Impacts and risks

Executive summary

A bioregional assessment is a regional cumulative analysis that assesses potential impacts of current and future coal resource development on water resources and water-dependent assets. It compares two futures, a baseline future that includes all coal mines and coal seam gas (CSG) fields that are commercially producing as of December 2012, and a coal resource development pathway (CRDP) future that includes not only the baseline coal resource developments but also the additional coal resource development, all coal mines and CSG fields, including expansions of baseline operations, that are expected to begin commercial production after December 2012.

The Methodology for bioregional assessments of the impacts of coal seam gas and coal mining development on water resources (the BA methodology; Barrett et al., 2013) states that the impact and risk analysis is the central purpose of BAs. While the BA methodology provides a high-level overview of the components and conceptual workflow, it is not detailed enough to clearly guide project teams performing a BA. This submethodology uses the concepts in the BA methodology, and provides the overall scientific logic that runs through all components and companion submethodologies, culminating in the impact and risk analysis for a bioregion or subregion.

The impact and risk analysis must meet the objectives of the BA methodology, while addressing the complexity of the bioregions and assets, and respecting good practice in risk assessment. A series of design choices that meet these requirements ensures that BAs are credible and timely and thus can constructively inform public debate and decision making. The major design choices are:

  • a dedicated hazard analysis
  • a quantitative analysis of impacts and risks
  • a focus on the predictive uncertainty
  • hydrological predictions for any location in the landscape
  • decomposition of the predictions into conditionally independent components
  • a landscape classification
  • two assessment time points
  • use of expert opinion where empirical data is not available
  • qualitative mathematical modelling to estimate direct and indirect impacts and choose key variables
  • automation of the analysis.

Given the most likely coal resource development in a region, a systematic hazard analysis provides a basis for describing the nature and severity of potential risks by identifying the potential causal pathways that may lead to changes in surface water and groundwater. Coupled with the conceptual understanding of the regional geology and hydrogeology, these pathways are embedded in regional hydrological models that make predictions at specific locations. Uncertainty is propagated through hydrological models by basing predictions upon plausible distributions of model parameters rather than fixed values. The large number and diversity of ecological assets is addressed by classifying ecosystems into landscape classes that, while still subject to predictive uncertainty, are expected to respond similarly to changes in groundwater and/or surface water. For those landscape classes that may experience hydrological change, qualitative mathematical modelling is used to produce signed digraphs that summarise the key interactions between ecosystem components and their dependence on hydrology for a landscape class. The qualitative mathematical modelling captures direct and indirect effects that may occur following changes to the hydrology as a result of coal resource development. Qualitative mathematical modelling also underpins the choice of important hydrological response variable predictions, to come from the hydrological models, and the receptor impact variables that are used as ecological indicators for that landscape class. Receptor impact models for a landscape class are functions that translate potential change in meaningful hydrological response variables into predicted changes in a receptor impact variable. They are constructed on the basis of structured expert opinion and incorporate both uncertainty in the input hydrology and uncertainty in the functional relationship as characterised by the elicited responses from experts.

Predicted distributions of the maximum hydrological change at particular locations across the simulation period (2013 to 2102), for hydrological response variables at particular locations in the short term (2013 to 2042) and long term (2073 to 2102), and for receptor impact variables at particular locations at the end of the short term (2042) and at the end of the long term (2102) underpin the assessment of impact and risk. Predictions at specific locations may be summarised and aggregated for assessing impacts and risks for individual water-dependent assets. The predicted distributions are a result of the probabilistic treatment of uncertainty through a modelling chain that considers the ecosystem modelling as conditionally independent of the hydrological modelling, and enables the quantitative assessment of impact and risk.

There are a very large number of multi-dimensional and multi-scaled datasets that are used in the impact and risk analysis for each BA. These include model outputs, and ecological, economic and sociocultural data from a wide range of sources. The data are organised into impact and risk analysis databases to enable efficient management. The purpose of the databases is to produce result datasets that integrate the available modelling and other evidence across the assessment extent of the BA.

The impact and risk analysis is reported and communicated through product 3-4 (impact and risk analysis). In addition, more details are available on the BA Explorer (, including three types of profiles:

  • a characterisation of the hydrological impact, including the summary of changes in the hydrological response variables, the identification of one or more zones of potential hydrological change, and a discussion of changes that are in scope but that are not modelled quantitatively
  • a landscape class profile, which rules out landscape classes that are outside the zone of potential hydrological change. For landscape classes within the zone, the profile assesses the hydrological changes (through hydrological response variables) and the ecological changes (through receptor impact variables) that individual landscape classes may experience. Note that receptor impact models may be developed for a prioritised subset of landscape classes within the zone, with the landscape class priority governed by factors such as the spatial extent, legislative significance and the availability of external scientific expertise for the qualitative mathematical modelling or expert elicitation
  • an asset profile, which summarises potential hydrological changes for groundwater and surface water economic assets and rules out ecological assets that are outside the zone of potential hydrological change. For ecological assets within the zone of potential hydrological change, the changes individual assets may experience are summarised by different hydrological response variables (for hydrological changes) and receptor impact variables (for ecological changes in the constituent landscape classes).

A BA is an analysis at a particular point in time. It seeks to help governments, industry and the community make better-informed regulatory, water management and planning decisions. The impact and risk analysis flags where future efforts of regulators and proponents should be directed, and where further attention is not necessary for the CRDP considered.

Last updated:
7 December 2018