When the first barrier fails: public health and policy implications of nitrate contamination of a municipal drinking water source in Aotearoa New Zealand

ABSTRACT

Safe, good-quality drinking water is a foundation of public health. Its provision relies on multiple barriers, the first being the protection of source water. Source water refers to the bodies of water (aquifers, rivers, lakes, springs, reservoirs) from which communities and individuals take their drinking water. A large waterborne campylobacter outbreak in 2016 spurred the New Zealand government to make a suite of legislative and policy reforms to strengthen the country’s drinking water supply system. However, the nitrate contamination of a municipal drinking water source, and its subsequent breach of drinking water standards, should bring renewed attention to the protection of source water. This article presents a case study of the exceedance and a review of legislation and policy governing drinking water sources. It finds that while important steps have been made since 2016, weaknesses in responsibility and accountability remain in Aotearoa’s drinking water supply system.

KEYWORDS:

• Drinking water
• source water
• public health
• policy
• nitrate

1. Introduction

On 6 August 2022, Waimate District Council (WDC) detected an exceedance of the drinking water standards for nitrate in one of their community water supplies. The exceedance revealed a failure to protect the community’s source water from contamination. This was despite source water protection being ‘the most significant barrier against drinking water contamination and illness’ (Government Inquiry into Havelock North Drinking Water 2017b, 92).

The regional council, Environment Canterbury (ECan), responsible for environmental regulation in this South Island region, emphasised higher than usual rainfall in the catchment as the driver of the elevated nitrate levels. However, an official report undertaken 7 years earlier, shows the exceedance was predicted through land use change modelling (Environment Canterbury 2015). Additionally, the new national drinking water regulator, Taumata Arowai, does not believe it has a role in investigating the contamination and exceedance, and has a limited interpretation of its powers.

WDC is currently considering different treatment options to remove excess nitrate and anticipates the installation of a denitrification plant. ECan has said they will not contribute to this cost because treatment of water supplies is not their responsibility (Hancock 2022). Additionally, no agency involved appears to be acting to adequately control the sources of the nitrate contamination of the community’s drinking water.

So, who is responsible for source water protection in Aotearoa New Zealand (NZ)? And what happens when a community’s source water becomes contaminated?

In this article, we use the Waimate exceedance as a case study to demonstrate widespread risks to public health with regard to the safety and quality of drinking water, with particular emphasis on nitrate contamination of source water. We identify the remaining weaknesses in NZ’s drinking water supply system, discuss public health and policy implications, and make recommendations to strengthen the responsibility and accountability of agencies involved in source water protection.

2. Nitrate contamination of drinking water and human health

Nitrate is a common drinking water contaminant, largely driven by agricultural activity (nitrogen fertiliser application and livestock urine) (Rogers et al. 2023). In NZ, nitrate leaching has increased substantially since 1990, mainly due to a 70% increase in dairy cattle (from 3.8 million animals in 1994 to 6.5 million in 2017) (Julian et al. 2017). This intensification of NZ’s dairy industry has been supported by a six-fold increase in the use of nitrogenous fertilisers (59,000 tonnes in 1990 to 429,000 tonnes in 2015) (Ministry for the Environment & Stats NZ, 2020), alongside a 19-fold increase in imports of Palm Kernel Expeller (97,000 MT in 2003 to 1,900,000 MT in 2022) (Index Mundi 2023) used as a supplementary feed. Additionally, an increase in area under irrigation has facilitated conversions to dairy farming in regions not otherwise appropriate for dairy operations, such as Canterbury. Nationally, the area under irrigation increased 91% between 2002 and 2019, with 64% of the total area under irrigation located in the Canterbury region (StatsNZ 2021).

The current Maximum Acceptable Value (MAV) for nitrate in NZ’s drinking water standards is based on the World Health Organization guideline of 11.3 mg/L as nitrate-nitrogen, (equivalent to 50 mg/L as nitrate) designed to prevent death from methaemoglobinemia in infants (Water Services Drinking Water Standards for New Zealand Regulations 2022).^1,2

A recent study found nearly 10% of 435 groundwater sites sampled nationally had nitrate levels above the MAV, and 33% of over 1000 surface and groundwater sites sampled were found to be over half the MAV (5.65 mg/L) (Rogers et al. 2023). Previous groundwater surveys have estimated nitrate-nitrogen levels in unaffected NZ groundwater (no human influence) to have a median value between 0.3 and 1 mg/L (Daughney and Wall 2007). Importantly, lag times (the time it takes for nitrate to move from land to water) can vary hugely. It may take decades for nitrate to reach deeper confined aquifers, and, for more shallow groundwater, it can be a year or several years (McDowell et al. 2021).

