New Zealand has 425,000 kilometres of rivers and streams, almost 4,000 lakes larger than 1 hectare in size, and about 200 groundwater aquifers.

By international standards, freshwater in New Zealand is both clean and in good supply. However, some aspects of water quality are getting worse in areas dominated by intensive land use. Demand for water is increasing, particularly in areas that are already water-stressed.

How clean are our rivers and streams?

Rivers in undeveloped catchments make up around half of the total river length in New Zealand and generally have good water quality. The remaining river length is located in farmed and urban catchments (at a ratio of about 40:1) and these areas generally have much poorer water quality.

Pollution of our waterways from organic waste has have considerably reduced since the late 1980s as a result of improvements in the effluent from sewage treatment plants, meat works, and farm ponds. However, pollution from diffuse sources, such as run-off from farm land (animal dung and urine, and fertilisers) and urban areas, has proven difficult to tackle. As Figure 3.5 on page 42 shows, the quantity of nutrients applied to agricultural land has increase significantly since the mid-1980s. Results from water quality monitoring show that a proportion of these nutrients will end up in our waterways.

Figure 3.7 on page 50 shows that urban streams are the most nutrient-enriched waterways in New Zealand, followed by rivers and streams in predominantly pastoral catchments. The average nutrient levels in both urban and pastoral waterways breach the Australia and New Zealand Environment Committee Council guidelines for ecosystem protection. Rivers and streams in unmodified catchments, such as those that are covered in native bush or alpine tussock, have the lowest levels of nutrient pollution measured in New Zealand waterways.

The Dairying and Clean Streams Accord

The Dairying and Clean Streams Accord is a voluntary agreement between Fonterra Co-operative Group (the largest dairy company in New Zealand), regional councils and the Ministers for the Environment and of Agriculture and Forestry. Signed in May 2003, its aim is to achieve clean, healthy waterways in dairying regions.

The accord sets out practical targets for farmers; for example, that “50 per cent of regular stream crossing points are to have bridges or culverts by 2007 and 90 per cent by 2012”. This target has already been met, while there has also been a steady increase in the number of waterways from which stock have been excluded (up from 67 per cent in 2003–2004 to 75 per cent in 2005–2006). However, the level of non-compliance of discharges of dairy shed effluent (33 per cent) falls significantly short of the target set.

Riparian planting in Taranaki to protect water quality

Taranaki Regional Council is one of many councils working with farmers to develop sustainable land management and riparian planting plans. Up to June 2007, 12,400 kilometres of stream bank and 60 per cent of all dairy farms in the region were covered by riparian plans. By the same date, more than 1 million plants had been provided to farmers by the Council, at cost, for land and riparian planting.

Water quality at swimming spots

More than 230 sites on rivers and lakes throughout the country are regularly monitored for recreational water quality. These are sites where water-based activities such as swimming, water-skiing, and diving are common.

Water samples are typically taken once a week over the summer (November to March) and are tested for E. coli, the indicator of faecal pollutants in freshwater. When E. coli levels are higher than those recommended by the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas, regional councils liaise with health authorities to make sure the public is warned (by signs or other means) of the health risk.

Figure 3.8 on page 52 shows that, over the 2006–2007 summer, 60 per cent of monitored swimming spots on rivers and lakes had water quality that met New Zealand guidelines for water-based (contact) recreation almost all of the time (that is, at least 95 per cent of samples taken at these sites were within acceptable levels), and were therefore safe for swimming.

Sampling over the past four seasons suggests that bacteria levels have improved over the monitoring period, but the data is sensitive to the weather (that is, whether the summer is dry or wet) and it is too early to draw firm conclusions from this sampling.

Government action to manage freshwater quality

The Sustainable Water Programme of Action

In 2003, the Ministry for the Environment and the Ministry of Agriculture and Forestry jointly launched the Sustainable Water Programme of Action (SWPoA) to identify priorities for government action to improve freshwater management in New Zealand. The SWPoA has a particular focus on addressing the pressures on water bodies from land-use change and intensification. Extensive consultation in 2005 revealed broad support for the development of policy in a number of areas of freshwater demand and quality management.

By 2007, Cabinet had approved the development of a national policy statement on freshwater, as well as two national environmental standards, including one that will ensure methods used to allocate water are geared to safeguard aquatic ecosystems. Another focus of the SWPoA is to produce tools and best-practice guidance for regional councils on water quality and land-use management.

