The groundwater and surface water resources in the central-eastern part of the Galilee subregion are utilised by the local population for a variety of purposes. These include town water supplies (e.g. the townships of Jericho and Alpha), stock and domestic supplies, and some minor irrigation usage (see companion product 1.5 for further information on water use in the Galilee subregion (Evans et al., 2015)). Consequently, the region’s water resources have an intrinsic economic value, and this may potentially be impacted by the proposed coal resource developments planned for the Galilee Basin. For example, groundwater drawdown caused by dewatering coal mines may reduce water levels within a bore, potentially increasing pumping costs or, at worst, causing an existing bore to run permanently dry. The management arrangements and/or infrastructure that control the access and supply of water resources in the Galilee subregion provide the foundation for defining the register of economic water-dependent assets (Bioregional Assessment Programme, 2017).
Most of the economic water-dependent assets within and around the Galilee subregion’s zone of potential hydrological change are associated with the Great Artesian Basin (GAB). During the time that the various stages of the BA for the Galilee subregion were being undertaken, the management of the Queensland part of the GAB was provided for by the Water Plan (Great Artesian Basin) 2006, which was implemented through the Great Artesian Basin Resource Operations Plan (DNRM, 2012). Consequently, all of the analysis of impacts to economic assets in the GAB reported in this product is based upon the framework of groundwater management areas and groundwater management units that are defined in the Water Plan (Great Artesian Basin) 2006.
Preliminary spatial analysis of bores within and nearby to the zone of potential hydrological change in the Galilee subregion (Figure 77) indicated that there are two groundwater management areas of the GAB that are potentially most affected by drawdown due to additional coal resource development:
- Barcaldine East Groundwater Management Area
- Barcaldine North Groundwater Management Area.
Within the vicinity of the zone of potential hydrological change, one of the main groundwater systems managed under the auspices of both of these groundwater management areas is the Clematis Group aquifer. This is also one of the three aquifers specifically modelled and assessed for this BA. For the Barcaldine East Groundwater Management Area, the Clematis Group is managed as part of the Barcaldine East 4 Groundwater Management Unit, along with the aquifers of the Moolayember Formation, Warang Sandstone and Rewan Group. For the Barcaldine North Groundwater Management Area, the Clematis Group is managed under the Barcaldine North 3 Groundwater Management Unit, along with the Moolayember Formation.
Figure 77 Water management areas in the vicinity of the central-eastern Galilee subregion
The grey shaded zone depicted on this map indicates the spatial extent of drawdown >0.2 m at the 95th percentile of modelling results for the Clematis Group aquifer, based on the probabilistic outputs of the analytic element model for the Galilee subregion. This aquifer is the main Great Artesian Basin hydrostratigraphic unit managed under the Water Plan (Great Artesian Basin) 2006 for which drawdown predictions have been modelled for this bioregional assessment. Modelled drawdown in the Clematis Group aquifer may potentially impact water-dependent economic assets in both the Barcaldine North and Barcaldine East groundwater management areas.
Data: Bioregional Assessment Programme (Dataset 3, Dataset 8, Dataset 9); Queensland Department of Natural Resources and Mines (Dataset 10); Bureau of Meteorology (Dataset 11)
As probabilistic drawdown predictions are available for the Clematis Group aquifer from the groundwater modelling undertaken for this BA, it is possible to evaluate potential mining impacts on the various bores that occur within the Barcaldine East 4 and Barcaldine North 3 groundwater management units. There are also some groundwater economic assets within the zone of potential hydrological change that rely on the near-surface (watertable) aquifer hosted in Quaternary alluvium or other Cenozoic sediments. As BA modelling results are also available for this aquifer, it is possible to assess any potential impacts to groundwater assets that rely on these Cenozoic aquifers. The groundwater modelling also produced probabilistic drawdown estimates for the upper Permian coal measures, although this hydrostratigraphic unit is not specifically managed under the 2006 GAB water plan.
The Assessment team recognises, however, that the 2006 GAB water plan expired in September 2017, and has been replaced by a new water-planning document, namely the Water Plan (Great Artesian Basin and Other Regional Aquifers) 2017. This new water plan for the GAB will be implemented through a water management protocol (replacing the former resource operations plan), known as the Great Artesian Basin and Other Regional Aquifers Water Management Protocol. The new GAB water plan will alter the previous framework of management areas and units against which impacts to economic assets are reported for this BA. Importantly, the GAB and other regional aquifers (GABORA) plan is divided into a new system of groundwater units, which comprises the water from specified geological units that cover parts of the broader plan area. For example, the new Clematis groundwater unit specifies six geological formations, including the Clematis Group, Dunda beds, Moolayember Formation and Rewan Group. The various groundwater units may also be further subdivided into groundwater sub-areas, reflecting specific geographic variations that may exist for a particular geographic unit (e.g. Galilee Clematis and Bowen Clematis sub-areas). Further information about how the new GABORA plans were developed, as well as their intent and variations from the former management arrangements are documented in a Statement of Intent (DNRM, 2017).
