Deriving guideline values for water quality
To derive a guideline value requires the collection of data or information on an indicator for a water body, then use of these data to determine concentrations that will protect a particular community value.
Here we describe methods for guideline value derivation related to the protection of aquatic ecosystems — relevant to both default guideline values (DGVs) and site-specific guideline values — and other community values.
Aquatic ecosystem guideline values
Guideline values for aquatic ecosystems can be derived using:
- reference-site data
- laboratory-effects data
- field-effects data
- multiple lines of evidence based on two or more of these data.
These derivation methods are relevant to indicators for all lines of evidence that may require guideline values, namely chemical and physical lines of evidence (physical and chemical stressors, toxicants) and ecosystem receptor lines of evidence (bioaccumulation, biodiversity, toxicity).
For guideline values derived from field and laboratory-effects data, the ecological or biological effects of the stressors are used to define guideline values below which ecologically meaningful changes do not occur.
Referential guideline values define a measurable level of change from a natural reference condition that, although the ecological consequences are unknown, is considered unlikely to result in adverse effects.
For toxicants in waters and sediments, the preferred approaches to deriving guideline values are usually through the use of field and/or laboratory biological-effects (toxicity) data. But this will be dictated by other factors, including the significance or risk of the stressor and the level of protection being assigned to the waterway. For example:
- a stressor assessed to be of low risk to a waterway may not require a guideline value based on field-effects data
- a stressor assessed to be of high risk to a waterway may require a guideline value based on a multiple lines-of-evidence approach using both field and laboratory-effects data
- for waterways of high conservation/ecological value — where any change in water quality from natural background concentrations might be unacceptable — a conservative reference-site approach to deriving guideline values might be preferable.
For physical and chemical (PC) stressors, our preferred approach to derive guideline values is to use local field and/or laboratory-effects data. But these are expensive to collect so guideline values are usually derived — initially at least — using reference-site data.
The reference-site approach may be preferable where toxicants or PC stressors have naturally different characteristics relative to other similar waterways. For example:
- Lake Burley Griffin in Canberra always has naturally high total nitrogen (TN) concentrations compared to similar systems that will have lower TN guideline values
- catchments with mineralised geology can have naturally elevated concentrations of certain metals and/or metalloids compared to non-mineralised catchments.
Derivations of guideline values for ecosystem receptors and associated biological assessments are implicitly local and ecosystem-specific. They are based on reference-site data and characterisation of — and change from — a reference condition.
Primary industry guideline values
Livestock drinking water
The main revision for livestock drinking water guidance in the Water Quality Guidelines is the addition of some weight-of-evidence material. Otherwise, our guidance is structurally the same as the ANZECC & ARMCANZ (2000) guidelines, with minor changes to some of the DGVs, including those for:
- major ions (nitrate, sulfate)
- metals and metalloids (arsenic, chromium III, chromium VI)
- radiological quality.
Livestock drinking water guidelines are partly based on chronic toxicity data but most of the guideline values still require validation.
Many guideline values have remained unchanged since the ANZECC (1992) guidelines, typically due to a lack of contradictory evidence rather than being definitively developed guideline values at that time. Often the guideline values are based more on field observations than on rigorous experimentation. In some cases, human drinking water guideline values have been adapted for livestock in the absence of livestock-specific information. These guideline values are likely to be subject to revision in the future as some do not reflect current leading practice for livestock water management.
As a general principle, contaminants should be minimised in livestock drinking water and irrigation waters, to protect the health of stock and crops and to minimise impacts on human consumers of animal and plant products.
The approach to develop guideline values for irrigation waters included consideration of the crop being irrigated, the soil characteristics, rainfall and other water quality parameters and the mode of irrigation in developing recommended guideline values for salt and major ion content.
For toxicants, we considered the likely period of irrigation to derive long-term and short-term guideline values.
For pesticides, we considered the impacts of herbicides on crop growth but not on aquatic ecosystems that might be downstream of the irrigation. Aquatic ecosystem guideline values should be considered for the receiving ecosystems in setting the overall water quality objective.
Water for aquaculture
Guideline values for aquaculture were based on developments from other countries and professional judgements from local aquaculture specialists.
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Drinking water guideline values
Both aesthetic and health-related guideline values for drinking-water quality are provided in the (NHMRC 2016) Australian Drinking Water Guidelines 6 (2011) — Updated 2016.
New Zealand drinking water guidelines are also available.
Aesthetic guideline values are associated with acceptability of water to consumers (e.g. appearance, taste and odour).
Health-related guideline values are concentrations that do not result in any significant risk to the health of the consumer over a lifetime of consumption.
Health-based guideline values were set at about 10% of the acceptable daily intake (ADI) for an adult weight of 70 kg and a daily water consumption of 2 L. These very conservative health values include a range of safety factors (NHMRC 2016). Their derivation draws heavily on the international (WHO 2011) Guidelines for Drinking-Water Quality, Fourth Edition; minor differences include an average body weight of 70 kg rather than 60 kg.
Recreation and aesthetic guideline values
Coastal, estuarine and fresh waters that may be a source of primary contact (dermal exposure) or secondary contact during activities, such as boating and fishing, must be free of contaminants to protect human health.
Guidance provided in the (NHMRC 2008) Guidelines for Managing Risks in Recreational Water includes microbial quality, cyanobacteria and algae, dangerous aquatic organisms and chemical contamination.
Aesthetics of water
Colour, clarity and the absence of surface oil films and odours are important considerations for aesthetics.
No specific guideline values are set for aesthetics because this does not affect public health or ecosystem health (NHMRC 2008). Although aesthetic aspects are important in maximising the benefit of recreational water use.
Guidance on how aesthetic values might be derived includes:
- for taste and odour thresholds, the smallest concentration or amount that would be just detected by a trained group of people
- concentration or amount that would produce noticeable stains on laundry or corrosion and encrustation of pipes or fittings
- concentration or amount that would be just noticeable in a glass of water and lead to a perception that the water was not of good quality.
Cultural and spiritual guideline values
Water resources have important cultural and spiritual values, particularly for the indigenous peoples of Australia and New Zealand. Many indigenous people believe that the land, sky, water and its people are inseparable; they are all connected.
To achieve the best outcomes for the preservation and enhancement of cultural and spiritual values, water quality planning must be integrated with water allocation (quantity) planning and management processes because they are intrinsically linked.
We provide specific guidance on cultural and spiritual values of waterways in Australia and New Zealand.
ANZECC 1992, Australian Water Quality Guidelines for Fresh and Marine Waters, Australian and New Zealand Environment and Conservation Council, Canberra.
ANZECC & ARMCANZ 2000, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.
NHMRC 2016, Australian Drinking Water Guidelines 6 (2011) — Updated 2016, National Health and Medical Research Council, Canberra.
NHMRC 2008, Guidelines for Managing Risks in Recreational Water, National Health and Medical Research Council, Canberra.
WHO 2011, Guidelines for Drinking-Water Quality, Fourth Edition, World Health Organization, Geneva.