2.7.6.1.1 Overview
The ‘Non-floodplain, terrestrial GDE’ landscape group contains two landscape classes: ‘Non-floodplain, terrestrial GDE’, which occupies an area of 5.5 km2; and ‘Non-floodplain, terrestrial GDE, remnant vegetation’, which occupies an area of about 1184 km2 (Figure 32). The classification of these two landscape classes does not specify the source of groundwater (see Section 2.3.3 of companion product 2.3 for the Galilee subregion (Evans et al., 2018b)). These two landscape classes are examples of the third type of GDE defined in the typology of Richardson et al. (2011). These ecosystems are terrestrial GDEs that rely on the subsurface expression of groundwater on a permanent or intermittent basis to maintain growth or avoid water stress and adverse impacts on condition (Eamus et al., 2006; Richardson et al., 2011). In the landscape classification adopted here, these would be broadly defined as groundwater-dependent vegetation assemblages that are not on floodplains and are not associated with palustrine, lacustrine or riparian wetlands.
The Galilee subregion occurs in an area where the annual rainfall is low and unpredictable. Climatically, areas occupied by the ‘Non-floodplain, terrestrial GDE’ landscape group are water-limited. Annual rainfall is low at approximately 300 mm/year and evaporation is high at greater than 2000 mm/year (companion product 1.1 for the Galilee subregion (Evans et al., 2014)). Low and sporadic rainfall coupled with high evaporative demand suggest that groundwater may be a more reliable source of water for this landscape group than surface water (Eamus et al., 2006). Much of the vegetation, in particular trees, relies on accessing groundwater from shallow unconfined aquifers. Groundwater is needed for trees to persist in areas where evapotranspiration exceeds rainfall. The presence of a shallow watertable enables the roots of trees to obtain a relatively consistent supply of water irrespective of aboveground conditions (Eamus et al., 2015).
A high level conceptual model for unconfined, permeable rock aquifers is relevant to this landscape group (Figure 33). In the model, groundwater stored in one or more unconfined permeable rock aquifers is transmitted through intergranular pore spaces, fractures and/or weathered zones in the rock strata (DSITI, 2015). Near-surface discharge can occur where there is a change in geology (e.g. at a geological contact between a sandstone layer and an underlying shale layer) or at footslopes at the base of hills or ranges (Figure 33). Here, unconfined aquifers can discharge groundwater to terrestrial vegetation. Groundwater may then move laterally downslope to within reach of the capillary zone of the terrestrial vegetation.
Sediments that comprise Cenozoic to Quaternary loamy and sandy plains readily store and transmit groundwater in shallow, local aquifers. Here, terrestrial vegetation may source groundwater up-gradient of the contact between the plains and elevated areas such as mesas and raised ironstone outcrops. Terrestrial GDEs in these areas are likely to support regional ecosystems (REs) dominated by Corymbia spp. (DSITI, 2015). Medium- to coarse-grained sedimentary rocks may store and transmit groundwater through fractures, residual porosity and weathered zones. These local, bedrock aquifers occur in rock that is otherwise of relatively low porosity (DSITI, 2015). Here, terrestrial vegetation may source groundwater where it discharges along footslopes within sandstone ranges. A rarer type of permeable rock aquifer occurs in basalts which store and transmit groundwater through vesicles, fractures and weathered zones. Terrestrial vegetation that occurs in areas of basaltic rock may source groundwater at the edge of basalt plains and hills.
GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 1)
Figure 33 Conceptual model of a permeable rock aquifer
GDE = groundwater-dependent ecosystem
Source: adapted from Queensland Department of Science, Information Technology and Innovation (Dataset 2), © The State of Queensland (Department of Science, Information Technology and Innovation) 2015
2.7.6.1.2 Hydrological regimes and connectivity
Understanding the connectivity of groundwater in the zone of potential hydrological change is challenging because the Galilee subregion contains a series of stacked groundwater systems. These are described in detail in companion product 2.1-2.2 (Evans et al., 2018a) and Section 2.3.2 of companion product 2.3 (Evans et al., 2018b) for the Galilee subregion, and are summarised below to provide context. The paragraph below focuses on the Galilee Basin groundwater system in which the Rewan Group and Clematis Group occur. These are the most likely sources of groundwater for the ‘Non-floodplain, terrestrial GDE’ landscape group within the zone. Further information about the variability of the depth to the watertable in the zone (i.e. the standing water level observed in groundwater bores) is provided in Section 3.4.1 of companion product 3-4 for the Galilee subregion (Lewis et al., 2018).
