Beneath the Cape Flats — the flat, sandy expanse that stretches from Khayelitsha to Mitchell’s Plain to Strandfontein — lies the Cape Flats Aquifer, a groundwater reserve the City of Cape Town is now pumping, treating, and actively refilling as a backup supply that does not depend on mountain rain.

↓ For kids — read this in plain language

Five days ago, on 26 August 2026, South Africa’s Public Works and Infrastructure Minister Dean Macpherson stood inside a recharge plant on the edge of the False Bay Nature Reserve in Pelican Park and called what he was looking at “groundbreaking.” The plant purifies treated wastewater and pushes it back underground — into the same aquifer the city drinks from. He wants other municipalities to copy it.

That ministerial visit was a quiet reminder that Cape Town’s water future runs partly underground. The six mountain dams in the Western Cape Water Supply System get most of the attention — and most of the risk, when the winter rain is thin. The Cape Flats Aquifer is the city’s hedge.

What the Cape Flats Aquifer actually is

The Cape Flats cover roughly 630 km² of low-lying ground between the Cape Peninsula and the Hottentots Holland Mountains. Below that ground sits a sandy, unconfined aquifer — meaning it has no impermeable cap, and groundwater sits close to the surface. Boreholes reach typically around 40 metres down. In places, the aquifer is 55 metres thick.

It is not a pristine underground lake. The Cape Flats Aquifer is made up of fluvial, marine, and wind-deposited sedimentary layers, compressed over millennia. Water moves through the sand slowly, filtered and cooled. The same sand that underlies Khayelitsha, Philippi, and Hanover Park underlies the wellfields now producing water for Cape Town’s pipes.

The City of Cape Town holds licences under the National Water Act of 1998 for both abstracting groundwater from the aquifer and for managed aquifer recharge — pushing treated water back in.

A crisis that changed the pace

The City had studied the Cape Flats Aquifer since the 1960s. A Cape Provincial Administration project started in 1966, prompted by concerns about future water shortages for the Cape Town metropolitan area. For decades the aquifer stayed in the planning files — contamination risks, seawater intrusion near the False Bay coast, and the political complexity of drilling through one of the city’s poorest and most densely settled areas kept it there.

Then 2018 happened. The combined dams fell to around 21 percent of capacity. The City drilled 159 boreholes into the Cape Flats Aquifer that year alone, pulling a combined 41 million litres a day out of the ground as an emergency measure. Speed replaced patience.

The drilling involved no fanfare — just rigs moving through Philippi and Hanover Park while the city watched the dam levels. But it demonstrated something the engineers already knew: the water was there.

How managed aquifer recharge works

Emergency pumping depletes an aquifer. To make the Cape Flats scheme sustainable, the City built a recharge plant — the one Minister Macpherson visited last week — inside the False Bay Nature Reserve at Pelican Park, about 23 kilometres from the city centre.

The plant takes treated effluent from the Cape Flats Wastewater Treatment Works, runs it through four linear filtration buildings, purifies it further, and injects it into the aquifer through a network of boreholes and infiltration ponds. This process — managed aquifer recharge, or MAR — does three things at once: it restores groundwater that abstraction has drawn down, it builds a hydraulic barrier against seawater intrusion from False Bay, and it protects the wetland ecosystems that depend on groundwater flows across the Cape Flats.

The plant’s recharge capacity is up to 40 million litres a day. That is treated wastewater that would otherwise flow into the sea, redirected as a replenishment credit for the aquifer below Khayelitsha and Mitchell’s Plain.

Cape Flats Aquifer Management Scheme

Take it out, clean it, put it back

The sand under the Cape Flats is both a well and a reservoir. The City pumps water out of it on one side of the city, and pushes purified water back into it on the other.

  • Water coming out
  • Water going back in
SALT WATER PRESSURE HOLDS IT BACK BOREHOLES, ABOUT 40 M DOWN SOAK-AWAY PONDS SLOWLY BACK WEST, FILTERED BY THE SAND ON THE WAY GROUND LEVEL DRY SAND THE CAPE FLATS AQUIFER — WET SAND, UP TO 55 M THICK BEDROCK — NOTHING GETS THROUGH FALSE BAY 01 Pump it up Wellfields at Philippi, Hanover Park and Strandfontein 02 Clean it Treated at the nearest works before it goes anywhere near a tap 03 Drink it Into the same pipes that carry water down from the mountain dams 04 Catch it again Used water arrives at the Cape Flats wastewater works 05 Purify it and push it down Pelican Park recharge plant, with four filter halls
BAY UP, FROM 40 M BACK DOWN DRY SAND WET SAND, UP TO 55 M BEDROCK

  1. 01  Pump it up

    Boreholes at Philippi, Hanover Park and Strandfontein draw water out of the wet sand, about 40 metres down.

