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ANZECC water quality guidelines - FAQs

3. How do the new Guidelines differ from the earlier (1992) Guidelines?

The new Guidelines use the previous Guidelines approach as the basic platform upon which a number of important features, either new or in expanded form, are added:

  1. Risk-based. The new Guidelines adopt a risk-based approach, which is described in more detail in issue 4. This is in line with a general move worldwide to adopt ecological risk assessment methods and takes account of the variability and complexity of aquatic ecosystems.
  2. Tailoring guidelines for local conditions. It is important to note that the new Guidelines provide default water quality guidelines, the same as in the previous 1992 document, but that these are now called guideline trigger values. However and importantly, the new Guidelines provide protocols for refining guideline trigger values in the context of local environmental conditions rather than restricting the user to these universal, single-number values. See issue 4. below
  3. Holistic approach to water quality management water. The Guidelines have moved towards a more holistic approach to water quality management: There is greater focus on issue-based management of water quality rather than management of the individual indicators of concern. Detailed guidance is provided for biological assessment, measures for which are the common end-points for management goals. For the first time, there are also guidelines for sediment quality and an introduction to suitable environmental flows for stream and river environments. Comprehensive water quality assessment requires measurement of biological, physical and chemical indicators in both water and sediment. The current Guidelines have been expanded to consider such integrated assessment.
  4. Deriving trigger values. The methodologies for deriving the physical and chemical water quality guidelines for ecosystem management (now termed guideline trigger values) have also been updated. Natural physical and chemical water quality variables (eg salinity, pH, nutrients) and aquatic biota inherently vary within and amongst ecosystem types and so the preferred method for determining guideline trigger values is to use high quality (where available) or similar quality reference sites to determine the target levels or condition of stressors and biota. This approach provides a guideline which is relevant to the ecosystem type and locality. To derive guideline trigger values for toxic chemicals, a risk-based statistical extrapolation method has been introduced for toxicants with a sufficient toxicological database: the traditional approach of using assessment factors is used for other toxicants.