Most of the New Zealand population receives safe drinking-water (Ministry of Health, 2005a). However, we do have problems with nutrient and microbiological contamination of water, partly as a result of our large primary industry base. The greatest risks are from microbiological contamination of water by viruses, bacteria and protozoa.

2.1 The need for a NES

New Zealand rates of gastroenteritis from food- and water-borne sources are double those of comparable OECD countries (Till and McBride, 2004). For example, the incidence of campylobacteriosis in New Zealand is two to three times higher than in other developed countries and more than 10 times higher than that in the United States (Baker et al, 2002; see Table 1). The proportion of disease resulting from contaminated water compared with food and other sources is unknown, but at least some of this disease is considered to be water-borne.

Table 1: Comparison of campylobacteriosis incidence between countries



Rate /100,000

New Zealand

12 months to December 2001














England and Wales



Source: Baker et al, 2002.

* Excludes New South Wales, which does not report campylobacteriosis.

Internationally, there is increasing recognition of the importance of protecting source waters as part of the process of ensuring the delivery of safe drinking-water. Drinking-water experts recognise that relying on treatment alone is not sufficient to manage the risk posed by drinking-water contamination to public health. A number of major outbreaks of water-borne disease in developed countries resulting in serious illness and death have shown that risks to health need to be reduced at every step of the way - not just in the treatment plant and distribution network, but by reducing the amount of contamination that enters water sources in the first place.

Reducing the loading of contaminants not only decreases the loading on treatment plants, but also decreases the risk of large amounts of contaminants entering community water supplies if a treatment plant fails. In addition, there are a number of disease-causing organisms and chemicals that can only be removed with sophisticated and expensive treatment. Preventing these contaminants from entering water in the first place is preferable to investing large amounts of money in sophisticated plants that are not only expensive to run but may break down, exposing communities to health risks. This ‘multiple barrier’ approach is recommended by the World Health Organisation as a key principle in preventing or reducing drinking-water contamination (WHO, 2006).

The multiple-barrier approach

‘Safety is increased if multiple barriers are in place, including protection of water resources, proper selection and operation of a series of treatment steps and management of distribution systems (piped or otherwise) to maintain and protect treated water quality. The preferred strategy is a management approach that places the primary emphasis on preventing or reducing the entry of pathogens into water sources and reducing reliance on treatment processes for removal of pathogens’ [emphasis added].

‘Identification and implementation of control measures should be based on the multiple-barrier principle. The strength of this approach is that a failure of one barrier may be compensated by effective operation of the remaining barriers, thus minimising the likelihood of contaminants passing through the entire system and being present in sufficient amounts to cause harm to consumers’. (WHO, 2006)

To improve how drinking-water is managed at source, the Ministry for the Environment is proposing a national environmental standard for the management of human drinking-water sources. This will complement proposed Ministry of Health legislation and standards for improving drinking-water supply and delivery, and will ensure a comprehensive source-to-tap approach to the management of drinking-water. This is in keeping with the multiple-barrier approach to managing human drinking-water advocated by the World Health Organization. Specifically, the NES will ensure there is a catchment component to managing human drinking-water.

2.2 International context

Major outbreaks of water-borne disease in developed countries have led to increased awareness of the importance of drinking-water quality for health. Two of the most notable outbreaks have occurred in North America.

In the small rural town of Walkerton, Canada, contamination of the drinking-water supplies by the toxin-producing bacterium Escherichia coli O157:H7 resulted in more than 2300 people becoming ill (out of a population of 4800) and caused seven deaths. Twenty-seven people require dialysis for the rest of their lives. Costs were estimated at CAN $155 million (Livernois, 2001). The contamination that caused this event entered the water supply from effluent run-off.

In another well-known case in Milwaukee, United States, 400,000 people are estimated to have become ill with cryptosporidiosis, and over 100 people died, as a result of contaminated drinking-water (MacKenzie et al, 1994). This event resulted from contamination of the water source by cattle feed lots.

