Weight of evidence

Weight of evidence describes the process to collect, analyse and evaluate a combination of different qualitative, semi-quantitative or quantitative lines of evidence to make an overall assessment of water/sediment quality and its associated management. It is the central platform for water/sediment quality assessments in the Water Quality Guidelines.

Applying a weight-of-evidence process incorporates judgements about the quality, quantity, relevance and congruence of the data contained in the different lines of evidence.

The Water Quality Guidelines recommends measuring indicators from multiple lines of evidence across the pressure–stressor–ecosystem receptor (PSER) causal pathway. This will give greater weight (or certainty) to your assessment conclusions — and subsequent management decisions to meet the water/sediment quality objective — than basing your evaluation on a single line of evidence.

Our approach for weight of evidence:

  • harmonises with existing pressure–state–response (PSR) management models that include indicator sets selected across the cause-and-effect pathway
  • encompasses a broad set of line of evidence indicators, including those with interpretative and diagnostic value (e.g. toxicity, bioaccumulation, biomarkers), as well as non–water quality related stressors
  • integrates into the Water Quality Management Framework at 3 key steps
  • adapts to many typical uses of the Water Quality Management Framework.
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Defining components in the process