Water-skiing on lake Taupō

Source: Ministry for the Environment.

Figure 3.7: Comparison of median nutrient levels in rivers and streams by catchment land use, 1997–2002

Nitrate Nitrogen

 

Dissolved Reactive Phosphorus

Ammoniacal Nitrogen

Notes:

(1) Catchments are defined as ‘natural’ unless pasture exceeds 25 per cent of the catchment area (in which case, it is classed as ‘pastoral’), or unless urban land use exceeds 15 per cent of the catchment area (in which case, it is classed as ‘urban’).

(2) The Australia and New Zealand Environment Committee Council guidelines provide ‘trigger values’ for the protection of ecosystems and the recreational and aesthetic values of waterways. If a trigger value is reached, it does not necessarily mean that ecosystem damage is occurring or that recreation is no longer possible, but it provides advance warning that a problem may be emerging.

(3) mg/L = milligrams per litre.

Data source: Adapted from Ministry for the Environment, in press a.

Figure showing (1) map of all rivers in New Zealand (that appear on a 1:50,000 topographic map) colour-coded according to whether they are in catchments dominated by natural, pastoral or urban land use/cover, and (2) graphs of median nutrient trends across the network. 

Key message from the graphs is that medians for dissolved reactive phosphorus, nitrate-nitrogen and ammoniacal nitrogen in pastoral and urban catchments are higher than natural catchments and generally exceed ANZECC guidelines.

Nitrate Nitrogen

Year

Measure

Pastoral (mg/L)

Natural (mg/L)

Urban (mg/L)

ANZECC Guideline (mg/L)

1997

Median

0.335

0.0775

0.93

>0.306

1998

Median

0.31

0.08

0.82

0.306

1999

Median

0.366

0.0765

1

0.306

2000

Median

0.32

0.091

0.8825

0.306

2001

Median

0.355

0.0905

0.6675

0.306

2002

Median

0.394

0.07075

0.8

0.306

Ammoniacal nitrogen

Year

Measure

Pastoral (mg/L)

Natural (mg/L)

Urban (mg/L)

ANZECC Guideline (mg/L)

1997

Median

0.02

0.008

0.05

>0.0155

1998

Median

0.02

0.006

0.05

0.0155

1999

Median

0.02

0.0085

0.05

0.0155

2000

Median

0.018

0.0085

0.05

0.0155

2001

Median

0.02

0.01

0.05

0.0155

2002

Median

0.02

0.0095

0.05

0.0155

Dissolved reactive phosphorus

Year

Measure

Pastoral (mg/L)

Natural (mg/L)

Urban (mg/L)

ANZECC Guideline (mg/L)

1997

Median

0.015

0.01

0.02

0.0095

1998

Median

0.013

0.01

0.02

0.0095

1999

Median

0.0135

0.008

0.02

0.0095

2000

Median

0.013

0.0075

0.015

0.0095

2001

Median

0.0155

0.00675

0.015

0.0095

2002

Median

0.0145

0.006

0.01025

0.0095

 

Figure 3.8: Bacterial water quality at monitored freshwater swimming spots, 2003–2007

Proportion of sites in each compliance category 2003-2007

Notes:

(1) The map shows 2006–2007 summer data only; the legend applies to the map and graph.

(2) Compliance with the guidelines for freshwater is based on the threshold of 550 E. coli per 100 millilitres of water sampled.

(3) Some councils did not sample sites in the 2006–2007 summer because they rotate their monitoring programmes (for example, Environment Waikato samples sites on alternate years) or were undertaking targeted water quality investigations (for example, Tasman District Council).

Source: Data collected by regional, city, and district councils and collated by the Ministry for the Environment in 2007.

Figure showing (1) map of locations of swimming spot monitoring sites colour coded according to the category of bacterial water quality (4 categories from “more than 95% of samples comply with guidelines” to “less than 75% of samples comply with guidelines”), and (2) a stacked bar graph showing numbers of monitoring sites in each category for each year between 2003 and 2007 (see source data).  The map shows that sites are distributed throughout the country with good and poor sites appearing in every region.  The poorest sites generally appear close to the coast (i.e. they are downstream sites in lowland areas).

% of beaches compliant

 

2003-04

2004-05

2005-06

2006-07

Between 95% and 100% of samples taken over the bathing season complied with guidelines.  Sites in this category have typically good water quality and are generally safe for recreation.

