**Abstract**

Production of coal seam gas (CSG), or coal bed methane, requires large-scale depressurisation of a target formation by extracting groundwater, which, in turn, has the potential to affect overlying and underlying aquifers. This leads to wideranging stakeholder concerns around the impacts on groundwater assets such as water supply bores, groundwater-dependent ecosystems and connected watercourses. Around 2010, the CSG industry in Queensland, Australia grew rapidly with the expansion of operations in the Surat and Bowen basins by multiple operators. This particularly raised concerns about the cumulative effects, because the target coal seams are part of the Great Artesian Basin – one of the world's largest aquifers. To respond to this challenge, an innovative framework was developed to provide for an independent cumulative impact assessment and to set up arrangements for managing those impacts. This chapter describes the main thrust of that framework.

**Keywords:** coal seam gas, cumulative impact assessment, groundwater management, Great Artesian Basin, groundwater, Queensland, regulatory framework, Surat Basin

## **1. Introduction**

In the Surat Basin of Queensland, Australia, production of coal seam gas (CSG), or coal bed methane as it is known in the Americas, requires extraction of groundwater to depressurise the Walloon Coal Measures (the target formation). CSG has grown to become the dominant source of natural gas in Queensland, Australia, comprising more than 95% of the gas produced and more than 99% of the remaining proved and probable gas reserves [1]. The CSG produced from the Surat and Bowen basins is the feed stock for the liquefied natural gas export industry based in Gladstone. By 2009 to 2011, an unprecedented scale of CSG development was proposed in environmental impact statements (EIS) by four major proponents – Santos Limited, Australia Pacific LNG Pty Limited., QGC Pty Limited and Arrow Energy Pty Ltd – whereby a maximum of about 34,000 CSG wells were proposed in an area of about 37,000 km2 [2].

The target formation for CSG production in the Surat Basin is part of the Great Artesian basin (GAB) – one of the largest groundwater systems in the world. This geology raised issues surrounding impacts of this development on groundwater assets such as water supply bores, groundwater-dependent ecosystems (GDE) and connected watercourses. There are an estimated 22,000 water supply bores in and around the CSG development area, along with a number of ecologically significant springs.

Exploration for CSG commenced in Queensland in the 1980s. Commercial production from the late Permian coal seams of the Bowen Basin commenced around 1995. By the early 2000s, the focus for development had shifted to the overlying Surat Basin, a part of the GAB (**Figure 1**), targeting the Jurassic age Walloon Coal Measures. However, over time, the development plans were revised downward in response to emerging market conditions and resource availability. Based on current

#### **Figure 1.**

*A map showing the Surat Cumulative Management Area boundary in relation to the Surat Basin and the CSG tenures.*

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

development plans, an estimated 21,000 CSG wells will have been constructed by the end of the life of the industry, of which about 7,000 are already in operation [3], extracting some 60,000 ML/year of groundwater from the CSG target formations in the Surat and southern Bowen basins.

This chapter provides some contextual background on the concept of cumulative impacts and related issues, followed by a description of how a framework was developed and implemented for managing those issues. The framework is a good example of proactive and adaptive groundwater management covering a cycle – from identifying issues to assessment and modelling, reporting, implementation and monitoring.

#### **2. Context**

#### **2.1 The concept of cumulative impacts**

The concept of cumulative impacts in water and environmental management is not new, but the context in which it is used varies widely. The term is sometimes used in relation to impacts of a single project on multiple social, environmental and economic factors [4]. In other instances, it is used to refer to impacts from the interaction of multiple activities, and/or the collective impact of many similar activities over time and space [5]. In this chapter, the term 'cumulative impacts' refers to groundwater pressure impacts from multiple CSG projects.

Regional or strategic assessments are often seen as mechanisms to assess cumulative impacts. Many authors have argued that cumulative effects are best assessed in a more regional and strategic context, at the level of strategic environmental assessment (for example, [6–9]). The Government of Alberta, Canada has developed a regulatory framework to better manage cumulative environmental effects from development through a regional planning instrument [10].

Although the term 'cumulative impacts' is not always used explicitly, the combined effects of all consumptive water use have always been considered, typically in catchment-scale and/or aquifer-scale planning for the allocation and management of water resources in Australia, following the 1994 Council of Australian Governments water reform agenda.

#### **2.2 The Surat Basin**

The Surat Basin underlies 180,000 km2 of southeast Queensland. It is connected to the Eromanga Basin to the west, the Clarence-Moreton Basin to the east and the Mulgildie Basin to the northeast. It is a Jurassic to Cretaceous age sequence of alternating sandstones, siltstones and mudstones, with coal seams of economic significance in some areas (**Figure 2**, Video 2) [3]. The Surat Basin overlies the Permo-Triassic Bowen Basin sediments and is overlain by inliers of Quaternary alluvium and Tertiary basalts, particularly in the east. The total thickness of the Surat Basin sequence is about 3,000 m, with sediments deposited on an older erosional surface of the Bowen Basin.