In the context of the BA for the Galilee subregion, an important change proposed as part of the new GABORA water plan is the inclusion of the Betts Creek beds in the water-planning framework. This new addition to the management of GAB water resources reflects the anticipated development of the large-scale coal mining operations that will extract coal from (and also dewater) the Betts Creek beds (and associated Permian stratigraphic units). Even though the aquifers of the Betts Creek beds are generally not directly connected to the main aquifers of the GAB, there may be potential for hydraulic connectivity to develop between the Betts Creek beds and the Clematis Group aquifer, due to large-scale mine dewatering or other mining impacts (e.g. subsurface fracturing above underground longwall mining panels). Hence, the GABORA water plan recognises that existing groundwater users in this region would be better served if both of these aquifers are managed under arrangements of a single plan. The Clematis Group aquifer (which was previously included in the 2006 GAB water plan) will continue to be managed under the GABORA water plan.
In addition to the water resources of the GAB, the central and eastern areas of the zone of potential hydrological change for the Galilee subregion occur within the Burdekin Basin Water Plan area (Figure 77). This area is managed under the Water Plan (Burdekin Basin) 2007. The Burdekin Basin Water Plan area is defined on the basis of the surface water catchment of the Burdekin River, and the management strategies incorporated into this plan are generally not concerned with groundwater resources. As shown in Figure 77, there is considerable overlap between the water plan areas of the GAB and the Burdekin Basin, given their differing focus on groundwater resources (GAB) and surface water resources (Burdekin). Most of the area covered by the zone of potential hydrological change in the Galilee assessment extent is part of the Belyando-Suttor Subcatchment of the Burdekin Basin Water Plan (Figure 77).
3.5.3.1 Water-dependent economic assets in the Galilee assessment extent
There are 129 economic water-dependent assets in the water-dependent asset register for the Galilee assessment extent, consisting of 96 groundwater economic assets and 33 surface water economic assets. Both groundwater and surface water economic assets are subdivided into two classes, either ‘water access rights’ or ‘basic water rights’, with most of the latter class being for water supply for stock and domestic purposes. Within the asset register, the individual ‘water access rights’ and ‘basic water rights’ are grouped by their type and spatial location according to the relevant groundwater or surface water management zones or areas to create the assets. As shown in Table 43, each asset comprises a variable number of individual elements, which can range from one element per asset up to many hundreds of elements per asset. Further information about the economic assets evaluated in the BA for the Galilee subregion is provided in companion product 1.3 (Sparrow et al., 2015), with the updated water-dependent asset register available at Bioregional Assessment Programme (2017).
Table 43 Summary of economic assets in the Galilee assessment extent
na = not applicable
Data: Bioregional Assessment Programme (Dataset 1)
Elements associated with surface water assets are mainly water extraction points located on part of a stream network. In the Galilee assessment extent, most surface water assets only occur on the major river channels, such as the Thomson, Barcoo and Flinders rivers. As shown in companion product 1.5 (Evans et al., 2015), the only surface water assets near the central-eastern boundary of the Galilee subregion occur at specific points along the Belyando River and some headwater tributaries. All of the surface water assets in this area are classified as basic water rights that are managed under the Burdekin Basin Water Plan.
Most elements associated with groundwater economic assets are individual bores that have been drilled to extract groundwater from a target aquifer. Many bores in the GAB extract groundwater from deeper confined aquifers (i.e. not the near-surface watertable). Consequently, it is important that the source aquifer of the bore is known when evaluating potential impacts due to additional coal resource development for this BA. Without information relating to the source aquifer of an individual bore, it may not be possible to evaluate drawdown impacts from the BA’s groundwater modelling outputs.
For BA purposes, assessing impacts to groundwater bores in the Galilee assessment extent relies on having reliable information to assess the source aquifer for each bore. The probabilistic groundwater modelling outputs for specific aquifer layers (outlined in companion product 2.6.2 for the Galilee subregion (Peeters et al., 2018)) are then used to evaluate the range of potential drawdown values that may occur for any bore that extracts groundwater from the target aquifer. This analysis method differs from the approach taken for assessing impacts to groundwater-dependent ecological (Section 3.5.2) and sociocultural (Section 3.5.4) assets, as most of these are considered to access the shallow, near-surface aquifer, which is commonly hosted in Quaternary alluvium and other Cenozoic sediments. The important exception to this rule is for some springs (ecological assets) that source their water from deeper confined aquifers (and hence impacts to springs are evaluated in a similar way to the groundwater-dependent economic assets).
