The 130,000 km2 Cooper GBA region contains diverse habitats that support important environmental, cultural, social and economic values that interact and respond to the episodic, irregular and extreme boom-and-bust periods that are characteristic of the Channel Country in Queensland and South Australia (Figure 17). The braided channels, vast floodplains and terminal lakes of Cooper Creek include internationally and nationally listed wetlands, as well as regionally protected areas. The assessment considers potential impacts due to unconventional gas resource development activities on these landscapes, aquifers, protected areas and 12 threatened species (7 fauna and 5 flora). These endpoints were prioritised based on the importance of the Cooper GBA region to each protected matter.
FIGURE 17 Scrubby Camp Waterhole on Cooper Creek, west of Innamincka in South Australia
Credit: Geological and Bioregional Assessment Program, Russell Crosbie (CSIRO), November 2019
Element: GBA-COO-3-660
The assessment found that compliance with existing regulatory and management controls can mitigate all potential impacts due to unconventional gas resource development identified in the Cooper GBA region. This includes national and state legislation, regulatory guidelines and approval conditions, industry best practice and management plans. The regional-scale assessment provides independent science to underpin coordinated management of potential impacts across governments, industry, land users and the community. The geological and environmental knowledge, data and tools will enable regulators and proponents to focus local-scale assessment, management and monitoring.
Impact assessment
The complex and interconnected nature of the natural environment and unconventional gas resource development activities were assessed at a regional scale using causal networks. Causal networks are graphical models that describe the cause-and-effect relationships between development activities and the values to be protected (referred to as endpoints); for example, the internationally protected Coongie Lakes wetland. The assessment uses spatially explicit and systematic evaluations of the likelihood and consequence of environmental harm, and availability of control and mitigation strategies. An online tool presents the comprehensive information base underpinning the assessment.
Confidence in the impact assessment is generally high where there is evidence to support the evaluations. Where there is insufficient knowledge to support robust and meaningful evaluations, the precautionary principle is applied so that uncertainty about potentially serious hazards does not lead to underestimation of impacts.
No pathways of ‘potentially high concern’ are identified in the causal network. This means that all potential impacts identified by the assessment can be mitigated through compliance with existing regulatory and management controls.
The assessment is based on a maximum development scenario matching current conventional gas production in the Cooper GBA region of 92 petajoules per year over a 50-year period. Under this scenario, a projected 1,180 petroleum wells are estimated to disturb a total area of 27 km2 spread over up to 7,350 km2 including undisturbed areas between well pads, roads and seismic line, or less than 6% of the total area. This maximum development scenario would require the extraction or reuse of up to 20 gigalitres of water over a 50-year development period, equivalent to approximately 400 megalitres per year for 50 years.
Potential impacts at the surface
Pathways between unconventional gas resource development activities and endpoints of ‘potential concern’ are primarily related to activities that create a disturbance at the surface (transport of materials and equipment, civil construction, decommissioning and rehabilitation, and seismic acquisition). The pathways of ‘potential concern’ connect these activities with the endpoints – all vegetation communities (dryland, floodplain, riparian and wetland), protected areas, protected flora and habitat of protected fauna – reflecting how surface disturbance has the potential to impact on these endpoints. These pathways of ‘potential concern’ warrant local-scale studies to inform decision-making and enable coordinated management of potential impacts. They include the following:
- Surface water contamination in 12% of the Cooper GBA region, as spills and leaks could spread rapidly and accumulate in sediments. Contamination of shallow groundwater is of ‘potential concern’ in less than 1% of the Cooper GBA region where groundwater is close to the surface (less than 9 m deep). Existing regulations, approval conditions and industry practices are effective in preventing, or ensuring quick remediation of, spills and leaks. There is insufficient species-specific information to establish robust thresholds of material change for the toxicity of potential pollutants for protected fauna. Therefore, soil and surface water contamination are conservatively assessed as of ‘potential concern’ for all fauna-related endpoints.
- Obstruction of surface water flows in 6% of the Cooper Creek floodplain, or 1.2% of the total area. Licensed surface water extraction – approximately 2% of annual flows – will not impact on flows in the river or scouring or flooding in Cooper Creek. Changes to flood extent could affect agricultural productivity and the condition of protected areas including the Channel Country SEA and Coongie Lakes, as well as habitat for the grey grasswren and Australian painted snipe, braided sea heath and Sclerolaena walkeri. Confidence in existing avoidance and mitigation strategies prescribed in state regulations and industry management plans is high.
- Direct impacts of surface disturbance could occur in 25% of the Cooper GBA region due to soil compaction, storage ponds, vegetation removal and vehicle movement. Habitat degradation is of ‘potential concern’ in 28% of floodplain, wetland and riparian areas and could impact on agricultural productivity and the condition of protected areas including the Channel Country SEA and Coongie Lakes. There is high confidence in existing protections, including legislated, ‘no-go’, areas, and industry controls can minimise future impacts on riparian vegetation. Mitigation strategies to manage site disturbance are well established. However, knowledge to determine robust and meaningful material change thresholds for processes affecting habitat is limited.
- Indirect impacts of surface disturbance could occur in 27% of the Cooper GBA region due to artificial water sources, introduced plants, predators and herbivores. Competition, predation, and habitat degradation, fragmentation and loss are of ‘potential concern’ in 23% of dryland areas, which could affect the kowari, yellow-footed rock-wallaby, and possibly the night parrot. Effective mitigation strategies for indirect impacts require coordinated regional responses and management plans.
Potential impacts below the surface
Pathways associated with development activities (drilling, hydraulic fracturing, well decommissioning and rehabilitation, production of hydrocarbons, and waste and wastewater management) could cause aquifer contamination or drawdown. Potential impacts of ‘potential concern’ below the surface that can be mitigated include the following:
- Aquifer contamination in less than 1% of the Cooper GBA region. Due to modelling constraints, aquifer contamination cannot be ruled out within 500 m of an existing water bore or groundwater-dependent ecosystem. There is high confidence that aquifer contamination can be mitigated through ongoing compliance with existing regulations and approval conditions developed over more than 50 years of conventional oil and gas production in the Cooper Basin. Hydraulic fracture modelling shows that natural barriers, such as the Nappamerri aquitard, protect overlying aquifers from contamination due to compromised aquitard integrity in the Cooper Basin. The risk of hydraulic fractures intersecting an aquifer can be mitigated by controls in existing regulations, sufficient understanding of the baseline geological and environmental systems, and industry practices. Aquifer contamination due to compromised well integrity is of ‘very low concern’ in the Cooper GBA region based on findings from domestic and international inquiries, as well as historical compliance reports for Cooper Basin petroleum wells. Stringent approval and management requirements, including national guidelines, state regulations and industry waste management plans, give confidence that waste disposal is of ‘low concern’ in the Cooper GBA region.
- Groundwater drawdown in less than 1% of the Cooper GBA region. Due to modelling constraints, drawdown in the Cadna-owie – Hooray aquifer in excess of 2 m cannot be ruled out within 1 km of existing bores and where the saturated aquifer thickness is less than 150 m in the south-west of the Cooper GBA region. For groundwater-dependent ecosystems that access the shallow unconfined aquifers in the west of the Cooper GBA region, drawdown in excess of 0.2 m in the Cenozoic and Winton-Mackunda aquifers cannot be ruled out where the saturated aquifer thickness is greater than 20m. Alternative water sources, such as groundwater from other aquifers, or reuse of co-produced water, could avoid potential impacts in these areas.
Potential impacts on the environment
Environmental values in the Cooper GBA region are represented by agricultural productivity, 4 key vegetation communities (dryland, floodplain, riparian and wetland; Figure 12) and 9 protected areas. This includes nationally and internationally listed wetlands, regionally protected areas and permanent waterholes.
Riparian ecosystems provide important connections between terrestrial and aquatic habitats and include parts of key ecological assets such as the Ramsar-listed Coongie Lakes, DIWA- listed wetlands and Channel Country SEA, as well as plants and animals of cultural significance for Indigenous peoples. Riparian areas are relatively undisturbed, which reflects the greater degree of protection for riparian areas than for wetland or floodplain areas. Potential impacts for riparian ecosystems could occur through direct impacts, such as soil compaction, vegetation removal and vehicle movement. However, existing measures to protect riparian areas are not focused on preventing indirect impacts that occur beyond riparian areas, such as invasive plants and predators or accidental release of chemicals into surface waters.IRiparian and wetland ecosystems are closely linked to Indigenous peoples in the region, with plants and animals being significant from cultural and economic perspectives. For example, the iconic river red gum (E. camaldulensis) not only provides a range of ecosystem services such as bank stabilisation and the provision of habitat, but also provides food, timber for tools and utensils, and medicines for Indigenous peoples. Satellite monitoring of water use on the floodplains and wetlands, and by fringing riparian vegetation along Cooper Creek showed that floodplain soils and vegetation use more water (77%) than the high ecological value wetlands, waterholes and fringing riparian vegetation, which account for less than a quarter (23%) of total water use.
Wetland ecosystems are extensive in the Cooper GBA region and include key ecological assets such as the Ramsar-listed Coongie Lakes, DIWA-listed lakes and wetlands, as well as habitat for the grey grasswren (Amytornis barbatus barbatus) and the Australian painted snipe (Rostratula australis), and plants and animals with significant cultural and economic values for Indigenous peoples. Floodplains are extensive in the Cooper GBA region and provide habitat for a range of species including plants such as braided sea heath, Scleroleana walkeri and Xerothamnella parvifolia. Water regimes – particularly the frequency, extent and duration of flooding – control the structure and dynamics of floodplain ecosystems. Flooding provides a significant boost to the productivity of the region, particularly the pastoral industry which relies on grazing on natural pastures.
Field and modelling studies to address knowledge gaps identified in Stage 2 (Section 7.1 in Stage 2 baseline synthesis and gap analysis (Holland et al., 2020)) include the following:
- Light detection and ranging (LiDAR) aerial surveys and 2D hydrodynamic flood inundation model. Cooper Creek floodplain spans across Queensland and South Australia, is large (about 32,000 km2) and floods frequently. It has extremely complex terrain, very low gradients and little observed data. Aerial surveys were flown across the Cooper Creek floodplain and the Thompson and Barcoo river systems to capture digital elevation data. There is good agreement between the calibrated 2D hydrodynamic flood inundation model (MIKE21FM) and satellite data for historical floods. The model can evaluate how flood characteristics may change under future development and climate change scenarios in one of the most complex floodplains in the world.
- Regional-scale biodiversity persistence modelling. While intense localised impacts on habitat (for example, roads, fence lines, seismic lines and well pads) are important in large regions, these are dwarfed by land management across vast areas. The intact landscape of the Cooper GBA region supports relatively high biodiversity (greater than 0.9) values. Trends vary between years with rainfall but are generally stable. These data can help establish baseline environmental conditions, detect change and monitor impacts within a natural capital accounting framework.
- Vegetation condition, estimated using satellite imagery from 2001 to 2018, provides estimates of extent and condition of vegetation communities for natural capital accounting. A 12 to 41% decrease in vegetation cover was detected near existing gas extraction wells a year after well establishment, which started to recover after about 4 years, and had recovered to pre-development condition after 5 to 7 years. Rapid decreases in vegetation cover of up to 60% after fire were observed, with recovery periods in excess of a decade.
Potential impacts on protected fauna and flora
Key threatening processes for the 12 protected flora and fauna species could be amplified by future unconventional gas resource development without implementation of appropriate mitigation, management and monitoring measures. These processes are of ‘potential concern’ in approximately 30% of the Cooper GBA region and include habitat degradation, fragmentation and loss; competition and predation by invasive species; and changed fire regimes. Unconventional gas resource development may also introduce threatening processes that are not currently recognised and for which there is less knowledge, such as noise and light pollution, soil compaction, and contamination that could cause the pollution of soil and water.
Habitat degradation, fragmentation and loss is recognised, based on existing conservation advice and recovery plans, as a threatening process for the Australian painted snipe, grey grasswren, plains-wanderer, kowari, dusky hopping-mouse, yellow-footed rock-wallaby and braided sea heath, and is a suspected threat for remaining species in the region. Key stressors include vegetation removal for infrastructure and the spread of invasive species, particularly those likely to lead to habitat degradation such as introduced herbivores or pigs.
Predation by cats and foxes is recognised as a key threatening process for 4 of the 7 protected fauna species: the plains-wanderer, kowari, dusky hopping-mouse and the yellow-footed rock- wallaby. While there is less supporting evidence, it is likely that predation is important for the other 3 fauna species in the region: the Australian painted snipe, grey grasswren and night parrot. In addition, competition with feral herbivores for resources, such as food and shelter, is a key threatening process identified for the night parrot, dusky hopping-mouse and yellow-footed rock-wallaby.
Altered fire regimes are assessed as of ‘potential concern’ in 30% of the Cooper GBA region and for all protected species in the assessment. Increased average temperatures, increased number of hot days (more than 35 °C) and shifting rainfall regimes combine to increase risks to biodiversity associated with fire. Changes in fire regimes are identified as important threatening processes for the grey grasswren, night parrot, plains-wanderer and yellow-footed rock- wallaby. Some species such as the grey grasswren or the night parrot require habitats that are relatively free of fire for long periods. However, relationships between species persistence and fire for many species are unclear. It is suspected that altered burning regimes are likely to have direct (such as mortality) and indirect (such as habitat modification) impacts on all species in the Cooper GBA region.
Reduced flood duration and extent is assessed as of ‘potential concern’ for 2 endangered bird species – the Australian painted snipe and the grey grasswren – but is not identified as a direct threat in existing conservation advice and recovery plans. Where knowledge of plant biology and water requirements is limited, the precautionary principle is applied, and changes to floodplain inundation are assessed as of ‘potential concern’ for braided sea heath, Indigofera oxyrachis and Xerothamnella parvifolia.
Soil and surface water contamination are conservatively assessed as of ‘potential concern’ for all fauna-related endpoints as there is insufficient species-specific information to establish robust materiality thresholds for the toxicity of potential pollutants on the 7 protected fauna species. Assessment of potential impacts on native fauna due to soil and surface water contamination considers population size, habitat extent, proximity to water, water requirements and species mobility.
Noise and light pollution can have significant impacts on all animal taxa. Due to considerable uncertainty, noise and light pollution is assessed as of ‘potential concern’ in 25% of the Cooper GBA region. Noise and light pollution may impact on cryptic (for example, the Australian painted snipe) or nocturnal species (for example, the night parrot, kowari and dusky hopping-mouse). Noise and light pollution are not currently recognised as key threatening processes for these species.
