The objective of the Bioregional Assessment Programme is to understand and predict regional-scale on water resources and from coal resource developments in some of Australia’s major coal-bearing basins. The assessments distinguish areas where water resources and water-dependent assets are to be impacted (with a less than 5% chance) from those where water resources and water-dependent assets are potentially impacted. Given the regional-scale focus, the modelling does not account for local-scale details (e.g. the presence of local aquitards; stream condition). Areas identified in a (BA) as at of potentially significant serve as ‘red flags’ for directing further local investigation. Governments, industry and the community can then focus on areas that are potentially impacted when making regulatory, water management and planning decisions. In some cases, the risk of adverse impacts may be substantially diminished or negligible when local-scale factors are considered.
The impact and risk analysis considers only biophysical , such as changes in hydrology or ecology; fully evaluating consequences requires value judgments and non-scientific information that is beyond the scope of . A full risk assessment (with risk evaluation and risk treatment) is not conducted as part of BAs.
The purpose of the following sections is to highlight design choices that have steered the direction of this BA and culminated in the impact and risk analysis. Further details about the design choices are provided in companion submethodology M10 (as listed in Table 1) for analysing impacts and risks ().
220.127.116.11 Choice of modelled futures
A is a regional analysis that compares two futures of coal resource development. In the Bioregional Assessment Programme, use of the term ‘coal resource development’ specifically includes coal mining (both open-cut and underground) as well as CSG extraction. However, other forms of coal-related development , such as underground coal gasification and microbial enhancement of gas resources, are not within the scope of the assessment.
The two futures considered in a BA are:
- baseline coal resource development (baseline): a future that includes all coal mines and CSG fields that are commercially producing as of December 2012
- coal resource development pathway (CRDP): a future that includes all coal mines and CSG fields that are in the as well as those that are expected to begin commercial production after December 2012.
The difference in results between and baseline is the change that is primarily reported in a BA. This change is due to 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. Figure 3 shows the location of the coal resource developments and companion product 2.3 () provides details of the timelines for these developments.
Thus, the primary focus of a BA is on the potential on water resources and that are attributable to . In the , these include nine coal mine developments (including Caroona, which as of 2017 is not going ahead) and one CSG development. In this Assessment, the baseline includes six existing coal mines (see companion product 2.3 ()).
Although the difference in potential impacts between these two futures is the focus of the assessment, the potential impacts under the baseline are important for regional . For instance, the potential implications to groundwater-dependent s of an additional 2 m of may depend on whether the is 0.05, 0.5 or even 50 m. Potentially important impacts due to coal resource development under the baseline may also occur in parts of the where additional coal resource developments have no further effect. The assessment gives less attention to these. The year in which maximum drawdown occurs under each future is unlikely to coincide and simply adding the drawdown results in a worst-case scenario that is unlikely to eventuate. Maximum drawdown occurs when the drawdown difference is at its maximum between the baseline and a ‘no-development’ scenario, and between the CRDP and the baseline scenario. These maximum drawdowns could (and in fact are likely to) occur at different times.
The CRDP is the most likely future, based on the analysis and expert judgment of the Assessment team in consultation with coal and gas industry representatives, state agencies and the Commonwealth Government. Based on information available at the time, the CRDP for the Namoi subregion was finalised in 2015 (see companion product 2.3 () for the Namoi subregion) to allow the hydrological numerical modelling to commence. Developments in the CRDP may ultimately be implemented in different ways (e.g. changes to timing) or circumstances of coal resource developments may even change (e.g. a proponent may withdraw for some reason). For example, the Caroona development is now not going ahead, even though it is included in the CRDP. This reflects the dynamic nature of resource investment decision making, which may ultimately respond to diverse economic, political or social factors. Consequently, the CRDP is a representation of an indicative future. It highlights potential changes for water resources and water-dependent assets where assessment of local conditions will improve future understanding. Equally as important, the CRDP plays a role in identifying where changes will not occur and thus flagging where potential impacts to water resources and water-dependent assets are .
