The City of Cape Town's (CoCT) borehole drilling programme has scientists scratching their heads at the apparent determination of the City to drill into the hard rock of the Table Mountain Group Aquifer (TMGA) at great cost, while other cheaper and more environment-friendly options are not first explored.
Dr Jasper Slingsby of the South African Environmental Observation Network (SAEON) suggests that alternative initiatives, like clearing of alien vegetation could see as much as 100 million additional litres of water running into our dams daily, increasing the supply by as much as 20%, at much less cost to ratepayers.
This view is shared by Dr Jane Turpie, Deputy Director at the University of Cape Town's Environmental Policy Research Unit, who writes that the most affordable ways to boost its future water supply is to decommission commercial forestry plantations in catchment areas that feed the dams and clear invasive alien plants in these key water catchments.
"I have been shocked by the City's lack of willingness to address the issue of invasive trees in our catchments. They're currently using more water than the projected losses under the worst case climate change scenarios, yet the City's Water Resilience Plan, is justified by the threat of climate change and completely ignores the more imminent threat of alien trees... Clearing aliens is much cheaper than any augmentation scheme, creates jobs, protects biodiversity, reduces fire risk, reduces soil erosion and dam sedimentation," says Dr Slingsby.
Executive Deputy Mayor, Alderman Ian Neilson, claimed the City had implemented a "successful vegetation control programme for more than 10 years" but pointed out that most of the catchment areas of dams supplying Cape Town were "outside of the city boundaries and thus are not directly under the City's control".
He cited the Wemmershoek Dam, around which 170ha of alien vegetation was cleared in 2017, with a further 110ha to be cleared over the next year.
The City has also come under fire from Professor Anthony Turton of the Centre for Environmental Management at University of Free State, who has criticised the City for failing to properly evaluate the cost-benefits of drilling for groundwater, saying the decision is not based on "robust information".
"The City cite a misguided report by a post doctoral student that claimed the Millennial Drought in Australia had caused authorities to 'over-react' and build desalination plants that they have now had to 'mothball'. In fact, they are building more desalination plants," he says.
"Groundwater is cited as being the least cost option, but it is compared to desalination at a grossly inflated price. This is not a fair assessment. Groundwater cannot be costed at present because too little information is available to make an informed decision.
"In the public interest we also need to flush out an accurate evaluation of the true costs and benefits of a range of water treatment technologies, including but not limited to: Managed aquifer recharge, desalination, recovery of water from waste, and the viability of additional bulk water storage for surface water systems."
In response, Neilson claimed Turton's claim was "misleading" and that massive capital projects in response to a drought could overburden the ratepayer, if normal rainfall resumes and the drought turns out to be a discrete event.
He said "re-commissioning" of Australian desalination plants "does not detract from our argument" and that desalination forms "only one part of our water augmentation effort".
He re-iterated that the costs of large-scale desalination would have a big impact on the price of water.