New research shows wildfowl such as ducks and Canadian geese are the biggest contributors to faecal contamination in Christchurch’s waterways, and that following rainfall human and dog faeces can also be present.
The research, which was undertaken by the Institute of Environmental Science and Research Limited (ESR), investigated the sources of faecal contamination in the Avon River/ Ōtakaro, Heathcote River/Ōpāwaho and the Estuary of the Heathcote and Avon Rivers/Ihutai.
Canterbury Medical Officer of Health Dr Alistair Humphrey, says the sampling provided further evidence that Campylobacter and E.coli bacteria are at levels that can be harmful to human health.
Unfortunately the quality of water in our city’s waterways is poor. E.coli levels usually exceed recreational water guidelines during normal weather conditions, and after rainfall the water is always unsafe," Dr Humphrey says.
"No one should swim in, or consume food from, these waterways. Recreational river users such as rowers should always avoid the waterways 48 hours after rainfall, and always wash their hands and equipment thoroughly after being in contact with the water."
Christchurch City Council's water manager Tim Joyce says while rain has always put pressure on our city’s stormwater and wastewater drainage systems, progress is being made on reducing the amount of wastewater that overflows into waterways.
"While there have only been two actual wet weather overflows from our network in either the Avon or Heathcote in the last 18 months, in some areas of our city it’s likely that stormwater is being contaminated after coming into contact with the wastewater system after rainfall, contributing to the contamination of our waterways," Mr Joyce says.
"SCIRT is making great progress rebuilding the city's earthquake-damaged wastewater and stormwater network and will have its work complete by the end of 2016. This will help reduce the contamination in our waterways after rain," he says.
"The Council has allocated $75 million to improve the wastewater system so it performs better after rainfall. A recently completed ’post SCIRT’ rebuild wastewater model is being used to determine how those funds can be used to the greatest effect."
Dr Humphrey says the solution to healthier waterways is in the hands of the community.
"Dog owners need to pick up after their dog every time. No matter where you are in Christchurch, if you don’t pick it up it will end up in a river after rainfall.
"Another way people can make our rivers cleaner is by not feeding non-indigenous ducks. The more we feed ducks the bigger their population becomes, and the more of their faeces ends up in our rivers.
"In early 2016 the Council will start consulting on its Three Waters Strategy and it’s important the community are clear about their expectations, and what they are prepared to pay, when it comes to recreational water quality," Dr Humphrey says.
As part of the research water samples were taken from nine locations between April 2015 and September 2015:
The highest levels of
E.coli was observed at the Antigua boatsheds, mostly from wildfowl (such as ducks and Canadian geese). Following heavy rainfall
E.coli also came from dog and human faeces.
Kerrs Reach and Catherine Street were the only two locations where human sewage was found during normal weather conditions. In every other location human sewage was only detected after rainfall.
After rainfall sheep and cow faeces were detected in samples taken from the Heathcote River.
The research was jointly funded by the Ministry of Health, Environment Canterbury, Christchurch City Council and the MBIE funded Clean Water Productive Land research programme.
The reports are available on the ESR Water Quality website.
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