Physico-Chemical Stressor Guideline not met, or likely not to be met?
First check how often the trigger value is not met, - it may be due to natural variation (see Vol1 7.4-3)
Reference Data Available -
A trigger for further investigation is deemed to have occurred when the median concentration of n independent
samples taken at a test site exceeds the 80th percentile of
the same indicator at a suitably chosen reference site. The median and 80th percentile are re-calculated as running
estimates from the last two years of results or appropriate number of weekly or daily samples where appropriate.
The minimum data set from the reference site is two years, with a minimum of monthly sampling.
No Reference Data Available -
<<<< Level below guideline value
Level exceeds guideline value >>>>
No change or no study >>>>
<<<< Local study shows level found is OK
Where a suitable reference site in not available, or the data are inadequate, a trigger occurs when the median value compiled as a running estimate from the last n results,
does not meet the published default guideline value listed on this web site.
Next conduct the risk assessment using the Decision Tree Framework for these stressors (WQG page 3.3-2)
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Define primary management aims ( see WQG fig 3.1.1)
Determine appropriate guideline trigger values for selected indicators( see WQG fig 3.1.1)
Monitor to test key performance indicators against guideline 'trigger' values for ecosystem type
*Low Risk of Damage or Impairment of Use
#Potential Risk of Damage or Impairment of Use
Conduct site-specific study:
1. Test for ameliorating effect of local conditions;
2. Compare with reference site condition to see if level is natural locally;
3. Test biological effects (e.g. direct toxicity assessment).
#High Risk of Damage or Impairment of Use
Initiate remedial actions or Accept Level of Change
*Low Risk of Damage or Impairment of Use
WQG - Australian and New Zealand Water Quality Guidelines (ANZECC & ARMCANZ 2000)
* Possible refinement of trigger value after regular monitoring.
# Further investigations are not mandatory; users may opt to proceed to remedial action.
Note: For some stressors such as dissolved oxygen and pH the guideline is set as a minimum value. The trigger then occurs when levels fall below the guideline value.