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Water quality and cyanobacteria monitoring

15 November 2012

Water quality and cyanobacteria monitoring at Canterbury swimming sites

Environment Canterbury will begin water quality monitoring at 51 freshwater and 45 coastal swimming spots – from Kaikoura to the Waitaki catchment – starting next week.

This summer Environment Canterbury staff and three university students – two in Christchurch and one in Timaru - will take the water samples and keep an eye out for cyanobacteria mats each week for 15 weeks. The results are updated weekly on the Environment Canterbury website - http://maps.ecan.govt.nz/WaterQuality/

The best water quality for swimming and other water recreation, showing as blue spots on the swimming water quality maps, are Gore Bay, Motunau Beach, Leithfield Beach, Woodend Beach, Waikuku Beach, Spencerville Beach, Taylors Mistake, Pigeon Bay, Lake Hood at main swimming beach, Lake Clearwater, Lake Camp, Lake Opuha at the dam boat ramp or recreation reserve, and Timaru Yacht Club.

Many other sites are graded as good for swimming with a green spot on the map.

However, even good swimming sites should be avoided during or shortly after heavy rainfall, which can wash contaminants off roadways, gutters and farmed land into the river or sea and temporarily affect the water quality.

At the freshwater river sites the council will also be on the alert for mats of cyanobacteria (blue-green algae) species such as Phormidium, which can produce toxins that are dangerous to humans, stock and dogs. There is a greater risk of potentially toxic cyanobacteria mats occurring during periods of low river flow and warm temperatures. People are warned to look out for areas of rivers where black cyanobacteria mats are growing or forming scums. They should be particularly careful to keep children and dogs out of these waters and avoid swimming in heavily infested areas. Mats can be attractive to dogs due to their odour and they can cause serious illness or death if licked or ingested.

At sites where cyanobacteria mats are found, a detailed survey will be undertaken by Environment Canterbury staff. The survey results are compared to national guidelines and if trigger values are exceeded a warning is issued for a site. A warning will be posted on http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx and a warning sign erected at the site. At sites where cyanobacteria mats have occurred in the past there will soon be information signs telling people what to look out for.

For more information: Lesley Bolton-Ritchie, Environment Canterbury Coastal Water Quality Scientist – 0272810822 or Michele Stevenson, Environment Canterbury Water Quality Scientist (rivers and lakes) 0275497703 or David Kelly Environment Canterbury Water Quality Scientist (re cyanobacteria) 0275497704

For information on water quality for swimming go to


For information on cyanobacteria go to



Water samples are sent to Hill Laboratories in Christchurch for testing. Laboratory staff test the weekly water samples for faecal indicator bacteria (E. coli in fresh water and enterococci in sea water) which are found in faecal material and can indicate the presence of sickness-causing bacteria, viruses and protozoa.

Results go back to the monitoring officer, who reports results that are above trigger values specified by the national guidelines to the relevant district council and Community and Public Health protection officers. It is the district or city council’s responsibility to put up signs when required, warning people that a beach or river is not suitable for swimming.

The coloured grades shown on the website map are based on up to five years of monitoring data and a risk analysis of possible nearby pollution sources. The overall grades are set in November each year and do not change during summer, although the weekly indicator bacteria readings vary from week to week depending on local conditions such as heavy rainfall.

The swimming water quality map is at http://maps.ecan.govt.nz/WaterQuality.

Website users are encouraged to explore the website for more information on how and why we monitor recreational water quality, including cyanobacteria blooms in rivers and lakes, at http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/pages/default.aspx


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