Heavy rain can affect water quality in the Mahurangi Harbour and increase health risks for swimming and shellfish gathering.
What affects water quality
During heavy rain, wastewater can overflow into Mahurangi River from an engineered overflow point An outlet designed to release untreated sewage when the system is overloaded by heavy rain or blocked. in Warkworth. These overflow points are there to stop wastewater from entering:
- homes
- parks
- businesses.
Watercare is investing $450 million to improve the wastewater system in Warkworth. This work will reduce wastewater overflows during wet weather.
Some recent upgrades include:
- opening the new Snells Beach wastewater treatment plant and connecting infrastructure
- installing new pumps and a larger pipe across the heritage bridge
- improving the wastewater network to reduce the amount of stormwater entering the system.
For more information, check Warkworth wastewater scheme.
Health and safety advice
Shellfish warning
Do not collect or eat shellfish from Mahurangi Harbour. They may contain harmful:
- bacteria
- viruses
- toxins.
Shellfish can collect and store contaminants, so eating them can make you sick. Cooking can reduce some risks but does not remove all toxins.
Commercial shellfish growers follow strict rules and are regulated by the Ministry for Primary Industries. They only collect shellfish when it is safe.
If you feel unwell after eating shellfish:
- call Healthline on 0800 61 11 16 for advice
- get medical help if your symptoms are severe
- contact your GP or your local public health unit
- keep any leftover shellfish in case testing is needed
- check shellfish biotoxin alerts.
Swimming safety
Do not swim in:
- Mahurangi Harbour for 48 hours after heavy rainfall
- Mahurangi River at any time.
During dry weather, water quality is usually good and swimming at beaches in Mahurangi Harbour carries a low risk.
Contact with contaminated water can cause eye, ear, nose or skin infections or gastroenteritis (nausea, vomiting and diarrhoea).
Most people recover without treatment. If you need advice, call Healthline on 0800 61 11 16 or contact your GP.
Water quality testing
Water quality testing at Mahurangi beaches usually meets the guidelines for swimming. These beaches include:
- Scott’s Landing
- Opahi Bay
- Sullivans Bay.
Swimming in the Mahurangi River is not safe, especially near the Warkworth jetty. Warning signs are in place.
For the latest water quality information for Auckland beaches, visit Safeswim.