The groundwater modelling undertaken for the BA for the Galilee subregion provided probabilistic estimates for groundwater drawdown due to additional coal resource development for three separate aquifer layers, namely:
- Quaternary alluvium and Cenozoic sediments (AEM layer 1) – the geologically young, uppermost aquifer that mainly hosts the regional watertable within the zone of potential hydrological change for the Galilee subregion
- Clematis Group aquifer (AEM layer 3) – a Triassic hydrostratigraphic unit, it occurs in limited areas of outcrop to the west of the seven proposed coal mines of the CRDP for the Galilee subregion, and mostly forms a deeper confined aquifer system that provides water resources to many stock and domestic bores in the Barcaldine North 3 and Barcaldine East 4 groundwater management units
- upper Permian coal measures (AEM layer 5) – the geological unit that contains the coal resources targeted for mining at the seven coal mines in the CRDP for the Galilee subregion. This is the main geological unit that needs to be dewatered at each mine site to allow open-cut and underground mining to occur. However, as previously noted, under the 2006 GAB water plan, the upper Permian coal measures are not specifically managed as part of any groundwater management area.
The focus of much of this section is on evaluating potential impacts to water-dependent economic assets that source water from these hydrostratigraphic layers. Additionally, any other bores registered in the Queensland groundwater bore database that are not included as part of a water-dependent economic asset in the BA are also assessed, providing the source aquifer for the bore is known.
3.5.3.2 Surface water economic assets
There is a single surface water economic asset within the zone of potential hydrological change for the Galilee subregion (BA water-dependent asset number 2311, Bioregional Assessment Programme (2017)). This is a basic water right under the Burdekin River water resource plan, specifically part of the Belyando-Suttor River Subcatchment Area. This single surface water asset has three different basic water right extraction locations that occur within the zone of potential hydrological change, two of which are on the Belyando River and one on its headwater tributary of Native Companion Creek (Figure 78). Using the BA’s modelled surface water predictions (outlined in companion product 2.6.1 for the Galilee subregion (Karim et al., 2018)) for the Belyando River and its main tributaries, an estimate of potential surface water changes at the model nodes nearest these three extraction points is provided in Table 44. This tabulated summary is focused on the predicted reductions in the annual flow volume, as well as the increase in zero-flow days, as these two hydrological response variables are considered most suited to evaluate the potential impacts to these surface water assets.
Table 44 Modelled surface water changes to annual flow and zero-flow days at nodes proximal to basic surface water rights under the Water Plan (Burdekin Basin) 2007 area, within the zone of potential hydrological change for the Galilee subregion
|
Surface water model node |
Location details |
Percent reduction in annual flow volume (%) |
Increase in zero-flow days per year |
||||
|---|---|---|---|---|---|---|---|
|
5th |
50th |
95th |
5th |
50th |
95th |
||
|
40 |
Situated on Native Companion Creek, this is the nearest model node to the southern-most element of the basic surface water right in the Burdekin Water Resource Plan area, within the zone of potential hydrological change (Figure 78). |
<1 |
<1 |
<1 |
2 |
14 |
152 |
|
44 |
Situated on the Belyando River downstream of the southern cluster of modelled coal mines, this model node occurs very close to the central element of the basic surface water right in the Burdekin Water Resource Plan area, within the zone of potential hydrological change (Figure 78). |
<1 |
1.1 |
1.4 |
8 |
51 |
261 |
|
53 |
Situated on the Belyando River downstream of all inflow tributaries directly affected by coal mining, and just upstream of the junction with the Suttor River, this model node occurs very close to the location of the northern-most element of the basic surface water right in the Burdekin Water Resource Plan area, within the zone of potential hydrological change (Figure 78). |
<1 |
<1 |
1.2 |
19 |
77 |
260 |
Data: Bioregional Assessment Programme (Dataset 12)
Based on the results presented in Table 44, some salient observations of the modelled changes to the basic surface water right asset include:
- The surface water element on Native Companion Creek (near node 40) is not expected to experience any significant changes in annual flow volume, as all predictions at the 5th, 50th and 95th percentile are below the 1% threshold. However, the modelled increase in zero-flow days is more variable across the range of predictions. At the 5th and 50th percentiles the modelled increase in number of zero-flow days is less than 15 days. However, an increase of over 150 zero-flow days is modelled at node 40 for the 95th percentile.
- The hydrological changes are greater for the other two element locations (near nodes 44 and 53 on the Belyando River) that comprise this surface water asset. Overall, the reductions in annual flow remain relatively low, only just exceeding 1% at the median result for node 44 (and up to 1.4% at the 95th percentile). Zero-flow days are also expected to increase at both sites, with similar median results suggesting an increase of greater than 50 days per year of zero-flow conditions. Very large increases of similar magnitude (around 260 days) occur at the 95th percentile in both cases.
