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As published by the Certified Enterprise Risk Manager® (CERM) Academy, Issue #258

ISO 31000 defines ‘risk’ as the effect of uncertainty on objectives. The Framework for Management of Drinking Water Quality (Australian Drinking Water Guidelines) includes a requirement to identify hazards, understand risk and the uncertainty associated with it. Understanding uncertainty is important in making sure the management of your water supply systems is optimised.

In this article, I discuss a simple framework for assessing uncertainty, which avoids overcomplication and still provides an ability to understand and prioritise uncertainty.

What does the Framework say?

Element 2 of the Framework deals with assessment of the drinking water supply system, Component 3 in particular covers hazard identification and risk assessment.

Uncertainty assessment is captured here:

“Evaluate the major sources of uncertainty associated with each hazard and hazardous event and consider actions to reduce uncertainty.”

But how do we practically assess uncertainty in a water quality context?

Making an Uncertainty Assessment

I have seen examples where uncertainty has been captured in notes within a risk register or more formally, via an assessment tool. Assessment tools are extremely useful as they can provide a ‘level’ of uncertainty – but it is important to not over-complicate the assessment, particularly as in the same workshop you will be assessing risk, which can sometimes lead to participant fatigue and a less than satisfactory outcome. The important thing is to ensure that you have something which provides an acceptable level of granularity and reasonableness in the outcome.

In determining what the tool should look like, it is helpful to consider how assured you are of the outcome:

  • Confident:
  • We have a good body of information available.
  • We know what the implications of the event and/or the hazard are for the water supply system.
  • An example of a ‘confident’ outcome might be ‘business as usual’ risks which are managed routinely and supported by sound verification monitoring outcomes and good procedures.
  • Estimate:
  • We have some information available.
  • We understand some of the implications of the event and/or hazard for the water supply system.
  • An example of an ‘estimate’ outcome might be the impacts of climate change which are starting to become more certain as we are starting to experience the impacts predicted by the models.
  • Uncertain:
  • We have little information available.
  • We have little or no understanding of the implications of the event and/or the hazard for the water supply systems.
  • An example of an ‘uncertain’ outcome might be something like an emerging hazard (such as microplastics and engineered nanomaterials), which might require an industry-wide response in terms of better understanding the impacts and mitigation requirements.

To add more depth to the assessment tool, it is also helpful to understand where the source of uncertainty might arise for instance:

  • Data:
  • What you know about the system, the flow diagram, historical functioning, sound human resources who ‘know’ the system well, any system changes etc.
  • Monitoring:
  • Whether you have sound verification and operational monitoring programs in place that are periodically checked for their fitness for purpose.
  • Event or Hazard:
  • Whether you have experience of the event or hazard at your organisation, within your system, within your industry and whether you have processes in place to keep on top of events that have occurred elsewhere e.g. through periodic undertaking of ‘risk shares’ in much the same way as it is now common practice to undertake ‘safety shares’ at Toolbox and other meetings.

An example uncertainty assessment matrix is presented in Table 1.

Table 1. Example uncertainty assessment tool.

Certainty LevelPossible Sources of Uncertainty
ConfidentSound body of information availableMonitoring is robustEvent or hazard have happened before at our organisation or within the system
EstimateSome data availableMonitoring could be improvedEvent or hazard have happened before to another organisation or industry but not yet to us
UncertainNo or limited data availableAd hoc, or no monitoring in place or hazard not yet possible to monitor, even with surrogatesEvent or hazard has just ‘appeared on the radar’

I have seen many examples of more complicated uncertainty assessment tools but the important thing is to keep a focus on the objective of the tool – is it helping you to tease out the key areas of uncertainty? Do you really need five levels of granularity or will three be enough? Is the addition of more information to the assessment tool simply clouding the issue? Are you perhaps better off spending your valuable resources on things for which complexity is more warranted– such as Quantitative Microbial Risk Assessment?

In the end, you need something that is going to clearly show your areas of uncertainty and help you identify specific areas that really need actions to be identified and implemented, to improve the certainty. My advice is to keep it simple, and focussed.

Risk Edge is a trusted Australian company with long experience in risk assessment and management and auditing of water quality management systems. Contact us if you would like help with your water quality management.


By Annette Davison, Director and Principal, Risk Edge Pty Ltd; Director and Chief Risk and Product Officer, D2K Information Pty Ltd

Director and Chief Risk and Product Officer, D2K Information Pty Ltd

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