Household and vehicle contaminants pouring into stormwater systems and polluting Christchurch waterways could take generations to clean up, new research shows.
Data collected by the city council for the Avon Stormwater Management Plan shows the waterway contains harmful contaminants affecting the river and human health.
Experts say it is a wake-up call to city residents that the finger should not just be pointed at farmers for polluting waterways - anyone who drives a car or lives in a house has responsibilities.
The "worst sites" in the city with indicators showing human waste exceeding safe levels are Dudley Creek, Riccarton Stream and the Avon at Manchester St.
Sites exceeding safe levels for water quality, with nitrates, phosphorous, dissolved oxygen, zinc, copper and ammonia were Dudley Creek, Riccarton Stream, the Avon at Mona Vale, Waimairi Stream, Horseshoe Lake and Addington Brook. Maps of the catchment showed the Addington area scored high in petroleum hydrocarbons, copper and zinc.
City council unit manager, natural environment and heritage, Helen Beaumont, said E. coli from human waste was entering waterways as a result of the earthquakes rupturing pipes.
Freshwater ecologist Professor Ian Hawes said the source of many contaminants was from everyday sources, which few people realised.
"Everyone who drives a car has zinc from brakes which then go on to the road. That is washed off the road into the stormwater drains, which goes into the estuary.
"It is the same for everyone who lives in a house. If you have a galvanised roof or copper pipes, contaminants slowly wash off through rain and go into the stormwater," said Hawes.
The Christchurch-West Melton Zone Committee, which requested the information, said the results would shock householders.
Chairman Ian Fox said: "Focus has been on what dairy farmers contribute to water quality but people in urban areas are also harming waterways . . . which could take generations to repair.
"Is it possible to get it clean? Yes it is. Is it going to be easy? No, and that is because we have 350,000 people living here.
"We have had 160 years of messing up our waterways. Now we all have a part to play in cleaning them up."
Beaumont said the focus was now on reducing contaminants, then treatment of stormwater.
The sites that were cleaner include the airport catchment, Wairarapa Stream and Waimairi Stream.
"Urban waterways are a challenge - there is an intense duck population, cats and dogs and all the road runoff.
"But we can do good housework by not putting paint down the drain and thinking, where is this water going to end up," she said.
To view an interactive history of the Avon River, click here.
- The Press
Which would you prefer?Related story: Natural burials the way to go
The cost of losing nature