More recently, experimental, genetic, and epidemiological evidence has suggested nitrate in drinking water at levels well below the current MAV could increase the risk of bowel cancer (Chambers et al. 2022a; Schullehner et al. 2018) and preterm birth (Coffman et al. 2022; Sherris et al. 2021). The implications for health policies are still controversial (Office of the Prime Minister’s Chief Science Advisor 2022). However, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) review recently concluded that:

[T]here is an association between the risk of colorectal cancer and exposure to nitrites and/or nitrates, whether they are ingested via the consumption of processed meat or drinking water. The higher the exposure to these compounds, the greater the risk of colorectal cancer in the population. (ANSES 2022, 1)

3. Protection of source water

In 2016, the North Island town of Havelock North experienced an outbreak of campylobacteriosis resulting from a poorly maintained municipal bore becoming contaminated with sheep faeces, following a period of heavy rain (Gilpin et al. 2020). This one incident led to an estimated six to eight thousand people becoming ill, 42 people being hospitalised, three people developing ongoing serious health conditions (e.g. Guillain–Barré syndrome), and the deaths of four people (Gilpin et al. 2020). The following year, the government launched the Havelock North Drinking Water Inquiry (Havelock North Inquiry). The inquiry identified six fundamental principles of drinking water safety (Government Inquiry into Havelock North Drinking Water 2017b). These were based on a review of principles used in other countries. The principles stress the importance of source water protection and a preventative approach to contamination. Principles two and five are particularly pertinent to this discussion and referred to later in the text. Principle two states:

Protection of source water is of paramount importance: Protection of the source of drinking water provides the first, and most significant, barrier against drinking water contamination and illness. It is of paramount importance that risks to sources of drinking water are understood, managed, and addressed appropriately. However, as pathogenic microorganisms are found everywhere, complete protection is impossible and further barriers against contamination are vital. (Government Inquiry into Havelock North Drinking Water 2017b, 8)

Principle five states:

Suppliers must own the safety of drinking water: Drinking water suppliers must maintain a personal sense of responsibility and dedication to providing consumers with safe water. Knowledgeable, experienced, committed, and responsive personnel provide the best assurance of safe drinking water. The personnel, and drinking water supply system, must be able to respond quickly and effectively to adverse monitoring signals. This requires commitment from the highest level of the organisation and accountability by all those with responsibility for drinking water. (Government Inquiry into Havelock North Drinking Water 2017b, 8)

The Inquiry also provided recommendations, including the establishment of a dedicated drinking water regulator. Though neither the recommendations nor the principles were binding, the outbreak and inquiry formed the backdrop and basis for legislative and policy reform from 2017 onwards.

4. Policies and agencies’ roles in source water protection in 2015

In 2015, ECan made significant decisions on land use that would increase nitrate concentrations in drinking water sources. These are to be discussed, and it is appropriate to consider these decisions in the context of legislation and policy that existed at the time. While the Havelock North Inquiry did not come about until 2017, in 2015 there were existing legislation and policies that provided for the protection of source water.

The Resource Management Act (1991) (RMA) was established to promote sustainable management. Administered by councils, it stated that councils must ‘avoid, remedy or mitigate adverse effects of activities on the environment’, and ‘sustain the potential of natural and physical resources … to meet the reasonably foreseeable needs of future generations’ (Resource Management Act 1991, s 5). The RMA gave regional councils the power to make bylaws, including for the purpose of protecting drinking water sources.

Under the RMA, the government issued national policy statements and national environmental standards, which have complementary functions. National policy statements set out national direction and objectives that councils must carry out in their regional planning. These provide important context when considering resource consent applications but cannot contain rules. Councils interpret this national policy direction and apply it to Freshwater Management Units (FMU). FMUs are generally hydrological catchments but may be multiple small catchments or sub-catchments. On the other hand, national environmental standards contain rules, which apply independently of regional plans. These can require individuals (e.g. landowners) to comply with permitted activity standards or otherwise obtain a resource consent.

