A new paper on groundwater modelling has highlighted its inherent uncertainty that is compounded by choice in modelling and influenced by independence in testing, and calls for systematic guidelines and a multi-model approach that covers the breadth of unknown groundwater conditions.
Groundwater modellers may choose between a single ‘consensus model’ approach, or a comprehensive ‘multi-model’ system that develops conceptual models in parallel - evaluating and adapting them as further data is obtained to reduce uncertainty and produce more reliable predictions.
The paper argues that while the multi-model method is superior in reducing uncertainty, it is underutilised and wide variations exist when it is used, with models often limited by testing independence together with the time and cost involved in obtaining more comprehensive data.
“Hydrogeological data is often scarce and uncertainty around how a groundwater system functions is always a challenge,” says Ms Enemark, Flinders University PhD candidate and lead author of the paper.
“While it is impossible to make a model that perfectly describes reality, conceptual uncertainty, which relates to uncertainty in understanding how a groundwater system functions, is often ignored.”
Ms Enemark’s paper notes that few guidelines exist for developing multiple conceptual models and these are rarely followed. It advocates for a systematic approach in developing, adapting and rejecting versions of models, consistent with new data obtained.
“Comprehensive parallel modelling is time consuming, but disregarding plausible alternative models can lead to surprises - and in the long run result in additional costs,” she says.
“Reducing uncertainty in groundwater modelling reduces the risk of making decisions that could have a negative impact on the groundwater system, while also avoiding overly cautious decisions that could lead to missed opportunities.”
Published in the Journal of Hydrology, the paper; ‘Hydrogeological conceptual model building and testing: A review’ has earned rave reviews from world-leading researchers in the field, with comments including “this paper is a gem” - who commend its comprehensive review of current practices and its achievable recommendations that better take into account the uncertainties in groundwater modelling.
Ms Enemark works under the supervision of Flinders University’s Strategic Professor Okke Batelaan, a co-author on the paper, who says her findings stress the importance of emphasising multi-model approaches in teaching and industry training, and could inform future changes to groundwater modelling guidelines.
“The groundwater debates that often surround mining or other major projects highlight the need for a less subjective, more systematic approach that cover all aspects of conceptualisation relevant to the study objective,” Professor Batelaan says.
The report was undertaken with supervisory and financial support from CSIRO, Dr Dirk Mallants and Dr Luk Peeters and the National Centre for Groundwater Research and Training at Flinders University.