The importance of groundwater
The time of the Day Zero crisis in Cape Town, many people sank boreholes and wellpoints so they could water their gardens and fill their pools. The trouble is that groundwater is an important resource in times of drought.
The WWF says unsustainable groundwater extraction is a critical risk to water resources, groundwater-dependent ecosystems, such as wetlands, and Cape Town’s water resilience.
To better understand what was happening to the city’s groundwater supply, AB InBev – which has the right to use water from the Newlands springs – funded a pilot project with WWF which included asking residents to monitor their borehole use.
Working with hydrogeology experts GEOSS South Africa, the idea was to establish a “citizen science groundwater monitoring network” in two pilot areas. These were Newlands, a mainly residential area known for its springs and high winter rainfall, and Epping and Airport Industria, a mixed residential and industrial area.
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Both saw a sharp increase in boreholes and wellpoints being dug during the drought. The groundwater monitoring was done using 12 data loggers – six in each area – fitted on to boreholes in private residences, schools and businesses to collect data with every change of season.
This work has already improved understanding of groundwater use and has set in motion a growing monitoring network that will help to inform the management of groundwater.
Greater Cape Town gets most of its groundwater from three aquifers:
• Table Mountain Group Aquifer: a huge aquifer beneath the Western Cape mountain ranges.
• Cape Flats Aquifer: A shallow aquifer, in excess of 400 km², stretching from False Bay to the Tygerberg hills and Milnerton.
• Atlantis Aquifer: about 130 km² in size, stretching from the Atlantic Ocean to the town of Atlantis. There are about 22 000 private boreholes registered with the city in greater Cape Town but there are probably many more which are not registered.
Residents are allowed to extract no more than 400 cubic litres a hectare a year, or the equivalent of just 100 litres a day on a property of 1 000m².
In a report on the project, the WWF says the aim is to grow a monitoring network in Cape Town’s residential and business areas, in order to better understand how groundwater responds to both borehole pumping and rainfall recharge.
The WWF also wants to know how many boreholes there actually are in residential areas. “All this information is critical if we are to understand how much water is being utilised and how the aquifers are responding to abstraction.”
The Danish government recently gave R11 million to this work under the banner of the Table Mountain Water Source Partnership.