Potential of groundwater in spotlight again amid Western Cape drought

1st December 2017 By: Donna Slater - Creamer Media Contributing Editor and Photographer

Groundwater still holds significant potential to provide water for various uses, especially to augment large-scale supply during a drought, notes Geological Society of South Africa Western Cape groundwater division chairperson Dr Roger Parsons.

He points out, however, that, although vast swathes of the Western Cape, and especially Cape Town, are experiencing the worst drought in recorded history, the use of groundwater is not widespread.

Ironically, Cape Town was established where it is on the basis that it had easily accessible groundwater, he says. “Cape Town exists because of groundwater, but this resource was overshadowed by the construction of dams in the past century.”

When the Dutch made landfall in South Africa centuries ago and were looking to establish a refreshment station, Saldanha was the preferred site, owing to its natural landform, which can be exploited as a harbour. However, Parsons points out that Cape Town trumped it, primarily owing to several springs flowing out of Table Mountain and towards the area where the Castle of Good Hope was built. Such springs also led to the establishment of Company’s Garden – a park and heritage site in central Cape Town.

“Cape Town lived off the springs and aquifer water almost exclusively until the early 1890s,” he states.

However, Parsons says, currently, Cape Town does not extensively use groundwater. In recent history, groundwater was sourced from the Atlantis aquifer, but reduced quantities of water are currently drawn from this source because of a pipeline from Melkbosstrand to Atlantis, which was built in about 1999, thereby reducing dependence on groundwater from the Atlantis aquifer, he explains.

Nationally, groundwater currently accounts for only about 15% of all water consumed.

The most extensive users of groundwater are agriculture and small towns and settlements in the western parts of South Africa, many of which almost entirely depend on it as a source of water, he says.

Parsons adds that larger cities use groundwater to a lesser degree despite the existence of some groundwater in locations such as the City of Pretoria, which was founded because of the existence of natural fountains.

The divergence from using groundwater and instead relying almost exclusively on surface water resources is driven by a combination of the lack of appreciation of groundwater, its dispersed nature and the infrastructure required for extraction, as well as its management requirements. Parsons says that, as groundwater cannot provide the volume of water required by large cities, it is too often “pushed aside” in favour of surface water schemes.

Groundwater is primarily recharged by rainfall, which seeps into the ground. It is also not an infinite resource, highlights Parsons, warning that someone cannot just drill a borehole and pump from it negligently and without consideration for the below-ground resource.

He says groundwater has significant potential to augment national supply, but that careful management and monitoring are essential to safeguard groundwater, which cannot simply be visually monitored the way surface water resources are.

The management and monitoring of groundwater fall under the custodianship of the Depart- ment of Water and Sanitation, with a degree of moral responsibility also being shouldered by operators of private boreholes or wellpoints.