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City’s long-term water security boosted with first groundwater into Steenbras Dam <p>​Groundwater is a key part of the City’s new water supply programme to diversify the mix of water sources available. The City initiated drilling operations at Steenbras during the drought crisis and the Table Mountain Group (TMG) aquifer is now producing its first yield of groundwater at the Steenbras wellfield.</p><p>The TMG aquifer is believed to be the largest in the world, and currently drilling has reached a depth of 710 metres below ground. </p><p>‘The launch of the first groundwater from the Table Mountain Group aquifer is very exciting because this is testament to the City’s commitment in action to contribute to our long-term water security. This milestone needs to be celebrated as it is a step closer to seeing our Water Strategy become a reality. The TMG aquifer is one of the projects listed in the strategy, which was launched in February this year. With the drought and given the changing climate, we have learnt there is a need to diversify our water sources and not rely solely on surface water.</p><p>‘The Water Strategy is an ambitious roadmap towards a future in which Cape Town is more resilient to drought and other climate shocks, meaning that sudden, extreme levels of water restrictions should not be necessary. It takes into account the important yet complex relationships between water, people, the economy, and the environment. I am glad to know we are on track with investing in our long-term resilience and water security,’ said Mayor Plato. </p><p>The Table Mountain Group is a geological formation that extends from Nieuwoudtville in the north, to Cape Agulhas in the south, and Port Elizabeth in the east. It is identified as a significant source of groundwater storage in the Western Cape and is known as the Table Mountain Group aquifer. </p><p>There are currently eight completed production boreholes, yielding almost 20 million litres per day. Drilling of a further four is underway, which will eventually increase the yield to 30 million litres per day.</p><p>‘To put this into context, 30 million litres per day is the equivalent of a daily water supply for around 200 000 people at current consumption levels of 125 litres of water per person, per day. Alternatively, this would represent 16 days’ worth of water for the whole city, for every year of operation.</p><p>‘Although there isn’t currently an urgent threat to our immediate water security (provided current restrictions are adhered to), we are still encouraging residents to not forget the very valuable lessons learnt about the finite nature of water, our most precious resource.</p><p>‘The City of Cape Town has been studying the character and behaviour of this aquifer for more than 10 years, so by the time the drought crisis reached the point where exploratory drilling needed to take place, it was done with a wealth of prior research. The Steenbras Wellfield was chosen due to favourable hydro-geological conditions giving rise to a potentially high groundwater yield, with the benefit of being in close proximity to the Steenbras Dam. This is ideal as the groundwater can be pumped directly into the dam and treated at the Faure water treatment works to drinking-water standard,’ said Alderman Limberg.</p><p>A key highlight in this project is the environmental mitigation and controls administered to ensure the protection of the Steenbras Nature Reserve, which falls within the Kogelberg Biosphere Reserve.</p><p>These measures include the search and rescue of protected vegetation, topsoil management, reusing onsite material to prevent changes to ground conditions (e.g. screening and reusing excavated material instead of importing new material), matching historical groundwater and surface water movement across trenches, installing power lines underground to allow for veld fire preventative management and reducing the visual impact of pylons, spanning pipelines across rivers instead of trenching through them, as well as rehabilitating disturbed areas after construction.</p><p>Due to the environmental sensitivity of the area, and the risk of damage by natural fire cycles in fynbos, medium-voltage power cables, and fiberoptic cables, were buried in the same trenches as the pipelines. </p><p>The fiberoptic cable network feeds all data from the respective boreholes to a centralised Supervisory Control and Data Acquisition (SCADA). The SCADA allows the wellfield to be controlled and operated through an automated system.</p><p>‘Invasive alien vegetation is being removed from the Steenbras Nature Reserve catchment area, in an effort to maximise the rainwater surface run-off yield into the Steenbras Dam. Pine and blue gum trees are being systematically removed and the land is carefully rehabilitated with indigenous vegetation. Alien vegetation clearance and various other short-term projects, are also providing local work opportunities through the Expanded Public Works Programme (EPWP),’ said Alderman Limberg. </p><p>The National Department of Human Settlements, Water and Sanitation is the custodian of groundwater in South Africa. They have issued the City with a water use licence to abstract water and construct supporting infrastructure for this aquifer project.  The total licenced volume for Phase 1 of this project is 33 million litres per day, with an additional 15 million litres per day expected from the Nuweberg wellfield, which is currently in the exploratory drilling phase.  The Steenbras Wellfield also forms part of the Western Cape Water Supply System (WCWSS), which has been established in collaboration with the National Department of Water and Sanitation. The long-term abstraction of groundwater will be balanced against the availability of surface water and other water sources within the WCWSS.</p><p>‘We want to thank all our staff and our key roleplayers and stakeholders who have been instrumental in seeing this project become a reality, which will contribute to our city’s water supply,’ said Alderman Limberg. </p><p>More information about the City’s Water Strategy, click <a href="">here</a>.</p><p><br><strong>End</strong></p>2020-08-05T22:00:00ZGP0|#1d539e44-7c8c-4646-887d-386dc1d95d70;L0|#01d539e44-7c8c-4646-887d-386dc1d95d70|City news;GTSet|#62efe227-07aa-45e7-944c-ceebacca891dGP0|#1b05f64b-82b6-48ff-9032-784fac58cf97;L0|#01b05f64b-82b6-48ff-9032-784fac58cf97|executive mayor;GTSet|#2e3de6c1-9951-4747-8f53-470629a399bb;GP0|#a56018a2-0c7a-4055-af9c-df4728adb384;L0|#0a56018a2-0c7a-4055-af9c-df4728adb384|water and waste1


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