The Steenbras dams seem surprisingly full, even though we are experiencing a drought, but there are a number of factors to take into consideration.

Upper Steenbras is not only used for water storage. It forms the upper reservoir for the City’s Steenbras pumped storage scheme, which generates extra electricity during peak demand.

During peak demand, water from Upper Steenbras is channeled through the turbine generator to create electricity. Water collected in Lower Steenbras is pumped to the upper dam at night, using low-cost surplus power.

Upper Steenbras is also linked by canal and pipeline, to Rockview Dam, the upper reservoir of the Palmiet pumped storage scheme operated by Eskom​​​ and the Department of Wate​r and Sanitation​​​. It receives transfers from the Palmiet River via this scheme.

The Steenbras dams are part of the Western Cape Supply​ Syst​em (WCW​SS)​ ​– an integrated system of dams, pump stations, pipelines and tunnels.

In addition to serving Cape Town, the system supplies water to the Overberg, Boland, West Coast and Swartland areas and it helps to optimise the use of water resources, as water can be transferred between dams and catchment systems.

The City carefully manages our water supply and currently maximises water stored in Upper Steenbras Dam as it provides for distribution over a wide area. From its elevated location, we can feed either the Faure water treatment plant via the storage dam at Firlands, or the Steenbras water treatment plant via Steenbras Lower.

The ‘Big Six’ dams hold 99,6% of the WCWSS’s capacity, but Upper Steenbras Dam is the smallest of the dams and holds less than 4% of the water in the WCWSS. This is a small amount if you compare it with the amount of water that the largest dam, Theewaterskloof, can hold. When full, Theewaterskloof holds more than half (53,5%) of all the water in the system.

The Big Six dams include:

• ​Berg River 
• Steenbras Lower
• Steenbras Upper
• Theewaterskloof
• Voëlvlei
• Wemmershoek