  2. 02  Clean it

    It goes to the nearest treatment works before it goes anywhere near a tap.

  3. 03  Drink it

    Into the same pipes that carry water down from the mountain dams.

  4. 04  Catch it again

    Used water arrives at the Cape Flats wastewater works instead of running out to sea.

  5. 05  Purify it and push it down

    Four filter halls at Pelican Park purify it further, then push it back through boreholes and soak-away ponds. The pressure also holds False Bay's salt water off.

Out of the ground
54 Ml a day once both phases run — about 6 percent of what the city supplies.
Back into the ground
40 Ml a day the Pelican Park plant can return. Water that used to run out to sea instead pays the aquifer back.
Why refill it at all
  • The level stops dropping
  • The pressure keeps False Bay's salt water out
  • The wetlands above keep their water

The catch Parts of the aquifer carry contamination from decades of industry, farming and thin sanitation, and the sand does not filter all of it. Near the False Bay coast, salt limits what can be used at all. And nobody knows how much water the Cape Flats' unregistered private boreholes take out of the same sand.

The plant also won the Architizer A+ Award Jury Prize in 2025, in the Factories and Warehouses category — a water treatment facility worth looking at.

Where the wellfields are, and who lives there

The Cape Flats Aquifer Management Scheme is divided into discrete clusters, each with its own wellfield and sustainable yield. The main ones: Hanover Park produces around 4 million litres a day; Philippi around 6 million; Strandfontein West around 5 million. Other clusters — Strandfontein North and East, Bishop Lavis, Swartklip — add to the total.

These are not abstract place names on a hydrological map. Hanover Park is a neighbourhood with high unemployment and one of the city’s most persistent gang violence problems. Philippi is the market-gardening district where most of Cape Town’s vegetables are grown, often irrigated with borehole water from the same aquifer. The Cape Flats Aquifer sits under communities that have historically received the least from the city’s infrastructure budget, and they are now part of the supply system in a new way.

The projected yield across Phase 1 and Phase 2 of the scheme is up to 54 million litres a day — adding roughly 6 percent to Cape Town’s bulk water supply. Current daily consumption runs at about 145 litres per person per day across the system. Fifty-four million litres is not a small addition.

The contamination question

The aquifer’s location is also its main complication. Decades of industry, informal settlements, agriculture, and inadequate sanitation infrastructure have left contamination in parts of the Cape Flats groundwater. The sand filters some of it. Not all.

High chloride concentrations near the False Bay coast — seawater creeping inland through the sandy aquifer — limit usable groundwater in that zone. Clay lenses and peat layers within the aquifer create isolated pockets where contaminants can linger. Water extracted from the wellfields goes to the nearest treatment plant before reaching a tap, but the treatment costs money, and not all parts of the aquifer are equally clean.

The MAR scheme’s recharge process adds another filtration step, and the hydraulic pressure of injected treated water pushes back against seawater intrusion. It does not solve every contamination problem, but it is a considered engineering response to what the geology actually presents.

The WWF has noted that many private boreholes across the Cape Flats are unregistered and unmonitored — nobody knows exactly how much water is being drawn, or from where. Unsustainable private abstraction puts the same aquifer the city is spending infrastructure budget to protect at risk.

What the aquifer adds to Cape Town’s water supply

Cape Town’s dam levels this week sit at 76.8 percent of combined capacity — fifteen percentage points below where they were at the same time last year. The winter rain forecast for the catchments has been below the climatological average. The dams are the city’s main store, and a dry winter draws them down.

The Cape Flats Aquifer, the desalination plants, and the water reuse programme are the three supply sources in Cape Town’s New Water Programme that do not depend on how much rain falls on the Franschhoek Mountains. Together, they are expected to cover a significant share of daily use.

The aquifer alone will not save the city from another Day Zero. No single source will. What it does is reduce the proportion of Cape Town’s water that rises and falls with the winter rainfall, which is the variable the city controls least. In a Mediterranean climate turning drier, that matters.

The dams are still the answer to most questions about Cape Town’s water. For the rest, there is what lies under the Cape Flats — for now.