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The Taranaki Regional Council undertakes microbiological water quality monitoring at a number of popular beach and river sites around Taranaki during the summer months (November to March) 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.
Taranaki bathing water quality
Bacteriological
Bathing water quality is assessed according to concentrations of indicator bacteria. For freshwater river sites the indicator is a type of bacterium known as Escherichia coli (E. coli) and for marine beach sites it 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.
These guidelines categorise recreational bathing sites into one of three 'mode' categories according to single sample results of E. coli (freshwaters) and enterococci (marine waters) bacterial counts. These categories are given below:
Freshwater
(E. coli/100ml)
|
Mode |
Marine
(enterococci/100ml) |
| No single sample greater than 260 |
Surveillance/Green |
No single sample greater than 140 |
| One single sample between 261 and 550 |
Alert/Amber |
One single sample between 141 and 280 |
| One single sample greater than 550 |
Action/Red |
Two consecutive single samples greater than 280 |
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The safety category is reassessed after each additional sample is collected. Sites on the 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. However, for trend detection purposes the Taranaki Regional Council does not sample river and beach waters within 3 days of any significant rainfall event.
However, several sites have been scheduled in the 2007/2008 recreational water quality monitoring period for an additional seven samples to be taken, thus totalling twenty samples for the monitoring period for those sites. These extra seven samples will be taken irrespective of weather conditions.
The purpose of this additional sampling is to compare the effect of non-weather dependent sampling with existing state of the environment protocols. |
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If elevated bacterial levels in rivers and coastal waters unrelated to high rainfall events are detected, extra sampling and/or investigations may be undertaken to determine the cause of the unusually high counts.
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.
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Cyanobacteria
Cyanobacteria, or blue-green algae, are very small plant-like organisms found in freshwater lakes and rivers where they can build up to very large numbers under certain conditions.
Cyanobacteria can cause skin irritation, and some species contain toxic substances and have been linked to negative effects on human and animal health.
They can cause nausea, stomach upsets, and tingling and numbness around the mouth or tips of fingers. If toxin levels are really high, involuntarily or accidentally drinking the water could result in severe liver damage.
The Taranaki Regional Council is monitoring summer cyanobacteria levels as well as bacteriological levels at Lake Rotomanu, the Waiwhakaiho River at Merrilands, Lake Ratapiko, Lake Rotokare and Lake Opunake.
There are three alert levels:
- LOW RISK if sampling reveals less than 2,000 cyanobacteria cells per ml of water.
- MEDIUM RISK if sampling reveals between 2,000 and 15,000 cyanobacteria cells per ml of water.
- HIGH RISK if sampling reveals more than 15,000 cyanobacteria cells per ml of water.
HIGH RISK will be denoted on the bacteriological water quality map with a thick red cross in the square at the relevant monitoring site.
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