Data: Bioregional Assessment Programme (Dataset 1, Dataset 3, Dataset 8)
3.5.3.3 Groundwater economic assets
3.5.3.3.1 Potentially impacted groundwater economic assets
The Clematis Group aquifer is the main hydrogeological unit managed under the 2006 GAB water plan that occurs near the central-eastern margin of the Galilee subregion, in the area of the proposed coal mining developments modelled for this BA. Using a similar approach to that which was used to create the groundwater component of the zone of potential hydrological change (Section 3.3), the area of the Clematis Group with greater than 0.2 m of drawdown at the 95th percentile of all modelled predictions was used to identify relevant water-dependent assets that may potentially be impacted due to additional coal resource development. The results of this analysis are presented in Figure 79, showing the area of predicted drawdown >0.2 m in the Clematis Group aquifer at the 5th, 50th and 95th percentile of all modelling results. Notably, the areal extent of the Clematis Group aquifer that is potentially impacted by drawdown is greatest at the 95th percentile. Additionally, it is only at the 95th percentile that any areas are predicted to experience more than 2 m of drawdown in the Clematis Group, and this occurs only in a relatively isolated area near to the two nearest mines in the northern cluster (China Stone and Carmichael).
As shown in Figure 79, the Clematis Group aquifer occurs only to the west of all the modelled coal mines in the CRDP (i.e. it does not exist directly in the areas targeted for mining), although it occurs much nearer to the cluster of northern mines than to those mines in the south. There is also some degree of overlap between this Clematis drawdown zone and the zone of potential hydrological change, even though the latter zone is not directly relevant to assessing impacts within the confined Clematis groundwater system.
Spatial overlay analysis using a geographic information system (GIS) approach indicates that there are three groundwater economic assets associated with the Clematis Group aquifer that are potentially affected by drawdown due to additional coal resource development in the Galilee subregion (Bioregional Assessment Programme, 2017). These are the:
- basic water right in Barcaldine East 4 Groundwater Management Unit (BA asset identification number 2217)
- basic water right in Barcaldine North 3 Groundwater Management Unit (BA asset identification number 2220)
- water access right in Barcaldine North 3 Groundwater Management Unit (BA asset identification number 2276).
The numbers of individual elements (i.e. different bores) that will potentially experience drawdown within the range of 0.2 to 2 m at the 5th, 50th and 95th percentile for each of these three economic assets are shown in Table 45. In all cases, the total number of bores potentially affected by drawdown in the Clematis Group aquifer is less than the entire total number of bores in the assessment extent for each groundwater management unit. In addition, there are no asset-related bores (elements) that are expected to experience greater than 2 m of drawdown, even at the 95th percentile of all model results.
Data: Bioregional Assessment Programme (Dataset 1, Dataset 3, Dataset 8)
Table 45 Impacts to groundwater-dependent economic assets sourced from the Clematis Group aquifer due to additional coal resource development in the Galilee subregion
There is only one water access right in the Barcaldine North 3 Groundwater Management Unit that occurs within the area of predicted Clematis drawdown >0.2 m.
Data: Bioregional Assessment Programme (Dataset 6, Dataset 8)
In addition to the three economic assets that each have a specified groundwater management unit under the Water Plan (Great Artesian Basin) 2006, there are a further two groundwater-dependent economic assets that are potentially impacted, but not specifically assigned to GAB groundwater management units (Figure 78 and Figure 79). In the water-dependent asset register for the Galilee subregion (Bioregional Assessment Programme, 2017) these are identified as:
- water access right in Eme[2] Not Assigned Management Subgroup (Groundwater) (BA asset identification number 2287)
- basic right in Eme Not Assigned Management Subgroup (Groundwater) (BA asset identification number 2241).
There are two likely reasons why these assets are not assigned to specific groundwater management units. Firstly, the bores that comprise these assets may only occur within the area of the Burdekin Basin Water Plan area, which is mainly concerned with management of the surface water resources and generally does not assign bores to specific management subgroups. The other possible reason relates to any bores that are part of the GAB management area, but which access groundwater from an aquifer which is not a specified part of a groundwater management unit. For example, the Dunda beds and Rewan Group are not specified aquifers managed under the Barcaldine North Groundwater Management Area.
Within the zone of potential hydrological change, the unassigned water access right (BA asset identification number 2287) comprises fifteen individual bores that occur in three main clusters:
- seven bores near the township of Alpha, most of which are part of Alpha’s town water supply system – information available from the Queensland bore database indicates that these are relatively shallow bores (around 35 to 50 m deep) that most likely source water from the Quaternary alluvium and Cenozoic sediment aquifer associated with Alpha Creek
- four bores near the township of Jericho, most of which are part of Jericho’s town water supply system – information available from the Queensland bore database indicates that these are relatively deep bores (e.g. from 87 to 123 m deep) that likely source water from the confined aquifer system of the Clematis Group
- four irrigation bores near the southern end of the proposed Carmichael Coal Mine – the source aquifer of these bores is generally not specified in the Queensland bore database, although the bores are commonly greater than 50 m deep (some over 100 m deep), which suggests that they may access groundwater from a deeper confined aquifer system, such as the Dunda beds in the upper part of the Rewan Group.
