8 November, 2013

Monitoring at Canterbury swimming sites about to get underway again

Environment Canterbury will begin their regular summer-season water quality monitoring, with testing to start next week at 51 freshwater and 45 coastal swimming spots across the region.

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 keep 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.

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 Mangamaunu, Gore Bay, Motunau Beach, Leithfield Beach, Woodend Beach, Waikuku Beach, Spencerville Beach, Taylors Mistake, Pigeon Bay, Lake Hood at main swimming beach or Bayliss Beach, Lake Clearwater, Lake Camp, Lake Opuha at the dam boat ramp, 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 immediately 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 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. Warnings are posted online http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx and a sign erected at the site.

Sites where cyanobacteria mats have occurred previously will soon have signs set up providing information on what to look out for.

For details on water quality for swimming go to:
http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/check-swimming-water-quality.aspx
http://www.facebook.com/canterburyrecwater

For information on cyanobacteria go to
http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx
http://www.facebook.com/canterburyrecwater

Background:
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 may vary from week to week depending on local conditions like 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

ENDS

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