Groundwater is one of the diverse water sources the City is investing in to ensure Cape Town’s water supply remains reliable against future climate shocks. The Monitoring Committee, the first of its kind for the City’s groundwater abstraction projects, met recently for one of their biannual engagements to discuss progress at the Cape Flats Aquifer Management Scheme and the Table Mountain Group Aquifer scheme.
What to know about aquifers:
An aquifer is a body of rock/soil with open spaces that contains large amounts of water that 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 1km deep in certain areas.
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 wastewater and/or stormwater into the aquifer 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 sea water enter the aquifer, the groundwater will no longer be suitable for irrigation and drinking purposes and would also impact natural environments such as wetlands that are dependent on fresh water from the ground.
'The City is planning to invest about R4,7 billion into projects to bring about 105 million litres of groundwater a day online to contribute to our drinking supply by 2036. This groundwater supply target from underground aquifers is part of the City's New Water Programme (NWP) and Water Strategy.
Meetings last week with the respective Monitoring Committees confirmed the Cape Flats Aquifer Management Scheme (CFAMS) and the Table Mountain Group Aquifer (TMGA) groundwater projects are progressing well.
Monitoring Committees are in place for CFAMS and TMGA:
They were formed in line with the water use licence that was issued by DWS to the City in December 2017 for groundwater abstraction and Managed Aquifer Recharge at the CFA, as well as groundwater abstraction from the TMGA. Cape Nature holds the significant role as chairperson at the CFA Monitoring Committee meeting (and previously the TMGA Monitoring Committee meetings).
It comprises various individuals who are environmentalists, farmers associations, scientists, officials (stormwater, wastewater, biodiversity, environmental management, and bulk water), regulatory authorities (Department of Water and Sanitation, Department of Environment, Forestry and Fisheries, and Department of Environmental Affairs and Development Planning). All are Cape Town residents with different kinds of expertise and perspectives to contribute to the City's responsible development and management of these groundwater schemes.
Their primary responsibility includes overseeing the implementation of the monitoring programmes, assessing the effectiveness of applied monitoring to protect the water resources and making recommendations to improve the monitoring for DWS's consideration and approval, and the City's implementation.
'The Monitoring Committees play a very important oversight role to monitor and assess the implementation of the groundwater projects and the water quality. We thank the representatives for keeping the City accountable and for their valuable contribution to Cape Town's journey to secure our future water supply in a way that is environmentally, socially and economically responsible.
'Cape Town is in a water scarce region and City teams are doing all they can to ensure that we continue to invest in and build a reliable and safe drinking water supply through our updated New Water Programme. Diversifying our water sources, through projects such as groundwater, water reuse and desalination, will reduce the City's current dependence on rain-fed dams as the main source of water,' said acting Mayoral Committee Member for Water and Sanitation, Councillor Siseko Mbandezi.
The Cape Flats Aquifer Management Scheme
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 2023.
The Managed Aquifer Recharge component is planned to be operational by 2026/7 and will support the City's vision to create a water sensitive city. This includes the construction of a pre-treatment facility that will treat treated wastewater to a high standard and then inject that high quality water into the Cape Flats Aquifer. The construction phase of the civil part of this project is expected to be completed in 2024.
Table Mountain Group Aquifer
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. To date, the groundwater scheme contributed nearly 12% of the upper Steenbras dam.
Further drilling will be under way soon 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, especially this summer
'While the City is investing in future water supply, residents and businesses are reminded to be water wise at all times to prevent wasting this precious resource. This summer, the City is calling on residents and businesses to use water wisely, fix leaks, and to comply with permanent regulations,' said Councillor Mbandezi.
Links for more information:
Water wise tips: http://www.capetown.gov.za/savewater
City's Water Strategy and New Water Programme: https://www.capetown.gov.za/general/cape-town-water-strategy
Caption 1: Standing (Left to right) David McGibbon, Kornelius Riemann, Phillip Horstman, Susanna Coleman, Nazeer Sonday, David Allpass, Dean Palmer Sitting (left to right) Candice Lasher-Scheepers, Samantha Saayman, Jenny Day, Andrew Turner, Philani Msimango, Nikiwe Solomon
Caption 2: The CFA Monitoring Committee conducts a walkabout around the new Strandfontein West Treatment Works, which is still under construction.
Caption 3: (Left to right) David McGibbon, Dean Palmer, Susanna Coleman, Marcel Woodman, Nikiwe Solomon, Kornelius Riemann, Philani Msimango, Andrew Turner, David Allpass, Samantha Saayman and Nazeer Sonday.
Source: City Of Cape Town