Weekend Argus (Saturday Edition)
Alternates aplenty ‘but conserving water is better’
AS CAPE Town moves to enforce level 3b water restrictions questions have been raised about alternate water resources. Possible solutions to improving water supply guarantees include rainwater harvesting, desalination and water reuse.
More than 10 years ago the Table Mountain Group aquifer project began to extract groundwater, but the city believes no amount of planning would be able to protect residents from the effects of drought. The only way is to conserve water.
Chris Hartnady, the research and technical director at Umvoto, was part of the team that conducted research into theaquifer project.
He helped pen the research paper “Large-scale quantification of aquifer storage and volumes from the Peninsula and Skurweberg Formations in the southwestern Cape”. It formed part of an aquifer feasibility study and pilot project in 2001.
The purpose of the study was to determine the feasi- bility of augmenting the city’s underground water supply using groundwater, specifically from the Peninsula and Skurweberg Formation aquifers.
The project had four phases. The study area extended from Wolseley in the north to Cape Hangklip 70km southwards, and from the Berg River system in the west to the Breede River system in the east.
Hartnady said target zones had to be close to the dams. Ten boreholes were drilled in three target areas, but the project was halted in 2010.
Roger Diamond, who lectures in hydrogeogology at the University of Pretoria, said Cape Town used surface water for public supply, but there was great potential for groundwater – like the Table Moun- tain Group aquifer – to be used. However, he said aquifers took time to show environmental damage and it took a while to remedy the problem.
Barrie Low, an ecologist and environmental scientist, said there were a number of aquifers in the Western Cape. He claimed the city was not even looking into the Cape Flats aquifer. He said aquifers formed when rainwater seeped into the ground and hit an impermeable layer of rock.
The city said it had been studying the deep aquifer underlying the Cape Folded Mountain Belt, which runs from Vanrynsdorp to Mossel Bay.
Xanthea Limberg, the mayoral committee member for informal settlements, water and waste services, and energy, said the study had been running for more than 10 years “to determine the best possible sites to extract water with minimal impact on the environment”.
The city said the Table Mountain Group aquifer project was ongoing. “The exploratory phase concluded in 2012, and the design work and supply chain management pro- cedures to commence the pilot phase have been under way since 2015,” Limberg said.
The city planned future water resources for the region together with the national Department of Water and Sanitation and other stakeholders.
“The timing of the city’s future supply schemes is planned according to long-term population and water demand growth projections. A new supply scheme is, however, not the answer to the current drought conditions.
“Best practice during drought conditions is to protect potable water supplies through reduced consumption rather than increased production, as large capital projects will have the effect of pushing up the price of water to pay for infrastructure and may constitute wasteful expenditure when the drought breaks and our dams fill up.”
The severity of droughts and when they occurred could not be predicted. “Therefore planning and building infrastructure in anticipation of a drought isn’t possible.”
Limberg said water supply alternatives included the Berg River to Voelvlei augmentation scheme phase one, to be constructed by the Department of Water and Sanitation over the next few years.
“Beyond this, water supply schemes such as the expansion of our groundwater use, reuse of water and desalination are planned over 20 to 30 years. Feasibility studies for these schemes are either in progress, or have been completed and constitute the groundwork for future implementation.”
With regard to the Cape Flats aquifer, Limberg said: “The city will be looking to make use of this resource in an environmentally responsible manner, however, surface water schemes even into the long term will continue to make up a significant portion of our supply. Given current available resources and projected population growth, no amount of planning will be able to shield Cape Town’s residents from the effects of drought. Even once the schemes are in operation it may be necessary to drive down demand with restrictions in times of low rainfall.”