Water quality on 
Norfolk Island

This brochure has been co-designed with collaborators from 
Norfolk Island, to explain the key findings of our Norfolk Island 
Water Quality Assessment Technical Report.


Credit: Rob Ryan



The ocean around Norfolk Island is home to vibrant and unique marine 
ecosystems. The cultural, historic, ecological, and economic value of the 
coral reefs is recognised and protected by the Norfolk Marine Park. 
The park spans over 188,000 square kilometres, with no-take areas in 
place to safeguard biodiversity. 

Yet over the past decades, marine experts and community members alike have raised concerns about the declining health 
of the reef near the island, and the delicate ecosystems it supports. Norfolk Island’s nutrient run-off and declining water 
quality have been linked to reduced coral cover and disease outbreaks in the lagoon. 

In 2019, CSIRO – Australia’s national science agency – was commissioned by the Australian Government to assess Norfolk 
Island’s water resources. This research was expanded in 2021 to monitor water quality and develop guideline values for 
contaminants, to help protect the marine ecosystem around Norfolk Island. 

Water flows above and below ground

On Norfolk Island, water can flow into the 
ocean via overland flow or streamflow, or 
through the soils and aquifers underground.

Surface water – from creeks and overland flow – can 
discharge directly into Emily Bay. This happens when 
enough surface water accumulates to move the sand that 
plugs up the creek at the beach between rainfalls. When it 
rains, a greater volume of surface water is flushed into the 
ocean, carrying excess nitrogen from the land. 

Groundwater is hidden below ground and can flow 
in different directions before discharging into creeks, 
wetlands and the bays. Over longer periods of time, rain 
can influence groundwater levels and flows. But generally, 
a single rainfall won’t have a big impact on how much 
groundwater is discharged. 

Contaminants from the island 
wash into the ocean

As they flow towards the ocean, both surface and 
groundwater pick up contaminants from a range of human 
activities and land uses on the island. Acid sulfate soils – 
which can lead to reduced pH, less oxygen in the water, and 
the release of heavy metals – also threaten water quality. 
From 2021, our researchers began monitoring water quality 
at several sites on and around Norfolk Island. 

They analysed seawater from the Norfolk Marine Park, 
surface water in Watermill Creek and Town Creek, and 
groundwater across the southern part of the island. They 
also measured seawater quality in places with little to no 
impact from the island. These are our reference sites, to 
compare with places polluted by contaminants. 

The main contaminant our researchers detected was 
nitrogen. Soils naturally contain a certain amount of 
nitrogen. But human activities like fertilising plants, rearing 
animals and processing sewage can all add extra nitrogen 
to the soil and water. 

On Norfolk Island, contamination from nitrogen-rich 
human, dog, cattle and bird (e.g., chicken and duck) waste 
was detected in the surface water. Only human waste was 
detected in the groundwater. Based on current land use, 
cattle manure, failing wastewater systems and fertiliser are 
the largest potential sources of excess nitrogen on 
the island. 


Water quality is poorer at Slaughter and Emily Bays than at 
Cemetery Bay. Under baseline and rain event conditions, 
Slaughter and Emily Bays have a higher percentage of water 
quality measurements that exceed site-specific guideline values 
(SSGVs for protecting 95% of species from toxicants) compared 
to Cemetery Bay. 

Key points:

Water flowing from 
the island carries 
contaminants like 
excess nitrogen into 
the ocean. 

As of 2026, Emily 
Bay and Slaughter 
Bay are most 
affected, especially 
after rain.

Higher levels of 
nitrogen harm the 
health of coral reefs 
and marine life. 

Community, 
industry and 
government can act 
together to protect 
the reef. 


Contaminants harm marine 
life and ecosystems

Even though nitrogen occurs naturally in soils, too much 
entering the ocean at once can cause disease in corals and 
overgrowth of algae. As algae takes up more space on the 
reef, it stops coral from growing back. Over the long term, 
this damages the health of the marine ecosystem, because 
lots of species rely on corals to thrive. 

Improving water quality helps coral reefs be healthier and 
more resilient to the combined impacts of climate change 
and contaminants. Reducing the flow of contaminants into 
the ocean from the island gives local reefs the best chance 
of recovering from rising sea surface temperatures, which 
are causing coral bleaching all around the world. 

What happens next?

Changing rainfall patterns and warming sea temperatures 
are likely to increase the pressures on Norfolk Island’s 
coral reef ecosystem. Improving water quality from the 
Island’s surface and groundwater will help corals to better 
withstand and recover from marine heatwaves and extreme 
rainfall events. A coordinated suite of actions to manage 
contaminants like nitrogen, and to prevent it from entering 
surface water, groundwater and the ocean, will help to 
produce a sustainable long-term improvement in water 
quality and ecosystem health. Various investigations and 
studies have already been undertaken to progress this. 
Upgrading wastewater management systems, continuing 
scientific monitoring, and works to protect waterways and 
their banks are among the actions being undertaken by 
governments and agencies. Success requires coordinated 
action, supported by scientific evidence and funding to 
implement measures to improve water quality. Continuing 
to monitor water quality is also critical to determine the 
effectiveness of different management strategies, and to 
help understand whether water quality is improving over 
the long-term.

Acknowledgements

The creation of this brochure was funded by Parks Australia, 
and the water quality monitoring was funded by the 
Commonwealth Department of Infrastructure, Transport, 
Regional Development, Communications, Sport and the 
Arts. We thank our colleagues from the Department, Parks 
Australia, Norfolk Island Regional Council, the University 
of Newcastle, the University of New South Wales, and 
numerous individuals from the Norfolk Island community 
for their contributions to the design and production of this 
brochure. Images were supplied by Rob Ryan, Neil Tavener, 
Rob Fitzpatrick, Alex McGillycuddy and Susan Prior.



Environment Research Unit
Joanne Vanderzalm
+61 8 8303 8505
joanne.vanderzalm@csiro.au
csiro.au/niwqa

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solutions for a productive, sustainable and secure future. 
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