Milnerton Lagoon: Recovery and Responsibility
Understanding Milnerton Lagoon's pollution, environmental recovery, the City's R15-million intervention and the future of this coastal ecosystem.
Environmental Recovery, Responsibility and the Limits of Intervention
Understanding the relationship between water quality, ecological recovery and human responsibility in one of Cape Town's familiar coastal environments.
A changing environmental landscape
Milnerton Lagoon is an important part of Cape Town's coastal landscape. Situated between Woodbridge Island and the Diep River estuary, it forms part of an interconnected natural environment where freshwater, seawater, vegetation, birdlife and human activity meet.
For many years, however, the lagoon has been associated with serious water pollution, sewage contamination and environmental deterioration. Its condition has affected more than the appearance of the water. It has raised questions about ecological health, public safety, infrastructure management and the long-term responsibility of those tasked with protecting the environment.
Recent observations suggest that conditions are improving. Water-quality measurements have shown encouraging changes, while reports of returning fish and regenerating seagrass provide further indications that the lagoon retains some capacity for ecological recovery.
Yet improvement does not necessarily mean that the underlying environmental problems have been resolved.
A recent GroundUp report, published on 11 November 2026, highlights this distinction through the City of Cape Town's R15-million groundwater pilot project. The intervention aims to improve conditions in the lagoon by introducing saline groundwater extracted from below Milnerton Beach. Although the project represents an additional attempt to improve water quality, environmental concerns remain about whether dilution can provide a sustainable solution to pollution originating elsewhere in the catchment.
The situation raises a broader question: what does genuine environmental recovery look like, and how should it be evaluated?
Water Quality Updates Milnerton Lagoon, Woodbridge Island
Understanding the sources of pollution
The environmental condition of Milnerton Lagoon cannot be understood by examining the lagoon in isolation. Its water quality is influenced by activities and infrastructure across a much wider geographical area.
One of the principal historical sources of pollution has been the Potsdam Wastewater Treatment Works. According to the GroundUp report, the facility has discharged more than 40 million litres of effluent daily into the Diep River, approximately five kilometres upstream of the lagoon. Department of Water and Sanitation data cited in the report indicate that Potsdam has failed to meet national effluent standards since 2018.
Other contributing sources include stormwater runoff from the Joe Slovo informal settlement, industrial activity around Montague Gardens, sewer pipe failures, pump station overflows and agricultural runoff from the upper catchment.
These sources illustrate the interconnected nature of environmental systems. Pollution entering a river upstream does not remain confined to its point of origin. It moves through the catchment, influenced by rainfall, water flow, sediment and other environmental conditions, eventually affecting downstream ecosystems.
The lagoon therefore reflects the cumulative consequences of activities taking place beyond its immediate geographical boundaries.
Understanding this relationship is essential when evaluating any proposed environmental intervention.
Signs of recovery, but not necessarily restoration
There are encouraging indications that water quality has improved since 2024.
UCT professor Kevin Winter, quoted in the GroundUp report, identified reductions in bacteria, ammonia, nitrogen, phosphorus and chlorophyll. Some water-quality measurements at Woodbridge Island Bridge were approaching conditions previously observed in 2018.
However, individual measurements need to be interpreted within their wider environmental context.
The report provides a particularly revealing example through E. coli readings. On 8 September 2026, a measurement at Woodbridge Island reached 141,000 colony-forming units per 100 millilitres. The report identifies 4,000 cfu/100ml as the threshold below which canoeing is considered safe. The elevated reading reportedly persisted for at least a month.
By 20 October, the recorded E. coli level had fallen to 1,600 cfu/100ml, categorised as an acceptable risk. Nevertheless, nitrogen, ortho-phosphate and un-ionised ammonia remained at unacceptable levels.
These contrasting measurements demonstrate why environmental assessment requires more than a single favourable reading.
Water quality is influenced by several variables, and improvements in one indicator do not necessarily establish that the wider ecosystem has returned to a healthy condition.
There are also visible ecological indicators. Following heavy rainfall in 2025, residents reported that the sewage smell had disappeared, seagrass began to regrow and large schools of fish returned.
Such observations are encouraging. They suggest that environmental conditions can improve when some of the pressures affecting the lagoon are reduced.
However, a cleaner appearance, the absence of an unpleasant smell or the return of fish should not be confused with proof of sustained ecological restoration.
The R15-million groundwater intervention
The City's pilot project introduces another dimension to the environmental management of the lagoon.
The R15-million initiative involves extracting saline groundwater from below Milnerton Beach and adding it upstream of the lagoon. According to the report, the intended effects include increasing dissolved oxygen and salinity while helping to flush pollutants out towards the sea.
UCT professor Kevin Winter described the project as a bold experiment but questioned its longer-term environmental value if the original pollution sources remain unresolved.
His central concern is that dilution does not eliminate pollution. It changes the concentration and movement of pollutants without necessarily addressing their origins.
This distinction is important.
Environmental interventions can improve immediate conditions, but their effectiveness must be assessed against the underlying causes of degradation. If polluted effluent, sewer failures and contaminated stormwater continue entering the catchment, the lagoon remains exposed to recurring environmental pressures.
