Over a third of NZ’s monitored groundwaters saw a rise in nitrate levels in the last two decades, likely because of human activities such as farming and wastewater.
That’s one of the findings from the latest three-yearly report assessing the state of our rivers, lakes, wetlands, groundwater, and glaciers.
Our Freshwater 2026 focuses on groundwater quality as a signal of long-term problems with our freshwater, as pollution that reaches groundwater can take years to decades to flush out. Groundwater supplies drinking water to nearly half the population, and feeds about 80% of everyday flow in most rivers.
The Science Media Centre asked experts in freshwater science including ecology, groundwater, and glaciology, to comment.
Dr Roger Young, Freshwater Ecosystems Group Manager, Cawthron Institute, comments:
“This is the 4th report dedicated to the freshwater environment since 2017. It’s great to have an updated picture, but the key messages are similar to that in previous reports with climate change, land and water use, pollution, invasive species and habitat modification affecting the health of our freshwater ecosystems.
“Unfortunately, the report again emphasises the challenges we face with 54% of river length across Aotearoa New Zealand affected by moderate or severe organic pollution or nutrient enrichment, while 63% of New Zealand’s lakes are in poor or very poor health.
“The growing impact of climate change came across very strongly in the report with glaciers shrinking by 42% since 2005, droughts and floods becoming more extreme, and water temperatures rising, which can all exacerbate the impacts of existing pressures on our freshwater systems. Sea level rise is pushing salt water further inland affecting lowland ecosystems and threatening to contaminate water supplies.
“I liked the focus on groundwater in the report, which is often out of sight and out of mind. I also appreciated the emphasis on how water movement connects all the parts of the landscape and how changes in any part of the system will affect the others. I was also pleased to see the focus on the importance of water for maintaining cultural well-being, the economy, human health and recreational values – water is much more than just an environmental issue.
“These reports are a plea for action to address the challenges identified, but unfortunately don’t focus on what actions are needed and who’s responsible for implementing them. Without this, I expect to see further reports in the future showing similar concerns.”
Conflict of interest statement: “Some of my colleagues were involved in collating evidence that is presented in the report and in providing advice that helped shape the report. My colleagues and I are also involved with the Land, Air, Water Aotearoa initiative, which gathers, analyses and reports on some of the data presented in the report.”
Nicholas Ling, Associate Professor in Biodiversity and Ecology, University of Waikato, comments:
“Today’s release of the latest report on the state of our freshwater makes for sobering reading. While there are some hopeful signs of small improvements in some measured outcomes, such as a general decline in phosphorus in rivers, most parameters show either little to no improvement or a continuing worsening of conditions.
“Of particular concern is continued significant deterioration in the state of our lakes, wetlands and groundwaters. Any slight improvements in the nutrient status of rivers does not yet translate to improvements in ecological conditions, with more than half of all river length indicating conditions of moderate to severe organic pollution. Nearly two thirds of all New Zealand lakes are in poor health with little signs of improvement, and groundwaters, upon which a large proportion of the population rely on for drinking water, show increasing pollution by nitrogen, pathogens and emerging organic contaminants such as pesticides and pharmaceuticals.
“Nearly half of all rivers and most lakes are unsafe for swimming at times due to either faecal pathogens or toxic algae. Although wetlands today constitute less than 10% of their pre-human extent they continue to decline, with nearly 7,000 hectares lost in the past 30 years. While the physical habitat condition of much of our rivers is assessed as good, that does not translate to a healthy ecological condition. Nearly half of our river network is now inaccessible to migratory fish, and 89% of our indigenous fish species and 43% of indigenous plants are now either threatened with extinction or at risk. Our treatment of waste water remains a major threat to the state of our freshwaters with most treatment plants either incapable of or inadequately removing pollutants such as pesticides and pharmaceuticals. Exotic invasive species, primarily fish and plants, continue to spread and contribute to loss of indigenous biodiversity and declines in water quality.
“While the report also makes clear the potential threat posed by climate change on the future condition of our freshwater ecosystems, we must acknowledge that the current dire state is due to our parlous historical and ongoing land use management, upon which the changing climate will only add to our freshwater woes.”
Conflict of interest statement: “I have no conflicts of interest.”
Professor of Freshwater Ecology Angus McIntosh, University of Canterbury, comments:
“Our Freshwater 2026 Tō Tātou Wai Māori paints a bleak and sad picture of freshwater health, but how we address this crisis is most important. The report’s concentration on groundwater helps focus that discussion. The links between activities in catchments and the availability of safe drinking water are nicely illustrated and point to the need to deal with problems at both catchment and local scales.
“The dire state of freshwater health won’t be a surprise to those with connections to a lowland river or lake, and the report illustrates those close health, cultural, economic and recreational ties. Some water quality parameters are going in the right direction, and substantial efforts are being made in some places, but much more widespread progress in dealing with water quality and quantity problems is needed before measures of freshwater life will improve. That involves addressing large-scale causes like dams, mining, urbanisation and agricultural intensification, as well remediation to remove legacies like heavy metals, forever chemicals, nutrients, invaders and fine sediment.
