Cape water crisis

Cape Town's water supply is in a crisis, with the level of its three biggest dams at an unprecedented low.

This is in the context of an already-stretched water supply that struggles to meet demand as the population grows, says climate change expert Bob Scholes.

Theewaterskloof Dam, the biggest, is at 33.6% of its capacity compared with nearly 76% three years ago. Voëlvlei Dam, the second biggest, is at 19.8% compared with 63% three years ago, while the third biggest, the Berg River Dam, is at 24.5% compared with nearly 90% three years ago.

Overall, Cape Town's dams are 31% full, compared with 56.5% a year ago. Anything under 50% was a major warning signal, said Scholes, adding that "it will take several years to replenish it and we certainly should be concerned".

He also warned that the quality of the water deteriorated when the levels were that low because contaminants were not diluted enough."

"The water tends to be warmer because it is shallower, and that leads to pollution problems as well," he said.

Cape Town mayoral committee member for utility services Ernest Sonnenberg said plans were afoot to "build a scheme to pump excess winter water from Berg River into Voëlvlei Dam". Groundwater expansion, water reuse and desalination were also being considered, but while the city could focus on planning, it was up to the national government to consider measures "from a crisis management perspective".

Only 2% of Cape Town's potable water supply is from groundwater, and it is thought that this figure can be raised to 7%.

Chris Jack, a researcher at the Climate System Analysis Group at the University of Cape Town, said boreholes were being sunk in many cities in the region to compensate for a lack of municipal water supply.

But groundwater extraction "can have negative impacts such as land sinking, salt water intrusion in coastal areas like Cape Town, and a drop in water quality" and borehole pumps were "further straining electricity supplies".

Scholes said: "It is positive or negative depending on where the boreholes are because mostly in South Africa, they tap into a non-replenishable water supply, in other words, fossil water."

This solution "could only give us some breathing space" because, unlike dams, groundwater was not subject to evaporation. But it was "not a sustainable solution".

Normal winter rainfall would not be enough to fully replenish dams.

Department of Water and Sanitation spokesman Sputnik Ratau said the South African Weather Service had predicted that the next two summer seasons would continue to produce insufficient rainfall.

"This will and must stress the fact that the lack of water supply will in the foreseeable future continue to be negatively affected by a general lack of rain," he said.

Dam levels throughout the country were "very low" and the department had worked with provinces and affected municipalities to find new sources of water.

These include drilling new boreholes and transporting water.