Public Health Hazards When There Is Elevated Bacteria Levels In Recreational Swimming Areas

Paula Martin, Communications Officer ,

Heavy rain events have caused bacteria contamination of popular swimming and seafood gathering locations in Northland.

Northland Regional Council monitors most of the popular swimming spots in the Northland region over the summer season, from the beginning of November to the end of March.

“Testing at the end of last week has indicated bacteria in a number of waterways across Northland, therefore, we strongly advise that people do not swim or gather shellfish where warnings are in place,” noted Northland DHB Medical Officer of Health Dr Jose Ortega Benito.

“It is also important to note that the test results are only a snapshot of conditions at the time of testing, and if there has been heavy rain since it’s likely the water quality will be worse.”

It is also wise not to collect shellfish after heavy rain as storms may flush sewage overflow or farm run-off downstream which contaminates the water. After the water has run clear for a few days, shellfish should be safe to collect again.

“We recommend that people do not swim or collect shellfish after heavy rain events such as the events we have been experiencing in the last few weeks.”

General advice

  • We advise not to swim during the 48 hours after heavy rain (>10 mm rainfall in 24 hours)
  • Look for posted signs at rivers and beaches, and read these signs carefully.  Do not enter the water if there are warning signs in place that advise against swimming
  • Saltwater is generally safer than freshwater, due to the pathogen-killing effect of salt. As far as bacteria and viruses are concerned, the sea is usually safer than a lake, or a river.
  • Moving water is generally safer than still water. So, as far as bacteria and viruses are concerned a river is usually safer than a lake, and seawater on an open coast will generally be safer than seawater in a harbour.
  • Even if the results shown on the website are fine, still check for warning signs posted at the beach when you arrive.
  • Even if there are no warning signs, there may still be some risk. Use common sense, as a range of environmental factors can affect the quality of recreational water. Consider what might flow into the area you intend to swim in such as; stormwater outfall pipes, stormwater run-off, stock waste, failing septic tanks, and boats emptying their toilets.
  • Look at the water for signs of contamination such stagnant, muddy or cloudy water. If the water is cloudy, there is visible scum, an odd smell or colour, or you cannot see your feet in knee-deep water, it may not be safe to swim.
  • Choose clear water for swimming. If you can’t see your feet when you walk in, you shouldn’t be swimming there.


Please also be aware of other natural risks such as stingrays, jellyfish, tidal rips, holes and unexpectedly deep water, especially on the west coast beaches.

You can check your favourite swimming spot at this link link)


For further information contact:

Paula Martin, Communications Officer

Phone (09) 4304101 ext 60519


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