“The Kai Mouriora Te Kaiwharawhara project in the companion ‘stories’ report is a nice illustration of the power of communities working together across a whole catchment to make that kind of restoration happen.”
Conflict of interest statement: “I have institutional connections or research collaborations with some of the senior science and mātauranga advisors and the external peer reviewers involved in producing the report.”
Dr Roland Stenger, Principal Scientist, Environmental Research, Lincoln Agritech Ltd., comments:
“Our Freshwater 2026 – Tō Tātou Wai Māori provides a high-level and predominantly easily understandable overview of freshwater as an interconnected system. While groundwater is highlighted in the introduction as a central focus of the report, the immense diversity of our groundwater systems in terms of hydrologic, chemical, and biological characteristics is barely explored. Accordingly, groundwater’s varying role in different environmental settings as dynamic water store and reactor for chemicals transported by the water remains rather opaque.
“While the long groundwater lag times repeatedly mentioned in the report apply to parts of Aotearoa New Zealand (e.g. the North Island’s Central Plateau), it should be noted that several studies in recent years have independently demonstrated the prevalence of young water in most of our rivers. Modelling approaches and tritium-based water dating indicate that shallow, local groundwater with an age of less than five years often accounts for most of the streamflow (and nitrogen input).
“The interconnectedness of the groundwater and surface water systems also makes it imperative to monitor, analyse, and model them concurrently, rather than as separate systems. Section 5 touches upon several areas considered crucial for improved long-term freshwater stewardship, but seems to ignore more innovative monitoring and modelling approaches (like AI-supported tools and real-time, high-frequency water quality monitoring).”
Conflict of interest statement: “No conflict of interest.”
Dr Helen Rutter, Senior Hydrogeologist, Lincoln Agritech Ltd., comments:
“The report has a focus on groundwater which is great – this is the often “out of sight, out of mind” aspect of the water cycle.
“In terms of groundwater quality, the report talks a lot about lag times, though I am concerned that readers may become a bit confused about sometimes apparently contradictory statements about long and short lag times. In reality, the whole subject of contaminant lag times is complex and poorly understood. Lag times can vary with hydrogeological setting (soil type, geology, depth to groundwater, proximity to rivers etc) but will also vary with time. We see many examples of rapid responses to major rainfall events suggesting preferential flow paths through the soils and sediments, but then very long “tails” in terms of contaminants, suggesting much slower pathways as well.
“It is good that the report identifies that we lack visibility of contaminant peaks following storms and land use change, though the only way to gain this visibility is through more targeted and high-resolution monitoring, which isn’t identified as a key knowledge gap. In my opinion, high resolution monitoring is required to understand processes driving contaminant transport, and only then can we really understand the information we obtain from spot samples.
“It is good to see shallow groundwater being recognised as a hazard, rather than as a resource, and the report specifically mentions Christchurch. However, this is not an issue just for Christchurch, but for most coastal, low-lying cities in NZ. The issue is often not so much about groundwater quality in terms of drinking water, but the increased hazard from groundwater flooding, increased liquefaction potential, and highly increased risk to urban infrastructure, particularly if the rising groundwater is also saline. This hazard will become increasingly apparent with sea level rise and extreme events as groundwater rise caused by sea level rise is expected to propagate a long way from the coast.
“In terms of strengthening models, tools and data, there are some very relevant points regarding the lack of surface water and groundwater interactions in (some) models, the fact that Māori knowledge/conceptualisation is undervalued/under-supported, and that environmental data is held across multiple organisations which then limits our ability to model and understand systems better. We need to get better at monitoring and modelling and improve on our ways of incorporating Mātauranga Māori to really be able to carry out catchment-scale management and work to improve groundwater quality.”
Conflict of interest statement: “No conflict of interest.”
Dr Murray Close, Principal Groundwater Scientist, New Zealand Institute for Public Health and Forensic Science, comments:
“It is great that this report recognises the key role that groundwater plays in our overall freshwater environment and notes some important areas where contamination of our groundwater resources is occurring.
“The impacts of climate change on our freshwater resources are highlighted but it should also be noted that, in addition to our groundwater resources being impacted by climate change, they can also act as a buffer for climate impacts as most freshwater is stored within the groundwater system. It is critical that a comprehensive understanding of groundwater is included in options to mitigate and manage climate change impacts on our freshwater resources.
“I agree with the critical knowledge gaps that have been identified in the report, and filling these gaps is increasingly important as pressures increase from climate change impacts and multiple demands on our freshwater resources. It is important that funding is allocated to fill these gaps.”
Conflict of interest statement: “I have no conflict of interest in this matter. The report’s peer review included input from another PHF Science scientist (Theo Sarris).“
Dr Catherine Moore, Principal Scientist – Groundwater and Groundwater Modelling, Earth Sciences New Zealand, comments:
“Water below ground (‘groundwater’) is an often neglected but highly significant component of freshwater systems. Groundwater sustains river flows and sustains the health of communities and economies that rely on freshwater. This report provides a much-needed focus on groundwater as a unifying theme for freshwater reporting.
