Raising dam walls no silver bullet for Cape Town water supply

Given the water crisis affecting parts of the Western Cape, some argue that raising dam walls is an effective way to store more water. The City of Cape Town agrees, but says it’s not as simple as merely adding height to existing structures.

"It's not always as simple as just adding a few metres above an existing dam wall," explains the City's Water and Sanitation Executive Director Leonardo Manus.

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Late last year, following a delay of around 10 years, the raising of the Clanwilliam dam wall finally got underway, but it was not without its challenges, says Manus.

"We had to go down about 15 meters into the foundation again to get a proper base to build the higher part. You basically build a new dam, flush next to an existing dam."

It's quite a costly exercise, explains Manus.

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Moreover, a dam like the Theewaterskloof has already been built beyond the mean annual runoff of the catchment it is in, so raising the walls further wouldn’t increase its water supply.

"It's highly unlikely for the dam to frequently be filled up to 100%"

Manus says the next big project on the cards is at the Voelvlei dam, where a system will be built to pump water out of the Berg River.

"That project is due to start very soon. Berg River dam's raising is also a possibility."

This week, the Western Cape government revealed it is implementing long-term solutions to prevent water scarcity.

More than R800 million will be used for water infrastructure over the next two years.

The money will finance upgrades in all Western Cape municipalities, except Cape Town, as the city has independent plans for desalination.

To listen to Manus in conversation with CapeTalk’s John Maytham, use the audio player below: