The assessment method addresses uncertainties related to the precise location, scale and nature of future development activities to allow government and the community to better understand potential impacts on water and the environment at a regional scale. Systematic evaluation of confidence for each link in the causal network identifies knowledge gaps related to the cause-and-effect relationships, materiality thresholds and mitigation strategies in the assessment. A detailed description of knowledge gaps related to causal pathways from unconventional gas resource development to individual endpoints is detailed for each endpoint ( see causal network ) and reported in the assessment summary for the Cooper GBA region.
The details about the nature and characteristics of a future unconventional gas resource development scenario are uncertain, particularly at a local scale. This affects many aspects of the assessment, including:
- The scale, location and timing of future development. There needs to be an economically viable level of infrastructure investment to connect the resource to market (such as production of hundreds of terajoules per day from hundreds of wells over the development lifetime). Development location influences the interactions with environmental, economic, cultural and social values. Location and timing of development affects rate-dependent potential impacts, such as water extraction and vegetation removal.
- The technologies used for future development. The amount and quality of water required for drilling and hydraulic fracturing, the chemicals used for those activities, and the exact nature of the surface footprint (such as number of wells per well pad and the spacing of well pads) will change as new technologies develop. Practices ensuring well integrity and management of drilling and hydraulic fracturing fluids, and the chemicals used in them, are likely to maintain or improve upon current standards.
- The volume and treatment of flowback water. The amount and quality of flowback water from hydraulic fracturing operations and the technologies available for its treatment, ultimately influence how much flowback water can be reused, recycled for subsequent hydraulic fracturing operations, or whether final disposal is required.
- Future interactions with other industries. High-resolution quantitative information on both the state of the environment and the processes acting on the landscape is needed to assess interactions with other drivers of system change (for example, agriculture, tourism, infrastructure development, climate change), which are not in the scope for the GBA.
- How thresholds of material change will be altered due to climate change.
- Ecological processes. Better understanding of the occurrence, distribution and sensitivity to development for each endpoint in the Cooper GBA region is needed, including detailed assessment of habitat requirements of species, estimates of the population size, reliance on surface water, optimum fire management regimes, and impacts of increased competition and predation by invasive species.
Knowledge gaps are prioritised where there is low confidence in cause-and-effect relationships, materiality thresholds and/or mitigation strategies. Specific knowledge gaps identified in the assessment include:
- How habitat is used by protected fauna varies in space and time. Materiality thresholds for links related to key ecological processes such as competition and predation, ecosystem burning, habitat degradation, fragmentation and loss or mortality of native species for individual species are poorly understood.
- Toxicity of chemicals used for future development, and relative toxicity of daughter compounds from chemical reactions and degradation. Limited data are available on the chronic toxicity of these chemicals, which is either largely unknown or extrapolated from acute toxicity studies. Other knowledge gaps that highlight the need for local- scale assessment include the behaviour of contaminants in wetlands and waterbodies, including attenuation of contaminants, changing concentrations with pulsed releases in boom-and-bust ephemeral systems, and partitioning and accumulation in sediments. Better understanding of the materiality thresholds for species or functional groups of species, based on how a single spill at a local scale impacts a protected matter at a large scale, in terms of species population persistence and fitness or wetland health would improve the assessment.
- Management and disposal of brines from treated flowback water at regulated waste disposal facilities. It is not known whether or how this will change in the future, and what additional avoidance and management techniques are needed to reduce the likelihood of impacts if local disposal were to be an option.
- Changes to habitat and water requirements of individual species with climate shifts, particularly increased night-time temperatures. Effect of noise and light pollution for cryptic or nocturnal species is also largely unknown.
While the assessment is designed to be structured, robust and transparent, there are limitations for both the method and assumptions made by the assessment team, including representation of the following:
- Non-linear effects or time-varying cause-and-effect relationships that capture the boom-and-bust dynamics of a region. It is not a trivial exercise to represent the complex reality of ecological and hydrological systems in a directional acyclic graph (the graphical causal network). One of the most challenging aspects is that feedback loops cannot be represented. Feedback loops are an essential feature of complex natural systems. When represented in a graph, however, it is no longer possible to unequivocally establish causal pathways between starting and ending nodes.