In 2015, the National Policy Statement for Freshwater Management (NPS-FM) 2014 was in effect. Problematically, it stated ‘overall freshwater quality in a region must be maintained or improved’ (Ministry for the Environment 2017, p. 9). This ‘overall’ approach led to many councils interpreting this to mean that quality in a catchment could be degraded provided improvements were made in another part of the catchment or region. An Environment Court proceeding found in 2015 that such an approach was unlawful (Ngāti Kahungunu Iwi Inc v Hawkes Bay Regional Council 2015 NZEnvC 50).

Under the NPS-FM 2014, councils could apply ‘water supply’ as a value for an FMU and have their regional plan reflect the requirement to protect drinking water sources. ‘Value’ in the NPS-FM is used to mean an outcome to be maintained or achieved in an FMU. Unlike ecosystem health, however, ‘water supply’ was an optional value. The intention of this was to have planning reflect drinking water requirements only in catchments where it was relevant. However, the result appears to be that protection of source water received less attention than compulsory values in planning processes.

Further requirements for councils to protect source water were described in the National Environmental Standards for Human Drinking Water Sources (NES-DW) (Resource Management National Environmental Standards for Sources of Human Drinking Water Regulations 2007). The NES-DW stated, in relation to supplies servicing more than 500 people, regional councils could not grant a water permit or discharge permit upstream of an abstraction point if this was likely to increase contaminants to the point that existing treatment would no longer be sufficient to meet drinking water standards (Ministry of Health 2018; ‘Resource Management (Resource Management National Environmental Standards for Sources of Human Drinking Water) Regulations’ 2007).

However, the Havelock North Inquiry found the NES-DW had been inconsistently applied (Government Inquiry into Havelock North Drinking Water 2017b). In fact, Hawke’s Bay Regional Council had initially given evidence to the Havelock North Inquiry that claimed they did not have any responsibility for the safety or quality of drinking water. However, as the inquiry explained:

[l]ater materials received from Regional Council did acknowledge the role and responsibility of a regional council for drinking water quality at the first barrier stage [ie source water protection]. (Government Inquiry into Havelock North Drinking Water 2017a, 91)

It went on to say:

The principal purpose of the NES Regulations was to address this “no responsibility” mindset and to create in some circumstances direct legal responsibility by regional councils for drinking water, thereby substantially boosting the strength and effectiveness of the first barrier in the multi-barrier drinking water safety system.

However, the Regional Council’s resistance to any acceptance of responsibility for drinking water (until late in the Inquiry process) has shown that this goal was not achieved in its case. (Government Inquiry into Havelock North Drinking Water 2017a, 93)

While this is the view of a regional council other than ECan, it does give insight into how regional councils may have viewed their responsibilities with regard to source water at the time.

The contemporaneous version of Ministry of Health Guidelines for Drinking Water Quality Management for New Zealand provided detailed guidance on drinking water supply (Ministry of Health 2015). They stressed a preventative approach to contamination of source water and warned that because there was no specific requirement to protect drinking water in the RMA itself, this posed a risk to public health. Although non-binding, the guidelines outlined the specific bylaws councils could use for source water protection.

In 2015, the Ministry of Health was responsible for oversight of drinking water supply. In practice, the Ministry would largely contract out this responsibility to District Health Boards (Government Inquiry into Havelock North Drinking Water 2017a). Drinking Water Assessors were employed to monitor suppliers. Water suppliers were required to produce a water safety plan, and Medical Officers of Health had some powers over these (Health Act 1956, ss 69ZA and 69ZZP). The Havelock North Inquiry found that, ‘complacency was common within the drinking water supply system in New Zealand’ (Government Inquiry into Havelock North Drinking Water 2017b, 5).

5. The 2022 Waimate nitrate exceedance

The Lower Waihao rural water scheme is a groundwater-fed supply that serves ~600 people. It is located within the Lower Waitaki (the lower part of the Waitaki River catchment that forms its own management unit). There are ~180 wells drawing on groundwater in the Lower Waitaki, this includes 15 that supply public or community supplies, with the rest being private supplies (Environment Canterbury 2015).

