Cape Town is using aquifers responsibly
Groundwater abstraction based on a “no regrets” approach
The City of Cape Town’s groundwater programme, which is based on years of research, follows a “no regrets” approach. This means that we have been doing everything that we can to understand our underground resources. We aim to err on the side of caution so that we do not do anything that could cause permanent damage to this resource.
As a result of the unprecedented and severe drought, it was decided to bring forward some of our medium-term augmentation programmes such as groundwater abstraction.
Our programme is based on a conservative approach.
The City and other municipalities in the Western Cape were issued a directive in terms of section 30A of the National Environmental Management Act (NEMA) to undertake water augmentation in response to the worst drought on record. The directive permits augmentation schemes to proceed without unnecessary delays, but it does not exempt the City from compliance with the NEMA or any other applicable legislation.
Also, the projects must comply with the approved environmental management programme, method statement and general duty of care which aims to protect the environment and ensures compliance with applicable legislation. Each project has a dedicated environmental control officer who monitors the abstraction process and ensures compliance with statutory requirements.
Borehole drilling by the City has to this point been restricted to the Steenbras Utility Zone, i.e. an area reserved for utility functions such as bulk water provision within the protected area (which is owned and managed by the City). Furthermore, all proposed drill sites are being screened by the City’s Environmental Management Department (EMD) along with independent specialists in ecological and freshwater systems, and with input from CapeNature and other relevant government bodies.
While drilling is permissible in the utility zone, a duty of care would apply and sensitive features or areas must be avoided and disturbance minimised. Each drilling is required to comply with the approved environmental management programme and method statement, over and above the duty of care.
Its important to note that aquifers are considered both for abstraction and as natural underground storage sites for water. As part of the City’s efforts to build resilience going forward, officials are working on finding a sustainable balance between storage on the surface (dams) and what exists in underground storage (aquifers). The data from the geophysical surveys will further help the City to manage the storage and abstraction of groundwater sustainably in the years to come. Treated wastewater will be used to recharge aquifers. In addition, the City is investigating means to improve the natural recharge of the Cape Flats aquifers.
The City has also consulted with geohydrology specialists who have confirmed that they are comfortable and confident with the City’s groundwater abstraction targets. These targets are supported by historic studies, updated modelling done as part of the current water resilience programme, and preliminary results from recent geophysical surveys. Geophysical surveys allow the City and its partners in other spheres of government to build a detailed model of the aquifer that can be monitored as we abstract and store water.
It is the responsibility of the National Department of Water and Sanitation (DWS) to assess impacts and award licences on the basis of the information available and submitted as part of the water use licence application. The water use licences include specific conditions relating to water use, aquifer management and monitoring which directs how the City utilises and manages the groundwater resources. The water extraction and recharge process will be phased and the effects monitored. The monitoring will determine short-, medium- and long-term management strategies. The recharging of the aquifers also forms part of the entire drilling project to ensure the source is kept sustainable as has been the case for the aquifers in Atlantis which the City has been tapping into for the last 30 years. Site-specific details must be submitted to the DWS on a regular basis for information and approval as part of the ongoing drilling operations.
As part of our overall resilience outlook, we are increasingly focusing on stormwater capture, the removal of alien vegetation on City land in our catchment areas, continued water saving campaigns, pressure reduction to lower water usage, improving on leak and burst rates, and water recycling.
If we look at the removal of alien vegetation specifically, most of the catchment areas of the dams that supply Cape Town are outside of the city boundaries. However, where the City does have some control (such as where it owns land within those catchments), it takes proactive measures.
To illustrate the impact on catchment areas and dams specifically, we can look at the Wemmershoek Dam as an example. Alien vegetation around the dam and in the catchment areas uses a huge amount of water and clearing this vegetation is assisting the City to conserve water that would have otherwise been used by these trees. At Wemmershoek, the saving will be approximately one million litres per day when all pine trees are removed, for instance. Clearing of other dam catchment areas are also under way.
The City has implemented a successful vegetation control programme for more than ten years and will continue to implement this programme.
During 2017, approximately 170 hectares of alien vegetation clearing was completed. Follow-up clearing of the catchment area is scheduled to take place over the coming months. Over the last year, a City-appointed contractor cleared over 50 hectares of pine trees from a City plantation used for commercial and industrial purposes. The remaining 110 hectares will be cleared over the next year. Removing these remaining plantations will improve stream flow into the dam and could secure an extra week or month’s worth of water supply for the city.
The majority of the greater catchment area within the watershed of Wemmershoek dam falls under the jurisdiction of another government entity or private landowners. The City continues to engage these stakeholders.
We will continue to do all that we can to ensure that we do not regret the choices that we make today, tomorrow.
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