Recent testing of 50 Christchurch sites found all failed at least one of the bacterial, heavy metals or sediment standards. Photo: 123RF
New Zealanders are being urged to think twice about what's going down their drains ahead of the summer swimming season.
Popular beaches in Canterbury's Whakaraupō Lyttelton Harbour were deemed unfit for swimming last summer, partly due to contaminated stormwater.
Recent testing of 50 Christchurch sites found all failed at least one of the bacterial, heavy metals or sediment standards, the regional council's surface water science manager Dr Elaine Moriarty said.
"A lot of people don't realise that what falls on our streets and our roads and our gardens goes straight into our rivers," she said.
"So if there's anything in the path of that, be it dog poo, or rubbish or paint brushes that get washed in the tap outside - they all just flow straight into our rivers. There's no filter or anything like that."
All but three of the sites failed the safe E-coli standard.
Bacteria levels were especially important when it came to testing for safe swimming levels.
"E-coli is kind of like a red flag, it indicates that there could potentially be an issue. As a comparison, your dog poo that you pick up off the road - even if there's one gram of that left, that has a million E-coli in it."
The council found human and animal waste was a major contributor to ruling some of the region's beaches unfit for swimming last summer.
A clean up organised at Christchurch's Ōpāwaho Heathcote River in May saw more than two tonnes of rubbish removed and taken to landfill, Moriarty said.
"Over 300 dog poos they picked up, a barbecue, a Christmas tree - one of the shiny, sparkly plastic ones - road cones, plastics,"
Christchurch City Council was also pulling a few electric scooters or bikes out of rivers every two weeks.
"Everything you could imagine ends up there, along with our beautiful taonga species. Our eels, fish, our inanga that people love for their whitebait sandwiches - they're all in there as well, competing with that rubbish."
The problem was not unique to Canterbury either, with pollution of waterways occurring across the motu.
Everyone can help improve the water quality, Moriarty said.
"If you're out for a walk with your dog, just pick up the poo and put it in a bin. If you need to wash your car, bring it to a carwash or wash it over the grass, just not on your driveway because all those [soap] suds and dirt and everything just goes straight down into the stream.
"It's kind of like washing your dinner plates over your fish tank."
People could also ask their mechanic about fitting brake pads with low copper levels next time their car was in the shop or use a special paint to seal heavy metals into their roofs, so they didn't run out with the rain, Moriarity said.
If anyone saw something blocking or running into a stormwater drain, they could use the Snap Send Solve app to alert the local authorities wherever they are in the country, she said.