Drill Baby Drill.
Impact of Cape Town's plan to tap underground aquifers.
Sirkelsvlei, the Cape of Good Hope Nature Reserve's largest lake, has under normal climatic circumstances, water in it all year round. Now it is dry (as pictured above, Dec '17), and despite there having been some rain, it was virtually empty throughout last winter. The rainwater must have sunk into depleted underground spaces.
What else fills those spaces?
In October last year, Anthony Turnton, a long time commentator on water issues, warned that by abstracting fresh groundwater close to the coast, seawater will seep through to replace it. The city must have considered this carefully before announcing that it plans to pump more than previously thought from local aquifers close to the city. A hundred and fifty million litres a day is planned to be taken from the vast networks of cracks and caverns below the city and its mountain wilds. (The city needs a minimum 500 million litres.)
The ecological question
The ecological impact of this is being debated. Dr Jasper Slingsby, a local ecologist at UCT, thinks that this is a great unknown factor. ‘It’s difficult to get good data on this,’ he says. 'Hydro geology isn’t an exact science.' It would take more than a couple of decades to get the numbers in, he says. Or before we actually see it impacting plants.
He thinks that if we prioritise people over biodiversity, we should go into it with eyes wide open. Don’t say, though, that this has no environmental impact. Logically, he says, there will be. Particularly the unique spots on the mountain where water seeps out, and plants have adapted to having water most of the year.
It is these plants that make the Cape's flora utterly unique. Their disappearance would have serious implications.
‘We have the most diverse temperate flora in the world. One of the few completely restricted to one country. We have the responsibility to take care of it,' he says.
Drilling into the aquifers, he adds, is not going to stave off Day Zero. It is not a short term solution. It may be useful over the next 5 - 10 years.
But the beleaguered Cape Town Mayor has a unenviable juggling act. 'The City’s programme is based on an environmentally-sensitive approach," says mayor De Lille. It will ensure sustainable water abstraction, meaning that generations of Capetonians will benefit from this groundwater. 'This is the first time such extensive mapping has been done and will ensure responsible use of groundwater through, for instance, the water recharge of these aquifers.'
But what of the City's plans to degrade an important aquifer?
About half of the Philippi Horticultural Area is still wild. About 1 500 hectares is farmed. It makes Cape Town one of the few cities that provides a large percentage of its fresh produce within its boundaries. About 150 000 tonnes of vegetables and flowers a year are harvested here. Thanks to the aquifer below it, it yields all year round. Without it, higher food miles would get clocked up in the dry season through food imports.
It is predicted that covering it in concrete will mean less water will seep into replenish the local aquifer. Food will have to be brought in from further afield. Food security and the jobs of thousands of people working there will be jeopardised. The benefits of a green space so close to densely packed impoverished communities will be lost.
Hopefully this will not be lost on De Lille and her fellow planners.
Get Rid of the Aliens
Slingsby says one better solution than drilling into rock would be to clear alien vegetation from the catchment areas. Estimates are that they consume two to three months of water (a year?) and this could rise considerably, if not controlled. In heavily invaded areas near catchment zones, Cape Nature estimates as much as 30% of run off is wasted.
Lessons from further afield
The extraction of California’s natural groundwater has resulted in land subsistence. Roads and irrigation canals there are being damaged at a monthly rate of half an inch. Water reserves are now under threat. Come a drought and Californian farms could turn to dust.
With the results of upsetting delicate natural balances seemingly only to be felt a long way off, dramatic announcements like drilling above sensitive biomes may be good politics. It could stave off calls for the mayor to resign. It is also going to be good business for the companies doing the underground surveys and the mining of the water. But is it going to stave off the immediate drought?
Mother Nature Mothering the Mother City
On the brighter side, come the rains, eventually, the city would be hopefully able to turn off the taps into the ground, and let the natural balances that have evolved and sustained the Cape's geographically and biologically unique and important features do what they have done over millions of years.