The earliest recorded nitrate levels in the Lower Waihao were 0.7 and 1.2 mg/L in 1996 and 1997, respectively (ESR 2019). Regrettably, water supplies found to be below 50% of the MAV for certain contaminants, including nitrate, over the course of a testing programme that ran between 1996 and 2004 did not require ongoing monitoring (ESR 2019). This means, if the source of a drinking water supply was found to be below 5.65 mg/L, 20 or more years ago, it has not been legally required to be monitored since. Some suppliers have implemented ongoing monitoring, but many have not (Chambers et al. 2022b). This approach to drinking water monitoring has led to major gaps in public health surveillance and research (Chambers et al. 2022b). Consequently, the only other available records on nitrate levels in the schemes source water held and provided to researchers by the WDC prior to the 2022 exceedance were 2015 (0.6 mg/L), 2020 (1.8 mg/L) and 2021 (6.5 mg/L) (Figure 1).

Figure 1. Lower Waihao rural scheme nitrate-nitrogen monitoring data from council sampling and real-time monitor.

The 2021 measurement was above half the MAV, which triggered new reporting requirements: a minimum of one test per month for at least 1 year (Ministry of Health 2018). It is unclear why the first 2021 sample was taken. In July 2021, a real-time nitrate sensor was installed at the treatment plant to monitor nitrate levels every 5 min (Figure 1).

In 2022, 21 days in August and 5 days in September had nitrate levels above the MAV. Thus, if WDC had implemented the minimum regulatory requirement of a single monthly test, the exceedance might have been missed. However, while the real-time monitor was useful, it could not be preventative. In August 2022, WDC issued a do-not-drink notice, providing the community with a temporary alternative drinking water supply in tanks.

On the recommendation of the Havelock North Inquiry, a new dedicated drinking water regulator, Taumata Arowai, had been established in 2020. The Taumata Arowai – the Water Services Regulator Act 2020 established the regulator’s functions. These included ‘providing national-level oversight, leadership, communication, and co-ordination in relation to drinking water safety and regulation, including the management of risks to sources of drinking water’, and to ‘identify and monitor matters that affect the safety of drinking water, and the environmental performance of drinking water, wastewater, and stormwater networks, including current and emerging contaminants’ (Taumata Arowai – the Water Services Regulator Act Taumata 2020, s 11).

As required, WDC notified Taumata Arowai of the nitrate exceedance by WDC. The only media statement the regulator made at the time stated that their role is to ‘ensure drinking water supplied to residents was safe but it was not involved in establishing causes of contamination. It was comfortable with the council’s handling of the issue’ (Hancock 2022). It went on to say:

If drinking water quality was impacted by a consent issued by a regional council a review of the conditions of a consent could be requested … There could also be other actions possible under the Resource Management Act to address adverse environmental effects. (Hancock 2022)

However, written questions to the Minister responsible for Taumata (2023) indicate that while it suggested publicly further action under the RMA could be possible, the regulator was not expecting it would be involved in any. The written questions revealed that the regulator has a limited interpretation of its role in source water protection. In response to the question, ‘is Taumata Arowai’s nitrates strategy to reduce nitrates in source water; if so, how will this be achieved?’ the Minister answered:

I have been advised by Taumata Arowai that the water services regulator does not have responsibility for the reduction of nitrates in source water.

Taumata Arowai, as the water services regulator, is responsible for recommending standards for safe drinking water (including a standard for nitrates), reviewing water suppliers’ drinking water safety plans (including source water risk management plans), and monitoring that water suppliers are supplying safe drinking water. (New Zealand Parliament 2023)

ECan emphasised in its public statements that heavy rain led to the exceedance. While they identified intensive farming as a contributing factor, their wording suggested a gradual increase in nitrate in groundwater over decades rather than the reasonably dramatic increase documented from 2015 to the time of the exceedance (Environment Canterbury 2022).

Disturbingly, however, records from 2015 show that ECan was aware of significant risks to the district’s drinking water sources from proposed land use and activities change in the catchment but did not step in to prevent the predicted nitrate contamination. In 2015, ECan prepared a report that estimated the likely impact of converting to spray irrigation in the area called the ‘Northern Fan’ (a section of the Lower Waitaki), the area which includes the Lower Waihao. The report estimated 2014 land use generated an average concentration of 2.5 mg/L, with approximately 33% of bores potentially exceeding the MAV at some point. It warned that, with conversion to spray irrigation, the average nitrate concentration was likely to increase to 3.9 mg/L, with 59% of all bores exceeding the MAV.

