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Definitions of some terms on Freshwater for Life


A large diverse group of plants. The algae we talk about on this site are found in freshwater or marine environments.

Algal blooms

A rapid increase of algae in a water system. These look like mats of slimy growth on river beds and soupy, green, smelly water in slow-moving parts of the river. Algal blooms are often caused by an influx of nutrients in a water system.

Algal bloom – Oroua River
Algal blooms

Algal bloom – Matakana River
Algal blooms 2

ANZECC 2000 Guidelines

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC 2000) were published jointly by the Australian and New Zealand Environment and Conservation Council (ANZECC) and the Agricultural and Resource Management Council of Australia and New Zealand. The guidelines provide a set of tools for assessing and managing ambient water quality in natural and semi-natural water resources. They are not mandatory but can be used to guide practice and formulate policy. Trigger levels are provided for differing levels of aquatic community protection. The trigger values of 99% protection relate to the narrative “no adverse effects” in the Resource Management Act 1991 (RMA) and would apply to the protection of pristine areas, with 95% value applying to a “no significant adverse effect” guideline.

Read the ANZECC guidelines

More information on the ANZECC guidelines


A benthic zone is the ecological region at the lowest level of a body of water, such as an ocean or lake, including the substrate surface and some sub-surface layers. Benthic organisms are those living on, or in, the bottom of a body of water.

Blue baby syndrome

Can be caused by methemoglobinemia (caused by the blood’s decreased ability to carry oxygen). This is thought to happen when too much nitrate is ingested and converted to nitrite; infants are more susceptible than adults. If body tissues are deprived of oxygen, infants may develop a blue coloration and possible digestive and respiratory problems.

The condition is believed to be caused by nitrate contamination in groundwater [1] – thus affecting drinking water supplies. However, this linkage has been disputed in other studies [2].

[1] Majumdar, D. (2003). The blue baby syndrome. Resonance, 8, 10-30.
[2] Addiscott, T.M. and Benjamin, N. (2004). Nitrate and human health. Soil Use and Management, 20, 98-104. DOI:10.1079/SUM2004256


Compaction is when soils are squashed (compacted) so that water, plant roots, and nutrients cannot infiltrate or flow down through the soil and occurs when soil cannot support the weight forced upon it. Compaction reduces plant cover, exposes soils, and affects soil physical properties (reducing aeration and drainage) that can lead to increased runoff, soil erosion, and ponding of water on land. These effects can cause flooding, restrict root growth and nutrient uptake by plants, as well as lower biological activity in the soil. Too many animals on the land and using heavy machinery are common causes of compaction.


Something that makes a place or substance (such as water, air, or food) no longer suitable for use.


A type of bacteria also often called ‘blue-green algae’. Under certain conditions cyanobacteria can reproduce explosively resulting in algal blooms which can become toxic, posing a danger to humans and animals.

Dead zones

These are areas in oceans and large lakes that are so low in oxygen concentration that animal life cannot survive. These zones are often caused by excessive nutrient pollution.

Diffuse pollution

Also called non-point source pollution.  Diffuse pollution does not come from a single, identifiable source but rather from many sources from different activities. Because of the nature of this pollution it is hard to regulate and control. Examples of diffuse sources of pollution are nutrient leaching and runoff, runoff from roads and towns, and waste from storm drain systems (although sometimes this is collected and discharged through pipes to nearby surface waters).

Dissolved oxygen (DO)

In water, oxygen is measured in its dissolved form as dissolved oxygen. A DO level that is too high or too low can harm aquatic life and affect water quality. DO levels fluctuate seasonally and over a 24-hour period, and vary with water temperature. DO levels are lowest just before sunrise and highest around midday. When measuring DO in water it is important to measure these fluctuations because the changes are harmful and eventually lethal for the river ecology. In a healthy system, DO levels are constant. Tolerable DO levels differ for trout, native fish and stream invertebrates but significant mortality occurs for all species at levels below 10 per cent [1]

[1] Wilcock, B.; Young, R.; Gibbs, M. and McBride, G. (2011). Continuous measurement and interpretation of dissolved oxygen data in rivers. Report prepared for Horizons Regional Council. NIWA client report.

E. coli

Escherichia coli is a bacterium that lives in the intestines of warm-blooded organisms. E. coli is used as an indicator to test the presence of human or animal faecal matter in water and whether it is safe to ingest. If E. coli is present, there is a greater risk of pathogens being present.


