**4. Implementation of the framework**

The Surat CMA was declared in 2011. This was followed by the preparation and release of three iterations of assessments through UWIR 2012, UWIR 2016 and UWIR 2019.

The first cycle of assessment was completed within 12 months of the establishment of the CMA, primarily using the existing knowledge and secondary data sources to build a regional groundwater flow model and design management strategies. This was followed by a research program for the following three-year cycle, providing the foundation for the subsequent assessments in 2016 [2] and 2019 [3].

#### **4.1 Hydrogeological assessment**

A range of hydrogeological assessments were undertaken relating to the geology of the Surat Basin and aquifer interconnectivity. These investigations, in combination with complementary assessments by others, were then used to build a regional hydrogeological conceptualisation that underpinned the construction of a regional groundwater flow model and management strategies.

In the latest iteration, the geological model has 22 layers covering all major formations of the Surat and southern Bowen basins [15]. The geological model was based on the primary lithostratigraphic interpretation of geophysical logging from some 7,000 P&G wells. Primary interpretation ensures consistency in stratigraphic interpretation across the whole basin.

Most of the water use in the Surat Basin is for stock and domestic purposes, which is unmetered. Indirect estimates of water use were therefore made by developing a methodology utilising demand-based estimates per bore, while taking into account the availability of alternative water supply sources and seasonal variations [3]. The new methodology resulted in an estimate of groundwater use for stock and domestic purposes in the Surat Basin of 41,000 ML/year.

A major study was also undertaken to assess the connectivity of the overlying alluvial aquifer – the Condamine Alluvium [16]. The study involved multiple lines of investigation including drilling, coring, long-duration pump testing and monitoring. It concluded that there is a low level of connectivity.

A range of other complementary assessments was also undertaken including recharge estimation, fault characterisation and inter-aquifer connectivity. These studies provided the basis of a new regional conceptualisation [17].

#### **4.2 Impact modelling**

The most recent model developed by OGIA for the cumulative impact assessment in 2019 [15] represents the third iteration of conceptualisation, construction and calibration, based on information and data collected from monitoring and strategies developed in previous iterations. Each iteration of the model is informed by a revised understanding of key hydrogeological processes or concepts operating within the Surat CMA at the time.

The domain of the current model covers an area of around 460 × 650 km, encompassing the entire Surat CMA. The model domain is discretised into cells of 1.5 × 1.5 km areal extent, with 34 layers. The model is designed to simulate groundwater flow within the Surat Basin sequence and overlying alluvial formations in the Surat CMA, and within the CSG-producing Bandanna and Cattle Creek formations of the Bowen Basin.

The model was developed using the MODFLOW-USG simulator with a range of modifications to accommodate specific and unique processes associated with CSG

#### *Cumulative Groundwater Impact Assessment and Management – An Example in Practice DOI: http://dx.doi.org/10.5772/intechopen.95278*

extraction: the approximation of coal desaturation and dual-phase flow effects using a modified Richards equation formulation; use of a "descending drain" methodology to extract water from coal measures; recognition of the gas-filled status of CSG production wells and the consequential steep vertical gradient of water head in the vicinity of these wells; representation of 16 major fault systems in the groundwater model structure; and a new approach to parameterisation which maximised the use of the extensive lithological and other data from CSG well drilling activities.

Regional hydraulic properties were derived using numerical permeameters. The model was calibrated against a number of additional observation types including: monthly actual CSG extraction; vertical head differences between stratigraphic units; observed drawdowns; expected vertical head gradients; and saturations within the target formation.

The regional groundwater flow model was used to predict the impact of the cumulative industry development profile on groundwater pressures in aquifers. The profile was prepared based on information available at the time about historic and planned development of the individual CSG projects.

The current assessment [3] revealed that by the end of 2021, a total of 222 bores would be affected by a groundwater pressure reduction of more than five metres; these are referred to as Immediately Affected Area (IAA) bores. In the long term, a total of 571 water bores are predicted to be affected; these are referred to as Longterm Affected Area (LAA) bores.