The contribution of source water problems to water supply contamination events is documented in a paper summarising the causes of 19 outbreaks in six developed countries (Hrudey et al, 2002). This paper concluded that 14 of the 19 outbreaks studied resulted from source water problems.

2.2.1 International approaches to catchment protection

The importance of catchment protection in ensuring good quality drinking-water is recognised by a number of developed countries.

In the US, Williams and Fenske (2003) estimated the benefits of wellhead protection programmes at between US$4.4 million (for a population of 13,000) and US $200 million (for a population of 2.3 million) in saved capital and operating costs. They found avoided benefit-to-cost ratios of between 2.3 and 13.4. Studies in the US have found that every $US1 invested in watershed protection can save from US $7.50 to US $200 in costs for new water treatment and filtration facilities (Emerton and Bos, 2004). Protection of the catchments that supply New York city’s drinking-water are estimated to have resulted in savings of US $3 to $4 billion by avoiding the need for further treatment (filtration), and a further US $300 million/annum for operating costs.[D Smith, personal communication, Presentation to New Zealand Treasury, 2006.]

In Australia, catchment protection for Melbourne’s water supply has avoided the need to build a treatment plant to filter Melbourne’s water. This has saved approximately A$400 million, plus annual operating costs of $50 million.[T Priestly, CRC for Water Quality and Treatment, personal communication, 2006.] In addition, Melbourne’s good water quality means that residents have confidence in the public water supply. This has both social and economic benefits, as so-called “avoidance behaviour” (eg, buying bottled water) does not occur. For example, when Cryptosporidium and Giardia were detected in Sydney’s water supply in 1998, citizens were warned not to drink the water for weeks on end. The cost of avoidance behaviour during this incident was estimated at A $308 million.[T Priestly, CRC for Water Quality and Treatment, personal communication, 2006.]

In the UK, costs from different agricultural contaminant contributions (pesticides, nitrates, phosphates and soil, and zoonoses) are estimated to contribute to the requirement for additional water treatment by £260 million every year (Pretty et al, 2000).

2.3 New Zealand context

Most of the New Zealand population receives safe drinking-water. Only three percent of the population receives water from registered supplies with unacceptable levels of the faecal indicator bacterium Escherichia coli (Ministry of Health, 2005a; see Table 2). However, it should be noted that compliance cannot be assured for another 26 percent of the population, either because they receive water from unregistered supplies or because monitoring data is insufficient to ensure compliance.

Table 2: Bacteriological compliance with drinking-water standards in New Zealand, 2004

Drinking-water supply compliance with bacteriological criteria a

Number of people b

Percentage of New Zealand population (%)

Complies with E. coli criteria



Population served by registered supplies not compliant with E. coli requirements



Unacceptable levels of E. coli



E. coli monitoring not performed or monitoring data unavailable



Water suppliers did not take appropriate corrective action after detection of E. coli



Insufficient number of samples to demonstrate compliance



Laboratory not registered by the Ministry of Health for drinking-water compliance testing



Supplied with drinking-water from unregistered supplies



Source: Ministry of Health, 2005a.

a Compliance with criteria specified in Drinking-Water Standards for New Zealand 2000.

b Some people are included in more than one category.

2.3.1 Water-borne disease in New Zealand

New Zealand is fortunate in having had few large outbreaks of water-borne disease in recent times. However, there have been a number of documented outbreaks, both in towns and at camps. Between 1986 and 2003 the Ministry of Health recorded at least 16 outbreaks of water-borne disease in towns around New Zealand, and 13 at camps, ski fields and tramping huts. Details of these incidents are provided in Appendix 2.

The largest recorded water-borne disease outbreak in New Zealand occurred in Queenstown in 1984, affecting an estimated 3500 people (Taylor and Ball, 2005). A number of people were hospitalised and almost half the population’s school pupils were absent at the height of the outbreak. The cause of the outbreak was thought to be a sewer overflow close to the town’s water supply intake. Most recently, in July 2006 contamination of a drinking-water source at Cardrona skifield resulted in at least 120 cases of gastroenteritis.[Ministry of Health, personal communication, 2006.]