- Adverse impacts and benefits. In line with guidelines under the EPBC Act (Commonwealth of Australia, 2013), where an action may have both adverse and beneficial impacts, only adverse impacts are assessed. However, positive effects are also evident. For example, while new roads in a landscape may increase bushfires due to an increased likelihood of accidental ignition, roads can also act as firebreaks, limiting the spread of bushfires. To determine net benefits of an action, a more quantitative estimate of the likelihood and magnitude of positive and negative effects is needed.
- Ecological, economic and/or social values to be protected. Environmental values are represented in the assessment by key ecological and hydrological systems in the Cooper GBA region. The 12 protected fauna and flora listed under state or national legislation were prioritised for assessment based on the importance of the Cooper GBA region to the continued persistence of each species. Significant cultural assets, including the Burke, Wills, King and Yandruwandha National Heritage Place and a range of Indigenous peoples’ values are considered in the assessment of landscapes and protected areas. However, while the assessment takes a values-based perspective, more detailed assessment of potential impacts on cultural heritage values are beyond the scope of the GBA Program and are not directly represented in the causal network.
- Cumulative impacts of multiple stressors from multiple industries. Future studies could extend the causal network to other industries, such as pastoralism or tourism, to assess the impacts of multiple activities and stressors on processes and endpoints. A quantitative assessment of the magnitude and likelihood of cumulative impacts is not possible without detailed baseline and future development scenarios.
- Ecological processes and interactions. Links between activities, stressors, processes and endpoints are unable to capture all of the nuance of more detailed ecological conceptual models, which may cause unintended assessment outcomes. For example, the stressors storage ponds , vegetation removal , vehicle movement link to the mortality of native species process node, which links to all of the fauna and flora endpoint nodes. As such, increased drowning of native species in storage ponds decreases persistence of protected fauna and flora. In future, mortality of mobile and sedentary species could be assessed separately. Increased herbivory associated with the stressors artificial water sources and invasive herbivores is represented by the process competition and predation .
The regional-scale assessment allows regulators and proponents to better focus and coordinate future assessment, management and monitoring. For example, the spread of invasive species may amplify key threatening processes that impact on the persistence of threatened species in the region. Mitigation and management of invasive species is best achieved via coordinated industry-wide approaches that work with existing land managers and natural resource management programs, including whole-of-life-cycle planning and risk management.
The causal network allows systematic examination of potential impacts on water and the environment associated with unconventional gas development activities. At a practical level, this may be useful in the formulation of terms of reference for environmental impact assessments of individual projects, ensuring that the identified pathways of concern are addressed. Importantly, due to its whole-of-region approach, the causal network for the Cooper GBA region is not a substitute for careful assessment of individual unconventional gas development projects in the Cooper GBA region under Australian or state environmental law. Such assessments may use finer scale groundwater and surface water models, consider impacts on matters other than water and the environment, and include interactions with neighbouring developments in greater detail.
Ecosystem extent and condition accounts capture the spatial and temporal trends in the natural resources and services to improve quantification and conceptualisation of the biophysical environment at a regional scale. Baseline accounts compiled for this assessment can be updated to track trends in extent and condition at a regional scale. Improved remote sensing technologies using relative benchmarking approaches (Hobbs et al., 2017; Donohue et al., 2021), when combined with site-scale monitoring data, can clarify trends in ecosystem extent and condition.
At a local scale, the calibrated hydrodynamic flood inundation model can evaluate how flood characteristics may change under future development and climate change scenarios. Design of civil works – such as a watercourse crossing, road, dam or a diversion – that could change flow paths on the floodplain and in small flood runners can be avoided through compliance with state and regional regulations at the design stage.
The assessment method is designed to be updated. New nodes, links and endpoints can be added to the causal network when new data and knowledge become available or the focus of the assessment changes. Link evaluations (and their spatial grids) can be updated to reflect improved knowledge, reduced uncertainty, new mitigation strategies or to better represent local-scale datasets, such as modelled groundwater drawdown. As individual gas resource development projects are assessed, the causal network can be updated to allow proponents and regulators to continue to prioritise future assessment, mitigation and monitoring activities.
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- At a glance
- Explore this assessment
- Executive summary
- 1 About the assessment
- 2 About the region
- 3 Assessment, mitigation and monitoring
- 4 Potential impacts on water
- 5 Potential impacts on the environment
- 6 Potential impacts on protected fauna and flora
- 7 Conclusion
- Contributors to the Program