41%

52%

49%

60%

Between 90% and 95% of samples taken over the bathing season complied with guidelines. 

22%

16%

22%

13%

Between 75% and 90% of samples taken over the bathing season complied with guidelines. 

24%

20%

15%

17%

More than 25% of samples taken over the bathing season did not comply with guidelines.  Sites in this category have typically poor water quality and are often not safe for recreation.

14%

12%

14%

10%

Sum

100%

100%

100%

100%

 

Iwi monitoring of freshwater: Cultural Health Index

The Cultural Health Index for Streams and Waterways (CHI) is a tool developed by Ngāi Tahu and supported by the Ministry for the Environment, Te Rūnanga o Ngāi Tahu, and Ngāti Kahungunu. Its purpose is to facilitate the monitoring of waterways by Māori.

The CHI gives iwi/hapū the opportunity to assess and report on the cultural health of a catchment or stream in their area. It provides a basis for iwi/hapū to assign priorities for the management or restoration of specific sites and monitor changes in them over time. It also provides a common platform for resource management agencies and iwi/hapū to discuss and incorporate Māori values for stream health in management decisions.

The CHI works by assessing and providing a ‘score’ for three aspects of the monitored waterway:

  • the significance of the freshwater site to Māori
  • the cultural use values of the site
  • the health of the stream or river.

The first measure assesses whether the site is of traditional or contemporary significance to Māori. It also evaluates whether Māori would return to the site in the future given its present state.

The second measure assesses the ability of the site to sustain cultural use. To do the assessment, the CHI identifies food resources (mahinga kai) present at the site, compares them with traditional mahinga kai sourced from the site, evaluates how easy it is for Māori to access the site, and determines whether or not Māori would return to use the site in the future.

The third measure assesses stream or river health by considering eight different criteria: water quality, water clarity, flow and habitat variety, catchment land use, riparian vegetation, riverbed condition/sediment, use of riparian margin, and channel modification. The scores for each criteria are averaged to produce a final stream health score.

What’s happening in our lakes?

New Zealand mountain lakes have good visibility. As an example, underwater visibility in South Island mountain lakes is commonly more than 10 metres. Two-thirds of New Zealand lakes are in natural or partially developed catchments and are likely to have good to excellent water quality.

Figure 3.9 shows that lakes in natural catchments have water that is, on average, five times clearer than water in lakes in pasture catchments because of the higher algal concentrations in the latter. Figure 3.9 also shows that lakes surrounded by farmland are likely to have much higher levels of nutrients than lakes in natural catchments.

Of the 49 lakes for which we can establish longer-term trends in nutrient levels, most have shown no signs of change in nutrients since 1990. Ten show possible or definite signs of deterioration and six show signs of improvement. Many of the lakes showing signs of deterioration are already moderately nutrient-enriched (meso-eutrophic) and lie in largely developed catchments (for example, Waikere in Northland, and Waikare and Rotomanuka in the Waikato).

Lake Tekapō

This photo shows Lake Spectacle (lake Tomorata in the background) in the Auckland Region. Water quality of Lake Tomorata has declined because of farming around its margins.

Source: iStockphoto.

Figure 3.9: Comparison of lake water quality in pasture catchments and natural catchments, 2004–2006

 

Notes:

(1) Total nitrogen concentrations are much higher than total phosphorus concentrations, but nitrogen values have been scaled down by 100 in this graph for the purposes of presenting information on both nutrients together.

(2) mg/L = milligrams per litre.

Data source: Ministry for the Environment, in press b.

Bar graph comparing water quality variables for lakes in pasture versus natural catchments.  Key feature is that nutrient levels are higher and visual clarity lower in lakes in pasture catchments.

 

Parameter

Natural catchment (39 monitored lakes)

Pasture catchment (55 monitored lakes)

Total nitrogen* 

0.00174

0.00733

Total phosphorus

0.0083

0.051

Algae (Chlorophyll a)

0.0017

0.0094

Visual clarity (m)

6.4

1.2

Local action to protect water quality in Lake Taupō and the Rotorua Lakes

The Bay of Plenty and Waikato regional councils are working with district councils, Māori trust boards, land owners, and the wider community to protect the water quality of Lake Taupō and the Rotorua Lakes.

In the Rotorua district, action plans are under development for each of 12 lakes to reduce their nutrient (nitrogen and phosphorus) levels. One example of action planned is the construction of a channel that will limit the input of nutrient-rich water to Lake Rotoiti.

