It is not possible to develop a universal set of specific guidelines that apply universally
    and effectively to the very wide range of ecosystem types. Environmental factors can reduce
    or increase the effects of physical and chemical parameters at a site.

    Local ecosystems or crops may be more or less sensitive to the water quality stressor and the
    development of local site-specific guidelines may be warranted to reduce the risk of harm or
    to reduce the cost of applying guidelines that are more stringent than they need to be.

    The Water Quality Guidelines have adopted an innovative risk-based approach that is intended
    to improve the application of guidelines to all Australian and New Zealand aquatic
    environments. Decision frameworks are used particularly for the protection of aquatic
    ecosystems that help users to tailor water quality guidelines to local environmental
    conditions and to understand what local conditions may be affecting the response of local
    ecosystems to the stress, toxicant or contaminant.

    In this approach the old 'single number' guidelines (see ANZECC 1992) are regarded as
    guideline trigger values that can be modified into regional, local or site-specific
    guidelines by taking into account factors such as the variability of the particular
    ecosystem or environment, soil type, rainfall and level of exposure to contaminants.
    Trigger values are concentrations that, if exceeded, would indicate a potential
    environmental problem, and so 'trigger' a management response, e.g. further
    investigation and subsequent refinement of the guidelines according to local
    conditions.

    Thus these Guidelines have moved away from promoting single-number guidelines
    that are applied universally, towards guidelines that can be determined individually
    according to local environmental conditions.

    It is not mandatory to use decision frameworks, and generally they become more and
    more expensive as you proceed further down the 'tree'. Often they will require
    direct toxicity assessments, laboratory toxicity studies or other biological effects
    tests that will be expensive to conduct in meeting the protocols contained in the
    published guideline documents.

    However they can also have cost benefits by avoiding the high cost of applying the
    highly conservative default guideline trigger which may be much more stringent
    than they need to be. On the other hand for high conservation sites the risks of
    applying the default guidelines may be too large as there is a chance that local
    endangered species may be very sensitive and would be harmed by values close to
    the trigger value.

    Decision frameworks apply guidelines that are more relevant to a specific water
    resource and environmental value can be developed where considered appropriate.
    However, it may take more time, expertise or resources to implement the
    risk-based decision frameworks, particularly where additional data collection
    is required to augment the data already collated.

    Which stakeholder(s) are responsible for data collection and implementation of
    the decision frameworks will depend on the issue (e.g. environmental impact
    assessment process or management strategy development) and the jurisdictions'
    legislative and regulatory tools, and should therefore be decided on a
    case-by-case basis.

    Alternatively, where resources, data and/or time are significant constraints,
    users can take a more conservative approach and initiate an appropriate
    management response when either the initial trigger value or a partly modified
    trigger value.

    Decision Frameworks have been developed for a variety of guideline value lists
    and for various processes. Some of the more important ones have been provided
    on this site with links to the guideline list web pages. Users should always
    consult the decision frameworks before applying the default guideline trigger
    values in the lists.

    The Decision Frameworks reproduced on this site are shown below: