## six dams, three owners

On 2 July 2026 the six dams held 686,514 megalitres of 898,221 megalitres of capacity, which is 76.4%. The City's Steenbras page calls these the Big Six and says they hold 99.6% of the system's capacity. Use the June 2026 table for the levels.

| dam | capacity | full on 2 july 2026 | who owns it |
| --- | --- | --- | --- |
| Theewaterskloof | 480,188 Ml | 77.0% | national water department |
| Voëlvlei | 164,095 Ml | 60.2% | national water department |
| Berg River | 130,010 Ml | 86.8% | Trans-Caledon Tunnel Authority owns it; the national department operates it |
| Wemmershoek | 58,644 Ml | 100% | City of Cape Town |
| Steenbras Upper | 31,767 Ml | 90.4% | City of Cape Town |
| Steenbras Lower | 33,517 Ml | 53.1% | City of Cape Town |

Theewaterskloof, at 480,188 megalitres inside an 898,221 megalitre total, is about 53% of the storage. A secondary writeup has put the same dam near 41%. Do not blend those shares. The June 2026 capacities are the ones to use. When Theewaterskloof is full it is more than half the system. When it is not, the city feels it first, because urban demand is the largest use of the system.

76.4% is not a surplus to spend. The hydrological year that ended on 30 October 2025 closed near 85%. Seasonal forecasts had pointed to a dry year. Rivers at Steenbras dried in January 2026. Then a storm — the outlook names both April and early May, and this piece does not decide whether that was one event — lifted dam levels 10 to 30% in a week, with rainfall up to a 1-in-200-year recurrence. Raw water went muddy. Wemmershoek treatment ran low, and demand shifted onto the other dams. A Water Restrictions Steering Committee had already been stood up in November 2025. Full enough to relax is not the same as full enough to ignore.

## the plants under the rain

Fynbos is the shrubland on those mountains: fine-leaved, adapted to periodic fire, and native to the Cape Floral Region. UNESCO describes that region as one of six floral kingdoms, the smallest and, for its size, the most diverse. The region is under 0.5% of Africa's area and holds nearly 20% of the continent's flora: about 9,000 plant species, 69% of them endemic. Those are regional counts. They are not a headcount of Table Mountain National Park, and they are not a price.

The dams do not store "nature." They store winter rain that the vegetation either uses or lets through. Pines, Australian acacias, and eucalyptus planted or invaded into these catchments use more of that rain than the fynbos they replace. That is the mechanism the Greater Cape Town Water Fund was built on. The plants are the supply. The concrete is the storage. The next post in this series stays with the plants. This one only needs the distinction, because a search for Cape Town water that stops at the dam wall has missed the thing that decides the yield.

The fynbos on those slopes, and the winter rain the shrubland lets into the rivers, exist whether or not anyone buys a certificate. If ensurance belongs here at all, it is a way for the utility that already runs part of this system to fund the work of keeping those slopes in fynbos. It is not the shrubland, and it is not a new name for the dam.

## both directions

The city depends on the catchments. More than 95% of what the Water and Sanitation Directorate supplies is this surface system. Informal settlements on the Cape Flats depend on the same supply, and they also sit on former wetlands and riverbeds that flood in the winter that fills the dams. They are not the buyer. They are the people the failure reaches.

The other direction is easy to miss if the story stays inside the municipal boundary. The same system serves Stellenbosch, Paarl, Wellington, and towns on the West Coast and in the Swartland, and it serves irrigators on the Berg, the Eerste, and the Riviersonderend. In the week of 22 January 2018, while the City was modelling a shutdown date, agriculture's share of the draw was 48% and the City's was 47%. That week is not a standing split. It is evidence that the storage is shared. Those irrigators are a real dependency and they are not a payor this series is selling to. The port and the V&A Waterfront depend on the city staying supplied and on Table Bay staying operable. No loss figure for either was pulled, so neither is a buyer here.

Heat on the Cape Flats is a different stress. Neighbourhood surface temperature is not what fills Theewaterskloof. It is already taught as [what financing urban heat island mitigation actually is](/guide/what-financing-urban-heat-island-mitigation-actually-is?from=guide). This series does not open a second heat argument.

Khoekhoe history on the peninsula is the indigenous context of this shore. No orthography for an indigenous city name was settled in the research behind these posts, and no one was invited as a payor. That absence is not a claim that the history is minor.

:::johnson
**cape town drinks six dams. the fynbos is what lets the winter rain reach them.**

The city is the door. The catchment is the subject. [The plants, not the tap](/guide/fynbos-is-not-the-water?from=guide).
:::

## what is already working

The City owns and operates Wemmershoek and both Steenbras dams, and it publishes the dam table. That outlook is the disclosure. National government operates the two largest dams the city drinks. The Greater Cape Town Water Fund, convened by The Nature Conservancy after the close call of 2018, clears alien trees in priority sub-catchments so more of the winter rain reaches the dams. On 1 April 2026 FirstRand issued a restoration-linked bond against that clearing. The fund and the bond are the hero of a later post. They are named here so nobody thinks the slopes are unmanaged.

