Two-thirds of New Zealand’s freshwater river sites have been deemed ‘ecologically impaired’ according to research. 

This week the Land, Air, Water Aotearoa (LAWA) project has released the LAWA River Water Quality National Picture Summary 2021, alongside updated river monitoring result histories for more than 1500 individual sites across New Zealand.

The release is timely, marking World Rivers Day 2021. This year the global theme is ‘waterways in our communities’ with a special emphasis on the need to protect and restore urban waterways.

Cawthron Freshwater Ecologist Dr Roger Young was part of the project team behind the National Picture Summary. 

Roger explains that while the assessment of current state varies by indicator, there is a pattern of poorer sites generally being in urban and pasture dominated catchments, with pristine rivers usually surrounded by native vegetation.

“Our analysis shows that impaired ecological health is evident at almost two-thirds of monitored river sites in New Zealand,” Roger says. 

“This is demonstrated by the proportion of Macroinvertebrate Community Index (MCI) sites graded attribute band C or D. For these sites, there have been few sensitive macroinvertebrates found through council monitoring, indicating compromised river health.

“New Zealand’s primary indicator of faecal bacterial contamination shows a similarly poor pattern with two-thirds of sites receiving undesirable grades for E. coli.

“The poorest results are found at sites in urban catchments, followed by pasture, then exotic forest. Unsurprisingly, the best ecological health is usually found in streams draining native vegetation.”

The Manuherekia has been rated in the worst 50% of NZ rivers on a range of indicators, including E.Coli, Clarity, Ammoniacal Nitrogen,  Dissolved Reactive Phosphorus, Turbidity and Total Phosphorus. 

It received a C-rating overall for the Macroinvertebrate Community Index, which uses aquatic macroinvertebrates to assess the health of streams in New Zealand. 

A C-rating indicates the Macroinvertebrate community indicates moderate organic pollution or nutrient enrichment. There is a mix of taxa sensitive and insensitive to organic pollution/nutrient enrichment.

The Manuherekia (pictured) has been rated in the worst 50% of rivers in a range of indicators according to LAWA. Photo: The Central App. 

Roger cautions that the National Picture Summary relates to sites where monitoring has been conducted and that these sites are often located in areas at greater risk of degradation from human activities, so are not necessarily representative of all rivers and streams across the country.

The interactive map of New Zealand on the LAWA website shows the geographical spread of state and trend results against freshwater indicators in the National Policy Statement for Freshwater Management (NPS-FM 2020).

LAWA River Quality Lead and Auckland Council Lead Water Scientist Dr Coral Grant says, “Exploring the LAWA website river quality map provides an overview of where the challenges are for each indicator. 

“This reflects our findings that the poorest results are often found in the most modified environments.

“While urban rivers and streams make up only 1% of total river length in New Zealand, they flow through areas of significant land cover transformation and 4 out of 5 monitored urban waterway sites are showing signs of severe pollution or nutrient enrichment.

“It’s positive to see in the results that the toxic effects of nitrate and ammonia on aquatic ecosystems are an issue at only a small percentage of sites. 

“However, nitrogen can also stimulate problematic plant and algae growth at lower concentrations than those causing direct toxicity and the intention is to report further on this as more data and national reporting guidance becomes available,” Coral says. 

River quality data presented on LAWA is collected by New Zealand’s 16 regional councils and unitary authorities, and the National Institute of Water and Atmospheric Research (NIWA).

LAWA Chair and Environment Canterbury Director of Science Dr Tim Davie said the number of river sites with water quality data available on LAWA has increased by around a third since LAWA was launched in 2014.

“Increased monitoring and reporting represents a commitment from regional and unitary councils to enhance environmental data collection which is essential as we move towards putting the health and well-being of water first under the principles of Te Mana o te Wai.

“The LAWA website presents information at a national, regional, and catchment level, as well as the all-important individual monitoring site data, to help us understand the condition of our waterways and how they’re tracking over time.

“This year, individual river site pages have been upgraded to report available data for an increased number of water quality and ecological indicators,” Tim says. 

The new NPS-FM 2020 requires every regional and unitary council, in consultation with its community, to develop a comprehensive plan for maintaining or improving the state of freshwater in the region. 

There are several compulsory measures of the state of a river that must be met, and communities can choose to go above and beyond these.

Hawke’s Bay Regional Council Chief Executive and Ministry for the Environment Freshwater Implementation Group member James Palmer says over the coming years regional councils and unitary authorities will be engaging with communities to develop plans for maintaining or improving the state of local freshwater.

“Data presented on the LAWA website will help to inform upcoming community conversations and be used to track future improvements. 

“While a lot of work has been done in many catchments across Aotearoa, it will take time and sustained effort to bring some of our more compromised rivers to a desired state.

“World Rivers Day seeks to raise awareness of the value of waterways and the threats they face to encourage improved stewardship. 

“Here in New Zealand, we care deeply about the health of our waterways and the data released today by the LAWA project further reinforces how much work lies ahead to restore our rivers,” James says. 

You can use the LAWA online tool for find out more information about your locals rivers.