As noted above, as this asset is not specifically assigned to any groundwater management unit there is some variability in the interpreted source aquifer. Thus, to better understand the potential impacts due to additional coal resource development on this asset, it is necessary to assess drawdown impacts separately for the three geographically different bore clusters.
Companion product 2.6.2 for the Galilee subregion (Peeters et al., 2018) noted that the hydrogeological conceptualisation that underpins the groundwater drawdown predictions from the AEM for the Galilee subregion is not appropriate for assessing potential impacts on the Alpha town water supply bores. This is mainly due to the poor understanding and characterisation of the hydrogeological properties of the deeper sequence of the Galilee Basin strata, particularly the basal Joe Joe Group. Although the town water supply bores at Alpha extract groundwater from alluvial aquifers associated with Alpha Creek, existing data from deeper bores in the area shows that these shallow Quaternary and Cenozoic sediments sit directly atop the rocks of the Joe Joe Group. Thus, the alluvial aquifer at Alpha is not connected to the alluvium and sediments that overlie the upper Permian coal measures for which drawdown is simulated in the AEM. Consequently, for drawdown impacts to propagate from the mines to the bores around Alpha, the drawdown in the upper Permian coal measures must first overcome the hydraulic resistance of the lower Permian units that separate the coal seams from the Joe Joe Group. Secondly, the hydraulic resistance between the alluvial deposits at Alpha and the Joe Joe Group also needs to be overcome. During development of the AEM for the Galilee subregion, research by the Assessment team indicated that scant information exists on the hydrogeological characteristics and groundwater flow systems of the Joe Joe Group, especially how this unit may contribute to (or impede) regional groundwater flow. Thus, the lack of understanding about groundwater systems and properties of the Joe Joe Group means that the conceptualisation used in the AEM is not suitable for assessing groundwater impacts due to additional coal resource development at the Alpha town water supply (including those bores that are part of this unassigned water access right). Further work using appropriate local-scale data is required to predict potential impacts on the Alpha town water supply bores due to the additional coal resource development.
The AEM for the Galilee subregion also does not explicitly simulate drawdown in the Dunda beds, the upper part of the predominantly low permeability Rewan Group (an aquitard). Thus, for the bores interpreted to extract water from the Dunda beds, it is only possible to assess drawdown impacts via a proxy unit (i.e. one that is specifically modelled in the AEM). In areas where the Clematis Group occurs, this aquifer could be used to estimate drawdown (although it may under predict the amount of drawdown). In other areas, the drawdown in the alluvial aquifer may be a suitable alternative proxy. In most cases, the drawdown estimates for the upper Permian coal measures are expected to substantially over predict drawdown impacts, as the impedance effect of the low permeability Rewan Group would not be adequately accounted for.
The caveats discussed in the preceding paragraphs indicate that potential drawdown impacts can be assessed for two of the three geographic areas where bores that belong to the unassigned water access right occur. In particular, it is possible to assess drawdown for the four bores that occur near Jericho, as well as the four bores near the site of the proposed Carmichael Coal Mine. The results of this analysis are shown in Table 46 (also see Figure 78). Drawdown at the 50th and 95th percentile exceed 0.2 m for all four bores near Jericho (although not at the 5th percentile), with the maximum predicted drawdown at the 95th percentile <0.6 m. There are two bores expected to experience greater than 2 m of drawdown near the southern boundary of the Carmichael mining lease, using the alluvial drawdown as a potential proxy indicator.
Table 46 Impacts to the water access right economic asset in the unassigned management group
As drawdown predictions for the Dunda beds and Rewan Group are not specifically modelled in the analytic element model for the Galilee subregion, the data for the southern Carmichael bores in this water access right are tabulated from the drawdown data for the Cenozoic aquifer, which is used here as a proxy indicator of drawdown impact.
The unassigned basic water right asset (BA asset identification number 2241) consists of seven individual bores, all of which are within the zone of potential hydrological change for the Galilee subregion (Figure 78). Only one of these bores also overlaps with the Clematis Group drawdown zone, occurring near the eastern-most edge of this unit’s modelled spatial extent (Figure 79), near the boundary of the zone of potential hydrological change. Even though this bore occurs within the Barcaldine North Groundwater Management Area, the source aquifer is specified (in the Queensland bore database) as the Dunda beds, which is the upper and more permeable part of the Rewan Group. As the Dunda beds are not a designated aquifer managed as part of the Barcaldine North Groundwater Management Area, this bore is not assigned to a specific management unit. The modelled drawdown in the overlying Clematis Group aquifer at this bore is 0.45 m at the 50th percentile, and covers the 5th to 95th percentile range from 0.18 to 0.80 m.
