A NIWA scientist has embarked on a first-of-its-kind study to track down sources of the plastic that ends up in New Zealand waterways.

Photo: 123RF

National Institute of Water and Atmospheric Research (NIWA) freshwater ecologist Amanda Valois will assess rubbish collected from Kaiwharawhara Catchment in Wellington.

Dr Valois will be sorting through rubbish to find its major sources and to come up with ways to stop it from getting into waterways.

The study was inspired by volunteer beach clean-ups across the country.

It was inefficient to clean up plastic once it was in the ocean, Dr Valois said.

"If we can actually stop it at the source it'll be much more useful. But we don't know if these major sources of plastic.

"Is it from people littering? Or is it during a windy day if you put your recycling out and it all blows into the river? Is it from the storm water? Or is it from waste water?"

Sampling the plastic rubbish would be quite simple as it floated along the water, Dr Valois said.

Photo: Supplied.

Litter surveys will be conducted as part of the study and during stormy weather nets will be put in place to figure out how much plastic is going from the river to the ocean.

Community groups and iwi will be involved in the three-year long study.

"There are a lot of great groups out there that are working to clean up the stream," Dr Valois said.

"[They will be] planting vegetation, looking at the fish community and even doing rubbish surveys. So we want to work with them to help look at what type of plastics that we can find either in the stream or nearby the stream and monitor them over time."

The study would also assess the impacts of plastics on Māori cultural values, Dr Valois said.

"I would love the Kaiwharawhara catchment to become a model catchment for studying plastics from a community perspective where everyone comes together and makes a plan to reduce it.

"This is a difficult task at a national level but working in catchments can effect real change."

Dr Valois will be documenting her finds, including the more unusual ones, on social media.