Environment Bay of Plenty has produced Rule 11, a set of regional rules designed to limit the loss of nitrogen and phosphorus from land-use activities.

In the Waikato, a proposed variation to the regional plan sets a water quality objective for Lake Taupō and changes land-use controls on nutrients entering the lake from urban and rural sources.

In addition, higher standards are proposed for domestic wastewater treatment and disposal near the lake, as well as limits on nitrogen leaching from all land in the catchment. For the first time, farmers in the Waikato region will be required to cap the amount of nitrogen that may leach from their farming activities.

The Government has committed $81.5 million to the long-term Lake Taupō protection programme and $4 million towards remedial work to improve water quality in Lake Rotoiti.

Groundwater

Nitrogen is found in groundwater in the form of nitrate and is monitored for both health and environmental reasons. From an environmental perspective, elevated levels of nitrate often indicate the potential presence of other pollutants from human activities, like faecal pathogens and pesticides (that is, nitrate can be a good indicator of general groundwater degradation).

In addition, nitrate-rich groundwaters can increase nutrient levels in the surface waters they drain into. Excessive nitrate levels in drinking water have been linked with blood disease in infants (known as ‘blue baby syndrome’), although this condition is rare in New Zealand.

Sixty-one per cent of over 1,000 monitored groundwaters in New Zealand have normal nitrate levels; but the remainder have nitrate levels that are elevated above natural background levels.1 Five per cent have nitrate levels that make the water unsafe to drink for infants, while 20 per cent of 520 monitored groundwaters have levels of bacteria that make general consumption unsafe. However, it is not known what proportion of these groundwaters are used to supply drinking water to people. High levels of nitrates and bacteria are particularly common in shallow, unconfined aquifers that are situated beneath areas of intensive land use.

Water quantity

Because New Zealand has a low average population density and high average rainfall, we have more total freshwater per person than most countries. However, not all of this water is in the right place at the right time; and many areas experience seasonal water shortages, suffer from flooding, or both.

For all uses of water combined (that is, agriculture, industry, and domestic), we currently use an estimated two to three times more water per person than the inhabitants of most other Organisation for Economic Co-operation and Development countries. Demand for water is increasing, particularly in areas already short of water. Drier parts of the country have the highest demand: Canterbury and Ōtago account for three-quarters of all water allocated through regional council resource consents. Several eastern regions have surface water catchments that are highly allocated and therefore likely to be under pressure during drier times of the year.

The rapid rise in irrigation

We do not have good information about how much water is actually used in New Zealand, but regional council resource consents tell us how much water is allocated. The volume of water allocated increased by 50 per cent between 1999 and 2006, driven mainly by an increase in land area under irrigation. Around 60 per cent of the total volume of water allocated comes from rivers and streams, 34 per cent from groundwater, and 6 per cent from lakes and reservoirs. Figure 3.10 shows that 77 per cent of all allocated water is allocated to irrigation and 11 per cent to manufacturing processes.

Figure 3.10: Use of allocated water in New Zealand, 2006

Data source: Ministry for the Environment, 2006.

Pie chart showing what allocated water is used for

  • Stock watering 3%
  • Public water supply 9%
  • Manufacturing processes 11%
  • Irrigation 77%

Managing our water resources

Past generations of New Zealanders have grown up with the idea that we would always enjoy an abundance of clean water. In recent times, however, we have begun to recognise that the resource is not infinite and that we need to manage it carefully.

The significant increase in recent years in the volume of water allocated in New Zealand underscores the urgency of balancing the competing needs of water users – recreational users, town water suppliers, hydroelectricity generators, tourist operators, and farmers – while maintaining the health of the aquatic habitat. For that, we need to better understand the environmental flow requirements of streams and rivers at different times of the year and how much water we are actually using. Increasing the efficiency of water use by all sectors may alleviate the pressures we are facing in some regions.

Effort is increasingly focused on halting the decline in New Zealand’s water quality. The control of point-source pollution of freshwater under the Resource Management Act 1991 is now well in hand, and attention has turned to reducing diffuse pollution from intensive land use and urban run-off. As a result, there is greater emphasis than in the past on managing intensively used land through stream bank planting, nutrient budgeting, and exclusion of stock from waterways through bridging and fencing.


1  Given that most monitored wells are located in areas where land has been developed, the statistics presented here are more representative of areas where contamination is likely than of the overall groundwater resource in New Zealand.