The other six bores in this unassigned basic water right will be variably impacted due to additional coal resource development (assuming they source groundwater from the upper aquifer). As shown in Figure 78, one bore occurs within the proposed southern mining area at the Carmichael Coal Mine, and hence direct impacts to this bore are highly likely to occur. Another bore near the southern boundary of the Carmichael mining lease lies within the 2 to 5 m drawdown zone (95th percentile) in the Quaternary alluvium and Cenozoic aquifer. However, all other bores in this asset occur much further away from the mine leases near the very margin of the zone of potential hydrological change, and predicted impacts at the 95th percentile for these bores just exceed 0.2 m for the upper aquifer (Figure 78).
3.5.3.3.2 Assessing impacts to groundwater economic assets
Provisions in Queensland’s Water Act 2000 help to manage the impacts that resource operations, such as coal mining and CSG extraction, may have on existing access to groundwater, for example, from an authorised water supply bore. The management framework specifies bore trigger thresholds (i.e. the amount of water level decline predicted for an aquifer as a result of the resource extraction) for different types of aquifers, with a:
- 5 m decline in groundwater level specified as the threshold for consolidated aquifers, such as sandstone aquifers
- 2 m decline in groundwater level specified as the threshold for unconsolidated aquifers, such as shallow alluvial aquifers.
Resource tenure holders (e.g. coal mining proponents) are generally required to determine the spatial extent of both the immediately affected area and the long-term affected area related to groundwater drawdown impacts caused by their activities. The immediately affected area encompasses areas around the resource operation where water levels in an aquifer are predicted to decline by more than the bore trigger threshold within 3 years of operation. In contrast, the long-term affected area covers the area where water level decline is predicted to exceed the trigger threshold at any future time (beyond 3 years) due to resource extraction.
For water bores that are predicted to be affected by drawdown in excess of the relevant threshold value, then a more detailed bore assessment may be required (particularly for bores within an immediately affected area). In cases where this type of assessment concludes that a bore’s capacity may be impaired by the resource development, then a ‘make good’ agreement may need to be negotiated between the tenure holder and the bore owner. This agreement seeks to ‘make good’ the impact caused by the resource extraction activity and is recognised as a legally binding document. Further information about the process for determining if make good arrangements are required, including the recommended approach for undertaking bore assessments, is available from DEHP (2017).
Under the relevant aquifer interference thresholds specified in Queensland, the potential impacts to the five groundwater-dependent economic assets potentially affected due to additional coal resource development can be evaluated as part of this BA. This analysis indicates that none of the groundwater-dependent economic assets sourced from the Clematis Group aquifer are predicted to experience a greater than 2 m drawdown impact, even for modelling results at the 95th percentile (Table 44). As the Clematis Group is a consolidated rock aquifer, the relevant bore trigger threshold under Queensland legislation is 5 m of drawdown. Consequently, none of the economic assets associated with the Barcaldine North and Barcaldine East groundwater management areas are expected to be impacted at a level that would trigger the need for make good provisions to be negotiated.
The town water supply bores for Jericho are part of an unassigned water access right (BA asset identification number 2287) that is classed as an economic asset for this BA. These bores are also interpreted to be sourced from the Clematis Group aquifer, in an area where the maximum predicted drawdown is less than 0.6 m at the 95th percentile of all modelling results (Table 46). This also suggests that any groundwater impacts at the Jericho town water supply due to additional coal resource development are unlikely to exceed specified bore trigger thresholds.
The town water supply bores at Alpha are also included as part of the unassigned water access right that occurs within the zone of potential hydrological change. However, as explained previously in this section, the outputs of the groundwater modelling for this BA were not able to accurately predict water level changes for these bores. Consequently, it is not possible to evaluate the potential for groundwater bore impacts to adversely affect the Alpha town water supply, flagging the need for further local-scale hydrogeological assessment in order to develop an appropriate management response to any potential impacts due to additional coal resource development.
3.5.3.4 Potentially impacted bores not in the water-dependent asset register
There are five groundwater-dependent economic assets potentially impacted due to additional coal resource development in the Galilee subregion. These assets consist of a variable number of bores grouped to the level of the relevant groundwater management unit (or unassigned group); with each bore representing an individual element of the asset. However, there are also a number of groundwater bores within and close to the zone of potential hydrological change that are registered in the Queensland groundwater bore database, but which are not included in the BA water-dependent asset register. Consequently, this section presents a brief analysis of potential impacts to bores that are not included as elements in the BA water-dependent asset register. This analysis is limited to those bores that are interpreted to source groundwater from the three aquifer systems that are modelled for this BA, namely the Quaternary alluvium and Cenozoic sediments (layer 1 in the AEM), Clematis Group (layer 3 in the AEM) and the upper Permian coal measures (such as the Betts Creek beds), which are represented as model layer 5 in the AEM. Some re-analysis of newly available data from various sources (such as publicly available coal company data) was done by the Assessment team to update the source aquifer information for some bores within the Queensland database, thereby allowing a more detailed assessment of a greater number of bores for this BA.