From a review of legislation and policy in effect in 2015, it would have been possible to use bylaws and planning, in a way that protected the community’s source water. However, by 2017, only ~5% of the land was still using border dyke (decrease from ~30% in 2014) and spray irrigation covered ~84% of land in the Northern Fan. ECan had failed to restrict land use activities and the predicted impact on drinking water came to pass. Nationally, similar consequences of widespread conversions to spray irrigation on increased groundwater nitrate levels have been documented (Dench & Morgan, 2021).

WDC lifted the do-not-drink notice in December 2022, reporting the nitrate level had reduced to 8.6 mg/L. The NZ College of Midwives currently recommends pregnant women seeking alternative supplies if their water is found to be >5 mg/L (Office of the Prime Minister’s Chief Science Advisor 2022). WDC has committed to instal a denitrification unit, the final cost of which is yet to be determined. Early estimates place capital costs at ~$750,000 (Hancock 2022). However, this is substantially cheaper than estimates presented in a scoping report produced for another Canterbury district. That report suggests a small scheme would be $6.31 million with an operational cost of $360,000/annum (MacDuff 2022). These costs and the costs placed on those people on private bores, as well as any potential health impacts, will now apparently be borne by the community.

6. Policies and agencies’ roles in source water protection in 2023

As a result of the Havelock North Inquiry, the Ministry of Health was relieved of its regulatory role in the drinking water supply system. Taumata Arowai, the new drinking water regulator, was established under the Water Services Regulator Act 2020. The Water Services Regulator Act outlines the functions of Taumata Arowai (extracts quoted above), which include explicit mention of oversight of the management of risks to source water (Taumata Arowai – the Water Services Regulator Act 2020, s 11). Additionally, the Water Services Act (2021) grants Taumata Arowai power to appoint (or their CEO act as) compliance officers. The Act stating the regulator may,

“exercise a power under this subpart only for 1 or more of the following purposes:

1. ‘to ensure that legislative requirements have been, are being, or will be complied with:

2. to ensure that a drinking water supplier has been, is, or will be complying with a drinking water safety plan:

3. to ensure that local authorities and others are complying with any undertakings made as part of a source water risk management plan:

4. to respond to serious risks to public health relating to drinking water:

5. to investigate anything that might have contaminated drinking water and poses a risk to human life or public health:

6. to investigate the commission of offences under this Act:

7. to bring proceedings in relation to any compliance orders, enforceable undertakings, or offences under this Act” (Water Services Act 2021, s 103)

This appears to grant the regulator significant powers including investigation and enforcement. However, as discussed, Taumata Arowai has developed a remarkably limited interpretation of its functions and purposes.

In 2021, Taumata Arowai revised NZ drinking water standards. However, the nitrate MAV remained at 11.3 mg/L and inadequate monitoring requirements (described above) were not substantially changed (Water Services Drinking Water Standards for New Zealand Regulations 2022). That same year, an amendment was made to the RMA (s 104 G) that states when issuing consents, councils ‘must have regard to –

1. the actual or potential effect of the proposed activity on the source of a drinking water supply that is registered under section 55 of the Water Services Act (2021); and

2. any risks that the proposed activity may pose to the source of a drinking water supply that are identified in a source water risk management plan prepared in accordance with the requirements of the Water Services Act (2021)’.

Currently, registered supplies are primarily from a former Ministry of Health register and are largely those supplying more than 500 people. However, all suppliers (meaning anyone who is responsible for the provision of water to more than one home) are required to register with Taumata Arowai by the end of 2025. In recent public statements, Taumata Arowai has said that identifying suppliers has been difficult, with the Ministry of Health register often being out of date or incorrect (Water 2023). Under the new Water Services Act, suppliers are required to submit drinking water safety plans to Taumata Arowai as well as the source water risk management plans referred to above. These source water risk management plans must identify hazards that relate to source water, assess risks that are associated with those hazards and identify how those risks will be managed, controlled, monitored, or eliminated (Water Services Act 2021). Councils are required to provide relevant information on risks to source water to suppliers to inform their plans and ‘must assess the effectiveness of regulatory and non-regulatory interventions to manage risks or hazards to source water in their region at least once every 3 years and make this information available to the public’ (Water Services Act 2021, s 45).