The outcrop is the recharge area, with groundwater flowing generally along the formation dip for the deeper aquifers in confined areas, although there is a significant proportion of flow in outcrop areas northward along the topographic elevations [11, 12]. For the most part, groundwater in the Surat Basin occurs under sub-artesian conditions. Artesian aquifer conditions are only encountered in the southwest corner.

There are some 22,400 private water supply bores within the GAB footprint of the Surat Basin, the equivalent Clarence-Moreton Basin and adjoining parts of the southern Bowen Basin [3]. A majority of these bores access groundwater from the shallower unconsolidated alluvium or tertiary formations. The underlying GAB formations are primarily accessed for agriculture, town water supply and stock and domestic use, totalling 41,000 ML/year.

GDEs, which are associated with springs and baseflow-fed streams and include deep-rooted terrestrial vegetation, occur within the area. Springs are known to source water from some of the GAB formations. Natural groundwater discharge along the outcrop areas also feeds into watercourses and supports flow in dry periods.

#### **2.3 Groundwater management challenges**

Groundwater in the Surat Basin has long been accessed primarily for consumptive use. Long-standing arrangements for managing groundwater had been designed for consumptive use. The rapid emergence of the CSG industry, which extracts large amount of incidental groundwater (non-consumptive use) to depressurise coal seams, challenged those arrangements. For context, average CSG-related extraction over the life of the industry is expected to be about 51,000 ML/year [3], although these estimates have been declining over the years.

There are significant regional aquifers above and below the Walloon Coal Measures (**Figure 2**, Video 2) and therefore depressurisation for CSG production could potentially impact water supply bores and GDEs that rely on those aquifers (Video 3).

#### **Figure 2.**

*A 3-D schematic of the Surat Basin sediments showing the CSG target formation and its relationship with surrounding formations [3].*

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

Although the primary groundwater management concern was the management of the impacts of CSG water extraction on groundwater supplies and GDEs, there were also other concerns about non-pressure-related impacts on groundwater resources, such as: the potential for groundwater pollution from drilling activity; the beneficial use of the formation water extracted during development; and social impacts associated with the large workforce operating in the area [13]. These other concerns are beyond the scope of this chapter.

There was significant resistance to proposed CSG development from landholders and the community in the early stages [14]. Landholders with water supply bores in and around the CSG development areas were seeking better understanding of impacts and appropriate compensation, including provisions for alternative supply in advance of impacts occurring. There were also concerns about long-term impacts, monitoring and questions about the independence of scientific assessments presented in EISs by the CSG industry. At the same time, the industry was also seeking clarity on responsibilities where impacts may overlap.

## **3. Development of a groundwater management framework**

To respond to the challenges outlined earlier, the existing regulatory arrangements were reformed to provide for a framework for independent assessment and management of cumulative impacts from petroleum and gas (P&G) development, including CSG. This was done in the context that, in Queensland, P&G tenure holders have a right to take groundwater that is unavoidably taken during the production of P&G. This right was made subject to certain obligations on managing impacts.

Development of the framework followed some key principles, such as: the cumulative assessment must be by an independent entity on a full-cost-recovery basis; the assessment and management arrangements must be periodic to adapt to evolution of knowledge of groundwater systems and changes to development; tenure holders must take the responsibility for making good the impacts on water supply bores; the management actions must be proactive; and there should be regular monitoring and reporting.

Two core elements of the framework that was established were: the establishment of an independent entity – the Office of Groundwater Impact Assessment (OGIA) – to displace proponents' responsibilities for preparing Underground Water Impact Reports (UWIR) in a declared Cumulative Management Area (CMA); and an ongoing three-yearly cycle of proponents preparing UWIRs containing impact assessment and management strategies, including the monitoring arrangements.

The entire intensive CSG development area, covering about 450 × 550 km, was declared a CMA (the Surat CMA) (**Figure 1**, Video 1). OGIA is tasked with assessing the cumulative groundwater impacts from P&G development in the Surat CMA. The costs associated with OGIA performing its functions are recovered through an annual levy payable by the tenure holders.

The technical assessment and arrangements for managing cumulative impacts are required to be reported by OGIA every three years in a UWIR. It is required that the report: includes an assessment and prediction of cumulative impacts in all affected aquifers; identifies the impact area for each aquifer; provides a list of affected water supply bores and GDEs; and outlines management arrangements such as the monitoring, make good of water supply bores, mitigation of impact on GDEs and assignment of responsibilities to tenure holders.
