Water quality monitoring

The Taranaki Regional Council undertakes microbiological water quality monitoring at a number of river sites around Taranaki during the summer months.

The montoring is undertaken to:

  • Assess the water quality of popular bathing sites in Taranaki.
  • Compare bathing water quality in Taranaki with national guidelines for contact recreational use of water.
  • Monitor trends in bathing water quality over time.

Freshwater quality monitoring

Coastal water quality monitoring

Freshwater quality monitoring

Bacteriological monitoring

Bathing water quality is assessed according to concentrations of indicator bacteria. For freshwater river sites, this is a type of bacterium known as Escherichia coli (E. coli), which is an indicator of faecal contamination. If there is faecal contamination there is a possibility of the presence of disease-causing organisms such as bacteria, viruses and protozoa. These organisms may pose a health hazard when the water is used for recreational activities such as swimming, board riding and other high-contact activities. Poor recreational water quality can possibly cause gastrointestinal illness and respiratory health effects, such as coughs and colds.

A high concentration of the indicator bacteria means that it is more likely that disease-causing organisms are present. It does not mean that anyone swimming in the water at the time will actually be affected.

Water quality safety is assessed and reported according to the Ministry for the Environment and Ministry of Health 'Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas' revised and issued in 2003.

These guidelines categorise recreational bathing sites into one of three 'mode' categories according to single sample results of E. coli (freshwaters). These categories are:

map-marker-green
Acceptable risk - surveillance mode
Less than 261 E. coli/100ml in single sample.
map-marker-amber
Acceptable risk - alert mode
261 - 550 E. coli/100ml in single sample.
map-marker-red
Unacceptable risk - action mode
More than 550 E. coli/100ml in single sample.
map-marker-red
Unacceptable risk - action mode
High cyanobacteria risk. More than 1.8mm³/litre in single sample.

 

Cyanobacteria monitoring

Cyanobacteria, or blue-green algae, are very small organisms with characteristics in common with both bacteria and algae.

An example of benthic (attached) CyanobacteriaSome cyanobacteria species can produce natural toxins known as cyanotoxins which if produced in high enough concentrations can pose a threat to human and animal health when consumed or by contact during recreational activities.

Someone who is affected by cyanobacteria could have skin irritation, nausea, headaches, flu-like symptoms or tingling and numbness around the mouth or tips of fingers. Exposure to cyanobacteria could also aggravate hay fever, dermatitis, eczema and asthma. If toxin levels are very high, involuntarily or accidentally drinking the water could result in severe liver damage.

An example of planktonic (free-living) CyanobacteriaCyanobacteria occur naturally in freshwater lakes and rivers, and are found in a wide range of water quality conditions, including relatively 'healthy' waters. Under certain conditions blooms can result, increasing risk to humans and animals. Taranaki rivers and lakes are at times affected by both attached and free-living cyanobacteria blooms. Attached (benthic) forms of cyanobacteria can appear as dark brown or black mats covering the river bed. Free-living (planktonic) cyanobacteria blooms can cause discolouration and give water a turbid or thick, soupy appearance. Avoid using areas if you suspect toxic cyanobacteria are present in large numbers. Cyanobacteria mats can pose a risk to dogs who may eat algal mats, or ingest algae when they drink water from a watercourse, so please remain vigilant of cyanobacteria mats that may develop in shallow areas of a river.

The Taranaki Regional Council monitors summer planktonic cyanobacteria levels at Lakes Rotomanu, Ratapiko, Rotokare and Opunake, and benthic cyanobacteria in the Oakura, Waiwhakaiho, Manganui, Patea, and Waingongoro Rivers and Te Henui and Kaupokonui Streams.

There are three Ministry for the Environment alert levels:

Alert level 
Planktonic cyanobacteria
(cells/ml OR mm³/litre)
Benthic cyanobacteria
(% coverage)
Low risk 
Less than 2,000 OR less than 0.5
Up to 20%
Medium risk 
 2,000 to 15,000 OR 0.5 to 1.8
20% to 50%
Elevated risk 
More than 15,000 OR more than 1.8
Above 50% 
AND/OR exposure of mats/scum

 

Coastal water quality monitoring

Bathing water quality is assessed according to concentrations of indicator bacteria. For marine beach sites this is enterococci bacteria. These bacteria are indicators of faecal contamination. If there is faecal contamination there is a possibility of the presence of disease causing organisms such as bacteria, viruses and protozoa. These organisms may pose a health hazard when the water is used for recreational activities such as swimming, board riding and other high contact activities. Poor recreational water quality can possibly cause gastrointestinal illness and respiratory health effects, such as coughs and colds.

A high concentration of the indicator bacteria means that it is more likely that disease-causing organisms are present. It does not mean that anyone swimming in the water at the time will actually be affected.

Water quality safety is assessed and reported according to the Ministry for the Environment and Ministry of Health 'Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas' revised and issued in 2003.

District Councils will inform the public when the action levels are reached based on national guidelines and the advice of the Medical Officer of Health.

These guidelines categorise recreational bathing sites into one of three 'mode' categories according to single sample results of enterococci (marine waters) bacterial counts. These categories are:

map-marker-green
Acceptable risk - surveillance mode
Enterococci/100ml - No single sample greater than 140.
map-marker-amber
Acceptable risk - alert mode
Enterococci/100ml - One single sample greater than 141.
map-marker-red
Unacceptable risk - action mode
Enterococci/100ml - Two consecutuive single samples greater than 280.

 

The safety category is reassessed after each additional sample is collected. Sites on the environmental data maps reflect the coloured safety category and level of compliance with the guidelines at the time of the most recent sample.

In Taranaki, it is known that significant rainfall events substantially increase bacterial levels in rivers and streams (and subsequently in coastal waters along the shoreline) due to rural and urban runoff for up to several days after rainfall. This may increase numbers into the Action mode category for recreational usage.

The results of the water samples collected from fresh water and coastal sites during the bathing season are updated on this site as they are received from the laboratory.