Effluent generally refers to wastes discharged into surface waters. It is liquid waste that flows out of a treatment plant, sewer, or industrial outfall. Farm dairy effluent (FDE) is the waste created by milking sheds and mainly contains faeces, urine, and wash-down water, but also comprises storm-water, spilled milk, soil and feed residue, detergents, and other chemicals. Due to its high nutrient content, shed effluent can be a rich source of fertiliser if applied to land. Dairy shed effluent is only a small proportion (5-20%) of the total waste produced by dairy cattle.

External inputs

Here we describe inputs as resources used in the production of a commodity. External inputs are those sourced outside from outside the area of production. For example, in a dairy farming system there are some inputs sourced naturally which the farmer does not control, such as rain, sunlight, and N-fixing by clover plants; and there are other standard external inputs required for production, such as cows, labour, seeds and perhaps machinery. Intensified dairy production uses more external inputs to increase production, such as fertilisers, brought-in feed, irrigation and medicine.


These are negative or positive outcomes arising during the production or consumption of a good or service that affects an unrelated third party (i.e. not the producer of the outcome), and who are uncompensated.  These are also called external costs or benefits and are often related to environmental consequences of production and use.  Negative externalities include water pollution; air pollution; noise pollution; and the depletion of resources, such as fish stocks and valuable minerals.  Most environmental externalities are public in nature and thus the public are left to deal with the costs of these externalities. These could be in the form of public health costs, clean-up costs of contamination, or taxes to fund government remediation projects.  Alternatively, the public may just have to deal with a degraded environment which will accelerate in the future.

Feed pad

A feed pad is a confined area that is used for supplementary feeding of cattle. Feed pads can be made of concrete, earth, gravel and sand, or permeable sheets of synthetic material. A stand-off area is similar but does not provide feed. The purposes of feed-pads/stand-off pads can be to minimise damage to pasture by taking stock off during wet periods, providing higher feed inputs, or capturing animal effluent.

GDP (Gross Domestic Product)

The monetary value of all the finished goods and services produced within a country’s borders. The OECD [1] defines it as:

an aggregate measure of production equal to the sum of the gross values added of all resident, institutional units engaged in production (plus any taxes, and minus any subsides, on products not included in the value of their outputs).

GDP estimates are commonly used to measure the economic performance of a whole country or region.

[1] OECD. (2001). Glossary of statistical terms – Gross Domestic Product (GDP).

‘Herd homes’/barns

This is a covered area where animals are fed supplementary or brought-in feed and taken off the pasture to reduce damage. Manure and urine can be collected and applied to pasture as a fertiliser source. Usually they are not used 24/7 but can be used to protect animals from harsh weather and minimise damage to pasture in wet conditions. ‘Herd Homes’ are different to factory farmed barns where animals are kept most of the time in cramped conditions and only fed brought-in feed. The use of factory farmed barns for dairy or beef cattle is not common in New Zealand.


This can be defined as an increase in outputs per unit area by increasing inputs.


Organisms without a backbone or internal skeleton large enough to be visible to the naked eye, such as insects, worms, and snails.

Macroinvertebrate Community Index

An index where macroinvertebrates are used for monitoring and reporting on stream health. A score is assigned to each species or taxon (from 1 to 10) based on its tolerance or sensitivity to organic pollution, then an average score is calculated based on all taxa present at a site. It tests presence or absence of species in a sample. The QMCI (Quantitative MCI) tests abundance (how many) of a certain species are in a sample.

National Policy Statement for Freshwater Management (NPS-FM)

The NPS-FM gives direction to regional councils to establish objectives and set limits for fresh water in their regional plans. It sets out eight objectives for targets on water quality, water quantity, integrated management and tangata whenua roles and interests. It provides a framework for councils on the objectives they must meet and types of policies to use to achieve these but it is up to councils to set rules and regulations to ensure the objectives and policies are fulfilled in their region. The NPS-FM aims to “improve the overall quality of freshwater within a region”*, and therefore does not protect every freshwater body as some water bodies can be further degraded as long as the overall water quality is maintained. The National Objectives Framework has been integrated into the NPS-FM. Read the NPS-FM here.

National Objectives Framework (NOF)

The NOF guides regional decision-making in the setting of freshwater objectives and limits. The NOF provides a set of values and uses so that councils can choose at what level they manage water to as long as they don’t go past a national bottom line. A set of attributes are associated with some of the values and uses, with ranges of numbers intended to represent different states that the attribute may be managed for. Each attribute has numbers that correspond with the state (A, B, C or D) of which regions can choose to manage an attribute to as long as they don’t go past the C state.

National River Water Quality Network (NRWQN)

This is operated by NIWA and provides scientific information on physical, chemical and biological characteristics of a selection of sites on New Zealand’s rivers.  The NRWQN consists of 77 sites on 35 rivers throughout New Zealand.

