Groundwater projects on track to help build Cape Town’s future supply

On Sunday, 20 March, kick-starts National Water Week. During this period, groundwater is this year’s focus for World Water Day, recognised on Tuesday 22 March. In light of this, Mayoral Committee Member for Water and Sanitation Councillor Zahid Badroodien visited the Cape Flats Aquifer Management Scheme in Strandfontein. This is one of three City groundwater projects that are each progressing well. Groundwater is one of the diverse water sources the City is investing in to ensure Cape Town’s supply remains reliable against future climate shocks.

Did you know? An aquifer is a body of rock/soil with open spaces that contain large amounts of water which collects beneath the earth’s surface. Aquifers are not affected by evaporation in the same way that dams are. The City targets both shallow and deep aquifers. The Peninsula Aquifer (within the greater Table Mountain Group Aquifer) extends further than 1 km deep in certain areas. The City of Cape Town’s Water Strategy sets the course toward a future in which Cape Town has sufficient, reliable water from diverse sources, including groundwater, so that we can be more resilient to the impacts of climate change. It also outlines other City commitments to wise water use, safe access to water and sanitation services, regional water system collaboration and becoming a water sensitive city. The ‘managed aquifer recharge’ (MAR) process is one way to ensure adequate groundwater supply while maintaining environmental sustainability. MAR is where the City puts back highly treated waste water and storm water into the aquifers to replenish it. It gets filtered and cleaned further as it makes its way through the rock, sand and soil, and is then abstracted downstream and treated once again before use. MAR is also used to form barriers along the coast to prevent sea water from seeping into the aquifer’s fresh water supply. Should this sea water enter the aquifer, the City will not be able to use the water for its municipal drinking supply.

The City is planning to invest about R4,7 billion into projects to bring approximately 105Ml/day of groundwater online to contribute to our drinking supply by 2036.

This groundwater supply target is part of the City’s New Water Programme (NWP) and Water Strategy.

The City identified the Cape Flats Aquifer and the Table Mountain Group Aquifer as resources that can be used in a responsible way to augment water supply within the Western Cape Water Supply System (WCWSS). The City is also upgrading the existing Atlantis Aquifer scheme.  This is supported by the National Department of Water and Sanitation, through the update of their Reconciliation Strategy for the Western Cape Water Supply System (WCWSS)

Mayoral Committee Member for Water and Sanitation Councillor Zahid Badroodien said the progress on site at the Cape Flats Aquifer was encouraging.

‘I am very pleased with the progress on site. The City will be investing approximately R2,6 billion into the Cape Flats Aquifer project. The boreholes are expected to produce 50 to 60 million litres a day, incrementally starting 2022, to help ensure that Cape Town’s drinking water supply is reliable in the face of unpredictable rainfall and climate change impacts.

‘This project is a key component of our New Water Programme, which is exceptionally important and designed to ensure that Cape Town’s water supply is able to navigate future droughts. We are looking to produce an additional approximately 300 million litres of water a day by 2030. The Cape Flats Aquifer, as well as Table Mountain Group Aquifer and the Atlantis Water Resource Management Scheme, are key to achieving this goal so I am happy to know that work on each of the sites are on track.

‘The City has been successfully and responsibly tapping into groundwater in Cape Town since about 1980, when the first managed aquifer recharge scheme was started at Atlantis. The Water and Sanitation team takes great care to manage these schemes in a very responsible way by looking after our environment and providing a more reliable water supply for residents,’ said Councillor Badroodien.

Update on groundwater projects underway:

• Cape Flats Aquifer Management Scheme (CFAMS): 

Drilling and construction operations are well under way and the first wellfield (borehole cluster), located in Strandfontein, is almost complete. The first groundwater injected into the water supply network from this scheme is expected towards the end of the second quarter of 2022. The Managed Aquifer Recharge component is planned to be operational by 2026 and will support the City’s vision to create a water sensitive city.

Managed recharge means the City will fill up the aquifers where groundwater has been used, on an ongoing basis.

• Atlantis Water Resource Management Scheme (AWRMS):
  The AWRMS has been in operation for the past 40 years.  The scheme consists of stormwater collection ponds, recharge basins, coastal recharge basins, treatment plants, and two wellfields (Witzands and Silwerstroom).

Currently, the scheme is being upgraded and expanded through the NWP. It is expected to bring in an additional 10 Ml per day from the new wellfield situated in between the Witzands and Silwerstroom wellfield. The current supply from the existing wellfield varies between five and 13 Ml per day. The refurbishment plan for the existing wellfields will contribute an additional 12 Ml/d. The eventual total capacity from the combined Atlantis wellfield will therefore be about 35 Ml/d.

The established Managed Aquifer Recharge component uses treated domestic wastewater and stormwater, which is diverted to the recharge basins, where it infiltrates into the sandy aquifer. Only the Witzands Wellfield receives Managed Aquifer Recharge water.

• Table Mountain Group Aquifer (TMGA):
  The first borehole cluster is located alongside the Steenbras Dam and produced its first water in 2020. Thus far, the boreholes drilled have targeted the Nardouw Formation of the TMGA, and these boreholes range from 150m to 350m in depth. These boreholes have the potential to produce a cumulative yield of 19Ml per day.

Currently, the City has equipped seven boreholes, capable of producing 18Ml per day. These are injected into the water supply network, coming via the Steenbras Dam and the Faure treatment plant.

Further drilling is under way and targets the deeper Peninsula Formation of the TMGA. The City has already completed one borehole reaching 1km in depth. It is anticipated that the full yield of the Steenbras Cluster will be about 25 Ml/d.

Environmental mitigation and controls are administered to ensure the protection of the Steenbras Nature Reserve, which falls within the Kogelberg Biosphere Reserve.

Be water-wise at all times:
The City encourages residents and businesses to continue to be water-wise, keeping in mind that drinking water is a limited resource.

For water-wise tips and relevant regulations visit: http://www.capetown.gov.za/thinkwater.

For the City’s Water Strategy and New Water Programme visit: http://www.capetown.gov.za/general/cape-town-water-strategy