Additionally, in 2020, NPS-FM was updated in 2020 and national direction with regard to drinking water was made more explicit. The NPS-FM 2020 provides a more detailed Te Mana o Te Wai framework, which establishes a hierarchy of obligations for councils in their decision-making. This hierarchy of obligations requires councils to provide first for ecosystem health of waterways in a regional plan, then provide for safe drinking water, before other consumptive or commercial uses can be considered. Te Mana o te Wai has been integrated into Taumata Arowai’s role with its one of its objectives being to ‘give effect to Te Mana o te Wai, to the extent that Te Mana o te Wai applies to the functions and duties of Taumata Arowai’ (Taumata Arowai – the Water Services Regulator Act Taumata 2020, s 10). How Te Mana o te Wai is implemented is still undergoing interpretation as iwi/Māori work with councils to establish in more detail its application in different rohe (areas), and as communities and regional councils work through the value, attribute, and limit-setting (rules governing land use and activities) required in regional plans. All councils are required to give effect to the NPS-2020 through plans that must be notified by the end of 2024.

The RMA is currently being transitioned into two Acts: the Natural and Built Environment Act (NBA) and the Spatial Planning Act. However, one potential risk to source water protection is if NBA outcomes, limits and mechanisms are not well aligned with existing freshwater policy; this could threaten the expected policy gains for environmental health and drinking water through implementation of Te Mana o te Wai.

Additionally, the NES-DW is under review with a discussion document released for public consultation in early 2022 (Ministry for the Environment 2022). Its proposals fall into three main changes: how at-risk source water areas are delineated, how activities that pose risks to source water are regulated and protecting all registered supplies. Important gains could be made for source water protection through the new NES-DW, and our recommendations reflect this.

7. Remaining weaknesses in responsibility and accountability

The legislative and policy reforms offer some important steps forward. They indicate growing government and public awareness and concern for the state of the natural environment, and improved understanding of how source water and its protection relate to many parts of our physical and policy landscapes. However, the Waimate exceedance highlights remaining weaknesses in the way source water is protected, particularly with regard to the role of Taumata Arowai, accountability for councils and precautionary measures for public health.

From this review, it appears ECan had primary responsibility to prevent contamination of the Waimate community’s source water. ECan failed to use its powers to take a preventative, precautionary approach in the protection of source water (despite this being stressed in guidance from the Ministry of Health). Having identified a significant risk of MAV breaches in its own reporting, it does not appear to have used the legal instruments available to protect source water. WDC is now intending to instal a denitrification unit as its existing treatment is no longer sufficient. This appears inconsistent with existing NES-DW requirements.

WDC met its responsibilities as a supplier. However, as a supplier, it had little or no control over source water. WDC could not control consents nor was it required to engage in regional planning. Furthermore, as it was not required to routinely monitor nitrate in its source water, restrictions on activities contributing to the contamination were not implemented. The first sample reported as >50% of the MAV for nitrate was taken in 2021, and it was only the following year the MAV was exceeded.

Even where water suppliers take an active role in regional planning to protect source water, commercial interests may outweigh appeals for more stringent targets. For example, Christchurch City Council proposed a target of 1 mg/L for aquifers that provide water for Christchurch City as part of Canterbury’s Regional Plan 7. The commissioners concluded:

[W]e are not satisfied that the additional constraint on dairy farming in the Waimakariri catchment that would be necessary to attain the more stringent standard sought by the City Council would be justified by the evidence tending to show risk of cancer (Sheppard et al., 2021, p. 62)

Given the failure of councils to protect source water exposed by the Inquiry and a review of the two Acts outlining Taumata Arowai’s role, it would be reasonable to expect the drinking water regulator would take responsibility for ensuring accountability for source water protection. However, the public comments (including answers to written parliamentary questions) indicate Taumata Arowai has chosen to focus on managing the responsibility of suppliers. It is difficult, presently, to establish if this is due to a limited interpretation of the Acts, or if its limited interpretation of the Acts is provided as a way of retroactively justifying a supplier-focused approach. Either way, this is a troubling revelation in the wake of the Waimate exceedance.

While suppliers should be required to perform a high level of care and diligence, they do not have powers nor adequate resources to be able to protect source water. Nitrate contamination requires the prioritisation of public health in decision-making over many years, over complex physical and policy landscapes. It requires a precautionary approach, vigilant enforcement of policy and adequate resources to do this.