The City has indicated that the project will operate as a six-month trial, with water quality and environmental conditions monitored to determine whether it should continue, be modified or stopped.
The intervention is also being undertaken under a directive issued in terms of section 28(4) of the National Environmental Management Act.
An important consideration is the lagoon's existing tidal character. The City has explained that saline water intrusion has previously been recorded as far upstream as the Otto du Plessis Drive Bridge. This forms part of its stated rationale for considering the introduction of additional saline groundwater.
Whether the pilot produces measurable and sustainable benefits will ultimately depend on its monitored environmental outcomes.
The wider infrastructure challenge
The groundwater intervention is not the only major project affecting the lagoon's future.
The City is also undertaking a substantial upgrade of the Potsdam Wastewater Treatment Works, with a reported investment of R5.2 billion.
The upgrade commenced in April 2023 and is intended to increase treatment capacity from 47 million to 100 million litres per day. According to the report, new membrane bioreactor filters with a capacity of 65 million litres per day were installed in October 2026, with the overall project approximately 80% complete.
The City expects the full upgrade to be completed in 2027.
Winter acknowledged that the Potsdam upgrade has been a major contributor to the improvements observed in the lagoon, while emphasising that other pollution sources still require attention.
This is a significant distinction. Wastewater infrastructure is central to the lagoon's environmental future, but it is only one component of a much larger catchment management challenge.
The Phoenix Pump Station, sewer infrastructure, industrial stormwater management and agricultural influences in the upper Diep River catchment also form part of the picture.
Environmental recovery requires these interconnected elements to be considered together.
Dredging and the consequences of intervention
Another issue raised in the GroundUp report concerns the proposed dredging of Milnerton Lagoon.
Dredging can form part of waterway management, but its environmental implications depend on how sediment is removed, handled and redistributed.
Caroline Marx of the Milnerton Central Residents Association expressed concern about proposals to redistribute dredged material within the lagoon rather than removing it from the site. She warned that this could create extensive mudflats and change the lagoon's existing character.
The City had previously indicated that environmental authorisation for dredging had been granted, although eight appeals had been lodged. A decision was expected later in 2026, with work potentially beginning in early 2027 if the authorisation is upheld.
The issue illustrates a wider consideration in environmental management: interventions intended to improve one aspect of an ecosystem can influence other aspects in ways that require careful assessment.
The physical appearance of a landscape, its sediment patterns, vegetation and habitat conditions are all part of its ecological character.
Understanding these relationships is particularly important in an environment as geographically and ecologically connected as Milnerton Lagoon.
A photographic perspective: Observation and environmental interpretation
For photographers working around Woodbridge Island, Milnerton Lagoon is more than a familiar coastal location. It is an environment in which natural processes and human activity are continuously visible.
The movement of water, changing tides, exposed sediment, bird activity and the relationship between the lagoon and Table Bay provide opportunities for sustained photographic observation.
Nature photography can contribute to environmental awareness by documenting these changes over time. Individual photographs may capture a particular bird, landscape or water condition, but a developing photographic archive can offer a broader record of a location and its changing characteristics.
This is where observation becomes interpretation.
A photograph of a bird feeding along the lagoon's edge may initially appear to be a straightforward nature image. Understanding the surrounding habitat, water conditions and ecological relationships adds another layer of meaning.
Similarly, landscape photographs can reveal changes in water levels, sediment exposure, vegetation and the relationship between the lagoon mouth and the ocean.
Photography cannot replace scientific water sampling, ecological surveys or professional environmental monitoring. It does, however, provide a complementary visual perspective.
The distinction is important. Photographs should not be presented as scientific proof of water quality or ecological recovery. Their value lies in documenting observable conditions and encouraging closer attention to the environment.
For Vernon Chalmers Photography, this represents an opportunity to connect geographical photography with environmental interpretation. The photographer becomes an observer of place, recognising that understanding a subject involves more than its visual appearance.
The meaning of sustainable environmental recovery
Milnerton Lagoon presents a useful example of the difference between improving an environmental condition and addressing the processes responsible for its deterioration.
The recent water-quality improvements are encouraging. The Potsdam upgrade represents a substantial infrastructure investment, while the groundwater pilot introduces another intervention that will require careful monitoring.
However, the longer-term environmental outcome will depend on whether pollution is consistently reduced at its sources, whether supporting infrastructure performs effectively and whether the wider Diep River catchment receives appropriate attention.
It will also require transparent monitoring and an understanding of how individual interventions influence the lagoon as a connected ecosystem.
The return of fish, seagrass and birdlife may provide visible indications of progress. Yet sustainable recovery must ultimately be evaluated through consistent environmental evidence rather than appearance alone.
Milnerton Lagoon remains an important part of Cape Town's natural landscape. Its future is connected to the management decisions made across the surrounding urban and agricultural environment.
The challenge is therefore not simply to make the lagoon look cleaner or improve an individual water-quality measurement. It is to establish the environmental conditions under which the lagoon can remain healthy over time.
For those who photograph, observe and appreciate this landscape, that distinction matters.
Environmental recovery is not simply the return of a healthier-looking environment. It is the sustained improvement of the ecological processes that allow that environment to function.