Potential sources of groundwater for vegetation that forms the ‘Non-floodplain, terrestrial GDE’ landscape group are:
- shallow perched aquifers in weathered Cenozoic sediments. Groundwater may come near or discharge to the surface on footslopes or where percolating groundwater becomes perched upon a relatively impermeable layer such as clay or shale, the result of which redirects groundwater flow to near surface
- groundwater flow in unconfined parts of aquifers coming within the capillary zone of plants or discharging near surface. This could occur in any weathered sedimentary rock unit which is dominated by sandstone (e.g. Clematis Group, Dunda beds (the upper and more permeable part of the Rewan Group), Colinlea Sandstone, and sandstone beds in the Joe Joe Group).
Some shallow groundwater flow could be part of a regional groundwater system. The GDEs that are connected to the regional groundwater systems within the zone of potential hydrological change would be impacted by changes in groundwater (for example, from drawdown or reductions in recharge) across a broad area. However, not all GDEs are connected to the regional watertable. Those that aren’t are unlikely to be impacted by broader-scale changes.
2.7.6.1.3 Ecological processes
The water requirements and the degree of groundwater dependency of the vegetation that is in the ‘Non-floodplain, terrestrial GDE’ landscape group will depend on a number of factors including:
- age and rooting distribution of plants, and how this enables access to the watertable
- depth to the watertable and spatial and temporal (seasonal) variation in the watertable level
- groundwater quality.
Vegetation within the ‘Non-floodplain, terrestrial GDE’ landscape group will typically use deep roots to access groundwater in the capillary zone above the watertable via capillary action or hydraulic lift. A baseline assumption with the physiology of Australian plants is that they can access groundwater to a depth of about 10 m (D Eamus, 2016, pers. comm.). This value is supported by research that found the mean maximum rooting depth across 11 species of sclerophyllous trees to be 12.6 m ± 3.4 m standard error (Canadell et al., 1996). However, some tree species have roots that can access water at greater depths. Eucalyptus marginata roots have been reported at depths of 40 m by Dell et al. (1983). This work found that only fine roots (less than 1 mm diameter) were able to penetrate the clay matrix of the soil and reach these depths.
The dependency of vegetation on groundwater may vary seasonally. It is generally assumed that water dependency will change with rainfall and be greatest at times of seasonal rainfall deficit. There is empirical support for this view. For example, in eucalypt woodland along the Condamine River, southern Queensland, the frequency of deep subsurface water use was greatest in the late dry season (Gow et al., 2016).
The depth to the watertable is an important factor in determining the volume of water discharged through GDEs. In the zone of potential hydrological change, the depth to standing water in the 98 bores in the ‘Non-floodplain, terrestrial GDE’ landscape group averaged 37.3 m below surface. The range varied widely however, from a maximum depth of 156.7 m to a minimum depth of 0.3 m below surface.
Currently, there is little published information on either the amount of water used by GDEs or the physiology of GDEs. Similarly, there is a knowledge gap in terms of information on root depth of vegetation within GDEs and on responses to changes in depth-to-groundwater (Eamus et al., 2015). This information, if it were available, would be invaluable in assessing the impacts of groundwater drawdown on GDEs.
2.7.6.1.4 Vegetation
The landscape classes within the zone of potential hydrological change span two of the Interim Biogeographic Regionalisation for Australia (IBRA) regions: Desert Uplands and Brigalow Belt. The Desert Uplands are characterised by upland landforms dominated by sandstone ranges and sandplains. In contrast, the Brigalow Belt is characterised by undulating ranges to alluvial plains (Bastin et al., 2008). Underlying geology and land zone contribute to a complex mosaic of vegetation communities, including eucalypt and acacia woodlands, shrublands and grasslands.
Within the ‘Non-floodplain, terrestrial GDE’ landscape group there are 90 regional ecosystems (REs). There is considerable uncertainty related to the water regime required to support many of these REs. However, the nature of the dependency on groundwater is likely to vary among and within vegetation communities, as a function of groundwater availability, depth and quality (companion product 2.1-2.2 for the Galilee subregion (Evans et al., 2018a)).
The distribution of the most widespread vegetation assemblages, represented by REs, within the ‘Non-floodplain, terrestrial GDE’ landscape group is shown in Figure 34. The majority of these REs have Eucalyptus and/or Corymbia species as dominant/co-dominant in the upper storey. A smaller number of REs have Acacia and/or Melaleuca species as dominant/co-dominant. The 10 most widespread REs in the ‘Non-floodplain, terrestrial GDE’ landscape group in order of decreasing area (expressed as a percentage of the zone) are:
- RE 10.5.5 ‘Eucalyptus melanophloia woodland to open woodland on sand plains’ (3.68%)
- RE 10.7.2 ‘Eucalyptus persistens or Corymbia dallachiana low open woodland or Triodia pungens hummock grassland on ferricrete above scarps’ (1.00%)
- RE 10.7.11 ‘Eucalyptus melanophloia low open woodland on ferricrete’ (0.74%)
- RE 10.7.7 ‘Melaleuca spp. and/or Acacia leptostachya shrubland on ferricrete (eastern)’ (0.56%)
- RE 10.10.4 ‘Eucalyptus exilipes and/or Corymbia leichhardtii open woodland on sandstone ranges’ (0.39%)
- RE 10.7.3 ‘Acacia shirleyi woodland or A. catenulata low woodland at margins of plateaus’ (0.28%)
- RE 10.10.1 ‘Acacia shirleyi woodland or A. catenulata low open woodland on sandstone ranges’ (0.26%)
- RE 11.5.3 ‘Eucalyptus populnea +/- E. melanophloia +/- Corymbia clarksoniana woodland on Cainozoic sand plains and/or remnant surfaces’ (0.19%)
- RE 10.5.2 ‘Corymbia plena with or without C. dallachiana or C. terminalis open woodland on sand plains’ (0.11%)
- RE 10.7.12 ‘Eucalyptus drepanophylla or E. crebra open woodland on ferricrete’ (0.11%).
‘Brigalow (Acacia harpophylla dominant and co-dominant)’, which is listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) as an ‘Endangered’ ecological community, occurs within this landscape group. The ecological community is predicted to occur widely in the eastern half of the Galilee subregion zone of potential hydrological change (Department of the Environment and Energy, 2017a). The vegetation types that make up the brigalow ecological community mostly occur on acidic and salty clay soils. Within the zone these are mostly on deep cracking clay soils.
‘Weeping Myall Woodlands’, which is listed under the EPBC Act as an ‘Endangered’ ecological community, occurs within this landscape group. The ecological community is predicted to occur widely in the south-eastern part of the Galilee subregion zone of potential hydrological change (Department of the Environment and Energy, 2017b). It occurs on flat areas or shallow depressions on alluvial plains. Such areas are not associated with river channels and are rarely flooded. The soils are black, brown, red-brown or grey clay or clay loam (Commonwealth of Australia, 2009).
GDE = groundwater-dependent ecosystem
Data: Bioregional Assessment Programme (Dataset 1, Dataset 3)
2.7.6.1.5 Flora and fauna
The ‘Non-floodplain, terrestrial GDE’ landscape group provides potential habitat for a range of threatened animal species. These are detailed below.
The koala (Phascolarctos cinereus) potentially occurs within the ‘Non-floodplain, terrestrial GDE’ landscape group in the Galilee subregion zone of potential hydrological change. Koalas in Queensland are listed as ‘Vulnerable’ nationally (EPBC Act) and under Queensland’s Nature Conservation Act 1992 (Nature Conservation Act). Koalas in semi-arid environments, including within the zone, inhabit forest and woodland dominated by Eucalyptus species with important food and habitat trees including Eucalyptus camaldulensis, E. populnea, E. crebra, E. tereticornis, E. melanophloia, E. tessellaris and Melaleuca bracteata (Gordon et al., 1988; Ellis et al., 2002).
The ornamental snake (Denisonia maculata) occurs within the zone of potential hydrological change of the Galilee subregion and potentially occupies the ‘Non-floodplain, terrestrial GDE’ landscape group. The species is listed as ‘Vulnerable’ under both the EPBC Act and the Nature Conservation Act (Department of the Environment and Energy, 2017c). The ornamental snake is considered to be water-dependent as it feeds almost exclusively on frogs. It occurs in riparian vegetation along watercourses, on the margins of wetlands including lakes and swamps and in terrestrial vegetation that is likely to be groundwater-dependent. The latter category includes woodland and open woodland of coolibah (Eucalyptus coolabah), poplar box (E. populnea), brigalow (Acacia harpophylla), gidgee (A. cambagei) and blackwood (A. argyrodendron) (Department of the Environment and Energy, 2017c). The REs in which it has been found all have clay soils.
