Borehole drilling Picture: Supplied
Borehole drilling Picture: Supplied

#WaterCrisis: Warning that borehole water could run out

By Athina May Time of article published Feb 2, 2018

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Cape Town - Groundwater has become the unspoken fall-back for Capetonians as Day Zero draws near. However, even borehole and well-point water has a finite supply and limitations. Exhausting this supply could have devastating consequences for the environment.

The City is planning to abstract 80million cubic metres of ground water from the Cape Flats aquifer, 30million cubic metres from the Atlantis aquifer and 40million cubic metres from the Table Mountain Group aquifer. There are also 22000 registered boreholes in Cape Town.

According to World Wildlife Fund (WWF) senior manager for fresh water, Christine Colvin, if we take out more water than is going in, we will run out eventually. “Our current groundwater store has been built up over decades by rainfall. Because groundwater is a large store of water, it takes longer than rivers and dams to feel the effects of drought. But to ensure that there is a fair share of this hidden resource for everyone, we need to measure how much we use, monitor the water levels and be sparing.

“If a lot of groundwater is abstracted close to the coast there is a danger of seawater intruding into the aquifer: salt water fills the aquifer and this water can't be used by homeowners or farmers unless it is desalinated back to freshwater. As a coastal city, Cape Town has to monitor and manage this risk if boreholes are drilled below sea level.”

Colvin explained that when we pump groundwater, the water table dropped and boreholes pumping close to each other could interfere with each other and bring down the water table even more.

In extreme circumstances, where lots of groundwater is removed, the aquifer itself could collapse and land sinking can occur.

“Life beyond Day Zero will present exceptional circumstances, which will hopefully see bylaws in place to enable Capetonians to use and share groundwater with neighbours to relieve the burden on the City's emergency Points of Distribution.”

Mayor Patricia de Lille's spokesperson, Zara Nicholson, has said previously that the City’s desalination program follows an environmentally sensitive approach that will ensure sustainable water extraction.

For those interested in having a borehole or well-point installed at their home, Colvin said groundwater was found on properties with certain types of rock below the surface.

If you are on sand, calcrete or hard-fractured sandstone, there is likely to be groundwater. If you live on thick clay or granite, you are unlikely to have groundwater to pump. Well-points are generally cheaper to install and tap into loose sand aquifers, which are generally shallow. Well-points have a narrow diameter pipe and are quick to install.

@IAmAthinaMay

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Cape Argus

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