3.5.3.4.1 Bores sourced from Quaternary alluvium and Cenozoic sediments
The distribution of non-asset bores within the zone of potential hydrological change for the Galilee subregion that are interpreted to source groundwater from the relatively shallow (near-surface) alluvium and sediment aquifer is shown in Figure 80. These bores are included in the Queensland bore database but are not formally recognised as elements of an economic asset within the BA water-dependent asset register. There are approximately 105 such bores that access groundwater from the uppermost unconsolidated sediment aquifer within the zone, and most of these occur within the Burdekin Basin Water Plan area (i.e. they are not part of the GAB water plan). The Cenozoic-sourced bores are clustered in several locations, such as around the township of Alpha in the south, at a site about 50 km downstream of Alpha on Native Companion Creek and in an area around the Carmichael River. Cross-checking these bores against information contained in various SEIS documents (and, where possible, confirming the status of this information as of late 2017 with the coal mine proponents) for six of the proposed coal mines in the central-eastern Galilee Basin indicates that about 26 of these bores have been installed as part of pre-development groundwater monitoring networks around the proposed coal mines (company bores shown in Figure 80 are depicted by a black outline around the bore, and most of these occur within or close to the mine exclusion zone). As these monitoring bores are owned by the mining proponents and are not used to extract groundwater for an economic benefit, they have been excluded from any further analysis of potential impact in this BA.
Most of the remaining 79 non-asset bores in the zone that extract groundwater from Quaternary alluvium or Cenozoic sediments have probably been drilled for stock and domestic supplies. According to the status information about these bores in the Queensland bore database six of the bores are recognised as being ‘abandoned and destroyed’, and consequently these six bores are also excluded from this analysis on the basis that they are no longer useable. A further 24 bores are classed as being ‘abandoned and useable’ (and hence these are retained for analysis purposes as the bore may possibly be reused at some point in the future).
Using GIS-overlay analysis it is possible to assess drawdown impacts to the 73 non-asset bores (included in this analysis) that are interpreted to source groundwater from the alluvium or other sediments aquifer (Table 47). Of the total number, three bores directly coincide with areas where coal mining development is planned to occur in future (i.e. the bore location overlaps with the spatial extent of planned open-cut or underground mine workings). In these cases, the bore is highly likely to be directly impacted (e.g. excavated) at some point in future as mining progresses, and hence no drawdown estimates are provided for these bores. As shown in Figure 80, there are also many bores that occur within the zone of potential hydrological change that do not have any reliable stratigraphic information associated with them. As the source aquifer for such bores is unknown, it is not possible to determine if these bores will be affected by additional coal resource development (apart from those that overlap with the extent of mining areas).
Data: Bioregional Assessment Programme (Dataset 3, Dataset 8, Dataset 13, Dataset 14)
The Queensland bore trigger threshold for impacts to unconsolidated aquifers like the Cenozoic alluvium is 2 m of drawdown. The modelled median result where drawdown in the alluvial aquifer exceeds 2 m is estimated to impact 7 bores, and ranges from as low as 2 to as high as 13 bores (Table 47) across the range of modelling results (i.e. from 5th to 95th percentile). These results indicate that between 2 and 13 non-asset bores in the Cenozoic alluvial aquifer may require further assessment using more local-scale information, in order to determine if make good provisions may apply due to the additional coal resource development.
Table 47 Number of non-asset bores sourced from the Quaternary alluvium and Clematis Group aquifers that are potentially impacted due to additional coal resource development
A number of bores that have no stratigraphic information available in the Queensland groundwater bore database are not included in this table, even if they occur within areas of proposed coal mine development.
Data: Bioregional Assessment Programme (Dataset 8, Dataset 13, Dataset 14)
3.5.3.4.2 Bores sourced from the Clematis Group
The Clematis Group aquifer is one of the main groundwater sources managed under the Barcaldine North and Barcaldine East groundwater management areas. The potential impacts of additional coal resource development to these groundwater-dependent economic assets were previously presented in Section 3.5.3.3.1. However, a further 41 bores in the Queensland bore database are identified as being sourced from the Clematis Group, although these were not assigned to a particular management unit, and hence were not included as part of the BA economic asset analysis previously presented. Of these 41 bores, nine are excluded from this analysis as they are bores that are part of company-owned monitoring networks for some of the mines (this approach was also used for the Cenozoic bores previously discussed). There is also another bore excluded from the analysis as it is listed as ‘abandoned and destroyed’ in the Queensland bore database.
Excluding the company-owned monitoring bores and the bore that is no longer useable means that there are 31 non-asset bores that source water from the Clematis Group that may potentially be impacted due to additional coal resource development. The distribution of these bores is shown in Figure 81, and results of more detailed analysis are tabulated in Table 47. Similar to the results of the asset analysis, most of the non-asset bores that tap the Clematis Group aquifer are predicted to experience between 0.2 and 2 m of drawdown. At the 95th percentile of modelled results, there are 31 bores that occur within this drawdown range. The maximum modelled drawdown is about 1 m at the 95th percentile, which is predicted for a Clematis-sourced bore near the northern mining cluster. There are no non-asset bores with a Clematis Group source that exceed Queensland’s 5 m bore trigger threshold for make good provisions for consolidated rock aquifers.