“The information presented in the report discuss recent changes observed in New Zealand’s freshwater. In places freshwater quality is improving and in as many other places freshwater quality is deteriorating. Freshwater habitat is changing as lowland streams face more extreme low flows. The report emphasises the need to build resilience into freshwater management given the projected shifts in rainfall patterns, sea level rise, and increased water demand.
“Unfortunately, groundwater flows and stores are difficult to measure and monitor. Groundwater and rivers, lakes and wetlands connect through complex flow interactions, making freshwater management difficult. However, the report points to better understanding of groundwater as a key component of building such resilience to avoid “water bankruptcy”.”
Conflict of interest statement: “No conflict of interest.”
Dr Lauren Vargo, Glaciologist, Antarctic Research Centre, Victoria University of Wellington, comments:
“This report focuses on freshwater systems in New Zealand, including how they are changing. My expertise lies in freshwater availability and storage in snow and glaciers. New Zealand has almost 3000 glaciers and seasonal snow, which gain mass (fresh snow) throughout the autumn and winter, and then lose mass via the melting of snow and ice throughout the summer. This melt can be an important source of freshwater in the summer, particularly during drought years.
“However, glaciers in New Zealand are shrinking quickly (faster than most other regions on Earth), resulting in a loss of capacity for storing water and as a source of freshwater in summer.”
Conflict of interest statement: “None.”
Professor Troy Baisden, Co-President of the New Zealand Association of Scientists, Affiliate at Motu, Adjunct Prof Victoria University of Wellington, comments:
“Freshwater 2026 presents no surprises while underscoring concern about the state of our freshwater as well our ability to look after it. Across the board, some freshwater indicators continue suggest improvements when viewed over decades, so it is important to emphasise freshwater challenges can be fixed.
“In particular, growing evidence suggests successful management of phosphorous, the key nutrient that was once considered the worst contaminant to waterways worldwide. Unfortunately, nitrogen and its main form in freshwater – nitrate – has become our chief long-term problem and continues to worsen overall. So too do the indicators that reflect the ecological health of lakes and rivers.
“The report doesn’t discuss that this has led some, including Canterbury’s regional council, to declare nitrate an emergency. Such declarations follow on those for climate change emergencies, representing environmental concerns that continue to worsen despite evidence and public concern. The appropriateness of considering emergency declarations is an interesting framing of the results in this report. For my part, I think they are somewhat helpful in elevating discussion but don’t tend to solve the problem, in part because the psychology of dealing with emergencies doesn’t work well on slow-burning challenges.
“One of the challenges of environmental reporting is that MfE can only use existing studies and doesn’t fund studies or monitoring to support these reports. As a result, much of the data is predicted and key areas such as lakes and wetlands (repo) are in states that often class between poor and dire, yet there is little meaningful monitoring that can assess whether trends continue to worsen or may be improving.
“Similarly, indications of lag times that suggest timescales for improvement are improving but remain a matter of debate. For instance, groundwater work suggested after lags of 40 years, but was unable to discriminate between 40 years response and mixtures of fast and centennial responses. Recent work has suggested that rivers respond to land use and management changes on timescales 4-5 years. In general, the continuing poor pathogen contaminant indicators associated with drinking water and recreational health can, in principle, be fixed even more quickly.
“Unfortunately, recently announced recommendations to further reduce funding for environmental science, combined with recent cliff edge of funding at the end of the Our Land and Water National Science Challenge could mean that evidence to keep improving on this report will be lacking.
“That will make it harder to assemble evidence that helps MfE’s Freshwater reports lead to effective and efficient change, despite the reporting series becoming more useful in pointing out the next steps that could aid policy and management decisions. Among these are the need for better models that connect land use activity to freshwater outcomes, like the troubled Overseer software that has mainly left a gap where we should note insufficient work is underway to fill the national need.
“It also challenges the report to deliver good evidence on areas where the cases are clearly stated for concern, such as growing impacts of climate change and irrigation. The report also highlights key land use changes including a 71% increase in dairy cattle since 1990 (also noting a reported tripling of land area occupied by dairying may be classification issue).
“A final issue with gaps is the somewhat artificial separation of Freshwater from other reports on the Land and Marine environments, which can lead to gaps where interactions should be highlighted. Included among these are estuaries, which accumulate impacts of contaminants received from rivers. We lack sufficient monitoring of pervasive emerging contaminants, such as microplastics, that occur across environmental domains. Last, there remains a lack of consideration or mapping of the artificial drainage of soils, which provides a key pathway for nutrient contaminants to quickly exits soils into freshwater. The mentions of these issues in the report are too brief from my perspective, only justified by the lack of data.”
Conflict of interest statement: “Has previously had research contracts and advisory roles with MfE.”