Citizen Scientists help nurse Kaiwharawhara Stream back to health

Wellington’s Kaiwharawhara Stream might be polluted now, but citizen scientists are helping restore it to health.  

In a recent survey of the stream’s estuary by Sustainable Coastlines, 2400 pieces of mostly plastic rubbish, were collected and analysed by volunteers. Coastal clean-ups, such as those coordinated by Sustainable Coastlines, have inspired the Kaiwharawhara Catchment Plastics Project, led by Dr Amanda Valois of NIWA. 

“There’s a lot of interest in New Zealand about the amount of plastics on beaches and in marine animals, but the rubbish is coming from the land and it is carried there by rivers. In the Plastics Project we are trying to figure out where the stream is picking up all this plastic, and what it is doing to it.” 

On 20 July, Amanda held a workshop at ZEALANDIA for people to sort and analyse plastic litter collected in the Kaiwharawhara from stormwater filters.  

With support from Wellington City Council, Amanda is working with existing community groups and other volunteers to periodically empty special filters called ‘LittaTraps’. These are baskets installed at the grids in street gutters which collect all rubbish, even very small pieces of plastic. She is training volunteers to audit the plastics collected and identify key plastic pollution sources and pathways.  

“I would love the Kaiwharawhara catchment to become a model catchment for studying plastic pollution from a community perspective where everyone comes together and makes a plan to reduce it. This is a difficult task at a national level and working in catchments can effect real change.” 

The Kaiwharawhara Stream has its source at ZEALANDIA, where it is most healthy. By the time the stream weaves its way through suburban and industrial Wellington, emerging into the harbour, it contains rubbish and contaminants. 

The Kaiwharawhara catchment is the largest stream system in Wellington City. It is also an important awa for mana whenua, Taranaki Whānui te Upoko o te Ika. Research with Taranaki Whānui will help develop a cultural monitoring framework that includes plastics and assess the impacts on Māori cultural values. 

Taranaki Whānui are also a key part of the solution. Terese McLeod (Taranaki Whānui) realised some of the plastic flowers placed on graves at urupā/ cemeteries were ending up in rivers. She is encouraging members of her iwi, both in Taranaki and Wellington, to consider biodegradable alternatives. 

Other sources of pollution 
 

Plastic isn’t the only thing polluting the Kaiwharawhara and of concern to ZEALANDIA’s ‘Sanctuary to Sea/Kia Mouriora te Kaiwharawhara’ project.  

Other sources include roof and building material found in urban areas. For example, fragments of the polystyrene used as building insulation can easily find its way to the stream. 

Wastewater is another important source of pollution. Contamination of stormwater can occur through cross-connections, from leaking wastewater pipes, and from overflows when the wastewater system becomes overloaded or fails. Over the last 25 years, efforts have been made to remedy this, including checking and repairing cross-connections, and fixing known wastewater pipe faults. As part of the Sanctuary to Sea project, ecological engineer Stu Farrant, of Morphum Environmental Ltd, is mapping stormwater infrastructure to highlight hot-spots for future work in upgrading or retrofitting improvements. 

Run-off from road surfaces and pavements includes pollution from vehicles (tires, brake linings, oil leakage, and exhaust). The Kaiwharawhara catchment includes major roads, shopping areas and industrial parking lots, all with high traffic volumes. The Wellington to Hutt and Porirua motorways are pollution hot-spots with SH 1 having an average daily traffic count in excess of 50,000 vehicles. 

Sedimentation is another threat to stream health, and it has increased recently due to land clearance, particularly for new housing developments. Sediment is washed out into the harbour through heavy rain events. Sedimentation in the Kaiwharawhara Stream is estimated at 1300 tonnes per year and is contributing to a high load in the harbour (2200 tonnes per year). Sediment in urban and industrial environment is often contaminated with heavy metals. The Kaiwharawhara stream is piped under disused landfills, which were known to have contributed to elevated concentrations of arsenic, lead, zinc and other metals in stream sediments in the past, traces of which remain. 

There are many opportunities for citizen scientists to become involved in catchment projects, for example through monitoring stream health. Last year, Greater Wellington Regional Council (GWRC), trained community restoration groups in the Kaiwharawhara catchment to undertake freshwater monitoring using a Stream Health Monitoring and Assessment Kit (SHMAK). This tool was developed by NIWA as part of a nationwide project to monitor water quality in streams and rivers. People can monitor a section of a stream to assess biodiversity and environmental conditions over time.  

So, how is your stream? Do you know what goes into its water? You can help by being part of a citizen science project, joining a clean-up day with your local council or reducing your plastic waste.