3.5.3.4.3 Bores sourced from the upper Permian coal measures
The last group of non-asset bores that can be assessed for potential impacts using this GIS-overlay approach are those that have an upper Permian coal measures source aquifer, such as the Betts Creek beds or Colinlea Sandstone (Figure 81). The upper Permian coal measures are the main coal resource target in the Galilee Basin and will need to be dewatered in areas of mining operations to allow for the safe and efficient extraction of the coal resource. As a consequence of dewatering this geological unit, very substantial drawdown predictions are modelled in this BA using the AEM. However, it is important to recall (as explained in Section 3.2.3.1) that the AEM has used a simplified conceptualisation of the upper Permian coal measures and has modelled the entire sequence as a single hydrostratigraphic layer of constant thickness and extent. In reality though, this unit comprises a range of lithological compositions and stratigraphic/structural associations that include variably thick layers of coal as well as a variety of interburden types including sandstone, siltstone and mudstone (all with variable hydraulic parameters). While the simplified hydrostratigraphy implemented in the AEM is considered appropriate for the regional-scale analysis of the BA for the Galilee subregion, this approach may potentially lead to over or under estimated drawdown predictions at a local scale.
Analysis of the available data from the Queensland bore database, combined with some updated interpretations resulting from this BA, has shown that there are approximately 168 bores within the zone of potential hydrological change that are interpreted to source water from the upper Permian coal-bearing units. However, analysis of available information from SEIS documents and company feedback indicates that about 131 of these bores have been installed as part of pre-development company-owned groundwater monitoring networks. As shown in Figure 81 (with coal company bores shown with a black outline), 74% of the company bores occur in areas of the mine exclusion zone which indicates that these bores would be directly impacted as mining progressed in the future.
Of the 37 non-company bores that extract groundwater from the upper Permian coal measures, three are listed in the Queensland bore database as being ‘abandoned and destroyed’. Due to their status these three bores have been excluded from further analysis in this BA. Most of the remaining 34 bores screened in the upper Permian coal measures that are potentially impacted due to additional coal resource development are likely to be pastoral bores that have previously been installed for stock and domestic water supplies. Importantly though, this geological unit is not actively managed as a groundwater source under the auspices of the GAB Water Plan, or the Burdekin Basin Water Plan (although it will be included under the new GABORA Water Plan).
Outside of the actual mine footprint areas (where drawdown predictions using the AEM may not be reliable, and the bores are highly likely to be directly impacted by development activity anyway), very substantial drawdowns are predicted for most bores that tap the upper Permian coal measures. For example, the median prediction results indicate that 23 bores will experience drawdowns of greater than 100 m. This number is as low as 21 bores at the 5th percentile, and rises to 30 bores at the 95th percentile. Relatively few bores are predicted to experience less than 20 m of drawdown in the upper Permian coal measures, varying from 24% at the 5th percentile to 12% at the 50th percentile (and none at the 95th percentile).
The results of this analysis clearly indicate that nearly every groundwater bore interpreted to source water from the upper Permian coal measures is likely to be substantially impacted due to additional coal resource development. Most of these bores that are owned and operated by landholders for stock and domestic purposes (i.e. that are not also the resource tenure holder or development proponent) may be eligible for more detailed bore assessments as a prelude to negotiated make good agreements, as applicable under existing Queensland water legislation and policy.
Figure 81 also highlights a number of other non-asset bores with different source aquifers that occur either within the zone of potential hydrological change, or its Clematis Group aquifer corollary. For these cases, the groundwater modelling undertaken for this BA is not able to directly assess aquifer drawdowns, as these hydrogeological units were not explicitly included in the conceptualisation and modelling. However, as these units are stratigraphically adjacent to the modelled layers, it is possible to qualitatively evaluate drawdowns based on the most suitable proxy layer. This can provide an approximation of potential drawdown impacts, even though the actual drawdown amount will likely be either underestimated or overestimated. For example, the Moolayember Formation overlies the Clematis Group, and so the Clematis Group aquifer could be used to provide an approximation of drawdown magnitude, even though any amount of drawdown in the Moolayember Formation would always be less than the predicted response in the Clematis Group at any particular point.
There are also a number of other bores for which stratigraphic information is not available in the Queensland groundwater bore database (e.g. these are shown as grey bores in Figure 80). For these bores, it is not possible to further assess potential drawdown impacts in this BA, due to the absence of relevant information about the source aquifer.
Data: Bioregional Assessment Programme (Dataset 3, Dataset 8, Dataset 14)
