By Sipokazi Fokazi
Water demand in Cape Town is placing increasing pressure on the city’s supply, with dam levels dropping to 47.8% in April and city officials warning water restrictions could be introduced later this year if daily consumption does not decline. Groundwater plays a crucial role during dry periods but this reliable reserve is on the decline.
A new study by a University of Western Cape (UWC) researcher cautions that while groundwater often helps cities and municipalities cope when dams and rivers dry up, fully understanding how it works is equally important. Such understanding could help policymakers to decide how much water can be used safely and improve how water levels are monitored over time.
In his PhD thesis, which analyses groundwater levels from 2007 to 2024 using borehole data, lead researcher Dr Sesethu Fikileni, in collaboration with fellow researchers Sandiso Zulu and Thokozani Kanyerere from the department of earth science, confirm that not only is Cape Town’s main aquifer system double-layered and separated by rock formations (Malmesbury shale) that allow water to move between upper and lower aquifers but there is a steady decline in groundwater levels across much of the city.
Using a homegrown mathematical modelling tool, scientifically known as a groundwater simulation framework, to predict water availability and flow direction for the Cape Flats aquifer system and Malmesbury shale aquifer system, the researchers found 80% of boreholes show long-term decline, with drops ranging from nearly 2m to as much as 17m over the study period.
The new data shows clear seasonal patterns: groundwater levels rise after winter rains and become shallow between August and October. During dry periods, groundwater levels dropped, especially in areas affected by drought, particularly in Cape Town from 2017 to 2019. Boreholes tapping the shallow Cape Flats aquifer are particularly vulnerable to the dry conditions.
To address the challenges of sustainable groundwater management, it is crucial to have a good understanding of the current status and to forecast future states of this indispensable resource. Therefore modelling is the cornerstone for future preparedness during extreme weather events like droughts and floods
— Dr Sesethu Fikileni, UWC
While a small number of boreholes showed rising groundwater levels, the researchers note that these increases are likely due to irrigation, accidental recharge from leaking infrastructure or water leaking from the deeper aquifer into the shallow one.
In the study’s findings, they note increasing urban development is likely reducing natural recharge by limiting how much rainwater soaks into the ground. In some cases, groundwater levels appear to be influenced more by human activity — such as abstraction, irrigation and infrastructure leaks — than by rainfall alone.
The researchers argue that treating Cape Town’s aquifer as a single water layer could yield misleading results and lead to poor management decisions. Instead, groundwater planning, monitoring and modelling must recognise the dual nature of the aquifer system.
Fikileni said the latest groundwater modelling is crucial as accurate predictions and the flow direction of underground water would help policy makers make better decisions and plan more effectively when allocating water resources to where they’re needed most and help avoid overuse of the complex water resource.
“To address the challenges of sustainable groundwater management, it is crucial to have a good understanding of the current status and to forecast future states of this indispensable resource. Therefore modelling is the cornerstone for future preparedness during extreme weather events like droughts and floods,” he said.
• Author: Sipokazi Fokazi for the UWC institutional advancement unit
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