Q&A: LAWA River Water Quality National Picture Summary 2021

The LAWA project is part of a wider programme to improve environmental monitoring and reporting in New Zealand. As the project and technology has evolved, so have opportunities to generate and share more information.

We now publish an annual River Water Quality National Picture Summary of state, and this year we have been able to break this down by land cover and how state is changing over time.

What does the LAWA River Water Quality National Picture Summary 2021 tell us about river health?

The summary presents a high-level aggregated picture of the current state of our rivers and streams, how state compares among different land cover types, and how state has changed over time.  For the national level analysis, the LAWA team focused on six indicators from the new NPS-FM 2020:

  • Macroinvertebrate Community Index (MCI) – A biological indicator of ecosystem health
  • Ammonia and nitrate toxicity - Nutrients that can be toxic to in-stream life
  • Dissolved reactive phosphorus (DRP) – A nutrient which can lead to problematic in-stream algal growth
  • Suspended sediment which affects the clarity of the water
  • E. coli – A faecal bacteria indicator of safety of water for human contact


At a national level, two-thirds of MCI monitored sites are classified in a C or D band – indicating that they’re ecologically impaired. The toxic effects of nitrate and ammonia on aquatic ecosystems are an issue at only a small percentage of sites so it’s not likely that such toxicity is driving the widespread ecological health impairments. E. coli monitoring results show a similar pattern to MCI with two-thirds graded band D or worse. Overall, the state of monitored sites is relatively consistent over the past 10 years at a national level.

How does the state of our rivers vary by different land cover types?

For most indicators, there is a clear pattern between compromised stream health and land cover (a proxy for land use) modification. The highest proportion of better scoring streams are found in areas that are predominantly in native vegetation, followed by exotic forest, then pasture. Urban streams generally receive the worst scores.

What causes river health to degrade?

Polluted run-off is the most significant contributor to water quality decline in New Zealand. Run-off is water running from our land to rivers, lakes, and beaches; along the way this water picks up pollutants such as chemicals and fine sediment from sources such as roads and streets, agriculture, horticulture, forestry, and homes. Some other factors that also impact river health include changes in climate, flow regime, shade, channelisation, pest invasions and blockages to fish passage.

How is river water quality monitored in New Zealand?

All regional councils and unitary authorities in New Zealand monitor indicators of river health at sites in their region as part of their State of the Environment monitoring programme. The monitoring is usually done monthly by council environmental officers who collect samples as per national guidelines and send them to an independent laboratory for analysis. The National Institute of Water and Atmospheric Research (NIWA) also administer a water quality monitoring network. Results are publicly available on the LAWA website.

How was the national picture generated?

Cawthron Institute led the analyses. The current state of sites from New Zealand’s most comprehensive river water quality network was calculated from a dataset comprising monitoring data regularly collected by all 16 regional and unitary councils, and National Institute of Water and Atmospheric Research (NIWA).

The evaluation requires an almost complete history of monthly measurements over the previous five years before a grade can be assigned, so not all sites that feature on the LAWA website can be graded. The ‘current state’ for 2020 at each site is based on data from 2016 to 2020.

To look at how state varies between sites in different land cover, Cawthron used land cover classes derived from the nationally consistent New Zealand River Environment Classification (REC).

What do the different coloured bars in the national summary graphs mean?

LAWA evaluates conditions at sites nationwide against the attribute bands described in the NPS-FM 2020, where expectations of each indicator’s values are defined from A (good) to D or E (poor).

What does the LAWA national interactive river water quality map tell us?

Sites displayed on the map for each indicator are colour-coded by their state attribute band. Site icon arrows represent whether trend is improving, indeterminate, or degrading for the chosen indicator. Sites with insufficient monitoring histories to generate state/trend under LAWA criteria are coded ‘not assessed’.

Why is LAWA reporting on these six indicators, what about other river health indicators? 

The six key indicators reported on at the national level for the LAWA River Water Quality National Picture Summary 2021 are widely recognised indicators of river health and are reported against national guidelines. At an individual site level, LAWA shows more information including additional river health indicators.

The national picture summary acknowledges that nitrogen can also stimulate problematic plant and algae growth at lower concentrations than those causing direct toxicity and dissolved inorganic nitrogen (DIN) monitoring results are available at the individual site level. The NPS-FM 2020 requires management of nutrients to protect the ecological health of waterbodies and we intend to report further on this as more data and reporting guidance becomes available. 

How can the data presented on LAWA inform freshwater improvement efforts?

The Government Essential Freshwater package aims to bring New Zealand’s freshwater resources, waterways, and ecosystems to a healthy state within a generation. Monitoring data is useful for understanding the current state and for tracking change over time.

This informs the work regional councils and unitary authorities are doing to set management targets and limits within regional plans to drive regulation and priority areas for more active management. Looking at state and trend at an individual site or catchment level is useful for community groups, landowners, and other parties interested in how their local waterways are tracking.

How can people find out more about river health near them?

Interested communities can look at sites on the LAWA interactive river water quality map to view the current state of several indicators and their trends over time and develop a greater understanding of what’s happening at a catchment, regional, and national level: www.lawa.org.nz/explore-data/river-quality.

More data for a wider range of indicators is available on individual site pages. Visit regional/unitary council websites for comprehensive regional reporting and Ministry for the Environment for Environment Reporting.

What more do we need to learn?

Year on year we’re learning more about New Zealand’s waterways. Data is now available for over 1500 river sites, an increase of around a third compared with 2014. Looking ahead, more information about community freshwater values and desired state is required. Conversations at the national, regional, and catchment level will direct future work programmes.

What is Land, Air, Water Aotearoa (LAWA)?

LAWA aims to connect New Zealanders with their environment through sharing scientific data online. It’s world-leading in its approach to making data collected by authorities freely available to the public. This is made possible by a collaboration of NZ’s 16 regional and unitary councils, the Ministry for the Environment, Cawthron Institute, Department of Conservation, and Statistics New Zealand. LAWA is committed to sharing the best available information, so New Zealanders can make informed decisions.