NRWQN sites in New Zealand

NRWQN sites

Nitrogen (N) 

A chemical element that is the most abundant uncombined element in Earth’s atmosphere and occurs in all organisms. To be used by plants and animals, nitrogen must be fixed from the atmosphere and converted to ammonium (NH4) or nitrites (NO2-) and nitrates (NO3-). Plants in the legume family are able to fix nitrogen. Nitrogen can now also be fixed synthetically, and this process is now overtaking the amount naturally fixed by plants, producing GHG emissions in the process.

Nitrate-nitrogen (NO3-N) is an important plant fertiliser but it is highly water soluble so it leaches through soils very easily and reaches waterways. Sources of NO3-N include inorganic fertiliser, septic tanks and leaking sewerage systems. Nitrate can also enter waterways from the nitrification of the ammonia in animal waste. Total nitrogen (TN) is the sum of all organic and inorganic forms of nitrogen tested in a water sample.

Nutrient leaching and runoff

The main ways that nutrients end up in water from diffuse pollution is through leaching and runoff. Nitrogen makes its way to water mainly through leaching which occurs when the plant cover cannot take up all the nitrogen so it moves down past the shallow root zone and through the soil. The nitrogen eventually moves into water, either groundwater storage areas or laterally into streams and then lakes and estuaries. The main form of nitrogen leaching is from cow urine because it occurs in small concentrated patches that the pasture cannot take up.

Nutrient runoff is the process of nutrients flowing over the soil where they might make their way to water. This form of transport is more common with phosphorus. Nutrient runoff is more likely to occur: with heavy rainfall as water flows over the soil; when soils are eroded – as phosphorus easily binds to soils and is lost with them; and when soils are heavily compacted – as water is less able to infiltrate the soil so it runs off.

Nutrient pathways to water from agricultural land

Nutrient pathways to water


Nutritional components in foods that allow organisms to grow. Nitrogen and phosphorus are some of the main nutrients used in farming.


Overseer is a tool for farmers to examine nutrient use and nutrient loss on farms. It is a computer model which requires users to enter information. It then estimates the flow of nutrients in a farming system and estimates nutrient loss from the farm, including run off and leaching. It produces a nutrient budget which summarises all the nutrient inputs and outputs from a farm.


Pathogens are anything that can cause a disease. They include bacterium, virusus and fungus.


A chemical element essential for life. It is almost always present in its maximal oxidised state as inorganic phosphate rock. Dissolved reactive phosphorus (DRP) is a measure of phosphorus that is in solution in water (rather than being attached to particles). Total phosphorus (TP) is a measure of all forms of phosphorus in a water sample.

Point source

This is an identifiable localised source of something, such as pollution, and usually comes from a pipe or other discharge point. Examples of point source pollution are effluent from the dairy shed being discharged to water from a single source, sewerage discharges, and other industrial discharges from a single point. A consent from regional councils is usually required to discharge these sources to water.


The introduction of contaminants into the natural environment that cause adverse change. Pollution can be if the form of chemical substances or energy, such as noise, heat or light. Pollutants can be foreign or naturally occurring contaminants. Pollutants in waterways include nutrients (nitrogen and phosphorus), pathogens, and sediment.

Resource Management Act 1991 (RMA)

Enacted in 1991, the RMA is New Zealand’s main piece of legislation that sets out how we should manage the environment.

Statistical significance

Statistical significance is the likelihood that a result or relationship is caused by something, other than by random chance. When a statistic is significant, it means that it is very likely that the statistic is reliable, but does not mean that the finding is important.  When the groups being measured have a large sample size (i.e. lots of observation points), very small differences will be detected as significant. The relationship may be strong, moderate, or weak and differences can be large or small. The strength of the relationship and amount of difference depends on the sample size of the groups.

Stocking rate

This is the number of animals on a given amount of land over a certain period of time. In New Zealand, the stocking rate is usually expressed as the number of cows per hectare (number of cows/ha).

Supplementary/brought-in feed

Supplementary feeds are used to supply nutrients that are lacking in an animals primary diet. Supplementary and brought-in feed are feed sources brought in from outside a farm, usually to increase production, when pasture growth is low, or when cows are kept on a feed pad or in a barn.

Water footprint

Water footprinting can be used to estimate the direct and indirect water use by a consumer or producer. It measures the water volumes consumed or polluted and groups water use into blue, green, and grey water footprint. The blue water footprint is the volume of freshwater used that evaporated from surface (such as rivers and lakes) and groundwater. The green water footprint is the volume of water evaporated from rainwater stored in the soil. The grey water footprint is the volume of polluted water, which is quantified as the volume of water required to dilute pollutants to an acceptable level.

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