A study for the Ministry of Health estimated the annual background burden of water-borne disease (Outcome Management Services Ltd, 2004). The study estimated that there are over 18,000 cases of water-borne disease in New Zealand every year. The annual cost of this is estimated to be $25 million (Harris Consulting Ltd et al, 2006). However, it is important to note that it is very difficult to accurately quantify the amount of disease caused by contaminated drinking-water, because many infectious diseases carried in water can also be transmitted by food or person-to-person contact. Water-borne disease is known to be substantially under-reported, both in New Zealand and internationally (see section 5.6 for more detail).

2.4 Legislative framework

Both local government and health agencies have responsibilities for drinking-water quality at different stages, from the catchment to the consumer’s tap. Regional councils and unitary authorities (collectively known as regional authorities) have the primary responsibility for managing water quality in the environment. From the point of abstraction from source water, drinking-water quality comes under the jurisdiction of health legislation, implemented by health agencies and local government (see Figure 1).

Figure 1: Key legislation and agencies involved in drinking-water management


Note: This figure shows only the key legislation associated with the management of drinking-water. Other associated legislation includes the Local Government Act and the Civil Defence and the Emergency Management Act. The Local Government Act 2002 requires local authorities to undertake a specific assessment of the quality and adequacy of drinking-water supplies (Part 7, section 126). However, there is no mandated requirement to manage source water quality.

Note: PHRMP means Public Health Risk Management Plan.

2.4.1 Water in catchments

Activities regulated by regional councils (eg, discharges, damming, diversion, some land uses) can have adverse effects on drinking-water sources. However, there is currently no specific requirement for councils to consider the effects of activities on the quality of water sources used for human drinking when making decisions under the RMA, other than a general duty to consider effects of activities on the environment. Consequently, there is the potential for activities or discharges to be consented that reduce water quality at the point of abstraction to below what the plant is designed to treat. This presents potential health risks to the community and may result in significant costs to the supplier in upgrading treatment facilities.

There is also the potential for unintended events (often accidental and unpredictable) to contaminate water supplies. For example, failure of a waste-water treatment process upstream of a water treatment plant could threaten the safety of a drinking-water supply.

Regulatory protection mechanisms for water supply catchments vary throughout the country. An assessment of regional plans found that only three out of 16 regional plans were considered to provide comprehensively[“Comprehensive” was defined as including specific policies and rules for drinking-water supplies, numeric water supply quality objectives, and identifying or classifying water supply catchments.] for drinking-water supplies (Ministry for the Environment, 2004). The extent to which a regional council considers water supplies also depends on the knowledge it has about the catchment and the location of community water supply. While many councils will be aware of the location of larger supplies, and refer consent applications to suppliers for comment on the effects of the activity on source water quality, there is no specific requirement for this to occur.

Health, local government, building and civil defence legislation applies only after water is taken from its source for treatment and/or delivery to the consumer. To achieve integrated management of water from source to tap, and thus achieve the objective of implementing the multiple-barrier approach, controls are needed under both the RMA and health legislation. Currently there can be some ambiguity about the responsibility of local government compared with health agencies for drinking-water quality, including source water protection. Part of the reason for these discrepancies is an uncertainty at the local government level about how potential effects on human health should be considered in environmental decision-making. Some councils may also consider that controls on activities in drinking-water catchments are not needed because treatment processes can make almost any water potable (wholesome).

2.4.2 Water after abstraction

The Health Act 1956 applies to drinking-water from the point of abstraction to the property boundary (see Figure 1). Proposals are currently before Parliament to amend health legislation to improve the management of drinking-water in the form of the Health (Drinking-water) Amendment Bill. This Bill focuses on improving the management of drinking-water after abstraction, in treatment plants and throughout the distribution network. It includes a requirement to comply with national monitoring and best practice guidelines (the Drinking-water Standards for New Zealand 2005), which is currently voluntary.

However, health agency jurisdiction does not extend into catchments to the extent needed to assess and manage risks to human drinking-water. Managing and regulating activities that can affect water quality in drinking-water catchments are the responsibility of local government, primarily regional councils, under the RMA.