Milnerton Lagoon | Woodbridge Island Pollution Report – January 2026
A Long-Running Environmental Crisis at the Mouth of the Diep River

Introduction"Milnerton Lagoon, located at the mouth of the Diep River where it meets Table Bay in Cape Town, has for decades been one of the city’s most ecologically and socially significant estuarine systems. It supports birdlife, recreational users, nearby residential communities, and forms part of a historically important coastal landscape. Yet by January 2026, the lagoon remains in a chronic state of environmental degradation, characterised by persistent sewage pollution, eutrophication, microbial contamination, and governance failures that have eroded public trust and ecological resilience.
Despite repeated commitments by the City of Cape Town to restore water quality, mitigate sewage spills, and modernise wastewater infrastructure upstream, conditions at Milnerton Lagoon continue to oscillate between poor and hazardous. Independent observations, water sampling reports, and visible pollution events suggest that the lagoon’s problems are not episodic, but systemic. This report examines the state of Milnerton Lagoon as of January 2026, tracing the sources of pollution, assessing ecological and public health risks, reviewing institutional responses, and situating the crisis within a broader context of urban water governance in South Africa.
Water Quality Updates Milnerton Lagoon, Woodbridge Island
Geographical and Ecological Context
Milnerton Lagoon forms part of the Diep River estuary, a dynamic coastal system influenced by tidal exchange, river inflows, and seasonal rainfall. Estuaries are among the most productive ecosystems on Earth, functioning as nurseries for fish, feeding grounds for birds, and natural filters that trap sediments and pollutants (Day et al., 2019). The Diep River catchment extends far inland, passing through industrial zones, informal settlements, agricultural land, and urban suburbs before reaching the lagoon.
Historically, the lagoon supported diverse bird species, including flamingos, pelicans, cormorants, and migratory waders. It also served as a recreational space for anglers, paddlers, photographers, and walkers. However, decades of urban expansion, inadequate wastewater treatment capacity, and poor stormwater management have progressively compromised the system’s ecological integrity (DWAF, 2004).
Sources of Pollution
Sewage and Wastewater Discharges
The dominant driver of pollution at Milnerton Lagoon remains untreated or partially treated sewage entering the Diep River upstream. Wastewater Treatment Works (WWTWs), particularly Potsdam WWTW, have repeatedly been identified as key contributors during periods of plant overload, equipment failure, or emergency bypass events (City of Cape Town, 2023).
As Cape Town’s population has grown, wastewater volumes have increased beyond the original design capacity of several treatment facilities. While upgrades have been announced and partially implemented, monitoring data indicate that effluent quality frequently fails to meet required standards for nutrients, ammonia, and microbial indicators such as Escherichia coli (E. coli) (Green Drop Report, 2022).
Stormwater Runoff and Urban Pollution
Stormwater infrastructure across the Diep River catchment often functions as a conduit for pollution rather than a protective system. During rainfall events, stormwater drains carry litter, hydrocarbons, heavy metals, faecal matter, and organic waste directly into the river and lagoon. Informal connections between sewer lines and stormwater systems further exacerbate contamination, particularly in older suburbs and informal settlements lacking adequate sanitation (Turpie et al., 2017).
Industrial and Agricultural Inputs
Industrial activities upstream, including food processing, manufacturing, and light industry, contribute chemical pollutants and high nutrient loads when compliance monitoring is weak or enforcement inconsistent. Agricultural runoff adds fertilisers and pesticides, increasing nutrient enrichment and promoting algal blooms that deplete dissolved oxygen levels in the lagoon (Allanson & Baird, 2018).
Water Quality Conditions – January 2026
By January 2026, observable conditions at Milnerton Lagoon remain deeply concerning. Discolouration of the water, foul odours, floating debris, and periodic fish kills continue to be reported by local residents and environmental observers. Elevated nutrient concentrations promote eutrophication, resulting in excessive algal growth and hypoxic conditions that stress aquatic organisms.
Microbial contamination remains one of the most critical risks. High E. coli counts indicate ongoing faecal pollution, rendering the water unsafe for full-contact recreation and posing risks to humans, pets, and wildlife (WHO, 2018). Although official water quality updates are periodically released, discrepancies between official statements and on-the-ground conditions have fuelled public scepticism.
Public Health Implications
The health risks associated with polluted urban waterways are well documented. Exposure to sewage-contaminated water can cause gastrointestinal illness, skin infections, respiratory conditions, and more severe outcomes for immunocompromised individuals (Fewtrell & Bartram, 2001). At Milnerton Lagoon, residents report recurring illness among dogs that swim or drink from the water, including vomiting, diarrhoea, and, in some cases, fatal infections.
Children playing near the lagoon and anglers handling contaminated water or fish are particularly vulnerable. The continued presence of pathogenic microorganisms raises serious questions about whether sufficient public warnings, access restrictions, and risk communication measures are in place.
Ecological Consequences
Milnerton Lagoon remains an important bird habitat, but pollution has altered species composition and behaviour. While some opportunistic species persist, sensitive species are increasingly absent. Bioaccumulation of pollutants through the food chain threatens long-term population health, particularly for piscivorous birds (Burger & Gochfeld, 2004).
