Water quality guidelines
The Australian and New Zealand Environment and Conservation Council (ANZECC) has developed water quality guidelines. These guidelines are numerical concentration limits or descriptive statements that can be applied to a range of ecosystem types and water uses, such as recreational and stock water. They are part of a national strategy to use water resources sustainably by protecting and enhancing their quality,
Water quality guidelines give recommended values for indicators and are designed to ensure that Environmental Values (EV) of waters are protected. The main nationally recognised EV or uses of waters are:
Ecosystem values
- ecosystem protection (aquatic plants, fish and other flora and fauna, habitat).
Human use values
- agricultural use (irrigation, stock watering)
- recreational use (swimming, boating, passive recreation)
- human consumption of aquatic species
- drinking water supply
- cultural values.
Each of these EVs requires its own specific set of guidelines because the acceptable guideline values to maintain one type of EV may not be acceptable to maintain another EV. An example of this is the pesticide levels required to protect fish and other fauna are usually lower than those required for protection of irrigated crops. Another reason is that the indicators used to assess one EV may be different to those used for other EVs. For example, a key indicator for recreational use is faecal bacteria numbers, but this indicator is not used for most other EVs.
Recognised guideline documents for the above EVs are:
- Ecosystem protection:
- Australian and New Zealand guidelines for fresh and marine water quality
- Queensland Water Quality Guidelines 2009
- Agricultural use: Australian and New Zealand guidelines for fresh and marine water quality
- Recreational use: Guidelines for Managing Risks in Recreational Waters:
- Human consumption: Australia New Zealand Food Standards Code:
- Drinking water supply: Australian Drinking Water Guidelines
- Cultural values: No recognised guidelines
Guidelines for human use EVs are almost all expressed as a single value of an indicator that applies uniformly across Australia (e.g. salinity guidelines for crops in Queensland are the same as those in West Australia). Human use EV guidelines are also dominated by physico-chemical indicators. As a result, these guidelines are relatively simple in concept and application.
Guidelines for ecosystem protection are considerably more complex. The main factors contributing to this are:
- ecosystem protection guidelines for some indicators (e.g. nutrients, chlorophyll-a) need to be specific to different regions (e.g. Wet Tropics versus south-east Queensland) because there are natural variations in their values
- within each region, ecosystem protection guidelines for some indicators (e.g. nutrients, chlorophyll-a) need to be tailored to different water types because they have naturally different values of these indicators. The main water types identified in the ANZECC 2000 guidelines are marine, estuary, freshwater lowland, freshwater upland, wetlands, lakes and reservoirs. As there are different flora and fauna in these water types, guidelines for toxicant indicators may also have to be tailored (e.g. coral reefs may be more sensitive to some pesticides than inshore or freshwater flora and fauna)
- ecosystem protection guidelines include physico-chemical indicators and biological, and sometimes habitat, indicators. Guideline values for biological indicators tend to be very regional and water type specific
- the ANZECC guidelines have specified three different levels of protection for ecosystems:
- high ecological value
- slightly to moderately disturbed
- highly disturbed.
For each level of protection, slightly different guideline values may apply.
The need to develop guidelines for specific regions, water types and local flora and fauna is one of the main reasons why the Queensland water quality guidelines were developed. These are aimed at developing and capturing regional and local data to a degree that is simply not possible in national guidelines.
Addressing the various issues with ecosystem protection guidelines is discussed in detail in both the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000) (ANZECC 2000) and the Queensland Water Quality Guidelines
Devloping guidelines
The ANZECC and ARMCANZ 2000 guidelines recommend two main approaches to developing guidelines:
Guidelines based on direct impact studies
This approach is best suited to the development of guidelines for physico-chemical indicators. It relies on development of a relationship between the indicator and the EV in question. Examples of this would include impacts of:
- salinity on crops
- blue-green algae on humans or stock
- toxicants or low dissolved oxygen on biota
- reduced light penetration on seagrass growth.
Based on known relationships, we can determine an acceptably safe level of the instream pressure indicator and use this as a guideline value. Developing guidelines using this approach requires a high level of technical expertise and resources. Therefore, this approach is usually confined to universities or other research organisations.
Direct impact studies are the preferred approach for developing guidelines and human use environmental values. However, this approach is often not possible for guidelines for ecosystem protection. For some indicators, the relationship between a physico-chemical indicator and the flora and fauna is not known. In the case of biological indicators, this approach is not applicable because we are not looking at a relationship between a physico-chemical indicator and the flora and fauna; we are trying to establish what the natural values of the flora and fauna are.
Therefore, for many ecosystem indicators, guidelines are instead developed using a referential approach.
Guidelines based on a referential approach
This approach is best suited to biological indicators (e.g. macroinvertebrate diversity) or to physico-chemical indicators (e.g. nutrients) where there are no simple direct-impact relationships.
Using a referential approach, guideline values for a particular indicator are determined by the condition of that indicator in a relatively undisturbed system. This becomes the reference condition. For example, dissolved oxygen guidelines would be based on typical dissolved oxygen values found in a relatively undisturbed system. Similarly, guidelines for biological indicators, such as macroinvertebrates, would be based on macroinvertebrate populations found in undisturbed systems.
The actual guideline value is calculated on the basis of maximum acceptable departure from reference condition. What constitutes an acceptable departure can be debated at length. However, the default acceptable departure suggested in the ANZECC 2000 guidelines (section 3.3.2.4) is that the guideline value be based on the 20th and/or 80th percentile (whichever is most appropriate for the indicator) of values at the reference site.
The referential approach can be used by regional groups. Provided that reference data is collected according to agreed protocols (adequate numbers of reference sites and data values, adequate time periods of collection and adequate quality assurance) then such groups can use their own monitoring data to develop local guidelines.
More detailed discussion of guideline development can be found in the ANZECC 2000 guidelines – see in particular pages 3.3–6 to 3.3–9. and the Queensland water quality guidelines.
Water quality guidelines and water quality objectives
Guidelines are often confused with water quality objectives. While guideline values are commonly used as de facto objectives, conceptually the two are quite distinct. According to the ANZECC 2000 guidelines, the definition of a water quality objective is:
“A water quality guideline was defined above as a numerical concentration limit or descriptive statement recommended for the support and maintenance of a designated environmental value. Water quality objectives take this a step further. They are the specific water quality targets agreed between stakeholders, or set by local jurisdictions, that become the indicators of management performance.”
Thus, while guidelines are the technical basis of objectives, final water quality objectives take into account social and economic factors and are ultimately agreed to by all stakeholders. They also usually have some legislative standing whereas guidelines may not. In Queensland, recognised water quality objectives are contained in schedule 1 of the Environmental Protection Policy (EPP) for Water (PDF)*. In areas where no water quality objectives are scheduled, the Queensland water quality guidelines apply as default objectives.
As with guidelines, the term “water quality objective” has traditionally referred only to the physical and chemical characteristics of waters. In modern usage, water quality objectives encompass a much broader range of characteristics including flora and fauna, habitat, flow and physical condition.
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Last updated 10 February 2011