Day Zero is the failure that reached people. The City set the trigger at 13.5% combined storage. In January 2018 it published a date. The taps did not stop. The threshold is still the threshold. [Day Zero was a date the dams set](/guide/what-day-zero-was?from=guide) is the post that stays with that date, and with the flood that comes from the same winters.

If you already care about a particular slope, a particular dam, or the week the restrictions were real in your building, the useful next step is the plants, not a general plea to protect the city. The parent account that can hold a river and a lake on this protocol is [rivers-lakes.ensurance](/rivers-lakes.ensurance?from=guide). If this is not your catchment, start from [another place](/explore?from=guide).

## frequently asked questions

### where does cape town water come from?

From the Western Cape Water Supply System: Theewaterskloof, Voëlvlei, Berg River Dam, Wemmershoek, and Steenbras Upper and Lower. The June 2026 outlook says this system is more than 95% of the City's supply. The dams are filled by winter rain on mountain catchments, most of them outside the municipal boundary.

### is cape town water groundwater?

No. Groundwater is a supplement, and the Cape Flats aquifer was not being used for supply when the June 2026 outlook was written, because the treatment plant was not complete. The bulk tap is the six dams.

### how full are the cape town dams?

On 2 July 2026 they held 76.4% of capacity, 686,514 megalitres of 898,221. Wemmershoek was full. Voëlvlei and Steenbras Lower were the low ones, at 60.2% and 53.1%. That level followed a flood pulse. It is not a reason to treat the system as comfortable. The same outlook says desalination delays push a conservative stance toward 2036.

### who else uses this water?

Other towns on the system, including Stellenbosch, Paarl, and Wellington, and irrigators on the Berg, the Eerste, and the Riviersonderend. In one week of January 2018, agriculture and the City each drew about half of what left the system. That week is not the annual average.

### what does the fynbos have to do with the tap?

Fynbos uses less water than the pines, gums, and wattles that have replaced it in the dam catchments. The rain those alien trees drink does not reach the dams. The shrubland is the living part of the supply. The dam is the storage.

## what comes next

[Who depends on the western cape dams](/guide/who-depends-on-the-western-cape-dams?from=guide) names the utility, the other towns, and the insurer that already pays flood claims. [Fynbos is not the water](/guide/fynbos-is-not-the-water?from=guide) stays with the plants. The live parent for a river account is [rivers-lakes.ensurance](/rivers-lakes.ensurance?from=guide).

## sources

[City of Cape Town, Water Outlook Edition 13, June 2026](https://web1.capetown.gov.za/web1/newsandnotices/site-media/documents/Water-Outlook-Report-June-2026.pdf) — more than 95% of supply from the WCWSS; dam table for 2 July 2026; 76.4% storage; dry rivers at Steenbras in January 2026; the flood pulse; Wemmershoek treatment; restrictions committee from November 2025; desalination delay toward 2036; Cape Flats aquifer not in use.

[Department of Water and Sanitation, WCWSS study area](https://www.dws.gov.za/iwrp/rs_wc_wss/sa.aspx) — who owns and operates the dams, and the other towns and irrigators on the system.

[City of Cape Town, Steenbras dams](https://www.capetown.gov.za/general/steenbras-dams) — the Big Six and their share of system capacity.

[City of Cape Town, Census](https://www.capetown.gov.za/Local%20and%20communities/Education-and-research-materials/Data-statistics-and-research/Cape-Town-census) — Census 2022: 4,772,846 people and 1,452,845 households.

[UNESCO, Cape Floral Region Protected Areas](https://whc.unesco.org/en/list/1007/) — the region's share of Africa's flora, and fynbos as fire-adapted shrubland.

[City of Cape Town, Water Outlook 2018 summary](https://resource.capetown.gov.za/documentcentre/Documents/City%20research%20reports%20and%20review/Water%20Outlook%202018%20-%20Summary.pdf) — the week of 22 January 2018, agriculture 48% and the City 47%.

## the series

1. [cape town drinks six dams](/guide/what-cape-town-depends-on?from=guide) (this post)
2. [who depends on the western cape dams](/guide/who-depends-on-the-western-cape-dams?from=guide)
3. [fynbos is not the water](/guide/fynbos-is-not-the-water?from=guide)
4. [day zero was a date the dams set](/guide/what-day-zero-was?from=guide)
5. [who already pays for the cape catchment](/guide/who-already-pays-for-the-cape-catchment?from=guide)