The importance of being uncertain in groundwater modelling

Thursday, 24 January, 2019

Current practice in groundwater modelling for assessing environmental risk is often insufficient when predicting potential impacts and their likelihood. Making uncertainty analysis a routine component of assessments represents a major reform for groundwater modelling in Australia.

In an Explanatory Note released in December 2018 by the Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development (IESC), co-authors and groundwater specialists Hugh Middlemis (HGL) and Luk Peeters (CSIRO), outline the need for and value of conducting an uncertainty analysis within a risk management framework.

The Information Guidelines Explanatory Note: Uncertainty analysis—Guidance for groundwater modelling within a risk management framework, identifies tools and methods to help proponents, consultants and regulators understand the range of available approaches to uncertainty, and explains that consideration of uncertainty is warranted for every groundwater project, at least in a qualitative manner.

ICE WaRM has invited Middlemis and Peeters to provide an interactive course on this topic which they will present online in February.

“For high risk projects, quantitative uncertainty analysis is required to provide information on the probabilities and consequences of unwanted outcomes, for input to risk assessments,” says Middlemis.

“Management decisions will often be directly informed by model predictions so modelling results presented to decision-makers should include estimates of uncertainty relating to potential environmental impacts and the effect of risk treatments and mitigation measures.”

The preparation of the Explanatory Note was inspired by the Workshop and Panel Session activities held at the Australasian Groundwater Conference 2017 by the National Centre for Groundwater Research and Training (NCGRT; report is soon to be released). Those sessions discussed the poor uptake of uncertainty methods and perceptions of low value for money from the results of uncertainty analysis, despite the guiding principle in the 2012 best practice modelling guidelines: “Because a single ‘true’ model cannot be constructed, modelling results presented to decision-makers should include estimates of uncertainty”.

The sessions sought to improve traditional workflows by augmenting the existing guidance, including on how to communicate effectively on this complex technical field and how to grapple with making decisions based on a range of predictive simulations and uncertainty results expressed with probabilities rather than “the traditional single number”.

The NCGRT is promoting the improved treatment of uncertainty in groundwater investigations generally and particularly in modelling studies, with training initiatives planned. The aim is to provide additional information and training opportunities that augment the 2012 guidelines on how groundwater modelling uncertainty methods can best support decision-making. (The Australasian Groundwater Conference 2019 in Brisbane in November 2019, is expected to further extend and support the initiative.)

ICE WaRM has responded to this call for training by initiating an interactive, online course in which Middlemis and Peeters discuss the Explanatory Note, not just in the context of coal development, but in a wider range of groundwater management issues. The presenters will use case studies, such as the Angas-Bremer catchment in South Australia, to illustrate many of the concepts essential to designing a transparent uncertainty analysis.

Understanding Groundwater Model Uncertainty Analysis, is a 3 hour session in which participants will have the opportunity to engage in live discussion with Middlemis and Peeters and also with peers from other countries. This session will focus on how to design an uncertainty analysis for a groundwater model project. The emphasis is not on the mathematical and statistical detail of uncertainty analysis, but on the systematic and transparent assessment and discussion of which sources of uncertainty to include. More information about this course is available at the Australian Water School.


Further information:

Information Guidelines Explanatory Note
Uncertainty analysis—Guidance for groundwater modelling within a risk management framework has been written to supplement the IESC Information guidelines for proponents preparing coal seam gas and large coal mining development proposals and complements the Australian groundwater modelling guidelines.

Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development
The IESC is a statutory committee of leading scientists under the Environment Protection and Biodiversity Conservation Act 1999 (Cth) (EPBC Act) that independently advises government regulators on the impacts that coal seam gas and large coal mining development may have on Australia’s waters resources. Further information on IESC’s role is on available on the IESC website.