Repeated hypoxic events and toxic conditions reduce fish recruitment and survival. Benthic invertebrates, which form the base of the estuarine food web, are especially vulnerable to sediment contamination and low oxygen levels. Their decline further destabilises the ecosystem, reducing resilience to future stressors (Whitfield & Elliott, 2011).
Governance and Institutional Response
The City of Cape Town holds primary responsibility for wastewater treatment and stormwater management within the Diep River catchment. Over the past decade, the municipality has acknowledged challenges and announced infrastructure investment programmes aimed at upgrading treatment plants and reducing sewage spills.
However, implementation timelines have repeatedly slipped, and emergency responses often appear reactive rather than preventative. Critics argue that maintenance backlogs, staffing constraints, and budgetary pressures undermine the effectiveness of existing strategies (Auditor-General of South Africa, 2023).
National and Provincial Oversight
The Department of Water and Sanitation (DWS) is mandated to regulate water quality and enforce compliance through mechanisms such as the Green Drop programme. While reports have highlighted non-compliance, enforcement actions remain limited, raising concerns about regulatory capture and insufficient political will (DWS, 2022).
Civil Society and Community Advocacy
Local residents, environmental groups, and independent observers have played a critical role in documenting pollution events and maintaining public pressure. Citizen science initiatives, photographic evidence, and independent water sampling have filled information gaps left by official monitoring programmes.
These efforts underscore a growing mistrust between communities and authorities. Transparency, timely data release, and meaningful engagement are repeatedly identified as prerequisites for rebuilding credibility.
Climate Change as a Risk Multiplier
Climate change compounds existing vulnerabilities at Milnerton Lagoon. Increased frequency of extreme rainfall events overwhelms sewer and stormwater systems, leading to higher spill risk. Conversely, prolonged dry periods reduce river flow, limiting dilution capacity and exacerbating pollutant concentrations (IPCC, 2022).
Sea-level rise and altered tidal dynamics may further disrupt estuarine processes, complicating restoration efforts unless adaptive management strategies are implemented.
Economic and Social Costs
Beyond environmental and health impacts, pollution at Milnerton Lagoon carries economic costs. Declining recreational use affects local businesses, property values, and tourism potential. Cleanup operations, emergency responses, and long-term remediation represent substantial financial burdens that could be mitigated through proactive investment.
Pathways to Recovery
Experts consistently emphasise that restoring urban estuaries requires integrated catchment management, combining infrastructure upgrades with land-use planning, enforcement, and community participation (Baird et al., 2020). For Milnerton Lagoon, key priorities include:
- Accelerated upgrades to wastewater treatment capacity
- Separation of sewer and stormwater systems
- Independent, transparent water quality monitoring
- Enforcement of industrial discharge standards
- Public access to real-time data and health advisories
- Without decisive action, the lagoon risks crossing ecological thresholds beyond which recovery becomes increasingly difficult and costly.
Water Quality Updates Milnerton Lagoon Disclaimer
Conclusion
As of January 2026, Milnerton Lagoon remains a visible symbol of South Africa’s urban water governance crisis. Despite technical knowledge, regulatory frameworks, and public awareness, pollution persists due to systemic failures in infrastructure, management, and accountability. The lagoon’s continued degradation is not inevitable; it reflects choices about priorities, investment, and transparency.
Restoring Milnerton Lagoon will require sustained political commitment, institutional reform, and genuine collaboration with affected communities. Until then, the lagoon stands as both a warning and a test case for whether urban estuaries can be protected in the face of rapid urbanisation and climate change." (Source: ChatGPT 2026)
References
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Auditor-General of South Africa. (2023). Local government audit outcomes. Pretoria: AGSA.
Baird, D., Adams, J. B., & Snow, G. C. (2020). Ecosystem-based management of South African estuaries. African Journal of Marine Science, 42(3), 275–288. https://doi.org/10.2989/1814232X.2020.1785481
Burger, J., & Gochfeld, M. (2004). Marine birds as sentinels of environmental pollution. EcoHealth, 1(3), 263–274.
City of Cape Town. (2023). Wastewater treatment works performance report. Cape Town: Water and Sanitation Department.
Day, J. W., Kemp, W. M., Yáñez-Arancibia, A., & Crump, B. C. (2019). Estuarine ecology (2nd ed.). Wiley-Blackwell.
Department of Water Affairs and Forestry. (2004). State of rivers report: Diep River system. Pretoria: DWAF.
Department of Water and Sanitation. (2022). Green Drop report. Pretoria: DWS.
Fewtrell, L., & Bartram, J. (2001). Water quality: Guidelines, standards and health. Water Quality: Guidelines, Standards and Health, 3–18.
IPCC. (2022). Climate change 2022: Impacts, adaptation and vulnerability. Cambridge University Press.
Turpie, J. K., Marais, C., & Blignaut, J. N. (2017). The working for water programme. South African Journal of Science, 113(3/4), 1–6.
Whitfield, A. K., & Elliott, M. (2011). Ecosystem and biotic classifications of estuaries. Estuarine, Coastal and Shelf Science, 94(3), 211–219.
World Health Organization. (2018). Guidelines on sanitation and health. Geneva: WHO.