Holding regional councils to account is not something suppliers or communities can do easily. Without adequate attention, what is eventuating is that those suppliers and individuals who can are seeking out denitrification equipment where nitrate levels are reaching or exceeding the MAV. Given the costs involved, many may be forced to accept greater risk than they would have otherwise, had councils taken a precautionary and preventative approach to protecting source water.

Approximately 800,000 people (15% of the NZ population) are served by water supplies with potentially hazardous nitrate levels (Richards et al. 2022). However, no comprehensive national database for drinking water nitrate contamination exists. Alongside lacking clarity on the scale of the issue, Taumata Arowai appears unlikely to investigate or intervene in the Waimate exceedance. If the Waimate exceedance sets the precedent for our national approach to nitrate contamination, source water and public health remain under protected and vulnerable.

8. Recommendations

While improvements have been made, there are still troubling weaknesses in the regulation of NZ’s drinking water. Oversight of regional councils remains minimal despite their power in source water protection; precaution is not being enshrined as our approach to what is a public health service (the provision of drinking water), and enforcement is (by default) being left to those without sufficient power or resources. Given this, we recommend:

• Taumata Arowai:

  • Publish an official legal view on what powers and responsibilities it is granted by its Acts.

  • Be given a drinking water advocacy function for source water protection (like the Department of Conservation has for conservation), via the Water Services Act.

  • Be required to engage in all regional plan making (giving effect to Te Mana o Te Wai).

  • Be adequately funded to take proceedings against councils where regional plans or consenting means source water protection is inadequate.

  • Commit to incident reports for serious contamination events to inform future water safety plans.

  • Revise its monitoring approach so that it can identify early and intervene where more pervasive contaminants like nitrate may be increasing.

  • Revise its nitrate MAV based on the precautionary principle, acknowledging the growing body of evidence of human health risks below 11.3 mg/L.

• The National Environmental Standard for Human Drinking Water Sources be revised to:

  • Require regional councils to identify all upstream influences on source water as the drinking water protection zone, rather than a small area around the abstraction point, as has been proposed.

  • Apply to all potential drinking water supplies, including private supplies, in the catchment, not only those the supplies required to register with Taumata Arowai.

  • Provide input (e.g. irrigation, stocking rates) control rules that can be applied immediately where nitrate (or other) contamination has exceeded the MAV.

• Requiring Medical Officers of Health to engage regional planning processes to advocate for their region’s public health needs.

9. Conclusion

The Waimate exceedance is an opportunity for NZ’s new regulator to step confidently into its role and provide robust protection for source water and the public. As with ECan in 2015, there appear to be sufficient legal instruments available to protect drinking water sources from nitrate contamination if regional councils and Taumata Arowai choose to use them. Government could address remaining weaknesses in the protection of the country’s source water by ensuring public health advocates and expertise are more deeply embedded in regional planning, clarifying the role and powers of Taumata Arowai and expanding them where necessary, and adequately resourcing the regulator to mount legal challenges in the public interest to hold regional councils to account.

Acknowledgements

The authors wish to thank Sally Gepp, Barrister, for her valuable insight, feedback, and advice during drafting.

Disclosure statement

Marnie Prickett is part of a volunteer-run campaign for improved freshwater policy called Choose Clean Water.

Additional information

Funding

No direct funding was acquired for this research. Authors receive funding by donations from the philanthropic Gama Foundation, but this funder had no role in this research or the decision to publish. Additionally, authors’ funding comes in part from a Health Research Council of New Zealand grant.

Notes on contributors

Marnie Prickett

Marnie Prickett has a background in freshwater ecology and agricultural science, with an MSc on protecting the health of waterways on agricultural land. She has been an advisor to government on freshwater policy and was chair of the Environmental Reference Group for state-owned farming company, Pāmu (Landcorp).

Tim Chambers

Tim Chambers completed his PhD in Public Health. His research focuses on environmental health and infectious diseases. His current focus is on the acute and chronic effects of water contamination.

Simon Hales

Simon Hales is a medical epidemiologist who specialises in environmental health issues including air and water pollution, climate change and social inequalities. He also has experience as a scientist, journal editor and consultant with the World Health Organisation.

Notes

1. Methaemoglobinemia is commonly known as ‘blue baby syndrome’, where nitrate interferes with oxygen in the blood.

2. This paper will use nitrate-nitrogen throughout. Values may be converted to nitrate equivalent by multiplying by 4.43.