Dunmall’s snake (Furina dunmalli) potentially occurs within the zone and, if it does, it is likely to occupy the ‘Non-floodplain, terrestrial GDE’ landscape group. The species is listed as ‘Vulnerable’ under both the EPBC Act and the Nature Conservation Act (Department of the Environment and Energy, 2017d). In Queensland, the range of Dunmall’s snake is mostly within the Brigalow Belt region to the east of the zone. Dunmall’s snake occurs in terrestrial vegetation. The species seems unlikely to be water-dependent.
The yakka skink (Egernia rugosa) is a threatened lizard that occurs within the zone of potential hydrological change of the Galilee subregion. It is listed as ‘Vulnerable’ under both the EPBC Act and the Nature Conservation Act (Department of the Environment and Energy, 2017e). The species occurs in woodland and open forest dominated by a range of trees including Acacia, Eucalyptus, Casuarina and Callitris. Yakka skinks are burrowing animals that occur in colonies or small groups (Chapple, 2003). Within the zone the yakka skink is likely to occupy sand plains, clay and clay loam plains, sandstone rises and minor pediments and vegetation fringing watercourses and stream channels and on alluvial plains. Therefore, it is expected to occur in the ‘Non-floodplain, terrestrial GDE’ landscape group. The water dependency of the species is poorly understood.
The southern subspecies of the squatter pigeon (Geophaps scripta scripta) is listed as ‘Vulnerable’ under both the EPBC Act and the Nature Conservation Act (Department of the Environment and Energy, 2017f). It is a granivorous bird that occurs through much of the Galilee subregion zone of potential hydrological change. It was recorded during surveys as part of the environmental impact statements for five of the proposed major coal mine developments in the zone. From north to south these are China Stone, Carmichael, Kevin’s Corner, Alpha, and China First. The squatter pigeon (southern) forages and breeds in a range of open-forest, woodland and open-woodland vegetation types that have a grassy understory. It depends on surface water as it needs to drink on a daily basis and, as a consequence, foraging and nesting sites are located within 3 km of a water source. Water sources used by the species include rivers, lakes and artificial sources such as farm dams (Department of the Environment and Energy, 2017f). Therefore, the squatter pigeon is predicted to use water sources within the ‘Non-floodplain, terrestrial GDE’ landscape group.
The southern subspecies of the black-throated finch (Poephila cincta cincta) is classified as ‘Endangered’ nationally (EPBC Act) and in Queensland (Nature Conservation Act). It is a threatened species with a large potential distribution within and adjacent to the Galilee subregion zone of potential hydrological change (Vanderduys et al., 2016). The black-throated finch was located during surveys as part of environmental impact statements and subsequent surveys at the Carmichael (nine locations) and China Stone (eight locations) coal mine projects. The black-throated finch occupies grassy woodland within the zone. It is surface water dependent. The finch feeds mostly on the ground on a range of grass seeds. It occupies several vegetation assemblages within the ‘Floodplain, terrestrial GDE’ and ‘Non-floodplain, terrestrial GDE’ landscape groups. Important regional ecosystems for the black-throated finch in the zone are listed below (based on GHD, 2012; Vanderduys et al., 2016):
- RE 10.3.6 ‘Eucalyptus brownii woodland to open woodland on alluvial plains’
- RE 10.3.28 ‘Eucalyptus melanophloia or E. crebra woodland to open woodland on sandy alluvial fans’
- RE 10.5.1 ‘Eucalyptus similis and/or Corymbia brachycarpa and/or Corymbia setosa low open woodland on sand plains’
- RE 10.5.5 ‘Eucalyptus melanophloia woodland to open woodland on sand plains’. This is the dominant RE where the black-throated finch occurs on the Carmichael mine lease (GHD, 2012)
- RE 10.7.11 ‘Eucalyptus melanophloia low open woodland on ferricrete’.
The species also occurs in non-remnant vegetation (GHD, 2012).
