‘Don’t dive in if it’s been raining hard!’ — warns
November 17, 2010
With the weather warming up, it’s nearly time for a dip at your favourite beach or river swimming hole.
But if there’s been a downpour, think carefully before you dive in, says the Greater Wellington Regional Council.
It advises people to wait for at least 48 hours after heavy rain before taking a dip.
‘Be careful for two days after heavy rain’
“It pays to be careful for the first two days after heavy rain as the rainfall can wash contaminants from agricultural and urban areas into our waterways and coasts,” says the Council’s Environmental Monitoring Manager, Ted Taylor.
During the bathing season (from mid November to the end of March) Greater Wellington, local councils and Regional Public Health work together to monitor water quality at 21 river and 74 beach sites across the Wellington region.
Results are posted on Greater Wellington’s website www.gw.govt.nz/on-the-beaches, using a traffic light system.
Determining the health risk
The health risk is determined from the number of bacteria found in water samples. A green light is for go and means the health risk is low.
River users should also keep an eye out for potentially toxic blue-green algae (cyanobacteria), which may be prevalent during low river flows and warm temperatures. Blue green algae can be fatal to dogs and livestock if eaten, and can make humans sick. Algal cover is assessed weekly during summer at 21 popular river spots throughout the region.
Greater Wellington’s Environmental Monitoring and Investigations Team, with Regional Public Health and local councils, uses a two-tiered warning sign system to advise river users of the risk from toxic algae.
A medium risk sign means users can still swim or walk their dogs but should keep an eye out for algal mats. A high risk sign means people should avoid contact recreation and dog walking in that part of the river.
The warning system is based on river bed coverage and algal mat exposure and follows the interim Guidelines for Cyanobacteria in Recreational Fresh Waters.
More information about toxic algae, including pictures and current warnings, can be found at www.gw.govt.nz/toxic-algae.
If local people see any exposed or easily accessible algal mats, they can contact Greater Wellington (04 384 5708) or the KCDC environmental health officer.