The modelling held factors such as climate change or land use (e.g. agriculture) constant between the two futures. Although the future climate and/or land use may differ from those assumed in BAs, the effect of this choice is likely to be small because the focus of BAs is on reporting the impacts of additional coal resource development, i.e. the difference in results between the CRDP and baseline. Where potential hydrological or ecological changes due to the additional coal resource development are identified it will be important to consider those changes in conjunction with local information and in the context of other water related changes that may occur in the Namoi subregion (e.g. irrigation or water extraction for human consumption) as that could also influence the ecological trajectory. This could be part of a more complete regional assessment of beyond BA.
18.104.22.168 Focus on water quantity and availability
focus solely on water-mediated , and specifically those related to water quantity, level or water resource availability. The scope of the BAs determined that potential water quality impacts are limited to salinity. Some broader water quality are identified through the dedicated hazard analysis but the scientific analysis is restricted to salinity and is only addressed qualitatively. BAs are also concerned with those and groundwater that may accumulate, either over extended time frames or as a result of multiple coal resource developments. These typically correspond to changes in surface water and groundwater that occur over long periods of time, sometimes decadal, and which may create the potential for flow-on effects through the wider hydrological system.
Many related to coal resource development may cause local or on-site changes to surface water or groundwater. These are not considered in BAs because regulatory site-based management and mitigation procedures address these issues, and because they are unlikely to create potential . The assessment identifies impacts and risks associated with water quality attributes other than salinity that potentially happen as a result of coal resource development, but does not analyse these further.
22.214.171.124 Assessment of regional-scale cumulative developments
analyse the of coal resource developments at a regional scale, and do not focus specifically on individual mines or CSG operations. The and for the each comprise a suite of developments, which are distributed across the at variable distances from each other and have variable, but often overlapping, periods of operation. Thus there is potential for the to accumulate to varying degrees in both space and time.
Regional-scale models predict the cumulative hydrological changes and potential impacts of those developments on and from multiple developments over time. The area of potential impact is more extensive and extends greater distances downstream of developments than what occurs from site-scale, single mine models. In some cases the spatial or temporal alignment of certain coal resource developments can allow for attribution of potential to individual developments, but that occurs because of that alignment rather than by design.
Results of the impact and analysis reported in this product do not replace the need for the detailed site- or project-specific investigations that existing state and Commonwealth legislation require. The hydrological and ecological systems modelling in a BA is appropriate for assessing the potential impacts on and risks to water resources and water-dependent assets at the regional scale, whereas the modelling undertaken for a mining proponent’s development, as part of an environmental assessment, occurs at a much finer scale and makes use of local information to more accurately represent the local situation. Therefore, results from these detailed mine-specific studies may differ from BA results. Employing a BA to invalidate existing site-specific modelling or impact assessments would be a fallacy; instead, BA results are useful in identifying broad areas where risk to and from future coal resource developments are likely.
126.96.36.199 Focus on predictive uncertainty
consider parameter as fully as possible when predicting hydrological outcomes (i.e. changes to surface water or groundwater) and ecological outcomes (i.e. changes to ecologically relevant receptor impact variables). For example, models were run many thousands of times using a wide range of plausible input parameters for the critical hydraulic properties, such as the hydraulic conductivity and storage coefficients of all modelled hydrogeological layers. This differs from the traditional deterministic approach used more routinely for groundwater and modelling.
While models are constrained to data, the density of reliable observation data is sparse, so results may not represent local conditions well. However, they do consistently represent the and uncertainty at all sites through of possible hydrological changes, where the area, depth, timing and assumed pumping rates of each development largely determine the spatial variation, and lack of detail about the physical environment at any given point in the define the uncertainty.