#### **4.3 Impact management**

For all 222 water supply bores that are predicted to be impacted in the short term, i.e. IAA bores, follow-up actions are assigned to individual tenure holders – the responsible tenure holders (RTH) – based on certain rules. Each bore initially requires a bore assessment by the RTH to assess if the predicted impacts are likely to affect the intended purpose of the bore. If it is found that a bore water supply is likely to be impaired, then the RTH will have to reach a proactive 'make good' agreement with the bore owner.

The arrangement also involves the design and implementation of a monitoring network. Initially, in the first iteration, the UWIR 2012 specified the progressive installation of a network of 498 monitoring points across the Surat CMA. In recent iterations, the planned network has now been enhanced to 622 groundwater-level monitoring points and 103 water-quality monitoring points, of which about 500 are currently installed. The network is an extensive undertaking by tenure holders, considering the formations monitored are typically 200 to 1,000 m below ground. The UWIR assigned responsibilities to individual CSG companies for implementing individual parts of the regional monitoring network and reporting monitoring data.

The strategy for managing GDEs is primarily imbedded in a spring impact management strategy. Source aquifers for springs were established through investigations to predict impacts. Where the source aquifer for an identified spring was not known with confidence, the predicted pressure impact at the location of the spring was taken to be the maximum predicted pressure impact in any aquifer below the location of the spring.

#### **4.4 Stakeholder consultation**

OGIA undertakes formal and informal engagement activities to assist communities to understand the assessments that have been made, and to hear community views on groundwater impact issues. After the publication of a consultation draft UWIR, written submissions are invited and public meetings are held at community centres around the basin to hear questions and provide explanations, before finalising the UWIR. Current views on issues relating to groundwater impacts from CSG development can best be gauged by the submissions received on the consultation draft of the current UWIR 2019 [18].

Landholder and community groups have raised a range of issues relating to: the effect of both CSG and non-CSG groundwater take on the sustainability of the GAB, particularly in the Hutton Sandstone; the effect of climate change; the impact of migrating gas in water bores; delays in finalising 'make good' arrangements; the indirect impact of 'make good' bores in the Hutton Sandstone; overall impacts of CSG development; construction of CSG wells; the effect of the modelling scale on predicting impacts in water supply bores; and the inherent limitation associated with the modelling of impacts. There was a general expectation that, although many of the issues are outside the scope of the UWIR, broadening of scope should be considered in the future.

Issues raised during engagements are considered both in finalising the UWIR and in designing and implementing the subsequent research. For example, in 2012, the community raised specific concerns about connectivity between the target coal formation and the Condamine Alluvium. As a result, OGIA launched a research project on improving understanding of the connectivity through an extensive field program for data gathering and analysis. Ongoing community engagement on interim findings and field testing to build community understanding and confidence was an integral component of this program. Similar other engagements have continued, in collaboration with public and private sector organisations.

#### **5. Conclusion**

Extractive resource industries have a potential to impact groundwater resources. Particularly where the development is large-scale and involving multiple operators, the impacts can magnify due to their cumulative effects. In such situations, there are often a number of difficulties in managing impacts due to: different approaches to impact assessment by individual operators; lack of clarity on management responsibilities where impacts may overlap; constantly changing plans for development and evolving knowledge; and lack of community trust in assessments by industry.

These generic issues were well manifested in Queensland, Australia, where large-scale CSG development in 2010 brought them to the surface. In response, an innovative cumulative assessment and management framework applying adaptive groundwater management principles was developed and has been applied since then.

The framework involves an iterative cycle of independent impact assessment using progressively updated data and information, supported through secure funding arrangements. The cyclic assessment underpins progressive revision of strategies for managing impacts and enables identification of knowledge gaps to drive subsequent investigation.

The framework and its implementation are broadly regarded as effective in providing stakeholders with information and a mechanism to address issues relating to groundwater pressure impacts from CSG water extraction. As an independently funded and scientifically focused body, OGIA links assessment with regulatory management arrangements, and in doing so, has been able to build stakeholder confidence. For CSG companies, the framework provides clarity about statutory obligations. The involvement of OGIA reduces concerns about conflicts of interest, benefitting both CSG companies and bore owners.

*Cumulative Groundwater Impact Assessment and Management – An Example in Practice DOI: http://dx.doi.org/10.5772/intechopen.95278*