Given the wide range of plausible input parameters used in the regional modelling, the hydrological changes due to at any given location within the assessment extent are likely to lie within the distribution of modelled changes. This assumption is likely to be tested near open-cut mines where potentially steep hydraulic gradients at the mine pit interface are poorly resolved in the regional groundwater models. These areas are excluded from the regional analysis for this reason. Where the BA regional-scale analysis identifies an area as ‘at risk’ of large hydrological changes and potentially significant on ecological, economic and/or sociocultural values, local-scale information may be necessary to constrain the predictive uncertainty to something more representative of local conditions, and more appropriate for informing the local management response. For example, the presence of a local that is not a feature of regional groundwater model may reduce potential near-surface hydrological and ecological impacts inferred using the regional model. This should be taken into account in any conditions or management response.
The quantitative representation of the predictive uncertainty through probability distributions allows BAs to consider the of impacts with a specified magnitude and underpins the impact and risk analysis. Sources of uncertainty that cannot be quantified were considered qualitatively.
188.8.131.52 Integrating ecological complexity with a landscape classification
are complex landscapes with a wide range of ecological systems that interact with human activities. The systems can be discrete, overlapping or integrated. Because of this complexity, a direct analysis of each and every point, or , in the landscape across the subregion is not currently possible. Abstraction and a systems-level classification can manage the challenges of the dimensionality of the task.
The defines a set of as with characteristics that are expected to respond similarly to changes in and/or due to coal resource development. The spatial coverage of landscape classes across the subregion is exhaustive and non-overlapping, and there is expected to be less heterogeneity in the response within a landscape class than between landscape classes. This reduces the complexity for each subregion and is appropriate for a regional-scale assessment. The landscape classification characterises the landscape and focuses on the key processes, functions and interactions for the individual landscape classes. The landscape classification for the builds on existing well-accepted classifications and is described in detail in companion product 2.3 for the Namoi subregion (). The landscape classification allows effort to be focused on those landscape classes that are water dependent.
The assessment of on and to water-dependent ecological relies heavily on the landscape classification. Potential impacts to individual assets are assessed via the landscape classes where they are located. For each of those landscape classes, the assessment is based on the qualitative mathematical models for those landscape classes and the indicators of hydrological change or ecosystem change that experts have identified as important for that landscape class.
184.108.40.206 Ruling out potential impacts
An important outcome of the multiple components of the is to identify areas of the that is unlikely to impact. The Assessment team rules out potential impacts where possible, both spatially and in terms of specific or , so as to concentrate on where potential impacts have a higher probability of occurring. This process starts with the identification of a (PAE) for a subregion or that is a conservative spatial boundary, encompassing areas of potential impact based on the most likely coal resource developments within the subregion or bioregion. The is where assessment effort is focused, including in the collation of , the creation of to summarise key surface , and the construction of numerical surface water and groundwater models.
Results of the hydrological modelling provide the details to finalise the ‘assessment extent’ used in the impact and analysis. No changes to the Namoi PAE were necessary, and the for the is the same as the PAE identified in companion product 1.3 for the Namoi subregion ().
Results of the hydrological modelling also define the (Section 3.3.1). Potential impacts on water-dependent landscape classes and are ruled out if they are wholly outside the zone of potential hydrological change. Thus, the zone identifies landscape classes that should be investigated further through qualitative mathematical modelling and receptor impact modelling and, as required, through use of local information to better define the risk and appropriate management response. Equally important, this logical and consistently applied process rules out landscape classes or water-dependent assets where potential impacts due to additional coal resource development are (less than 5% chance) to occur.
Product Finalisation date
- 3.1 Overview
- 3.2 Methods
- 3.3 Potential hydrological changes
- 3.4 Impacts on and risks to landscape classes
- 3.4.1 Overview
- 3.4.2 Landscape classes that are unlikely to be impacted
- 3.4.3 'Floodplain or lowland riverine' (non-Pilliga) landscape group
- 3.4.4 'Non-floodplain or upland riverine' (non-Pilliga) landscape group
- 3.4.5 Pilliga riverine (upland and lowland)
- 3.4.6 Potentially impacted landscape classes lacking quantitative ecological modelling
- 3.5 Impacts on and risks to water-dependent assets
- 3.6 Commentary for coal resource developments that are not modelled
- 3.7 Conclusion
- Contributors to the Technical Programme
- About this technical product